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Aircraft survivability

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Title:
Aircraft survivability
Place of Publication:
Arlington, VA
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Joint Aircraft Survivability Program Office (JASPO)
Publication Date:
Copyright Date:
1998
Frequency:
Three times a year
regular
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English

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Aeronautics -- Safety measures -- Periodicals -- United States ( lcsh )
Aeronautics -- Safety measures ( fast )
United States ( fast )
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Periodicals. ( fast )
newspaper ( marcgt )
serial ( sobekcm )
periodical ( marcgt )
Periodicals ( fast )

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Began with 1998.

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University of Florida
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University of Florida
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This item is a work of the U.S. federal government and not subject to copyright pursuant to 17 U.S.C. §105.
Resource Identifier:
656541464 ( OCLC )
ocn656541464
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TL553.5 ( lcc )

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Digital Military Collection

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Spring 1999

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Aircraft Survivability Spring 1999 2 Contents Lethal and Survivable Air Weapons Systems: Essential Today and Tomorro w 4 byV ADM W illiam J .F allon, USN Aircraft Survivability: A Balanced Susceptability Reduction Approach 6 b y Mr Rober tT. (Tom) W ebber Integrated Low Observables and Countermeasures 8 b y Mr Ron "Mutz" Mutzelbur g& Mr .T ony Grieco Pioneers of Survivability 10 Huber t HughDrak e Electronic Warfare and Low Observability T echnology to Defeat RF and IR Threats 12 b y Mr Dan Gobel The Survivable Rotorcraft 14 b y Mr David G Harding & Mr Stephen A.Brumle y Stealth As A Dependent Variable T o EW 18 b y Mr .P aul H.Ber ko witz NDIA Aircraft Fire and Explosion Information Exchange Meeting 21 b y Mr Ralph Lauzz e, Mr Chuck Pedriani & Mr Dale Atkinson The Synergy of Susceptibility Reduction and Signature Management: A Question of Energy 23 b y Mr Lar r y DeCosimo JTCG/AS Industry Advisors Receiv e Special Honors 25 by Mr.J o s e ph P.J o l l e y A ctive Core Exhaust Control Systems 26 b y Mr Clarence F Chenault & Dr Yvette S. W eber National MANPADS Workshop: A Vulnerability Perspectiv e 28 b y Mr .J oseph P .J olle y Calendar 31 Aircraft Survivability is published by the Joint Technical Coordinating Group on Aircraft Survivability (JTCG/AS). The J T CG/AS is chartered by the Joint Aeronautical Commanders Group. V i e w s and comments are welcome and m a y be addressed to the Editor at the f o l l o wing address. E d i t o r : Joseph P. Jolley J T CG/AS Central Office 1 2 13 Jefferson Davis Highway C r y stal Gateway #4, Suite 1103 Arlington, VA 22202 P H O N E : 70 3 6 07 3 5 09, ext. 14 D S N : 3 2 7 3 5 09, ext. 14 email: j o l l e y 2 @ t e c n e t 1 j c t e. j c s. m i l h t t p : / / j t c g j c t e. j c s. m i l : 9 101 Mailing list additions, deletions, and/or changes may be directed to: A F R L / V A V S / S U R V I A C, Building 45 Attention: Linda Ry a n 2 1 3 0 Eighth Street, Suite 1 W r i g h t P atterson AFB, OH 45433-7542 P H O N E : 9 3 7 2 5 5 4 8 4 0 D S N : 7 8 5 4 8 4 0 email: lry a n @ s u r v i a c f l i g h t w p a f b. a f m i l C r eative Dir e c t o r : Christina McNemar S U R V I A C Satellite Office 3 1 9 0 Fairview Park Drive Falls Church, VA 22 0 4 2 P H O N E : 70 3 2 8 9 5 4 6 4 email: m c n e m a r c h r i s t i n a @ b a h c o m G r aphic Artist: Ahnie Senft C o ver Design by Christina P. McNemar featuring Lockheeds F-117 Stealth Fighter.

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Editor s Notes Aircraft Survivability Spring 1999 3 LTC Charles Schwarz Wed like to welcome a member to the Central Office staff. Army LTC Charles Schwarz replaces LTC Paul McQuain as the Arm y s military representat i v e and the new Director. His recent assignments include tours at Headquarters Army Materiel Command as a Procurement Staff Officer for Engineer Mine-warfare Equipment and Non-system Training Devices; the Pentagon, in the Strategic Defense Initiative Organization now known as Ballistic Missile Defense Organization as a Program Integrator; and again at Headquarters Army Materiel Command in the Inspector Generals office. Professor Ball at the Naval Postgraduate School has published an article in the November-December 1998 issue of Naval Aviation News. The article is titled, "Designed to Survive". If you dont have the magazine, the article is on the w e b at, http://www h i s t o r y. n av y mil/nan/1998/1298/survive.pdf. Professor Ball also has a survivability education web site at, http://www a i r c r a f t s u r v i va b i l i t y .com. Mark your calendars for the annual Survivability Symposium sponsored by the National Defense Industrial Association (NDIA) which will be held 16-18 N o v e m b e r 1999 at the Naval Postgraduate School in Monterey, CA. The theme for this y e a r s event is, Aircraft Survivability 1999: Challenges For The New Millennium. The JTCG/AS is investigating the idea of developing a Spacecraft Surviv a b i l i t y d i s c i p l i n e Dr. Joel Williamsen of the University of Denver Research Institute (UDRI) and formerly with NASA, is working with the JTCG/AS and the AIAA S u r v i v ability Technical Committee to promote this objective. The concept is to extend the discipline of aircraft survivability into the regime of spacecraft design and operation, to protect spacecraft assets from undirected threats (meteoroid and orbital debris) and directed threats (kinetic energy, directed energy, nuclear, and other anti-satellite weapons). As part of the space survivability initiative, the JTCG/AS is in the preliminary stages of planning a workshop to explore the applicability of aircraft surviv a b i l ity methodologies and test data to the growing concern of spacecraft surviva b i l i t y Possible co-hosts could include USSPACECOM and AIAA. The tentative date is June 2000 and would be held at the USAF A c a d e m y, Colorado Springs, C O If you would like more information, Dr. Williamsen may be contacted at 30 3 8 71 4 5 02 or email jowillia@du.edu. Or, you may call the JTCG/AS Central O f f i c e More to come in upcoming issues of A i rc r aft Survivability. Since our last issue, the JTCG/AS co-hosted with the Missile and Space Intelligence Center (MSIC) a successful workshop titled, National MANP A D S Workshop: A Vulnerability P e r s p e c t i v e. The workshop was held in Huntsville, Alabama 15-17 December 1998. Over one hundred experts attended a technical interchange to assess if there is anything more the survivability community should or could be doing to make aircraft more survivable against the MANPADS threat. The next issue of the n e w sletter will focus on the theme of Aircraft Vulnerability against the M A N P ADS threat.

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Aircraft Survivability Spring 1999 4 1948. DoD topline spending and research, dev e l o p ment, test and evaluation (RDT&E) are down 34 percent and 26 percent, respectiv e l y since 1987. There is certainly room to debate the appropriate allocation of resources within the budget. But, there is no doubt that the amount of money in the DoD budget is sharply less than a decade agoand unlikely to significantly increase in the near future, absent a big change in the strategic landscape. In spite of these factors, we have been operating v e r y well, thanks to the procurement and readiness inv e s t ments of the early 1980s. Current replacement levels for equipment, how e ve r are clearly insufficient and readiness of our nonforward deployed forces is eroding. Ov e r the past 25 y e a r s the cost growth curve of new fighter and attack aircraft, measured in cost per pound, has been increasing steadily and is at about 7 percent, compared to 3-4 percent for various new ship and land equipment designs. 1 This steep and steady cost escalation is making it increasingly difficult to acquire replacement aircraft in the numbers required by the services. D i s c u s s i o n To ensure that our air forces are effective, surviv a b l e and affordable, we must plan for the future Consideration must be given to employing a combination of devices and techniques to enable us to successfully complete our missions. The use of electronic w a r fare (EW), low observable (LO) applications, and precision guided munitions (PGM) will aid in attaining this goal. For 60 y e a r s EW has been a factor in combat o p e r a t i o n s with a heavy inv o l v ement in tactical a v i a tion for the last 30 y e a r s The focus of the a v i o n i c s industry has been on the hardware of threat receiv e r s warning devices, jammers, deception devices, expendables; discussion about self-protect or strike support; pod or integrated, onboard and off-board techniques, and related tactics. LO applications are new e r in service for only 20 y e a r s and less mature. Primarily the purview of the airframe contractors, these applications have seen limited he air warfare dimension of our national military capability is indispensable today and a prime consideration in every strategy and contingency in the political-military arena. This emphasis is w a r r a n t ed because we enjoy a significant adv a n t a g e over potential adversaries in our ability to dominate airspace. Our ability to influence e v ents w o r l d w i d e to prevent actions detrimental to national interest, and to respond d e c i s i v ely hinges on speed and agility. Airlaunched weapons from tactical platforms p r o vide that ability and are high on the list of preferred military options. F o r w ard deploy e d and rapid response air forces working jointly and increasingly, in combined operations with our allies, provide the nation with a valuable and reusable capability. But to be c r e d i b l e these forces must be effective, surviva b l e and affordable. B a c k g ro u n d The collapse of the Soviet empire and end of the Cold War has resulted in a fundamental redefinition of the term "security." No longer is there a superpower military standoff in an essentially bipolar strategic setting, but complex, interdependent economic, political, milit a r y and population issues punctuated with a continuing series of regional conflicts and ethnic strife. Although U.S. combat forces have been reduced by some 35 percent over the past 9 y e a r s the operational tempo for our troops, manifested in forward presence, crisis r e s p o n s e and regional engagement operat i o n s is higher than during the Cold W a r A d d i t i o n a l l y the Department of Defense (DoD) allocation of gross domestic product (GDP) is only about 3 percent, down 50 percent since 1986 and at the lowest level since Lethal and Survivable Air Weapons Systems: Essential Today and T o m o r r o w by VADM William J. Fallon, USN T

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Aircraft Survivability Spring 1999 5 service to date having been reserved as "manned silv e r b u l l e t s ," in the form of F-117s and the newer B-2. But LO will be a major factor in aircraft survivability in new strike fighter designs and should be employed for all future tactical aircraft. The public domain has an interesting perception that equates LO to stealth; stealth to invisibility; invisibility to invulnerability; invulnerability to 100 percent surviva b i l i t y Of course, this is an inaccurate picture that has become a major factor in employment decision-making and produces high public expectation of success. EW is less glamorous and less well understood than stealth and generates much less public interest. Another very significant operational factor is the rapid ascent of PGMs to a position of ov e r w h e l m i n g preference for nearly every planning contingency t o d a y. The development and use of PGMs of v a r i o u s r a n g e s profiles, and capabilities are closely related to aircraft survivability factors and should be a design consideration. Expectations among airwing designers and aircrews h a ve become more reasonable regarding LO and EW a p p l i c a t i o n s Few in the business today regard any single device as guaranteeing full surviv a b i l i t y Most combat aircrews train to employ a combination of techniques to complete missions with high assurance of returning home. The Way Ahead To successfully incorporate LO and EW applications, we must first ensure that the task or mission is w e l l defined. This is straight forward for tactical air, i.e d e s t r o y the opponents aircraft before the opponent d e s t r o ys you and put weapons on ground targets to d e s t r o y them. The next issue is to enhance surviv a b i l i t y when completing these missions. The approach to accomplishing survivability should be coordinated, systemic analysis of mission execution from launch to r e c o v e r y This requires a "mental open architecture." F o r e x a m p l e we should be Looking at the big picture first to determine the o p p o n e n t s functional tasks, e.g., detection, acquisition, targeting Working the seams to delay or deny information Looking at the full spectrum of the mission with the philosophy that no single application is going to guarantee survival, but several w e l l integrated, mutually supporting, or complementary applications could do the job. Other factors, such as the ability to integrate intelligence feeds and combat identification data, would enhance the functionality and techniques of discreet EW equipment to boost s u r v i va b i l i t y Airframe layout, signature reduction, and EW techniques have been used to enhance surv i v ability but rarely coordinated optimally or well integrated from initial design concept into operational use. Instead, techniques have been presented singularly in the form of external p o d s internal boxes, or reprogrammable prog r a m s just to mention a few. There are in fact too many dysfunctional solutions. If DoD and industry agree to work closer together from the beginning, that relationship will be enhanced by the follo w i n g : Methods of modeling and simulation that have been vastly improv e d Techniques that enable products to be manufactured at significant cost and time sa v i n g s Industry groups exchanging information in a more efficient manner as a result of the existence of fewer aerospace companies. Along the way there are challenges to ov e r c o m e : Reliability and maintainability of avionics equipment and coapplications Issues with antennas, apertures, and t r a n s m i s s i v i t y E x c e s s i v e time in dev e l o p m e n t Cost of applying the solutions. When addressing theses challenges, all types of aircraft should be considered as well as the ability to upgrade without wholesale component replacement. For the future, unmanned aerial vehicles (UAV) could redefine surviv a b i l c o n t i n ued on page 9

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(CM)] low observables (LO), threat avoidance through mission planning, Suppression of Enemy Air Defenses (SEAD), and maneuv e r s To maximize the reduction in susceptibility in a c o s t e f f e c t i v e design, we must examine the proper balance of all the available methods. Although many of these techniques have been in use for y e a r s effective EW has been a primary consideration only since the Vietnam W a r The application of LO is even more recent. To evaluate alternative concepts, we must accurately quantify the combined effects of these susceptibility reduction technologies. The "Low Observables and Countermeasures Complementary Capabilities for Aircraft Surviv a b i l i t y symposium, held in Monterey, CA in August 1998 w a s co-sponsored by the National Defense Industrial Association (NDIA) and the Association of Old Crows ( A OC). The synergistic application of LO and CMs to reduce aircraft susceptibility was discussed at this s y m posium. The objective of the symposium was to discuss the leveraging effect of the integrated application of EW and LO to improve aircraft surviv a b i l i t y and how this balanced integration of technologies significantly surpasses the contribution of either concept applied separ a t e l y The presentations introduced many considerations necessary to achieve a cost-effective design through a balanced approach to susceptibility reduction. H o w e ve r no one proposed a methodology to integrate these technologies to achieve a truly cost-effective system. Technology has advanced to a point where integrated LO/CM systems are not only feasible, but also are being built and tested. Many attendees indicated that the symposium was a first step toward achieving a joint capability within the community; how e v er we still have a long way to go before the LO and EW communities will work together effectively on combined EW/LO concepts to achieve the most cost-effective designs. The symposium showed that there is still too much of a "them versus us" (i.e., EW versus LO) attitude that blocks the way toward a truly integrated solution. The concept of integration (or balance) has not caught on at a n y in both the operational and aircraft survivability communities incorrectly use the words "surviva b i l i t y ," "susceptibility," and "vulnerability" i n t e r c h a n g e a b l y From the pilot or operational commander's viewpoint, surviv a b i l i t y is the w a t c h w ord. They want the aircraft and pilot to return unscathed to fly another mission. Survivability is a combination of susceptibility (the ability of a threat system to successfully engage an aircraft) and vulnerability (the probability that an aircraft will actually be damaged when a missile passes close enough to the aircraft to fuse). An aircraft can be made more survivable by reducing either its susceptibility to the threat system or its vulnerability to the detonated warhead, or a combination of both. Susceptibility reduction can be achieved by many methods. One method is electronic warfare (EW) [a broad category that includes countermeasures Aircraft Survivability Spring 1999 6 A i r craft Sur v i v a b i l i t y : A Balanced Susceptability Reduction Appr o a c h by Mr. Robert T. (Tom) W e b b e r M F r om the pilot or operational commander's viewpoint, survivability is the watchwor d Photo by Denny Lombard and Eric Schulzinger

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all program lev e l s How e ve r some programs are leading the push toward achieving an effective EW and LO blend. In developing the F-22, numerous LO and EW concepts were considered in the trade studies that resulted in the effective balance evident in toda y s design, as briefed by Mr. Al Pruden at the Monterey Symposium. The JSF Program will demonstrate an even larger step in balancing EW and LO technology to achieve low susceptibility to the current and future threat as LockheedMartin and Boeing strive to develop an effective and surv i v able design, while meeting the many cost, performa n c e producibility, and maintainability requirements. Other balanced approaches may also exist in companies proprietary concepts or within classified areas. F e w presenters actually showed analyses that demonstrated the synergistic effects of integrating both technologies to a c h i e v e a result that is greater than either contributor; when they did, the LO community emphasized LO reduction with the use of EW to augment surviv a b i l i t y where necessary, whereas the EW community emphasized a little LO to make the EW job easier. One of the most important messages in the s y m p o sium was presented by Lt Gen George Muellner, USAF ( R et) (former Principal Deputy Assistant Secretary of the Air Force for Acquisition) in his remarks on the first day: The greatest need is for a metric, a measure of warfighter utility, that can be used across both disciplines to effectively compare and trade LO and EW solutions. The first step the community must take is to define and develop this metric and credible modeling and simulation (M&S) to quantify the value of alternative EW and LO concepts. The presenters who mentioned M&S b e l i e v ed that current M&S is inadequate to accurately quantify EW effects, particularly in the area of countercountermeasures (CCMs). Some presenters also had similar comments regarding quantifying the benefits d e r i v ed from LO. Accurately quantifying this balanced solution (including aircraft performance and operational conc e p t s which were barely mentioned at the s y m p o s i u m ) is necessary to develop future military aircraft that are truly cost-effective, survivable sy s t e m s The cost factor needs more in-depth study. Most people do not consider the "T r u e Full Cost of EW" when discussing the cost of LO. Lt Col Bob Gierard USAF ( S A F / A QL), presented a paper on The Cost and C o m p a r ative Effectiveness of EW and LO. He demonstrated that when the total costs of EW Systems and LO S y stems capable of performing similar missions (including supporting systems) are compared, their total costs are similar. Some attendees did not support Lt Col G i e r a r d s conclusion, which demonstrates w h y the survivability community must dev e l op and agree on a methodology to correctly determine and assess the true costs of the combined EW and LO system approach to surviva b i l i t y If the combat objective is the destruction of a specific target, all costs and penalties associated with accomplishing that objective with each design must be considered. Thus, cost is not only the procurement dollars of an aircraft. Other considerations are weight and performance changes; cost of supporting f o r c e s SEAD, expendables, and lost aircraft; and the possible cost of delays in achieving the required objective (such as putting other forces in harms wa y ) W h e r e do we go from here? U n f o r t u n a t e l y we have barely scratched the surface with this symposium. I hope that this article has generated additional insight and interest in this subject. We must work together to clear some of the hurdles identified here and at the symposium. I would like to hear the thoughts of the survivability community. As a member of NDIAs Air Combat Surviv a b i l i t y D i v i s i o n s Executive Board, I will act as a clearing house for your ideas and present them at a future symposium. F B i o g r a p h y M r .W e b ber is the Manager of the Lockheed Mar t i n Skunk W o rk s System Requirements and A n a ly s i s D i v i s i o n This Division is r e s p o n s i b le for dev e l o p i n g and justifying the r e q u i r ements for all Skunk W o rk s P ro g r a m s as well as quantifying the resulting surv i v ability and eff e c t i v eness of these systems. H e r e c e i v ed a B.S.in Eng i n e e r ing from UCLA,and an M B A .f r om Pe p p e r dine Univ e rs i t y .He was r e c e n t l y aw a r ded the 1998 Air Combat Sur v i v a b i l i t y L e a d e r ship Aw a r d for his w o r k in developing analysis methodology of low observable (LO) conce p t s H e p re s e n t l y serves on the National Defense Industr i a l Association (NDIA)Air Combat Sur v i v a b i l i t y D i v i s i o n s Ex e c u t i v e Boar d He may be reached at 805.572.7011 or tom.w e b ber @lmco c o m Aircraft Survivability Spring 1999 7

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technology would allow, and equip the force structure with it. Despite Winston Churchills comment that "nothing in life is so exhihilarating as to be shot at without result," it is better that the first shot never be fired. If our force can accomplish its mission without having defensive missiles launched, the pilots will avoid the intense stress that comes when a missile is in the air. The Real W o r l d There has never been enough money to do what we wanted to do because the budgeteers compete betw e e n EW and LO. Yet, the situation has worsened. Our defense budget is at its lowest pointas a fraction of the gross national product (GNP)since before Pearl Harbor. If we are to have the best force possible for limited dollars, we must cease the competition between LO and EW and begin working together. A notional trade-off curve between the cost of better LO or better EW, with aircraft survivability held constant, might resemble a "U." Going toward "perfect" LO to a c h i e v e survivability could break the bank, whereas going toward "perfect" EW does the same. How e ve r a cost minimum might exist somewhere in betw e e n T h e r e f o r e we might be able to search for a cost-effective solution that permits our military to wage war but return home afterw a r d s You may call this solution Cost as an Independent Variable (CAIV), or simply consider this as applying solid systems engineering principles to the problem of aircraft surviv a b i l i t y Our fictitious curve will depend clearly on the platform and its mission. Further, the suggested trade-off ignores the type of LO (e.g., frontal, all-aspect) and types of EW ( e .g., on-board, stand-of). Drawing a valid curve will require a good model, that which is one of our shortfalls. We also must consider life-cycle cost, along with dev e l opment and initial acquisition. As we strive for "perfect LO" and/or "the ultimate EW suite," the cost of supporting these systems escalates dramatically. Model Development To ensure that we can do valid and robust cost/benefit trade-offs, the current state of modeling must be eaders of this publication are usually focused on a single aspect of aircraft s u r v i va b i l i t y When this focus becomes so narrowed that the other survivability components are lost from the field of view, s t o vepiping" may occur. In this manner, low o b s e r v ables (LO) and electronic warfare (EW) h a ve tended to become stovepipes resulting in a lack of communication between the two technical communities. To the casual observ e r LO and EW are perfect candidates for stovepiping because they appear to be opposites. If one (perfect) sy s t e m existed, a second would not be needed. If y o u could not be seen, you could not be easily hit with guided w e a p o n s On the other hand, if you could spoof a guided munition, it w o u l d not matter if you were seen. F u r t h e r LO and EW can interfere with each other. EW requires antennas; to w o r k EW systems need to take in information, so that disinformation can be sent out. H o w e ve r the LO designer, does not like antennas because they create an additional cross section, which is not w a n t e d G i v en the limitations on resourcesspecifi c a l l y money-coupled with the stov e p i p e m e n t a l i t y a natural rivalry developed. The budgeteers quickly bought into the idea that if you had LO, you would not need money for E W Money would be saved, they reasoned, to be allocated to other priorities. Consequently, EW lost funds. The problem is that neither perfection nor invisible aircraft exist. Given enough money, h o w e ve r engineering perfection, that is enough to accomplish the mission, can be a c h i e v ed. Yet, the entire situation ev o l ve d because of a lack of funds. If enough money were on hand to do whate v er anyone wanted, stealth would clearly be the way to go. Build the most invisible aircraft that Aircraft Survivability Spring 1999 8 Integrated Low Observables and Countermeasures by Mr. Ron "Mutz" Mutzelbur g Mr. Tony Grieco R

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impro v ed. LO effectiveness modeling tends to be reasonably tractable with excellent examples from Air Force Studies performed by federally funded R&D centers, such as IDA and Rand. With respect to EW, we now use "Greybeard" round tables to codify the effects of defensive electronic countermeasures (ECM) for modeling purposes. We must do better Although the authors do not ha v e a fa v orite solu tion, we were encouraged with results from the Susceptibility Model Assessment and Range Test (SMART) project, funded by (D, TSE&E). Perhaps that project could be continued or institutionalized. At the End of the Day Survivability encompasses not only LO and EW but also tactics, vulnerability, and extent of standoff. Arguments ha v e been advanced, ho w ever spe ciously, that if we had perfect LO or EW (or a com bination of both that did the same thingno hits on the aircraft from guided weapons) we would not need vulnerability reduction. W e find those arguments disingenuous. United States experience in Southeast Asia sho w ed that w e lost about 50 percent of our aircraft to fuel-related events. Designing an aircraft without fire suppres sion does not appear wise if our LO/EW solution is not totally robust or if the enemy gets a lucky hit. Furthermore, some aircraft ha v e missions that dic tate that they fly low and slo w and not enough LO and EW exists to ensure no hits; therefore, they also need vulnerability reduction. F Biographies M r M u t ze l b u r g r e c e i v ed his B.S.I.E. f r om Wayne State U n i ve r sity and his M.S.in Industrial and Systems Engineering from Ohio State University He is the Deputy Director for Air W arfare within the Of f ice of Strategic and T actical Systems, Under Secretary of Defense for Acquisition &T echnolog y. Mutz is responsible for acquisition o v ersight f or the B-1, B-2,C-17, F-22, F-18, JSTARS, n umerous air-to-air and air-to-g r ound weapons and numerous other aeronau tical prog r ams.He may be reached at 703.697.8184. Mr Grieco has o v er 35 years of experience in EW He received his M.S.in Engineering Management from the University of C a l i fo rn i a a M.S.in Electrical Eng i n e e r ing from the University of Missouri and a B.S. in Electrical Engineering from F r esno State College.Anthony is the Deputy Director Electronic W arfare, Strategic and T actical Systems Of f ice, Under Secretary of Defense for Acquisition and T echnolog y. He may be reached at 703.697.3619. Aircraft Survivability Spring 1999 9 i t y They are becoming more capable and should replace manned vehicles for many tasks being performed today. They also must be surviv a b l e One last point. Information operations are ov e r s h a d o wing hardw a r e We must have credible airframes, but the speed and agility of information are gaining importance ov e r massed metal. It may be possible to inflict greater loss on an adversary using information rather than missiles. C o n c l u s i o n The bottom line of military operations today is weapons on target. Survivability is a product of signature, aircraft vulnerability countermeasures, and integration of multi source information and weapons. An inte grated, s y stemic, balanced approach to sur vivability offers the best pa y off. Let us lever age our technical strength, experience, and industrial savvy to our advantage and mo ve forward no w. F F o o t n o t e s 1 Dev Zakheim, Trends in Military Spending and Weapons Systems Costs, S A CLANT Seminar Presentation, June 1998. B i o g r a p h y Vice A d m i r al William J.Fallon is a graduate of the N a val War Colleg e N ew p o rt R I the National W a r C o l l e g e in W a s h i n g t o n D C and has a M.A. i n I n t e r national Studies from Old Dominion Univ e rs i t y He commanded Attack Squadron SIXTY FIVE e m b a r ked in USS DWIGHT D. E I S E N H OW E R ,M e d i u m Attack Wing ONE at NAS Oceana,V A and Carrier A i r Wing EIGHT in USS THEODORE R O O S E V E L T dur i n g O p e r ation DESERT STORM in 1991.He has been C o m m a n d e r ,SECOND Fleet and Striking Fleet Atlantic since November 1997.Vice A d m i r al F a l l o n m a y be reached at 757.444.2422. A u t ho r s note: A d m i n i s t r a t i v e and research assistance provided by LCDR Todd J. F l a n n e r y USN COMSECONDFLT Staff. c o n t i n ued from page 5 Lethal & Sur v i v a b l e

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Warfare Center Weapons Division) China Lake, California, to support weapons development. H u g h s first position at China Lake was as an operations analyst in the Warhead Branch where he w a s responsible for methodology development and lethality analy s i s He became branch head in February 1968. He standardized warhead test and e v aluation (T&E) data analysis procedures and characterization methodologies and was responsible for weapon system lethality analy s i s Shortly after joining China Lake, Hugh became interested in joint activities, which led him to the Joint Technical Coordinating Group for Munitions E f f e c t i v eness (JTCG/ME). The JTCG/ME was chartered in April 1966; one of its tasks was dev e l o p i n g the Joint Munitions Effectiveness Manuals (JMEM). In the early days, the primary interest of JT C G / M E was air-to-surface and surface-to-surface munitions. Hugh joined the JTCG/ME in 1969 and, because of his interest in aircraft targets, became chairman of the Air Target Vulnerability Subgroup. To create more interest in air-to-air and surface-to-air missiles, Hugh established and chaired the Missile Ev a l u a t i o n Subgroup and later the Anti-Air Working Group which developed air target JMEMs and associated m e t h o d o l o g i e s Prior to that time, Hugh convinced D r Joe Sperrazza, head of Army Material Sy s t e m s A n a l y sis Agency (AMSAA) and Chairman of the J T CG/ME, to support the documentation of softw a r e models to minimize the proliferation of modeling and simulation (M&S.) More than 30 models w e r e documented in an analysts manual and a users manual. These manuals played an important role in standardizing M&S in the JTCG/ME as well as in the later established JTCG/AS. In addition, Hugh was an a c t i v e member of the international T r i Pa r t i t e Technical Coordinating Program (TTCP) working in this technical area. D r Joe Sperrazza established a Surviv a b i l i t y Committee under the JTCG/ME to give surviv a b i l i t y a d v ocates a forum for pushing to establish the ne of the unheralded pioneers of aircraft survivability is Hubert "Hugh" Drake. Hugh made major contributions to surviv a b i l i t y specifically to the Joint Technical Coordinating Group on Aircraft Survivability (JT C G / A S ) Because he was a person who did the job without looking for praise, he did not r e c e i v e sufficient recognition for his many c o n t r i b u t i o n s Hugh is now going to r e c e i v e that recognition. Hugh joined the U.S. Navy as a reservist in January 1955 and attended Interior Communications Electricians School. He spent the majority of his Navy time onboard an Auxiliary Transport Demolition ship (a destro y er escort) that carried Navy Seals and Marine R a i d e r s He spent 9 months of his shipboard time in Japanese and Chinese waters before his honorable discharge in January 1957. He entered col lege the day after his discharge Hughs path to the field of aircraft sur v i v ability was somewhat roundabout. F ollowing his June 1961 graduation from California Polytechnic College at San Luis Obispo, with a B.S. in mathematics and a minor in electronics, Hugh joined the Boeing Company in Seattle, Washington. Here he became a first line supervisor in F ebruary 1962 responsible for the intersite circuitry development for the first five wings of the Minuteman I missile. He m o ved to Honeywell Corporation in Hopkins, Minnesota, in February 1964 to support ordnance development and trans ferred to the Micro-Switch Division in 1965 to establish an engineering analysis capa bility. In February 1966, he mo v ed to the N a val Weapons Center (now Naval Air Aircraft Survivability Spring 1999 10 Pioneers of Survivability H u b e r t Hugh Drake by Mr. Dale B. A t k i n s o n O

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J T CG/AS and then played a role in convincing the JLCs to charter the JTCG/AS, which occurred on 25 June 1971. The Director Defense Research and Engineering (DDR&E) then funded the Test and E v aluation Aircraft Survivability (TEAS) Program so the JTCG/AS could address the survivability of the A7, F-4, and AH-1 aircrafts. Dr. Sperrazza pressured the first JTCG/AS chairman to support quick response efforts to solve some of the aircraft loss problems in Southeast Asia. The unexpected heavy combat aircraft losses experienced in the early stages of the Southeast Asia conflict led the Joint Logistics Commanders (JLC) to establish the JTCG/AS. Hugh played a major role in establishing the JTCG/AS and later became the second chairman of the JTCG/AS Methodology Subgroup. His task was to realign the subgroup from its focus on human factors to the methods needed to perform aircraft survivability assessm e n t s He made major contributions toward getting the Methodology Subgroup focused on the right areas and initiating work on many of the models used today in surv i v ability assessment. The J T CG/AS initially focused on vulnerability reduction but later addressed all aspects of surviv a b i l i t y One interesting experience Hugh had was attempting to bridge the gap between electronic warfare (EW) and the rest of surviv a b i l i t y This attempt met with resistance from the EW side, which held the opinion that the JTCG/AS should concentrate on vulnerability and leave EW to the experts. With time and new play e r s this viewpoint changed significantly; and the JTCG/AS Susceptibility Subgroup now routinely addresses EW and has made major contributions to this area over the y e a r s Hughs contributions in initiating these changes were manifold. Hugh wishes to acknowledge that his accom plishments during his da y s in survivability o w ed much to the outstanding joint service personnel who worked with him. Hugh sa ys "They fought hard for the program and performed in an out standing manner." Hugh jokingly sa y s if he did one thing well it was "attempting to set a standard of (1) early to bed, (2) minimiz ing after-hours frivolity, (3) keeping every ones nose to the grind stone, and (4) main taining a gung-ho image." As Hugh empha s i z e s "Those working with me w o r k e d hard, pla y ed hard, and accomplished a sig nificant amount of work." Hugh sa y s that rumors that he used unscrupulous methods to gain consensus from his working groups w ere all greatly exaggerated. H u g h s career took a turn when in 1980 the China Lake Technical Director asked him to take over responsibility for the Electronic Warfare Test and Ev a l u a t i o n Simulation (EWTES) Division, commonly referred to as Echo R a n g e Hugh directed the range (inv o l v ed in EW test and ev a l u a t i o n ) through a get-well program requiring a coordinated approach involving in-house resources as well as NAVAIR, OPNAV and user commands including COMOPTEVFOR, VX-5, TOPGUN, DET WHIDBEY, and other Navy organizations. He established a N a vy Tri-Lab committee to oversee simulator development and supported the Crossbow Committee. Hugh spent the next 3 1 /2 y ears orchestrating a get-well program. He worked long da y s and long weeks. His one regret was his work did not lea v e time to pursue joint service programs. After the successful Echo Range get-well program, Hugh was selected as associate department head of the Electronic Warfare Department, where he was directly responsible for o v er sight of EW development programs ( i n vo l v ed in antiradiation weapons and electronic s y stems RDT&E) and maintained direct liaison with SPAWAR, NAV A I R OPNA V and OSD. He was also a member of the Fallon, Nevada, training range fleet project team. He established the depart m e n t s Long-Range Planning Office in 1987, where he headed the Navy Tactical T raining Range Roadmap Committee and Aircraft Survivability Spring 1999 11 c o n t i n ued on page 2 9

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in the context of information warfare or information c o n t r o l T h r eat is Reactive If the threat were constant, defeating the threat system would be simple. Unfortunately, threat improvement and countermeasure response is a continual response and counter-response (Figure 1). As threat lethality improv e s platform survivability and mission success degrades, and a countermeasure response is necessitated. T r a d i t i o n a l l y the countermeasure response has been jamming related. R e c e n t l y the countermeasure response can and will include defense suppression, dilution, signature reduction, and jamming. The objective is to establish a "low-cost" combined countermeasure response that will necessitate a "highcost" threat response. Traditional Responses No Longer V a l i d The threat today is dynamic and responsive, representing the best that money can buy. Gone are the days of a homogeneous monolithic threat. Emerging is a r a i n b o w threat that combines technologies and platforms from multiple countries and design philosophies. The export of advanced technology is now limited only by the buy e r s pocketbook. It once took 10 to 15 years to proliferate advanced technologies to the third w o r l d ; n o w, co-production and co-procurement accelerate the proliferation. Multispectral and super-agility summarize he blending of electronic warfare (EW) and low observables (LO) offers unique operational opportunities and operational challenges. By reducing and controlling a platforms passive signature and emissions, new or previously developed EW technologies and techniques may now be feasible where once they were not. Existing warfare applicat i o n s such as stand-off jamming, and new warfare applications that were considered too p o wer hungry or not robust enough may now be feasible. This success does not come without challenges. For example, how do we effect i v ely marry a technologys concept of operations that was conceived in covertness (LO) with one that was conceived in overtness (electronic countermeasure [ECM] jamming)? This process requires a cost-effective balancing of the two technologies and may inv o l v e changes in operational employment concepts and tact i c s Overall, the combined results are i m p r o ved platform effectiveness and i m p r o ved countermeasure robustness. Common MOE is Fundamental Blending these technologies requires establishing a best value for a platform. Establishing the best value will require defining a measure of effectiveness (MOE), mission success, that is common to both technologies and then optimizing the platform for mission success. F o r e x a m p l e if the goal is to defeat the threat system in the context of the mission, this w o u l d require effective identification of the threat syst e m s kill chain and then exploitation of the kill chain vulnerabilities. Robustness is a c h i e v ed by not relying on the disruption of one element of the kill chain, but rather disrupting or degrading multiple kill chain elem e n t s Note, that disrupting or degrading the kill chain may begin days before the mission Aircraft Survivability Spring 1999 12 E l e c t r onic W a rf a r e and Low Obser v a b i l i t y Technology to Defeat RF and IR Thr e a t s by Mr. Dan Gobel F i g u r e 1. Response/Counter Response Design Evolution Threat Lethality Impro v ed Capability Platform Survivability Degrades Platform Survivability Countermeasure Development Necessitates Countermeasure R esponse T

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the threat capabilities of today and tomorrow. The threat continues to exploit the total radio frequency (RF) and infrared (IR) spectrum to minimize its vulnerability to single kill chain element failures. Threat agility exceeds the limits of manned aircraft, minimizing the traditional countermeasure tactics to out-maneuver or outrun the threat. New Design Appr o a c h Blending LO and EW technologies offers the ability to degrade the total susceptibility kill chain from d e l a yed acquisition to increased endgame miss distance (Figure 2). The LO concept is to degrade the engageability of the platform by the threat by attacking the fundamental physics of the detection and track processes. Traditional EMCs rely on exploiting threat sy s t e m design vulnerabilities and often use high-powered jamming to saturate or deceive the threat. Fundamentally, the concepts of operations of the two technologies are at opposite ends of the spectrum. Independently, both technologies are limited by affordability. Blending the t w o technologies will require philosophical changes in both communities. The EW community shift will be to d e v elop countermeasures (CM) that work in concert with LO technologies. A shift in philosophy will be from overt to covert concepts for platform integration Aircraft Survivability Spring 1999 13 and countermeasure operation. This effort will include a greater emphasis on situational awareness: to manage the countermeasure timing or use, to manage platform observ a b i l i t y and to focus the countermeasure response. In addition, blending the technologies offers an ability to develop and integrate ECMs that exploit the benefits of signature reduction and offer techniques and technologies that attack the fundamental physics of the engagement. F B i o g r a p h y M r .Dan J.Gobel is the Manager of A d va n c e d C o u n t e rm e a s u r e Pr o g rams for Sander s a Lockheed M a r tin Company.His responsibilities include the c o n c e pt dev e l o p m e n t f o r m u l a t i o n a s s e s s m e n t and demonstration of advanced RF and IR elect r onic combat systems for use on tactical air c ra f t r o t a r y wing platf o r ms and military ground v e h i c l e s M r .Gobel has a Masters of Eng i n e e r ing in O p e r ations Research from Southern Methodist U n i ve r sity and a Bachelor of Science degree in E l e c t r ical Eng i n e e r ing from Purdue Univ e rs i t y H i s w o r k e x p e r ience includes ten y e a r s of advanced airc r aft pr o g ram dev e l o p m e n t v u l n e r ability anal y s i s and design,and operations analysis while e m p l o yed at General Dynamics,F o r t W o rt h D i v i s i o n He may be reached at 603.885.5382. F i g u r e 2. EW/LO Impact Every Phase of the Threat Engagement

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ZSU-57, and SA-7 as the primary threats to the attack helicopters T o evaluate the effectiveness of the scout/attack helicopter team in the European threat environ ment, the U.S. Arm y Europe, Canadian Forces Europe, and Federal Republic of Germany (FRG) forces conducted the Ansbach Trials. For the trials the United States provided AH-1G attack helicop ters with simulated T O W missiles, Canadians pro vided the OH-58C scout, and the FRG provided the armor force of Leopard tanks with its organic air defenseM-113/Vulcan and Redeye missiles. Trials w ere conducted in a free-play fashion o v er the Ansbach region and included three different tacti cal situations. For realistic attrition scoring, all pla yers were equipped with an early version of the Miles Laser weapons simulators Operational tactics for the scout/attack helicop ter were also refined during these trials. It was dis co v ered the key to modern helicopter effectiveness w as a change in tactics. Figure 1 illustrates the hel icopter tactics used for a ground attack. Rather than using the typical time-honored fixed-wing tactics of strafing attacks, the helicopter w ould be most effective if it emplo y ed ho v ering flight tactics at standoff ranges. Specifically, the sce nario worked as follo w sscout helicopters, transit Introduction The superb effectiveness and survivability of todays modern scout/attack helicopter w eapon s y stem is based on a series of developments made since the late 1960s This article traces the evolution of this w eapon s y stem to explore if it can surviv e in the future battlefield. Based on its histo ry, the authors of this article believe mod ern scout/attack helicopterswith their unique combination of technology and operational tacticswill remain a vital force in the combined arms Arm y. Initial development of todays helicop ters began as a result of the shift in U.S. military focus from operations in Vietnam to involvement in the NA T O alliance and the European Theater. Although more than 1 0,000 helicopters were sent to Vietnam, neither a significant armor threat nor sig nificant air defenses existed within that theater. Consequently, there was no con viction these helicopters would ha v e a role in addressing the midto high-intensity threat of NA T O / Pact Europe The U.S. Army AMSAA addressed these helicopter survivability issues in its AMH1 studies and concluded that helicopters although their losses may be high, could survive in the midto high-intensity AAA threat range. Mean w h i l e the CDC/ISS studies were being conducted to help define the attributes of a new attack heli copter that would replace the canceled AH56 Cheyenne. These studies included SRIconducted battle simulations and also concluded that the combat effectiveness of the attack helicopter in the midto highthreat range would be positiv e Both of these studies considered the ZSU-23/4, Aircraft Survivability Spring 1999 14 The Survivable Rotorcraft by Mr. David G. Harding Mr. Stephen A. Brumley F i g u r e 1. Rotorcraft Tactics for Ground Attack

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ing behind terrain mask, would pop-up and ho v er in brief exposures to view the region of interest while maintaining maximum standoff range. Multiple successive pop-ups of limited duration were conducted from different locations. To increase the difficulty of detection by opposing forces, exposure locations were chosen that provid ed a terrain, vegetation, or building backdrop to the helicopter The scout helicopters, having detected and locat ed the targets, would then call in and direct the attack helicopters to fire. The attack helicopters then would use similar tactics as those emplo y ed b y scout helicopters to conduct their attack. The limit ed duration of the helicopters exposure to threats became the fundamental difference between effec tive helicopter versus fixed-wing attack tactics Fixed-wing aircraft with current weapons must fly a trajectory that allo w s line-of-sight for its sen sors to search, acquire, identify, and lock-on to the target. Depending on the weapon, the fixed-wing aircraft must remain unmasked during its weapon launch and guidance The ho v ering helicopter, ho w ever, may regain co v er within very few seconds of a perceived threat, although engagement tactics may require it to "sta y on the line" if a missile has been fired. Still, the helicopters exposure time to threats is typically sig nificantly shorter than for fixed-wing aircraft. A major conclusion drawn from the exposure statistics gained during the Ansbach trials was that although the intent of the helicopters ho v ering tac tics was to stand off beyond the range of threat w eapons and sensors, terrain and tactics emplo y ed by both forces usually preclud ed complete standoff. Because of this fact, adjacent clutter and minimum exposure times became equally important factors for helicopter effectiveness. That is, high clutter minimized the chance of detection at the exposure range, while brief exposure times could "beat" the threat timeline Figure 2 illustrates the distribution of engagement ranges the AH-1s firing T O Ws experienced during the Ansbach trials. As the figure sho ws half of the engagements occurred at less than two-thirds of the TO Ws maximum range. Exposure times w ere driven by the difficulty in detecting the armor units at these ranges using a moderate and narrow field-of-view optical sight and the time required to fire and guide the tow missile The results of the Ansbach trials were a stunning success for validating the effec tiveness of the helicopter force because they pro v ed that, at standoff, in terrain, helicopters were very difficult to detect and that helicopters ho v ering near co v er the helicopter could terminate their exposure to risks or engagement at any time. Figure 3 illustrates an attack helicopter masked in terrain. F ollowing the Ansbach Trails, a series of scout/attack helicopter field trials w e r e conducted throughout the 1970s. Trials at the Combat Developments Experiments Aircraft Survivability Spring 1999 15 c o n t i n ued on page 1 6 F i g u r e 2. Ansbach Engagement Statistics F i g u r e 3. Photograph of the Stealth Rotor c r a f t At Standoff, detection of the helicopter is difficult and time consuming n Reasons for Success

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a vionics s y stem allo w ed targets to be acquired with in a much shorter timeline, even during the da y. A dditionally, a significant gun with light armor capability was included with substantial ammuni tion. Vulnerability reduction techniques w e r e required against small arms up to 23mm HEI and infrared signature reduction was included in the basic design, rather than added on as was the case with prior helicopters In the early 1980s, the U.S. Army TRADOC con ducted a series of Mission Area Analyses across the breadth of its forces. These analyses examined the mission, threats, technological opportunities, and current plans for impro v ements in each branch of the service, including aviation. It was decided that within the scout/attack portion of the aviation fleet a new helicopter should be developed that would be a fully night-capable scout for the Apache team in the Heavy Divisions and would replace the AH1 attack helicopter and OH-58C scouts in the Light D i v i s i o n s Thus, development of the LHX/ Comanche began. Studies on how to fulfill the LHX / Comanche concept focused on three areasimpro v ed sensors and integrated and automated avionics, impro v ed w eapons, and reduced signatures. The latter being based on emerging "stealth" technology. To devel op the LHX/Comanches concepts and require ments, extensive analyses and simulations were conducted that applied the key factors learned in previous trials. Specifically, maximum stand-off range in terrain, limited exposure time, firing rate and detectibility, including emerging a v i o n i c s computer, sensor weapons, and stealth technology developments were applied to the analyses Reduced Signatures The fundamentals of ho v ering tactics, stand-off distance, and adjacent terrain clutter all drive the signature reduction requirements involved in creat ing a significant helicopter combat capability. because of these factors, signature reduction requirements for helicopters is factors less than that required for the F-117, which operates high in the sky without the clutter Comanche radar signature reduction w a s achieved by shaping and materials in the classical Center in Fort Ord were conducted with both AH-1 and AH-56 Cheyenne proto types. These trials examined and quanti fied the factors involved with, and devel oped tactics to include, night operations With Project MASSETER at Fort Hood, T exas, major contributions were made in developing camouflage for helicopters The preoccupation with anti-armor s ystems and close air support in the midto high-threat scenario had generated a plethora of competing weapons s y stems In response, the Undersecretary of Defense commanded a series of trials in 1978 that w ould compare "competing" aviation s ystems. These trials were named TASVAL. The results of T A S V AL showed that despite the significant increase in quality and quantity of air defense threats, scout/attack helicopters still produced sig nificant loss exchange ratios vice the opposing force. Their performance, although somewhat less than that experi enced in the Ansbach trials, remained highly effective. The helicopters, ev e n when presented with more modern air defense threats than those used during the Ansbach trials, were difficult to detect. Based on the results of TASVAL, the attack helicopter programs were granted addi tional funding to continue dev e l o p i n g new technologies Modern Helicopters Beginning in the mid-1970s and based on a firm foundation of the lessons learned from the previously conducted tri als, the Apache and Hellfire were devel oped. The Apache was originally required to survive in the presence of the ZSU23/57, AAA, and SA-7 air defense threats Meanwhile new technologies, such as a FLIR/ LLTV/Optics target acquisition s ystem and FLIR/IHADS pilots night vision sy stem extended use of the Apache attack helicopters to include night operations A dditionally, the FLIR and the integrated Aircraft Survivability Spring 1999 16

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way as Figure 4 sho ws Similarly, the infrared sig nature was reduced by cooling and completely shielding the exhaust and insulating the airframe so that lock-on was difficult to achieve when the helicopter was viewed against the terrain back ground. Visual signature was controlled by canop y shaping and advanced paints. Acoustic signature w as reduced by the use of fiv e main-rotor blades with swept-tapered-tips and a multi-bladed, shield ed fantail anti-torque s y stem. During the mid-1980s the creation of the Longbow radar target acquisition s y stem and the companion RF seeker Hellfire missile further enhanced the effectiveness of the scout/attack heli copter weapons s y stem. First, the mast-mounted Longbow radar provid ed target acquisition in almost all weather, day or night, against multiple stationary and moving tar gets. This enabled target acquisition, identification, and classification to be accomplished automatical ly in many conditions providing both detection and prioritization of targets, via exposure of just the sensor Second, the RF seeker Hellfire provided a true "fire and forget" missile. No helicopter exposure w as required to either launch or guide the Hellfire Initially, the Longbow/RF Hellfire developments w ere included into portions of the Apache fleet as the AH-64D. Eventually, these capabilities will be included in Comanche More recent developments in the scout/attack helicopter mission technologies include enhance ments in communications, navigation, and intelli gence. For example, the "Automatic Target Hand-off System" transmits targeting data among the helicopter team via digital burst transmission, whereas integrated GPS/INS navigation provides far greater accuracy in both navigation and the target hand-off process. Additionally, largescale instrumented field trials have been enhanced significantly by the dev e l o p ment of SIMNET and its associated com prehensive Battle Lab war gaming simula tions. Perfect intelligence results in the absolute minimum number of exposures at the optimum location in terms of stand off, background and field-of-view These dev e l o p m e n t s when they are fully implemented, will improve the scout/attack helicopter engagement parameters. Stand-off ranges for the scout portion of the team will continue to be based on terrain and tactics and are not expected to change much, while attack machines may stand off behind mask at ranges limited primarily by missile range Overall, exposure times will be shorter. A t most tactical ranges, Comanche will be difficult to detect. Further, all this will be accomplished day or night in all weather and should result in combat effectiveness against modern air defense threats that is at least as good as the results achieved in the Ansbach Trials Future Considerations The question of survivability for the scout/attack helicopter s y stem then is not, "Can the scout/attack helicopter weapon sy stem survive on the future battlefield?" but "Will sensors and weapons on the future battlefield exist that will engage and destroy the helicopter?" The answer is it is unlikely. The nearto midterm develop ment of rapid scanning line-of-sight sen sors will not significantly improve the detection of Comanchelike helicopters operating in terrain. There are simply not enough signals a v ailable to produce the Aircraft Survivability Spring 1999 17 F i g u r e 4. The Comanche RAH-66 c o n t i n ued on page 2 0

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requested for e v e r y mission.) Therefore, LOis also considered adequate, but not a magic bullet. C o n s e q u e n t l y the current trend is to use a combination of LO and EW technologies for surviv a b i l i t y This trend is evidenced by programs to backfit LO enhancements to EW-equipped aircraft, and add EW to LO aircraft. This combination offers great s y n e r g y LO significantly reduces EW requirements. Because LO can enable avoidance of many threats, the EW system does not have to jam everything in the battlefield. A d d i t i o n a l l y the unavoidable threats can be jammed using lower pow e r Similarly, EW reduces LO requirem e n t s Because EW situational awareness can enable threat av o i d a n c e the aircraft does not have to be "LO" to everything in the battlefield. Furthermore, the robust EW endgame countermeasures can make "statistical" rather than absolute LO acceptable. A 97 percent probability of not being detected, coupled with a 97 percent probability of preventing a missile kill, yields a 99.9 percent probability of survival. Given this s y n e r g y the question becomes how to optimize the integration of LO and EW. Two basic approaches exist: build all the stealth that we can (or cannot) afford, or e v aluate LO on its own a n d as a function of EW. The premise is that the second approach yields optimum performance at affordable cost. Let us examine LO/EW interaction as cross section is reduced. The LO payoff versus range is linear; the detection range decreases as the 1 /4 root of RCS reduction. EW performance also has a linear component versus RCS. Jamming power reduces by the 1 / 2 root of RCS reduction. How e ve r EW performance also has incremental improvements at specific RCS thresholds. These improvements include EW system simplification and cost reduction, but more importantly EW system enabling. Figure 1 illustrates incremental EW simplification. As LO is increased (RCS is decreased), EW power requirements are reduced as the square root of RCS. As the EW p o wer requirement decreases, it crosses important amplifier technology thresholds. The first increment is to lthough electronic warfare (EW) has existed since the 1940s, low observability (LO) has existed only about half that time. These two technologies have been developing independently, but that is changing. The two technologies are s y n e r g i s tic, but at certain levels of radar cross section ( R CS) reduction, EW techniques are enabled, greatly leveraging the survivability achiev e d with LO. Thus, by treating stealth as a dependent variable to EW, it is possible to optimize affordable solutions. H i s t o r i c a l l y achieving airborne surviv a b i l i t y has been solely via EW means. Even though the robustness of EW has matured to the point of l i v e fire testing, robust techniques are typically limited to endgame scenarios. These techniques engage only after a missile has been fired. Thus, EW is considered adequate, but not the desired "magic bullet." Most recently, achieving airborne survivability has been solely via LO. Even though the LO F-117 aircraft suffered zero losses in DESERT STORM, at least one-third of the missions were flo w n with EW support. (According to those scheduling the F-117 missions, EW support w a s Aircraft Survivability Spring 1999 18 Stealth As A Dependent Variable To EW by Mr. Paul H. Berkowitz F i g u r e 1. Incremental EW Simplification A

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change from traveling wave tube (TWT) and microwave p o wer module (MPM) transmit amplifiers to smaller, l i g h t e r less expensive solid-state amplifiers. The second increment reduces from solid state to Monolithic M i c r o wave Integrated Circuit (MMIC) components, again with corresponding reductions in size, weight, and cost. This simplification is desirable, but is not dramatic enough to drive LO design. For incremental enabling of E W how e ve r the payoffs warrant consideration during LO design. C o n v entional EW implementation can be either electronically or physically incompatible with LO. For examp l e a broadband noise jammer is inherently electronically incompatible with LO. Similarly, large EW antennas can physically prevent their usage on LO aircraft. H o w e ve r incremental cross section reductions can enable EW technologies to be compatible with LO. An example using towed decoy technology will be analyzed. The baseline is a conventional fighter with a nominal 10 m 2 cross section, using a smart towed decoy, confronted by a typical pulsed I Band surface-to-air-missiles (SAM) radar with a +125 dBm effective radiated p o wer (ERP). At a nominal 5 nautical mile range, using the standard radar range equation with these h y p o t h e t ical values results in a jamming power requirement of 50 to 100 Watts to achieve the desired jam-to-signal (J/S) ratio. This process requires (TWT) transmitter technology in the decoy. Figure 2 illustrates conv e n tional towed decoy concept. If RCS is reduced by 10 dB, to 1 m 2 or 0 dBsm, the EW power requirement reduces between 5 and 10 w a t t s which still requires a TWT transmitter in the d e c o y. How e ve r this has a potential impact because the decoy physical size can create an echo that competes with the aircraft LO. A typical decoy size measures 16 inches long and 2 1 / 2 inches wide. The cross section of a simple cylinder is nominally 1 m 2 at I/J Band; with fins and stabilizers, it is larger. As shown in Figure 3 this decoy cross section is clearly incompatible with the aircraft RCS and eliminates a valuable EW asset for this size aircraft. H o w e ve r if the RCS can be reduced another 3 dB (to 0.5 m 2 ) the EW power requirement reduces between 2 1 / 2 and 5 W a t t s This change makes solid-state transmitter technology viable for the decoy. In turn, a much smaller decoy is enabled. Figure 4 illustrates a recent minit o wed decoy design, which is 4 inches long by 1 inch wide. Its cross section is nominally 0.01 m 2 or -20 dBsm at I/J Band, which is clearly compatible with the LO RCS, returning to the aircraft and decoy balance as shown in Figure 2. Thus, this 3-dB increment in LO enables the t o wed decoy EW and highly leverages the surv i v ability increase of the incremental R C S reduction. Similarly, another 10-dB RCS reduction can reduce the vehicle cross section below the decoy towline power wire RCS, again disabling the use of the towed decoy. Likewise, another 3-dB RCS reduction enables the d e l i v ery of power to the decoy via a fiber optic line, eliminating the metallic tow line wires and their cross sections. Again, the incremental 3-dB RCS reduction enables the v a l u a b l e t o wed decoy EW. F u r t h e r m o r e R C S r e d u c t i o n s can enable not only additional towed deco y size reductions but also unpowered decoys, which simply launch the RF signal from the t o w line into an antenna without an amplifier. As is demonstrated in the towed decoy a n a l ys i s the LO/EW interaction can be somewhat complex. Incremental RCS levels can either disable or enable the use of tow e d d e c o y. This important factor must be considered during LO design. Aircraft Survivability Spring 1999 19 F i g u r e 2. Conventional Decoy on Conventional Air c r a f t F i g u r e 3. Conventional Decoy on LO Air c r a f t c o n t i n ued on page 2 0

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The Survivable Rotor c r a f t Similar increments exist for other EW techniques. Onboard techniques, such as Cross Eye Cross Polarization, require hundreds of Watts of power for c o n v entionalsize aircraft. This technique requires TWT t r a n s m i t t e r s ferrite components, and waveguide transmission lines, all of which add significant size, w e i g h t and cost. Furthermore, Cross Eye may require a large baseline separation between antennas, which for conventional aircraft is about 75 feet. None of these factors are conducive to installation on an LO v e h i c l e How e ve r a 25-dB reduction in RCS eliminates the need for TWTs, f e r r i t e s and wav e g u i d e enabling an all-solid-state component and cable implementation. In addition, the antenna separation requirement for Cross Eye is reduced to 18 feet. This RCS reduction significantly enhances the feasibility of robust Cross Eye Cross Polarization EW. Another 10-dB RCS reduction enables an all-MMIC solution and 10-foot Cross Eye separation, further increasing robust Cross Eye/Cross Polarization EW feasibility. In summary, it has been determined that many interactions between LO and EW are incremental. This incremental relationship offers significant opportunities for optimization. The LO payoff can be multiplied at EW enabling increments. To exploit these opportunities, it is necessary to evaluate LO in context of its EW impacts during the initial design phase of a program. Thus, treating stealth as a dependent variable to EW will lead to optimum affordable solutions. F Biography M r B e r kowitz has w o r ked in the EW community for over 30 y e a r s and is curr e n t l y Ex e c u t i v e Vice President of Electr o Radiation Inc.in F a i r fi e l d ,N J .His EW e x p e r ience extends from B52 to B-2,F-4 to F-22,and MH-47 to SR-71.His LO backgr o u n d i n c ludes D A R P A studies as well as EW for Stealth air c ra f t M r B e r kowitz r e c e i v ed a B.S.E.E. f r om Rutg e r s Univ e r sity in 1968. H e m a y be reached at 973.808.9033. Aircraft Survivability Spring 1999 20 F i g u r e 4. Mini Towed Decoy signal-to-clutter levels that will allow detection in the brief timeline afforded the air defense sensor And although imaging-type sensors that could detect a Comanche-like target are clearly feasible, their timeline is, for the foreseeable future, too long to engage the fleeting targets. Non-line-of-sight imaging sensors, such as those developed for U A Vs also require significant timelines and rela tively narrow field-of-view. Additionally detection of camouflaged fleeting targets will require a very large number of nonline-of-sight imaging sensors. Because these imaging sensors will become vulner able, if not low-observable themselves, this approach is not optimum. C o n s e q u e n t l y any such solution is probably unaffordable by any nation for the foreseeable future. And because of this, todays modern helicopters can be expected to continue their role as a highly effective scout/attack weapons s y stem in the future battlefield. F Biographies M r H a r ding is the Dir e c t o r F u t u r e Pr o g r a m s A d v anced Rotor c r aft Systems,The Boeing Compan y. During his 36 years with Boeing, he has w or k ed on the design and de v elopment of the CH47, CH-46, HLH, LIT A-X, UTTAS, AAH, ASH, HSM and Commercial Chinook prog r ams. Mr Harding has specialized in the design and analysis of heli copter surviv a bility and combat ef f ectivenss fea tures.He may be reached at 610.591.8700. Mr Brumley presented Rotorcraft Surviv a bility: T he Role of LO and EW T echnologies at the Lo w Obser vab les and Countermeasures Symposium in A ugust 1998. c o n t i n ued from page 1 7 c o n t i n ued from page 1 9 Stealth As A Dependent

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Aircraft Survivability Spring 1999 21 and the TWA 800 accident has brought fire and explosion concerns to the forefront in transport aviation. Consequently, reducing fuel fire and explosion hazards is a matter of interest throughout the aviation community. The thrust of the meeting was to review the fuel fire detection, suppression, and explosion mitigation needs for military and civil a v i a t i o n and foster ways to expedite development and transition of technology to the aviation fleets. The presentations and discussions were tailored toward exploring potential for cooperat i v e approaches to focus and accelerate dev e l opment and leverage resources. M r Ralph Lauzze, Chairman of the meeting, c o n v ened the conference and introduced Admiral Robert Gormley, USN (ret), Chairman of the Combat Survivability Division, who provided the Introduction and Purpose of the meeting. The Guest Speaker, Dr. P a t r i c i a S a n d e r s Director, Test, Systems Engineering and Evaluation, Office of the Under Secretary of Defense for Acquisition and T e c h n o l o g y set the tone for the meeting by stressing that sharing information was not enough, that truly c o o p e r a t i v e programs would be necessary to s o l v e the aircraft fire and explosion issue. The initial speakers provided a broad pers p e c t i v e of fire problems from different dev e l opmental and operational perspectiv e s Mr. Ronald Mutzelberg, Deputy Director for Air Warfare in the Office of Strategic and T a c t i c a l S ys t e m s Under Secretary of Defense for Acquisition and T e c h n o l o g y provided an overview of the military perspective of aircraft fire and explosion problems. Dr. V e r n o n Ellingstad, Director of the Office of R e s e a r c h and Engineering, National T r a n s p o r t a t i o n Safety Board, provided an overview of the civilian perspective. Mr. Eric Schwartz, Executive Assistant to the Chief Engineer, The Boeing he National Defense Industrial Association (NDIA) sponsored a Fire and Explosion Information Exchange Meeting on October 2 1 1998 at the Defense Logistics Agency Headquarters, Ft. B e l v oir VA. The meeting was arranged by the Combat S u r v i v ability Division of the NDIA (formerly ADPA) to explore how the agencies working in fire and explosion research might come together to make progress in this important area by leveraging off each others initiativ e s for the common good. Participants included speakers representing the FAA, NTSB, NASA, Office of the Secretary of Defense, Army, Na v y Air F o r c e Department of Energy, Department of Commerce, and industry. Military and civil aviation share a continuing interest in reducing aircraft hazards from fire and explosion. H i s t o r i c a l l y fuel fire and explosion have been the leading cause of combat aircraft losses. Fire is one of the major contributors to aircraft incidents in civil aircraft, NDIA Aircraft F i r e and Explosion I n f o r mation Exchange Meeting by Mr. Ralph Lauzze M r Chuck P e d r i a n i M r Dale A t k i n s o n T c o n t i n ued on page 2 2

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Aircraft Survivability Spring 1999 22 C o m p a n y, presented a comparison of civilian and military views, citing the resulting differences in hardware solutions to the fire hazard p r o b l e m s Mr. Richard Hill, Program Manager, Aircraft Fire and Cabin Safety, Federal A v i a t i o n Administration, presented the results of the recent Aviation Rulemaking A d v i s o r y Committee (ARAC) study examining explosion hazards and potential solutions. The remaining presentations included details covering a wide range of active programs addressing the many facets of the fire and explosion hazard. The Services, F A A NASA, and industry perform active research and development programs to address the fire problem as manifested in their air systems and operational environment. NASA is the focal point for a new initiative to make a dramatic reduction in the civil accident rate. The Next Generation Fire Protection Program (NGP), is pursuing a replacement for Halon 1301. In response to the TWA 800 accident, the NTSB is overseeing a fuel explosion research program aimed at determining the cause of the of the T W A 800 explosion. In spite of the wide range of aircraft syst e m s missions, and basic operational object i v es represented at this meeting, there w e r e m a n y common threads throughout the pres e n t a t i o n s Many presenters stated that, at the heart of developing a better understanding, there is a need for better modeling and simulation technology at both ends of the spectrum precise physics based models to ev a l u ate phenomena, and somewhat less rigorous engineering models to be used in sy s t e m design and development. In addition, more widely accepted and validated dev e l o p m e n t and test methods are needed that can be correlated to basic physical principles. At this time, there is no established forum specifically for the coordination of fire and explosion technology development. Much of the coordination currently occurs on an ad hoc b a s i s There are many common needs within the technology that can be used as the basis for more information exchanges and, possibly, cooperative p r o g r a m s A structure for the exchange and coordination of fire and explosion information and programs could reduce development time, avoid duplication, and result in better solutions. Focused research, directed at kno w l edge and technology v o i d s common to all air platforms would facilitate the development of fire and explosion protection for all aircraft and save liv e s The participants agreed that, as a first step, DOD should take measures to centralize the information describing the work being performed by its organizat i o n s A single point of contact is needed to facilitate coordination between DOD efforts, and those initiated outside DOD. As a result of this discussion, the JT C G / A S will take action to act as the single face to the customer for DOD fire and explosion research. Secondly, the NDIA should sponsor a workshop to develop a similar centralized way of coordinating programs between DOD and other organizations in the civil sector. The w o r k shop could also develop prioritized goals that w o u l d form the basis for potential joint programs. For additional information, or comment, on the initiative to coordinate efforts in aircraft fire and/or explosion research, please contact one of the authors listed above, or the JTCG/AS Central Office. F B i o g r a p h i e s M r L a u z z e r e c e i v ed a B.S.in Mechanical Eng i n e e r ing fr o m P u r due Univ e r sity and an M.S.in Mechanical Eng i n e e r ing fr o m the Univ e r sity of Dayton in 1982.Ralph is the AFRL air c r aft vuln e r ability Test Director for Live F i r e Test and Evaluation (LFT&E). Ralph is the Air F o r ce Principal Member to the tr i s e r vice J o i n t Technical Coordinating Group on A i rc r aft Sur v i v a b i l i t y ,and is c u r r e n t l y its chair m a n He may be reached at 937-255-6823. M r .P e d r iani r e c e i v ed his B.S.in Mechanical Eng i n e e r ing fr o m P e n n s y l v ania State Univ e r sity in 1966.He is a project eng i n e e r with SURVICE Eng i n e e r ing Company, s e r ving as principal inv e s t i g ator and team leader in projects involving live f i r e testing, s u r v i v ability design,system r e q u i re m e n t s s u s c e ptibility r e d u c t i o n and vulnerability r e d u c t i o n He may be reached at chuck@surv i c e c o m M r .Atkinson is a consultant in the air c r aft combat sur v i v a b i l i t y a re a He r e t i r ed from the Office of the Secr e t a r y of Defense in 1992 after 34 y e a r s of gov e r nment service and remains active in the sur v i v ability ar e a M r .Atkinson played a major role in establishing sur v i v ability as a design discipline and was a char t e r member of the tr i s e r vice JTCG/AS.He was also one of the f o u n d e r s of the DoD Sur v i v a b i l i t y / Vu l n e r ability Inf o rm a t i o n A n a l ysis Center (SUR V I AC ) He may be reached at 703.451.3011. c o n t i n ued from page 2 1

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Aircraft Survivability Spring 1999 23 f a single key parameter had to be identified that was critical to all aspects of susceptibility reduction, that parameter would be jammer to signal (J/S), the ratio of the jamming pow e r to the signal pow e r Regardless of where the sy s t e m is operating within the electromagnetic spectrum, from radio frequency (RF) through infrared (IR) into the ultraviolet region, the most critical factor to be considered for jamming effectiveness is the J/S ratio. The higher the ratio, the more likely that the countermeasure will work. Many earlier attempts to p r o vide susceptibility protection to a platform took a "stovepipe" approach increasing the jammers p o w e r The current trend is to take a broader approach and work with both elements of the equation: the susceptibility reduction portion (the numerator) and the signature management portion (the denominator). This approach yields significantly more survivable solutions that are technically sophisticated and cost effective. U.S. helicopters first encountered IR missiles in Vietnam. It was a new and frightening experience when helicopters seemed to simply fall from the s k y Once it was learned that heat-seeking missiles were causing the problem, the solution was simple: get rid of the heat. That problem was solved by installing an exhaust div e r t e r The exhaust div e r t e r funneled the exhaust up into the rotor wash to dissipate the heat and also blocked the view of the turbine that was visible up the engine tailpipe. For that generation of missiles, this was a very simple and sophisticated solution. These missiles needed a v e r y high temperature source for acquisition and tracking. The pilot only had to remember to make pedal turns and not bank the aircraft. Banking the aircraft would expose the engines hot metal parts, pro v i d ing an easy target for the missile. This type of approach is now outdated because newer missiles h a ve an-all aspect capability. Their seekers are designed to work in an IR region that can lock on to the skin as opposed to the hot metal parts of an aircraft. H a ving learned from this experience, the next generation of aircraft included signature management in its basic design. An example of this integrated approach is the U.S. Arm y s Apache Attack Helicopter, the AH-64. Its IR suppression w a s designed as an integral part of the entire aircraft, especially the engine. When it came time to develop the active jammer for this aircraft, the job became significantly easier. Based on the Apaches radiated signature, it was estimated that a jammer with an input power of 1500 w a t t s could provide adequate countermeasures e f f e c t i ve n e s s The system developed w a s the AN/ALQ-144A. This 26.5-pound system, which consumes 1.3 KVA of total p o w e r provides protection against some of the latest generation missiles. As aircraft get larger, so does the problem of providing surviv a b i l i t y Designers h a ve to become more ingenious, or the platform will begin to suffer in regard to load-carrying capability and mission range. For example, the Arm y s Blackhawk UH-60 h e l i c o p t e r could not be suppressed to the same levels of the Apache. Consequently, a single AN/ALQ-144A would not pro v i d e adequate cov e r a g e The project leader for the jammer devised a solution that was rela t i v ely simple mechanically, yet sophisticated from an engineering aspect. Two AN/ALQ-144As were phase locked so that their jamming power could be added to p r o vide twice the capability of a single unit. This change gave more than adequate protection to the aircraft. For other aircraft, it has not been possible to develop effective suppression techThe Synergy of Susceptibility Reduction and S i g n a t u r e Management: A Question of Ener g y by Mr. Larry DeCosimo I c o n t i n ued on page 2 4

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the AN/ALQ-156 missile approach detector for protection of its Chinook. The Army developed a pulse doppler radar that detects a missiles approach and launches a flare to decoy the missile. How e ve r a d r a wback is that it is an active system that increases RF emissions from the platform. (For many applic a t i o n s the AN/ALQ-156 has been replaced by the A A R -47 passive missile warning receiv e r. ) The problem continues to this day, regardless of whether expendables or active jammers are considered. The major difference between Army and Air Force flares is in their size. Larger signature aircraft require larger flares to accomplish the same results. A r m y flares measure 1 inch x 1 inch x 8.5 inches. Comparable Air Force aircraft flares are 1 inch x 2 inches x 8.5 inches or 2 inches x 2.5 inches x 8.5 i n c h e s This increased size means that either more or significantly larger dispensers would be required to launch the same number of flares. The same problem exists for laser-based jamming. Lasers are available that can provide suppressed aircraft with J/S ratios in the 1,000s. These lightweight, 18-pound lasers can be carried by small aircraft, such as helicopters. Because of the large J/S ratios they pro v i d e generic waveforms can be used to defeat a wide range of the newer threat missiles. H o w e ve r when these same lasers are placed on aircraft having large signatures, the J/S drops precipit o u s l y as does its ability to breaklock a missile. The accuracy of the jamming waveform now becomes increasingly critical, and miss distances begin to diminish. Two approaches being pursued are to either develop larger lasers or to attempt to diminish the aircraft signature. The benefit to pursuing both approaches is that the platform will not be locked into a single approach; rather the most affordable approach can be selected. F B i o g r a p h y M r DeCosimo has 15 years experience developing surv i v ability equipment for U.S. Army platforms. This has included RF and EO systems as well as infrared c o u n t e r m e a s u r e s He is currently responsible for hardware development for the Tri-service A d v anced Threat Infrared Countermeasures/Common Missile W a r n i n g R e c e i v er program. He may be reached at 7 3 2 4 2 7 4 2 61 niques without placing an unacceptable weight and performance penalty on the aircraft. An example is the Arm y s CH-47 Chinook, which is comparable to the Marine Corps CH-46 Sea Knight. The A r m y has tried unsuccessfully to dev e l o p an engine suppressor for this aircraft. The latest attempt yielded a design that weighed 300 pounds per side and consumed more than 2 percent of the engines p o w e r Although this solution was not feasible and had to be abandoned, other experiments are under way to use different concepts to develop a viable suppressor. E v en though it has not been possible to d e v elop viable suppressors, aircraft have not been left unprotected. Other approaches needed to be employed to reach the desired J/S ratio. The Army and N a vy developed systems to protect these h e l i c o p t e r s The Navys Appr o a c h The Na v y s approach was to develop the AN/ALQ-157 infrared jammer to protect the Sea Knight. This 22 0 p o u n d system consumes 8.5 KVA of p o w e r A "negative s y n e r g i s m comes into play when these types of systems are mounted on an aircraft. Larger systems require a stronger and hea v i e r installation kit. Higher power consumption means that heavier gauge wiring must be used, which only increases the w e i g h t Higher system weight and power consumption require additional engine horsepow e r and have a negative effect on weapons payload and platform range. The Ar m y s Appr o a c h The Army took a different approach to platform s u r v i v ability by dev e l o p i n g Aircraft Survivability Spring 1999 24 c o n t i n ued from page 2 3

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Nikolaos Caravasos M r Nikolaos (Nick) Caravasos was recently honored as recipient of the American Institute of Aeronautics and Astronautics (AIAA) Survivability Award during the aw a r d s banquet at the World Aviation Congress & Exposition being held in Anaheim, California on 29 September 1998. The S u r v i v ability T e c h n i c a l Committee of the AIAA unanimously selected Mr. Carav a s o s for this y e a r s award for his contributions in the areas of design, a n a l ys i s implementation, and education, which have clearly separated him from his peers in the advancement of survivability as a design discipline. Nick has been inv o l v ed with aircraft design and survivability for over 30 years with Boeing Information, Space, and Defense Sy s t e m s Philadelphia, P e n n sy l v ania. He is recognized as an expert, nationally and internationally, on s u r v i v ability matters having worked on programs such as: Y U H 6 1A (UTTAS), HLH, RAH-66 Comanche, V 2 2 O s p r e y F-22, and JVX aircraft. He continues to do research in new materials and processes, hydrodynamic ram, and blast damage effects among others. He was previously honored as the top IR&D producer at Boeing Helicopters in 1985, 1986, 1987, and 1988. He has managed numerous A r m y, Na v y & Joint Technical Coordinating Group on Aircraft Survivability (JTCG/AS) contracts, and is currently managing two such contracts. Nick is an Associate F e l l o w of the American Institute of Aeronautics and Astronautics, a charter member of their S u r v i v ability Technical Committee (serving as chairman in 1992 and 1993), a member of the American Helicopter S o c i e t y and an industry advisor to the JTCG/AS. He has published and presented numerous articles on aircraft combat surviv a b i l i t y repairability, and crash w o r t h i n e s s He has also given several invited lectures on "Aircraft Combat Survivability", "Helicopter Design", and L i v e Fire T e s t i n g F Michael Meyers Michael Mey e r s a leader in dev e l o p i n g the survivability of the F-4, F-15 and F / A -18A/B, has been selected a Boeing Technical F e l l o w, an award to recognize and promote technical excellence. A t Boeing, for merly McDonnell Douglas A e r o s p a c e Mike has been Vulnerability Team Leader for the F/A-18E/F since 1991. His responsibilities include vulnerability analy s i s design interface, l i v e fire testing, and trade study ev a l u a t i o n s From the mid-1970s into the mid-1980s, Mike led evaluations of the F/A-18 Hornet surv i v ability design. Studies included signature reduction analy s e s countermeasure effectiveness ev a l u a t i o n s and a laser vulnerability and hardening analy s i s E a r l i e r Mike was responsible for the F-15 vuln e r a b i l i t y / s u r v i v ability program from conceptual design to production. During this time, he formulated the vulnerability estimating methodology and the associated survivability modeling techniques used for design ev a l u a t i o n s Mike earned his B.S. in electrical engineering from Washington University in 1960 and worked on design and evaluation of adv a n c e d electronic equipment for the Radio Phy s i c s Laboratory at the Naval Research Laboratories i n Washington, DC, before joining McDonnell Aircraft Company in 1962. F Aircraft Survivability Spring 1999 25 Two Long-Time JTCG/AS Industry Advisors Receive Special Honors by Mr. Joseph P. Jolley

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The Air Force Research Laboratory (AFRL), under contract with the Boeing Company, has i n v estigated the use of pulsed injection to trigger self-sustained mixing of jet exhaust plumes. The system uses a small amount of engine bleed pulsed at key frequencies to destabilize the p l u m e This results in a periodic flapping of the plume that entrains ambient air and enhances the mixing effectiveness of the system. Such a system, termed A c t i v e Core Exhaust (A C E ) Control System was recently tested in a full-scale engine ground test with the ACE system installed on a Pratt and Whitney JT8D-15A at Pratt and W h i t n e y s C-11 commercial test facility in W e s t Palm Beach, Florida, as shown in Figure 1. The ACE JT8D test configuration was dev e l oped to ensure maximum flexibility in v a r y i n g injection flow rate, frequency, and v e l o c i t y and in injector slot size, orientation, and geometry. Injection flow was provided via the 8 t h and 13 t h stage bleed ports, and a fluidic actuator v a l v e was developed to provide injected pulses at a wide variety of frequencies. Injection slots, major concern for many military h e a vy-lift cargo and transport aircraft is the undesirable effects hot exhaust gases have at various points in the flight regime on structural integrity, human effectiv e n e s s and aircraft surviva b i l i t y During powered descent and takeoff, hot gas impingement can damage trailing edge flaps. During off-load o p e r a t i o n s ambient temperatures at the rear of the aircraft can rise to unsafe levels for sustained manual labor. In all phases of the flight, the hot plume and engine components increase an aircrafts vulnerability to heat seeking miss i l e s Techniques to ov e r c o m e each of these problems are av a i l a b l e but a balanced solution is often difficult to attain. Split flap designs and hightemperature titanium alloys can help maintain an aircrafts structural integrity; how e ve r split flaps generate less lift than single flap designs, and titanium alloys are heavier and more costly than aluminum a l l o ys. A core thrust reverser can be used to control the ambient temperature at the rear of the aircraft during off-load operations by deflecting the hot gases away from personnel. How e ve r the hot gas deflection to other airframe structures may require additional thermal protection. A core reverser also adds weight, complexity, and correspondingly higher maintenance to an aircraft and m a y preclude the use of a plug nozzle or obscuration device. Aircraft Survivability Spring 1999 26 Active Core Exhaust Control Systems by Mr. Clarence F. Chenault and D r Yvette S. W e b e r F i g u r e 1. Full-Scale Low-Bypass Ratio Aircraft Engine A

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which were positioned 180 degrees opposite each other, had injection characteristics v a r i e d with removable "jet blocks" to change the slot s i z e s Two injector positions, fore and aft, near the nozzle exit could evaluate the effectiv e n e s s of the injection when it was applied upstream of the nozzle exit plane. In addition, the nozzle could rotate 90 degrees about the longitudinal axis to obtain data for flapping in the horizontal and vertical planes. Figure 2 shows the injectors mounted in a horizontal position at the upstream nozzle injector port. The ACE JT8D test hardware was designed for flexibility under considerable cost constraints. Optimized, flightw o r t h y configurations are the subject of f o l l o w-on activities. The test program demonstrated strong mixing under most of the test c o n d i t i o n s Self-sustained exhaust plume mixing resulted in a 50 percent temperature reduction along the exhaust plume centerline in as few as five nozzle diameters downstream of the exhaust exit plane. The test validated that mixing e f f e c t i v eness improves as the injection is placed closer to the exit plane of the n o z z l e Figures 3 and 4 illustrate dramatically the efficiency of the flapping mechanism in reducing plume temperatures. Figure 3 contains a computationally d e r i v ed image of the undisturbed plume and a cross-sectional temperature field d e r i v ed from experimental rake data 5 diameters downstream of the nozzle exit. Figure 4 shows a similar set of images at a snapshot in time with the ACE system turned on. This figure illustrates the resulting flapping motion and temperature reduction of the plume. Also evident is the alteration of the plume shape. The plume disperses in the Aircraft Survivability Spring 1999 27 F i g u r e 2. ACE Control Installed F i g u r e 3. Steady-State CFD Results for Low Bypass Ratio Engine With ACE off at Off-Load Conditions c o n t i n ued on page 3 0

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vulnerability reduction features will be contingent on aircraft type and mission. After welcoming remarks and an overview of the MSIC organization and mission by its commander, Col John Wigington, three excellent presentations by key OSD sponsors followed. Dr. P a t r i c i a S a n d e r s OUSD(A&T)DTSE&E, provided the keynote address. Mr. Ron Mutzelburg, O U S D ( A & T ) D S & T S ( A W) and sponsor of the w o r k shop, provided the background and basis for concern with the vulnerability of aircraft to MANP A D S g i v en the current emphasis on stealth and low o b s e r va b l e s And Mr. Jim OBry o n O S D / D D OT & E / L F T addressed the MANP A D S threat from the operational test and live fire test pers p e c t i v e. A highlight of the workshop was hearing the combat experiences of three pilots who encountered the MANPADS threat during Desert Storm. During the workshop, speakers from gov e r n m e n t and industry described the proliferation and lethality of MANPADS, susceptibility reduction limitat i o n s and the need to incorporate vulnerability reduction into aircraft designs. In addition, three break-out sessions concentrated on specific subjects including vulnerability reduction techniques, assessment methodologies, and test facility capabili t i e s The Results Preliminary findings from the workshop are listed below. 1 M A N P ADS are a lethal threat, proliferated worldwide in large numbers. This shoulderlaunched weapon system is a serious threat to all types of aircraft. 2. A MANPADS hit does not necessarily equate to a kill. he National MANPADS W o r k s h o p was held 15-17 December 1998 at the Sparkman Center, R e d s t o n e Arsenal, Alabama. The classified w o r k s h o p brought together over one hundred experts for a technical interchange on the issue of h o w to make aircraft less vulnerable to the M A N P ADS (Man Portable Air Defense S y stem) threat. Under the sponsorship of O U S D ( A & T ) S & T S ( A W), the workshop w a s co-hosted by the Joint T e c h n i c a l Coordinating Group on Aircraft S u r v i v ability (JTCG/AS) and the Defense Intelligence Agencys Missile and Space Intelligence Center (MSIC). W o r k s h o p o b j e c t i v es were to: Gather and exchange information concerning aircraft-MANP A D S e n c o u n t e r s Compile a roadmap of current MANPADS vulnerability reduction activit i e s and Identify vulnerability reduction solutions effective against MANP A D S t h r e a t s The results of this workshop are contributing to a one year study, now underway, with similar objectiv e s The study is scheduled to be completed June 99. Avoiding the threat using susceptibility reduction techniques such as signature reduction, countermeasures, tactics, etc are recognized as the first line of defense against the MANPADS. How e ve r vulnerability reduction techniques also pro v i d e needed protection and constitute a second line of defense which contributes to the overall survivability of the aircraft. The proper mix of susceptibility reduction and Aircraft Survivability Spring 1999 28 National M A N PA D S Workshop: A Vulnerability Perspective by Mr. Joseph P. Jolley T

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3. There is a need for MANPADS threat characterization and test databases to support dev e l o p ment of improved assessment methodologies and new vulnerability reduction techniques 4. Models have limited capability to predict surface-to-air missile hit locations. Specific i m p r o vements are needed in IR signature models and threat-in-the-loop softw a r e Modeling requirements need to drive tests performed and data collected. 5. Current MANPADS test facilities are generally adequate and no major investments are required. Exceptions relate to shotline control and handling large transport-sized aircraft or c o m p o n e n t s S u m m a r y M A N P ADS have become a highly proliferated threat and are lethal against all air platforms. Vulnerability reduction techniques offer a second line of defense after signature reduction, countermeasures and other threat avoidance techniques. Aircraft survivability is optimized by designing in the right combination of susceptibility and vulnerability reduction features, based on the aircraft type and mission, not only for the MANPADS threat, but all types of threats. Workshop proceedings are being published in t w o v o l u m e s Volume One is unclassified and contains the agenda, a list of attendees, and the unclassified presentations. Volume Two is classified S E C R E T and contains the classified presentations. A c o p y of the proceedings can be obtained by contacting SURVIAC at 937.255.4840 or DSN 785.4840. F B i o g r a p h y M r .J o l l e y is the Deputy Director of the JTCG/AS.He holds a B.S. d e g ree in A e r ospace Eng i n e e r ing from the U.of Florida and an MA degree in Public A d m i n i s t r ation from Wichita State U n i ve rs i t y P r ior to coming to the Central Office in 1990, M r J o l l e y served for six y e a r s in the Propulsion and Pow e r Division of the Naval Air Systems Command.He may be reached at 703-607-3509,ext 14. Aircraft Survivability Spring 1999 29 established and chaired the DOT&E TriService Coordinating Group for this area. Hugh retired from civil service in 1988. Two weeks after retirement, he joined ASI S y stems International (ASI-SI) as a vice president responsible for all ASI-SI Navy programs and later became Executive Vice President. ASI-SI was acquired by SRS Technologies in January 1998. Hugh is the Vice President of ASI-SI, a wholly owned subs i d i a r y He has been directly inv o l v ed in Live Fire T&E for the HARM Improved W a r h e a d Program and the A d v anced Bomb F a m i l y risk management planning and systems engineering for weapons development programs. In addition to his corporate responsibilities, he supports the Joint Electronic Combat test using Simulation (JECSIM) Joint Test and E v aluation (JT&E) Program. Hugh has received a number of aw a r d s and citations including the follo w i n g : an award for outstanding support to the JTCG/ME and the Army from the chairman of the JT C G / M E Certificate of Merit from the Joint Logistics Commanders for outstanding service in joint service activities N a vy Superior Civilian Service Aw a r d in recognition of contributions and support to the Navy and to the defense of the Nation from the C o m m a n d e r Space and Nav a l Warfare Systems Command numerous Naval Weapons Center aw a r d s Hugh and his wife Sondra, whom he married in October 1956, have raised three d a u g h t e r s Sheri, Cathi, and Cindi, and one son, Jeff. When Hugh is not working, he and Sondra spend time with their children and s e v en grandchildren and visit their second home (the cabin) located at an altitude of 6000 ft. in the Sequoia National Forest, 90 minutes driving time from home F c o n t i n ued from page 1 1 Pioneers of Sur v i v a b i l i t y

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Aircraft Survivability Spring 1999 30 direction of the injection, forming an oval rather than a circular cross section. The redistribution of temperature and corresponding pressure loads may have some beneficial effect on the aerodynamic performance of a blown flap system. Although exhaust plume mixing is not a new idea, it has always been accomplished with intrusive devices that degrade engine performance over the entire flight regime. In contrast, the A C E Control System can be switched on and off as needed with no thrust penalty in the off position. The system has the a d v antages of reducing hot gas impingement on aircraft surfaces during specific c o n t i n ued from page 2 7 Active Core Exhaust Control Systems portions of the flight envelope and in mitigating a potentially hazardous environment for ground personnel operating in exhaust w a s h e d areas of an aircraft without resorting to a core thrust reverser solution. F B i o g r a p h i e s Captain Clarence Chenault graduated from the Air F o rc e Institute of T e c h n o l o g y with his Ph.D.in 1998 and M a s t e r s in 1993,both in A e r onautical Eng i n e e ri n g H e e a r ned his B.S.in A e r ospace Eng i n e e r ing from the U n i ve r sity of Missouri-Rolla in 1990.Capt Chenault has p e r fo r med basic r e s e a r ch in the application of n u m e r ical simulation of high speed injection f l ow f ields using s e c o n d o r der Reynolds stress turbulence models. M o r e r e c e n t l y,he has w o r ked in the Air Frame Propulsion and Weapons Integration Branch of the Air F o r ce Resear c h L ab o ra t o r y as the senior military computational f l u i d dynamics analyst and A i r f r ame Integration Engineer f o r A d v anced Exhaust Systems.Captain Chenault may be reached at 937.255.6207. D r Y v ette Weber graduated with her Ph.D. f r om the U n i ve r sity of Maryland in 1994.She has been employ e d by the US Air F o r ce Research La b o ra t o r y (f o rm e r ly W r ight La b o ra t o r y) since 1992. Y v ette has perf o rm e d basic r e s e a r ch in high temper a t u r e gas dynamics and the application of computational fluid dynamics to computational electr o m a g n e t i c s M o r e r e c e n t l y,she has w o r ked in the Air Frame Propulsion and W e a p o n s I n t e g ration Branch as the technical lead for A d va n c e d Exhaust Systems.She curr e n t l y manages Air F o r ce techn o l o g y pr o g rams related to fluidic jet control for mixing, a r ea control and thrust v e c t o ri n g the objectives being to p r ovide lightw e i g h t a f f o rd a ble and highly sur v i v ab l e mission critical perf o r mance for military air c ra f t .Y ve t t e has also r e c e n t l y been appointed Chief of the Focus A re a on Uninhabited Air V e h i c les for AFRL Air V e h i cl e D i re c t o ra t e .D r .Weber may be reached at 937.255.6207. F i g u r e 4. Snapshot of Unsteady CFD Results for Low Bypass Ratio Engine With ACE on at Of f Load Conditions

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Aircraft Survivability Spring 1999 31 M a r ch 29-April 1, 1999, Monter e y CA G r ound Vehicle Sur v i v a b i l i t y Contact: 703.522.1820, iclick@ndia.org April 11-15, 1999, San Diego, CA High Per f o r mance Computing Contact: Dr. Adrien Tetner 619.277.3888, tetner@anl.gov April 22-23, 1999, London 1999 Combat Aircraft Survivability Confer e n c e Contact: Steve Philpott hsauk@aol.com, 44.171.413.0936 May 11-13, 1999, Kelly AFB, TX 1999 HAVE For u m Contact: Capt. Wayne Floyd 937.255.0276, http://www a o c h q o r g June 15-18, 1999, Colorado Springs, CO DDEAF-CRAB Model Users Gr o u p Contact: Geri Bowling 937.255.4840, DSN 785, gbowling@sur v i a c f l i g h t w p a f b a f m i l November 16-18, 1999, Monter e y CA A i r craft Sur v i v a b i l i t y Contact: 703.522.1820, jhylan@ndia.org Information for inclusion in the Calendar of Events may be sent to: SURVIAC W ashington Satellite Office Attn: Christina McNemar 3190 Fairview Park Drive, 9 th Floor Falls Church, VA 22042 PHONE: 703.289.5464 F AX: 703.289. 5 4 6 7 Calendar MAR APR MA Y JUN NOV

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