Aircraft survivability

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Aircraft survivability
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Began with 1998.

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University of Florida
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CREW AND PASSENGER SURVIVABILITYTransport Rotorcraft Airframe Crash Testbed (TRACT) Twopage 6Survivable. Safe. Low 112014 Threat Weapons & Effects Trainingpage 14Evaluating Long-Term Impact of Nonfatal Injuriespage 20


TABLE OF CONTENTS4 NEWS NOTESby Dennis Lindell5 JCAT CORNERby Greg Fuchs6 TRANSPORT ROTORCRAFT AIRFRAME CRASH TESTBED (TRACT) TWOby Frank ColucciA follow-on helicopter drop test at the National Aeronautics and Aerospace Administration (NASA) Research Center in Langley, VA, will take another close look at cabin crash behaviors and crashworthiness innovations.11 SURVIVABLE. SAFE. LOW Penny T. Willard and Richard A. Moyers Survivable. Safe. Low risk. For anyone who has ridden in an airplane, a primary human consideration for being a passenger relates to any and each of those words. Every passenger expects the aircraft to be survivable, safe, and relatively risk free. 14 2014 THREAT WEAPON AND EFFECTS TRAININGby Scott Quackenbush, LCDR The 2014 Threat Weapon and Effects Training (TWET) took place on Hurlburt Field, Okaloosa County, FL, and at Eglin Air Force Base (AFB), Fort Walton Beach, FL, 2224 April 2014. This annual training is presented by the Joint Combat Assessment Team (JCAT), sponsored by the Joint Aircraft Survivability Program Ofce. 16 AIRCRAFT SURVIVABILITY RATINGby Jordan Kaye, Mark E. Robeson, and Nathaniel BordickTo demonstrate an integrated platform solution that exemplies both operational durability and total survivability without deleterious effect on mission performance, the US Armys Aviation Development DirectorateAviation Applied Technology Directorate (ADDAATD) and Sikorsky are executing the Combat Tempered Platform Demonstration (CTPD). CTPD integrates and demonstrates enhanced aircraft and crew/occupant protection, improved battleeld durability, and reduced threat vulnerability. The integrated approach to vulnerability reduction enables the survivability requirements for current and future aircraft to be realized more efciently.


20 EVALUATING LONG-TERM IMPACT OF NONFATAL INJURIESby Latrice HallCurrently, personnel survivability studies primarily focus on the Soldier surviving injuries in combat and not necessarily on how nonfatal injuries affect the ability to perform everyday functions after treatment and recovery. Advancements in protective equipment and protection strategies, which are a result of these survivability studies, have greatly reduced the number of killed in action and have increased the number of wounded in action. Because of the increase in survivability, there is a need to characterize the effect of nonfatal injuries on long-term quality of life. A recently published metric called predicted Functional Capacity Index (pFCI) quanties long-term functional limitations one year post injury. 23 EXPANDING AIRCRAFT COMBAT SURVIVABILITY TO INCLUDE FORCE PROTECTIONby Christopher Adams The U.S. military Services design aircraft to operate in both normal and combat ight environments. The normal ight environment includes day-to-day operations conducting routine missions such as training and humanitarian assistance, with the usual takeoffs, transits, and landings. It also includes the natural hostile environment with its brownouts, severe turbulence, lightning strikes, bird strikes, midair collisions, and crashes. The combat (or man-made hostile) ight environment includes traditional combat with enemy forces using surface-to-air and air-to-air guns and missiles, as well as on-board terrorist threats, such as suicide bombers and bombs in suitcases.


AS Journal 14 / FALL h ttp:// 4 RON KETCHAM RETIRES!Ronald L. Ketcham, chairman of the Joint Aircraft Survivability Program (JASP) Survivability Assessment Subgroup, retired from civil service on 30 May 2014, after 30-plus years at China Lake. Ron began his career as a junior professional at the Naval Weapons Center in September 1982 working as an industrial engineer for system safety; after his JP tours he moved permanently to the Anti-Air Warfare Branch in the Weapons Planning Group ( aka Code 12) as an operations research analyst. While there, he worked on a number of projects, including: F-14 Tomcat Tactics, EA-6B EW Software Analysis, Sidewinder, RF Fire Control Fusion Algorithms, Joint Direct Attack Munition, and the Airborne High Energy Laser Weapon System. He also developed a model called SPADE (Simulated Point Area Defense Engagements) to study eet defense effectiveness against cruise missiles. It was while working on SPADE that he began to interact off and on throughout his career at Code 12 with the Combat Survivability Division. Around 1985 Ron decided he wanted to leave the desert and see the world, so he went to work for Lockheed skunkworks at the Burbank Airport; while at Lockheed he did modeling, simulation, and analysis for multiple platforms. But, apparently missing the wide-open spaces, he returned to China Lake after a couple of years to work in Code 12s Strike Warfare Branch. From the desert he soon was sent off to do two tours in Washington, DC: one to support the A-12 program (we wont blame you for that one, Ron), and the second at Space and Naval Warfare Systems Command to complete a tour requirement of the Senior Executive Management Development Program. After being back at China Lake for a year Ron took over project management and development of the Analysts Workbench, a tool for analyzing weapons systems in conceptual development; he was able to see it successfully applied to a Carrier Load-Out Study. In 1997, Dave Hall called Ron and asked if he would work on a detail with the Survivability Division as a member of the Joint Accreditation Support Activity (JASA). He accepted and shortly became the accreditation lead for the Joint Strike Fighter (JSF) program. He also supported other accreditation projects, including the Coast Guard Deepwater program. And as a member of JASA, Ron chaired the second M&S Credibility Workshop in Reno, NV, in 2001. Ron became the Branch Head of the Naval Air Warfare Center Weapons Division (NAWCWD) Survivability Assessment Branch in 2001, supporting a variety of Navy and Marine Corps aircraft and weapons programs including F/A-18, V-22, Tomahawk, and others. That same year Ron also took over as chair of the JASP Survivability Assessment subgroup and became a member of the executive board of the National Defense Industrial Association Combat Survivability Division (CSD). Ron chaired the 2011 CSD Aircraft Survivability Conference in Monterey, CA: thanks to Ron, this was the rst year that the conference had a golf tournament, and Ron took up golf just so he could participate in the tournament! Since then he has become an avid golfer and plans to continue playing and improving his game in retirement. In recent years, Ron has applied his modeling, simulation, and accreditation expertise to support the Joint Technical Coordinating Group for Munitions Effectiveness Endgame Manager tool, serving as chair of the Methodology Review committee. He recently served as product quality manager for the Joint Anti A ir Combat Effectiveness/Joint Anti-Air Model/Suite of Anti-Air KillChain Models and Data program. Upon his retirement, Ron was presented the Navy Meritorious Civilian Service Award by Scott ONeil, the NAWCWD Executive Director and Director of Research and Engineering (Code 4.0); the award was signed by Rear Adm. Mike Moran, NAWCWD Commander. Rons citation reads, in part, For signicant technical and leadership achievements in the development and advancement of Modeling & Simulation capabilities for the evaluation of Mission Effectiveness and overall Combat Survivability assessments . Your Figure 1 Scott ONeil, SES, NAWCWD Executive Director (left), congratulates Ron on his Meritorious Civilian Service Award.


5 h ttp:// A S Journal 14 / FALL unequalled talents as a modeling and simulation expert, as well as your innate ability to formulate requirements for complex modeling systems, have been vital to the unparalleled success of the Survivability Assessment Branch. You are an unselsh and effective mentor, a visionary leader, and a highly valued member of the NAWCWD team. Your many noteworthy achievements and sustained superior performance are in keeping with the highest traditions of the Naval Service . . Ron is retiring to Las Vegas and will be living on the 13th fairway of the Los Prados Golf Course. JCAT CORNERby Greg Fuchs The Joint Combat Assessment Team (JCAT) has seen a busy year. This past spring saw another JCAT assessor training cycle complete, resulting in over 15 new assessors. The 2014 Threat Weapon and Effects Training (TWET) made a return after a years absence, giving JCAT assessors the ability to interact with professionals from across the aircraft survivability industry. The future will be a challenge as the JCAT footprint changes over the next year. JCATs annual assessor training was completed in three phases: a week at Fort Rucker, AL, in February (phase I); a week at the Naval Air Warfare Center, China Lake, CA, in March (phase II); and TWET in April (phase III). In addition to the JCAT assessors, the Army hosted Aviation Mission Survivability Ofcers (AMSO, formally known as TACOPS ofcers) from Combat Aviation Brigades (CAB) across the Army during phase I. These warrant ofcers attend the entire week of phase I to prepare them to collect the raw data and begin the aircraft combat damage reporting (ACDR) process. As the frontline survivability representative for their units, JCAT does and will continue to work with these pilots to collect raw data to be used in JCAT combat damage assessments. TWET made its return this year after it was canceled in 2013 because of the sequestration. This culminating event in the training of new JCAT assessors provides the new forensics ofcers critical insight into aircraft survivability by receiving classes and briengs from military and industry experts across many disciplines. Hosted by the Navy JCAT detachment and held at Hurlburt Field, Okaloosa County, FL, and at Eglin Air Force Base (AFB), Fort Walton Beach,FL, this years theme focused on threats in Asia. Attendees were able to see the effects of a directional style warhead against one of DODs rotary-wing aircraft after a warhead demonstration. Next years TWET will be held at Hurlburt Field and at Eglin AFB from 2830 April 2015. The Armys Aviation Survivability Development and Tactics (ASDAT) Team will host this event, which will focus on threats to aircraft 20152020. JCATs footprint will return to a continen tal-US-only system as US involvement draws to a close in Afghanistan. This ends a continuous presence that began August 2004 and has been stalwartly supported by members of the Navy, Marine Corps, and Air Force aircraft survivability professionals. JCATs forward deployed presence has provided commanders, and their ying Soldiers, valuable information regarding the threat faced by aircrews in Iraq and Afghanistan. With this forward-deployed presence coming to a close, JCAT elements must now posture to rapidly deploy assessors around the world as the ASDAT Team has done since 2003. This is only the beginning of the chal lenges JCAT will face as the military withdraws from Afghanistan and the entire military contracts. As with any military organization, personnel changes have been a frequent occurrence. The ASDAT Team said goodbye to a long-time and valued member. Ms. Laurie Mitchell, the intelligence specialist for the team, has been accepted to a law school in Kentucky. The team bade her farewell in July; her knowledge, expertise, professionalism, and daily friendship will be missed. Chief Warrant Ofcer 4 Robert Olson will be transferred to the Combat Aviation Brigade in the Republic of Korea. Finally, Chief Warrant Ofcer 4 Wayne Grimes has announced his retirement and will depart the team this winter for a spring retirement.




7 h ttp:// A S Journal 14 / FALL A second drop test of the Transport Rotorcraft Airframe Crash Testbed (TRACT) is scheduled for this September in the Landing and Impact Research (LAND IR) facility at the NASA Research Center in Langley, VA. The rst TRACT crash of an instrumented CH-46E helicopter full of anthropomorphic dummies last August gave NASA, Army, Navy, the Federal Aviation Administration (FAA), and industry researchers baseline data to correlate with photogrammetric tools. TRACT lead test engineer Martin Annett explains, I would say the biggest thing we got out of it was the high-speed video and being able to fuse that video with the responses of the crash test dummies. We were able to coordinate when the peak loads occurred with the timing of that video. With the same tools, the next TRACT test will evaluate crushable oors, active seat restraints, and other crash-attenuating technologies. Generally speaking, everybody who participated before will be participating again with their experiments. TRACT experiments are not tied to any one rotorcraft design effort, but they may help designers of some joint-service Future Vertical Lift (FVL) helicopter or tilt rotor better protect aircrews and passengers. Unlike todays crashworthy helicopters optimized for vertical impact from a hover, FVL rotorcraft will need full-spectrum crashworthiness. Annett explained, If youre going to design things like FVL concepts, how do you capture the aspects you want? . Impact velocity, terrainall that will feed forward into how you design the airframe. TRACT data may shape future crashworthiness specications like the MIL Standard 1290 rst applied to the UH-60 Black Hawk in the 1970s. I think the airframes that came out of there are in very good shapelike the Apache and the 60, observed Annett. Were not looking to redo requirements; were looking more to understand the overall physics of whats happening inside. Dynamic crash data may also help dene active crew restraints and other safety systems inside the vehicle. Annett noted, We have a velocity and attitude. What we dont always know is what will happen to the occupants. Sitting, standing, and litter-reclining occupants in the rst TRACT crash included 13 instrumented crash test dummies and two uninstrumented mannequins. The LAND IR pendulum at Langley swung the retired Marine Phrog from 30 feet and severed suspension cables just before impact. The helicopter hulk hit the dirt track at 26 feet per second (fps) vertically and 35 fps horizontallycalculated survivable crash parameters. Annett observed, People said it didnt look that bad on the outside; then you see what happened inside. Cameras, accelerom eters, and a video game motion tracker all captured crash data still being analyzed for upcoming experiments. The second TRACT airframe will, for example, replace aluminum shear-webs with energy-absorbing crushable composite oors. The idea for that is we have some NASA concepts for shear webs in the suboor, said Annett. We would isolate out different frame sections. That allows us to put different concepts in different frames. NASA Langley technicians are fabricating several carbon-aramid oor structures. One has alternating inverted cones instead of sine-wave beams to begin the crush from either top or bottom. Another concept comes from the Deutsches Zentrum fr Luftund Raumfahrt, or DLR, the German space agency, working with manufacturers in Australia and New Zealand. Theres been some work going by Frank Colucci A follow-on helicopter drop test at the National Aeronautics and Aerospace Administration (NASA) Research Center in Langley, VA, will take another close look at cabin crash behaviors and crashworthiness innovations. Figure 1. The NASA LAND IR facility dropped the rst TRACT in August to collect baseline data for another crash in 2014. (NASA)


AS Journal 14 / FALL h ttp:// 8 on outside the US in composite crashworthiness, said Annett. I proposed we put their design in under the oor.CONTROLLED CRASHESTRACT is part of the Fundamental Aeronautics Program Rotary Wing Project of the NASA Aeronautics Research Mission Directorate. Crash conditions inside the rst CH-46 were also of interest to the US Army Aeromedical Research Laboratory (USAARL), the Naval Air Systems Command (NAVAIR) Crashworthy System Branch, the FAA Civil Aeromedical Institute (CAMI), and Cobham Life Support. The Naval Air Depot at Cherry Point, NC, gave NASA researchers the crash test article. The 46 was available, and there was something in the size of the airframe, said Annett. The all-metal CH-46 nevertheless predated modern crashwor thiness standards. Were just interested in the overall system aspect . The ultimate objective was to understand what would happen if we switched something that was metallic to compositewould it be better? Would it be worse? Stripped of engines, transmissions, and rotors, the TRACT airframe was painted white with 8,000 black dots on one side to support full-eld photogrammetry. LAND IR engineers now use the video measurement technology on all of their tests to capture uncorrupted data. Annett noted, We have historically used strain gauges. They work relatively OK for metallic structures. Its not as well understood how you would bond to a composite structure. Two Phantom calibrated cameras provided high-speed imagery processed by Aramis motion analysis software able to track individual dots and map struc tural deformation in six degrees of freedom. We can identify hot spots on the airframestuff thats deforming out-of-plane or in-plane, explained Annett. We can not only get individual time histories of those dots; we can plot the temporal response of the deection. Umbilical cables carried signals to and from the instrumented airframe prior to the drop, but pendulum pyrotechnics ruled out wireless telemetry and led engineers to record crash data on the aircraft. Ruggedized solid-state recorders from the Diversied Technical Systems, Inc. (DTS) and Kistler collected over 340 channels of data. Annett observed, I think that was one of the bigger technical leapsbeing able to instrument that much on-board and record at the time of impact. The second TRACT test will use the same measurement technology with modica tions. Were going to add more cameras this time, said Annett. Langley techni cians have also tested a polycarbonate oor in a cabin section from the rst helicopter. One of the things we will hopefully do is develop a oor thats transparent so we can shoot down into the suboor. INTERIOR INSTRUMENTATIONUSAARL researchers at Fort Rucker, AL, continue to analyze data from the rst TRACT crash and plan to participate in the second. The laboratory has ongoing efforts to improve medevac equipment in Army helicopters and used the rst TRACT crash to collect baseline dynamic Figure 2. The CH-46E was painted with a polka dot pattern for photogrammetry measurements of airframe deformation. (NASA)


9 h ttp:// A S Journal 14 / FALLresponse data on existing patient litterstwo from the Army and one from the Marine Corpsriding a three-tier Marine CH-46 litter support system. (Army CH-47 stanchions stack litters four high.) According to USAARL research mechanical engineer Joe McEntire, This test was not intended to evaluate emerging or developmental hardware, but to increase understanding of existing litter equipment performance. Structural standards for helicopter litter stanchions are old, and McEntire noted, The standards have not been upgraded in terms of crashworthiness the way the seats have been. Existing UH-60/ HH-60/CH-47 litter specications are also based on static rather than dynamic loads. The rst TRACT test put loaded litters in a dynamic crash environment. Our objective is to develop recommenda tions for dynamic loading conditions and to conduct additional studies to assess other performance metrics and occupant injury risks. USAARL lled the middle of the litter stack with a Hybrid III automotive crash test dummy instrumented with load cells at the head, neck, chest, spine, and pelvis. Two uninstrumented dummies above and below provided representative occupant masses to put realistic loads on the litter system. The support system was also instrumented with triaxial accelerometers on each of the four hooks carrying the middle litter. Recorded imagery of the rst crash was revealing. If you look at the video, it appears to be pretty benign, but the internal video reveals its pretty harsh for most occupants with things collapsing and components breaking, said McEntire. Our intent is to use some of this data weve collected to better understand what loads are required on the litter system. He added, Thats a structural design component. The other half well be looking at is the forces and accelerations applied to the patient in the litter and looking at those to establish injury criteria to see if theyre appropriate . Many criteria are set for automotive car crash testing in a forward impact. USAARL may use either modern HH-60M or developmental litter concepts in the second TRACT crash. While Army researchers focused on litters in a crash, the FAA CAMI in Oklahoma City, OK, was interested in side-facing cabin seats and occupants. FAA Mid-States Public Affairs Manager Lynn Lunsford reported that the crush characteristics of the rst TRACT fuselage produced loads signicantly different from the idealized loads used in laboratory tests to qualify crashworthy seats. Common automotive crash test dummies have heads and necks tuned for front and rear impacts. European side-impact dummies (EuroSIDs) are tailored to the kinematics of side-facing loads. CAMI researchers put a hybrid dummya EuroSID head and neck on a Hybrid III torsonext to a regular Hybrid III dummy in side-by-side energyabsorbing seats. In the rst TRACT crash, both side-facing seats stroked down and reduced lumbar spine loads as intended. All parameters measured by the FAA dummy were conrmed well below the injury limits. For the next TRACT crash, the FAA experiment will remain unchanged so that the effect of the added energy absorption of composite fuselage structures can be compared to the baseline data. According to Lunsford, Results from the test series will help us determine if revisions are necessary to current side-facing seat testing standards in order to ensure an equivalent level of safety when compared to foreor aft-facing crashworthy seats. Up in the cockpit, Cobham Life Support outtted the left-seat copilot dummy with the pretensioning aircrew restraint system (PARS). This active restraint uses a pyrotechnic gas generator to tension the dummys shoulder harness and tighten the harness inertia reel on impact. Cobham PARS engineer Tony Ollive explained, By pretensioning, it keeps the occupant sitting in the seat more correctly than they would be without it and at the back of the seat. In that position, you can take full advantage of the protection the [stroking] seat provides. Figure 3. Instrumented crash test dummies provided insight into the TRACT crash behaviors, including the effects on litter patients and occupants of side-facing seats. (NASA)


AS Journal 14 / FALL h ttp:// 10 Cobham engineers had tried the active restraint on xed seats, but the NASA event provided the rst ight test. The right-seat dummy was strapped into a conventional MA-16 inertial reel. We were doing a direct comparison between the left-hand side and right-hand side with the same seat, harness, and dummy with and without PARS. NAVAIR sponsored the original PARS Small Business Innovative Research and provided the stroking seats and dummies for the rst TRACT crash. The PARS in the rst test was bolted to the back of the copilot seat and triggered by a contact switch when the helicopter hit the ground rather than by the intended G-sensor. We were aiming for the simplest test we could do, notes Ollive. We werent particularly interested in testing the G-switch. We really wanted to test the pretensioner. He adds, The system worked as it expected it to. There is evidence of reduced head, chest, and neck motion in the dummy . We did a very simple testwe tied a string around the dummys neck. The rst TRACT crash gave Cobham engineers data regarding the forces and moments on the head, neck and chest of the dummies. High-speed video corre lated that data with events in the cockpit. The most enlightening aspect of TRACT 1 was the ability to watch the interaction of the whole system, said John Hintenach, key campaigns director at Cobham Mission Systems Division. When we saw the numeric results coupled with the relationship between the restraints, the seat, and the equip ment the crewmember was wearing, it was truly insightful, Hinternach added, Most importantly, we received conrma tion that the PARS system reduced the injury sustained by the crewmembers. TRACT 2 will test the integrated PARS subsystem, including crash-sensing electronics. The LAND IR pendulum previously crashed the Bell YAH-63 Advanced Attack Helicopter, the Bell D292 and Sikorsky S-75 composite airframes, and a Boeing MD500 with external crash attenuator. Saved from planned demoli tion, the onetime lunar landing training facility has been reconditioned and modernized with a larger bridge to drop 32-ton loads and a basin for water impact testing. NASA Langley engineers have photogrammetry technology for crash tests on dirt or concrete, and Martin Annett said, Were working on being able to look clearly underwater and do the same kind of tracking. Figure 4. The Cobham PARS installed on the copilots seat alone gave researchers comparative data on crash movements with and without an active restraint system. (NASA via Cobham Life Support)


11 h ttp:// A S Journal 14 / FALL by Penny T. Willard and Richard A. MoyersSurvivable. Safe. Low risk. For anyone who has ridden in an airplane, a primary human consideration for being a passenger relates to any and each of those words. Every passenger expects the aircraft to be survivable, safe, and relatively risk free.SURVIVABLE. SAFE. LOW RISK. The challenge for military aircraft is that the operational environment the plane is being exposed to antagonizes and works against survivability. The plane is more prone to being engaged with small arms re, high-explosive ordnance, and a broad range of threats in between. Yet a common and primary consideration still remains to make that aircraft surviv ablea challenge that for the rst time was explicitly a part of the key perfor mance parameters (KPPs) in designing the Joint Cargo Aircraft (JCA) to meet wartime requirements. In 20092010, the US Army Research Laboratory (ARL) collaborated with the US Aeronautical System Center Engineering Directorate, Combat Effectiveness and Vulnerability Branch (ASC/ENDA) to conduct a ballistic vulnerability analysis on the JCA. Two analyses were conducted to assess the crew vulnerability and system-level vulnerability, which was comprised of both the crew and troops ying as passengers. In the initial stages of modeling, legacy methods were used that roughly approximated the contributions of the crew to the overall architecture of the plane. The ComputerMan/pilot survey (CMPS) technique uses the high-resolu tion ComputerMan limb-state-to-performance model combined with the pilot survey perfor mance results to provide levels of dysfunction using the SperazzaKokanakis (SK) traditional functional states ( e.g., assault, defense, reserve, and supply). These models have since been replaced by the tri-service Operational Requirement-Based Casualty Assessment (ORCA) model. MUVES-S2 is a material-based vehicle vulnerability model that assesses threat shotlines through a vehicle to determine what components are damaged, given an insult, and to what degree. Several onboard components are the crew and passengers, which requires the use of MUVES-S2 to determine what specic insults may interact with those Soldiers/ Airmen; these would subsequently be assessed through ORCA. The insights provided by ARLs MUVES-S2 and ORCA models allowed high-resolution assess ments of levels of injury and, through mapping residual capability to required functions, a level of incapacitation over several periods of post-wounding time. ORCA incorporates previously and newly developed injury criteria, models, algorithms, and a widely used injuryseverity scoring systemthe Abbreviated Injury Scale (AIS)to characterize the threat to life and an individuals response to trauma from various types of insults. Using ORCAs embedded database of job descriptions, this injury characterization allows the assessment of remaining human performance ( i.e., physical, cognitive, and sensory). MUVES-S2,while used in previous aircraft assessments, provided component-level shotline analysis of penetrating fragments into the airframe; the MUVES-ORCA combination allowed the answering of questions not previously asked in other aircraft programs. MAIS Injury Level Type of Injury 1 Minor Supercial 2 Moderate Reversible injuries: medical attention required 3 Serious Reversible injuries: hospitalization 4 Severe Life threatening: not fully recoverable without care 5 Critical Non-reversible injuries: not fully recoverable even with care 6 Maximal Nearly unsurvivable Figure 1: Maximum AIS (MAIS) Scoring


AS Journal 14 / FALL h ttp:// 12 ORCA assesses the level of injury in AIS for each injurious shotline through an individuals body region. ARL determined that the maximum AIS (MAIS) threat to life and need for denitive medical care acceptable is a MAIS 3 (serious). Figure 1 illustrates the severity scale of MAIS injuries. Furthermore, when mapping those injuries to incapacitation, ORCAs Operational Casualty (OpCas) output answers the question: Can the person still do X, Y, or Z tasks? For the JCA mission, the authors rst had to decompose the ight proles and crew contributions to the aircraft throughout those proles into specic crew functions. This addressed what individual pilots did to maintain the aircraft in ight, the tasks that load masters performed, andin the case of passengerswhat was expected of them from takeoff through landing. As illustrated in Table 1, those required functions allowed the authors to aggregate tasks into specic job descriptions that ORCA used to assess incapacitation. Table 2 describes the mapping process from task to job. These jobs are then linked to the specic component of the JCA target description (see Figure 2) such as a pilot/copilot, a loadmaster, or a guy-in-back (GIB). With the assumption of redundancy, either pilot or copilot fullled the critical functions of maintaining ight while either of the load masters contributed to secondary functions of the aircraft cargo. In traditional uses of ORCA, each crew member would be assigned a specic job. However, given the unique nature of pilot/copilot taskings and built-in redundancies, these jobs had to be built in a subtle but powerfully different manner. In Table 1, the mission that the aircraft was undergoing, coupled with the phase of ight (vignette) the aircraft was in along that mission, bound the pilot team to required functions. As an example, if the mission was to y cargo a long distance, but the aircraft was already in ight when it was struck by anti-aircraft fragmentation, the pilot team would have to fulll all of the tasks associated with the airborne-landing mission prole, regardless of which pilot executed each of those tasks. Failure of any of those tasks results in an incapacitation. So the principal difference between the typical use of ORCA and those used in the JCA analysis is that in a traditional use, the job is mapped to the person. In the airborne jobs the person is mapped to the job performed. This allows the aircraft to continue so long as the pilot or copilot is able to perform the function of the aircraft. That is, in order for the task to be failed, both the pilot and copilot had to be incapable of performing it. The two vulnerability analyses (system level and crew vulnerability) then, answered two different question sets. In the system level analysis, three types of system-kill levels were assessed: „ A ttrition: the incapacitation of both pilot and copilot in fewer than 30 seconds, which used the Operational Casualty (OpCas) metric from ORCA. OpCas is a binary assignment of one (can perform the job) or zero (cannot), so that failure of both pilot and copilot means a loss of the aircraft. „ F ly and land: the inability to perform all of the tasks at a certain time ( e.g., ve, 15, or 30 minutes post injury) drives the analysis to determine how much longer the aircraft can stay in ight before it must have landed safely. Time beyond that window may result in attrition. Pilot/Copilot Loadmaster GIB Takeoff Tasks to Control A/C, Task to Communicate with ATC, Navigation Tasks, and Emergency Tasks Personnel/Cargo Accountability, Emergency Tasks X Cruise Tasks to Control A/C, Task to Communicate with ATC, Navigation Tasks, and Emergency Tasks Personnel/Cargo Accountability, Emergency Tasks X Landing Tasks to Control A/C, Task to Communicate with ATC, Navigation Tasks, Personnel Accountability, ID/ Exit A/C, and Emergency Tasks Personnel/Cargo Accountability, ID/Exit, Emergency Tasks Identify/Exit, Personnel Accountability Table 1: General Functions to Task Mapping, by Crew Position Job A job is dened as a list of an individuals tasks. Task A task is made of task elements A job can have one or more tasks. Task Element A task element a single activity with specic parameters. An instance of a task element is dened in the terms of elemental capabilities. Table 2: Job Decomposition Figure 2. Aircraft Conguration: Crew


13 h ttp:// A S Journal 14 / FALL „ Mission abort: if any troop member or crew sustained a MAIS 3 or greater, the aircraft would simply return to station short of its designated mission. Of course, loss of both the pilot and copilot leading to attrition supersedes a mission abort. The results of each threat-target combination allowed the analysts to determine a probabilistic outcome of how well the aircraft performed against the threat (see Figure 3). Furthermore, it allowed the developers to identify specic vulnerable locations. They could then add armor to those locations without up-armoring the entire aircraft and weighing it down, even if a complete through-and-through perforation hits nothing critical to the mission. This analysis directly supported the JCAs full-rate production milestone decision. While survivability has always been a concern for our systems, the JCA analysis provided the opportunity to address human survivability in an airplane. Adding this KPP to the requirement allowed the partnership to specically address human vulnerabilities in a high-resolution and meaningful manner not until recently touched. Figure 3. Example of Combined Threat-Target Shotline Analysis (Notional)


AS Journal 14 / FALL h ttp:// 14 by Scott Quackenbush, LCDRThe 2014 Threat Weapon and Effects Training (TWET) took place on Hurlburt Field, Okaloosa County, FL, and at Eglin Air Force Base (AFB), FL, 2224 April 2014. This annual training is presented by the Joint Combat Assessment Team (JCAT), sponsored by the Joint Aircraft Survivability Program Ofce. 2014 THREAT WEAPON AND EFFECTS TRAINING TWET is an excellent venue for represen tatives from Department of Defense (DoD) organizations, industry partners, and other government agencies to meet and network with other people who are interested in or work in the aircraft survivability eld. JCAT, as its name implies, is a joint organization, comprised of Army JCAT, staffed by members of the Aircraft Shoot Down and Assessment Team, Air Force JCAT, and Navy JCAT, made up of Navy reservists from the In-Service Engineering & Logistics (ISEL) unit. Each year, the three services share responsibility for conducting TWET. This year the training was led by Navy ISEL and organized by LCDR Scott Quackenbush, with a focus on the likely source and capabilities of future threats. JCATs mission is to perform hands-on forensic assessments on combat damaged aircraft. JCAT assessments are used to provide the forward-deployed operational commander with a nearreal time fact-based explanation of what happened to the aircraft, as well as provide the aircraft survivability commu nity with a detailed, pervasive record of damage sustained by the airframe. JCAT combat assessors have evolved into highly trained combat battle-damage and threat weapon analysts. Their training blends a highly technical and analytical capability with an in-depth knowledge of aircraft capabilities, friendly and enemy tactics, and enemy threat weapons capabilities and their effects. It includes continuous learning with threat weapons effects and munitions experts from the DoD ( i.e., Missiles and Space Intelligence Center, National Ground Intelligence Center, Naval Air Warfare Center Weapons Division Weapons Survivability Laboratory, as well as explosive experts from the Federal Bureau of Investigation and the Bureau of Alcohol, Tobacco, and Firearms). The prociency of a JCAT combat assessor is continuously evaluated and rened through collaboration with other service components, intelligence updates, and the training curriculum. TWET serves as continuing education for JCAT assessors, providing education and training in threat systems, combat-dam age assessment, and engineering analysis of data gathered. JCAT has had team members overseas supporting Operation IRAQI FREEDOM (OIF)since 2003, Operation ENDURING FREEDOM (OEF) since 2008, and currently supports forward detachments in Afghanistan at Camp Leatherneck, Bagram, and Kandahar. JCAT damage assessment reports are widely disseminated in near real time to coalition soldiers, affected platform program ofces, and the Figure 1. The 2014 Threat Weapon and Effects Training was another great success.


15 h ttp:// A S Journal 14 / FALLbroader scientic/survivability communi ties. To date, over 1,300 JCAT assessments documenting combat damage on aircraft have been completed for use by intelligence as well as future survivability engineering analysis. In total, 188 attendees participated in the 2014 TWET. The schedule of events included briefs, which took place at the Hurlburt Field theater, as well as eld training, which utilized Eglin AFB test ranges. Transportation to and from the range was provided for all participants, and typically took up one afternoon of the three-and-a-half-day schedule. This years presentations, made at the classied level, covered an analysis of combat damage from all of OEF and OIF, current and future threat systems, and survivability advances. Field activity included hands-on training with a Stinger trainer, observation and assessment of live re assets, and close observation of target damage from a just occurred live re. Figure 2. An Army JCAT assessor instructs a TWET attendee during the eld portion of the training. Figure 3. The Coveted 2014 TWET Challenge Coin.


AS Journal 14 / FALL h ttp:// 16 by Jordan Kaye, Mark E. Robeson, and Nathaniel BordickTo demonstrate an integrated platform solution that exemplies both operational durability and total survivability without deleterious effect on mission performance, the US Armys Aviation Development DirectorateAviation Applied Technology Directorate (ADDAATD) and Sikorsky are executing the Combat Tempered Platform Demonstration (CTPD). CTPD integrates and demonstrates enhanced aircraft and crew/occupant protection, improved battleeld durability, and reduced threat vulnerability. The integrated approach to vulnerability reduction enables the survivability requirements for current and future aircraft to be realized more efciently. AIRCRAFT SURVIVABILITY RATING Vulnerability assessments are an impor tant part of meeting the survivability requirements for many aircraft. Traditionally, these assessments consider the aircraft both at a system and subsys tem level to determine how survivable the aircraft will be against certain threats. Typical assessments consider how likely a component is to fail after ballistic impact, based on a damage modes and effects analysis (DMEA), and then track the failure through a failure analysis logic tree (FALT) to predict an end effect on the aircraft. End effects are considered the mission outcomes. Typically there are three outcomes analyzed: mission abort (MA), forced landing (FL), and attrition (At). Each outcome is assigned a probability of kill given hit ( PK/H) and a vulnerable area ( Av ). The PK/H and Av are often used for the validation of aircraft vulnerability require ments, armor trade studies, and protection optimization. In addition, assessments typically consider different mission points, such as high/fast and low/slow. The output of these assessments consists of one PK/H per mission point per mission outcome per threat. For example, for an assessment consisting of two threats, three mission outcomes, and two mission points, there will be 12 separate PK/H values as output. Turning these multiple output values into one usable number to rate the vulnerability of the aircraft or assess the impact of a single technology has proven to be a challenge. In addition, while these assessments account for component and system-level ballistic testing of the aircraft, they do not account for any aircraft reaction in the combat environ ment. To assess the vulnerability of an aircraft more accurately, combat data can be used to add an additional layer of statistical reasoning to rene the vulner ability assessment and reduce the multiple outputs of an assessment to a single number. The additional statistical layer and reduction to a single number enable an easier interpretation of the vulnerability of current or future aircraft and provide a means to further assess how various survivability features can improve the overall survivability of the aircraft. Required data When evaluating the survivability of a current or developmental aircraftthat is, determining its survivability ratinga key consideration is how to combine vulner ability assessment output with data from combat reports. For the present paper, it is assumed that a traditional vulnerability assessment is being performed; the assumptions made in that portion of the assessment will not be considered herein. Combat data will not always fall exactly into categories of threat, mission outcome, or mission prole in the way that a vulnerability assessment does. Threat Typically, an aircraft requirement will determine what threats are included in a vulnerability assessment. In combat there are often identied threats with many variations, unidentied threats, and multiple threats used simultaneously. Therefore it is important that more generic threat groups, such as small arms or heavy machine guns, are used for combat data instead of a specic threat. It should be determined in the beginning of the assessment what category certain threats will fall into, and also how to divide and account for attacks using multiple threat categories.


17 h ttp:// A S Journal 14 / FALL Mission Outcome As mentioned previously, vulnerability assessments typically consider three mission outcomes: MA, FL, and At. Combat data supports a fourth category representing no effect on the mission: not applicable (N/A). An N/A outcome represents when the pilot of the aircraft is either unaware of the damage or knows of the damage but continues the mission to completion. This category helps to account for pilot decisions in the mission, which are not considered in typical vulnerability assessments. Using this data more accurately predicts the real number of times that a more severe mission outcome occurs. Mission Prole While mission prole does not need to be accounted for in combat data, it is an integral part of the vulnerability assess ment. In determining a survivability rating, mission proles are used to create a weighted average value for the aircraft. This is based on mission proles typically developed in aircraft design. The mission proles can be analyzed to see how long the aircraft is in each mission condition assessed (for instance high/fast or low/ slow). This length of time can then be used to determine the percentage of time the aircraft will be in the state of vulnerability associated with a given mission prole. This approach allows multiple PK/H values to be collapsed into one weighted value, a key attribute of the present survivability rating methodology. COMBAT DATA Collection Combat reports must include, at a minimum, the type of aircraft, the assessed threats (including number of impacts), and enough information to determine the mission outcome. Reports should also be applicable to the aircraft being analyzed. Mission outcome is often left to the discretion of the analyst, as there may be some reports that do not directly state if the aircraft nished the mission or aborted. (This illustrates the importance of detail in the combat reports.) When analyzing the combat reports, the analyst must carefully track and document relevant data from each report to fully substantiate any conclu sions. When collecting relevant data from combat reports, the number of impacts on the aircraft (separated by threat) and the mission outcome are essential for determining the survivability rating. The statistical methods described in detail later are based on this aircraft impact data. Analyzing Analyzing the relevant combat data requires that it be reduced to percentages so that it can be applied in statistical methods discussed later. The data must be sorted for the following values: „ T otal number of aircraft impacts, broken down by threat group and mission outcome „ Pe rcentage chance of mission outcome, based on all threats „ P ercentage chance of encountering an individual threat group, inclusive of all outcomes As mentioned previously, when reviewing combat data there may be cases in which a threat impacts an aircraft, but the aircraft continues the mission to comple tion, resulting in a mission outcome category of N/A. It is suggested that these data points still be used when calculating the outcome probability discussed in the next section. The N/A outcome allows for the resulting survivability rating to better represent what happens in combat, as opposed to what is predicted to happen in the vulnerability assessment. CALCULATING SURVIVABILITY RATING Reducing Mission Points In the present methodology, the rst step in calculating the survivability rating is to reduce the data in the vulnerability assessment. This involves using a predetermined mission prole, and determining how long the aircraft will be in each of the mission points during that ight prole. For example, if there are four mission points analyzed in the vulnerability assessment, the time in each point must be determined, and from this, the percentage of time in each point must be determined. Using these percentages, the weighted average PK/H for each mission outcome and threat can be determined, as shown in Equation 1. Equation 1 should be applied for all mission outcomes, such that if three mission outcomes were analyzed, the result would be only one value for PK/H per outcome for each threat analyzed in the vulnerability analysis. If ight proles are not available, using an equal weighting for all mission points would be acceptable. Combining Threat Data As previously described, relevant combat data should be sorted into the number of impacts on the aircraft per threat group per mission outcome. An example of this approach to sorting data, highlighting the outcome probability, is shown in Table 1. Note that all values used in Table 1 are notional, and therefore do not represent any actual data. Equation 1 Calculating Average PK/H for Each Outcome and Threat


AS Journal 14 / FALL h ttp:// 18 The other key type of data needed is the percentage of time that the aircraft encountered each threat group. This threat probability is represented as the total number of impacts from the threat group divided by the total number of impacts from all threats present in the data set. Calculating Survivability Rating With the three key pieces of data (weight averaged PK/H, outcome probability, and threat probability) now determined, the survivability rating can be calculated. The rst step is to calculate the expected value of PK/H for all threats combined. This is done using Equation 2: This expected value of PK/H should be calculated separately for each mission outcome. Note that this equation only combines the PK/H for threats. Next, the solutions from Equation 2 are used to combine all of the mission outcomes into one survivability rating. This survivability rating is given by Equation 3. This survivability rating equation creates a weighted average of all outcomes and all threats to determine a single value to evaluate the chance of survival for the aircraft in combat. LIMITATIONS AND USES The greatest factor limiting the substantia tion of the survivability rating is the combat database used. Since the survivability rating is dependent on data from combat, a limited data set will result in a less robust result. In addition, a survivability rating developed using combat data from a particular combat theater is applicable only to that theater. If the combat theater changes, the data points will no longer be as valid, since different threats may be encountered. By grouping the threats in larger, more general categories, the effect on the survivability rating caused by varied combat theaters can be reduced. Additionally, the data used to calculate survivability rating can be supplemented with predicted operational uses and encountered threats. Interpretation The survivability rating produces a single value, which represents the chance that hostile re will affect an aircrafts mission. Since the rating takes into account different threats, different mission outcomes, and the mission prole, it can be interpreted as the percent chance that hostile re will lead to a negative outcome during a given mission. Unlike the output of a traditional vulnerability assessment, the survivability rating quanties not only the chance of a hostile attack in a given combat theater, but also the chance of actually being hit to the detriment of the mission. Current Uses Being able to statistically reduce a vulnerability assessment to a single survivability rating value can be helpful in the aircraft design process in that it simplies the amount of relevant data needed. In addition, by considering what threats are the most likely to hit the aircraft based on data or predictions, aircraft systemlevel protection can be better optimized to be either more or less robust, depending on the survivability rating and relevant requirements. This capability can lead to the aircraft meeting survivability requirements while having the potential to reduce weight by optimizing protection. Areas for Improvement The survivability rating and methodology to generate it can be improved in a few ways. The primary area for improvement is better combat data. The larger and more detailed the database, the better and more accurate the survivability rating will be. Limitations in the combat data or in its analysis can lead to false conclusions being drawn from the rating. Another way to improve the methodology is to determine how to change the incorporation of the combat data from something done after the vulnerability assessment into being part of the vulnerability assessment itself. If the assumptions made during the vulnerability assessment could more accurately reect what the outcome of the ballistic damage will be, the parts of the survivability rating can be incorporated into the assessment. This would allow the current methods of using ballistic test data to dene system reaction to be further expanded to begin to include pilot judgment and aircraft level Threat Group N/A Mission Outcome At Threat Probability MA FL A 20 10 3 0 51.5% B5 7 4 1 26.6% C3 5 2 4 21.9% Outcome Probability 43.8% 34.4% 14.0% 7.8% Table 1: Example Threat Data Equation 2 Calculating Expectxed PK/H for All Threats Combined Equation 3 Calculating Survivability Rating


19 h ttp:// A S Journal 14 / FALL reactions. Using statistical methods to collapse the multiple PK/H values would still enable simplied results. Future Uses The survivability rating could also be used to assess a future aircraft, if the predicted combat theater is known. Predictions can be made about the threat usage in that combat theater. This can allow for the expected value of PK/H (see Equation 2) to be calculated using predicted values. Calculating the survivability rating (see Equation 3) will be slightly more difcult because there will not be data for the outcome probability. However, data from similar aircraft can be applied, as long as it is applicable for threats and similar design, to make a prediction of how the aircraft will react to the threats. Moving forward, Sikorsky and ADDAATD will continue to apply the new aircraft survivability rating methodology during execution of CTPD. Furthermore, ADD AATD will seek opportunities for broader application of the aircraft survivability rating to benet the current Department of Defense (DoD) aircraft eet, with a particular focus on rotorcraft. In coming years, the aircraft survivability rating methodology will provide an additional tool for enhancing the survivability of the evolving DoD eet, including that being shaped by the Armys future vertical lift initiative. CONCLUSIONS A new methodology to rate aircraft survivability has been developed, making use of traditional vulnerability assess ments for aircraft while adding in combat data to align the results more accurately with what is encountered in actual usage. The rating can be applied to current aircraft to help create a baseline value against which survivability and vulnerabil ity improvements can be compared. The rating can also be applied to future aircraft to optimize survivability features. By taking multiple PK/H values from the vulnerability assessments and reducing them down to a single number, the relevant data becomes more manageable and allows for an easier comparison of results. This new methodol ogy is not only applicable to elded aircraft, but can also be applied to future aircraft and the development of require ments for more survivable aircraft eet. ACKNOWLEDGEMENTS This research was partially funded by the Government under Agreement No. W911W6-12-2-0005. The US Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation thereon. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the ofcial policies, either expressed or implied, of the Aviation Applied Technology Directorate or the U.S. Government. The present paper was presented at the American Helicopter Society International 70th Annual Forum, Montral, Qubec, Canada, 2022 May 2014, and published in the conference proceedings. The authors wish to thank Sikorsky Aircraft Company and the US Armys ADDAATD, without whom this effort would not have been possible.


AS Journal 14 / FALL h ttp:// 20 Currently, personnel survivability studies primarily focus on the Soldier surviving injuries in combat and not necessarily on how nonfatal injuries affect the ability to perform everyday functions after treat ment and recovery. Advancements in protective equipment and protection strategies, which are a result of these survivability studies, have greatly reduced the number of killed in action and have increased the number of wounded in action. Because of the increase in survivability, there is a need to characterize the effect of nonfatal injuries on long-term quality of life. A recently published metric called predicted Functional Capacity Index (pFCI) quanties long-term functional limitations one year post injury.The pFCI is an application of Functional Capacity Index (FCI) provided in the AIS 2005Update 2008 dictionary [1]. The Abbreviated Injury Scale (AIS) is a global scoring system that classies injuries based on type, location, and severity. The values for pFCI range from 5 to 1, where 5 is no functional limitation on daily life and 1 is maximum functional limitation. Therefore, to understand what the pFCI values mean, one must understand FCI. FCI is a 10-dimensional index that characterizes long-term functional limitation on daily life one year after injury. The 10 dimensions characterized are eating, excretory, sexual, ambulation, hand/arm movements, bending/lifting, visual, auditory, speech, and cognitive function. Within each dimension there are three to six levels (AF) that describe the level of functional limitation for that dimension. The index is written as letters, where each letter corresponds to the level of functional limitation for each dimension and an overall score. [2,3] FCI was created by Dr. Ellen McKenzie, along with her colleagues at the Johns Hopkins Bloomberg School of Public Health and in partnership with the Association for the Advancement of Automotive Medicine and the AIS scaling committee. It was created as a compan ion to AIS, which is primarily a threat-to-life metric that does not sufciently characterize long-term functional limitation. pFCI was created by lumping the overall score from the FCI into the ve levels and assigning a score to each injury dened in the AIS dictionary. [2] Because the data that serves as the basis for pFCI is based on civilian data, it was very important to perform analyses to determine if the metric is useful for military applications, as well as to determine if it provides additional information for survivability studies. The goal for this metric is not to replace currently used survivability metrics, but to be used in conjunction with existing metrics to understand the inuence of survivable injuries on quality of life. With this in mind, several analyses were conducted to demonstrate the usefulness of this metric. To determine if pFCI provides additional information that can be used to supple ment survivability studies, the distribution of AIS severities versus the distribution of pFCI was investigated to understand how signicant injuries are distributed across the body regions. Within the evaluation community for survivability studies pertaining to the US Soldier, signicant injuries are dened as injuries coded AIS level 3 (serious) or greater. In terms of pFCI, all injuries that have an effect of long-term functional impairment were classied as serious injuries for the analyses discussed in this paper. After reviewing the distribution of injuries, it was noted that the head and spine were the two body regions that sustained the most AIS serious or greater by Latrice Hall EVALUATING LONG-TERM IMPACT OF NONFATAL INJURIES


21 h ttp:// A S Journal 14 / FALL injuries. The two body regions with the most AIS injuries that have a long-term effect on daily life were the head and lower extremities. The difference between these distributions shows that some AIS moderate and minor injuries, which are not considered signicant injuries in terms of threat to life, could have a long-term effect on daily life. Also, the distributions show that injuries that are considered signicant in terms of AIS severity may not affect functional limitations. The pFCI scores were implemented in a personnel vulnerability model to demon strate its usefulness for military applications. This personnel vulnerability model used by the U.S. tri-service vulnerability community is called the Operational Requirement-Based Casualty Assessment (ORCA) model. ORCA evaluates the effect of various battleeld insults such as blast overpressure, penetration, and acceleration on personnel targets to predict injuries and functional impairment [4]. The injuries that ORCA predicts are coded using the AIS 2005 Update 2008 dictionary, therefore, the implementation of pFCI was fairly straightforward. In terms of severity scales, both AIS severity and pFCI assume that the person received only one injury. Since a single insult on a personnel target could produce multiple injuries, summary metrics are used to characterize overall severity for an individual. The summary metrics used are Maximum Abbreviated Injury Scale (MAIS) for evaluating threat to life and minimum predicted Functional Capacity Index (mpFCI) for evaluating quality of life. MAIS classies injury severity on the basis of the injury with the greatest AIS severity value. mpFCI classies functional limitation on the basis of the injury with the greatest effect on long-term functional limitation. The range of values and meaning for both metrics are located in Table 1 and Table 2. A survivability analysis using penetrating threats was performed to further understand the benet of using both metrics. Two different threats were analyzed to demonstrate the differences between MAIS and mpFCI. This analysis was performed to visualize how the vulnerable area changes as the threat changes, as well as where the two can differ for specic shot lines to the body. Figure 1 shows an example of a 4 grain steel fragment traveling 600 meters per second (m/s) against a represented personnel anatomy. A uniform distribu tion of shot lines to the body was modeled to sample all impact locations to the front of the body. The colors for each sample point represent the MAIS or mpFCI for all injuries along the shot line. In Figure 1, injuries in the lower arms do not receive a MAIS value greater than 2, which means those injuries are classied as moderate or minor. For mpFCI, some injuries in the arms received an mpFCI value that were less than 5, which classied them as signicant injuries relative to quality of life. This example MAIS Injury Level Head Injury Example 1 Minor Minor laceration of scalp 2 Moderate Major laceration of scalp, blood loss < 20% 3 Serious Fracture of skull, penetration < 2 cm 4 Severe Depressed skull fracture, penetration > 2cm 5 Critical Depressed skull fracture, laceration of spinal artery 6 Maximal Massive brain stem crush Table 1: MAIS Legend with Examples Table 2: mpFCI Legend with Examples mpFCI Injury Level Head Injury Example 5 None Penetrating injury to skull; supercial 4 Minor Vestibulocochlear nerve laceration (cranial nerve) 3 Moderate Large contusion of cerebellum 2 Severe Penetrating injury to skull; major 1 Maximal Massive brain stem crush Figure 1: MAIS and mpFCI for 4 Grain Steel Fragment at 600 m/s Figure 2: MAIS and mpFCI for 100 Grain Fragment at 900 m/s


AS Journal 14 / FALL h ttp:// 22 shows that some minor and moderate injuries could be counted in assessing survivability, since they could cause long-term effects. The second threat velocity combination was of a 100 grain steel fragment traveling at 900 m/s against a represen tative personnel target. The results in Figure 2 show there were several shot lines that produced signicant injuries in terms of both MAIS and mpFCI. There were very few shot lines that had signicant injuries in terms of MAIS that were not signicant in terms of mpFCI; however those shot lines do exist. This demonstrative analysis shows that the agreement between the two metrics increases as the size of the threat increases, as expected, because of the signicant levels of trauma. pFCI allows analysts to characterize another aspect of survivability. Survivability does not only deal with being able to survive an injury, it also deals with the ability to recover from that injury. The AIS severity score, which characterizes an injurys threat to life, mainly addresses the ability to survive an injury. Using AIS and pFCI in conjunction allows analysts to not only predict threat to life, but also quality of life and functional limitations for a given injury. The results of the analyses show that minor and moderate injuries in terms of threat to life can signicantly decrease long-term quality-of-life. Work is ongoing to continue to improve FCI to better model all types of civilian and military trauma. References:[1] Association for the Advancement of Automotive Medicine. AIS 2005 Update 2008 Barrington, IL, 2008. [2] M acKenzie, Ellen J., Anne Damiano, Ted Miller, and Steve Luchter. The Development of the Functional Capacity Index. Journal of Trauma 41, no. 5 (1996): 799807. [3] M acKenzie, E.J., et al. Validating the Functional Capacity Index as a Measure of Outcome Following Blunt Trauma. Quality of Life Research 11, no. 8 (2002): 797808. [4] N eades, D.N., and E. G. Davis. A New Approach to the Simulation of Battleeld Injuries and Their Effect on the Performance of Military Tasks. In 20th International Symposium on Ballistics Orlando, FL, September 2327, 2002.


23 h ttp:// A S Journal 14 / FALL by Christopher Adams EXPANDING AIRCRAFT COMBAT SURVIVABILITY TO INCLUDE FORCE PROTECTION The U.S. military Services design aircraft to operate in both normal and combat ight environments. The normal ight environment includes day-to-day operations conducting routine missions such as training and humanitarian assistance, with the usual takeoffs, transits, and landings. It also includes the natural hostile environment with its brownouts, severe turbulence, lightning strikes, bird strikes, midair collisions, and crashes. The combat (or man-made hostile) ight environment includes traditional combat with enemy forces using surface-to-air and air-to-air guns and missiles, as well as on-board terrorist threats, such as suicide bombers and bombs in suitcases. [1]Aircraft can be damaged, lost, or killed, and aircraft occupants injured or killed as they y in both normal and combat ight environments. Three disciplines, or communities, share responsibility for preventing damage or loss of aircraft and protecting occupants from injury and death. System safety (SS) involves the application of engineering and manage ment principles to identify hazards and then to eliminate the hazards or reduce the associated risks when the hazards cannot be eliminated. The expanded aircraft combat survivability (ACS) involves application of design principles to increase the capability of an aircraft and its occupants to avoid or withstand damage from a man-made hostile environment ( i.e., combat). Human systems integration (HSI) is a recently developed discipline that has a goal of optimizing total system performance and total ownership costs while ensuring that the system is designed, operated, and maintained to effectively provide the user with the ability to complete his or her mission. The HSI discipline will be described in an upcoming issue. Although there are some similarities between these three disciplines, when it comes to system design techniques and protecting occupants, each has unique responsibilities to ensure users can effectively and safely operate their aircraft to accomplish their assigned missions. To identify the appropriate discipline responsible for preventing or mitigating each particular damage event, the ight environment in which the event occurs, the cause of the event, and the outcome of the event must be considered. For example, consider event number one, consisting of an aircraft on a training mission (the aircraft is operating in the normal ight environment). The engine throws a fan blade, which results in an engine re and the eventual loss of the aircraft and the death of all of the occupants in a crash. The event is caused by the hazard associated with the thrown fan blade, and the outcome of the event is a loss of the aircraft and death of all of the occupants in a crash. Because the event occurs in the normal ight environ ment and is the result of a mechanical failure, the event falls within the purview of the SS discipline. Consider a very similar event, number two, in which the aircraft is on the same mission that the aircraft in event number one was training for, but this mission is in a combat zone. The cause of the event is a fan blade failure leading to a crash and the subsequent death of the occupants. This event was the purview of SS in the normal environment. Does the fact that the aircraft is ying in a combat zone in this event change anything?


AS Journal 14 / FALL h ttp:// 24 Consider another event, number three, consisting of an attack aircraft with a single pilot on a close-air support mission in a combat zone (the aircraft is operating in the combat ight environment) that is attacked and killed by the launch, impact, and detonation of an infrared surface-toair missile (IR SAM). The aircraft kill is due to the impact of a threat weapon, and in this example the pilot safely ejects. Because this event occurs within a combat environment and the aircraft kill is due to the IR SAM (a threat weapon), the event falls within the purview of the ACS discipline. In a fourth event, a helicopter carrying troops is ying low to avoid detection in a combat zone (the combat environment), an example of threat avoidance. While ying at a low altitude, the helicopter collides with several electrical power lines and crashes. The aircraft kill and the occupant casualties are due to the collision with the power lines and subsequent crash, not to the damage mechanisms of an enemy weapon. The incident is due in large part, however, to the very existence of the threat (or air defense) environment. The helicopter is ying in a combat zone, but it is not shot down by a threat weapon; rather it crashed as it was attempting to avoid a weapon engagement. Which discipline has the responsibility to prevent or mitigate this event and to protect the operating crew and passengers? In the fth event, another low-ying helicopter carrying troops in a combat zone is shot at by an automatic small arms weapon. The helicopter is hit by several bullets, but survives the attack with minimum damage due to its low vulnerability design. It continues on its mission with some minor aircraft damage, but no aircraft kill. However, three of the troops in the passenger cabin were hit by the gunre, however; one was killed and two were wounded. Which discipline has the responsibility to prevent or mitigate this event and to protect the operating crew and the passengers? In the nal event, number six, another low-ying helicopter carrying troops in a combat zone is shot at by several automatic small arms weapons. The helicopter is hit many times, loses the ability to y with control as rotor blades break, and crashes. A re starts, and many of the occupants are killed either by the impact with the ground or the subsequent re. Which discipline has the responsibility to prevent or mitigate this threat-caused event and to protect the operating crew and the passengers before and after the aircraft impacts the ground? (Table 1 summaries the six events) To help identify the discipline responsible for all possible events, consider the following denitions for three general categories of events consisting of an aircraft loss or fatal injuries to the occupants of the aircraft. These event categories were developed by the Joint Aircraft Survivability Program (JASP) to categorize all actual combat incidents that resulted in an aircraft loss or occupant fatality (see Figure 1). „ C ombat hostile action covers any Class A mishap (loss of aircraft or fatal injuries to the crew/passengers) caused by a threat weapon; this includes aircraft evading the threat, destroyed in place, or deemed irreparable.. „ C ombat non-hostile covers any Class A mishap occurring within a recog nized combat theater of operations in which the loss of aircraft or fatal injury to the crew/passengers is not a direct result of a threat weapon. „ N on-combat events cover Class A mishaps occurring outside a recog nized combat theater of operations. Note in Table 1 that the pertinent discipline can be relatively easily identied in only two of the six events. To determine the specic discipline respon sible for the remaining four events, more information about the specic coverage of these disciplines is needed. Consequently, the SS discipline and the ACS discipline are briey described below. The HSI discipline will be described in Part 2 in an upcoming issue of the Aircraft Survivability Journal. SYSTEM SAFETYSystem safety, the oldest of the three disciplines involved in the design of military aircraft for vehicle and occupant safety and survivability, attempts to eliminate, minimize, or control those conditions known as hazards that can lead to a mishap. Hazards are described in MIL-STD-882E as: A real or potential condition that could lead to an unplanned event or series of events (i.e., mishap) resulting in [unintentional] death, injury, occupational illness, damage to or loss of equipment or property, or damage to the environment. [2] Combat Hostile Action Combat Nonhostile Noncombat Figure 1: Event Categories (courtesy of JASP)


25 h ttp:// A S Journal 14 / FALL Hazards result from internal system hardware and software failures, poor human interface designs, operator errors, or by outside inuences, such as those environmental factors associated with the natural hostile environment. They are eliminated, minimized, mitigated, or controlled by design, a safety device, a warning device, or training. In summary, the SS discipline is responsible for preventing or mitigating event(s)/ mishap(s) that result in the unintentional injury or death of the occupants and/or unintentional damage to or loss of an aircraft while the aircraft operates in either the normal and combat environment. Damage caused by enemy weapons is not considered in system safety since the threat-caused damage is intentional.AIRCRAFT COMBAT SURVIVABILITYAircraft combat survivability began its development as a design discipline during the Vietnam conict over 40 years ago, when approximately 4,000 U.S. xed and rotary-wing aircraft were lost in combat. (An additional 4,310 aircraft were lost due to mishaps in theater i.e., combat non-hostile events.). ACS is dedicated to enhancing the capability of an aircraft to survive while operating in a combat or man-made hostile environ ment, where the damage or loss of aircraft and the death or injury of the occupants is intentionally caused by the enemy. Aircraft combat survivability is comprised of two components: susceptibility and vulnerability. Susceptibility is the inability of an aircraft to avoid hits by the damage mechanisms carried or generated by warheads on the enemys weapons, such as ballistic projectiles from guns, or fragments and blast from internal or external detonation of high explosive (HE) warheads. Vulnerability is the inability to withstand any hits by the projectiles, fragments, and blast that do occur. [1] The primary focus of ACS has been on designing aircraft to be more survivable in combat, as opposed to the combined aircraft and occupant safety focus of SS, which is primarily concerned with the non-combat and combat non-hostile ight environments. The ACS aircraft-centric concentration on keeping the aircraft ying while operating in a man-made hostile environment does not mean there is no consideration given to any of the occupants. Those aircraft occupants that are essential to the continued controlled ightor survivalof the aircraft ( i.e., the operating crew), must be protected from death or serious injury if the aircraft is to survive. For example, the single pilot on the close-air support A-10 Thunderbolt II, or Warthog, sits inside a heavy titanium armor tub to protect him or her from ballistic projectiles or warhead fragments that hit the aircraft in the pilots vicinity. The armor tub under and around the pilot was not put there by a safety engineer to enhance the pilots safety; bullets and fragments are not considered safety hazards because they are not uninten tional. They were put there by a vulnerability reduction engineer to protect the pilot, and hence enhance the aircrafts combat survivability by preventing a critical component (the pilot) from being killed by a bullet or fragment. However, there is a great deal of overlap between designing for system safety and designing for combat survivability. There are many design features on an aircraft that simultaneously enhance safety and survivability, or more specically reduce vulnerability. Consider the hydraulic subsystem on an aircraft. Failure of a hydraulic seal due to a material defect (safety) or fragment hit (vulnerability) could lead to a sequence of possible effects: 1) the ammable hydraulic uid Event Environment Cause Outcome Category Discipline #1 Normal Engine fan blade failure Aircraft loss & occupants killed in crash Non-combat SS #2 Combat Engine fan blade failure Aircraft loss & occupants killed in crash Combat non-hostile ? #3 Combat IR SAM hit Aircraft killed & pilot ejects Combat hostile action ACS #4 Combat Power lines (while avoiding detection by an active threat) Aircraft loss & occupants killed in crash Combat hostile action ? #5 Combat Gunre Occupant killed due to gunre Combat hostile action ? #6 Combat Gunre Aircraft loss & occupants killed in crash Combat hostile action ? Table 1: Event parameters


AS Journal 14 / FALL h ttp:// 26 leaks from the failed or killed hydraulic seal onto a hot surface, 2) the uid ignites, 3) the subsequent hydraulic uid re burns through the single data bus carrying a bundled set of control signals to the surface actuators at the tail of the aircraft, 4) the pilot loses control of the aircraft, and 5) the aircraft crashes. This safety hazard could be minimized at an acceptable cost by design (replacing the ammable uid with nonammable uid and moving the control signal lines or adding a second, separated control path for redundancy), by adding a safety device (installing re detection and extinguishing equipment near the actuator), by adding a warning device (a re light in the cockpit to alert the pilot of the emergency condition), and by training (the pilot practices emergency re procedures). Note that all of these features control the hazard and also reduce the vulnerability of the aircraft by increasing its capability to withstand the combat (man-made) hostile environment. In other words, the hydraulic subsystem is now both safer and less vulnerable to a leak, regardless of whether the leak was caused by a part failure (SS) or a threat warhead fragment (ACS). [1] Not every safety feature enhances combat survivability, however, unless it is also designed to do so. For example: Redundant hydraulic power sources are a safety feature, regardless of their location. They are also a combat survivability feature, but ONLY when there is sufcient separation between the redundant power sources so that a single hit by a threat weapon, such as an internally detonating 23-millimeter HE projectile, does not kill all redundant power sources. Furthermore, many safety features are limited in their ability to control hazards when an aircraft is hit by an enemy weapon, particularly those with high explosive warheads. Simultaneous failures of multiple unrelated systems is possible with aircraft combat survivability, but not typically considered with system safety. Additionally, the concept of cascading damage, where one hit component causes other nearby components to fail, potentially overwhelming installed safety features, plays a major role in combat survivability. An example of likely insufcient safety features in the non-combat environment was TWA 800, a 747 that apparently had a spark-caused major explosion in the mid-wing fuel tank, resulting in the total loss of the aircraft. After this incident, an onboard inert gas generating system was proposed for airliner fuel tanks to reduce the likelihood of a fuel tank explosion. In this case, the redesign of the aircraft for improved safety involved the use of a combat survivability design feature used on military aircraft. An example of cascading damage from a non-combat event similar to what might be seen in a combat is Air France 4590, a Concorde taking off from Charles de Gaulle International Airport on 25 July 2000. Shortly before rotation, the front right tire of the left landing gear ran over a strip of metal and was damaged. Tire debris was thrown against the lowerleft wing structure, leading to a ruptured fuel tank due to the hydrody namic ram caused by the impact of the tire debris. A major re ignited almost immediately and as the aircraft took off, indications of a re alarm on engine 2 appeared and the crew shut down the engine. They noticed that the landing gear would not retract, causing signi cant drag on the aircraft in the heavily loaded takeoff conguration. The aircraft ew for around a minute at a speed of 200 knots and at an altitude of 200 feet, but was unable to gain further height or speed. Then engine one lost thrust, leading to a signicant increase of the aircrafts angle of attack and bank. Then thrust on engines three and four fell suddenly. As can be seen from this example, the Concorde did not have typical military survivability enhancement features for vulnerability reduction, such as sufcient hydrodynamic ram protection, an effective system to inert the fuel tank against an in-tank re, or redundant engine controls routed with enough separation (or physical protection) such that a re could not disable the engine control path. EXPANDING THE SCOPE OF THE ACS DISCIPLINEHistorically, ACS has had an aircraftcentric view of survivability and force protection. This view is primarily driven by the assumption that if the aircraft continues to maintain the essential or critical ight functions (lift, thrust, control, and structural integrity), then all of the occupants on the aircraft are indirectly protected. This viewpoint is inherent in the denitions of the aircraft attrition kill levels (KK, K, A, and B), based on ying time after being hit. The recent conicts in Iraq and Afghanistan, however, have shown many instances in which crew members and passengers have been killed or seriously injured, even though the damage to the aircraft did not reach attrition kill level. Event example number ve is an illustration of that possibility. Consequently, to fully consider force protection for all of the occupants, casualties must be considered as a separate metric from aircraft attrition. Because of the importance of force protection for all occupants and the need to reduce casualties from all potential sources, a recent framework has been developed to expand the scope of ACS to


27 h ttp:// A S Journal 14 / FALL include consideration of all occupants on an aircraft ying in a man-made hostile environment, not just the crew that are essential for ight. [3] Recent efforts within the Department of Defense in the past several years to include comprehen sive force protection requirements as part of ACS have been a key driver in addressing user casualties in survivability assessments as required by Section 2366, Title 10, of the U.S. Code. In particular, there has been an ongoing effort since 2007 to expand ACS to include occupant crash survivability, particularly for helicopters. Methodologies to evaluate crew casualties using the Computation of Vulnerable Area Tool and Advanced Joint Effectiveness Model have been imple mented since 2010. The Director, Operational Test and Evaluation has also endorsed using force protection analysis methods in the development of the live-re strategy for new programs. From an earlier Aircraft Survivability Journal article: The combat hostile action loss rate for (rotary-wing) aircraft in Operation ENDURING FREEDOM (OEF) and Operation IRAQI FREEDOM (OIF) was eight times lower than Vietnam, primarily because aircraft vulnerability reduction design reduced the cheap kills caused by the small arms and automatic weapon threats. The human fatality rate associated with combat hostile action (helicopter) losses also showed a reduction from Vietnam to OEF/OIF, but not to the same extent. Some of this decrease in the fatality rates can be attributed to having more survivable aircraft, but improvements in airframe crashworthiness and crash protection for passengers are necessary to further reduce fatalities and injuries. [4] Also, members of the ACS community have been given instructions to: ...broaden their scope and refocus their efforts, and to work in concert with the aircraft safety community to predict and reduce combat-related occupant (passenger and crew) casualties. [4] Note that broadening or expanding the scope of ACS to include all of the occupants (not just the ight essential crew) and crashes (which have historically been the responsibility of system safety) will involve a sharing of informa tion, but not an overlap of responsibilities. However, it should be noted that at least one well-known military aircraft manu facturer tasks its vulnerability reduction personnel for enhancing crash survivabil ity including the structures, fuel systems, and occupant-protection design teams. The sequence of events for the expanded aircraft combat survivability discipline begins with an assessment of the threats to the aircraft while it is operating in a man-made hostile environment and ends with an assessment of the aircrafts survivability and any crew and passenger casualties to the point of safe return or egress from the combat zone. Figure 2 Air France 4590 on takeoff


AS Journal 14 / FALL h ttp:// 28 SURVIVABILITY AND FORCE-PROTECTION KEY PERFORMANCE PARAMETERS (KPP s)Finally, consider the relationship between SS, ACS, and two of the mandatory KPPs for manned systems: survivability and force protection. These KPPs will have different emphases. Survivability KPPs should emphasize preventing a system kill, whereas force protection should emphasize preventing personnel casualties [5]. According to the Joint Capabilities Integration and Development System (JCIDS), survivability attributes are dened as: . . those that contribute to the surviv ability of a manned system. This includes attributes such as speed, maneuverability, detectability, and countermeasures that reduce a systems likelihood of being engaged [hit] by hostile re [susceptibility reduction], as well as attributes such as armor and redundancy of critical compo nents that reduce the systems vulnerability if it is hit by hostile re [vulnerability reduction]. [6] Because the survivability KPP is speci cally applied to the manned aircraft as a system and addresses only the hostile re threat associated with a combat (man-made) hostile environment, ACS is the pertinent system design discipline for the survivability KPP. Even though ACS has been broadened to include all aircraft occupants, it still retains all the inherent coverage of aircraft survivability Force-protection attributes are dened in JCIDS as: . . those that contribute to the protection of personnel by preventing or mitigating hostile actions [or threat effects] against friendly personnel, military and civilian. This may include the same attributes as those that contribute to survivability, but the emphasis is on protecting the system operator or other personnel rather than protecting the system itself. Attributes that are offensive in nature and primarily intended to defeat enemy forces before they can engage friendly forces are not considered force protection attributes. Attributes that protect against accidents, weather, natural environmental hazards, or disease (except when related to a biological attack) are also not part of force protection. [6] The force-protection KPP applies to all occupants on an aircraft operating in a combat environment. The emphasis of the KPP is to address personnel casualties more broadly. A forceprotection KPP might address tactics, techniques, and procedures (TTPs) or a system design feature that directly protects the crew [7]. In fact, the only aircraft survivability enhancement feature outside the scope of the JCIDS denition of the force-protection attributes is threat suppression, because it is typically offensive in nature and intended to defeat enemy forces before they can engage. The other ve susceptibility-reduction concepts (threat warning, signature reduction, expendables, tactics, and noise jamming and deceiving), although not emphasized, and the six vehicle vulner ability reduction concepts (component redundancy with separation, component location passive damage suppression, active damage suppression, component shielding, and component elimination/ replacement) could be applied to show how personnel casualties are reduced. The difculty when applying all of the susceptibility and vulnerability reduction concepts, with respect to the forceprotection KPP, is to show how personnel casualties are directly reduced, and not just how they increase the survivability of the aircraft. If the historic aircraft-centric view of ACS were retained, it would be somewhat more difcult to dene a force-protection KPP that is not also a survivability KPP. For example, consider the armor tub installed on the A-10 aircraft. From an aircraft-centric view of ACS, the armor tub that protects the pilot (who is a critical component of the ight-control system) is a survivability enhancement feature of the aircraft, with force protection being incidental. From this perspective, and depending on the threat being evaluated, an aircraft designer could trade the weight of the tub and the protection it provides to the pilot for the ability to carry extra weapons or fuel, assuming the user is willing to accept any increased vulnerable area attributed to the pilot. However, from a force protec tion view of ACS, the armor tub fullls a clear role: protecting the pilot from being killed or injured. Although other methods could be used to enhance vehicle survivability, such as including a second pilot (effectively separated from the other pilot), the aircraft designer may not be able to trade the tub for something else because the metric of crew casualties would still need to be evaluated. Unfortunately, adding armor to protect occupants tends to be the default response when developing a forceprotection KPP. This need not be the case. The predominant threat in the ight regimes of interest should drive the requirement. For example, users could write a force-protection KPP to add armor in the cockpit of a large xed-wing aircraft to protect pilots from being hit by small arms projectiles. At rst look, this appears to be very clear requirement to


29 h ttp:// A S Journal 14 / FALL provide protection for personnel. However, since there is no requirement to put armor in the rest of the aircraft to protect the nonpilot crew and passen gers, this is really a survivability KPP with the appearance of a force-protection KPP. In this instance, the purpose of the armor is to protect the pilots, who are consid ered critical components, with the rationale that killing both pilots will result in killing the rest of people on the aircraft. This rationale invokes the aircraft-centric view of ACS, which relegates the pilots, crew, and passengers to be either critical components or noncritical components, and accordingly noncritical crew and passengers are not protected. This discrepancy becomes more acute if the aircraft only spends a small portion of its time at low altitude where small arms threats are prevalent. Looking across all ight regimes, maybe a better forceprotection solution would be to add an emergency oxygen system such as the one used on commercial airlines when there is a sudden loss of cabin pressure. This emergency system could also protect against smoke and other toxic gases in the event there is a threat-induced re in the cabin area. It would likely have the added benet of weighing less than the armor. This emergency oxygen system would serve as both a safety feature to prevent loss of oxygen during a sudden depressurization and an aircraft surviv ability feature to provide an alternate oxygen source to avoid crew and passenger asphyxiation. Finally, consider ejection seats installed in a jet aircraft or crashworthy seats installed in a helicopter. From the aircraft-centric perspective of ACS, neither would buy their way on the aircraft because they dont increase the survivability of the platform. However, from an expanded scope of ACS that includes force protection, both can be considered part of force protection because these features help save lives, even though the aircraft might be an attrition loss. One might argue that the last sentence in the JCIDS description of the force-protec tion attribute would prohibit considering ejection seats and crashworthy seats because they protect against an accident (or mishap in the system safety vernacu lar). This is not the case; neither seat protects against the mishap. The mishap may occur regardless of whether the seat (ejection or crashworthy) is installed. The purpose of the seat is to protect its occupantclearly a forceprotection concern. Additionally, the ACS discipline would need to address concerns such as the compressed timeline for a pilot to eject out of a severely damaged aircraft from combat hostile action, such as in internal detonating warhead leading to an explosion and immediate loss of aircraft structural integrity. This scenario would require that an ejection seat be built with features to ensure successful ejection under unique ight envelopes that would be outside of the normal ight environment.IDENTIFYING THE RESPONSIBLE DISCIPLINESReturning to the six examples of events shown in Table 1, now that the signicant details of the SS and the expanded ACS disciplines and the survivability and force-protection KPPs have been described, a decision can be made as to which discipline is the primary discipline responsible for preventing or mitigating an event (see Table 2). Consider event number two. Even though the event occurs in the combat environ ment, the cause of the event, a fan blade failure, is not threat related. Hence, SS is the applicable discipline. Figure 3: Concorde Crash


AS Journal 14 / FALL h ttp:// 30 In event number four, if the helicopter were ying low in a combat zone to avoid detection, then SS is again the appropri ate discipline, because helicopters can y low and into power lines in normal environmentsnot because of damage from a threat weapon. However, if the threat is red at the aircraft ( i.e., an engagement occurs) and the aircraft ies into the wires while attempting to evade the approaching threat, then the loss is directly related to the aircrafts attempt to evade the threat. In this case the loss would be categorized as a combat hostile action loss, and ACS would be the appropriate discipline responsible for preventing or mitigating similar events in the future. For event number four, the time when the event occurseither before or after the threat engages the aircraftdetermines the appropriate discipline. However, one might consider whether an aircraft attempting to avoid detection by an active threat, and a subsequent weapons engagement, blurs the lines of before (avoid detection) and after (engage ment) categorization. Perhaps the loss of aircraft and crew were due to combat TTPs, poor threat warning system, inadequate signatures (IR, radar, acoustic) that required the aircrew to y nap-ofthe-Earth, or perhaps they experienced a loss of situational awareness due to certain wartime modes and sensors. The ACS contributions to reduce losses from a threat engagement are obvious, but clearly the SS and ACS communities must work together to enhance safety and survivability in this scenario. In event number ve, the aircraft-centric scope of ACS did not include protection of the passengers, and SS does not consider intentional threat-caused events. Thus, expanding ACS to include force protection for all occupants is a necessary action, particularly since ACS includes protection of those members of the force who are critical components. In event number six, the cause of the crash is combat related, and therefore not within the purview of SS. However, aircraft also crash while ying in normal environments, which is in the purview of SS, so assigning crash survivability to the SS discipline is reasonable. On the other hand, the crash of an aircraft that has been severely damaged in combat can be signicantly more catastrophic, so assigning the responsibility for crash survivability to the expanded ACS discipline is also reasonable. Therefore, once again, a shared view of both the SS and the expanded ACS discipline seems to be the best solution. Both disciplines need to share information and work to design optimized solutions to improve the survivability of the aircraft and the survivability and safety of personnel on board.RECOMMENDATIONS AND SUMMARYFive recommendations are provided below to facilitate the transition of the expanded ACS discipline from policy to common practice. The ability to address all potential combat-related casualty sources can be achieved by taking a number of steps from several organiza tions, including: „ I ntroducing the expanded force protection coverage into future ACS educational programs and forums „ F unding technology for reducing occupant casualties in combat „ R ening the methodology for assessing the level of occupant protection in combat „ T esting for occupant protection „ W orking with the requirements community to coordinate responsibilities between the SS, ACS, and HSI disciplines. Event Environment Cause Outcome Category Discipline #1 Normal Engine fan blade failure Aircraft loss & occupants killed in crash Non-combat SS #2 Combat Engine fan blade failure Aircraft loss & occupants killed in crash Combat non-hostile SS #3 Combat IR SAM hit Aircraft killed & pilot ejects Combat hostile action ACS #4 Combat Power lines (while avoiding detection by an active threat) Aircraft loss & occupants killed in crash Combat hostile action SS & Expanded ACS #5 Combat Gunre Occupant killed due to gunre Combat hostile action Expanded ACS #6 Combat Gunre Aircraft loss & occupants killed in crash Combat hostile action SS & Expanded ACS Table 2: Event Parameters with Expanded ACS


31 h ttp:// A S Journal 14 / FALL In summary, the scope of the ACS discipline now includes comprehensive force protection as a matter of policy. This would also include combat-related crash survivability for all occupants on an aircraft, not just the crew that are critical to ight of the aircraft. Furthermore, ACS should work in concert with the SS discipline to achieve force-protection synergy in the design of the aircraft for all ight environments. The second part of this article will describe the domains of the HSI discipline and examine how these domains interact with those of SS and the expanded ACS, especially as they relate to enhancing aircraft survivability and force protection.ACKNOWLEDGEMENTSThe author would like to thank Dr. Robert E. Ball, distinguished professor emeritus, Naval Postgraduate School and consul tant, SURVICE Engineering Company; and Dr. Mark Couch, Institute for Defense Analyses, for their review of this article. References[1] Ball, Robert E. The Fundamentals of Aircraft Combat Survivability Analysis and Design. 2nd ed. American Institute of Aeronautics and Astronautics, Inc.: 2003. [2] D epartment of Defense Standard Practice: System Safety. MIL-STD-882E. 11 May 2012. [3] W illiamsen, Joel, James Rhoads, and Mark Couch. Critical Component Protection (CCP) Increased Vulnerability Reduction for Rotorcraft. Aircraft Survivability 13 (Fall 2013): 2831. [4] S ayre, Rick. Casualty Assessment and ReductionAt the 5-Year Mark. Aircraft Survivability 13 (Spring 2013): 68. [5] T onnessen, Williamsen, Eusanio, and Volpe, Aircraft Survivability Journal Spring 2007 [6] J oint Capabilities Integration and Development System (JCIDS) Manual. Appendix C, enclosure B. Updated 19 January 2012. [7] T onnessen, AS Journal Spring 2006


PRSRT STD US POSTAGE PAID PAX RIVER MD Permit N o 22 COMMANDER NAVAL AIR SYSTEMS COMMAND (4.1.8J) 47123 BUSE ROAD PATUXENT RIVER, MD 20670-1547Official BusinessCALENDAR OF EVENTS SEPTProgram Review 2325 Sept 2014 Nellis AFB, NVNOVA2/AD Systems and Technology Workshop 46 Nov 2014 Lexington, MA Aircraft Survivability Technical Forum 1214 Nov 2014 Laurel, MD /default.aspx