Research abstracts

National Advisory Committee For Aeronautics



Research Abstracts
NO.48 SEPTEMBER 8, 1953


CURRENT NACA REPORTS

NACA TN 2965

AN ANALYSIS OF NORMAL-ACCELERATION AND
AIRSPEED DATA FROM A FOUR-ENGINE TYPE OF
TRANSPORT AIRPLANE IN COMMERCIAL OPERA-
TION ON AN EASTERN UNITED STATES ROUTE
FROM NOVEMBER 1947 TO FEBRUARY 1950.
Thomas L. Coleman and Paul W. J. Schumacher.
August 1953. 27p. diagrs., 5 tabs. (NACA
TN 2965)

Normal acceleration and airspeed data covering
about 50, 000 hours of flight of one type of four-
engine transport airplane flown in commercial oper-
ations at altitudes to 20,000 feet on a north-south
route in the eastern United States are analyzed to de-
termine the gusts encountered and the accelerations
experienced. Comparisons are made between the
present results and the results previously obtained
from other operations. Effects of airpseed and of
seasons on the gusts and accelerations are indicated.


NACA TN 2984

STUDIES OF THE LATERAL-DIRECTIONAL FLY-
ING QUALITIES OF A TANDEM HELICOPTER IN
FORWARD FLIGHT. Kenneth B. Amer and Robert
J. Tapscott. August 1953. 42p. diagrs., photos.,
tab. (NACA TN 2984)

Results of flight measurements and pilots' opinions of
the forward-flight lateral-directional flying qualities
of a tandem helicopter in several different configura-
tions are compared and analyzed. The conclusions
are presented in the form of desirable flying-qualities
goals applicable to all types of helicopters. Compari-
son between theoretical analyses and experimental
results indicates theory to be a useful tool for study-
ing means of achieving these goals. On the basis of
theoretical analyses, possible practical methods of
achieving these goals in the tandem helicopter are
suggested.


NACA TN 2986

EFFECT OF BLADE-THICKNESS TAPER ON
AXIAL-VELOCITY DISTRIBUTION AT THE
LEADING EDGE OF AN ENTRANCE ROTOR-BLADE
ROW WITH AXIAL INLET, AND THE INFLUENCE
OF THIS DISTRIBUTION ON ALINEMENT OF THE
ROTOR BLADE FOR ZERO ANGLE OF ATTACK
John D. Stanitz. August 1953. 33p. diagrs
(NACA TN 2986)

A method is developed for estimating the effect of
blade-thickness taper on the inlet axial-velocity dis-
tribution of an entrance rotor-blade row with axial


inlet, and the influence of this velocity distribution on
the alinement of the rotor blade for zero effective
angle of attack (that is, zero blade loading at the
nose). This alinement of the blade requires a devia-
tion between the angle of the blade camber line di-
rection at the inlet and the upstream relative flow
direction. The method is developed for compress-
ible and incompressible nonviscous fluids, and re-
sults are presented for incompressible flow into a
plane, two-dimensional cascade and for compress-
ible flow into an entrance rotor-blade row with
tapered blades. It is e for the en-
trance rotor-blade r iil 4; 'tbade taper has
a large effect on t In deviatiloh fe; whereas
compressibility h small effect, eapbi perhaps at
the hub, and the ream relative flow aeclion also
has a small eff 9


NACA TN 2987 \

CHARTS RELATIN HIE % IESSPOE BUCKLING
STRESS OF LONGIT LLY SUPPORTED
PLATES TO THE EFFECTIVE DEFLECTIONAL AND
ROTATIONAL STIFFNESS OF THE SUPPORTS.
Roger A. Anderson and Joseph W. Semonian.
August 1953. 53p. diagrs., 4 labs. INACA
TN 2987)

The stability of a plate under edge compressive
stress is analyzed in terms of the deflectional and
rotational stdffnesses of one or more longitudinal
lines of support between the plate side edges. The
results are presented in the form of charts which
make possible the determination of the compressive
buckling stress of plates supported by members
whose stiffness may or may not be defined by ele-
mentary beam bending and twisting theory but yet
whose effective restraint is amenable to evaluation.
The deflectional and rotational restraint provided by
longitudinal stiffeners and full-depth webs is dis-
cussed, and numerical examples illustrate the
application of the charts to the design of wing struc-
tures


NACA TN 2990

FLIGHT MEASUREMENTS AND ANALYSIS OF HEL-
ICOPTER NORMAL LOAD FACTORS IN MANEU-
VERS F. B Gustafson and Almer D. Crim.
August 1953 29p diagrs photos., 2 tabs
(NACA TN 2990)

Flight tests have been conducted in two single-rotor
helicopters to determine the load factors due to var-
ious maneuvers. A simple theoretical method of es-
timating for new designs the maximum load factor
that can be attained for any given flight condition is
also presented, and the results compared with those
obtained from the flight tests.


* AVAILABLE ON LOAN ONLY.
ADDRESS REQUESTS FOR DOCUMENTS TO NACA, 1724 F ST, NW, WASHINGTON 5,. D C, CITING CODE NUMBER ABOVE EACH TITLE;
THE REPORT TITLE AND AUTHOR
6 29. /30.Z
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NACA
2 RESEARCH ABSTRACTS NO.48


NACA TN 2991

ACCELERATIONS AND PASSENGER HARNESS
LOADS MEASURED IN FULL-SCALE LIGHT-
AIRPLANE CRASHES. A. Martin Elband, Scott H.
Simpkinson and Dugald 0. Black. August 1953.
67p. diagrs., photos. (NACA TN 2991)

Full-scale light-airplane crashes simulating stall-
spin accidents were conducted to determine the de-
celerations to which occupants are exposed and the
resulting harness forces encountered in this type of
accident. Crashes at impact speeds from 42 to 60
miles per hour were studied. The airplanes used
were of the familiar steel-tube, fabric-covered, tan-
dem, two-seat type. In crashes up to an impact
speed of 60 miles per hour, crumpling of the forward
fuselage structure prevented the maximum decelera-
tion at the rear-seat location from exceeding 26 to
33g. This maximum g value appeared independent of
the impact speed. Restraining forces in the seat-
belt shoulder-harness combination reached 5800
pounds. The rear-seat occupant can survive
crashes of the type studied at impact speeds up to 60
miles per hour, if body movement is restrained by
an adequate seat-belt shoulder-harness combina-
tion, so as to prevent injurious contact with obsta-
cles normally present in the cabin. Inwardly
collapsing cabin structure, however, is a potential
hazard in the higher-speed crashes.


NACA TN 3000

STUDIES OF THE USE OF FREON-12 AS A WIND-
TUNNEL TESTING MEDIUM. Albert E. von
Doenhoff, Albert L. Braslow and Milton A.
Schwartzberg. August 1953. 57p. diagrs. (NACA
TN 3000)

A number of studies relating to the use of Freon-12
as a substitute medium for air in aerodynamic
testing have been made. The use of Freon-12 in-
stead of air makes possible large savings in wind-
tunnel drive power. Because of the fact that the
ratio of specific heats is approximately 1. 13 for
Freon-12 as compared with 1. 4 for air, some differ-
ences exist between data obtained in Freon-12 and in
air. Methods for predicting aerodynamic character-
istics of bodies in air from data obtained in Freon-
12, however, have been developed, which provide
substantial agreement in all cases for which compar-
ative data are available. The Freon charging and
recovery system used for the Langley low-
turbulence pressure tunnel is described.


NACA RM E53F19

MEASUREMENT AND ANALYSIS OF TURBULENT
FLOW CONTAINING PERIODIC FLOW FLUCTUA-
TIONS. William R. Mickelsen and James C.
Laurence. August 1953. 45p. diagrs. (NACA
RM E53F19)

Techniques are presented for the measurement of the
energy spectrum of flow fluctuations in both axial and
lateral flow directions. A simple spectrum analysis
is presented by which quantitative distinction may be
made between turbulence and the flow disturbances
associated with sound waves in ducts. Experimental
data are presented which indicate that the energy
spectrum of the turbulence is not affected by periodic


and random sound disturbances outside the frequency
ranges containing the disturbances. Preliminary
measurements are presented that illustrate the effect
of combustion on the approach-stream velocity-
fluctuation spectra in a ram-jet combustor. \


NACA RM L53F16

SOME INFORMATION ON THE STRENGTH OF
THICK-SKIN WINGS WITH MULTIWEB AND MULTI-
POST STABILIZATION. Roger A. Anderson,
Richard A. Pride and Aldie E. Johnson, Jr.
August 1953. 19p. diagrs., 3 tabs. (NACA
RM L53F16)

The preliminary results of strength tests on thick-
skin wing structures are described. Some of the
factors which have a major influence on the buckling
behavior and strength of multiweb and multipost
stiffened construction are illustrated by the data pre-
sented, and the conditions under which a combination
of multiweb and multipost construction may be used
are discussed. Also given are the results of
bending tests on hollow circular-are airfoils.


NACA TM 1335

MOTION OF A CYLINDER UNDER THE SURFACE
OF A HEAVY FLUID. (Dvizhenie tsilindra pod
poverkhnostyu tyazheloi zhidkosti). L. N.
Sretensky. August 1953. 36p. (NACA TM 1335.
Trans. from Central Aero-Hydrodynamical Institute.
Transactions, Rept.346, 1938, p.3-27).

General equations are derived for the approximate
solution of the flow of a heavy infinite depth about a
submerged circular cylinder where the center of the
cylinder is submerged 1.5 diameter or greater.
Then by replacing the cylinder by a dipole of a cer-
tain strength an equation is derived for the wave re-
sistance of a circular cylinder moving in a fluid of
finite depth.



BRITISH REPORTS


N-26059*

Aeronautical Research Council (Gt. Brit.)
THEORETICAL CONSIDERATIONS ON FREE CON-
VECTION IN TUBES. M. J. Lighthill. July 21,
1952. 44p. diagrs. (ARC 15,074; FM 1758)

Methods are developed for predicting the flow and
heat transfer due to free convection in heated verti-
cal tubes, closed at the bottom and opening into a
reservoir of cool fluid at the top. These include
methods of predicting whether the flow is laminar or
turbulent, and whether the boundary layer of heated
fluid fills or does not fill the tube, or fills it with a
stagnant region near the closed end. The theory is
extended to apply to a tube closed at both ends, part
heated and part cooled. There is some discussion of
a mechanical engineering application in which the ex-
ternal force is not gravity but centrifugal.






NACA
RESEARCH ABSTRACTS NO. 48


N-26063,

Aeronautical Research Council (Gt. Brit.)
THE DESIGN OF THIN FINITE WINGS IN INCOM-
PRESSIBLE FLOW. G. J. Hancock. September 2,
1952. 17p. diagrs. (ARC 15,185; FM 1788)

A method is developed for designing thin finite wings
with prescribed lift distributions. Particular
attention is given to wings which, at a certain opti-
mum angle of incidence. have zero loading along the
whole leading edge. It is suggested that such a wing
will have greater range of lift coefficeint for low
drag than other wings with the same plan form. On
the basis of the linearized theory a formula, re-
lating the wing surface to the pressure distribution
over the surface, is deduced which differs from the
usual potential relationship by avoiding the difficulty
of the nonuniform convergence with respect to the
normal distance away from the wing surface
singularities. The surface integral which is de-
veloped includes a regular singularity and a definite
limiting process. Three examples have been
worked out in which the condition of smooth flow at
the leading edee is satisfied.


N-26068'

Aeronautical Research Council (Gt. Brit.)
ON BOUNDARY LAYERS AND UPSTREAM IN-
FLUENCE. U SUPERSONIC FLOW WITHOUT
SEPARATION. M. J. Lighthill. October 23, 1952.
38p. diagrs., tab. (ARC 15, 298; FM 1805a)

This report is concerned with interactions between a
boundary layer and a supersonic main stream which
take place without separation. These arise either
from expansive disturbances, or from relatively
weak compressive disturbances to a turbulent layer.
The analysis may also have value for the study of the
flow upst reanm of separation in interactions with
laminar separation.


N-26070*

Aeronautical Research Council (Gt. Brit.)
ON EDGE TONES AND ASSOCIATED PHENOMENA.
Alan Powell. October 7, 1952. 17p. diagr.,
photos., tab. (ARC 15,333; FM 1809)

The edge-tone phenomena occurring at high jet
speeds have been photographed by the Schlieren
method and the sound waves produced are clearly
visible. They are of opposite phase on each side of
the stream, and microphone traverses have shown
this to be the case at low speeds also. This obser-
vation makes possible an explanation of the mechan-
ism by virtue of the "sensitivity" of the jet, which is
particularly susceptible to this form of acoustic
disturbance whereby the sound waves give rise to
stream disturbances at the jet orifice. Two basic
relationships are given, one connecting the relative
phases of the motion and the other dealing with the
effect e efficiencies of each of the component pro-
cesses.


3


N-26300*

Royal Aircraft Establilshment tGt. Brit.)
SOME REMARKS ON THE CHOICE AND PRESEN-
TATION OF FORMULAE FOR TURBULENT SKIN
FRICTION IN COMPRESSIBLE FLOW. R. J.
Monaghan. May 1953. 13p. (RAE Tech. Note
Aero 2246)

A review of the various formulas which have been
developed for estimating turbulent skin friction in
compressible flow has already been given and is
mainly concerned with the theoretical aspects of the
problem. The object of the present note is to ex-
amine briefly the practical application of the re-
sults obtained. It is suggested that there is now
sufficient evidence to justify changing the com-
pressibility parameter frori Mach number to the
ratio (surface temperature)/(local ambient temper-
ature). The merits of various formulas are dis-
cussed and some brief remarks are made on the ef-
fects of pressure gradients and on the present state
of knowledge concerning transition.


N-26301*

Royal Aircraft Establishment (Gt. Brit.)
AN ELECTRO-HYDRAULIC POWERED FLYING
CONTROL SYSTEM WITH AUTOMATIC SAFE-
GUARDS AND VARIABLE CONTROL CHARACTER-
ISTICS. C. D. Watson. March 1953. 17p.
photos., diagrs. (RAE Tech. Note Mech. Eng. 77)

A standard Lincoln aircraft was fitted with an auto-
pilot and powered flying controls to investigate the
stability conditions of two series connected servo-
mechanisms in an aircraft control system. This
note describes the design and installation of the
electrohydraulic power control units, and the vari-
ous automatic and safety provisions. In addition,
details are given of a variable rate spring feel
system, semiautomatic feel trimming and variable
servocontrol characteristics. To introduce power-
ful threshold damping should sustained oscillations
arise in flight, a divided reset mechanism is in-
corporated, which is also described. Stability
curves show the effect of tuning this mechanism.


N-26302 *

National Gas Turbine Establishment (Gt. Brit.)
THE MEASUREMENT OF TRUE MEAN PRESSURES
AND MACH NUMBERS IN OSCILLATORY FLOW.
M. V. Nesbitt. March 1953. 37p. diagrs.
(NGTE Memo. M. 180)

In this paper, the problem of measuring mean
pressures and Mach numbers under regular oscillat-
ing flow conditions is considered. Firstly, a pa-
rameter is developed which enables the damping or-
ifice and instrument volume to be designed to give
any required variation in pressure in the measur-
ing section. Next the relationship between the
measured mean pressure and true mean pressure is
determined for rectangular, sine, and sawtooth
wave forms and finally the relation between true
mean Mach numbers and Mach numbers as computed
from true mean pressures is determined for rec-
tangular, sine and sawtooth waves :raveling up and
downstream.






UNIVERSITY OF FLORIDA


3 1262 08153 284 7


N-26303*


Aeroplane and Armament Experimental Establish-
ment (Gt. Brit.) THE FORWARD TAKE-OFF OF A
HELICOPTER. F. O'Hara. June 26, 1953. 21p.
diagrs. ,AAEE Res 276)

A theoretical analysis is given of the accelerated
motion of a single rotor helicopter for estimation of
the forward take-off performance. The motion is
considered in stages during which either the disk
attitude to the horizontal or the flight speed is con-
stant. Equations are derived for the motion along
and normal to the flight path and solutions are given
assuming constant mean values for the aerodynamic
forces on the rotor and fuselage. The equations of
motion for constant disk attitude have a simple solu-
tion for motion from rest (and for special initial
conditions) giving a straight flight paih. and a gen-
eral solution giving a curved flight path. The per-
formance at constant speed is considered for a gen-
eral climb away case and also for climb away
approaching steady flight conditions with the thrust
approximately equal to the aircraft weight. For
application of the theory, charts of the various so-
lutions are given covering a representative range of
the variables.


N-26335 *

Royal Aircraft Establishment (Gt. Brit.)
DESIGN CRITERION FOR FATIGUE OF WINGS.
P. B. Walker. May 1953. 16p. diagr., tab.
(RAE Structures 146)

Design criteria for wings are postulated from a
study of past and present knowledge of aircraft
structural fatigue. Earlier criteria are considered
first, and are then followed by new criteria that are
believed to be more appropriated to modern condi-
tions. The main general conclusions are, first,
that design must be based on a fatigue test of critical
components and, secondly, that the conditions for
this test must be derived from a typical gust case
specially devised for fatigue life, followed by sug-
gested adjustments when statistical information is
available concerning the particular operational
conditions.


MISCELLANEOUS





NACA TM 1317

Errata No. 2 on "A SIMPLE NUMERICAL METHOD
FOR THE CALCULATION OF THE LAMINAR
BOUNDARY LAYER." K. Schr5der. April 1952.


NACA
RESEARCH ABSTRACTS NO. 48


UNPUBLISHED PAPERS
"I


N-19474*

Cornell U. Graduate School of Aeronautical Engi-
neering. ON THE LONGITUDINAL STRESS PRO-
PAGATION IN THE PLASTIC RANGE. Kuang-Tao
Hsu, Cornell University. September 1950. vi,
67p. diagrs., photos. (Cornell U. Graduate School
of Aeronautical Engineering)

This report presents a graphical method to solve the
problem of longitudinal wave propagation in the
plastic range and a short summary of the theories
developed by others. The problem of a semi-
infinite plastic bar struck by a rigid mass and that
of a constant force impact on the bar with the mass
attached at its end are investigated. A short inves-
tigation of the experimental method of photoelasticity
applied to impact test is given.


N-24814

Gas Turbine Lab., Mass Inst. of Tech.
LAMINAR AND TURBULENT BOUNDARY LAYERS
IN A ROTATING PIPE. A PRELIMINARY THEO-
RETICAL AND EXPERIMENTAL INVESTIGATION.
Joel S. Isenberg and Alan H. Stenrung. June 1952.
vi, 67p. diagrs., photos. (Gas Turbine Lab.,
Mass. Inst. of Tech)

An analysis is made of the boundary layer which
forms in a straight rotating pipe through wluch a un-
iform incompressible stream of fluid is flowing in
the cases when this layer is entirely laminar or en-
tirely turbulent. The analogous problem of a ro-
tating flow entering a fixed pipe is also analyzed.


NACA-Langley 9-8-53 -4000

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