Results of the crash test of a remotely piloted transport aircraft instrumented to measure a NASA energy-absorbing transport seat are given. Human tolerance limits to acceleration and a dynamic response index model are discussed. It was found that the acceleration levels at the rear of the airplane were quite low and were below the stroking threshold of the NASA EA-seat. Therefore, dummies in the standard and EA-seat responded approximately the same. All longitudinal accelerations were quite low for the primary impact with very low forces measured in the lap belts. The vertical (spineward) acceleration levels measured in the dummies were also relatively low and very survivable from an impact tolerance standpoint. The pilot with an 18 G peak acceleration received by far the highest vertical acceleration and could have possibly received slight spinal injury

Fasanella, E. L.

English

NASA Technical Reports Server

NASA SEAT EXPERIMENT ASD OC(_PANT RESPONSES
E. L. Fasanella
PRC Kentron, Inc.
Aerospace Technologies Division
Hampton, Virginia
NASA/FAA Government/Industry CID Workshop
NASA Langley Research Center
April i0, 1985
79
https://ntrs.nasa.gov/search.jsp?R=19860012468 2020-03-20T14:57:10+00:00Z
NASA EA-SEAT SHOWING INSTRUMENTATION
Figure 1 is a rear view of the NASA energy-absorbing transport seat
showing longitudinal and normal (vertical) accelerometers attached to the
rear tube of the seat structure. This seat was located on the left side of
the aircraft in the rear (body station 1220) at what was designated row 14
in the instrumentation list. On the right side of the aircraft in the same
row, there was placed for c(mparison an unmodified standard seat (NASA
standard seat) of the same basic structure, but without an energy absorbing
tube. Three dtmTnieswere placed in each NASA seat with each center dunm_y
instrumented with accelercmeters and lap belt load cells. The instrumented
dtm_nies in the EA- and standard seat were designated dummies 14B and 14E,
respectively.
The planned crash scenario was for a 17 ft/s sink rate with attitude 1
degree nose up. For this scenario, the rear section of the aircraft near
the two NASA seats would impact the ground first, generating a vertical
pulse that was expected to cause the energy absorbers to stroke and to
provide a comparison between an unmodified standard and an EA-seat.
Two unfortunate events prevented a good comparison: I) The roll of
the aircraft caused wing impact which reduced the vertical velocity and
caused the nose to be the first part of the fuselage to impact the ground;
2) A pool fire developed in the rear of the aircraft and both seats were
totally consumed by the fire.
Right rear leg
Acceterometers
Figure 1
8O
S_ HUMAN TOLERANCE TO HEADWARD ACCELERATIONS
Figure 2 sun_Tarizesseated human tolerance limits to acceleration along
the spinal direction with the stopping force pointed t_ard the head.
Accelerations along the longitudinal direction will not be discussed because
the CID accelerations were very low in the longitudinal direction. In
addition, the human body can withstand greater acceleration in the
longitudinal direction. Human tolerance is a subject that creates a lot of
controversy, even among the experts. Human subjects cannot be used to
determine permanent injury levels, and the accelerations and durations from
accident data are only estimated. Well-restrained volunteers have mapped
out non-injurious acceleration levels and durations as shown in the figure.
Human surrogates such as hogs and chimpanzees have been used to establish
estimated human severe injury levels.
In the CID crash, the acceleration levels were low but of relatively
long duration. Many pulses exceeded 0.1 seconds and sane were of nearly 0.2
second duration. Most of the voluntary exposure was for durations less than
0.I seconds.
Subject
o Human ,j
......................... Human t
200 - ,_?_ii_i,.:,,,,,,_:.:iil,;:i_:_::.... [] Ho£1 .
\_iiiii_;;S_;_;_._._;i_;!_;_;_!;;_i_i_!_;_:_:_;_;........ All survivable exposures
\ _'_;:i_beve_e Injuryiiiii_i_:_::;;::_,.... Max bodysupportin all cases
Uniform \ Moderateinju ry :::::::'_i_i_i_:_i_'_iii_iiiiiii_i_iAcceleration
- -__Limited to
of Vehicle,G _ ,,,,: ,,,,, ,,,:,_, _ _crashworthyseat ^^"""ff"d"
10 :_::'_Voluntary...........................................................humanexposure_ performance.... IVI_ILJIII U _ ?
_::!(uninjured,undebilitated) iiii'_iiiii_::,;_,!_;,_ uural°nT,_._._'
=i_i_..................................................................................;!iiii ____/
_ tO t1 t2 t3
Time,,,I,I1 I I II!IIII I I IIIII_I _ _ Illll_l
.001 .005 .01 .05 .1 .5 1 5 10
Duration of Uniform Acceleration,sec
Figure 2
81
DRI MODe,
The Dynamic Response Index (DRI) model (ref. i) was developed by the
Air Force as an aid for studying injury to pilots who had ejected from high-
speed aircraft and for specifying ejection seat performance. In this model,
mass M is the upper torso mass, K is the spinal stiffness, and C is the
spinal damping constant. The acceleration input (Z) forces the upper body
and is generally taken to be the "vertical" seat pan acceleration for the
Air Force ejection seat. For our purposes, the normal pelvis acceleration
will be used since it is located directly above the seat pan and is the
acceleration input that is forcing the upper body mass. Omega is 2 pi times
the natural frequency. The equation in figure 3 is simply the equation for
a forced simple harmonic oscillator. The DRI can be shown to be the maximum
output acceleration of the mass M driven by forcing acceleration Z.
The plot on the left shows spinal injury rate as a function of DRI from
cadaver (solid line) and from emergency ejections (dashed line).
50- /
40 - Operationaldata//
30- Cadaverdat_/ / I I
/ m
2
Spinal / 6 c k5 - //0injury
rate,% 2-i_ _)X/_)/0 z
.5- _ d26 + 2CWn d6 +w 26 = z2 --{- n
• dt2
w = 52.9 radlsecn
I I I I I I I
c = O.22410 12 14 16 18 20 22 24
Dynamicresponseindex
Figure 3
82
NASA EA-SEAT PERFORMANCE
In figure 4 the dummy (14B) pelvis normal acceleration (along the
spine) for the primary ground impact (wing cutter data not considered) is
compared to the EA-seat normal (to floor) acceleration. Notice that the
dt_my pelvis acceleration follows the EA-seat acceleration rather closely
except that it lags slightly in time. Also note that the peak acceleration
is less than four G's, with the average acceleration down in the 1 to 2 G
range and with durations approaching 0.2 seconds. Referring to figure 2,
one can see that these levels are quite low and in the non-injurious range.
This seat was designed to begin stroking for a normal input acceleration of
approximately 8-10 G's. Since the input acceleration is well below that
value, the graphite/epoxy energy-absorber would act as a solid member with
no stroking.
B
o
Accel,-I- i ,,, ' ' ._
w
G -2-
-3- ___EAseatN Dummypelvis N
-4-
-.5 I I I I I I i I I I
0 .I .2 .3 .4 .5 .6 .7 .8 .9 1.0
33731.00 Time, sec
Figure 4
83
NASA STAhDARD SEAT PERFORMANCE
Figure 5 uses the same format as figure 4 except that the NASA standard
seat and d_mmy 14E pelvis accelerations are compared. Notice that the
normal dummy pelvis acceleration in the standard seat also follows the seat
normal acceleration quite closely except for some time lag. Since the input
pulse was below the stroking level for the EA-seat, both seats and both
instrumented duchies experienced comparable acceleration pulses.
31 I----3
Accel, 1G , , tl i % II I
-2- %;Seat Nj'¢
I
-3 - L_Dummy14Epelvis N L:
-4--
-5 : l I I I I 1 I I I I
0 .I .2 .3 .4 .5 .6 .7 .8 .9 1.0
33731.00 Time, sec
Figure 5
84
PILOT PELVIS ACCELERATION AhD CONTINUOUS DRI
The dummy pilot received the highest normal (spineward) acceleration
because the pitch rate i_parted by the wing impact caused the aircraft nose
to hit first with the highest vertical velocity. Figure 6 shows that the
pilot normal pelvis acceleration peaked at 18.3 G's with base duration of
about 0.07 seconds. The average acceleration over the 0.07 seconds is about
i0 G's. In addition, the continuous DRI was plotted using the pelvis
acceleration as the forcing acceleration. The peak DRI lags the input and
slightly exceeds it at 19.8. By comparing the peak and average acceleration
for 0.07 seconds with the curve in figure 2, one can see that the
acceleration borders the moderate injury range. Referring to figure 3, a
DRI value of 19.8, would indicate a 10-percent chance of spinal injury.
25-
DRI= 19.82
Pilot _1
15 - pelvi_iN
DRI 5 - .\ 'l l I I _ ,-
| I
-_ -- I !
_.--- Continuous DRI
-15 I I I I
0 .25 .50 .75 1.O0
Time, sec
Figure 6
85
CID PLAN VI_
Figure 7 is used to show the location of the various seats in the
aircraft. The NASA EA- and standard seats were located at body station 1220
which is the 14 th row of seats. The pilot seat is considered row 1 and the
attendant's seat near the main door is row 2. The seats at body station
(BS) 540 are row 3 etc. The x-coordinate in inches measured from the nose
is also given. (For example, the x-coordinate for body station 540 is 410
inches from origin at the nose. )
m Battery pallet [DAS] /
// /
I_PowerpalletEcamera/lights] / /
= Flightrecorder _/-_--_/
z_Camera and range [10 locations] Ir_"/ /,_7 /.'// _-_-C,osets/7-Restr°°m
Galley_ vGalley door /// / /Service \_- //_
Restroo-m-_.\. //" / L dOOr-',l\ /// /
I I Flight
_S/Pi/o_ _ j,. "_,--- B!S_ ( B'S Zi,_._ .,__'_,."--_F_gr_ers1 20 \ \ 1220,.,.,,,uoo,
i . :3q0 x _ i
;x" main\ _4u .___..._ \\ x
n n ooor x L75-"^^"-' " " '=0,..-.----L--.._III0
""" 410 '_"
\ \\
4 Lights[camera] _]Flightattendantseats
FAA seats []Data acquisition sys. pallet
NASA seats [] Taperecorder pallet
Figure 7
86
DUMMY OC(_/PANTRESPONSE, DRI VERSUS DUMMY LOCATION
The d_y DRI was calculated for each instrumented dummy with good data
traces and plotted versus the aircraft x-coordinate. The pilot was the only
occupant that received a moderate acceleration. All of the other dLm_nies
received mild non-injurious accelerations. The number in front of each data
point is the row number. The letter refers to the location from left to
right with A being the far left seating position and F being the far right
seating position. All instrumented dLm_nieswere located in the center
position of each triple seat, thus they are in locations B and E (fig. 8).
24-
20 [] Pilot
16
DRI 12
8 5B3E[] D 9B 12B
5EO [] [] [] 14E
rn o
4 - 7B 9E 12E 14B
, I , I I I , I i I I I
O 200 400 600 800 1000 1200
X-coordinate, in.
Figure 8
87
SUMMARY
In s_mary (fig. 9), the acceleration levels at the rear of the
airplane were quite low and were below the stroking threshold of the NASA
EA-seat. Therefore, d_ies in the standard and EA-seat responded
approximately the same.
All longitudinal accelerations were quite low for the primary impact
with very low forces measured in the lap belts. The vertical (spineward)
acceleration levels measured in the d_ies were also relatively low and
very survivable from an impact tolerance standpoint. The pilot with an 18 G
peak acceleration received by far the highest vertical acceleration and
could have possibly received slight spinal injury.
• Acceleration level belowstroking threshold for NASAEA seat
• Acceleration levels measuredin dummieswere relatively low
• Very survivable from human impacttolerances
standpoint
• Pilot receivedabout 18 6's, the highest measured
• Injury criteria
• Pilot had chanceof receiving spinal injury
Figure 9
88
REFERENCES
I. Brinkley, James W. ; and Shaffer, John T. : Dynamic Simulation Techniques
for the Design of Escape Syst_ns: Current Applications and Future Air
Force Requirements. AMRL-TR-71-29, Paper No. 2, U.S. Air Force, Dec.
1971. (Available from DTIC as AD 740439.)
2. Military Specification, MIL-S-9479: Seat System, Upward Ejection,
Aircraft, General Specification For. Department of Defense,
Washington, D.C., March 1971.
89


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