the TSO. The steep slide angles produced by the
sandbag toboggan modeled well the steep angles
produced by the human toboggan, and an added
benefit provided by the sandbag toboggan test is
the ability to answer the same questions about
beam strength that the sandbag drop test had
been designed to address. This proves to be a
very cost-beneficial solution.

The range of effects demonstrated with the
sandbag toboggan test also suggests that the test
is sensitive to current (state-of-the-art) inflatable
slide design and performance characteristics. For
example, the slight slide beam under-inflation
and attendant softening of the sliding surface
employed with 2 of the dual lane slides produced
so-called test failures. These effects did not occur
for 1 of the escape slides after it was fully
inflated; however, the other slide continued to
perform poorly when fully inflated, suggesting
that it could benefit from additional inflation
design pressure or other beam strengthening
measures. Thus, the sandbag toboggan test, as
currently conceived, effectively addressed both
of the original beam strength questions, without
the hazards associated with its earlier human-
subjects form.

The sandbag drop test also proved to be a
forcible test of escape slide beam strength, as
almost all of the escape slides bent severely when
assaulted by the bag. However, none of the
slides displayed any tendency to collapse
permanently, or rupture, and the slides were
designed with the sliding surface suspended from
the top of the lower inflatable beams (as is
typical), which prevented any of the sliding sur-
faces from contacting the ground. The single-
lane slides were more sensitive to the drop tests,
as they had fewer beams to distribute the load,
although there was never a case in which a slide
failed to regain its original configuration. The
dual-lane slides were more impervious to the
drop tests, maintaining their configurations
much better. Attempts to make the test brutal
enough to produce some sort of failure demand-
ed both weights and drop heights well outside
the range of normal operations. This circum-

stance, combined with the ability of the sandbag
toboggan to pose essentially the same question,
led to the conclusion that the sandbag drop test
could be abandoned.

In conclusion, and in response to these find-
ings, proposed revisions to TSO-C69b to address
inflatable escape slide beam strength could incor-
porate the sandbag toboggan test to advantage.
Its methodology would include the use of a
sandbag(s) toboggan weighing 510 pounds, distri-
buted across an area not to exceed 7.5 feet long
by 2 feet wide, delivered by a ramp or other in-
clined plane located at the top of the slide so as
not to propel the toboggan by other than grav-
ity. For multiple lane escape slides, sandbag to-
boggans should be delivered simultaneously to
all sliding lanes. To be successful, all the sand-
bags comprising the toboggan, if more than one,
to reach the ground at the toe end of the slide,
except in the case of a multiple sandbag tobog-
gan, where one bag may be resting on top of
previously delivered bags and where it would
have reached the ground if not for its impedi-
ment by the other bags already on the ground.

GIRT STRENGTH TESTS

The original girt strength tests in the TSO
were designed to assure that the slide attachment
to the aircraft would support the in-use loads
expected. One, the 1050 Ib static girt loading
test, was designed to assure that heavy symme-
trical loads could be handled, and the other, a 25-
knot wind lateral girt loading test, was designed
to assure that asymmetrical loads produced by
side-winds did not cause the girt to shear. The 2
new protocols were developed to replace the
original tests with more cost- and time- effective
methods that employ a tensile test machine to
produce analogous symmetrical and asymmetri-
cal girt loading forces.

In both of the new test protocols, girt
specimens were mounted in a tensile test
machine and stretched according to the type of
loading being considered. For each test a girt was
attached to 1 end of the test fixture, using the


ACKNOWLEDGMENTS

The authors thank the many participants of the FAA Aviation Rulemaking Advisory Committee’s
Performance Standards Working Group who worked diligently in support of this project. Special thanks
go to Mr. Tom Anderson of BFGoodrich Aerospace, and Mr. Ed Smialowicz of Air Cruisers Company,

for providing the array of escape slide test articles used in the study.


CONCLUSION

Tests of inflatable escape slide beam and girt
strength have been developed to assure that
current and future inflatable escape slides
perform as intended during emergency aircraft
evacuations. The beam strength tests resulted
from the studied use of human test subjects in
comparison with non-human test methodologies
designed to mimic slide use by humans. Of
particular interest was the ability to properly
assess beam strength without the potential for
injury of human test subjects. The girt strength
tests were designed to imitate loads resulting
both from evacuee usage during evacuations and
the application of asymmetrical forces created by
lateral winds. Also of interest was the ability to
create test methods that could be applied in a
tensile test machine to improve the reliability of
test results, while reducing the need for full scale
tests.

The results of the test development program
indicate that the resultant beam and girt strength
tests provide robust measures of the quality of
inflatable escape slides, and that inflatable escape
slides manufactured to conform with these re-
quirements should provide aircraft evacuees with
a worthy means of emergency egress. Incorpo-
rating these tests in any revision of TSO-C69
would be a satisfactory approach to addressing
the inflatable escape slide beam and girt strength
issues during the manufacturing and certification
process.

13

REFERENCE

Technical Standard Order (TSO) Cé69b,
Emergency Evacuation Slides, Ramps, and
Slide/Raft_ Combinations, Department of
Transportation, Federal Aviation Administra-
tion, Office of Airworthiness, Washington, D.C,
August 18, 1988.

CUS. GOVERNMENT PRINTING OFFICE: 1998 -660-088/60056


Figure 2
Sandbag Drop Test

was used in a few confirmatory trials. Also,
rather than pushing the bags out of the door as
before, an adjustable-height, Formica® covered
ramp, capable of holding up to 4 sandbags per
lane, was positioned inside the aircraft to deliver
the bags. This change was intended to reduce the
workload of the research team, as well as stand-
ardize sandbag delivery. Once loaded with the
correct number of bags, the ramp was raised
until the bags began to slowly creep, unaided,
onto the escape slide. The choice of 3 sandbags
per lane, or 3 bags with a trailer, was also varied
to allow comparisons with the earlier results.
Tables 1 and 2 show the results of the tests.

Sandbag Drop Tests.

The sandbag drop test was conducted on all
of the single lane slides, but none of the dual lane

slides. This dichotomy was based on the results
from the earlier preliminary tests, where it ap-
peared that the sandbag toboggan test was a
more powerful indicator of slide rebound cap-
ability, especially for dual lane slides. This ap-
proach was substantiated by the results of the
subsequent sandbag toboggan tests on the single
lane slides, which were shown to bend severely
under the heavier 510 Ib. load, but recover
adequately to allow the sandbags to continue to
the ground. The drop test methods were identi-
cal to those used in the earlier preliminary tests,
ie., a 250 pound sandbag was dropped onto the
center of the sliding lane. The height of the bag
was varied, as before, for comparisons with the
results obtained in the preliminary trials. Table 3
displays the single lane sandbag drop test con-
ditions and results.


The success criteria required that the girt,
and its attachments to the test machine and the
inflatable portion of the escape slide, withstand
pulls pertinent to the in-use loading forces to
which the girts would be exposed. Such loading
forces would be determined via instrumentation
attached to the girt and/or escape slide during
the other usage-rate and loading tests required by
the TSO.

BEAM STRENGTH TESTS

Beam strength test options were explored,
using both single-lane and dual-lane A330/340
escape slides erected at nominal doorsill heights,
in preparation for a larger test series involving an
array of inflatable escape slides representative of
those in use throughout the transport airplane
industry. The goal was to fine-tune the test
methodology, and its systematic application by
the research team, to provide tests of inflatable
escape slide beam and girt strength that were
severe, but representative of what escape slides
might encounter during an emergency evacua-
tion. Accordingly, both the beam strength tests
and their respective success criteria were modi-
fied during the test development program. Test-
ing of the additional slides was intended to
address the range of slide designs currently in use
aboard transport category aircraft, thereby al-
lowing broader generalization of the findings to
current, as well as newly proposed, inflatable
escape slide designs.

Preliminary Dynamic Loading Tests

The initial dynamic loading tests were
conducted on an A330/340 single-lane slide and
a dual-lane slide/raft, both inflated to pop-off
pressure, using U.S. Air Force personnel attend-
ing an aircraft evacuation training class at
CAML. These trainees were physically fit adult
males and females in their 20s and 30s. The tests
were designed to evaluate only the proper
configuration of the human toboggan, which
was formed by seating the trainees closely

together, single-file at the doorsill, in the center
of the sliding lane(s). At the go command, they
pushed off in unison, moving as a unit down the
slide (Fig. 1).

Depending on the specific trial, either 2 or 3
persons were employed to form the toboggan.
Different combinations of trainees were used to
achieve toboggan weights ranging from 350 to
580 pounds; this provided assessments of the
toboggan weight that would be most appro-
priate. It quickly became apparent that the
original 510 pounds per sliding lane was essen-
tially optimum; however, it was also discovered
that almost all of the toboggans produced nearly
vertical slide angles during the test. This defor-
mation of the escape slide was so severe at the
heavier toboggan weights that questions imme-
diately arose about the likelihood of injury to
the 10 subsequent sliders who were supposed to
follow the toboggan down the slide during the
test.

Discussions among the team members about
this likelihood of injury resulted in an agreement
to develop a sandbag toboggan test that would
simulate the human toboggan test and achieve
comparable results. Development of this sandbag
toboggan test centered on the number, weight,
and configuration of the sandbags, as well as
elaboration of a sandbag delivery system. All
other factors remained the same.

The new tests were conducted with tobog-
gans made of 2 or 3 sandbags, each weighing 150,
200, or 250 pounds, tied together by 1-foot
ropes. The toboggans weighed between 400 and
600 pounds. In addition, a fourth bag weighing
200 pounds was also employed in some tests. It
was tied with either a 1-foot rope to form a 4-bag
toboggan or tethered with a 3-foot rope to the
last bag in the toboggan as a trailer, to simulate a
person jumping onto the slide 1 second after the
toboggan was launched. The tests started with
the bags being placed at the top of the slide at
the doorsill; they were then pushed as gently as
possible out of the door and allowed to be
gravity-fed down the slide.


Inflatable Escape Slide Beam and Girt Strength Tests:
Support for Revision of Technical Standard Order C-69b

INTRODUCTION

Minimum design and performance standards
for aircraft inflatable escape slides are defined in
Technical Standard Order (TSO) C-69. These
criteria have evolved over the years, as new ma-
terials and manufacturing methods have been
developed. Many of the evolutionary changes
have resulted from the need to accommodate
ever larger aircraft and passenger loads, and from
lessons learned during aircraft evacuations. As
the state-of-the-art evolves, advances in inflatable
escape slide technology are codified in TSO-C69
to assure that future inflatable escape slide
designs are worthy.

Owing to inflatable beam strength problems
evidenced by escape slide buckling in a recent
full-scale aircraft evacuation certification demon-
stration, the Performance Standards Working
Group (PSWG) of the FAA’s Aviation Rule-
making Advisory Committee (ARAC) was task-
ed to develop upgraded inflatable slide beam and
slide-to-aircraft attachment means (girt) strength
test procedures for use in the development and
certification of inflatable escape slides. In re-
sponse to this charge, the PSWG requested,
through the FAA Aircraft Certification Service
(AIR3), that a research project be conducted by
the FAA Civil Aeromedical Institute (CAMI) to
develop new inflatable escape slide beam and girt
strength test procedures and success criteria for
inclusion in a future revision of TSO C-69.

Discussions aimed toward establishing pro-
per test protocols were held between the PSWG
TSO-C69 task team and members of the CAMI
Cabin Safety Research Team. Two dynamic
beam strength test protocols were initially
suggested: 1) an escape slide loading test, in
which each lane of the slide is boarded and
utilized toboggan style by 3 persons weighing a
combined total of not less than 510 pounds,
followed by additional human sliders immedi-

ately boarding and utilizing the slide at 1-per-
second intervals for the succeeding 10 seconds,
and 2) a sandbag drop test, in which one 250 Ib.
sandbag per slide lane is dropped to measure
potential slide collapse or rupture. The latter test
is also designed to determine whether such a
concentrated load would cause the sliding surface
to impact the ground. For both beam strength
tests the escape slides were to be inflated to pop-
off pressure, as determined by the individual es-
cape slide pressure-relief valve(s).

The success criteria for the toboggan test
were based on the ability of the escape slide to
regain its original shape after dynamic loading
by the human toboggan, so as not to form a cup
in the sliding surface that would impede the
toboggan participants, or subsequent individual
sliders, from exiting the slide. The success cri-
teria for the drop test required the escape slide,
after bending under the weight of the sandbag,
to remain intact, recover its original config-
uration, and deliver the sandbag to the ground.

The original girt strength tests in the TSO
were designed to assure that the attachment
point of the slide to the aircraft would support
the in-use loads expected. These tests included: 1)
a 1050 Ib. static loading of the girt, produced by
placing sandbags on the escape slide erected to
nominal doorsill height, or an angle not greater
than 30°, and 2) a lateral loading of the girt,
produced by a 25-knot wind directed horizon-
tally, parallel to the ground, against the side of
the escape slide longitudinal beam. These tests
produced symmetrical and asymmetrical girt
loading forces. Two new protocols, designed to
replace the original tests, were proposed for the
attachment means (girt) strength tests; these also
included symmetrical and asymmetrical girt
loading forces. In both of the new test protocols,
girt specimens were to be mounted in a tensile
test machine and pulled according to the type of
loading force being considered.




Preliminary Sandbag Drop Tests

The sandbag drop test appeared initially to
be fairly well conceived. Again the A330/340
slide and slide/raft inflated to pop-off pressure
were tested by sandbags weighing 150, 200, and
250 pounds. The bags were hoisted above the
center of the sliding lane and positioned with the
bottom of the bags at doorsill height. The bag
landing site was chosen by rational analysis to be
the location most susceptible (likely to collapse,
rupture, or produce contact of the sliding surface
with the ground) to a cannonball type of jump;
the spot was selected for its lack of cross beams,
stringer supports, etc., that would strengthen the
slide at a particular location. This resulted in the
landing site being located along the centerline of
the sliding lane surface between the doorsill and
a point in the plane of the aircraft floor about 6
feet outside the exit opening (see Figure 2).

Results from the initial sandbag drop tests
showed that all 3 bag weights produced
significant deformation (buckling) of the single
lane slide, although the slides rebounded quickly
to transport the sandbags to the ground. The
sliding surfaces remained well above the ground.
The dual lane slide proved more robust to the
challenge of the weights; i.e., there was minimal
bending and the bags easily traveled down and
off the end of the sliding surface. Given these
results, and considering that the initial center of
gravity for a person jumping onto the slide
would be about 3 feet above the doorsill, the
height of the sandbag bottom was increased to 3
feet above doorsill height for the next series of
sandbag drop tests.

Positioning the sandbags 3 feet above the
doorsill height proved to be much more
stringent than necessary. The single lane escape
slide buckled severely, and more quickly,
reaching essentially vertical angles for all 3
sandbag weights. The rebound was nearly as
quick, however, and the sandbags cleared the
end of the slides as before. The dual lane slide
functioned similarly, reacting more severely than

with the doorsill-height sandbag drops, but it al-
so recovered easily to transport the sandbags to
the ground. Neither sliding surface came close to
contacting the ground.

Analysis and discussions about the utility of
this test, relative to the findings from the orig-
inal sandbag drop test, led to the conclusion that
this form of the sandbag drop test did not offer a
measure of slide strength that was representative
of a singular maximum anticipated load. A
return of the sandbag bottom to doorsill height
was considered more appropriate, although the
sandbag toboggan tests were beginning to appear
better at providing data about recoverability of
escape slide shape and function after severe
loading. A decision was made to formally com-
pare the 2 procedures early in the next test
series.

Application To Other Slides

The slides chosen for the tests were repre-
sentative of a range of inflatable escape slide
designs currently in use in the transport category
airplane fleet, as well as a prototype under de-
velopment. Four single lane slides were tested;
these included a DC-8, a B-737, an MD-80, and
the prototype B-737 slide. One slide each from a
B-747, a B-767, and a B-777 aircraft formed the
dual lane slide sample. All but one of the sand-
bag tests were conducted using the CAMI single-
aisle Aircraft Cabin Evacuation Facility raised to
the nominal doorsill height appropriate for the
individual slide being used in the test. The final
test was conducted using the B-747 slide attached
to its normal Door-5 position on the CAMI
B-747 Aircraft Cabin Evacuation Facility.

Sandbag Toboggan Tests

The sandbag toboggan tests were conducted
as in the preliminary trials. Based on the findings
of the first test series, the weight of the sandbags
was set at 170 pounds per bag for the toboggan
weights (510 pounds total); a 200 pound trailer


DOT/FAA/AM-98/3 Inflatable Escape Slide Beam and

Girt Strength Tests: Support for
Office of Aviation Medicine Revision of Technical Standard
Washington, D.C. 20591 Order (TSO) C-69b

Garnet A. McLean
David A. Palmerton
Charles B. Chittum
Mark H. George
Gordon E. Funkhouser

Civil Aeromedical Institute
Federal Aviation Administration
Oklahoma City, Oklahoma 73125

February 1998

Final Report

This document is available to the public
through the National Technical Information
Service, Springfield, Virginia, 22161

2Q

U.S. Department
of Transportation

Federal Aviation
Administration


Table 2

Sandbag Toboggan Tests on Dual Lane Slides

Aircraft |Test} Sill | Slide | Sliding Test Results
Type Height|Length| Angle Condition
B-747 1 | 16.9 | 32.3 31 +=|Three 170 Ib. bags} All bags traveled straight
feet | feet |degrees|per lane tied 1 ft.| down the slide, but the trailer
lapart toboggan style|didn’t touch the slide until 8 ft.
with 4th 200 Ib. bag] from the toe end. The slide
las trailer in right} cupped and all the bags
lane. (Slide appeared stayed on the slide.
under-inflated)*
2 | 16.9 | 32.3 31 Three 170 LB bags | All bags traveled straight
feet | feet |degrees} per lane tied 1 ft. | down the slide, but the slide
apart toboggan style.| cupped, preventing the bags
(Tension straps from reaching the ground.
loose).
B-767 1 | 14.5 | 24.5 36 Three 170 Ib. bags | The bags slid well. Slide bent
feet | feet |degrees} per lane tied 1 ft. | severely, sprang back, bags
apart toboggan style.| bounced onto the ground.
B-777 1 | 15.6 | 34.2 27 Three 170 LB bags | The 3 bags in the left lane
feet | feet |degrees| per lane tied 1 ft. slid into the right lane. The
apart toboggan style.| slide twisted some, but did
(Slide appeared not bend. Only 3 of the 6
under-inflated)* bags slid off the slide.
2 | 156 | 34.2 27 Three 170 LB bags Two bags in the left lane
feet | feet |degrees| per lane tied 1 ft. | drifted right, but all bags slid
apart toboggan style. off the end.

* Slide was re-inflated for test 2.

Discussion

The goal of this research was to develop tests
of transport category aircraft inflatable escape
slides that would assure sufficient inflatable
beam strength to prevent the sliding surface
from cupping and trapping evacuees on the toe
end of the slide. The original tests were
conceived to assess this capability by: 1) dynamic

Loading of the slide by a toboggan of people
entering the slide, which would be followed
immediately by other persons entering the slide
at a 1-per-second flow rate, and 2) the dropping
of a large sandbag onto the sliding surface at a
point deemed critical for causing collapse,
rupture, or contact of the sliding surface with
the ground. These 2 approaches were considered
to model the most likely assaults that evacuees


Table 1

Sandbag Toboggan Tests on Single Lane Slides

Aircraft |Test| Sill | Slide | Sliding Test Results
Type Height |Length| Angle Condition
DC-8 1 10.5 | 15.4 43  |Three 170 Ib. bags] First 3 bags slid together, but
feet feet |degrees|tied 1 ft. apart to-| 4th bag failed to touch slide
boggan style with] and landed on the other 3. All
4th 200 Ib. bag as| bags bounced off slide.
trailer.
2 10.5 | 15.4 43  |Three 170 LB bags} All bags slid well, but 3rd bag
feet | feet |degrees| tied 1 ft. apart to- was pulled off the sliding
boggan style. 4th | surface, landing on the first
bag pushed out two. The 4th bag had little
while toboggan effect on the slide and
was sliding. bounced off the end.
B-737 1 8.5 15.5 33 | Three 170 Ib. bags | The bags slid well, as the first
feet feet |degrees| tied 1ft. apart |2 pulled the 3rd one out fast.
toboggan style. The slide bent slightly.
2 8.5 15.5 33 | Three 170 Ib. bags | First 3 bags slid together, but
feet | feet |degrees| tied 1 ft. apart to- | 4th bag landed 7 ft down the
boggan style with | slide. All bags slid off the end
4th 200 Ib. bag as of the slide.
trailer.
MD-80 1 8.5 12.5 44 |Three 170 lb. bags} First 2 bags pulled the 3rd
feet feet |degrees| tied 1 ft. apart bag hard onto the middle of
toboggan style the slide. All bags bounced
off the end.
2 8.5 12.5 44 |Three 170 Ib. bags | First 3 bags slid together, but
feet feet |degrees| tied 1 ft. apart to- | 4th bag failed to touch slide
boggan style with | and landed on the other 3. All
4th 200 Ib. bag as bags bounced off slide.
trailer.
Prototype] 1 8.5 | 16.75 31 Three 170 Ib. bags} All bags slid down smoothly,
B-737 feet feet |degrees| tied 1 ft. apart but the slide bent 4 ft. from

toboggan style.

the end, keeping the bags
from sliding off.



Figure 1
Human Subjects Toboggan

The results of this exercise indicated that the
sandbag toboggan functioned essentially like the
human toboggan. The deformations of the slide
appeared essentially identical to those produced
by the trainees in the first series of tests, inclu-
ding increased difficulty in exiting the slide at
the higher toboggan weights. This effect was
caused by more severe cupping of the sliding
surface near the bottom of the slide, which effec-
tively raised the toe-end cross beam to a position
that could not be easily traversed.

Use of the sandbags with a trailer was
plagued with difficulties. Typically, the steep
vertical angle produced by the deformation of
the slide allowed the trailer to fly past the last
bag of the toboggan and land on the ground after
minimal contact with the sliding surface. When
using both the toboggan with the trailer and the
4-bag toboggan, the bags often piled up together
on the slide at the toe end. This occurred not
only because of the slide surface cupping de-
scribed above, but also because the toe-end cross

beam was generally not tall enough, relative to
any sandbags already on the ground, for the
remaining bags to exit the slide. After much
discussion, the use of 3 sandbags with the trailer
and/or the 4-sandbag toboggan was deemed in-
appropriate, given that the success criteria for
this test required that all of the sandbags end
their descent at the end of the slide on the
ground.

Although the replacement of the human
toboggan test with the sandbag test, especially
without trailers, eliminated the ability to assess
slide use at a 1-per-second flow rate immediately
after severe loading, the sandbag toboggan test,
as conceived, allowed robust testing of escape
slide beam strength. The ability to adjust the
weight of the sandbags provided finer discrimi-
nation of the loads that the slide beams could
withstand, and the inability of the sandbags to
help in getting off the slide provided a standard-
ization that could generally not be achieved with
human test subjects.




girt bar attachment typical of installations on the
aircraft; the fabric attachment end of the girt was
connected to a steel plate drilled to accept the
typical girt-to-slide-fabric lacing. The steel plate
was anchored to the other end of the test fixture
by a mechanical arm positioned to pro-vide
symmetrical or asymmetrical tension on the girt.
This increasing tension was provided by
hydraulic cylinders that forced the girt bar at-
tachment point to move away from the girt-to-
slide-fabric lacing joint at a rate of 0.5 inches per
second. A load cell placed in the mechanical arm
measured the amount of force being applied (see
Figures 3 and 4).

The girt loading tests were conducted using
worn-out single-lane B-737 girt specimens. The
specimens were chosen both for their ready
availability and their expected susceptibility to
variable tearing loads and locations. The expecta-
tion of variability in loading and tearing location
was based on the frayed condition that many of
the specimens exhibited. Because of the dual girt-
to-slide-fabric attachment layers that comprise
the B-737 girt, and because all girt specimens
were subsequently shown to tear exclusively at
the fabric lacing joint of each attachment layer,
each girt specimen provided 2 test trials.

The results of the girt loading tests proved to
be more consistent than originally expected. In
the symmetrical loading test trials the initial
loading force peaks, indicative of the point at
which the girt began to tear, were grouped
tightly (see Figure 5). Subsequent force peaks
and troughs in Figure 5 show secondary tearing
of the girt lacing joint. These test data indicate
that the symmetrical girt loading test can
provide reliable, reproducible data concerning
the ability of girt attachments to withstand load-
ing forces typical of emergency usage. The asym-
metrical test data were also generally consistent,
although the initial loading force peaks were
about half as large as those found in the
symmetrical girt loading tests. This resulted
from the more concentrated loading, and subse-
quently easier tearing, of the girts caused by the

10

asymmetric mechanical-arm-to-steel-plate point
of attachment near the outer edge of the girt.
The initial loading force peaks were also follow-
ed by secondary tearing force peaks and troughs
(see Figure 6).

Discussion

Together, these tests provide the qualitative
and quantitative findings relative to girt strength
that were being sought. The symmetrical loading
test provided forces greater than the original
1050 Ib static sandbag loading test, and the
amount of force applied by the asymmetrical
loading test exceeded the 360 lb loading force
computed for a girt attached to its B-737 slide
being exposed to a 25-knot steady-state lateral
wind. These positive test attributes were aug-
mented by an enhanced cost-benefits equation
(relative to the original test methods) allowed by
the ease of test execution, as well as lesser
requirements for personnel and test apparatus.

The application of these mildly dynamic test
methods in the current study was intended to
challenge the girt specimens until girt failure was
achieved. No relevant force requirements had
been predetermined as pass/fail criteria. In con-
trast, application of the test methodology to the
design and manufacture of current and future
generation girts could use purely static loading
forces designed to model the actual in-use and
special conditions loads to which specific slide
and slide/raft girts would be exposed. Predeter-
mination of the loading forces through instru-
mentation attached to the girt during other rate
and loading tests required by TSO C-69, or
mathematical analysis where necessary, would
need to be accomplished to establish the pass/fail
loading force(s) and the duration(s) of loading
force application. These pass/fail criteria should
include additional amounts of force beyond
those shown to exist for any particular girt, e.g.,
150% of demonstrated load, to provide a signi-
ficant margin of safety for those evacuees who
will eventually need to use the slide or slide/raft.


in LU

Force

Force in Lbs

Figure 5
Symmetrical Girt Loading Test Results

10 15 20
Time in Seconds

Figure 6
Asymmetrical Girt Loading Test Results

1750 4—

1500 +—-

“= 3
iy
a
So

a

Time in Seconds

12



Technical Report Documentation Page

7. Report No. 2. Government Accession No. 3. Recipient's Catalog No.
DOT/FAA/AM-98/3

4, Title and Subtitle, ©. Report Date

Inflatable Escape Slide Beam and Girt Strength Tests: Support for February 1998

Revision of Technical Standard Order C-69b

7, Author(s) @. Performing Organization Report No.
McLean, G. A., Palmerton, D. A., Chittum, C. B., George, M. H., and

Funkhouser, G. E.

9. Performing Organization Name and Address 10. Work Unit No. (TRAIS)
Protection and Survival Laboratory

Gil Aeromedical Institute

Oklahoma City, OK 73125 TT. Contract or Grant No.

12. Sponsoring Agency name and Address 13. Type of Report and Period Covered
Office of Aviation Medicine

Federal Aviation Administration

800 Independence Ave.

Washington, D.C. 20591 14. Sponsoring Agency Code

15. Supplemental Notes

This work was performed under task AM-B-96-PRS-93.

16. Abstract

The ability of inflatable escape slides to provide a safe egress route for evacuees in transport aircraft
emergencies depends, to a great degree, on the structural integrity of such slides. Recent certification
demonstration evacuations have demonstrated potential problems with the structural integrity of inflatable
escape slides; specifically, the strength of the major structural elements of escape slides, i.e., the inflatable
beams, has been questioned. With severe loading of the escape slides, the inflatable beams are known to
bend, sometimes allowing the sliding surfaces between the beams to form cups that can impede the egress of
evacuees by making it hard to climb out of the slide and onto firm footing. This study was intended to
develop practical dynamic tests of inflatable beam strength that can be implemented during the
developmental manufacturing process for escape slides to identify and correct inadequate inflatable beam
strength. The result was the development of a practical test that uses sandbags to simulate human evacuees
who are bunched together, toboggan style, during movement down the slide. The test provides data essentially
equivalent to that obtained with human test subjects and also provides substantial benefits to human test
subject safety.

Additional tests of the structural integrity of the escape slide girt (attachment-to-the-aircraft) were also
developed to standardize the test procedures for girt strength. Prior manufacturing tests had utilized 2
challenges: static loading of the girt attachment by sandbags laid along the erected slide surface and lateral
loading of the girt by a 25-knot wind applied horizontally to the side of the erected escape slide. The new
tests use both symmetrical and asymmetrical loading of the girt in a tensile test machine. These tests provide
an enhanced ability to assess girt strength, especially as related to ease of execution and replicability of
results.

17. Key Words 78. Distribution Statement

Inflatable, escape slide, egress, evacuation, girt, testing | Document is available to the public through the
National Technical Information Service,

Springfield, Virginia, 22161
19. Security Classif. (of this 20, Security Classif. (of this page) 21. No. of Pages 22. Price
report)
Unclassified Unclassified 17

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized


NOTICE

This document is disseminated under the sponsorship of
the U.S. Department of Transportation in the interest of
information exchange. The United States Government
assumes no liability for the contents or use thereof.


Table 3
Single Lane Slide Sandbag Drop Tests

Aircraft Sill Slide | Sliding Test Results
Type | Height | Length} Angle Condition
DC-8 10.5 15.4 43 One 250 Ib. bag Bag caused severe bending
feet feet. |degrees} dropped from sill before springing back into
height onto the middle] shape, bouncing the bag off
of the slide. the end.
B-737 8.5 15.5 33 One 250 Ib. bag Bag slid about 7 feet, bending
feet feet |degrees| dropped from 3 ft. the slide severely but
above sill height at 5 | springing back and bouncing
ft. down the slide. the bag off the end.
MD-80 8.5 12.5 44 One 250 Ib. bag Bag caused less severe
feet feet |degrees| dropped from 3 ft. bending than was seen with
above sill height at 4 |the first two slides and the bag
ft. down the slide. slid off the end of the slide.
Prototype} 8.5 16.75 31 One 250 Ib. bag Bag caused intermediate
B-737 feet feet |degrees| dropped from 3 ft. bending compared to the
above sill height at 6 | others, this caused the bag
ft. down the slide. to bounce off the end.

would furnish escape slides. Application of the
proposed test methods to the problem quickly
led to the realization that an alternative method
could better provide the answers required, even
though the original questions were also some-
what modified by the alternative approach.

For example, in the original toboggan test
designed to employ human subjects, early at-
tempts at implementation soon made it clear
that the steep sliding angles produced by the
human toboggans would imperil those persons
comprising both the toboggan and those sliding
immediately after. Human injury occurring dur-
ing the test appeared so likely that the (potential)
added safety benefit of assuring that the escape

slide could be cleared by evacuees during times
of large static and dynamic loading was offset, if
not overwhelmed, by potential injury to test
participants. Thus, a change in test methodology
was deemed appropriate, even though the ability
to witness humans dismounting the slide during
the test was forfeited.

The choice of the alternative sandbag to-
boggan test methodology, albeit without the
continuing dynamic component that additional
evacuees would provide, appeared to provide the
absolute test of beam strength required, and the
question of multiple dynamic loading is already
being answered by the 70-person-per-minute
flow-rate test incorporated in another section of


Figure 3
Symmetrical Girt Loading Test Method

Figure 4
Asymmetrical Girt Loading Test Method

Load Cell L

i