US. Department of Transportation Federal Aviation Administration Advisory Circular Subject:: DYNAMIC EVALUATION OF SEAT Date: 01/19/96 RESTRAINT SYSTEMS & OCCUPANT Initiated by: ANM_110
PROTECTION ON TRANSPORT
AIRPLANES AC No: 25.562-1A Change:
1. PURPOSE. This advisory circular (AC) provides information and guidance regarding acceptable, but not the only, means of compliance with Part 25 of the Federal Aviation Regulations (FAR) applicable to dynamic testing of seats intended for use in transport category airplanes. The AC provides background and discussion of the reasoning behind the test procedures. It also describes the test facilities and equipment necessary to conduct the tests. Terms used in this AC, such as "shall" and "must" are used only in the sense of ensuring applicability of this particular method of compliance when the acceptable method of compliance described herein is used. While these guidelines are not mandatory, they are derived from extensive FAA and industry experience in determining compliance with the pertinent FAR. This advisory circular does not change, create any additional, authorize changes in, or permit deviations from, regulatory requirements.
2. CANCELLATION. Advisory Circular 25.562-1, dated 3/6/90, is cancelled.
3. RELATED REGULATIONS. Sections 25.562, 25.785, 25.787, and 25.789 of Part 25 of the Federal Aviation Regulations.
4. DISCUSSION.
a. Intent of Tests. The intent of the tests is to evaluate airplane seats, restraints, and related interior systems in order to demonstrate the structural strength and the ability of those systems to protect an occupant from injuries in a crash environment. For example, occupant injury potential, which is influenced by head strike envelopes and seat pitch, should be assessed. This assessment will be essentially qualitative.
b. Standardized Test Procedures--Reason and Practicalities. The tests described are standardized procedures that are generally to be regarded as the minimum necessary to demonstrate compliance. Such standardized procedures ensure that, to the maximum extent possible, consistent results are achieved between different test facilities. These facilities may be of varying types, as described in paragraph 7. They will often not be under the direct control of the designer or manufacturer of the article under test, and they may be primarily dedicated to testing not related to the aerospace industry. For this reason many of the procedures and evaluations described are already accepted as standards by government and commercial test facilities and have been modified only as necessary for the specific testing of civil airplane systems.
c. Standardized Test Procedures--Relationship to Design Standards . As stated above, the tests are, of necessity, standardized. The most obvious examples are the one size and weight representation of the occupant and the two discrete directions specified for the test impact. This philosophy is no different than that applied to static testing but, in the dynamic case, results in a much more complex consideration of the design factors involved in ensuring that the testing performed is adequate to demonstrate compliance with the applicable regulations.
(1) Occupant size. The dynamic tests are performed with an anthropomorphic test device (ATD) approximately representing the 50th percentile male occupant. Although the basic structural capability of the seat/restraint system is not directly demonstrated for other size occupants, aspects such as energy absorbing systems, restraint system loads and anchorage locations, and seat adjustments are typical design factors which are directly influenced by occupant size.
(2) Test Conditions. Only the two minimum impact tests are described in the dynamic test procedures discussed in this AC. These procedures therefore address the tests required to demonstrate compliance for one seat and restraint system installation. A typical use of a seat model on a particular aircraft will involve variations of seat design and installation. Additional tests may be necessary to demonstrate compliance for these variations if analysis is not adequate. An example is the lateral component of the test where it is necessary to consider the effect of loads from either side.
(3) Floor Deformation. The test procedure requires that for structural evaluation the floor should be deformed. The seat and restraint system should also perform properly if the floor remains undeformed.
(4) Head Impact. Occupant head impact with the interior of the airplane, should it occur, is evaluated by using a Head Injury Criterion (HIC) that can be measured directly in the tests described in this AC, or in alternative tests of the interior. The HIC is measured on the most critical surface within the ±10 degrees yaw envelope (measurement of the HIC does not supersede the requirements of § 25.785). The HIC does not consider injuries that can occur at low impact velocities from contact with surfaces having small contact areas or sharp edges, especially if those surfaces are relatively rigid.
(5) Femur Injury. Extensive seat testing has shown that the femur loading criterion is not exceeded. For this reason, the femur loads need not be recorded in the individual test if compliance can be shown by rational comparative analysis using data from previous tests.
NOTE: There may be several other aspects of the standardized test procedure that need to be considered when determining the test program required to demonstrate compliance or interpret the test results. The extent of the test program will depend on the most critical case determination and its applicability to other configurations. Further information on this aspect of testing is provided in paragraph 5b.
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5. TEST CONDITIONS .
a. General. A minimum of two dynamic tests are required to assess the performance of an airplane seat, restraints, and related interior system. The seat, the restraint, and the nearby interior are all considered to act together as a system to provide protection to the occupant during a crash. For side-facing seats, there may be additional criteria necessary to determine that these seats provide the same level of safety as is intended by the regulation. (See paragraph l0d for additional considerations regarding side -facing seats.)
(1) Test 1 (Figure 1), as a single row seat test, determines the performance of the system in a test condition where the predominant impact force component is along the spinal column of the occupant, in combination with a forward impact force component. This test evaluates the structural adequacy of the seat, critical pelvic/lumbar column forces, and permanent deformation of the structure vender downward and forward combined impact loading, and may yield data on ATD head displacement, velocity, and acceleration time histories.
(2) Test 2 (Figure 1), as a single row seat test, determines the performance of a system in a test condition where the predominant impact force component is along the longitudinal axis of the airplane and is combined with a lateral impact force component. This test evaluates the structural adequacy of the seat, permanent deformation of the structure, and the pelvic restraint and upper torso restraint (if applicable) behavior and loads, and may yield data on ATD head displacement, velocity, and acceleration time histories, and the seat leg loads imposed on the seat tracks or attachment fittings.
This test requires simulating airplane floor deformation by deforming the test fixture, as respectively prescribed in Figures 1 and 2 for single occupant and multiple occupant seats, prior to applying the dynamic impact conditions.
The purpose of providing floor deformation for the test is to demonstrate that the seat/restraint system will remain attached to the airframe and perform properly, even though the airplane and/or seat are deformed by the forces associated with a crash.
(3) For seats placed in repetitive rows , an additional test condition, using two seats in tandem placed at representative fore and aft distance between the seats (seat pitch), similar to Test 2 with or without the floor deformation directly evaluates head and femur injury criteria (the floor deformation is required if the test also demonstrates structural performance). These injury criteria are dependent on seat pitch, seat occupancy, and the effect of hard structures within the path of head excursions in the ±10 degrees yaw attitude range of the Test 2 conditions. The test procedure using the appropriate data obtained from Test 2, as described in paragraph 13d, may be an alternative to multiple row testing.
NOTE: It may be possible to evaluate the HIC using alternative tests. Specific methodologies will require acceptance for certification.
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TEST I TEST 2 Illustration shows a forward-facing seat Inertial load / yaw right or left shown by arrow 10° 30° Min V; m/s (ft/s) 10.67 (35) 13.41 (44) Max t, s 0.08 0.09 Min G. 14 16 Deform floor:
Degrees roll 10 Degrees pitch 10 Test Pulse Simulating Aircraft Floor Time -→ Deceleration-Time History:
Deceleration t, = Rise time V; = Impact velocity Figure 1. Type A Seat/Restraint System Dynamic Tests 4 Par 5
b. Consideration of test criteria. The tests should be planned to achieve "most critical" conditions for the criteria that make up each test.
(1) For multiple place seats, a rational structural analysis shall be used to determine the number and seat location for the ATDs and the direction for seat yaw in Test 2 to provide the most critical seat structural test. This will usually result in unequally loaded seat legs. The floor deformation procedure shall be selected to increase the load on the highest loaded seat leg and to load the floor track or fitting in the most severe manner; however, a special procedure has been provided, as discussed in paragraph l0c(2), to account for seats that have more than two pairs of legs.
(2) If multiple-row testing is used to gather data to assess head and femur injury protection in passenger seats, the seat pitch shall be selected so that the head would be most likely to contact hard structure in the forward seat row. The effect of the 10 degree yaw in Test 2, the seat back breakover, and front seat occupancy shall be considered. Results from previous tests or rational analysis may be used to estimate the head strike path of similar seats in similar installations. The front row may be unoccupied.
(3) If non-symmetrical upper torso restraints (such as single diagonal shoulder belts) are used in a system, they shall be installed on the test fixture in a position representative of that in the airplane and which would most likely allow the ATD to move out of the restraint. For example, in a forward-facing crew seat equipped with a single diagonal shoulder belt, the seat should be yawed in Test 2 in a. direction such that the belt passes over the trailing shoulder.
(4) If a seat has vertical or horizontal adjustments, it shall be tested in the position that produces the most critical loads on the seat structure (typically the highest vertical position). Positions prohibited for takeoff and landing need not be considered. Seat adjustments that do not have a significant effect on structural loading (e.g., thigh support angle, lumbar support, armrest and headrest positions) shall be tested in the design positions for the SOthpercentile male occupant, unless special requirements dictate the positions allowed for takeoff and landing. In addition, height adjustment should be relative to the interior envelope as it relates to the upper contour (ceiling) of the airplane whenever a specific seat design is approved in a particular airplane. Therefore, the seat needs only to be raised to the point where the head of the 50th percentile ATD contacts the upper portion of the airplane interior. Height adjustment to a level above the normal 50th percentile male location is intended to validate the strength of the seat and is not related to testing for a range of occupant sizes.
6. TEST ARTICLES.
a. General. In all cases, the test article must be representative of the final production article in all structural elements, and shall include the seat cushions, restraints, and armrests. It must also include a functioning position adjustment mechanism and correctly adjusted breakover (if present). Food trays or any other service or accouterment that are part of the seat design must be representative of the final production item if they influence seat stiffness or head impact.
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Otherwise they and any other items of mass that are carried on or positioned by the seat structure e.g., weights simulating luggage carried by luggage restraint bars [90 N (20 lb) per passenger place], fire extinguishers, survival equipment, emergency equipment etc. need only be representative masses. If these items of mass are placed in a position that could limit the function of an energy-absorbing feature in the test article, they should be of representative shape and stiffness, as well as weight. In addition, items of mass of any significance could become both an evacuation hazard, as well as dangerous projectiles.
Nonetheless, detachment of certain items, such as an in-arm ashtray or decorative trim, can be considered inconsequential and should not be grounds for re-test (the means of r estraint should be improved, however). In any case, the separation of an item of mass should not leave any sharp or injurious edges.
Function of equipment or systems after the test is not required. Once an item of mass has been demonstrated to be retained in its critical loading case, subsequent tests may be conducted with the item secured for test purposes. This AC does not establish operational requirements for equipment attached to the seat system.
b. Selection of test articles. Many designs comprise a family of seats that have the same basic structural design but differ in detail. For example, a basic seat frame configuration can allow for several different seat leg locations to permit installation in different airplanes. If these differences are of a nature that their effect can be determined by rational analysis, then the analysis can determine the most critical configuration. As a minimum, the most highly stressed configuration shall be selected for the dynamic tests so that the other configurations could be accepted by comparison with that configuration.
For Test 2, there are two factors that need to be considered in selecting the critical structural test configurations. First, the seat to airplane interface loads (undeformed seat) can be determined by rational analysis for all seat design and load configurations. The rational analysis can be based on static or dynamic seat/occupant analytical methods. That rational analysis can form the basis for selecting the most highly stressed critical configuration based on load. Additionally, the effects of seat deformation should also be considered. As noted, a family of seats typically includes seat models with varied seat leg locations. The effects of floor deformation are more critical for narrow spaced seat legs. Thus, a test or rational analysis of the seat model with the minimum seat leg spacing needs to be conducted to evaluate the most highly stressed critical configuration based on deformation.
The following additional items shall be considered in choosing test articles and the manner of loading:
(1) If a multiple -place seat incorporates energy-absorbing or load -limiting features that are necessary to meet the test criteria or other requirements, a partially occupied seat may adversely affect the performance of that seat. In such a case it shall be shown, by rational analysis or additional testing, that the seat will continue to perform as intended, even with fewer occupants.
(2) If different configurations of the same basic design incorporate loadcarrying members, especially joints or fasteners, that differ in detail design, the performance of each detail design should be demonstrated in a dynamic test. Experience has shown that small details in the design often cause problems in meeting the test performance criteria.
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(3) Additional dynamic impact testing may be required for a seat with features that could affect its performance, even though the test may not be the most critical case based on structural performance. For example, if in one of the design configurations the restraint system attachment points are located so that the pelvic restraint is more likely to slip above the ATD's pelvis during the impact, that configuration should also be dynamically tested, even though the structural loading might be less than the critical configuration in a family of seats.
(4) Typical dress cover materials, including synthetic and natural fabrics, and leather, can be used on a seat without testing more than one material, or substituted on an already certificated seat.
Evaluation of such materials has shown the effect on test results is small, particularly considering other factors such as occupant clothing. It is possible that some unusual seat surfaces such as hard plastics, which exhibit very low friction coefficients, may require some additional substantiation.
7. TEST FACILITIES.
a. General There are a number of test facilities that can be used to accomplish dynamic testing. These can be grouped into categories based on the method used to generate the impact pulse (i.e., accelerators, decelerators, or impact with rebound), and whether the facility is a horizontal (sled) design or a vertical ( droptower) arrangement. Each of the designs has characteristics that have advantages or disadvantages with regard to the dynamic tests discussed in this AC. One concern is the rapid sequence of acceleration and deceleration that must take place in the tests. In an airplane crash, the acceleration phase is always gradual, and usually well separated in time from the deceleration (crash) phase. In a test, the deceleration always closely follows the acceleration. When assessing the utility of a facility for the specific test procedures outlined in the recommendations, it is necessary to understand the possible consequences of this rapid sequence of acceleration and deceleration.
b. Deceleration sled facilities. In an airplane crash, the impact takes place as a deceleration, so loads are applied more naturally in test facilities that create the test impact pulse as a deceleration. Since it is simpler to design test facilities to extract energy in a controlled manner than to impart energy in a controlled manner, several different deceleration sled facilities can be found. The deceleration sled facility at the Federal Aviation Administration's Civil Aeromedical Institute (CAMI) was used in developing the test procedures discussed in this AC. The acceleration phase of the .test, where sufficient velocity for the test impact pulse is acquired, can distort the test results if the acceleration is so high that the test articles or ATDs are moved from their intended pre-test position. This inability to control the initial conditions of the test would directly affect the test results. This can be avoided by using a lower acceleration for a relatively long duration and by providing a coast phase (in which the acceleration or deceleration is almost zero) prior to the impact. This allows any dynamic oscillation in the test articles or the ATD, which might be caused by the acceleration, to decay. To guard against errors in data caused by pre-impact accelerations, data from the electronic test measurements (accelerations, loads) should be reviewed for the time period just before the test impact pulse to make sure all measurements are at the baseline (zero) level.
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reviewed to make certain that the ATDs used in the test and the test articles were all in their proper position prior to the test impact pulse.
The horizontal test facility readily accommodates forward-facing spats in both tests discussed in this AC, but problems can exist in positioning the test ATDs in Test 1 if the seat is a rearward facing or side- facing seat. In these cases, the ATDs tend to fall out of the seat due to the force of gravity and must be restrained in place using break-away tape, cords, or strings. Since each installation will present its own problems, there is no simple, generally applicable, guidance which can be given for doing this. Attention should be given to positioning the ATD against the seat back, and to proper positioning of the ATD's arms and legs.
It will probably be necessary to build special supports for the break -away restraint so that they will not interfere with the function of the seat and restraint system during the test. Film taken of the test should be reviewed to make sure that the break-away restraint did break (or become slack) in a manner that did not influence the motion of the ATD or the test articles during the test.
c. Acceleration sled facilities. Acceleration sled facilities, usually based on the Hydraulically controlled Gas Energized (HYGE) accelerator device, provide the impact test pulse as a controlled acceleration at the beginning of the test. The test item and the ATDs are installed facing in the opposite direction from the velocity vector, (opposite from the direction used on a deceleration facility) to account for the change in direction of the impact. There should be no problem with the ATD or the test items being out of position due to pre-impact sled acceleration, since there is no sled movement prior to the impact test pulse. After the impact test pulse, when the sled is moving at the maximum test velocity, it must be safely brought to a stop. Most of the facilities of this design have limited track length available for deceleration, so that the deceleration levels can be relatively high and deceleration may begin immediately after the impact test pulse. Since the dynamic response of the system follows (in time) the impact test pulse, any sled deceleration that takes place during that response will affect the response and change the test results.
The magnitude of change depends on the system being tested, so that no general "correction factor" can be specified. The affect can be minimized if the sled is allowed to coast, without significant deceleration, until the response is complete. If the seat or restraint system experiences a structural failure during the test pulse, the post-impact deceleration can increase the damage and perhaps result in failures of unrelated components. This will complicate the determination of the initial failure mode, and make product improvement more difficult. One other consideration is that the photometric film coverage of the response to impact test pulse must be accomplished when the sled is moving at near maximum velocity. On-board cameras or a series of track -side cameras are usually used to provide film coverage of the test. Since on-board cameras frequently use a wide angle lens placed close to the test items, it is necessary to account for the effects of distortion and parallax when analyzing the film. The acceleration sled facility faces the same problems in accommodating rearward facing or side-facing seats in Test 1 as the deceleration sled facility, and the corrective action is the same for both facilities.
d. Impact-with-rebound sled facilities. One other type of horizontal test facility used is the "impact-with-rebound" sled facility. On this facility, the impact takes place as the moving sled contacts a braking system, which stores the energy of the impact, and then returns the stored energy back to the sled, causing it to rebound in the opposite direction. This facility has the advantage over acceleration or deceleration facilities in that only one half of the required velocity Par
for the impact would need to be generated by the facility (assuming 100 percent efficiency). Thus, the track length can be shortened and the method of generating velocity is simplified. The disadvantages of this facility combine the problems mentioned above for both acceleration facilities and deceleration facilities. Since one of the reasons for this type of facility is to allow short track length to be used, it may be difficult to obtain sufficiently low acceleration just before or after the impact pulse to resolve data error problems caused by significant pre-impact and post impact accelerations.
e. Drop towers. Vertical test facilities can include both drop towers (decelerators) and vertical accelerators. Vertical accelerators that can produce the long duration/displacement impact pulse depicted in Figure 1 have not been generally available. However, drop towers are one of the easiest facilities to build and operate, and are frequently used. In these facilities, the pull of earth's gravity is used to accelerate the sled to impact velocity so that the need for a complex mechanical accelerating system is eliminated. Unfortunately, these facilities are difficult to use for conducting Test 2, particularly for typical forward-facing seats. In preparing for this test, the seat must be installed at an angle such that the ATD tends to fall from the seat due to gravity. The restraint system being tested cannot hold the ATD against the seat unless tightened excessively, and will not usually locate the head, arms, or legs in their proper position relative to the seat. Design and fabrication of an auxiliary "break-away" ATD positioning restraint system just for this test is a complex task. The auxiliary restraint must not only position the ATD against the seat (including maintaining proper seat cushion deflection) during the pre-release condition of lg, it must also maintain the ATD in that proper position during the free fall to impact velocity when the system is exposed to Og, and then it must release the ATD in a manner that does not interfere with the ATD response to impact. The usual sequence of lg/Og impact, without the possibility of a useful "coast" phase, as done in horizontal facilities, causes shifts in initial conditions for the test impact pulse which can affect the response to the impact. The significance of this will depend on the dynamic characteristics of the system being tested, and these are seldom known with sufficient accuracy to enable the response to be corrected.
In addition, the earth's gravity will oppose the final rebound of the ATDs into the seat back, so that an adequate test of seat back strength and support for the ATD cannot be obtained. The problems in Test 1, or with rear-facing seats in Test 2, are not as difficult because the seat will support the ATD occupant prior to the free fall. However, the Og condition that exists prior to impact will allow the ATD to "float" in the seat restraint system, perhaps changing position and certainly changing the initial impact conditions. Again, use of an auxiliary break-away restraint system to correct these problems is difficult.
8. ANTHROPOMORPHIC TEST DEVICES.
a. General. The tests discussed in this AC were developed using modified forms of the ATDs specified by the United States Code of Federal Regulations, Title 49, Part 572 Anthropomorphic Test Dummies, Subpart B - 50th Percentile Male. These "Part 57213" ATDs have been shown to be reliable test devices that are capable of providing reproducible results in repeated testing. However, since ATD development is a continuing process, provision was made for using "equivalent" ATDs. ATD types should not be mixed when completing the tests discussed in this AC.
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b. Modification to measure pelvic/lumbar load.
(1) To measure the axial compressive load between the pelvis and lumbar column due to vertical impact as well as downward loads caused by upper torso restraints, a load (force) transducer shall be inserted into the ATD pelvis just below the lumbar column. There is now a load cell available for this purpose that does not require major alteration to the ATD. The procedure in general is similar to that described in Figure 2. The modification shown in Figure 2 is retained in this revision of the AC to aid facilities that may already incorporate this procedure, which is still acceptable. Future revisions of this AC will not contain this modification procedure, as it is no longer the standard. The illustration shows a commercially available femur load cell, with end plates removed, that has been adapted to measure the compression load between the pelvis and the lumbar column of the ATD.
(2) A femur load cell was selected because of its availability in most test facilities and its ability to measure the compression forces without errors due to sensitivity to shear forces and bending or twisting moments which are also generated during the test. To maintain the correct seated height of the ATD the load cell must be fixed in a rigid cup which is inserted into a hole bored in the top surface of the ATD pelvis. The interior diameter of the cup provides clearance around the outside diameter of the load cell, so that the loads are transmitted only through the ends of the cell. If necessary, ballast shall be added to the pelvis to maintain the weight of the original (unmodified) assembly.
(3) Alternative approaches to measuring the axial force transmitted to the lumbar spinal column by the pelvis are acceptable if the method:
(i) Accurately measures the axial force but is insensitive to moments and forces other than that being measured;
(ii) Maintains the intended alignment of the spinal column and the pelvis, the correct seated height, and the correct weight distribution of the ATD; and
(iii) Does not alter the other performance characteristics of the ATD.
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Figure 2. Installation of Pelvic--Lumbar Spine Load Cell in Part 572B ATD.
This illustration shows an acceptable adaptation of a femur load cell (d) at the base of the ATD lumbar spine (a). The load cell is in line with the centerline of the lumbar spine, and set below the top surface of the pelvis casting to maintain the seated height of the ATD. A rigid adapter cup (e) is fabricated to hold the load cell and a hole is bored in the ATD pelvis to accept the cup. Clearance must be provided between the walls of the adapter cup and the load cell for the wires leading from the cell. The bottom of the load cell is bolted to the adapter cup. Adapter plates having similar hold patterns in their periphery are fabricated for the lower surface of the lumbar spine (b) and the upper surface of the load cell (c). These plates are fastened to the lumbar spine and load cell with screws through holes matching threaded holes in those components, and are then joined together by bolts through the peripheral holes. The flange on the adapter cup has a bolt hole pattern that matches that on the pelvis. The cup is fastened to the pelvis using screws to the threaded holes in the pelvis. Spacers (f) may be placed under the flange of the cup to obtain the specified ATD seating height. Additional weight should be placed in the cavity below the adapter cup to compensate for any weight lost because of this modification. The instrument cavity plug (g) is cut to provide clearance for the adapter cup and added weight.
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c. Other ATD Modifications.
(1) To prevent failure of the clavicle used in Part 572 Subpart B ATDs due to flailing, a clavicle of the same shape but of higher strength material can be substituted.
(2) Submarining indicators, such as electronic transducers, may be added on the ATD pelvis. These are located on the anterior surface of the ilium of the ATD pelvis without altering its contour, and indicate the position of the pelvic restraint as it applies loads to the pelvis. These indicators can provide a direct record that the pelvic restraint remains on the pelvis during the test, and eliminate the need for careful review of high-speed camera images to make that determination.
d. Equivalent ATDs. The continuing development of ATDs for dynamic testing of seating restraint/crash-injury-protection systems is guided by goals of improved biofidelity (human-like response to the impact environment) and reproducibility of test results. For the purposes of the tests discussed in this AC, these improved ATDs can be considered the equivalent of the Part 572B ATD if.
(1) They are fabricated in accordance with design and production specifications established and published by a regulatory agency that is responsible for crash injury protection systems;
(2) They are capable of providing data for the measurements discussed in this AC or of being readily altered to provide the data;
(3) They have been evaluated by comparison with the Part 572B.ATD and are shown to generate similar response to the impact environment discussed in this AC; and
(4) Any deviations from the Part 572B ATD configuration or performance are representative of the occupant of a civil airplane in the impact environment discussed in this AC.
9. INSTRUMENTATION.
a. General.
(1) Electronic and photographic instrumentation systems shall be used to record data for qualification of seats. Electronic instrumentation shall measure the test environment, and measure and record data required for comparison of performance to pass/fail criteria.
(2) Photographic instrumentation shall be used to document the overall results of tests, confirming that the pelvic restraint remains on the ATD's pelvis, and that the upper torso restraint straps remain on the ATD's shoulder during impact, and documenting that the seat does not deform as a result of the test in a manner that would impede rapid evacuation of the airplane by the occupants and that the seat remains attached at all points of attachment. For passenger seats with lap belt angles of btween 45 and 55 degrees, submarining is typically not a problem.
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