c. Photographic Instrumentation. Photographic instrumentation is used for documenting the response of the ATDs and the test items to the dynamic test environment. Both high-speed and still image systems should be used.
(1) Photographic instrumentation is in accordance with SAE J211, Part 2. Highspeed cameras that provide data used to calculate displacement or velocity should operate at a minimum nominal speed of 500 frames per second. Photo instrumentation methods should not be used for measurement of acceleration. The locations of the camera and targets or targeted measuring points within the field of view should be measured and documented. Targets should be at least 1/100 of the field width covered by the camera and should be of contrasting colors or should contrast with their background. The center of the target should be easily discernible. A description of photographic calibration boards or scales within the camera field of view; the camera lens focal length; and the make, model and serial number of each camera and lens should be documented for each test. Appropriate digital or serial timing should be provided on the image media. A description of the timing signal, the offset of the timing signal to the image, and the means of correlating the time of the image with the time of the electronic data should be provided.
(2) Rectilinearity of the image is documented in accordance with SAE J211, Part 2. If the image is not rectilinear, as indicated by an overall error in excess of 1 percent, appropriate correction factors should be used in the data analysis process. A rigorous, verified analytical procedure should be used for data analysis. The accuracy of the procedure is considered adequate, if the difference between the measured and derived distance separating the Validation Target Pair, as defined in SAE J211, Part 2, is not greater than 1.0 cm (0.4 inches).
(3) Cameras operating at a nominal rate of 200 frames per second or greater may be used to document the response of ATDs and test items, if measurements are not required. For example, actions such as movement of the pelvic restraint system webbing off of the ATD's pelvis can be observed by documentation cameras placed to obtain a “best view” of the anticipated event. These cameras should be provided with appropriate timing and a means of correlating the image with the time of electronic data.
(4) Still image cameras should be used to document the pre-test installation and the post-test response of the ATDs and the test items. At least f our pictures should be obtained from different positions around the test items in pre-test and post-test conditions. Where an upper torso restraint system is installed, post-test pictures must be obtained before moving the ATD. For additional post-test pictures, the ATD's upper torso may be rotated to its approximate upright seated position, so that the condition of the restraint systems may be better documented, but no other change to the post-test response of the test item or the ATD should be made. The pictures should document whether the seat remained attached at all points of attachment to the test fixture.
(5) Still pictures may also be used to document post-test yielding of the seat for the purpose of showing that it would not impede the rapid evacuation of the aircraft occupants. The ATD should be removed from the seat in preparation for still pictures used for that purpose. Targets or an appropr iate target grid should be included in such pictures, and the views should be selected so that potential interference with the evacuation process can be determined. For tests where the ATD's head impacts a fixture or another seat back, pictures shall be taken to document the head contact areas.
9. TEST FIXTURES.
a. General. A test fixture is required to positi on the test article on the sled or drop carriage of the test facility and takes the place of the airplane's floor structure. It does not need to simulate the airplane floor flexibility. It holds the attachment fittings or floor tracks for the seat and provides the floor deformation if needed for the test; it provides anchorage points if necessary for the restraint system; it provides a floor or footrest for the ATD; and it positions instrument panels, bulkheads, or a second row of seats, if required.
b. Floor Deformation.
(1) Purpose of floor deformation. The purpose of providing floor deformation for the longitudinal tests is to demonstrate that the seat system will remain attached and perform properly, even though the seat or airframe may be deformed by the forces associated with the crash. Floor deformation is not required for demonstrating compliance with injury criteria.
(2) Floor deformation fixture. For the typical seat with four seat legs mounted in the aircraft on two parallel tracks, the floor deformation test fixture should consist of two parallel beams: a pitch beam that pivots about a lateral (y) axis and a roll beam that pivots about a longitudinal (x) axis (see Figure 9-1 for a schematic representation). The beams can be made of any rigid structural form: box, I-beam, channel, or other appropriate cross section. The pitch beam s hould be capable of rotating in the x-z plane up to ±10 degrees relative to the longitudinal (x) axis. The roll beam should be capable of ±10 degrees roll about the centerline of floor tracks or fittings. A means should be provided to fasten the beams in the deformed positions.
The beams should have provision for installing a floor track or other attachment fittings on their upper surface in a manner that does not alter the above-floor strength of the track or fitting. The track or other attachment f ittings must be representative in above-floor configuration and in the strength used in the airplane. Structural elements below the surface of the floor that are not considered part of the floor track or seat attach fitting need not be included in the installation. Appropriate safety precautions should be taken while imposing floor deformations.
Figure 9-1. Schematic Floor Deformation Fixture— Seat Legs Attached at Floor Level
(3) Airplane floor track or attachment fitting simulation. An example of the minimum required representation of a floor track is shown in Detail A of Figure 9-1 for one type of seat track. The track or other a ttachment fittings must be representative of those used in the airplane. Alternatively, three components of reaction forces and three components of reaction moments may be measured during dynamic tests. These six components may be applied simultaneously, by a separate static or dynamic test to a track or attachment fitting used on an airplane, or to a more critical track or attachment fitting than that used on an airplane to demonstrate that the loads measured in the dynamic impact test will not fail the track or attachment fitting used on an airplane.
(4) Load transducer installation (optional). The pitch and roll beams should have provisions for installing individual load transducers at each seat leg attachment point capable of measuring three reaction forces and, if necessary, three reaction moments (see paragraph 7b(3)). The load transducers should have provisions to install floor track or other attachment fittings on their upper surface in a manner that does not alter the above-floor strength of the track or fitting.
c. Other Mounting Configuration Constraints. The preceding discussion describes the fixture and floor deformation procedure that would be used for a typical seat that uses four seat legs and four attachments to the aircraft floor. These test procedures are not intended to be restricted only to those seat configurations, but can be adapted to seats having other designs. Special test fixtures may be necessary for those different configurations. The following methods, wh ile not covering all possible seat designs, should be followed for the more common alternatives:
(1) Airplane seats with three legs may have one central leg at the front or back of the seat and one leg on each side of the seat. The central leg is held in its undeformed position as deformation is applied to the side legs.
(2) Seats that have more than two pairs of legs should be tested with the floor warpage condition that results in the most critically stressed condition. This typically involves warping adjacent pairs of legs. S eats that employ several pairs of legs, ganged together by common cross tubes, can be distorted so that the critical pair of legs is rolled, while the remaining legs on one side of the critical leg are pitched in unison. The legs that are pitched should be selected to increase the load on the critical leg and stress the floor or track fitting in the most severe manner (see Figures 9-2 and 9-3).
POSITION AFTER
FLODR DEFORMATION › POSITION BEFORE
FLOOR DEFORMATION
FIXED LEGS 10 DEGREE ROLL
LEFT DE RIGHT
HIGHEST LOADED ROLL AXIS LEG
PITCH AXIS 10 DEGREE PITCH DOWN Figure 9-2. Floor Warpage Multiple Leg Seat 32
POSITION BEFORE
FLOOR DEFORMATION
POSITION AFTER
FLOOR DEFORMATION PITCH AXIS
PITCH BEAMS
ROLL AXIS 10 DEGREE PITCH DOWN (TYP. )
ROLL BEAM
HIGHEST LOADED LEG 10 DEGREE ROLL
LEFT OR RIGHT Figure 9-3. Floor Warpage Multiple Leg Seat 33
(3) Seats that are wall-mounted must be evaluated individually. There are several types of mounting schemes, some of which are discussed below. As noted in the preamble to Amendment 25-64, the dynamic impact pulses defined in § 25.562 are considered compatible with existing airframe structure. The definition of the test fixture required for floor-mounted seats takes this into account, so that extensive floor structure is not necessary for test; that is, only the seat track above the floor is used. The important consideration is the retention of the seat under dynamic conditions, and the test setup should account for this in wall-mounted seats as well. The following guidance has been established with this objective in mind.
(a) Seats that are mounted to primary airplane structure, such as a pressure bulkhead, need only be tested with the attachment fitting mounted to rigid structure in a manner equivalent to the production installation.
(b) Seats mounted to a structure, such as a structural bulkhead, galley or lavatory, where no integral structural members are used for attachment should be tested with the seat attached to segments of the mounting surface. These segments are typically eight inch by eight inch sections of the panel. These sections can, in turn, be mounted to a rigid structure.
(c) Seats that are mounted to single panel furnishings, such as class dividers or windscreens, where the panel essentially fulfills the role of the legs should be treated the same as floor mounted seats. For the purpose of conducting tests, the entire assembly, including the panel and its attachments, should be included in the test setup. In this case, floor warpage should be applied to track-mounted furnishings.
(4) Seats that are attached to both the floor and a bulkhead should be tested on a fixture that positions the bulkhead surface in a plane through the axis of rotation of the pitch beam. The bulkhead surface should be located perpendicular to the plane of the floor (the airplane floor surface, if one were present) in the undeformed condition or in a manner appropriate to the intended installation. Either a ri gid bulkhead simulation or an actual bulkhead panel can be used. If a test fixture with a rigid bulkhead simulation is used, the seat restraint system is attached to fittings installed in a test panel equivalent to those used in the actual installation. The seat is attached to the bulkhead and the floor in a manner representative of the airplane installation, and the floor shall then be deformed as described in paragraph 9b.
(5) Seats that incorporate attachment to the aircraft sidewall must be evaluated taking into consideration the expected aircraft fuselage cross-section deformation during a crash. The seat could be mounted between sidewalls or to the side wall and the floor.
The test fixture will allow either a pitch beam or a roll beam to be installed at the outboard attachment structure of the seat. The seat positioning pins or locks are fastened in the same manner as used in the aircraft, including the adjustment of anti-rattle mechanisms, if provided. The following two seat attachment cases incorporating sidewall attachment will be considered:
(a) For the case where there are both sidewall and inboard floor attachments, two tests may be required.
1 To substantiate the seat and sidewall attachment structure, the roll beam is installed on the sidewall attachment and the pitch beam is installed on the inboard floor location as shown in Figure 9-4. The test is conducted with the roll beam rotated simulating the sidewall rotating outboard. The pitch beam rotation and the yaw angle direction of the seat are selected to produce the critical loading condition for the sidewall attachment structure.
2 To substantiate the seat and inboard floor attachment structure, the roll beam is installed on the inboard floor attachment and the pitch beam supports the sidewall attachment. The pitch and roll directions of the test fixture and the yaw direction of the seat are selected fixture and the yaw direction of the seat are selected to produce the critical loading condition for the inboard attachment structure.
Both tests are required, unless it is shown by rational analysis that testing one attachment structure in its critical condition substantiates the other attachment structure.
(b) For the case where the seat is mounted between aircraft sidewalls with no floor attachment structure, the roll beam is installed at the critical outboard attachment structure, while the pitch beam is located at the other outboard attachment structure. The test is conducted with the roll beam rotated simulating the sidewall rotating outboard. The pitch beam rotation and the yaw angle of the seat are selected to produce the critical loading condition for the outboard attachment structure.
Figure 9-4 Schematic Floor Deformation Fixture— Seat Legs Attached at Side Wall
(6) Seats that are mounted between interior furnishings. Seats that are mounted between two interior furnishings, such as an observer seat or a flight attendant seat mounted between interior walls, should be tested with deformation in plane as shown in Figure 9-5. Deformation is applied so that the critical attachment is first raised, resulting in vertical displacement of 5 degrees from one side of the seat to the other, and is then rolled outboard 5 degrees.
Example: Observer's SeExample: Observer's Seat at
AC 25.562-1B 01/10/2006 5 Degrees due to Vertical Displacement 5 Degrees Roll 10 Degrees Total on Attachment Fitting Vertical Displacement Figure 9-5 Seats Mounted in an Aisle
(7) Seats that are cantilevered from one sidewall without connection to other structure are not subject to floor deformation. A determination must be made whether sidewall deformations could be expected that could generate a condition critical for seat performance in a crash. If sidewall deforma tion is likely, the entire sidewall attachment plane or the attachment points is deformed in a manner to represent the sidewall deformation. Either a rigid sidewall simulati on or an actual sidewall panel may be used.
If a test fixture with a rigid sidewall simulation is used, the seat/restraint system is attached to fittings installed in a test panel equivalent to those used in the actual installation.
(8) Seats that are mounted on adapter plates (plinth). Where the adapter (plinth) is used to mount a single seat assembly (whether single or multiple place), and the adapter plate is attached to the floor, the adapter plate is considered as part of the seat assembly and should be deformed as described in paragraph 9b. Any items of mass attached to the plinth need to be represented and included in the dynamic testing, as discussed in Appendix 5 of this AC.
(9) Seats that are mounted on a pallet (for example, multiple seat rows). A pallet is considered part of the floor structure of the airplane based on its size, structural design, and redundancy of attachment. The seats should be attached to the test fixture in 37
a manner representative of the airplane installation. The seat legs are deformed as described in paragraph 9b. Any items of mass attached to the pallet and not part of the seat structure do not need to be included in the dynamic testing.
d. Side-facing Seats.
(1) General. All seats occupiable for takeoff and landing are subject to the specified dynamic test conditions. Included are side-facing seats and both single occupancy and multiple place seats, such as divans. Compliance with the structural requirements should be demonstrated for side-facing seats, using the same conditions for the test and pass/fail criteria as for fore- and aft-facing seats. The seat should be loaded in the most critical case structurally. Mean s of restraining the ATDs may need to be adapted to ensure adequate retention during the test. The application of floor distortion will need to be assessed on an individual basis, depending on the design of the fixation of the seat. The injury criteria of § 25.562 are not adequate to demonstrate equivalent safety of side-facing seats when compared to fore- and aft-facing seats. To demonstrate equivalent safety fully in the absence of such specified criteria, the applicant must use other injury criteria which may be derived from the automotive industry, which uses side-impact ATDs.
(2) Assessment criteria. Research into side-f acing seats is ongoing. As research proceeds, the FAA will work toward establishing a more definitive policy with respect to the acceptance of side-facing seats. Until then, in the absence of specific compliance guidance, the FAA is prepared to assess side-facing seats on the following basis:
(a) The seat must demonstrate compliance with the structural requirement.
(b) If an acceptable side impact ATD has not been used with assessment of the corresponding injury criteria, it must be shown that the occupants are restrained in a manner that prevents substantial energy absorption by body to body contact (on a multiple occupancy seat) and which, using the best available engineering judgment, minimizes injury to the occupant(s).
e. Multiple Row Test Fixtures. In tests of passenger seats that are normally installed in repetitive rows in the airplane, head and knee impact conditions are best evaluated through tests that use at least two rows of seats. These conditions are usually critical only in Test 2. This test allows direct measurements of the head and femur injury data.
(1) The fixture must be capable of setting the airplane longitudinal axis at a yaw angle of -10 to +10 degrees. The fixture should also allow adjustment of the seat pitch and installation angle with respect to the airplane center line.
(2) To allow direct measurement of head acceleration for the head injury assessment of a seat installation where the head of the occupant is within striking distance 38
of structure, a representative impact surface may be attached to the test fixture in front of the seat at the orientation and distance from the seat representing the airplane installation.
f. Other Fixture Applications. Test fixtures should provide a flat footrest for ATDs used in tests of passenger seats and crewmember seats that are not provided with special footrests or foot-operated airplane controls. The surface of the footrest must be at a position representative of the floor in the airplane installation. Test fixtures used for evaluating crew seats that are normally associated with special footrests or foot-operated controls must simulate those components. (A footrest is optional for Test 2 structural tests—see paragraph 10f.) Test fixtures may also require guides or anchors for restraint systems or for holding instrument panels or bulkheads. If these provisions are required, the installation must represent the configuration of the airplane installation and be of adequate structural strength. The strength of any such restraint anchorages should be equivalent to the actual installation, whereas instrument panels or bulkheads should be sufficiently strong to ensure that they withstand the test pulse.
10. TEST PREPARATION.
a. Preparation for the Tests will involve positioning and securing the ATD, the ATD restraint system, the seat, and the instrumentation. This is done for the specific critical condition being tested. Preparations that pertain to the normal operation of the test facility, such as safety provisions and the actual procedures for accomplishment of the tests, are specific to the test facility and are not addressed in this AC.
b. Use of Anthropomorphic Dummies. Anthropomorphic dummies used in the tests discussed in this AC should be maintained to perform in accordance with the requirements described in their specification. Periodic teardown and inspection of the ATD should be accomplished to identify and correct any worn or damaged components, and appropriate ATD calibration tests (as described in their specification) should be accomplished if major components are replaced. For the tests discussed in this AC, the following procedures have been found to be adequate:
(1) Since extremes of temperature and humidity can affect ATD performance, the ATDs should be maintained at a temperature range between 66 to 78 degrees F (19 to 26 degrees C) and at a relative humidity from 10 to 70 percent for a minimum of 4 hours prior to the test.
(2) Each ATD should be clothed in form-fitting cotton stretch garments with short sleeves, mid-calf length pants, and shoes (size 11E) weighing about 2.5 pounds.
The color of the clothing should be in contrast to the color of the restraint system.
(3) For tests where the ATD's head is expected to impact a fixture or another seat back, the head and face of the ATD may be treated with a suitable material to mark head contact areas. The material used must not reduce the resulting HIC values.