For this reason, a second camera (e.g., an overhead camera) for evaluation of submarining is not necessary.
b. Electronic Instrumentation . Electronic instrumentation should be accomplished in accordance with the Society of Automotive Engineers Recommended Practice SAE J211, "Instrumentation for Impact Tests." In this practice, a data channel is considered to include all of the instrumentation components from the transducer through the final data measurement, including connecting cables and any analytical procedures that could alter the magnitude or frequency content of the data. Each dynamic data channel is assigned a nominal channel class that is equivalent to the high frequency limit for that channel, based on a constant output/input ratio versus frequency response plot which begins at 0.1 Hz (+1/2 to -1/2 dB) and extends to the high frequency limit (+1/2 to -1 dB). Frequency response characteristics beyond this high frequency limit are also specified. When digitizing data, the sample rate should be at least five times the -3 dB cutoff frequency of the pre-sample analog filters. Since most facilities set all presample analog filters for Channel Class 1000, and since the -3 dB cutoff frequency for channel class 1000 is 1650 Hz, the minimum digital sampling rate would be about 8000 samples per second. For the dynamic tests discussed in this AC, the dynamic data channels shall comply with the following channel class characteristics:
(1) Sled or drop tower vehicle acceleration should be measured in accordance with the requirements of Channel Class 60, unless the acceleration is also integrated to obtain velocity or displacement, in which case it shall be measured in accordance with Channel Class 180 requirements.
(2) Belt-restraint system and seat attachment reaction loads (when measured) shall be measured in accordance with the requirements of Channel Class 60. Loads in restraint systems that attach directly to the test fixture can be measured by three-axis load cells fixed to the test fixture at the appropriate location. These commercially available load cells measure the forces in three orthogonal directions simultaneously, so that the direction as well as the magnitude of the force can be determined. If desired, similar load cells can be used to measure forces at other boundaries between the test fixture and the test item, such as the forces transmitted by the legs of the seat into the floor track. It is possible to use independent, single axis load cells arranged to provide similar data, but care should be taken to use load cells that can withstand significant cross axis loading or bending without causing errors in the test data.
(3) ATD head accelerations used for calculating the Head Injury Criterion (HIC) should be measured in accordance with the requirements of Channel Class 1000.
(4) ATD femur forces should be measured in accordance with Channel Class 600.
(S) ATD pelvic/lumbar column force shall be measured in accordance with the requirements of Channel Class 600.
Par 9 13
(6) The full-scale calibration range for each channel shall provide sufficient dynamic range for the data being measured.
(7) Digital conversion of analog data shall provide sample resolution of not less than 1 percent of full-scale input.
c. Photographic Instrumentation . Photographic instrumentation shall be 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) High speed cameras that provide data used to calculate displacement or velocity shall operate at a nominal speed of 500 frames per second. Photo instrumentation methods shall not be used for measurement of acceleration. The locations of the cameras and of targets or targeted measuring points within the field of view shall be measured and documented. Targets shall be at least 1/100 of the field width covered by the camera and shall be of contrasting colors or shall contrast with their background. The center of the target shall be easily discernible. Rectilinearity of the image shall be documented. If the image is not rectilinear, appropriate correction factors shall be used in the data analysis process. Photographic instrumentation should be in accordance with SAE J211, part 2.
(2) A description of photographic calibration boards or scales within the camera field of view, the camera lens focal length, and the make and model of each camera and lens shall be documented for each test. Appropriate digital or serial timing shall be provided on the image media. A description of the timing signal, the offset of timing signal to the image, and the means of correlating the time of the image with the time of electronic data shall be provided. A rigorous, verified analytical procedure shall be used for data analysis.
(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 shall be provided with appropriate timing and a means of correlating the image with the time of electronic data.
(4) Still image cameras shall be used to document the pre-test installation and the post-test response of the ATDs and the test items. At least four pictures shall 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 shall 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 shall be made. The pictures shall 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 14 Par 9
occupants. The ATD should be removed from the seat in preparation for still pictures used for that purpose. Targets or an appropriate 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.
10. TEST FIXTURES.
a. General . A test fixture is required to position 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 shall 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 3 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 shall 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 shall be provided to fasten the beams in the deformed positions.
The beams should have provision for installing 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 fittings must be representative in above-floor configuration and strength to that which would be 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.
Par 9 15
ORIGINAL
POSITION NOTE:
FOR CLARITY
LOAD TRANSDUCERS ARE NOT SHOWN.
POSITION
AFTER FLOOF
DEFORMATION
UNDER REAR AXIS
LEG ATTACHMENT
POSITION -ROLL SEAM -P: BEAM MINIMUM SEAT TRACK
TO BE TESTED 10° ROLL
LEFT OR RIGHT
DETAIL (A)
XAMPLE OF AIRCRAF
RACK BEA Figure 3.
Schematic Floor Deformation Fixture; Seat Legs Attached at Floor Level 16 Par 10
(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 3 for one type of seat track. The track, or other attachment 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 l0b(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 shall be adapted to seats having other designs. Special test fixtures may be necessary for those different configurations. The following methods, while not covering all possible seat designs, shall 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 shall be 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. Seats that employ several pairs of legs, ganged together by common cross tubes, can be distorted so that one pair (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 4 and 5).
Par 10
POSITION AFTER
FLOOR DEFORMATION \ POSITION BEFRE FLOOR DEFORNATION
FIXED LEGS 10 DEGREE ROLL
LEFT OR RIGHT
HIGHEST LOADED ROLL AXIS LEG
PITCH AXIS 10 DEGREE PITCH DOWN Figure 4. Floor Warpage Multiple Leg Seat 18 Par 10
POSITION BEFORE
FLOOR DEFORMATION
POSITION AFTER PITCH AXIS
FLOOR GEFORMATION
PITCH BEAMS
RILL AXIS 10 DEGREE PITCH DOWN (TYP.)
ROLL BEAM
- LEG HIGHEST LOADED
LEFT OR RIGHT Figure 5. Floor Warpage Multiple Leg Seat Par 10 19
(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.
(i) 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.
(ii) 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.
(iii) Seats that are mounted to single panel furnishing-s, 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 rigid 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 shall attach to fittings installed in a test panel equivalent to those used in the actual installation. The seat should be 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 l0b.
(5) Seats that are mounted between sidewalk or to the sidewall and floor of an aircraft shall be tested in a manner that simulates airplane fuselage cross-section deformation during a crash.
Brackets shall be provided to attach the seat to the test fixture at the same level above the fixture floor representing the installation above the airplane floor where the inboard tracks or attachment is located. The roll axis should be approximately at the center of the outboard track.
A sidewall bracket shall be located on the roll beam. Then, as the beams are rotated to produce the most critical loading condition (sidewall rotates outward), the combined angular and transitional deformation will simulate the deformation that could take place in a crash (see Figure 6 for a schematic representation).
The seat positioning pins or locks shall be fastened in the same 20 Par 10
manner as would be used in the airplane, including the adjustment of anti-rattle mechanisms, if provided.
ORIGINAL
POSITION
POSITION
AFTER FLOOR
DEFORMATION
REPRESENTATION
SEAT TO \ SIDEWALL
ATTACHMENT -RIGID TEST
SIDEWALL STRUCTURE TRACK 10° ROLL
PITCH AXIS
UNDER REAR OUTBOARD
LEG ATTACHMENT
ORIGINAL POSITION -PITCH
PORT DOWN BEAM Figure 6. Schematic Test Fixture; Sidewall Mounted Seat Par 10 21
(6) Seats that are cantilevered from one sidewall without connection to other structure are not subject to floor deformation. A determination shall be made whether sidewall deformations could be expected that could generate a condition critical for seat performance in a crash. If sidewall deformation is likely, the entire sidewall attachment plane, or the attachment points, shall be deformed in a manner to represent the sidewall deformation. Either a rigid sidewall simulation or an actual sidewall panel may be used. If a test fixture with a rigid sidewall simulation is used, the seat/restraint system shall be attached to fittings installed in a test panel equivalent to those used in the actual installation.
(7) Seats that are mounted on a plinth. Where the plinth is used to mount a single seat, and the plinth is attached to the floor, the plinth should be considered as part of the seat assembly as an adaptor and should be deformed as described in paragraph lOb. Any items of mass attached to the plinth need to be represented and included in the dynamic testing.
(8 ) Seats that are mounted on a pallet (e.g., multiple seat rows). The pallet is considered part of the floor structure of the airplane. The seats should be attached to the pallet in a manner representative of the airplane installation. The seat legs should be deformed as described in paragraph lOb.
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, including side -facing seats, both single occupancy and multiple place (e.g.
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. Means 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-facing seats is ongoing; therefore, in the absence of specific compliance guidance, the FAA is prepared to assess side-facing seats on the following basis:
(i) The seat must demonstrate compliance with the structural requirement.
(ii) 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 such a manner that prevents substantial energy absorption by body to body contact (on a 22 par 10
multiple occupancy seat), and which, using the best available engineering judgment, minimizes injury to the occupant(s).
(iii) As research proceeds, the FAA will work toward establishing a more definitive policy with respect to the acceptance of side-facing seats.
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 (see Figure 1).
(1) The fixture shall 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 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 shall be covered with carpet (or other appropriate material) and 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 shall simulate those components. (Note: A footrest is optional for test 2 structural tests--see paragraph 11f). Test fixtures may also be required to provide guides or anchors for restraint systems or for holding instrument panels or bulkheads, if necessary, for the planned tests. If these provisions are required, the installation shall represent the configuration of the airplane installation and be of adequate structural strength.
11. Test Preparation.
a. Preparation for the tests will involve positioning and securing the ATD, the ATD restraint system, the seat, and the instrumentation. This will be 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 will not be 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 Par 10 23
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 perfo rmance, 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.
(4) The friction in limb joints should be set so that they barely restrain the weight of the limb when extended horizontally.
(5) The ATD should be placed in the center of the seat, in as nearly a symmetrical position as possible. The ATD should be placed in the seat in a uniform manner so as to obtain reproducible test results.
(6) The ATD's back should be against the seat back without clearance. This condition can be achieved if the ATD's legs are lifted as it is lowered into the seat. Then, the ATD is pushed back into the seat back as it is lowered the last few inches into the seat pan. Once all lifting devices have been removed from the ATD, the ATD should be "rocked" slightly to settle it in the seat.
(7) The ATD's knees should be separated about four inches.
(8) The ATD's hands should be placed on the top of it's upper legs, just behind the knees. If tests on crew seats are conducted in a mockup that has airplane controls, the ATD's hands should be lightly tied to the controls.
(9) The feet should be in the appropriate position for the type of seat tested (flat on the floor for a passenger seat, on control pedals or on a 45 degree footrest for flightcrew systems). The feet should be placed so that the centerlines of the lower legs are approximately parallel, unless the need for placing the feet on airplane controls dictates otherwise.
c. Seat adjustment. To the extent that they influence the injury criteria, all seat adjustments and controls should be in the design position intended for the 50th percentile male occupant. If seat restraint systems are being tested that are to be used in applications where special requirements dictate their position for landing or takeoff, those positions should be used in the tests.
24 Par 11