APPENDIX 4. PROCEDURE FOR DEMONSTRATING COMPLIANCE WITH
HIC FOR REPETITIVE SEAT ROWS (CONTINUED)
(c) Conduct a test of the seat pitch and yaw angle per paragraph (a) of this paragraph) with the yaw direction, such that the ATD head strikes the side of the seat without the seat recline mechanism (Zone B test).
NOTE: It is common for the recline mechanism to be positioned on the left side of some seat backs and the right side of other seat backs of the same assembly. Therefore, the seat-to-seat HIC test for Zone A and Zone B can usually be accomplished in one two row test using two instrumented ATD’s with the yaw direction set to effect a head strike in Zone A by one ATD and Zone B by the other ATD. Alternatively, it may be possible to relocate one recline mechanism for test purposes. If this method is chosen, care should be taken to not alter the basic design. The intent of this procedure is to create a mirror image of the actual part, to simplify testing.
(4) For the same seats identified in paragraph (3) above, installed parallel to each other:
12 inches Additional Zone for 6 inches Zone C Staggered Seats Zone A Zone B Recline Non-Recline Control Control Side Side
Figure A4-2
APPENDIX 4. PROCEDURE FOR DEMONSTRATING COMPLIANCE WITH
HIC FOR REPETITIVE SEAT ROWS (CONTINUED)
(a) Determine the point of initial head contact by the 50% male ATD at the minimum pitch identified in paragraph 1a(2) and at 0 degrees yaw angle. If the 50% male ATD head path does not contact the seat forward, move the seats 3 inches closer together and locate the initial head contact using the 50% ATD head path. If, after moving the seats closer, there is still no contact with the 50% ATD head path, a row-torow HIC test is not required.
(b) Evaluate the area defined by a 6-inch high by 12-inch wide rectangle centered on the initial head contact point for structures that differ significantly from the initial contact point (that is, telephone handsets, video screens, and oxygen mask container units) such that the seatback is not homogeneous.
(c) Determine which structure in the 6-inch by 12-inch rectangle is the most rigid in the direction perpendicular to the aft seat back structure.
(d) Conduct a test designed to produce ATD head contact with the structure identified in paragraph (c) above (Zone C test).
NOTE: Typically, the Zone C test will be conducted at the minimum seat pitch and 0 degrees yaw. However, when the area of concern (as identified in paragraph (c) above) is not at the center of the 6 inch by 12 inch rectangle, the relative position of the seats in the two row set up must be adjusted to produce the ATD head contact desired. Lateral offset or vertical adjustment of the seats’ relative position will ensure that a comparable head impact velocity as that measured from the normal position Zone C test is achieved. Ot her methods that achieve the same objective are acceptable.
(5) For seats installed at an angle with respect to the airplane’s longitudinal axis—parallel rows or non-parallel rows (for example, the rows in the tapered section of the airplane):
APPENDIX 4. PROCEDURE FOR DEMONSTRATING COMPLIANCE WITH
HIC FOR REPETITIVE SEAT ROWS (CONTINUED) Strike Point
For Angled Installation
Head Strike
Offset
Strike Point
For Parallel Installation
Fwd Figure A4-3
(a) Determine the head strike location of the 50th percentile male ATD for the seats in the yawed installation configuration (inertia load direction parallel to the airplane’s longitudinal axis) using the path of the top of the ATD head.
(b) Determine the head strike location of the 50th percentile male ATD for the same seats in a 0 degrees yaw; parallel row installation configuration at the same seatto-seat pitch as the yawed installation configuration.
(c) Calculate the “head strike” offset—the lateral distance between the two contact points determined in paragraphs (a) and (b) above, measured on a plane perpendicular to the airplane’s longitudinal axis.
(d) If the cumulative offset between the staggered seats plus offset due to the installation angle is 6.0 inches or less, the additional seat angle may be neglected for the row-to-row HIC tests.
APPENDIX 4. PROCEDURE FOR DEMONSTRATING COMPLIANCE WITH
HIC FOR REPETITIVE SEAT ROWS (CONTINUED)
(e) If the cumulative offset between the staggered seats plus the offset due to the installation angle is greater than 6.0 inches, the additional seat angle must be included in the evaluation identified in paragraph (3)(a) above and included in the test setup, as necessary.
(6) For seats which have staggered seat places, row-to-row:
NOTE: Staggered seating can result from a change in the number of seat places, different width seat assemblies, or installation on staggered seat tracks to accommodate the airplane taper section.
(a) If the row-to-row seat place is staggered and the cumulative offset between the staggered seats plus the offset due to the installation angle is 6.0 inches or less, the lateral offset between the seat places may be neglected and the row-to-row HIC tests identified above may be conducted without including the lateral offset.
(b) If the row-to-row seat place is staggered more than 6.0 inches, the actual staggered installation configuration must be considered. This may broaden the Zone C evaluation window defined in paragraph 4b and include more objects to consider for head strike. If a test re presentative of the actual staggered installation configuration is determined to be required (either in addition to or in lieu of one of the baseline tests identified above), the test set-up (yaw direction and angle and seat pitch) must be that which is determined to be critical for HIC.
NOTE: A staggered seat installation may prove to be the critical HIC evaluation for the airplane installation, if contact with armrests or other hard structure occurs. Such an in stallation may require testing beyond the Zone A and B evaluations of paragraph 1a(3) of this appendix.
(7) For row-to-row HIC tests:
(a) Since this test is not considered the critical case used to demonstrate compliance to structural criteria, non-production seat tracks may be used (for example, steel track or seat track from a different airplane type).
(b) Any seat or seat place that allows the ATD to strike the intended target area is acceptable.
(c) It is acceptable to conduct the test with no ATDs in the forward seat row. The components attached to the seat ba ck and the structure of the seat back that influence HIC must all be representative of the production seat for all seat backs or armrests that will be contacted by the ATD during the HIC test. This includes the mass and weight of the seat back, breakover mechanism, the structure of the armrest, and 91
APPENDIX 4. PROCEDURE FOR DEMONSTRATING COMPLIANCE WITH
HIC FOR REPETITIVE SEAT ROWS (CONTINUED) contact area of the armrest. Other components or parts of the seat may be nonrepresentative or deleted from the forward seat.
(d) Weights representing under-seat baggage are not required for either seat row. All components that are part of the occupied seat should be represented, at least, by ballast.
(e) Life vests and weights representing literature pocket contents are not required for either seat row.
(f) A representative floor must be included in the test setup for the ATD’s feet.
(8) For each row-to-row HIC test, a post-test evaluation of the high-speed film/video and evaluation of the seat back (for example, chalk mark) must show that the intended ATD head strike was achieved with regard to location and head impact (solid head strike and not a glancing blow). If th e intended ATD head strike was not achieved, an adjustment to the test setup and a retest may be required.
2. Collection of ATD Head Path Data to demonstrate no head contact with airplane interior features (usually front-row seats).
NOTE: It is acceptable to collect ATD head path data in the 16g longitudinal structural test.
NOTE: This procedure only selects a test article for the collection of head path data. Additional analysis will be required to assess the specific interior configuration (for example, translating the yawed head path into airplane coordinates and evaluating the airplane interior for potential head strikes using the head path data collected.).
a. For each family of seats
(1) Conduct a 16g longitudinal dynamic test of the seat selected in the 16g longitudinal structural test identified in paragraph 5 of this AC. If more than one seat is identified in paragraph 8 for the 16g longitudinal structural test , select the seat with the greatest overhang to collect head path data. It is acceptable to use the opposite-hand part for this seat.
(2) The occupancy used in the 16g longitudinal structural test must be used for this test.
APPENDIX 4. PROCEDURE FOR DEMONSTRATING COMPLIANCE WITH
HIC FOR REPETITIVE SEAT ROWS (CONTINUED)
(3) The test will be conducted with no yaw, no pitch, and no roll.
Representative seat track is not required for this test, since structural attachment substantiation is not under consideration (for example, steel tracks may be used on this test).
(4) The head path data of the ATD expected to move the furthest forward due to structural deformation (usually in the most overhung seat place) should be collected.
The most overhung seat place is the outer (left or right) seat place with the greatest distance from the centerline of the seat leg to the outer edge of the seat.
NOTE: It is acceptable to conduct additiona l head path tests of this type on less critical seats or head path da ta may be collected on more than one ATD on the same seat to collect head path data for specific occupant locations.
NOTE: It is also acceptable to install a bulkhead or rigid vertical wall at the minimum design setback from the bulkhead into the test setup for the purpose of showing no ATD head contact during the test. It is not required for the bulkhead used in the test setup or material to be representative of the production airplane interior component. This is because the test is conducted to establish if head contact occurs for a specific setback distance and the location of head contact by a 50th percentile ATD in those cases where it does. It is the responsibility of the seat installer to use this data to demonstrate an acceptable installation.
One way to use this data to demonstrate compliance for front-row HIC is to digitize the head path, then use the data to show no head contact for the range of occupants.
(5) Representative mass for baggage, life vests, and literature pocket contents must be installed at each seat place, regardless of seat occupancy. Items of mass on the seat (for example, under-seat IFE boxes) may be replaced by ballast.
(6) Retention of items of mass need not be demonstrated in this test, and items of mass may be restrained for the test.
(7) A representative floor must be included in the test setup for the ATD’s feet.
3. Large Clearance Installations. Installations behind a nother seat or interior component where the nominal distance between the Seat Reference Point (SRP) and the aft-most point on the seat or interior component is greater than 50 inches do not require dynamic test data to substantiate the HIC criteria. This is based on substantial industry data that demonstrates a seat passing structural criteria will not have a head path that extends beyond 50 inches from SRP.
APPENDIX 5. PROCEDURE FOR SUBSTANTIATING RETENTION
OF ITEMS ATTACHED TO SEATS
1. Seats typically consist of components that perform the actual function of occupant restraint and components that are ancillary to that function. In this latter category, equipment may be carried on the seat which could also be installed at other locations in the cabin. For the purposes of substantiating retention, the following categories of items have been established:
a. Items that Affect Dynamic Performance of Seat. These may include deployable items, such as legrests, video arms, food trays and privacy dividers that are part of the seat. The presence or deployment of these items may affect the dynamic response of the seat or passenger egress. Egress can be aff ected in the way discussed in Appendix 2 or by introducing a tripping hazard. For these items, it is necessary to substantiate the production means of attachment and to assess the potential for deployment using dynamic tests. Figure A5-1 illustrates the principle.
Deployable Item Seat Structure 9g static 16g dynamic Deployment Arm Figure A5-1
(1) Initial certification must be done as part of the dynamic testing (that is, no static alternative). Components that do not influence retention/deployment (for example, the video monitor attached to the video arm) may be dummy units or representative masses.
(2) For substantiating changes after the initial certification, component level dynamic tests may be considered. Also, static comparative analysis to a previously dynamically qualified configuration may be acceptable.
(3) If a component partially deploys during the dynamic test, a load of 10 pounds should be applied along the inertial load path of the test to evaluate the potential for full deployment. The load should then be removed. After the load has been removed, a determination will be made if “normal passenger movement” would move the 94
APPENDIX 5. PROCEDURE FOR SUBSTANTIATING RETENTION
OF ITEMS ATTACHED TO SEATS (CONTINUED) component out of the way (see Appendix 2). Egress will be evaluated after this consideration has been applied.
(4) As a result of a test failure, a design change may be required. If it is clear that the deployment could be solved by adding additional strength capability to the system while considering the effects of structural deformation during the dynamic event, the revised retention mechanism may be substantiated by a 24g static test or analysis.
b. Items that are Part of Seat But do not Affect Dynamic Performance of Seat These items include electronic boxes, telephones, game controllers, passenger control units (PCU’s), power ports (power plugs), audio jacks, video screens, motors, power control boxes, junction boxes, emergency lighting, cushions, and consoles (armrests) that are not part of the primary structural load path of the seat. These items are typically integrally attached to the seat and not intended to be removed during operation.
(1) These items are considered part of the seat and, therefore, are required to show compliance with § 25.562 for retention. For these items, it is necessary to substantiate the production means of attachment. Compliance may be shown either via dynamic test or, since the dynamic response of the seat is not affected, by static test or analysis. If static substan tiation is chosen, a 24g static assessment should performed.
The value of the static substantiation has been selected based on past practice and confidence in this method. Figure 2 illustrates the principle.
(2) A 24g static assessment may be utilized for certain in-arm deployable components, such as in-arm monitors and foodtrays, to assess whether these items will remain attached and stowed during the dynamic event. If these items remain stationary on the seat (considering the effects of structural deformation during the dynamic event) and do not deploy under the 24g static load condition, they fall into the category of items that are part of the seat but do not affect the dynamic response of the seat.
(3) Changes to the means of attachment subsequent to the original certification may be substantiated by comparative analysis.
Equipment
01/10/2006 AC 25.562-1B APPENDIX 5. PROCEDURE FOR SUBSTANTIATING RETENTION
OF ITEMS ATTACHED TO SEATS (CONTINUED) Seat Structure Attachment Bracket Equipment 9g static 16g dynamic 16g dynamic or 24g Static Figure A5-2
c. Operationally Removable Equipment Mounted to Seats. Equipment that is mounted to seats but is intended to be removed from the seat during operation is not considered part of the seat for purposes of establishing restraint. This equipment includes fire extiguishers, oxygen bottles, protective breathing equipment, and flashlights. This equipment would be s ubstantiated for the conditions of § 25.561 and any flight loads. Figure A5-3 illustrates this approach.
Attachment Bracket Seat Structure
9g static 16g dynamic Figure A5-3
d. Lifevests. Lifevests are considered part of the seat and, therefore, require substantiation to the dynamic requirements. However, due the variation possible in lifevests over the family of seats, a simplified method of compliance is needed. The lifevest retention means should be shown to retain an approved lifevest under the 96
Lifevest
AC 25.562-1B 01/10/2006 APPENDIX 5. PROCEDURE FOR SUBSTANTIATING RETENTION
OF ITEMS ATTACHED TO SEATS (CONTINUED) dynamic conditions. (See Figure A5-4.) Once this is done, any other approved lifevest may be installed in the lifevest stowage location without further qualification, provided the weights is not increased. It may be advi sable to increase the weight of the tested lifevest with ballast to avoid this issue in the future. Observe that the retention requirements do not address lifevest accessibility which is still a requirement to be assessed for each lifevest installation.
Seat Pan Lifevest Pouch 9g static 16g dynamic 16g dynamic or 24g Static Figure A5-4
e. Very Lightweight Items. Items weighing less than 1/3 pound are not required to be substantiated explicitly. Examples include ash trays, proximity lighting, passenger control units, PC power outlets, decorative trim, audio jacks, cocktail trays, cup holders, and rub strips. These items will typically have very high margins of safety and will not influence the dynamic behavior of the seat. Wiring harnesses are considered lightweight, irrespective of their actual weight, and do not require explicit substantiation.
2. Irrespective of how items are qualified, in order for the seat itself to meet the dynamic test requirements, it must be capable of carrying all loads resulting from all masses attached to the seat.
a. This means that certain items that are qualifed only to the 9g static load requirements must either be artificially restrained for the dynamic tests or be represented by ballast at an appropriate location relative to the center of gravity.
b. If the item is part of the primary or secondary load path or influences occupant injury or egress, it must be representative of production parts on the dynamic test, even if it might otherwise fall into one of the other categories.
APPENDIX 5. PROCEDURE FOR SUBSTANTIATING RETENTION
OF ITEMS ATTACHED TO SEATS (CONTINUED)
3. Dynamic retests should be very rare for any issues of retention of items of mass.
Retest is required if an item exceeding 3 percent of the empty weight of the seat assembly detached prior to the seat achieving peak reaction loads. In all other cases, the consequences of the failure to retain an item, the effect on the seat, and the effect on egress capability should be assessed to determine whether a retest is necessary. In particular, the load history of the seat reactions should be checked to detemine whether the item was retained until after the seat reached its peak load reactions. If it was, the item should be able to be substantiated statically using the appropriate load factors as discussed above, assuming the seat did not fail some other performance parameter.
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