[Federal Register Volume 65, Number 145 (Thursday, July 27, 2000)]
[Notices]
[Pages 46193-46194]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-18991]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration


Guidance for Demonstrating Compliance With Seat Dynamic Testing 
for Plinths and Pallets

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of interim means of compliance.

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SUMMARY: This notice provides clarification of acceptable interim means 
for demonstrating compliance with the airworthiness standards for seats 
mounted on adapter plates of transport category airplanes. It is 
necessary to give the public guidance in this area and is intended to 
be used as a means of compliance until the FAA publishes superseding 
document(s).

FOR FURTHER INFORMATION CONTACT: Federal Aviation Administration, 
Attention: Jeff Gardlin, Airframe/Cabin Safety Branch, ANM-115, 
Transport Airplane Directorate, Aircraft Certification Service, 1601 
Lind Avenue SW., Renton, WA 98055-4056; telephone (425) 227-2136, 
facsimile (425) 227-1320.

SUPPLEMENTARY INFORMATION: The information contained in this notice was 
taken directly from FAA Memorandum No. 00-115-7, dated May 1, 2000.

    ``The purpose of this memorandum is to transmit acceptable 
interim means to demonstrate compliance with Sec. 25.562 of the FAR 
[Federal Aviation Regulations] for seats installed on adapter 
plates, sometimes referred to as ``plinths'' or ``pallets''.
    ``The attachment addressed a specific type of installation, for 
which the guidance contained in Advisory Circular (AC) 25.562-1A 
[Dynamic Evaluation of Seat Restraint Systems & Occupant Protection 
on Transport Airplanes], as clarified by Memorandum No. 00-115-3, 
may not provide sufficient information. Recent installations of 
multiple single-place seats into adapter plates, with

[[Page 46194]]

the adapter plate installed into the airplane seat track (or other 
structure), have generated questions as to the proper certification 
procedure. In these cases, no dynamic testing incorporating the 
adapter plates was performed. The attached guidance addresses that 
issue.
    ``This guidance is interim, because additional data are needed 
to asses the interaction of seats/adapter plates/airframe. However, 
there are very near term projects where certification criteria are 
required before such data will be available. This guidance may be 
used until the FAA publishes a superseding document(s).
    ``Acceptable Interim Approach for Near Term Executive Interior 
Deliveries for Multiple Single Seats Mounted to an Adapter-Plate:
    ``Issue:
    ``Multiple single seats that are mounted to a single adapter-
plate in the aircraft, are being tested to the 16g dynamic load 
conditions without the adapter-plate. The adapter-plate, which is 
attached to the aircraft seat tracks and, at times, to other 
attachment `hard points', provides the load path to the aircraft 
structure. As a result of the adapter-plate not being incorporated 
in the test, it is unknown whether or not the seat-to-adapter-plate 
attachment, the adapter-plate itself, and the adapter-plate-to-
aircraft-structure/seat track attachment are capable of reacting and 
distributing the seat loads into the aircraft structure.
    ``It is necessary to ensure that the seat remains attached to 
the aircraft floor structure under the prescribed 16g dynamic load 
condition. Failure in any of these load path details may result in a 
seat becoming detached from the aircraft floor structure. Therefore, 
the load path between the seat and aircraft floor structure must be 
shown to be capable of transferring the 16g seat dynamic loads.
    ``For the load path components between the seat leg attachments 
and the aircraft seat track or floor fittings, which were not 
represented/substantiated in the 16g dynamic seat test, a stress 
analysis of those details, using the peak loads recorded during the 
16g dynamic tests, may be performed as an acceptable interim means 
of compliance to Sec. 25.562(b) as provided below. Due to the 
limited amount of data available to assess the dynamic performance 
of this particular type of seating installation (seat/adapter-
plate), this is interim action until such data are obtained to 
support policy addressing the subject installations. The FAA has 
identified that data from tests (to be performed possibly by CAMI) 
utilizing seats mounted on adapter-plates are needed to support 
long-term policy and guidance.
    ``Conditions necessary to use this interim approach are:
    ``--Each seat type (without adapter) has been dynamically tested 
in accordance with Sec. 25.562, including pitch and roll.
    ``--The tested means of attachment is consistent with attachment 
of the seat to the adapter-plate.
    ``--Airplane floor warpage is addressed for the adapter-plate 
installation by providing an adequate number of distributed 
attachments of the adapter-plate to the airplane floor structure. 
The number of attachments will depend on the design of the adapter-
plate and positioning of the seats on the plate. Typically the 
number of attachments will exceed the number of seat-to-adapter-
plate attachments and shall not be less than the number of seat-to-
adapter-plate attachments. The attachments of the adapter-to-
aircraft structure must be structurally adequate to accommodate the 
dynamic loads and floor deformation.
    ``--Compliance with Sec. 25.561 is achieved.
    ``If the actual attachment of the seat to the adapter-plate was 
not represented during the 16g dynamic seat test, it must be shown 
that the retention of the seat to the adapter-plate will not be 
compromised when the seat legs are subjected to the required pre-
test pitch and roll conditions of Sec. 25.562(b)(2). Testing of this 
condition may not be necessary if the attachment retention design 
and strength are shown to be capable of accommodating the dynamic 
loads and deformations.
    ``Analysis of load path components not tested:
    ``--Analysis of the seat-to-adapter-plate interface. It Must be 
shown that the seat/plate attachment is capable of reacting the 
measured peak 16g seat loads. The analysis must take into account 
eccentricities of load path and adapter-plate deformations that may 
induce prying (bending) loads at the attachment.
    ``--An analysis of the adapter-plate. It must be shown that the 
adapter-plate is capable of transferring the measured 16g peak loads 
from the seat-to-adapter-plate interface to the interface of the 
adapter-plate-to-aircraft floor structure (seat track lips and `hard 
points').
    ``--Analysis of the adapter-plate-to-floor-structure interface. 
The aircraft seat track lips must be shown to be capable of reacting 
the measured peak 16g seat test load as distributed by the adapter-
plate from the seats. The analysis must take into account 
eccentricities of load path and adapter-plate deformations that may 
induce prying (bending) loads at the attachment. In the case of hard 
point installations, the interface would be taken to the point at 
which the hard point interfaces with the aircraft floor structure 
(e.g., floor beam).

    Note: If a positive margin of safety cannot be achieved in the 
above analysis, either testing of the seat with the adapter-plate or 
redesign of the deficient interfaces will be required for compliance 
to Sec. 25.562.

    ``If the actual seat/plate/aircraft-floor structure installation 
is planned to be tested, but the rigidity of the adapter-plate 
precludes the pre-test floor deformation condition from being 
performed, segments of the adapter-plate can be used for the 
interface between the seat and aircraft seat track section. This is 
in lieu of using the full plate. This will require however, that 
multiple attachments of the adapter-plate to the aircraft floor 
structure be provided. The intention of providing multiple 
distributed attachments is to indirectly address the potential 
deformation between the airplane floor structure and the plate. The 
number of attachments will depend on the design of the adapter-plate 
and positioning of the seats on the adapter-plate. The attachments 
of the adapter-plate-to-aircraft structure must be structurally 
adequate to accommodate the aircraft floor deformation.
    ``The FAA is also preparing a policy statement on the broader 
issue of compatibility of the seat installation with the airframe. 
This future policy statement will address this issue, and others, 
where they may be a question of the dynamic performance of the seat 
producing loads that exceed the structural capability of the 
airframe.''

    Issued in Renton, Washington on July 14, 2000.
Donald L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service, ANM-100.
[FR Doc. 00-18991 Filed 7-26-00; 8:45 am]
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