Interpretation ID: 77-2.23

TYPE: INTERPRETATION-NHTSA

DATE: 04/28/77

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: Weber Aircraft

TITLE: FMVSS INTERPRETATION

ATTACHMT: ATTACHED TO LETTER DATED 08/16//88, TO GLENN L. DUNCAN FROM ERIKA Z. JONES, REDBOOK A32, STANDARD 207; LETTER DATED 08/30/79 TO ROBER J. WAHLS FROM FRANK A. BERNDT; LETTER DATED 02/01/88 TO ERICA Z. JONES FROM GLENN L. DUNCAN RE UNITED TOOL AND STAMPING INC FMVSS 207 SEATING SYSTEM; LETTER DATED 11/16/87 TO ERICA Z. JONES FROM GLENN L. DUNN RE FMVSS 207 SEATING SYSTEM OCC-1278

TEXT: This responds to your letter of February 25, 1977, requesting an interpretation concerning the force requirements specified in Safety Standard No. 207, Seating Systems, and Safety Standard No. 210, Seat Belt Assembly Anchorages. You ask whether the specified forces are intended to be "limit loads" (those loads under which no permanent set, yielding or permanent deformation is allowed) or "ultimate loads" (those loads under which structural integrity must be maintained even though permanent set, yielding or permanent deformation takes place) (your terms and definitions).

Under the requirements of Standard No. 210, the anchorage of a seat belt assembly must be able to withstand certain designated forces when tested in accordance with the procedures of the standard. Paragraph S4.2.3 of Standard No. 210 provides that permanent deformation or rupture of a seat belt anchorage or its surrounding area is not considered to be a failure, if the required force is sustained for a specified period of time. Therefore, the force requirements of Standard No. 210 could be considered "ultimate loads," as you define that term.

The agency interprets the force requirements of Standard No. 207 to allow some deformation of the seats during the force test, provided structural integrity is maintained. Therefore, the force requirements of Standard No. 207 could also be considered "ultimate loads," as you define that term.

Please note, however, that if seats are displaced to an extent that the agency determines occupant safety is threatened, a determination could be made under provisions of the National Traffic and Motor Vehicle Safety Act (15 U.S.C. @ 1381, et seq.) that the vehicle contains a safety related defect and sanctions could be imposed on the manufacturer.

Please contact our office if you have any further questions.

SINCERELY,

Frank A. Berndt Acting Chief Counsel

Feb. 25, 1977

National Highway Traffic Safety Administration Attention: Chief Counsel's Office

Subject: Motor Vehicle Safety Standard No. 207 & 210

Ref: Telecon G. Cress and R. Nelson, 2-25-77

Our test facility has been approached by several manufacturers of vehicle seating systems. These manufacturers have requested that we test (and provide a report) to the requirements of MVSS Nos. 207 and 210. In reviewing the MVSS requirements, a question has arisen. It is on the definition or interpretation of the phrase, "shall withstand the following forces" as used in MVSS 207, Paragraph S4.2. In the aircraft industry, load or force requirements are usually designated as limit loads (those loads under which no permanent set, yielding or permanent deformation is allowed) or ultimate loads (those loads under which structural integrity must be maintained even though permanent set, yielding or permanent deformation takes place).

As an example, if the structure in Figure 1 (attached) were subjected to a limit load of 20 times the weight of the seat, the seat would retain its full capabilities to function. There would be no permanent deflection or degradation of the structure due to the limit load application. If the structure in Figure 1 were subjected to an ultimate load of 20 times the seat weight, the seat could assume the posture shown in Figure 2 as long as it supported the test load for from 3 to 10 seconds. The question is, "May we consider the forces specified in MVSS 207 (and also MVSS 210) as ultimate loads?"

Thank you for your assistance.

WEBER AIRCRAFT, Division of Walter Kidde & Company, Inc.

Gordon P. Cress Chief, Structures & Test

ATTACH.

DIRECTION OF TEST LOAD

PRE & POST TEST (LIMIT LOAD)

FIGURE 1

DIRECTION OF TEST LOAD

POST TEST (ULTIMATE LOAD APPLICATION)

FIGURE

(Graphics omitted)