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Interpretation ID: gustback_doorlatch

    Dr. Peter Gust
    Kirchhoff GmbH & Co. KG
    Oststrasse 1
    58553 Halver
    Germany


    Dear Dr. Gust:

    This letter responds to your e-mail and fax inquiries into the application of Federal Motor Vehicle Safety Standard (FMVSS) No. 206, Door locks and door retention components. You asked a question about how a specific back door latch configuration is tested under the procedures specified in the standard. We have addressed your question below.

    Your letter describes a back door that opens upward, with a single latch at the bottom of the door with a single striker on the back door sill. According to the diagrams sent with your letter, the latch is comprised of two sections. When the latch is engaged, (1) the portion of the latch that is attached to the door is oriented perpendicular to the vehicle floor plane (the "upper section"), and (2) the portion of the latch face that interacts with the striker is oriented along a plane that is roughly 45 degrees to the vehicle floor plane (the "lower section"). The diagrams also show that the striker plate is parallel to the lower section, with the striker oriented perpendicular to the striker plate. You asked how the test procedures in Load Test One and Load Test Two of FMVSS No. 206 apply to your latch assembly.

    FMVSS No. 206 specifies requirements for door locks and door retention components including latches, to minimize the likelihood of occupants being thrown from their vehicle as a result of an impact. Under FMVSS No. 206, hinged back doors must comply with several load requirements, including:

    S4.4.1.1  Load Test One. The primary door latch and striker assembly, when in the fully latched position, shall not separate when a load of 11,000 Newtons (2,500 pounds) is applied in the direction perpendicular to the face of the latch (corresponding to the longitudinal load test for side door latches) such that the latch and the striker anchorage are not compressed against each other. When in the secondary latched position, the primary latch and striker assembly shall not separate when a load of 4,450 Newtons (1,000 pounds) is applied in the same direction.

    S4.4.1.2  Load Test Two. The primary door latch and striker assembly, when in the fully latched position, shall not separate when a load of 8,900 Newtons (2,000 pounds) is applied in the direction of the fork-bolt opening and parallel to the face of the latch (corresponding to the transverse load test). Figure 1 depicts the loading direction for this test. When in the secondary latched position, the primary latch and striker assembly shall not separate when a load of 4,450 Newtons (1,000 pounds) is applied in the same direction.

    As indicated in S4.4.1.1 and S4.4.1.2, the orientation of the latch face dictates the direction of the loads. FMVSS No. 206 does not define latch face, but we have stated that SAE J839, Passenger car side door latch systems (JUN91), provides guidance on its meaning (see 60 FR 50124, 50128; September 28, 1995). While SAE J839 does not define latch face, it defines "latch plate" as "the main body or frame for supporting working components, appendages and transmitting or distributing loads to the door structure" (S3.1.1).

    Based on the specifications in S4.4.1.1, Load Test One would be oriented with the lower section of the latch face in question. While S4.4.1.1 does not specifically address testing a latch face that aligns with more than one plane, the section does specify that the latch and striker anchorage should not compress upon application of the load. The intent of Load Test One is to apply the load such that there is no engagement of the latch face by the striker. This is accomplished with your latch assembly by applying the test load in a direction perpendicular to the lower portion of the latch face. By contrast, application of the test load perpendicular to the upper portion of the test face would result in some compression; i.e. , the striker would engage the latch face to some extent, and would thus not test the latch as specified by the standard.

    Regarding the application of Load Test Two to your latch system, again the standard indicates that the direction of force should be oriented with the lower section of the latch face. Load Test Two specifies application of the load in the direction of the fork-bolt opening, parallel to the face of the latch. Figure 1 of FMVSS No. 206 illustrates that Load Test Two is applied in a direction that is parallel to the portion of the latch face that interacts with the striker. On the latch face in question, this corresponds to the lower section. Testing in this manner is consistent with the intent of the standard to test the latch in a manner representative of opening the door.

    Further, applying Load Test One and Two as described would test your latch in a manner consistent with the longitudinal and transverse testing specified for side door latches, respectively. Additionally, orienting the test loads to the lower portion of the latch face would permit testing in accordance with SAE J934, as intended by the agency (see 60 FR 50128).

    I hope that you find this information helpful. If you have any further questions, please contact Mr. Chris Calamita of my staff at (202) 366-2992.

    Sincerely,

    Jacqueline Glassman
    Chief Counsel

    ref:206
    d.11/19/04