Interpretation ID: 09-002613 BMW positioning the seat

Dr. Jan Urbahn

BMW Group

P.O. Box 1227

Westwood, NJ 07675-1227

Dear Dr. Urbahn:

This responds to your inquiry about Federal Motor Vehicle Safety Standard (FMVSS) No. 214, Side impact protection, particularly regarding the standards procedure for positioning the drivers seat for the upgraded moving deformable barrier (MDB) test and the pole test. Your original letter, dated April 28, 2008, was withdrawn by you and later resubmitted, unchanged from the original, on April 29, 2009, in a meeting between Martin Rapaport and Alissa Moulton of BMW and agency staff.[1] Mr. Rapaport also emailed us slides on June 3, 2009, that he had brought to the meeting.

Background

The seat positioning procedure you ask about was adopted by a September 11, 2007, final rule[2] and applies to vehicles on a phased-in schedule beginning with vehicles manufactured on or after September 1, 2010. The seat positioning procedure is set forth in S8.3 for the MDB test and in S10.3 for the pole test. The procedure specifies how the vehicle seat is positioned in these crash tests with regard to an adjustable seat back, head restraint, lumbar support and any other adjustable part of the seat. The procedure specifies how the vehicle seat is positioned with regard to the seat cushions fore and aft location,[3] angle, and height.

Simply stated, the seat positioning procedure describes the following (S8.3.1)[4]:

--lumbar support are in the lowest, retracted or deflated position (S8.3.1.1) and other adjustable parts of the seat that provide additional support are in the lowest or non-deployed adjustment position (S8.3.1.2);

--head restraints are in the highest and most forward position, and adjustable seat backs are in the manufacturers nominal design riding position (S8.3.1.2); and,

--the seat is positioned as follows (S8.3.1.3):

-using specified controls, move the seat to its rearmost position (S8.3.1.3.1);

-using specified controls, determine the full range of angles of the seat cushion reference line (SCRL). Set the SCRL to the middle of the angular range (the SCRL angle)(S8.3.1.3.1);

-maintain the SCRL angle and without using fore and aft control(s), place the cushion to its lowest position (S8.3.1.3.1);

-using only the control that primarily moves the seat fore and aft, move the seat to the mid-travel position (S8.3.1.3.2); and,

-maintain the SCRL angle and without using the fore and aft control(s), set the height of the seat cushion to the lowest height (S8.3.1.3.3).

Discussion

You ask twelve questions about the seat positioning procedure. Questions 1 and 2 (Q1 and Q2) and five (Q5) ask whether the specifications of S8.3 and S10.3 need to be followed in the exact sequence as they are described in the standard, particularly with respect to placement of the head restraints and adjustable seat backs, and the closing of convertible tops. You state that due to the kinematics of the seat adjustment, the sequence of the different steps has a significant influence on the final seat position. You provide as an example that if the head restraint were in its highest position, there could be a collision between the head restraint and the roof liner, which could prevent the seat from achieving the specified seat cushion angle. Conversely, you indicate that if the head restraint were raised after the seat is positioned, the seat cushion angle specified by the standard could be achieved.

Our answer is as follows. It is very important to follow the seat positioning procedure of S8.3.1.3 in the exact sequence described. This is needed to standardize the fore-aft placement, cushion angle, and height. However, the steps described in S8.3.1.1 and S8.3.1.2 for positioning the lumbar supports and other adjustable parts of the seat, the head restraints, and the adjustable seat backs may be deferred until later in the adjustment process if interference of the seat back and head restraint with vehicle components prevents determination of the full range of the SCRL angle or fore and aft seat travel. Thus, the head restraint may be placed in the lowest position while the seat is adjusted and moved to the highest and full forward position after the seat cushion reference point is set to its lowest position (S8.3.1.3.3), as you suggest in your letter. Similarly, the seat back may be placed at the manufacturers nominal design riding position (S8.3.1.2) after completion of the procedure described in S8.3.1.3.3.

You note in your letter that S8.6 of the standard specifies that convertible tops are in the closed position and ask whether the top is closed during the seat positioning procedure. You indicate that if the convertible top were closed during the positioning of the seat, there could be interference between the head restraint and the roof liner, whereas if it were closed after the seat is positioned, the seat cushion angle specified by the standard could be achieved. S8 of FMVSS No. 214 specifies the test conditions for the MDB test. For the test, the convertible top is in the closed position. However, for the pre-test set up, the top may be open to facilitate the positioning of the seats, placement of the test dummies, installation of test equipment, etc.

Your third question asks about a thigh support provided by the Z4 seat and whether it would be positioned in the lowest (or non-deployed) position. The agency addressed a similar issue in an interpretation letter to Chris Tinto, dated August 27, 2004 (copy enclosed). The main portion of the seat cushion would be adjusted to the required height position using the seat cushion reference line angle as the primary control parameter. Other adjustments such as an extendable seat cushion leading edge would be treated as additional support and would be adjusted to the lowest or non-deployed position.

Questions six (Q6) through twelve relate to the procedure in S8.3.1.3 for positioning the vehicle seats fore and aft location, height, and horizontal angle. You state your understanding of the procedure and ask if you are correct. We believe some of your statements, such as those in Q6 and Q7, indicate some confusion. We trust you have a better understanding of the procedure now, in light of our discussion in the background section, and will write back if you still have questions.

Q8 asks about S8.3.1.3.1, which states, among other things, Using any part of any control, other than those just used, determine the full range of angles of the seat cushion reference line and set the seat cushion to reference line to the middle of the angular range. You ask if it is correct that for seats that are equipped with a height adjustment but do not offer a separate seat cushion angle adjustment, that this would determine the height position that they have to be adjusted to (namely the height position where the seat cushion reference line reaches its mid position)? It might be helpful to keep in mind that the procedure of S8.3.1.3 gives priority to the SCRL angle above other factors. We adjust the seat fore-aft in the vehicle and adjust the seat height, as specified in S8.3.1.3 to the extent the SCRL angle can be maintained. That said, assuming we understand your question, our answer is the seat is adjusted to the SCRL angle, and the height range of the seat cushion reference point (SCRP) that allows the SCRL to maintain the mid-angle setting is used to determine SCRP height.
In Q11 and Q12, you make several statements that the leading parameter for adjusting a seat to S8.3.1.3.3 is the seat height and not the SCRL angle. You believe that the seat is brought to its minimum height even if the seat cushion reference line angle can not be kept at the mid range. As explained above, these statements are incorrect. The SCRL angle is the controlling parameter for adjusting the seat, not seat height or any other factor.

We hope this information answers your questions. Please contact Ms. Fujita of my staff at 202-366-2992 if you have any further questions.

Sincerely yours,

Stephen P. Wood

Acting Chief Counsel

Enclosure

ref:214

d.7/24/09