Interpretation ID: nht73-4.16

DATE: 05/03/73

FROM: AUTHOR UNAVAILABLE; Richard B. Dyson; NHTSA

TO: AM General Corporation

TITLE: FMVSS INTERPRETATION

TEXT: This is in reply to your letter of March 22, 1973, concerning the conformity of buses manufactured by AM General Corporation with paragraph S5.1.1 of Standard No. 217, "Bus Window Retention and Release." Your letter states, enclosing a drawing, that the side sash construction in these buses includes an aluminum tie bar that connects the upper and lower portion of the sash, and is located on the inside and at the center of the glass. You state this configuration precludes testing as specified in S5.1.1, which specifies that the head form applying the load be placed at the center of the glazing. You request that the standard be revised to permit testing with the head form located as close as possible to the center of the glazing.

Based on the information you have provided, we are of the opinion that the configuration of this window should be treated under paragraph S5.1 as two separate windows, even though only one sheet of window glazing is used. The tie bar appears to be an integral part of the window sash, and by preventing an occupant from contacting the window at that point, performs essentially the same function as a conventional divider strip. Consequently, we would expect to test this window configuration by applying the head form to the center of each half of the glazing surface.

Yours Truly,

AM General Corporation

March 22, 1973

FEDERAL MOTOR VEHICLE SAFETY STANDARDS

(49 CFR PART 571)

MOTOR VEHICLE SAFETY STANDARD NO. 217

"BUS WINDOW RETENTION AND RELEASE"

Office of the Chief Counsel National Highway Traffic Safety Administration

AM General Corporation, a wholly-owned subsidiary of American Motors Corporation, is in the process of designing a transit bus for use by Transit Authorities in the United States.

The side window sash and rear window sash construction is so designed as to make it virtually impossible to conform to the required test procedure described in FMVSS No. 217 - Bus Window Retention and Release.

Paragraph S5.1.1 states: "An increasing force shall be applied to the window glazing through the head form specified in Figure 4, outward and perpendicular to the undisturbed inside surface at the center of each sheet of window glazing, with a head form travel of 2 inches per minute."

AM General's side sash construction is as depicted on the enclosed AMG Drawing No. 5955931. Your attention is directed to the center of the glazing which reflects that at this location you will find an aluminum "tie bar" which connects the upper and lower portion of the aluminum sash.

Since this "tie bar" is an integral functional item and its location is at the center of the glazing, but not integral with respect to the glazing, it is obvious that it precludes testing according to the aforementioned test procedure of Paragraph S5.1.1.

Therefore, AM General requests clarification whether it is permitted by this standard to locate the contact of the head form as close as possible to the normal center of the glazing, without coming in contact with the "tie bar," as shown on the enclosed drawing. Should this procedure not be allowed under the current Standard No. 217, AM General requests that the requirement be revised to permit an option to test with the head form located as close as possible to the normal center of the glazing.

A similar sash type rear window with a positive lock mechanism and with a "tie bar" as herein described will be used; and it is, therefore, requested that the offset(Illegible Word) be approved or revision to the standard apply also to rear windows.

We respectfully request your prompt attention and reply. Should you require additional information pertaining to our design, do not hesitate to call on us.

Sincerely,

F. A. Stewart Vice President Safety & Reliability

Enclosure

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