Interpretation ID: nht76-3.43

DATE: 02/18/76

FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA

TO: Oshkosh Truck Corporation

TITLE: FMVSS INTERPRETATION

TEXT: This responds to Oshkosh Truck Company's January 22, 1976, question whether a vehicle that complies with S5.1.1 of Standard No. 121, Air Brake System, when it is moving must also comply with the requirement when it is stationary. Section S5.1.1 specifies an air compressor of sufficient capacity to increase air pressure in the supply and service reservoirs from 85 p.s.i. to 100 p.s.i. within a limited period when the engine is operating at the vehicle manufacturer's maximum recommended rpm.

Section S5.1.1 does not specify whether or not the vehicle is moving as a test condition for the requirement. In view of the absence of this test condition, the NHTSA will resolve differences in this test condition in the manufacturer's favor if they affect the outcome of testing.

Yours truly,

ATTACH.

January 22, 1976

T. Herlihy -- National Highway Traffic Safety Administration

Dear Mr. Herlihy:

Based on discussions with Sid Williams it is my understanding that section 5.1.1 of FMVSS 121 does not require that compressor buildup time be tested when the vehicle is stationary. If the vehicle meets compressor buildup time when it is moving, but exceeds compressor buildup time when the vehicle is stationary, it is my understanding that the vehicle qualifies. Please confirm.

Sincerely,

Danny Lanzdorf -- Supervising Engineer

cc. J. Westphal; D. Thekkanath