Interpretation ID: nht76-4.18
DATE: 03/31/76
FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA
TO: Adams County
TITLE: FMVSS INTERPRETATION
TEXT: This responds to your March 5, 1976, request for written permission to deactivate the "121 brake system" of a school bus manufactured from a Ford chassis with a Kelsey-Hayes antilock system.
From the description of the problems you have encounted with this vehicle, I assume that you do not intend to disconnect the entire "121 brake system", but only one or more antilock systems installed in satisfaction of the "no lockup" requirements of S5.3.1 of Standard No. 121, Air Brake Systems. The National Highway Traffic Safety Administration (NHTSA) has made a finding that early models of the antilock system supplied on transit and intercity buses is characterized by malfunction that warrants its deactivation until a correction is fully developed. This finding was not made with regard to the Kelsey-Hayes system that equips your vehicle.
Section 108(a)(2)(A) of the National Traffic and Motor Vehicle Safety Act (15 U.S.C. @ 1397(a)(2)(a)) prohibits, with one exception, knowing disconnection of the antilock system by manufacturers, distributors, dealers, or repair businesses. A person that does not fall into those categories is not prohibited from disconnection of the system. Other State or Federal requirements, such as those of the Bureau of Motor Carrier Safety, may prohibit disconnection. In any case, the NHTSA urges that you not disconnect safety devices without consulting the vehicle manufacturer with regard to the safest configuration of the vehicle.
SINCERELY,
School District No. 12
MEMO NO: B-0093
DATE: MARCH 5, 1976
TO: CHIEF COUNCIL NATIONAL HIGHWAY TRAFFIC ADMINISTRATION
FROM: RON STACY SUPERVISOR OF TRANSPORTATION
RE: DE-ACTIVATE 121 BRAKES
A letter to Dr. Neil McCormick, (attached), telephone conversation with Brad Marks, "National Highway Safety Administration", Colorado, Dr. Steve Sacks, "National Highway Traffic Safety", Washington, D.C., explaining existing problems with the 121 brake, (Kelsey-Hayes, Ford Chassis).
December 1975, Kelsey-Hayes representative performed an inservice workshop. Problems still exist!
Refer, Fleet Maintenance Magazine, February 1976 issue, page 61. Washington Report; QUOTE: "NHTSA has also tentatively determined, at this writing, that virtually the only anti-lock system currently available for buses "is characterized by malfunction that warrants its deactivation on all vehicles on which it is installed while a correction is fully developed." UNQUOTE.
Request permission, in writing, to deactivate the 121 brake system, until such time corrections are complete.
Your cooperation and expedience is greatly appreciated.
RON STACY
School District No. 12 Adams County
TRANSPORTATION DEPARTMENT
MEMO NO: B-0085
DATE: NOVEMBER 13, 1975
TO: DR. NEIL MCCORMICK SUPERVISOR OF SUPPORTING SERVICES UNIT COLORADO DEPARTMENT OF EDUCATION
FROM: ROW STACY
REF: 121 BRAKES
1. Frequently one brake will grab at low speed.
2. Occasionally brakes will fade.
3. Occasionally all four wheels will lock-up on panic stop.
4. Occasionally brakes will fade completely: gradual stop, below 15 m.p.h.. Then, brakes will grab as if panic stop condition existed.
If I can be of further assistance, please do not hesitate to call.