Interpretation ID: aiam2458
Engineering
FWD Corporation
Clintonville
WI 54929;
Dear Mr. Steenbock: This responds to FWD Corporation's October 15, 1976, request to kno whether a truck that complies with the requirements of Standard No. 121, *Air Brake Systems*, would continue to comply after the addition of another parking brake system (hand-operated mechanical, operating on the driveline) or another service brake control (piped to either or both sides of a split system).; Standard No. 121's requirements for braking systems does not preclud the addition of an additional braking system. The agency would not consider the requirements of S5.6.4 to prohibit an additional parking brake control.; Standard No. 121 does not prohibit installation of more than on service brake control. The installation of a hand- operated control lever that your letter appears to describe would not of itself violate the standard's requirements. If the hand control were piped into both systems, however, a failure introduced into the control would probably result in violation of S5.7.1, which requires certain secondary braking performance following a single failure introduced into the service brake system.; Sincerely, Frank A. Berndt, Acting Chief Counsel