Interpretation ID: aiam2366
Senior Engineer
Clayton Dewandre Company Limited
P.O. Box 9
Titanic Works
Lincoln LN5 7JL
England;
Dear Mr. Page: This responds to Clayton Dewandre Company's May 20, 1976, request fo confirmation that its 'Dual Brake Booster' system is designed to conform to the definition of 'split service brake system' and the requirements of S5.1.2 and S5.1.3 specified in Standard N0. 105-75, *Hydraulic Brake Systems*. in unimpaired braking circuits, the primary circuit which is initially powered by the driver's application of pedal force and subsequently supplemented by pressurized fluid from the pump accumulator system, and the secondary circuit which is powered by pressurized fluid from the pump accumulator system. In the event of a primary circuit failure, a mechanical connection unimpaired by a loss of reservoir fluid continues to modulate the secondary circuit. In event of a secondary circuit failure, the driver's pedal application continues to actuate the primary circuit by muscular effort alone. A single master cylinder reservoir is provided to supply the primary circuit. A single pump reservoir supplies the pump, accumulator, and secondary circuit.; As you are no doubt aware, the National Traffic and Motor Vehicl Safety Act does not authorize a 'type approval' of vehicle design as the basis for certification (15 U.S.C. S 1397(a) (1) (A)). Our comments on the description of your system do not relive the vehicle manufacturer of its responsibility to design a system for each of its products that actually complies with the standard's requirements.; From your description of the system, it would appear to qualify as 'split service brake system' as that term is defined in S4 of the standard. You state that, in the event either of indefinite operation. This conforms to the NHTSA's September 14, 1973, letter to Citroen on the meaning of 'unimpaired operation' of a subsystem.; With regard to partial failure performance, your state that the vehicl can meet the requirements of S5.11.2 (inadvertently designated as S5.1.1 in your letter) using either of two subsystems.; With regard to the requirements of S5.1.3 (for inoperative brake powe assist unit or brake power unit), you indicate that the vehicle is capable of stopping within the specified distances of column IV of Table II 'purely by muscular effort of the driver'. By this we assume you mean that the vehicle conforms to the condition required for testing under S5.1.3.1, *i.e.*, with one power unit inoperative and deleted of all reserve capability. Please note that the NHTSA regards the 'pump and accumulator' energy source to constitute a 'brake power unit' and not a 'brake power assist unit', because the described unit 'provides the energy required to actuate the brakes, either directly or indirectly through the auxiliary device, with the operator action consisting only of modulating the energy applica- tion level.' (S4 definition of 'brake power').; We are assuming that Clayton Dewandre does not object to making publi the designs described in your May 20 letter.The NHTSA will place the materials in the public docket three weeks after the date of this letter unless we hear otherwise from you.; Yours truly, Frank Berndt, Acting Chief Counsel