Interpretation ID: aiam3287
Group Director
Engineering
Heavy Vehicle Systems Group
The Bendix Corporation
901 Cleveland Street
Elyria
OH 44035;
Dear Mr. Hildebrandt: This responds to your April 8, 1980, letter asking for a interpretation of section 5.2.1.1 of Standard No. 121, *Air Brake Systems*. In particular, you ask whether your system complies with the provisions of that section which require that vehicles have a reservoir capable of releasing the parking brakes in the event of an emergency failure of the service brake system. You indicate that your system is in compliance with the intent of this section but may not be in technical compliance with the actual requirements. Nonetheless, you believe that your system complies based upon a letter of interpretation made by the agency to Berg Manufacturing Company dated August 27, 1979.; The August letter to Berg to which you refer in your letter wa conditioned upon our reading of the facts as stated by Berg in their letter. That letter as it applied to section 5.2.1.1 was not an interpretation of the standard, but rather an assessment by the agency as to whether we believed that the Berg system would comply with the requirements. At that time and based upon the given facts, we stated to Berg that we felt that their system would comply.; The agency has always been reluctant to issue such letters, because i is impossible to determine compliance based upon a manufacturer's description of its vehicles or from vehicle drawings. It is necessary for the agency to conduct tests to be certain whether a vehicle will comply. Accordingly, the agency always indicates in its letters that any assessment of compliance is contingent upon the description made in the manufacturer's letter, and that our opinions only reflect our engineering expertise and in no way bind the agency should we test the vehicle and find a noncompliance. In fact, we have frequently indicated to manufacturers that these letters are of little or no value to them.; Subsequent to the issuance of the Berg letter, the agency has receive a clearer picture of how the Berg system operates. We have notified that company that their system does not comply with the requirements of the standard. Berg has indicated to the agency that they consider their system to be as good as any that is in complete compliance with the standard and has petitioned the agency to amend the standard in a way that would permit their system. The agency is now looking into the Berg request. We suggest that you closely follow that rulemaking action.; With respect to your system, it appears that it too would not compl with the technical requirements of the standard, because your system does not have a reservoir capable of releasing the parking brakes in the event of service brake failure. Although the agency appreciates your argument that your system meets the intent of the standard for the release of parking brakes when the service brake system fails, nonetheless the standard is specific in its requirement that a reservoir be provided that is capable of releasing the parking brakes. We cannot by interpretation remove the reservoir requirement. Our rulemaking effort with respect to the Berg petition will address the question of whether the reservoir requirement remains necessary in the standard.; Sincerely, Frank Berndt, Chief Counsel