Brian,
Perhaps some clarification is necessary here; at the time that this report was produced - i.e November 1984, the members of the HARP (a committee set up by the Airworthiness Requirements Board (ARB)) would have been aware of the contents of the proposed amendment to FAR 29 but would have had no direct interest because Certification in the UK was to an alternative set of requirements - i.e. BCARS. (Without checking, I would make the assumption that this requirement was contained in BCARS. It was also not clear at that time that the UK would eventually be forced to abandon BCARS in favour of FARs (in the form of harmonised JARs).)
Perhaps a more interesting fact is that in the
proposed NPRM, the text was slightly different.
3-46. By amending Sec. 29.927 by revising paragraphs (c), (d) (introductory text), (d)(2), and by adding new paragraph (f) to read as follows:
Sec. 29.927 Additional tests.
* * * * *
(c) Lubrication system failure. For lubrication systems, the function of which is required for operation of the rotor drive system, the following apply:
(1) Category A. It must be shown by tests that each rotor drive system, where the probable failure of any element could result in the loss of lubricant, is capable of continued operation, although not necessarily without damage, for a period of at least 30 minutes at a torque and rotational speed prescribed by the applicant for continued flight, after indication to the flightcrew of the loss of lubricant.
By the time the requirement was finalised as amendment 29-26 in 1988, the rule contained the
conditioning text we now see. Normally one can examine the explanatory text of the final rule and establish why the text has been subsequently amended. In the case of the text of 29.927(c), the explanatory text is as follows:
Proposal 3-46. The notice proposed several amendments to Sec. 29.927. Paragraph (c) is changed by revising and extending the rotor drive system lubrication failure test requirements for Category A rotorcraft and by clarifying the corresponding test requirements for Category B rotorcraft. Category A aircraft must have significant continued flight capability after a failure in order to optimize eventual landing opportunities. However, indefinite flight following the lubrication system failure is not expected. The changes to the Category B rotorcraft drive system lubrication failure test requirements are largely for clarification and are not substantive.
A commenter notes that paragraph (c), as proposed, could be interpreted to preclude credit for auxiliary lubrication systems or to require consideration of lubricant failures to self-lubricated bearings. This was not intended, and the wording of paragraphs (c)(1) and (c)(2) has been revised to eliminate this possible ambiguity.
The 'law of unintended consequences' in action?
By putting in this clarification, there is no intent to reopen the discussion on the 30 minute run-dry capability (and the reason why it was not underlined in my previous post) only to clarify the extract from the HARP report.
Jim