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Recommendation issued to: Civil Aviation Safety Authority

Recommendation details
Output No: R19990109
Date issued: 16 December 1999
Safety action status:
Background: Why this Recommendation was developed

Output text

The Bureau of Air Safety Investigation recommends that the Civil Aviation Safety Authority review the maintenance requirements and retirement lives for dry vacuum pumps and introduce a uniform retirement life for dry vacuum pumps regardless of airframe installation.

As a result of the investigation of this safety deficiency, the Bureau simultaneously issues recommendation R19990110 to the Civil Aviation Safety Authority:

"R19990110

The Bureau of Air Safety Investigation recommends that the Civil Aviation Safety Authority adopt US FAA's final ruling on regulation 14 CFR 23.1331".

Initial response
Date issued: 17 May 2000
Response from: Civil Aviation Safety Authority
Action status: Closed - Not Accepted
Response text:

One occurrence noted in your report is a Mooney VH-KUE which suffered a fatal accident after the vacuum system to the instruments failed. This was subject to your draft safety occurrence report 9703221 of 22 May 1998. The CASA response to that report concurred that excessive operating hours since new or overhaul can contribute to vacuum pump failure. The CASA response also noted an extensive range of advisory material issued by CASA to educate the aviation industry on the problem.

To implement a blanket overhaul requirement would probably increase the reliability of operation of these vacuum pumps but would not prevent failures.

The aircraft is, however, intended to be safe even with a vacuum pump failure. This is facilitated by CAO 20.18 Appendix IV which requires that specific instruments have duplicated sources of power. The result is that a full vacuum failure results in part-panel operations. As you note, part-panel operations are not desirable, but under normal expected conditions are considered to provide an acceptable 'get-you-home' capability.

You will note that Discussion Paper DP 9902RP was issued covering General Operating and Flight Rules. That Discussion Paper included proposed alternate instrument power supply requirements at section 91.345 which closely align with the current requirements in CAO 20.18. The review of comments received against that Discussion Paper will be reflected in the Notice of Proposed Rule Making that will be circulated for comment before CASR 91 is issued. ATSB may care to consider providing a specific comment against this requirement in the NPRM which can be considered with other public comments on this important rule.

 
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Last update 01 April 2011