Federal Aviation Administration
Central Region, Office of the Regional Counsel
ATTN: Rules Docket No. 99-CE-86-AD
901 Locust - Room 506
Kansas City, Missouri 64106
Gentlemen,
The Aircraft Owners and Pilots Association (AOPA), representing the aviation interests of more then 375,000 pilots and aircraft owners, submits the following comments to Notice of Proposed Rulemaking (NPRM) 99-CE-86-AD. The NPRM proposes a new airworthiness directive (AD) mandating replacement of Roto-Master and RAJAY scavenge pumps installed on Aerostar PA-60-601, PA-60-601P, PA-60-602P, and PA-60-700P airplanes.
AOPA agrees that, in this particular situation, the possibility of in-flight failure of an oil scavenge pump and possible subsequent loss of engine oil warrants airworthiness concern. However, given the lack of reported instances of scavenge pump problems or failures during relatively high time-in-service (TIS) intervals, AOPA fails to see any need for mandatory replacement of scavenge pumps installed on Aerostar airplanes.
In response to this proposed AD, the Aerostar Owners Association (an aircraft type-club representing the vast majority of Aerostar owners/operators) polled its membership to determine the rate of occurrence of scavenge pump problems or failures. Respondent's scavenge pumps averaged approximately 2253 hours TIS. Scavenge pump TIS ranged from 603 to 5963 hours. Of the members polled, none reported ever having service problems with scavenge pumps installed on their airplanes. Several respondents indicated that repeated routine maintenance and inspections revealed no adverse wear or damage to scavenge pumps or their end plates.
Several Aerostar Owners Association members also pointed out that routine maintenance actions may provide indications of damage to the scavenge pump end plate. One commenter suggested that the scavenge pump will leak prior to failure, allowing a damaged pump to be detected prior to failure. Another commenter suggested that routine oil analysis would reveal trace metals that would inevitably result from a scavenge pump rotor "machining its way through the end plate."
A search of the FAA's Service Difficulty Report database revealed no reported instances of oil scavenge pump failure on Aerostar airplanes. Consolidated Fuel Systems, the original equipment manufacturer (OEM) of Roto-Master and RAJAY scavenge pumps, reports in their comments to this docket that only three of the suspect pumps have been returned to their facility for warranty consideration in the past four years. Consolidated Fuel Systems also points out "not a single unit has ever been returned for premature wear or 'failure' of the end plate." Citing lack of service information and the fact that there has to date been no reported instances of an actual failure of a scavenge pump, the OEM opposed mandatory replacement of the pumps stating, "It is our belief that this AD is not warranted."
AOPA has also learned that the FAA has received four reports of wear of scavenge pump end plates - all issued by Aerostar - all resulting from wear discovered during routine maintenance and inspections.
Based on the high TIS of Aerostar oil scavenge pumps and the lack of adverse scavenge pump maintenance history, the lack of FAA service difficulty reports, and lack of OEM data substantiating a service issue with the suspect scavenge pumps, AOPA fails to see any justification for mandatory replacement of Roto-Master/RAJAY scavenge pumps installed on Aerostar airplanes. Given that all four reported instances of worn scavenge pump end plates resulted from routine maintenance and inspections, AOPA believes that annual/100-hour inspections adequately detect unusually worn or damaged scavenge pumps. Thus, AOPA opposes the AD's proposed mandatory replacement of scavenge pumps on Aerostar airplanes. AOPA believes the FAA can best mitigate this concern through the issuance of a Special Airworthiness Information Bulletin (SAIB) highlighting the need to inspect for unusual wear or damage to scavenge pumps and endplates during regularly scheduled maintenance.
Thank you for your time and consideration in this matter. AOPA stands ready to assist the FAA in developing the most appropriate means to mitigate this concern.
Respectfully,
Andrew Werking
Associate Director
Regulatory and Certification Policy