Delta Air Lines saves $20 million a year by using PMA parts, according to Andy Shields, VP of engineering for the Wencor Group. That might be one reason Delta had the lowest maintenance cost per flight hour among U.S. network carriers in 2016. $20 million represents nearly 1% of Delta’s MRO spending and about double that portion of its MRO material costs. Shields thinks other airlines ought to consider PMAs too, although he admits there are hurdles to effective PMA use.
The first advantage of PMAs is cost. For a simple PMA like a lavatory filter on an Airbus A330, Wencor charges $9, versus $22.50 for an OEM part. For the much more complex carrier shaft on an internal drive generator, it is $16,000 for the PMA and $38,000 for the OEM version.
Next is equal and often better reliability from PMAs. “We understand the shortcomings of OEM parts, because airlines tell us what breaks,” Shields notes. “Also we have new materials and new methods, especially compared with a legacy aircraft like the A320, which entered service in 1982.” Shields says Delta uses PMA parts for the internal drive generators on its Boeing 737s, and gets 1.5 to 2 times the mean time between removals of the industry as a whole.
Finally, there is availability, especially for older aircraft. When the thrust reverser door-block links on Delta’s MD90s started breaking, the OEM had few replacements available, so the carrier sought a PMA solution. The PMA yielded no further failures on the component.
Shields admits exploiting PMAs can pose challenges. Long-term contracts and power-by-hour programs can be attractive and exclude PMAs. “But once you have signed those deals, you are locked in, there will be no improvement,” Shields says.
OEMs might use intellectual property arguments to deny manuals to PMA users. FAA has forbidden outright denial, but OEMs can still price manuals very high.
Used parts can be attractive alternatives to OEM new parts, but Shields says this alternative may not cover all needed parts on a major component.
OEMs may engage in predatory pricing. For example, if an airline use one or a few PMAs on a component, the OEM can jack up prices on the remaining parts. That is why Wencor takes a systematic approach to PMAs and tries to produce all the frequently needed parts on a given component.
Safe and effective PMA use requires staffing up to review PMAs and set PMA policy. Airline staff must update manuals for PMA use, because OEMs will not.
Finally, although almost all foreign regulators approve FAA-accepted PMAs, local inspectors may be uncomfortable with them. And some leasing firms do not accept PMAs, requiring different part stocks for leased versus owned aircraft.
Major carriers such as Delta have the bargaining strength to deal with OEM counter-moves and the scale to justify staffing up for PMA use. Smaller airlines may have neither strength nor scale.
Still, for the right airline PMAs can be very attractive. One Star Alliance member uses nearly 1,300 PMAs for its A320s, A330s, 767s and ERJ-170s and -190s, Shields says. Wencor alone has about 4,600 active PMAs covering all mechanical systems, including engines, fuel systems, landing gear, pneumatics and cabin interiors. “All the parts that wear out,” Shields jokes. “We don’t make structural parts because they don’t wear out.”