It is enlightening to see that there is some movement to increase the use of parts manufacturer approval (PMA) spares in aviation ("Non-OEM engine parts gain sales", Flight International, 13-19 May). Original equipment manufacturers (OEMs) have been late in recognising that their parts are too expensive for airlines.
I worked for a PMA company that made engine combustion chambers for the Pratt & Whitney JT8D. A customer, contemplating a purchase of 549 chambers, was concerned about quality and had a set of combustion chambers checked against the OEM's chambers by its metallurgical laboratory. The laboratory reported them as good as, and in most of the tests, better than, the OEM's parts.
Companies wishing to manufacture component parts are required to comply with strict manufacturing processes and quality procedures before gaining US Federal Aviation Administration approval.
Marc Ventre, president of Snecma Services, asks "how somebody can copy a design and claim to have covered all the engineering background". Has he not heard of reverse engineering? The OEMs have done all the work - the PMA company is working to the OEM's component manufacturing drawings and specification, with low overheads, low production costs - and low prices.
Considering the costs of OEM replacement parts, is it any wonder that airlines and operators are looking to reduce the cost of fleet maintenance. PMA parts can reduce the maintenance costs of an airline by 50% or more, without sacrificing high standards of quality and longevity.
Anthony Mullard Colnbrook, UK
Source: Flight International
