Engine makers are proposing tighter parts manufacturing approval (PMA) for the USA. General Electric and Pratt & Whitney have jointly submitted a letter to the US Federal Aviation Administration (FAA) which calls for drastic revisions of certification regulations controlling PMAs for core engine components, including rotating parts.
The two companies cite safety reasons for their action, though the move is also aimed at the growing activities of non-original equipment manufacturers (non-OEMs) in the lucrative spares market.
"There is a new and greater level of risk at hand with the advent of non-OEM replacement parts in the rotating sections of aircraft engines", the makers claim. "The FAA rules as currently applied, seem to permit approval and use of non-OEM parts under inadequate standards as compared to those satisfied by OEM-type design parts. We submit that the FAA should weigh these factors heavily in reforming its safety regulations", the letter says.
The action, thought to have been spurred by the growth of new, ambitious, non-OEM supply sources like the KLM-Chromalloy venture, is based on the apparent disparity between the rigorous testing regime for GE and P&W, and the standards required of PMA suppliers.
The letter says failure to ensure that both groups are required to meet common high standards could result in "potential risk to aircraft operating integrity, repair station compliance with applicable instructions for continued airworthiness and timely and accurate identification and resolution of incident and event root causes."
GE and P&W say that, historically, most PMA replacement parts for engines have been made from standard alloys and used in relatively low stress environments but "recently, a number of our customers have advised us that non-OEM part manufacturers are preparing to market replacement airfoils for the high pressure [HP] compressor and HP turbine sections of jet engines."
The letter states this "creates a materially higher risk in large commercial jet engines", and adds: "Improperly executed blade designs can potentially lead to significant adverse consequences." The letter urges the FAA to bolster regulations covering PMAs rather than stick to the current schedule which does not anticipate any new rules until May 2004.
Source: Flight International
