OEM v PMA a case study

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Paul Hurley K0640515

Kingston University - Faculty of Engineering

BEng (Hons) Aircraft Engineering Top - up

AE 3111 - Aircraft Maintenance and Logistics

Aircraft OEM vs. PMA Parts makers (A Case Study)

P J Hurley 21st May 2007

Lecturer:  Dr A A Ghobbar

INTRODUCTION

The Federal Aviation Administration (FAA) and European Aviation Safety Agency (EASA), which largely governs the ‘British’ Civil Aviation Authority, set the standard regulations for the production of aircraft replacement parts for civilian aviation. Parts Manufacturer Approval (PMA) are becoming more widely accessible and popular within the aircraft industry.  Having initially been developed post WW2 to feed spare parts to the operators of surplus ex-military aircraft, PMA manufacturers were largely unregulated until the mid 1990s when the FAA sat up and took notice of what was occurring. Now manufacturers of PMA parts operate under strict FAA (and to a growing extent EASA) guidelines - FAR 21.303. PMA parts are advantageous to the aircraft industry for the following reasons:

  • Often the sole source of parts for out of production aircraft.
  • Cost less than OEM parts
  • Outstanding safety record

In this essay the author will, by way of reinforcing the viability of PMA parts, give a brief case study of Replacement Aircraft Parts Company (RAPCO) who operate entirely in the civilian sector, and will discuss the advantages that their replacement brake parts have over the rival OEM parts.  The author works within the confines of military aviation and as such the comparison of PMA versus OEM parts is not valid within his particular environment.  However there is a degree of flexibility within military aviation that allows the manufacture of aircraft and airborne equipment by Army, Navy or Air Force personnel to be carried out at unit level, especially on operations, this is the nearest thing to PMA in the Armed Forces.  The author will therefore discuss the policy, authority and manufacturing requirements for the local production of aircraft parts for military use.

RAPCO

A United States company, and a large stakeholder in the PMA parts industry, RAPCO is a large scale producer of replacement aircraft brake parts.  Their business plan has seen them not only match OEM standards, but exceed them by introducing advancements to the replacement parts that they provide.  An example of the innovation shown was the introduction of asbestos-free brake linings that included a wear indicator, characteristics lacking in the OEM component.  Of course the RAPCO brake linings were also markedly cheaper than the OEM parts, and as such the sales figures were impressive.

In an expansion to their production range, RAPCO began manufacturing PMA brake discs, once again adding improvements to the OEM parts.  In detail, they introduced a single piece milled disc to replace a two-piece assembly, offering greater corrosion resistance and better heat dissipation.  Such was the success that they currently manufacture replacement brake discs for 83 aircraft types.  A typical Learjet OEM brake disc has an expected life of 125 cycles, whereas the cheaper RAPCO alternative can be expected to last for 200 cycles.  RAPCO also ensured that there would be no delay in the availability and delivery of brake components by procuring their own dynometer testing facility, ensuring there would be no delays in gaining airworthiness approval.

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RAPCO’s success story has been described in brief purely to add value to the argument that the use of approved components, other than OEM, is not necessarily detrimental to the airworthiness of an aircraft.  In fact the opposite is often true and, as seen, an approved manufactured component either PMA or, as the author will now discuss, locally manufactured by highly trained military tradesmen, has the potential to be better than the original.

Manufacture Of Parts For Military Aircraft

The manufacture of replacement parts for military aircraft is permitted within certain prescribed guidelines.  The author ...

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