Lear Romec Fuel Pumps: Pressure to perform

AD2003-14-03 marks yet another effort by the Crane Manufacturing Corp. and the FAA to eliminate the persistent fuel leakage problem associated with the Lear Romec engine-driven fuel pump. At first glance, this most recent AD appears to be a simple...

Lear Romec Fuel PumpsAD2003-14-03 marks yet another effort by the Crane Manufacturing Corp. and the FAA to eliminate the persistent fuel leakage problem associated with the Lear Romec engine-driven fuel pump.

At first glance, this most recent AD appears to be a simple rehash of the superceded AD98-18-12. However, a more focused reading reveals some important details in this document. This AD is far from benign and could have some longstanding impact on your pocketbook unless some preventative measures are taken. Aug. 14, 2003 is the stated affectivity date of this newest Airworthiness Directive. Owners and operators have 10 hours of time in service or 30 days from this date to begin complying with the AD.

A Brief History
Mechanics have been faithfully performing repetitive torque check inspections on the four cover screws (see Figure 1 on page 14) on fuel pumps since 1976, when Lycoming first released SB406. Lycoming Service Bulletins have repeatedly addressed the importance of inspecting Titan and Lear Romec model fuel pumps for potential leaks at the parting surfaces of the relief valve housing. Typically such leaks were symptomatic of gasket material that had taken a set or shrunk with time. This ongoing inspecting and retorquing the four cover screws at scheduled intervals was an attempt to eliminate fuel seepage.

Over the past 25 years, a number of bulletins have been spawned in the wake of SB406. Many of these bulletins served to clarify fuel pump inspection criteria. AD98-18-12 came on the heels of three engine fires and six other leakage events on certain Lycoming recip engines. Yet in spite of all this additional attention, there still remains the potential for gasket compression set or gasket creep which both result in loss of clamping force. When clamping force is reduced, fuel may be allowed to escape from the parting surfaces; occasionally with catastrophic results (see Lear Romec Fuel Pump article in July 2000 AMT).

One successful measure taken by Crane in November of 1999 was to incorporate a new relief valve design that relied on packings held captive in O-ring grooves machined directly into the housing itself (see Figure 2). Modification kits soon became available. Replacing the old valve housing with this newer design served to enhance the pump's resistance to fuel leakage. By installing the new style housings, owners could then ignore the mandates for reoccurring inspections. Unfortunately, the additional costs associated with installing these modification kits sent overhaul prices through the roof. Modification costs were added to the cost of a normal overhaul to return the pump to an airworthy condition. An aircraft owner could expect to see list prices in the range of $1,500 to $2,000 to return his Lear Romec pump to service as newly overhauled and modified.

Ramifications of AD 2003-14-03
So what differentiates AD2003-14-03 from its predecessor, AD98-18-12? Also, what are some of the considerations that an owner or operator should give when attempting to comply with this directive?

The AD sets itself apart from previous documents in the following areas:
1.) It further defines and establishes a terminating action.
2.) It requires an ongoing visual inspection for the life of the pump (or until the terminating action has been satisfied).

Figure 1: The four cover screws must be retorqued at specific intervals in accordance with Crane’s bulletins 101SB012, 101SB017, 101SB018, and 101SB020 and Textron Lycoming bulletin SB529B.

Figure 2: AD 2003-14-03 (7/14/03) and Crane’s bulletin RG9080-73-001 (7/28/03) address the possibility of replacing the
relief valve housing as an alternate means of compliance and as a terminating action to the AD.
Relief valves for the RG17980 style of pump sell for $315. Valve housings for the RG9080 sell for $285.

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