AD NUMBER: 2007-24-10
MANUFACTURER: Turbomeca
SUBJECT: Airworthiness Directive 2007-24-10
SUMMARY: We are adopting a new airworthiness directive (AD) for the products listed above. This AD results from mandatory continuing airworthiness information (MCAI) provided by the European Aviation Safety Agency (EASA) to identify and correct an unsafe condition on Turbomeca Arriel 2S1 and 2S2 turboshaft engines.

The MCAI states the following: During assembly of a new HP/LP fuel pump, the drain screw on the fuel filter unit failed when it was tightened to the torque value specified in the assembly schedule (12 Nm).

Investigation of the screw showed that it was fully conformed to its specification, in terms of both dimensions and material. The mechanical calculations show, however, that a torque value of 12 Nm is too high for this screw, exceeding the elastic limit of the material.

Failure of the affected screw could cause a fuel leak, resulting in an engine flame-out or engine fire.

We are issuing this AD to prevent a fuel leak as a result of a ruptured fuel filter drain screw that could lead to engine flame-out or an engine fire.

FMI: www.faa.gov/regulations_policies/airworthiness_directives/