Misassembled Fuel System Componant Could Cause In-Flight Shutdown

The FAA has issued an emergency AD (2011-05-51) for Turbomeca Arriel 1E2, 1S, and 1S1 turboshaft engines after three reports of incorrectly assembled low-pressure fuel system ejectors, with one of them resulting in an uncommanded engine in-flight shutdown.

The European Aviation Safety Agency (EASA), which is the Technical Agent for the Member States of the European Community, issued emergency AD No. 2011-0023-E on February 9, 2011 (corrected on February 10, 2011). That AD states:

In October 2009, Turbomeca issued SB [Service Bulletin] No. 292 73 0826, Version A that instructed operators to check the effectiveness of the bonding of the ejector jet installed on the low-pressure fuel system between the tank and the high-pressure fuel pump.

So far, Turbomeca have been informed of three discrepancies with the reassembly of the ejector following a maintenance procedure performed during accomplishment of Turbomeca SB No. 292 73 0826, Version A.

In all three cases, the discrepancies led to a “one-off” abnormal evolution of gas generator (NG) rating during engine starting. In one of these cases, this resulted in an uncommanded in-flight shutdown, during a cruising phase at 8,000 feet. This condition, if not corrected, could result in uncommanded engine in-flight shutdown of one or both engines in a two-engine helicopter and an emergency autorotation landing or accident.

The FAA reviewed Turbomeca Mandatory Service Bulletin (MSB) No. A292 73 0834, Version B, dated February 8, 2011, and SB No. 292 73 0826, Version B, dated February 4, 2011. This service information describes procedures for inspecting for proper ejector installation. The agency says it is issuing this AD because it evaluated all the relevant information and determined the unsafe condition described previously is likely to exist or develop in other products of the same type design.

This AD requires inspecting the fuel ejector in the body of the fuel ejector assembly for proper installation by checking that the circlip is properly seated in its groove using Turbomeca MSB No. A292 73 0834, Version B, dated February 8, 2011.

FMI: http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/0/8DC777BBB620165D862578390056677B?OpenDocument