FAA Releases Airworthiness Concern Sheet for Fuel Additives in H80/M601 Engines

The FAA has released an Airworthiness Concern Sheet (ACS) for certain GE Aviation Czech (GEAC), formerly Walter Engines, models including the H80 and M601D-11. This ACS is a request for information to operators of aircraft with these engines installed, specifically on use of lubricity improver additives (LIA) in fuel. 

Earlier this year, the European Union Aviation Safety Agency (EASA) published EASA AD 2025-0022. This AD identified the above referenced engine models Fuel Control Units (FCU) as having the potential to have delayed or no response to power level inputs due to fuel deposits in the FCU internal valves which increases friction on mating surfaces. This can result in Loss of Power Control (LOPC) events and unscheduled removal of the FCU for maintenance. The EASA AD mandates (in its jurisdiction) compliance with GEAC Service Bulletin SB-000469 Revision 1, dated March 2024, requiring the application of LIA to the aircraft fuel tanks every 100 flight hours to avoid potential LOPC and improve FCU reliability. 

While FAA currently has no such requirement for use of LIA, it is seeking information from operators of these engines, including: 

• Information on the US fleet of affected engines/aircraft, such as number of engines, current operators and N-registered aircraft. 
• Availability of LIA to include types and concentrations. 
• Whether sufficient information is available at fueling stations to accurately dose LIA for on-wing fueling operations. 
• Whether the GEAC SB is being followed, and if so, whether there has been any adverse effects or problems from following the SB, such as corrosion in affected FCUs. 
• If the GEAC SB has not been followed, have there been any issues regarding FCUs, such as LOPC. 

If you would like to provide information to FAA regarding this issue, see the ACS for full details and contact information. 

An ACS is neither regulatory nor mandatory. It requests feedback from the aviation industry on a voluntary basis and is intended to increase communications between the FAA and the aviation industry so that input from industry can be used to inform FAA’s analysis of the safety issue. For this ACS, FAA has not yet decided if a corrective action will be necessary or what it might be, but it could involve an Airworthiness Directive (AD) or a Special Airworthiness Information Bulletin (SAIB). The FAA’s final determination will depend in part on the information received in response to this ACS.