Alert Lycoming IO-360 Engine: Reports of engine shutdowns during throttle reduction to idle

[Neal]

Thanks for the link @Tsquared. I know you had an engine failure on base/final with undetermined cause. @Cactus Charlie this may be related to your engine failure after touchdown if I recall?

https://www.eaa.org/eaa/news-and-pu...orthiness-concern-sheet-lycoming-io360-engine

Fuel-injected Lycoming rollbacks prompt FAA concern

Fuel-injected four-cylinder Lycoming IO-360 engines with AVStar fuel servos have unexpectedly shut down at idle power.

www.aopa.org

https://download.aopa.org/advocacy/2025/2025-12-16_ACS_IO-360-engine-rollbacks.pdf

The FAA is currently investigating reports of engine shutdowns during throttle reduction to idle, often referred to as rollbacks, on aircraft equipped with Lycoming IO-360 engines. An airworthiness concern sheet (ACS) has been issued to inform operators and maintenance personnel of this concern and to collect additional operational data.

The ACS was published after multiple reports were received indicatinguncommanded engine shutdownson aircraft with IO-360 engines using AVStar manufactured vertical and horizontal mounted fuel servos when the throttle was brought back toward idle. These events have been reported on a range of aircraft including Cessna 172S, Cessna 172R, Piper Archer III, Piper Pilot 100i, and Piper Seminole models equipped with IO-360 engines.

The FAA is asking operators, maintainers, and owners of aircraft with IO-360 engines to provide information on any observed rollback events, regardless of fuel servo manufacturer or installation orientation. The requested information can be found here.

The FAA uses the airworthiness concern sheet to communicate and coordinate potential airworthiness concerns to the industry and to gather information about specific issues before they reach the level of required airworthiness actions. EAA, along with other associations and type clubs, disseminates the voluntary ACS as a means to help the FAA gather information and to better understand any mitigating circumstances surrounding each particular issue.

 

[Cactus Charlie]

I reviewed the data for my stoppage on rollout. It showed the engine had been running very rich during the approach. I suspected contamination of the servo metering ball valve and dismantled the servo for inspection.

I found no contamination but blew out all exposed passages. The problem has not been seen since then.

 

[Neal]

Original post updated with more information and a PDF resource.

 

[Cactus Charlie]

I submitted my report of my landing rollout stoppage to FAA in response to the ACS. It has far more detail than the final NTSB report of the engine stoppage of another FX-3 that resulted in substantial damage.

I still suspect that my event was caused by contamination introduced during manufacture of the servo.