Cause for loss of engine power a mystery

The passenger reported that, about 15 minutes after takeoff on the cross-country flight, the Cessna 175’s engine began “stalling in and out.”

Although the pilot attempted to troubleshoot the issue, he could not remedy it, and selected a dirt road near Pine Bluff, Arkansas, as a forced landing site.

The passenger said the airplane was too fast and too high to land, and the pilot circled the airplane for a second approach.

About 150′ above the ground, the engine experienced a total loss of power. The airplane touched down in an area of tree stumps and immediately nosed over. The pilot died in the crash.

Toxicology testing of the pilot revealed the presence of diphenhydramine, however the level detected was too low to quantify and was unlikely to be impairing.

No shoulder harnesses were installed, and their installation was not required.

Advisory Circular 91-65, in part, stated, “The NTSB concluded that shoulder harness use is the most effective way of reducing fatalities and serious injuries in general aviation accidents.”

Although the spark plugs displayed significant wear, a test run of the engine revealed no anomalies that would have precluded normal operation.

A carburetor icing probability chart showed the airplane was operating in conditions conducive to serious icing at glide power. However, the plane should not have been susceptible to carburetor icing at the cruise power setting at which it was operating. The investigation could not determine a reason for the loss of engine power.

Probable cause: A loss of engine power during cruise flight for reasons that could not be determined because a test run of the engine did not reveal any mechanical malfunctions or anomalies that would have precluded normal operation. Contributing to the accident were the tree stumps at the forced landing site.

NTSB Identification: CEN16FA210

This June 2016 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.