N3964L

On January 8, 2022, about 1530 eastern standard time, a Cessna 172G airplane, N3964L, was substantially damaged when it was involved in an accident near Youngstown, Ohio. The private pilot and two passengers sustained no injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 test flight.

The airplane was modified with a Federal Aviation Administration (FAA)-approved supplemental type certificate to utilize automotive fuel (commonly called “MOGAS”), which the pilot used to fuel the airplane before the accident flight. Before the flight began, the pilot reported there was 7 gallons in the right fuel tank and less than 2 gallons in the left fuel tank, as he checked the fuel levels with a sight gauge. The pilot added 3.8 gallons of fuel to the left fuel tank. The right fuel gauge indicated “one quarter of a tank” and the left fuel gauge indicated “slightly less than half a tank.”

The pilot reported the purpose of the flight was to verify the proper operation of a newly installed automatic dependent surveillance-broadcast system in the airplane. After the confirmation of accuracy, the pilot entered the downwind leg of the traffic pattern. At the midfield point, the pilot added 10° flaps and applied full carburetor heat. The engine then “stumbled and quit.” The pilot attempted to restart the engine to no avail. The pilot had the fuel tank selector in the BOTH position, and he reported he did not change its position at any time.

The pilot increased the flaps to 40° and he executed a teardrop-style left turn to the runway. He reported he was below the tree line but was still too high to make a touchdown. The airplane “floated long” and landed on airport property beyond the runway into trees, at stall speed. The airplane came to rest with the left wing pointing down toward the ground and the right wing toward the sky. The three occupants were able to egress from the airplane without further incident.

The airplane sustained substantial damage to the left wing and fuselage. Postaccident examination of the airplane found both fuel tanks intact, with no signs of a fuel leak on the airframe. About a quarter of a gallon of fuel was drained from the right fuel tank and about 4 gallons of fuel were drained from the left fuel tank. The fuel tank selector was found in the BOTH position. Airframe to engine control continuity was confirmed. An examination of the engine revealed no mechanical anomalies.

A review of the meteorological conditions near the time of the accident, showed that the formation of carburetor icing was not likely for the usage of aviation gasoline. The FAA has published Advisory Circular (AC) 91-33A Use of Alternate Grades of Aviation Gasoline for Grade 80/87 and Use of Automotive Gasoline. This document discusses carburetor icing and states:

FAA Technical Center testing indicates that carburetor icing will occur in less time and at higher ambient temperatures with automotive gasoline than with aviation gasoline.

Therefore, pilots using automotive gasoline should be familiar with the induction system icing prevention procedures of the FAA AC 20-113 and be prepared to use these procedures at higher ambient temperatures and lower humidities than when using aviation gasolines.