What happened
On a flight from Dryden to Geraldton, Ontario, a Hicks & Lawrence Limited Aero Commander 500B, registration C-GETK, experienced a dual engine power loss while cruising at 5,500 feet. The incident began approximately 40 minutes into the flight when the crew noticed abnormal fuel flow in the right engine. As the crew attempted to troubleshoot the issue and diverted toward Armstrong, the left engine also experienced a significant drop in fuel flow and RPM.
Unable to maintain level flight, the crew performed a forced landing in a wooded, marshy area roughly 20 nautical miles southwest of Armstrong. The aircraft sustained substantial damage during the belly landing and subsequent impact with a tree. The captain sustained serious injuries, while the co-pilot and passenger suffered minor injuries.
The investigation
The investigation focused on the fuel systems of the two Lycoming IO-540-B1A5 engines. Investigators discovered a blockage in the fuel supply to both engines. Specifically, the right engine suffered a complete blockage, while the left engine had a partial blockage preventing fuel from reaching the forward cylinder nozzles.
Upon examining the right engine's fuel distributor valve, investigators found ice adhering to the internal main metering well and the servo bleed screen. The investigation also noted that the aircraft had been stored in a heated hangar, which increased the fuel's capacity to hold water in suspension. While pre-flight sump drains showed no visible water, the investigation determined that water was present in the fuel but remained invisible while held in solution.
Findings
- Water in the fuel system precipitated out of solution and froze within the fuel distributor valves, obstructing the flow of fuel to the engine nozzles.
- The extreme cold, with temperatures aloft reaching -33°C, caused super-cooled water droplets to freeze upon contact with the valve, which is directly exposed to the engine cowling's cooling airflow.
- The aircraft was operating without a fuel additive icing inhibitor, which would have prevented the ice formation.
- The operator lacked specific procedures for the use of fuel additives during winter operations.
Safety action
Hicks & Lawrence Limited has since updated its operations manual to mandate the use of fuel additive icing inhibitors whenever ambient temperatures at the surface or altitude fall below 0°C. The company also planned to implement mandatory training regarding these additives.