History of the Flight
On 26 May 2010, the pilot of a Cessna 177A Cardinal, registration G-BTSZ, planned a local area flight from Cranfield with two passengers. Before departure, the pilot visually inspected the fuel tank contents by looking through the filler necks and estimated approximately 22 gallons, sufficient for two hours of flight. The engine fuel strainer (gascolator) drain operating handle was located on the upper right engine cowling and when opened discharged fuel through a pipe extending through the lower left cowling. With the assistance of a passenger, the pilot performed the drain check and observed no abnormalities.
After engine start, the aircraft was held on the ground for 15 minutes due to other circuit movements. Approximately 15 minutes after takeoff, the engine began to misfire. The pilot applied carburettor heat but it had no effect. Checking the fuel quantity gauges, he found both indicating empty. He established a glide, informed ATC of the problem, and intended to land at a disused airfield in the vicinity. During the approach, he realised the aircraft would not reach the remaining runway and instead landed on an area of ploughed ground north of the site. During the ground roll, the nose landing gear collapsed. The pilot and two passengers sustained minor injuries but were able to leave the aircraft unassisted.
Investigation
The pilot stated that his fuel estimation was by visual assessment of depth through the filler necks, which lacked tabs for accurate measurement. He also reported that approximately 18 months earlier he had experienced difficulty with the fuel strainer drain, but it had been rectified. He placed covers over the fuel filler caps when parked to prevent water ingress. The maintenance organisation later examined the aircraft and confirmed it was fitted with an early standard of fuel filler caps, more prone to water ingress than the raised umbrella type.
Inspection revealed the aircraft's fuel tanks were empty and evidence of an in-flight fuel leak from the engine fuel strainer drain. Tests on the drain mechanism showed that after operation, the drain valve could stick partially open, producing a leak rate of 18 to 24 gallons per hour. Disassembly found the filter drain mechanism contaminated by a large deposit of waxy material, similar to that produced when fuel is contaminated with water. After cleaning and reassembly, the drain operated normally. The deposits likely prevented the drain from closing fully, resulting in unobserved fuel loss.
On 30 July 2010, the Federal Aviation Administration published Special Airworthiness Information Bulletin SAIB CE-10-40R1 advising Cessna 100, 200, and 300 series owners of water contamination hazards and methods to minimise water ingress, including use of new raised umbrella fuel filler caps.