The pilot of an Aero Commander departed on a flight earlier this with insufficient fuel that resulted fuel exhaustion and a forced landing, according to an ATSB report released this week.
VH-MEH was on a multi-sector cargo run on the Bankstown-Parkes-Bankstown route in March, when both engines stopped on the final return leg only four minutes after leaving Bathurst. The pilot was able to turn back towards flatter ground and landing the aircraft in a paddock.
The ATSB determined that both engines stopped because the fuel in the tanks was exhausted.
At the end of the first sector at Orange earlier that day, the pilot found the fuel cap was dislodged and hanging from the chain. The pilot replaced the cap, but at the end of the second sector to Parkes, found the cap again dislodged. An engineer rectified the problem before the pilot started the return leg, which would include stops at Orange again and at Bathurst.
Before departing Parkes, the pilot noted a discrepancy between the fuel quantity gauges and the expected fuel remaining, but did not refuel the aircraft, believing there was enough on board to get back to Bankstown.
“For the two sectors from Bankstown to Parkes, the fuel cap had been incorrectly installed with the retention chain lodged in the fuel tank’s anti-siphon valve, resulting in the cap dislodging in flight, and fuel being siphoned overboard,” ATSB Director Transport Safety Stuart Macleod explained.
“However, the pilot identified an unexplained discrepancy between expected fuel remaining and gauge quantity indication, but did not refuel to a known quantity, or amend the flight log.
“This meant the aircraft left Parkes without enough fuel to complete the remaining sectors on its return trip back to Bankstown.”
ATSB investigators believe that the pilot over-estimated the fuel on-board at the beginning of the flight by 70 litres, and that the flight consumed around 305 litres of fuel, leaving 185-251 litres of fuel not accounted for.
Calculations showed that the aircraft could have departed Bathurst with as little as 28 litres on board.
“Pre-flight fuel quantity checks should use at least two different verification methods to determine the amount of fuel on board,” Macleod said.
“When using computed fuel on board and comparing against gauge readings, it is important that calculations are accurate. If any discrepancy is detected between the two methods, another method such as filling to a known quantity is required.”
The report notes that it is impossible to visually verify the fuel tank quantities on a Twin Commander, which led to the company using fuel logs as a method of keep track of consumption.
The full report is on the ATSB website.