Page 13 - June 2015 Volume 19 Number 6

Need Fuel
Lessons from this: Don’t assume that mathematics, and even your knowledge of the fuel system, will precisely predict results in actual flight. Concepts of unusable fuel and regulatory fuel reserves are designed to give us a little “wiggle room” if actual conditions differ from what we expect. If you’re operating near the maximum range of the aircraft (“maximum” may be revised if something unusual happens en route), be spring-loaded to divert to a nearby airport if you cannot positively verify the amount of fuel remaining through multiple, independent means.
Airplane limitations. Airframe and systems limitations are almost always the result of known and documented issues that stem from the aircraft’s design–often accentuated by examples in the NTSB record.
The Baron pilot apparently adhered to the fuel system limitation, at the last minute, because both selectors were found on their respective main tank. Perhaps he switched before the engine quit and exhausted the remaining fuel in that tank. It’s possible the engine failed while burning from the auxiliary tank, and he switched to the main tank as part of a restart attempt.
In the Conquest, the right engine did not completely empty its tank, but the fuel level was apparently pretty low. It may be that a common fuel system limitation was a factor– to avoid slips when the fuel level is below some level. More correctly, this condition is problematic when making an uncoordinated turn, when a low fuel level can “slosh” away from the fuel lines.
The Cessna 402B’s case should have been obvious before takeoff. An inoperative fuel transfer pump is a “no-go” item in these airplanes. If the pilot performed the pre- takeoff check, and assuming the pump failure did not occur at some time during the accident flight, he should have aborted the flight. Good
found with the engine that could have resulted in its failure. The right fuel tank was breeched; however, fuel calculations, confirmed by some fuel found in the right fuel tank as well as fuel found in the engine fuel filter housing, indicated that fuel exhaustion did not occur. It is unknown if or how much pilot fatigue might have influenced the outcome.
NTSB probable cause: The pilot’s failure to maintain minimum control airspeed after a loss of right engine power, which resulted in an uncontrollable roll into an inadvertent stall/spin. Contributing to the accident was the failure of the airplane’s right engine for reasons that could not be determined because no preexisting mechanical anomalies were found, and the pilot’s subsequent turn toward that inoperative engine while maintaining altitude.
From the NTSB:
The Cessna 402B was approaching the destination airport with about seven gallons of fuel remaining in each of the 50-gallon main fuel tanks. While on short final, as the pilot fully extended the flaps, the airplane experienced a total loss of power on the right engine. The airplane touched down hard on a grassy area about 650 feet before the runway, bounced onto the runway, and came to rest. The pilot subsequently started both engines and taxied to the ramp area uneventfully.
A post-accident examination of the airplane revealed that the right main fuel tank’s fuel transfer pump was inoperative. The fuel
transfer pump was designed to operate continuously when the battery switch is on. The purpose of the pump is to transfer fuel from the nose section of the tank to the fuel pick-up area near the center of the tank, which permits steep descents with low fuel quantity. It could not be determined when the fuel transfer pump failed; however, confirming pump operation is a required preflight inspection item for each main fuel tank.
NTSB probable cause: The failure of the right main fuel tank transfer pump, which resulted in a total loss of right engine power during approach due to fuel starvation, and a subsequent hard landing. Contributing to the incident was the pilot’s operation of the airplane with a low fuel quantity.
Let’s look at some commonalities in these three scenarios, and explore some strategies to avoid finding yourself in similar circumstances.
Common Elements
Low fuel level. It sounds redundant to say that fuel exhaus- tion was due in part because the fuel level was low, but work with me: in these three events, the pilot was knowingly operating the aircraft to the extreme of its fuel endurance. In the case of the Conquest and 402B, it appears the pilot intended to stretch the airplane’s range to its limits. In the Baron, some unusual situation led to detection of a fuel imbalance, and the pilot flew the airplane into a limited-fuel condition.
JUNE 2015
TWIN & TURBINE • 11