Page 12 - June 2015 Volume 19 Number 6

Twin Proficiency: by Thomas P. Turner
They Both
In most twin-engine airplanes, fuel management is simple. Each engine’s fuel selector often has three positions: ON, OFF and CROSSFEED. CROSSFEED is an emergency position, for use during extended single-engine operation to maximize range and balance fuel when one engine is shut down. Consequently, the fuel selector typically remains in the ON position.
Some airplanes have auxiliary fuel tanks, resulting in a fourth valve position: AUX. In every airplane I’ve encountered, independently- selectable auxiliary fuel tanks are POH-limited to cruise flight. That adds only a little complexity to the task of fuel management: take off with the selector in ON or MAIN, switch to AUX at some point during cruise, and return to ON before descent and landing.
Regardless of your airplane’s fuel system specifics, one thing seems obvious: both engines need fuel in order to run. Since you generally start one engine right after the other, the engines usually burn fuel at approximately the same rate, and we usually load the same amount of fuel into each wing, for symmetry. One engine starving for fuel is way down on our list of things to worry about.
Yet, it happens. What are some of the unusual scenarios that result in exhausting one engine’s fuel supply, while fuel is available to the other? What strategies are suggested by studying these events?
From the NTSB:
The pilot of a Beechcraft Baron E55 noted an imbalance between the left and right main fuel tanks during cruise. He attempted to correct the imbalance by placing the left fuel selector in the crossfeed position, so both engines would receive fuel from
10 • TWIN & TURBINE
therightmaintank.About15minutes later, both engines lost power. When the pilot reset the left and right fuel selectors to the left main and the right auxiliary fuel tanks, respectively, the left engine regained power and the right engine began “surging.”
The pilot decided not to shut down the right engine and diverted to the nearest suitable airport. During final approach, the right engine lost power completely, and the airspeed decayed until it approached the airplane’s minimum-control airspeed. When the airplane drifted right of the runway centerline, the pilot reduced power on the left engine in an attempt to maintain control. The airplane impacted an open field near the runway and a post-impact fire ensued.
Post-accident examination revealed no airframe or engine anomalies consistent with a pre- impact mechanical failure or malfunction. Both fuel selectors were positioned to their respective main fuel tanks. The pilot stated that the airplane was fully fueled before departure. He stated he had not used any of the fuel in the auxiliary tanks before the loss of engine power. The pilot’s operating handbook notes that the crossfeed system is not to be used to transfer fuel from one tank to another or to balance fuel during flight. The simultaneous loss of engine power while both engines were receiving fuel from one fuel tank, the restoration of power on the left engine after switching fuel tanks, operation at or near the endurance limit for the right main
tank, and the lack of anomalies identified during the engine exams are consistent with exhaustion of fuel in the right main tank.
NTSB probable cause: The pilot’s failure to maintain airspeed and subsequent loss of airplane control during a single-engine landing approach. Contributing to the accident was the pilot’s improper fuel management during cruise flight, resulting in an initial loss of power in both engines and the subsequent single-engine approach after power was restored on only one engine.
From the NTSB:
Toward the end of a 6 hour, 20 minute flight, during a night visual approach, the pilot of a Cessna Conquest flew the airplane to a left traffic pattern downwind leg, lowering the landing gear and setting the flaps to 30 degrees. He turned to a left base leg and, after doing so, was heard on the CTAF stating that he had an “engine out.”
The airplane then passed through the final leg course, the pilot called “base to final,” and the airplane commenced a right turn while maintaining altitude. The angle of bank was then observed to increase until the wings became vertical, then inverted, and the airplane rolled into a near-vertical descent, hitting the ground upright in a right spin.
Subsequent examination of the airplane and engines revealed that the right engine was not powered at impact, and the propeller from that engine was not in feather. No mechanical anomalies could be
JUNE 2015