A time-honored pre-flight inspection ritual is sampling an aircraft’s fuel tanks. The idea, of course, is to drain a quantity from each sump, which usually mounted at a tank’s lowest point, into a clear container, then examine the fuel for contamination and quality: Is it the same stuff that’s supposed to be in the tanks? Are water or other contaminants present? Is it even fuel?
In my flying career, at least, it’s rare to find a problem with a fuel sample. But I’ve been quite shocked on a few occasions to find nothing but some very nasty-looking water in a tank or two, which demanded further investigation. Yet, I’ve seen pilots walk up to an airplane for the first flight of the day, kick the tires, light the fires and launch without sumping. Truth be told, I’ve probably done it a couple of times, too. But it’s a bad idea. Here’s why, and what can happen when we fail to sump fuel tanks and ensure we have clean, correct fuel.
Background
On March 16, 2011, at 1029 Pacific time, a Beech Super King Air 200 impacted terrain following a loss of control during takeoff from the Long Beach (Calif.) Airport. The commercial pilot and four passengers were fatally injured; a fifth passenger was seriously injured. The airplane was substantially damaged. An IFR flight plan had been filed for a cross-country flight to Salt Lake City, Utah, and the crash occurred on initial departure. Visual conditions prevailed.
The aircraft owner’s aviation manager stated he did not observe the pilot perform the airplane’s preflight inspection and no witnesses observed such an activity on the morning of the accident. At 1027, ATC cleared the pilot for takeoff. Several witnesses reported the initial ground roll appeared normal. Shortly after the airplane rotated and started to climb, it began to yaw left and level off. One witness said “the airplane sounded like it was in trouble.” Several witnesses reported the airplane banked left, its wings wobbled and its fuselage fishtailed. The bank angle increased to 45 to 90 degrees, and the airplane’s nose dropped down to near-vertical. One witness said the bank angle and pitch “began to flatten out just before crashing down to the ground.” A fire erupted, which consumed the airplane.
Investigation
The 43-year-old pilot had approximately 1113 hours of multiengine time, of which 463 hours were in the make and model of the accident airplane. On October 19, 2010, he successfully passed a Part 135 check ride in a King Air 90. He was hired to fly the accident airplane on January 2, 2011.
During a flight about a month before the accident, the aviation manager noticed the pilot drained at least one of the airplane’s 12 fuel sumps while it was being fueled. Normal procedures recommend waiting 20 to 30 minutes after fueling to permit the settling of any water or any other possible contaminates.
Two days before the accident, the airplane was topped off with about 380 gallons of jet fuel, leaving a useful load of 695 pounds. Six adult males were aboard the accident flight; their total weight came to 1115 pounds. The airplane was estimated to be approximately 653 pounds overweight at takeoff.
Flight control continuity was established from the pilot’s control column and rudder pedals to the ailerons, rudder and elevator. The flaps were found in the up position and the landing gear in the down position. The power levers, propeller levers and condition levers on the central pedestal were all found full forward. No airframe anomalies were noted that would have precluded normal flight operations.
Engine examinations revealed similar internal contact signatures consistent with producing symmetrical power at the time of impact, likely in a low-to-middle range. The engines displayed no indications of any pre-impact anomalies or distress precluding normal operation. The damage to both propellers also was similar, suggesting they both impacted in a similar manner and were operating at similar power.
Security camera video of the takeoff revealed the accident airplane reached an estimated groundspeed of 130 knots and an altitude slightly greater than 140 feet agl. About two seconds into the video, a darker grayish area appears behind the airplane. At the same point where the darker grayish area appears, the airplane begins to yaw left, which progressed until the airplane impacted the ground.
The maintenance director for a local King Air 200 operator reported maintenance personnel are required to open the type’s nacelle tank every 24 months for inspection and cleaning. When this is done, it is common to find water, debris and biomicrobial contaminants in the tank. The maintenance director added that, during the accident airplane’s departure, as the airplane rotated for takeoff, if water was present in the bottom of the nacelle tank, it would shift aft and cover the fuel intake port to the engine. This “slug” of water would then flow to the fuel nozzles, where it could extinguish the engine’s fire. The engine would stop producing power and its propeller would move from coarse to fine pitch.
Samples were obtained from the fuel truck that fueled the airplane, but no anomalies with them were identified. One of the airplane manufacturer’s test pilots stated: “King Air fuel tanks must be drained before every flight; it seems like a little bit of water is always being drained off.”
Probable Cause
The National Transportation Safety Board determined the probable cause(s) of this accident to include: “The pilot’s failure to maintain directional control of the airplane during a momentary interruption of power from the left engine during the initial takeoff climb. Contributing to the accident was the power interruption due to water contamination of the fuel, which was likely not drained from the fuel tanks by the pilot during preflight inspection as required in the POH.” That’s as it should be.
Interestingly, however, the NTSB apparently spent no time considering why the relatively experienced pilot was unable to maintain control. The King Air’s published VMC, the lowest airspeed at which the airplane is directionally controllable when one engine suddenly becomes inoperative and the other engine is at takeoff power, is around 86 KIAS. The NTSB estimated the airplane had accelerated to around 130 KIAS before it began yawing. Even in the face of evidence both engines were operating at reduced power upon impact, why the pilot lost control will remain a mystery. Why the engine(s) partially failed isn’t.
