Flight and Loss of Power
The commercial pilot was conducting an aerial observation (surveying) flight in a piston engine-equipped multiengine airplane. Several hours into the flight, the pilot advised air traffic control (ATC) that the airplane had a fuel problem and needed to return to the departure airport. When the airplane was eight miles from the airport, and after passing several other airports, the pilot informed ATC that he was unsure if the airplane could reach the airport. Radar data showed the airplane descending and tracking toward a golf fairway, with groundspeed decreasing to a speed near the single-engine minimum control airspeed.
Witness Observations
Witnesses reported hearing an engine sputter before two loud "back-fire" sounds. One witness stated that after the engine sputtered, the airplane "was on its left side flying crooked." Others reported that the airplane turned left before it "nose-dived" into a neighborhood, impacting a tree and a private residence before coming to rest in the backyard of the residence. A witness approached the wreckage immediately after the accident and observed a small flame rising from the area of the left engine. Video recorded on a mobile phone several minutes later showed the airplane engulfed in flames.
Wreckage and Fuel System Examination
Examination of the wreckage revealed no evidence of preimpact mechanical malfunctions or failures of either engine. The fuel systems feeding both engines were damaged by impact forces; however, the examined components generally displayed only trace amounts of fuel remaining, with the exception of the left engine nacelle fuel tank. Given the extent of fire damage to this area and the witness report that the post-impact fire originated in the left engine area, it is likely that this tank contained fuel. By design, fuel in this tank could not supply fuel directly to either engine; instead, it relied on an electric pump to transfer fuel into the left main fuel tank. Fire damage precluded a detailed postaccident examination or functional testing of the left nacelle fuel transfer pump. Other pilots who flew similar airplanes for the operator, along with a review of maintenance records, revealed at least three instances of these pumps failing in the months surrounding the accident. These pilots also reported varying methods of utilizing fuel and monitoring fuel transfers from the nacelle fuel tanks, since there was no direct indication of the quantity of fuel available in the tank. These methods were not standardized between pilots within the company and relied on monitoring the quantity of fuel in the main fuel tanks to ensure fuel transfer was occurring. Had the pilot not activated this pump, or had the pump failed during the flight, it would have rendered the fuel in the tank inaccessible. Given this information, it is likely that the fuel supply available to the airplane's left engine was exhausted, and that the engine subsequently lost power due to fuel starvation.
Fuel Leak History
The accident pilot, along with another company pilot, identified fuel leaking from the airplane's left wing about a week before the accident. Maintenance records showed no actions had been completed to address the fuel leak. Due to damage sustained during the accident, the origin of the fuel leak could not be determined, nor could it be determined whether the fuel leak contributed to the fuel starvation and eventual inflight loss of power to the left engine.
Propeller and Control
Because the left engine stopped producing power, the pilot would have needed to configure the airplane for single-engine flight; however, examination of the left engine's propeller found that it was not feathered. With the propeller in this state, the pilot's ability to maintain control of the airplane would have been reduced, and it is likely that the pilot allowed the airplane's airspeed to decrease below the single-engine minimum controllable airspeed, which resulted in a loss of control and led to the airplane's roll to the left and rapid descent toward the terrain.
Toxicology
Toxicology results revealed that the pilot had taken doxylamine, an over-the-counter antihistamine that can decrease alertness and impair performance of potentially hazardous tasks. Although the results indicated that the amount of doxylamine in the pilot's cavity blood was within the lower therapeutic range, review of ATC records revealed that the pilot was alert and making necessary decisions and following instructions. Thus, the pilot's use of doxylamine was not likely a factor in the accident.