WPR16FA112

The pilot's inability to return to the departure airport due to an unspecified in-flight emergency for reasons that could not be determined during a postaccident examination of the airplane.

The airline transport pilot and a passenger departed on a local flight as part of a flight of two airplanes in daytime visual meteorological conditions. Shortly after takeoff, witnesses heard the engine popping; another witness reported a possible loss of power. The airplane entered a right turn and appeared to slow. It subsequently impacted the ground and a postimpact fire ensued. Recorded communication obtained from the air traffic control tower revealed that the pilot transmitted a mayday call before the accident; however, he did not state the nature of the emergency. Postaccident examination of the airframe, flight control system, and the engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. The airplane was originally equipped with left- and right-wing fuel tanks, as well as a reserve tank located within the left tank. Maintenance records revealed that the fuel system was modified from its original configuration to remove the reserve tank and interconnect the left and right tanks, therefore allowing for an "On/Off" selection and eliminating the need to switch tanks in flight. The fuel system was again reconfigured; however; no entries in the maintenance records were found regarding this modification. Postaccident examination of the airplane and interviews with the operator revealed that the tank interconnect had been removed, and that the reserve port on the fuel selector valve had been plugged with a blanking cap.  The fuel selector valve face displayed four quadrants, one each for the Left, Right, and Off positions, and a blank quadrant where the Reserve position had been previously. Although the Reserve position was not marked, the selector could still be moved to that position, which would result in a loss of fuel flow to the engine.   During the wreckage examination, the fuel selector valve was found in a position consistent with the reserve position; however, the fuel selector valve position at the time of the accident could not be determined. It is possible that, if the airplane experienced a momentary loss of power, and in accordance with the practice most commonly used by T-6 pilots, the pilot would have selected what was the "reserve" position (although not marked), even though that port was plugged. This would have led to a total loss of engine power due to fuel starvation.

FFZ is a tower-controlled airport located at an elevation of 1,394 ft mean sea level (msl). The airport is equipped with two asphalt runways: 4R/22L, which is 5,101 ft long, and 4L/22R, which is 3,799 ft long. An entry in the aircraft maintenance records indicated that the airplane was completed by North American Aviation on December 15, 1942, under Type Certificate A-2-575, and shipped directly to the South African Air Force (SAAF). The airplane was originally equipped with left- and right-wing fuel tanks, as well as a reserve tank located within the left tank. The SAAF modified the fuel system as outlined in the supplemental type certificate (STC) SA00636CH (The STC is in the public docket). The modification allowed fuel in the right fuel tank to flow directly to the left fuel tank (from which the reserve fuel tank had been removed) through an interconnecting fuel pipe between the two tanks, and then from the left tank through an "ON/OFF" valve to the engine, thus making fuel tank selection during flight unnecessary. No maintenance records were recovered for the period between 1989 and 1995. In 1996, the airplane returned to and was registered in the United States. On April 11, 1997, the airplane was issued a Special Airworthiness Certificate in the experimental category. On May 3, 1997, a Standard Airworthiness Certificate was issued, which indicated that the airplane conformed to Type Certificate Data Sheet (TCDS) A-2-575 Revision 13. However, a postaccident review of the TCDS indicated that, based on its S/N, the accident airplane was not eligible for a standard type certification. The airplane's fuel system was reconfigured at an unknown time and no entries in the maintenance records were found regarding the fuel system modification. The postaccident examination of the fuel system indicated that the interconnecting fuel pipe between the left and right tanks had been removed and that the reserve port on the fuel selector valve was capped. The left fuel tank reserve port stand pipe was also removed. The fuel selector valve face displayed four quadrants, one each for the Left, Right, and Off positions, and a blank quadrant where the Reserve position had previously been located. Although the Reserve position was not marked, the selector could still be moved to that position and would result in a loss of fuel flow to the engine since that port had been capped. During the wreckage examination, the fuel selector valve was found in a position consistent with the Reserve position; however, the position of the valve at the time of the accident could not be determined. In an interview with an FAA inspector, the operator stated that the fuel selector was made of cork and that excessive manipulation of it could lead to damage or internal wear. The fuel selector was rarely moved and normally stayed on the left tank position, as most flights were short and did not necessitate the use of both fuel tanks. The selector would only be moved during flights of extended duration or if the pilot perceived a fuel-related issue. The operator indicated that the last time the airplane flew before the day of the accident was on the weekend of April 12, 2016 from FFZ to Phoenix-Mesa Gateway Airport (IWA), Mesa, Arizona, and back, which was about 20-minute flight each way. The airplane was topped off at IWA. The operator stated that the accident flight was the second flight of the day; the first flight lasted about 30 minutes or less. The FAA inspector estimated that the airplane would have flown about 50 minutes to an hour since it was refueled on the left fuel tank. When the FAA inspector queried the operator regarding their leaning procedures, they stated that on most of their flights, which were 20-30 minutes in length around the area, they would lean very little if at all. However, they would lean on the rare longer cross-country flights or if it was at a high-altitude airport. The FAA inspector also interviewed a few T-6 pilots, and the common practice amongst them was that, in case of a fuel interruption, a pilot should select a "reserve" position for those airplanes that were equipped with the reserve position. The nearest automated weather report was from Phoenix-Mesa Gateway Airport (IWA), located 10 miles south of the accident site. The 1859 observation included wind from 290° at 9 knots, 20 statute miles visibility, scattered clouds at 12,000 ft above ground level (agl), ceiling broken at 15,000 ft, temperature 29°C, dew point 4°C, and an altimeter setting of 29.77 inches of mercury (inHg). The 1851 observation at Sky Harbor International Airport (PHX), located 14 miles from the accident site, included wind from 310° degrees at 26 knots gusting to 37 knots, 9 miles visibility, scattered clouds at 2,100 ft and 11,000 ft, ceiling broken at 21,000 ft and 25,000 feet, temperature 27°C, dew point 6°C, and an altimeter setting of 29.75 inHg. A peak wind of 320° at 37 knots was recorded at 1844. The complete weather report is appended to this accident in the public docket. The Maricopa County Office of the Medical Examiner, Phoenix, Arizona, performed an autopsy of the pilot. The cause of death was determined to be "multiple blunt force injuries." The FAA Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma, performed toxicology testing on specimens from the pilot. Specimens tested negative for carbon monoxide in blood and ethanol in urine. No presence of amphetamines, opiates, marijuana, cocaine, phencyclidine, benzodiazepines, barbiturates, antidepressants, or antihistamines was detected in urine. The pilot, age 43, held an airline transport pilot certificate with airplane single-engine land and multi-engine land ratings. The pilot was issued a first-class Federal Aviation Administration (FAA) medical certificate on July 22, 2015, with no limitations. On the application for that medical certificate, the pilot reported 11,950 total hours of flight experience of which 465 hours were in the previous six months. The pilot's digital logbook, with entries from January 1, 2013, through April 24, 2016, revealed that during that period, the pilot accumulated a total of 2,744.1 flight hours. The pilot had about 50 hours of flight experience in the accident airplane make and model, including about 11 hours in the accident airplane. The two-seat, single-engine, low-wing, retractable landing gear airplane, serial number 84-7721, was manufactured in 1942. It was powered by a Pratt & Whitney R1340-AN, 550-hp, reciprocating engine, serial number 2D700, which drove a Hamilton Standard two-bladed, controllable pitch propeller. A review of maintenance records showed that the most recent annual inspection was completed February 13, 2016, at a total aircraft time of 8,746.9 hours. The accident site was located about 1,400 ft from the departure end of runway 22L. The airplane impacted terrain and came to rest on a road on a heading about 37° degrees magnetic. All major structural components of the airplane were located within the wreckage debris path. The wreckage path was oriented on a heading about 12° magnetic and was about 380 ft in length. The first identified point of contact (FIPC) was a 15-ft-tall orange tree. About 20 ft from the tree strike was a section of disturbed ground, about 12 ft in length and 1 ft in width, consistent with a wing strike. The left wing separated from the fuselage and was inverted. The left wing tank, near the inboard separation, was visible and exhibited impact signatures. The remaining debris was contained on the road, with the exception of a separated propeller blade tip. The left aileron and wing tip were separated from the wing and found on the east side of the debris field. About 100 ft to the south-west of the debris field was the separated oil cooler. The oil cooler had impact damage and was surrounded by a pool of oil. The main wreckage was about 170 ft from the FIPC and consisted of the fu