Skiatook, OK, USA
N95442
MOONEY AIRCRAFT CORP. M20
The pilot reported in a written statement that the airplane had just been released from a repair shop after the engine exhaust system had been rebuilt. He added that the engine was tested before being released from the repair shop, and no mechanical anomalies were noted. According to the pilot, while completing the preflight run-up, the engine quit running when it was at 1,800 rpm. He got out of the airplane and did a walk-around and noticed nothing abnormal. He then attempted multiple engine starts, and "the engine would try to start but would not keep running." Subsequently, he was able to get the engine started. The pilot reported that he conducted a preflight but did not visually check or measure the fuel in either tank during the preflight, but before flight, he believed the left fuel tank was empty. He then took off and circled the airport in a right traffic pattern, flew down the runway at 2,000 ft mean sea level, then proceeded on-course to his destination. The pilot further reported that, when he departed, the left tank low fuel light was on, the right fuel tank light was off, and the fuel level in the right tank was between 1/8 and 1/4 full. The fuel selector was selected to the right fuel tank. He added that, about 7 nautical miles from the destination airport, the right tank low fuel light illuminated for about 3 to 5 seconds and then extinguished. As he turned the airplane onto final, he added power and "pumped [the] throttle several times with no response from [the] engine." He added that when the engine lost power, he switched the fuel selector from the right tank to the left tank out of habit. The pilot reported that the airplane continued to sink and that he made a slight right turn to avoid power lines and a street with several cars and landed hard in a large yard. The right wing sustained substantial damage. A Federal Aviation Administration aviation safety inspector reported that, after the accident, he and the pilot drained the fuel from the airplane. He reported that they sumped about 3.25 to 3.50 gallons of fuel from the right tank and about 1 gallon of fuel from the left tank. The Airplane Flight Manual (AFM) stated that the airplane had a total unusable fuel volume of 3 gallons and was equipped with left and right fuel low annunciation lights that indicated when 2.5 to 3 gallons of usable fuel remained in the respective tanks. The AFM further stated, "switch to fuller tank." According to Title 14 Code of Federal Regulations Part 91.151 Fuel requirements for flight in VFR [visual flight rules] conditions: (a) No person may begin a flight in an airplane under VFR conditions unless (considering wind and forecast weather conditions) there is enough fuel to fly to the first point of intended landing and, assuming normal cruising speed - (1) During the day, to fly after that for at least 30 minutes. Estimated fuel requirements for the flight, based on the pilot's statement that the airplane normally burned "28-30 gph [gallons per hour] on takeoff power and 18-19 gph on cruise power" and the reported flight profile, indicated that a minimum of 8.7 gallons were required for the flight. When an additional 30-minute reserve was added, a total of 17.96 gallons were required for the flight. As noted previously, the pilot reported that, before flight, the fuel gauges read 1/8 (4.7 gallons) to 1/4 (9.4 gallons) full on the right fuel tank, and he believed the left fuel tank was empty. It is likely that the engine was starved of fuel after the pilot completed multiple turns in the traffic pattern with low fuel in the right fuel tank, and that, subsequently, when the pilot switched the fuel selector to the left fuel tank, which contained only about 1 gallon of fuel, fuel starvation occurred.
The pilot reported in a written statement that the airplane had just been released from a repair shop, where the engine exhaust system had been rebuilt. He added that the engine was tested before being released from the repair shop and no mechanical anomalies were noted. According to the pilot, he took possession of the airplane, and while completing the preflight run-up, "the engine died upon the 3rd time of cycling the propeller. The engine was at 1800 RPM [revolutions per minute] when it quit running, [it] totally died." He added that he, got out of the airplane and did a walk around and noticed nothing abnormal. He then attempted multiple engine starts, and "the engine would try to start but would not keep running." Subsequently, he was able to get the engine started, he then completed the "pre-flight checks" with "no issues," and he took off. He added that after takeoff, he circled the airport in a right traffic pattern and flew "back down the center line" of the runway at 2,000 ft. mean sea level, before proceeding on-course to his destination. The pilot further reported that "upon departure," the "left tank low fuel light was on, right fuel tank light was off and [while] level showed between 1/8 and 1/4 full." The fuel selector was selected to the right fuel tank. He added that about 7 nautical miles from the destination airport, the right tank low fuel light illuminated for about 3-5 seconds, and then stopped illuminating. As the airplane entered the traffic pattern, he completed a left base turn and then a left turn to final "with power pulled back" because the airplane was "a bit high on left base." As the airplane turned onto final, the "glide path altitude looked correct" and he added power, but there was no response from the engine. He added that he "pumped throttle several times with no response from [the] engine." The pilot reported that the airplane continued to sink, and he made a slight right turn to avoid power lines and a street with several cars, and landed hard in a large yard. The right wing sustained substantial damage. During telephone conversations with the NTSB investigator-in-charge, the pilot described numerous details about the flight and the accident airplane. He reported that he did not visually check or measure the fuel in either tank during the preflight, but prior to flight he believed the left fuel tank was empty and the right fuel tank gauge read 1/4 to 1/8 full. He reported that when the engine lost power, the propeller was wind milling, the mixture was rich, and he moved the throttle to full forward. He added that when the engine lost power, he switched the fuel selector from the right tank, to the left, out of habit. He reported in numerous conversations, that he could have run out of gas, but he was unsure. He also added that, "I'm not going to deny that my turns in the traffic pattern may have introduced air into line and then the engine quit." The pilot reported on the NTSB Form 6120.1 Pilot/ Operator Aircraft Accident/ Incident Report that the engine failed. A Federal Aviation Administration (FAA) aviation safety inspector reported that after the accident, he and the pilot drained the fuel from the airplane. He reported that while sumping the right wing, via the right wing sump, about 3.25 to 3.50 gallons were drained into a bucket. He reported that they were using a combination of buckets due to the quantity, and "at the very most" a quarter of fuel, or less, was spilled. He added that he drained about one gallon of fuel from the left fuel tank. About two and a half months after the accident, the pilot provided an additional emailed written statement and additional photos. He reported that he measured the drained fuel quantity as "4.45 gallons less spillage." He added that the "gas a lator [gascolater] housing was removed from the plane where a fair amount of lint type material was observed that could [had] restricted fuel flow to the engine." The pilot further added that he normally burns "28-30 gph [gallons per hour] on takeoff power and 18-19 gph cruise power." The FAA inspector was not present for the pilot's additional fuel measurements, or his airplane examination. The airplane flight manual (AFM) stated in part that, fuel is carried in two integrally sealed sections of the forward inboard area of the wings and the total usable fuel capacity was 75.6 gallons, with a total unusable fuel volume of 3 gallons. The AFM further stated that, fuel feeds from one tank at a time to the selector valve and through the electric fuel pump enroute to the engine-driven pump and the fuel injector unit. The airplane was equipped with a three-position fuel selector valve located on the floorboard between the left and right cockpit seats. The valve allowed the pilot to select the left or right fuel tank, or select the fuel off. The AFM stated that the airplane was equipped with left and right fuel low annunciation lights, that indicate 2.5 to 3 gallons of usable fuel remain in the respective tanks and further stated: "switch to fuller tank." The AFM also stated in part: "Warning: Takeoff maneuvers when the selected fuel tank contains less than 12 gallons of fuel have not been demonstrated." According to the FAA electronic document retrieval system, the airplane underwent a "Rocket 305" engine conversion, which was completed in March 1998. The conversion was performed under FAA approved supplemental type certificate numbers SA00243SE and SA5691NM. In part, the conversion involved removal of the original engine and installation of a TSIO-520 engine, increasing the airplane's horsepower to 305. According to 14 Code of Federal Regulations Part 91.151 Fuel requirements for flight in VFR conditions: (a) No person may begin a flight in an airplane under VFR conditions unless (considering wind and forecast weather conditions) there is enough fuel to fly to the first point of intended landing and, assuming normal cruising speed - (1) During the day, to fly after that for at least 30 minutes. The FAA Pilot's Handbook of Aeronautical Knowledge stated in part: Fuel Gauges The fuel quantity gauges indicate the amount of fuel measured by a sensing unit in each fuel tank and is displayed in gallons or pounds. Aircraft certification rules require accuracy in fuel gauges only when they read "empty." Any reading other than "empty" should be verified. Do not depend solely on the accuracy of the fuel quantity gauges. Always visually check the fuel level in each tank during the preflight inspection, and then compare it with the corresponding fuel quantity indication.
The pilot's improper decision to conduct the flight despite the fuel gauges indicating that there was insufficient fuel for the flight, which resulted in the low amount of fuel in the right tank becoming unported during the multiple turns, and his subsequent improper decision to switch to the nearly empty left tank, which led to a loss of engine power due to fuel starvation.
Source: NTSB Aviation Accident Database
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