When it comes to figuring out what caused an airplane to crash, the first and most obvious clues often lead to a plausible, but ultimately incorrect, explanation. A case in point is an accident that occurred on June 15, 2003, at Jeannette, Pa. A Cessna 205 went down, killing the pilot and three skydivers. A fourth skydiver survived, but had no recollection of the accident flight. It became apparent to investigators that the engine suffered at least a partial power loss. Early in the investigation, it was discovered that the pilot/operator had used plastic containers in refueling the airplane, and contamination was found in fuel samples. It seemed like a sensible explanation, but it turned out that something else had been happening.
It was 3:15 p.m. when the Cessna 205 was damaged during a forced landing after its takeoff from the Greensburg Jeannette Regional Airport. VMC prevailed and no flight plan was filed for the parachute drop flight conducted under Part 91.
A witness observed the airplane taxi from the grass on the southwest corner of the airport to runway 02. The airplane immediately departed to the north and, during the initial climb, about ¼-mile from the runway, the airplane’s engine began to sputter. The airplane then began a turn to the left and initiated what appeared to be a right base entry for a landing on runway 20. The airplane continued the turn, past 270 degrees and the end of runway 20, and headed east, perpendicular to the runway. As the airplane continued past the runway, it appeared that the engine had regained power, and the airplane began a climb. The witness then lost sight of the airplane behind a trailer, but immediately heard the engine stop and the sound of an impact with trees. The witness also noted that when the airplane initially turned back, it had sufficient altitude and airspeed to reach runway 20.
A second witness was sitting on his porch about one mile northwest of the airport when he heard a “reduction in speed and/or power” coming from the airplane’s engine. The airplane climbed, then began a left turn toward the south, parallel to the runway, but “considerably west and north of [it], and 100 feet off the ground.” As the airplane approached the end of a level, grassy field, it banked sharply to the left, then abruptly to the right toward the northern end of the runway. At that time, it appeared that the airplane wouldn’t be able to reach the end of the runway, which was at an elevation above the airplane’s altitude. One of the airplane’s wings then dropped, “either due to a stall or impact with a tree,” and separated from the fuselage, before the airplane impacted the ground. The witness couldn’t recall if the airplane’s engine stopped prior to the impact. He reported, however, that the engine sounded as if it was “changing speed to try to gain altitude.”
A third witness observed the airplane during the takeoff and reported that as it tried to gain altitude, the engine was “struggling, as if the fuel mixture was too rich, or the choke was pulled out.” The airplane performed a left turn back toward the airport, during which the engine “appeared to be struggling more.” The airplane straightened its flight path and then initiated a steep right bank, during which the engine “cut out completely.” The witness lost sight of the airplane and then heard its impact with the trees.
A skydiver, who flew on the accident airplane just prior to the accident flight, was interviewed by telephone. He stated that he thought the accident flight was the airplane’s third flight of the day. He reported that two skydivers took a flight prior to his flight, and the accident flight occurred just after his. The skydiver stated that just prior to his flight, the pilot added two quarts of oil to the engine and opened the cowl flaps “for cooling.” The pilot then attempted to start the engine twice before he was successful. The flight departed about 11:45 a.m., and no engine abnormalities were noted during the flight, which lasted about 30 minutes.
The skydiver who survived the accident was interviewed in the hospital. He had no memory of the accident flight.
Examination of fuel receipts and a written statement provided by the FBO at the Mount Pleasant/Scottsdale Airport (P45), Mount Pleasant, Pa., revealed that the owner of the airplane purchased 40 gallons of 100 LL aviation fuel on April 26, 2003, and again on May 23, 2003. Both purchases were billed to Skydive Boquet, and on both occasions, the fuel was purchased and transported in eight five-gallon “polyurethane” fuel containers.
A portable trailer, from which Skydive Boquet had been conducting skydiving operations, was removed from the airport following the accident and prior to the Safety Board’s arrival. On the day after the accident, an FAA inspector interviewed the airplane owner’s wife at her residence. He observed the Skydive Boquet portable trailer at the residence, and was given access to its contents. He observed three plastic “lawnmower”-type fuel containers inside the trailer, which the owner’s wife stated were used to fuel the airplane. One container had a 2 ½-gallon capacity, and two containers had a five-gallon capacity. All three containers were empty. The eight five-gallon polyurethane fuel containers weren’t located.
The pilot held a commercial-pilot certificate with ratings for single-engine land and instrument airplane. Examination of the pilot’s logbook revealed 809 hours of total flight experience, 10 of which were in the same make and model as the accident airplane.
A handwritten flight time log was found in the airplane, with entries noting the date, beginning and ending tach times, and the “amount of fuel at start.” The last entry, noted on June 14, 2003, had a beginning tach time of 467.8 and 62 gallons of fuel at start. The tach time at the accident site was 470.4.
Examination of the airplane and engine logbooks revealed that the last two entries were for annual inspections performed on October 18, 2001, and October 4, 2002. The last inspection occurred at tach time 454.7 hours. No additional entries were noted between inspections or following the last inspection. A handwritten log found in the airplane recorded oil changes since 1995. The last two entries were dated October 2002 and March 16, 2003. The comments following the entries were “annual inspection, oil change, 454.7” and “oil change, no filter, 459.5,” respectively.
The accident site was located on airport property in hilly, wooded terrain next to an access road. The site was 250 feet northeast of the approach end of runway 20, and 20 feet below the runway’s elevation. The wreckage was examined at the site, and all major components of the airplane were accounted for at the scene.
The left wing fuel cap was secured to the tank; the tank, however, was breached. When the wing was positioned upright, a small amount of blue-colored fuel was drained into a container. Black particulate matter was subsequently observed at the bottom of the container, while white particulate matter was observed in suspension.
The throttle, mixture and propeller controls were observed in the full forward position, and the electric fuel boost pump switch was observed in the off position. The flap selector indicated the flaps were in the up position, and the fuel selector indicated the right fuel tank was selected. The words “Switch Tanks” were handwritten on the instrument paneling.
The right fuel tank cap was secured to the tank; the fuel tank, however, was breached at its inboard edge. A small amount of liquid was observed in a crevice of the fuel tank bladder.
The engine was removed from the airframe and rotated manually via the propeller. Thumb compression and valve train continuity was obtained on all cylinders. During the rotation of the engine, a spark was produced at each magneto ignition lead, with the exception of the number-five top and bottom leads, due to impact damage to the harness. The harness was then manually cut at the terminals, the engine was rotated again, and a spark was observed at both wires.
The engine-driven fuel pump was removed and examined. The pump’s drive coupling was intact, and the pump rotated freely. A small amount of blue fuel was observed. The fuel was sampled, and black particulate matter with white suspended contamination was noted.
The engine was disassembled and examined at the Teledyne Continental Motors Analytical Department under the supervision of the FAA. Examination of the cylinders revealed heavy black combustion deposits, with the number-three and number-six cylinders exhibiting signatures of operation with a foreign material. Additionally, two pieces of aluminum material were found in the combustion chamber of the number-six cylinder. The aluminum pieces were identified by the Teledyne Metallurgical Lab to be the same material as the air filter mount frame from the airframe induction system. The number-five top compression ring also was broken and severely worn.
According to the Continental report, “The ingestion of foreign material in cylinder combustion chambers can affect proper valve operation and timing and produce a combustion miss, thereby diminishing the engine power output.”
The NTSB determined the probable cause of this accident was the loss of power caused by fragments of the air filter being ingested in the engine. A factor was the pilot’s delayed decision to perform a forced landing after experiencing a partial loss of engine power.
Peter Katz is editor and publisher of NTSB Reporter, an independent monthly update on aircraft accident investigations and other news concerning the National Transportation Safety Board. To subscribe, write to: NTSB Reporter, Subscription Dept., P.O. Box 831, White Plains, NY 10602-0831.