NTSB Factual Report

HISTORY OF FLIGHT

On May 4, 1994, at 1228 Pacific daylight time, an Aero Commander 100, N3661X, was destroyed by impact and postcrash fire while in the traffic pattern at Ocotillo Wells, California. The aircraft was owned and operated by the pilot and was on a solo personal flight. Visual meteorological conditions were prevalent at the time and no flight plan had been filed for the operation. The certificated private pilot sustained fatal injuries. The flight originated from the Ocotillo Wells airport at 1225 on the day of the accident.

According to witnesses, the pilot had experienced engine problems with the accident aircraft while flying in the vicinity of Ocotillo Wells airport sometime between the 6th and 13th of April, 1994. As a result, he terminated his flight and parked the aircraft at the airport. Reportedly believing the carburetor to be the source of his engine problem and, with the aid of an A&P mechanic, he removed it from the aircraft for repair.

The pilot took the carburetor to an A&P mechanic, who was willing to do the work. The A&P mechanic reported that it showed signs of rust and scale which, in his opinion, was evidence that the aircraft was being flown infrequently. Again, according to witnesses, the pilot returned to the airport about the 24th of April and, without a licensed mechanic's supervision, reinstalled the carburetor on the engine. After the reinstallation was completed, the pilot performed a ground run-up and the aircraft reportedly ran normally. A witness stated that the pilot did not fly back to Gillespie Field that day because of localized high wind conditions existing at the time and his reluctance to leave his vehicle unattended at the airport.

At 1200 on the day of the accident, the pilot returned to the Ocotillo Wells airport with the former owner of the aircraft and performed a preflight in preparation for a return flight to Gillespie Field. During what was described by the former owner as a very thorough preflight, the pilot drained an estimated 1 gallon from the aircraft's gascolator. Witnesses stated that the pilot did not use a container to collect the fuel, but rather ran the fuel over his hand and onto the ground. There are no quick drain fuel sumps on either wing's main fuel tank. The pilot then performed an aircraft run-up, during which time the aircraft was described by a witness as running normally. The pilot next taxied into position and made a soft field takeoff from runway 9 with what was described as "two notches" (15 to 20 degrees) of flaps.

The witness stated that at the time of takeoff the surface temperature was between 80 and 85 degrees with a light wind blowing from the east. The former owner, who was in two-way contact with the pilot via a handheld VHF radio, stated that after takeoff as the aircraft reached the departure end of the runway the aircraft's engine began to sputter. He described the flight path of the aircraft after takeoff as an abrupt left 180-degree left turn, paralleling runway 09. After reaching the departure end of runway 09, the pilot began what was described as another left 180-degree turn. After approximately 180 degrees of turn in a nose-high attitude, and at an estimated altitude of 100 feet agl and airspeed of 70 knots, the aircraft reportedly stalled and abruptly nosed-down.

During the flight, two brief conversations occurred between the pilot and the former owner. During the first conversation while the pilot was making his initial turn, he advised the pilot to immediately lower his nose or he would most likely stall the aircraft. After the pilot reversed course, he could hear the sputtering engine and told the pilot that he should make a precautionary landing on the runway which was to his left and in front of him. The pilot replied that he wanted to try to gain some altitude and see if the problem would clear up.

The aircraft impacted level dirt terrain on a final heading of 55 degrees in a near vertical nose-low attitude north of the departure runway. Four to five seconds after impact, witnesses heard a sound described as a "poof," at which time the aircraft ignited in flames. They stated the aircraft burned for approximately 30 minutes before the arrival of any fire fighting personnel or equipment.

PERSONNEL INFORMATION

The pilot held a private pilot certificate with a single-engine airplane rating. According to the former owner, the pilot normally carried his logbook with him while flying. The pilot reported his total flight time to be 650 hours during his last Federal Aviation Administration (FAA) third-class flight physical on February 24, 1992.

According to the A&P mechanic who repaired the carburetor and performed the last four annual inspections on the aircraft, the aircraft had flown approximately 15 to 20 hours since the last annual inspection.

The records of fuel purchases made by the pilot at the FBO where the aircraft was tied down showed that over the last 12 months the pilot had purchased 268.2 gallons of 80/87 AVGAS. Based on an estimated fuel consumption rate of 10.5- to 12-gallons per hour provided by the engine manufacturer, the pilot had flown the aircraft approximately 22 to 25 hours since May 1, 1993. There is no evidence to suggest that the pilot was accumulating flight time elsewhere. Based on the quantity of fuel purchased, it's estimated that his total flight time was approximately 695 hours at the time of the accident.

AIRCRAFT INFORMATION

An A&P mechanic at Gillespie Field, reported that this aircraft had been susceptible to accumulated water in its fuel tanks. He reported that on one occasion approximately 4 years ago the pilot had experienced engine stoppage during takeoff from Gillespie Field. After that event, the pilot had the main fuel tanks drained, removed, cleaned, and reinstalled.

WRECKAGE AND IMPACT INFORMATION

Both main wings exhibited leading edge crushing with hydraulic deformation of the upper and lower wing surfaces in the area of the main fuel tanks. Both fuel tank filler caps were found separated from the tanks and were located approximately 8 feet forward of their normal location on the filler necks.

Control continuity was established between the rudder, elevator, and ailerons. The elevator trim tab position was in a neutral position. The chain and sprocket type trim actuator revealed 16 chain links extending from both the top and bottom of the sprocket. The flaps were in the full up position; however, the torque tube that mechanically links the cockpit control handle was separated from both the right and left flaps. The flap handle was in a position that approximated "two notches" although there was no longer a mechanical linkage between the flaps and the flap position handle.

The propeller, flange, and spinner remained attached to the engine. The spinner exhibited evidence of longitudinal crushing. The propeller blades both exhibited some chord-wise rotational scarring. One blade had a slight forward bend at the tip. There was evidence of impact scarring on the aft surfaces of both blades.

The engine was found attached to the engine mounts which were fractured. The top spark plugs were removed and visually examined. The electrode wear appeared normal. All four spark plugs were dark and sooty in appearance. The plugs from the number 2 and number 4 cylinders were wet with oil, while the number 1 and number 3 plugs were dry. The oil screen was removed and visually examined. It was discolored and free of blockage or contamination.

Valve and gear train continuity was established during a 360- degree hand rotation prior to tear down. A thumb compression check verified compression in the number 1 and number 4 cylinders, while the number 2 and number 3 cylinders did not develop any detectable compression. The number 2 exhaust valve was found in the open position.

The cylinders were further examined at an engine overhaul facility in El Monte, California. All the cylinders were disassembled and inspected. The valves, seats, and guides from the number 1 cylinder were examined and there was no evidence of valve sticking.

The number 2 cylinder exhaust valve was found in an open position. A collapsed valve spring was observed and it moved freely in the valve guide. The exhaust guide was measured and found to be undersized. When a finished reamer was run through the guide, steel particles were removed.

The two number 3 cylinder valves had built up deposits on the valve heads. The intake valve had some dark sooty build up on approximately 180 degrees of the valve seat. Build up was present on the cylinder port and back side of the valve. Both push rods were found to be slightly bent.

The number 4 cylinder valves, seats, and guides appeared normal. There was no evidence of valve sticking.

The carburetor was removed and visually examined. The body sustained impact damage which separated the housing and displaced the butterfly valve. The throttle linkages were intact; however, the throttle linkage nut was not safety wired in position. The carburetor had a visible amount of water in the bowl. There was a one-piece venturi installed. The composite floats sustained heat damage. The inlet fuel screen was removed and was discolored and free of contamination.

The air box was crushed. The gascolator and oil filter element had been subjected to the postcrash fire.

The engine accessory section was burned. Both magnetos were destroyed by fire. The left magneto impulse coupler was found intact, but could not be tested.

The cabin area of the aircraft had been consumed by fire. The left door of the aircraft was found separated from the aircraft and did not exhibit fire damage. The occupied left forward seat had separated at the seat track and was found partially extending through left doorway. The left seatbelt buckle was found latched although all the nylon belt fabric had been burned away. There was no shoulder harness or harness fittings found in the wreckage.

The empennage was separated from the fuselage and did not exhibit evidence of fire damage. The vertical stabilizer and rudder were separated from the horizontal stabilizer and elevator.

MEDICAL AND PATHOLOGICAL INFORMATION

The San Diego County Medical Examiner's Office performed an autopsy on the pilot with specimens retained for toxicological analysis. The results of the toxicological analysis were negative for alcohol and all screened drug substances.

ADDITIONAL DATA/INFORMATION

The aircraft's wreckage was recovered to a storage facility at the Ramona, California, airport. The aircraft and engine were released to Ramona Aircraft Salvage at the conclusion of the engine examination.

NTSB Probable Cause

the failure of the pilot to maintain flying speed after experiencing a partial power failure while maneuvering. A factor in the accident was the failure of the pilot to drain accumulated water from the aircraft fuel system during the preflight inspection.