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30th of July 2000, fuel contamination, Blog #610

Updated: Aug 8, 2023

The pilot of a Piper PA-30 Twin Commanche was preparing his aircraft for a flight from Elmsett to Blackpool (United Kingdom), with one passenger, on this day in 2000. After completing the external walk-around the fuel drains for the main, auxiliary and tip tanks were checked for water.

The aircraft wreckage in its final position (Source: © unknown)

The fuel drains are located in the fuel selector valves, accessible through an access panel directly behind the fuel selector valves, which are located just ahead of the main spar, between the pilot seats in the cabin.

Fuel flow can be observed via a transparent tube (connected to the filter bowl of each selector valve) extending through a hole in the bottom of the fuselage. Fuel should be collected in a container to check for (water) contamination. This requires two persons, one to operate the drain valves and one to collect the fuel in a container. On this occasion, the pilot only visually checked the transparent tubes. The engines were started after the completion of the flight preparations

and the aircraft was taxied to runway 23 for take-off. The main fuel tanks were selected and the engine power checks were completed satisfactorily. Take-off clearance was obtained and the aircraft accelerated to 80 knots at which speed it became airborne. The aircraft was held level with the intent to accelerate to 100 knots before starting to climb. The pilot became aware of a slight yaw at this point and a check of the engine instruments showed that the right-hand engine was only producing 2000 RPM. With insufficient space for an immediate landing, the take-off was continued however the aircraft failed to accelerate above 80 knots. The landing gear was being retracted when the aircraft violently yawed to the right, the nose was lowered to increase speed in an attempt to regain directional control. A shallow climb was initiated to avoid rising terrain and the failed engine procedure was initiated. At the same time, a left turn was initiated to avoid a house, and this caused further losses of height. The right wingtip struck the ground and the aircraft spun around, continuing backwards into a field, coming to a stop in a hedge.

The Piper PA-30 Twin Commanche fuel system (Source; ©Piper)

The pilot and passenger were able to unbuckle their harnesses and evacuated the aircraft, they had only sustained minor injuries.

There was no post-impact fire. The wreckage was inspected and during this inspection, water was found in the fuel control unit for the right-hand engine, Since the last refuelling of the aircraft (at Gloucestershire Airport, UK, two days previous) the aircraft had been parked outside in heavy rain. An experienced (on-type) Aircraft Engineer was interviewed and commented that he was aware of water ingress into the fuel system of this type of aircraft. There is no ready explanation as to how this occurred in this particular instance.

The manufacturer's Information Manual for the PA-30 Twin Commanche contains Operating Instructions for the pre-flight inspections, including draining of the fuel valves and lines. This is divided into separate procedures: one for use, "before each flight" and an expanded procedure, "when the aircraft has been exposed to below freezing temperatures or it is suspected that water may have entered tanks". In both cases, the instructions are explicit that the drained fuel should be collected in a container and examined for water contamination and that, for the expanded procedure, the drains should be opened for 10 to 12 seconds (for each main and auxiliary cell). For the normal pre-flight inspection, the Operating Instructions specify nothing further for drain operation than "a few seconds" for each cell.

Th AAIB (Air Accidents Investigation Branch) does not state a probable cause in their report but it appears that water contamination caused the right-hand engine to fail. The AAIB report on this accident, which served as the source for this blog, can be accessed by clicking on the .pdf file below.

Piper Fuel Contamination 30Jul2000
Download PDF • 73KB

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