No need to go it alone…

We should not have needed to be told that a pandemic would touch every aspect of our lives, but few of us understood the extent to which it would do so. And although this particular accident occurred just before Covid-19 became widespread, it reminds us how much more we need to watch out for each other, as the pandemic continues.

Keeping to our respective bubbles comes at a cost, both for our mental well-being and our ability to interact, which are key tenets of aviation safety.

So when it comes to flying, ‘going it alone’ is not really an option, and that means all of us need to make an extra effort supporting one another.

Accident 1

The owner of G-BUDW kept his aircraft at a small farm airstrip. In the months leading up to the accident it was reported that G-BUDW had been experiencing a rough running engine and loss of engine power in flight.

In April 2019, it had an engine failure and landed in a field. The pilot was able to fix the problem and took off again 40 minutes later. It was reported that he had aborted several flights in recent months and returned to the airfield due to engine problems.

“The engine was in poor condition with multiple defects”

The owner had tried several solutions to resolve the engine problems including fitting an additional electric fuel pump. The day before the accident the owner had modified the fuel system to change the arrangement of the electrical and mechanical fuel pumps. On the day of the accident, it was reported that the owner intended to undertake a short flight to test the modified fuel system.

An old grain shed, at one end of the runway, was used to store G-BUDW and three other aircraft. When the owner of G-BUDW arrived at the airfield, another pilot was working on his aircraft. The other pilot was busy with his own aircraft so, other than exchanging some pleasantries, they did not speak. However, the other pilot was aware of G-BUDW’s owner preparing his aircraft.

The other pilot later heard the aircraft start and reported that ‘the engine sounded fine’, a few minutes later he saw the aircraft taxi away.

When he heard G-BUDW start its take-off, he walked out of the hangar to watch and recalled it was 1232. He reported that when he saw the aircraft come over the crest of the runway it was at about 5-10ft and the engine sounded ‘good’. He then heard the engine go much quieter ‘as if it had been altered to tick over’ and was aware the aircraft was no longer climbing normally. He heard the engine ‘get loud again then hesitate and get quiet again’ and described the engine as ‘fizzing and popping’. The aircraft passed directly over his head, clearing the shed roof by 20-30ft. As the aircraft went out of sight, he could no longer hear the engine and assumed the pilot would be attempting a forced landing in a field. He ran around the shed but could not see the aircraft.

He returned to his car and started a search of the surrounding area but was unable to locate the aircraft. At 1252, he called the pilot of one of the other aircraft in the hangar and asked if he could come to the airfield and use his aircraft to search the area. At 1315, the other pilot arrived, prepared his aircraft for flight and started to taxi to the far end of the airfield for take-off.

As he taxied over the crest of the runway, he saw the wreckage of G-BUDW in the field to the north of the runway. They alerted the emergency services at 1328 and went on to attempt to revive the pilot without success.

The Colibri MB2 aircraft is a homebuilt single-seat light aircraft with fixed landing gear, constructed predominantly from spruce and plywood, and is operated under a Permit to Fly issued by the LAA.

G-BUDW was built in 1992 and the current owner purchased the aircraft in 2007 and flew it regularly. He undertook the maintenance of the aircraft himself, but no evidence of a maintenance programme was found.

The aircraft’s annual inspection was carried out by a local LAA inspector, as required to maintain the Permit to Fly. Since the engine had been rebuilt, 605 hours of running time had been logged.

The owner of G-BUDW held a valid UK PPL with a valid Single Engine Piston (Land) rating. He had previously held an IMC rating, but this was no longer valid. The pilot’s logbook recorded that he had a total of 1,300 flying hours. Since April 2016, when his current logbook started, he had completed 221 hours in G-BUDW.

He had completed a pilot medical declaration on the 15 December 2017, which was valid until he reached the age of 70. There was no evidence that the accident was caused by any medical condition. Toxicology found no evidence of any substance which may have contributed to the accident.

The accident site was discovered approximately one hour after take-off. It is not known for certain when the accident occurred or where the aircraft flew after the initial sightings, but the fact that the aircraft was not recorded on radar suggests it did not gain significant altitude. There was no record of the pilot contacting any of the air traffic control frequencies.

Therefore, the most likely scenario is that after take-off the pilot tried to fly a circuit to the north of the airfield in an attempt to land back on the runway when it struck the ground.

The investigation identified that the engine was in poor condition with multiple defects which could have caused the loss of engine power and rough running. The most significant of these were the crack in the cylinder head, the split in inlet manifold joint and deposits on the valve seats. The crack in the head of cylinder 2 would have resulted in a reduction in compression and engine power. The split in the manifold would allow air into the manifold, weakening the mixture and causing the engine to run hot. The deposits on the valves were most likely a mixture of carbon and oil and not untypical for an engine of this age. In cylinders 1 and 2 it was noted that some of the deposits had flaked off the head and there was evidence that these flakes had been caught and crushed in the valve seats. This would have prevented the valves from sealing, resulting in low compression and loss of engine power. From the sealing checks, only cylinder 4 sealed effectively.

The original power output of the engine was not known but with the defects identified during the examination its power would have been severely reduced. The weather conditions on the day were also conducive to carburettor icing and following the long taxi over wet grass, this may have further reduced engine power. The long-term engine problems are likely to have been caused by the crack in the head of cylinder 2 and the split in the inlet manifold joint.

However, it is believed that on the accident flight, a detached carbon flake caught under the exhaust valve of cylinder 1, further reducing the engine’s performance to a point where flight could not be sustained.

Although the checks for the Permit to Fly had been signed off by the LAA inspector, no evidence of long-term maintenance planning was identified.

The engine logbooks recorded the completion of regular annual tasks, which were predominantly oil changes and tappet adjustment. The LAA recommends monitoring of various engine parameters and taking appropriate action when deviation from the ‘norm’ is noted. During the investigation no evidence was found that engine parameters were being regularly recorded. This investigation demonstrated that a compression check by feel rather than using compression test equipment is not a reliable indication of the condition of the cylinders. Had the checks and servicing been carried out using the LAA guidance it is likely the crack in cylinder 2 and the inlet manifold leak would have been identified. While there was no defined overhaul period for G-BUDW’s engine its poor condition indicated that it required a top-end overhaul.

The pilot had made several changes to the aircraft fuel system while attempting to resolve an engine problem. There was no evidence that these changes had been inspected by a LAA inspector or that they had been discussed with, or approved by, LAA Engineering. While there is no evidence that these contributed to the accident, it is important that owners/ pilots should follow the correct inspection and approval process when making changes to the aircraft configuration.

“It is about being human and caring as we all struggle with today’s challenges”

An engine problem in a single engine aircraft need not necessarily result in a fatal accident. During this flight it is likely the pilot experienced a partial engine power loss but felt he had enough height and power to return to the runway.