Fuel starvation in Yak?
The owner pilot flew the Yak-18A from Old Sarum to Lincoln Wickenby.
The owner pilot flew the Yak-18A from Old Sarum to Lincoln Wickenby. It was his first flight in the aircraft since an engine change a month earlier. At Wickenby, the pilot refuelled filling both wing tanks. The aircraft departed Wickenby at 1450 hours.
Some 45 minutes later the engine "missed a beat". This was followed by fifteen minutes of normal running. The pilot climbed from 2,000 to 3,000 feet as a precaution and continued at 210 kph IAS with all engine indications normal and over 120 litres of fuel remaining. At that point the pilot realised that his radio was not transmitting although he could still receive.Some fifteen minutes after the first missed beat the engine missed again followed some minutes later by two missed beats. The pilot increased power from the normal cruise setting, of 60 to 66 per cent, to seventy, and continued the flight.With ten minutes to his destination, he passed Thruxton airfield to the south. Shortly after this and still at 3,000 feet, the engine began to cough violently and continuously. It was apparent to the pilot that he would need to land quickly and that Thruxton and Old Sarum were probably the same flying time away. Boscombe Down was the nearest airfield but with his radio not transmitting and Old Sarum only five miles to the south-west he elected to continue to Old Sarum.The pilot intended to maintain his altitude until overhead Old Sarum, and then make a right descending turn to land on R06. Due to his high workload and the haze he flew beyond the airfield and had to turn back, approaching from the south. On sighting the runway the pilot lowered the flaps and landing gear but was still at about 500 feet as he passed over the runway threshold. At that point the engine was coughing continuously but some power was still available. Given the seriousness of the situation the pilot did consider a landing on R06 from but from his position he knew it would result in a serious overrun and so he continued the right turn to reposition for the runway.Shortly after the turn was started and at about one mile south-west of R06 with height estimated at about 200 feet, the engine stopped completely. The only possible landing area was a field which the pilot had noticed earlier which was sloping and rough but was clear of the built-up area. Although high, the pilot managed to touch down heavily and fast in the field. The aircraft rolled a short distance and then flipped over onto its back. The pilot broke a window and exited with minor injuries.Whilst no conclusive reason for the engine failure could be identified, the pilot thought that the sound was that of fuel starvation. There was however plenty of fuel remaining in the wing tanks.