Unwise go-around after power loss
PUBLISHED: 17:43 22 June 2011 | UPDATED: 14:03 10 October 2012
Three days before the accident, whilst preparing his Piper Comanche 260 for flight, the pilot found that the battery was discharged, and had it changed. On the day of the accident he was able to start the aircraft on
Three days before the accident, whilst preparing his Piper Comanche 260 for flight, the pilot found that the battery was discharged, and had it changed. On the day of the accident he was able to start the aircraft on the first attempt and noted that the ammeter indicated that the battery was charging.
The Comanche took off from Leicester’s Rwy 33 with full tanks, and as it climbed, the pilot noticed that the low voltage warning light had illuminated, so he decided to carry out a circuit to land back on the departure runway.
On approach, he noticed a tractor and trailer that appeared to be moving towards the threshold, so he reduced the rate of descent to ensure that he cleared the vehicles safely and landed further along the runway.
On touchdown, the aircraft bounced twice, so he started a go-around, but whilst climbing back into the circuit he heard an “odd pop” from the engine, after which it began to run “very, very roughly”, so the pilot radioed to say that he would land in the middle of the aerodrome.
An instructor in a helicopter operating nearby estimated that the Comanche was at about 100 feet when it completed a left turn from its north-westerly takeoff track onto an easterly heading. The engine continued to run intermittently and make noises that a witness on the ground described as “like shotgun fire”.
At a point south of the Rwy 28 threshold, with the aircraft descending to within 50 feet of the ground, the pilot attempted to position the Comanche onto a right-hand base leg for Rwy 33. It was seen to climb very slowly then adopt a nose-down attitude and roll to the right.
The pilot reported that at this point the engine had ceased to produce power, and he responded by applying up elevator, which resulted in a nose-up attitude but no decrease in the rate of descent. This was followed almost immediately by the aircraft hitting the ground in a wheat field some 600metres southeast of Rwy 10.
Impact marks showed that the aircraft struck nose-first, in a slight left bank, then bounced and travelled for 30 metres before coming to rest upright. The pilot suffered facial injuries when his head struck the control yoke during impact and he was also aware of back pain.
Shortly afterwards the helicopter landed nearby and its occupants went to assist, one of them using an extinguisher to attack a fire in the engine bay. Strip examination of the Comanche’s Lycoming IO-540-D4A5 engine and its accessories did not reveal any defects that could have accounted for the power problems the pilot reported, nor could the low voltage warning after takeoff be explained.
One possibility considered was a fuel leak from the inlet fitting of the fuel injector. Insufficient fuel delivery could have caused rough running at a high power setting, and if fuel had already been leaking from this fitting before the crash, a fire would have more readily ignited at initial impact causing the narrow trail of scorched wheat that was noted at the accident site.
However, there were no records of this fitting having recently been disturbed, and examination of stripped threads on it could not establish if the fitting had been loose before it was pulled out on impact, as had been observed during investigation of a similar accident. Thus, no definitive cause of the engine power loss could be established.
The pilot considered that when the aircraft was positioned south of the Rwy 28 threshold, he should have attempted to turn left for a landing on that runway. He commented that it was not an ordinary engine failure in that it progressed from “a couple of pops” to a series of explosions, accompanied by severe vibration.
He recalled that the aircraft had been in a level attitude when the engine failed completely, and judged that it not stalled because it pitched up in response to nose-up elevator control. However, the subsequent change to a nose-down attitude had been very rapid.
Notes the AAIB, “Evidence from previous accidents and theoretical analysis both suggest that an attempt to return to the departure runway in the event of engine failure in a single-engine aircraft is unlikely to be successful if the failure occurs shortly after takeoff. In this instance, after going around with what appeared to the pilot to be a partial engine failure, the aircraft turned through approximately 230º to approach Rwy 10…CAA Safety Sense Leaflet 1a – Good Airmanship includes the following advice: In the event of engine failure after takeoff, if the runway remaining is long enough, re-land and if not, never attempt to turn back. Use areas ahead of you and go for the best site. It is a question of knowing your aircraft, your level of experience and practice and working out beforehand your best option at the aerodrome in use.
“Engine failure shortly after takeoff requires the pilot of a single-engine aircraft to decide very quickly where to land. Despite comprehensive advice to the contrary, the inclination to attempt to return to the departure airfield may be hard to resist, especially if the failure is partial and gives the impression of producing sufficient power to sustain flight. Although theoretically a return may be possible after the aircraft has climbed to several hundred feet, most single-engine aircraft are unlikely to complete this manoeuvre successfully unless the failure occurs considerably higher. The aircraft would not have had sufficient height at the point it passed the threshold of Rwy 28, to turn for landing on that runway…All the available evidence suggests that, following engine failure in a single-engine aircraft, it is safest to land in open ground ahead. There is a risk of damage when landing on other than a prepared runway, but such damage is likely to be less severe if the pilot can accomplish a touchdown while still in control of the aircraft. In this case the aircraft stalled at a relatively low height above the ground. The ensuing high rate of descent, combined with a turn, resulted in touchdown at low forward speed. Had the aircraft stalled at a greater height, its speed on impact would have been higher, with possibly fatal consequences.”