INCIDENT REPORTS PHOTOS BY KEITH WILSON/SFB PHOTOGRAPHIC - File images for illustrative purposes only
Pitch trim warning
EV-97 TEAMEUROSTAR UK NR BUILTH WELLS 18 SEPTEMBER 2016
Pilots are being warned of a potential hazard following a double fatality after a left wing failure on an EV-97 Eurostar. The pilot had arranged to fly from Arclid
Airfield, Cheshire, to Swansea which should have taken around 80 minutes. Radar data later showed that the altitude during the flight varied but remained above 2,000ft amsl until the accident. At 1045 hrs the Eurostar, which had been
flown generally straight and level, started a descent followed by a climbing turn to the right, and then a climbing turn to the left, before turning right onto a course to intercept the original track between Arclid and Swansea. At 1053 hrs, it started manoeuvring again, turning, descending and climbing before levelling off at 4,100ft. Three minutes later, it descended again, levelled at 2,400ft and then after half a minute started to climb again. Witnesses walking along a track half a mile to the east of the accident site in a field near Builth Wells said the Eurostar had flown over them in a normal level, or slightly climbing, attitude. After it had passed they walked back down the track and one noticed that it
now appeared to be in a vertical, climbing attitude. After glancing away, the person looked again and saw it nose-down and rotating in a spiralling descent. As she watched she noticed that one wing had apparently ‘turned’ and was pointing towards the tail. The wreckage was found, about 360 metres from the last recorded radar return resting in its initial impact crater, indicating a high vertical speed and low forward speed on impact. No pre-existing material defect, or
significant design issue, was found. The left wing failure was therefore probably due to a high aerodynamic load in excess of the 4g limit, probably closer to and possibly exceeding 6g. It is most likely to have occurred as a result of an attempted recovery from an inadvertent manoeuvre inducing the structural overload. The weight of the aircraft at the time of the accident was probably between 471 and 496kg, at least 21kg above Max Take- Off Weight. The cause of the manoeuvre couldn’t be
identified, but the AAIB has made a Safety Recommendation relating to the pitch trim mechanism, pointing out that there might have been an inadvertent trim operation because there is a potential for the pitch trim lever to be moved rapidly full-range by accident. The elevator trim tab was
operated via a ‘Bowden-type’ cable and a lever between the seats, pushing it forward provides nose-down trim pulling it aft gave nose-up trim. On the EV-97, the pitch trim lever friction is not adjustable in flight. It can only be adjusted during maintenance by tightening a nut beneath the floor. According to the maintenance manual the nut should be adjusted to ensure a minimum 1.0 kgf force is required at the lever’s end to move it. Its position between the seats has resulted in occasions of inadvertent movement. Other possible reasons for the manoeuvre include an event within the aircraft taking the pilot by surprise, a medical issue — blood tests indicated that carbon monoxide toxicity was not a factor — or incapacitation of either pilot or passenger, or avoiding a potential collision with an object or bird. The AAIB recommended that “The
Civil Aviation Authority require the Light Aircraft Association, the British Microlight Aircraft Association, Light Sport Aviation Ltd and Evektor to conduct a joint review of the design and location of the pitch trim mechanism on the EV-97 Teameurostar UK, and the amateur-built EV-97 Eurostar, to identify whether modification is required to prevent inadvertent, improper or abrupt input.”
FOR FURTHER INFORMATION ON INCIDENT REPORTS, VISIT
AAIB.GOV.UK 38 CLUED UP Summer 2018
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