History of the Flight
The accident flight was the return leg of a trip from Stapleford Aerodrome, Essex, to Lydd Airport, Kent. On board were a pilot (the commander) and a passenger, who held a Private Pilot's Licence and was the handling pilot for the exercise. The exercise was conducted near Hanningfield Reservoir, northwest of Southend Airport. After performing a clean stall and recovery, the pilot executed a steep turn to the right, then a steep turn to the left with a load factor of about 2g. During the left steep turn, the power lever was advanced from 80% to 100% in one to two seconds, and the engine momentarily shuddered. A second steep turn to the left caused another momentary shudder. The commander observed propeller overspeed and engine power exceedance cautions. The pilot lowered the nose to gain airspeed for a wingover-type manoeuvre, at which point both occupants realized the engine had lost significant power. The ECU switch was set to 'ECU B' but was ineffective. Shortly after, 'ECU A' and 'ECU B' caution annunciations appeared, engine power dropped to 7%, and the engine ceased responding to power lever inputs. No low fuel annunciations were noted. An emergency was declared to Southend Airport, and preparations were made for a forced landing in a field. The approach speed was high, and the aircraft touched down well into the field. Insufficient distance remained to stop, and the aircraft struck a hedge and a small ditch, causing the nose gear to collapse rearward and damaging the propeller, lower front fuselage, and left wing. The aircraft remained upright, no fire occurred, and the two occupants exited unharmed. Emergency services attended promptly.
Aircraft Information
The Diamond DA 40 D is a four-seat, low-wing monoplane with a composite structure. It is powered by a single Thielert TAE 125-01 diesel piston engine, rated at 99 kW (135 HP) at sea level. The engine drives a three-bladed variable-pitch propeller via a 1:1.69 reduction gearbox. The maximum continuous propeller speed is 2,300 rpm. The engine and propeller are controlled by a digital Engine Control Unit (ECU) with two independent channels (ECU A and B). The ECU can record faults and data for post-flight analysis but does not monitor fuel quantity. Engine parameters are displayed on two panels: the Compact Engine Display (CED) and the Auxiliary Engine Display (AED).
Fuel System
The aircraft was equipped with optional long-range fuel tanks, comprising two tanks per wing. Total usable fuel capacity is 147.6 litres. The engine draws fuel only from the left inboard main tank. Fuel is transferred from the right auxiliary tank via an electric pump. Unused fuel from the engine is returned to the main tank after being cooled through the auxiliary tank. Each main tank has a fuel trap to ensure supply during manoeuvres. Fuel quantity is indicated by circular LED bar gauges, with a low fuel caution at 3 USG (11.5 litres) and a red warning when empty. The gauges are calibrated for straight and level flight.
Fuelling and Fuel Consumption
The aircraft was refuelled to full capacity on 28 December 2006, verified by the commander and an independent witness. That day, it completed four flights totalling 3.5 hours. It did not fly again until the accident day, when it flew a 45-minute outbound leg to Lydd, followed by the accident flight of approximately one hour. Total block time since refuelling was 5.25 hours. Based on an assumed average consumption of 19 litres per hour at 75% power, the aircraft would have had about 50 litres remaining at the time of the accident, equating to roughly 2.5 hours of flight.
Examination
Borescope inspection of the main fuel tank found it free of debris. Evidence suggested that the engine had been starved of fuel, possibly by air entering the fuel system, but the cause of this could not be determined with any degree of certainty.