Synopsis
The aircraft departed from Humberside Airport on an instructional flight and was being flown in clear air at medium level when radar contact was lost. Shortly afterwards it impacted the ground in a steep nose-down attitude at high speed which killed both pilots on board.
History of Flight
Three days before the accident, the company pilot flew the aircraft to Humberside Airport to undertake an instructional course with an FAA licensed instructor. Over the next two days, he completed four flights. Immediately before the accident flight, the two pilots briefed and booked out with ATC by telephone. The instructor told the air traffic assistant they intended to fly to the northwest before returning for approaches. The aircraft had been refuelled the previous evening with 120 US gallons, nearly full capacity. They took off at 1139 hrs after requesting permission to practise an engine failure after takeoff. Although no radio call confirmed the practice, the duty ATCO noticed a reduction in climb rate at about 300 ft agl before normal rate was restored two miles later. At 1141 hrs, radio contact with Humberside Radar was established, with the instructor stating intention to fly to the northwest climbing to 3,000 feet. Seven minutes later the instructor transmitted 'CLIMBING TO OPERATE BETWEEN THREE AND FIVE THOUSAND FEET'. Nothing further was heard. At 1157 hrs, radar contact was lost and the controller attempted radio contact without success. Eyewitnesses reported an aircraft crashing in the same area.
Radar Recordings
Radar heads at Claxby and Great Dun Fell recorded much of the flightpath. The aircraft flew west from Humberside Airport for 7 nm, turned north to the Humber estuary, performed an orbit at about 3,000 feet, then resumed a northerly track climbing to about 4,000 feet. Wind at altitude was westerly at 25 kt. After removing wind effect, the final leg showed airspeed accelerating from approximately 100 kt to 150 kt TAS when radar contact was lost. The last recorded altitude was 3,200 feet. A test flight established the radar base at approximately 700 feet altitude. The next radar sweep was eight seconds later; if the aircraft had descended below radar cover, it would have averaged a rate of descent over 18,000 feet per minute.
Witness Information
Several witnesses at close range heard engine noise described as 'normal' with little variation, then an increase. The aircraft was seen exiting the cloud base in an approximately 45° nose-down attitude, wings-level, travelling 'extremely quickly'. About 5 seconds elapsed until impact. Only one witness reported any sign of attempted recovery. Nothing fell from the aircraft and no pre-impact smoke or fire was observed. The evening before, the company pilot told his partner he was learning a lot and enjoying the experience, and that his instructor said he would have no problem passing his tests. He described a stall demonstration that was 'almost nose up' during which they entered cloud.
Meteorology
An aftercast from the Meteorological Office showed a light to moderate moist westerly airflow. Humberside Airport weather at 1150 hrs: wind 220°/10 kt, visibility 3,000 metres in light rain, broken cloud base at 1,000 feet. An airborne message reported cloud tops at 2,400 feet; the commander advised company operations that cloud tops were at 2,000 feet.
Pathology
Toxicological tests found no evidence of factors in either pilot that may have contributed to the cause of this accident.
FAA CPL/IR Training
The instructor operated a flying school training for JAR PPL and FAA CPL/IR. The school was registered with JAA for PPL training but did not hold FTO status. Under FARs, FAA commercial licence training can be conducted in the UK without school approval if the instructor holds a current FAA Flight Instructor Certificate and operates under FAR Part 61. The instructor renewed his Flight Instructor Certificate on the previous two occasions by completing a ground-based Flight Instructor Refresher Course in the USA. The FAA Advisory Circular No. 61-67C (25 Sep 2000) states that stall demonstrations should be conducted at sufficient altitude to enable recovery by 3,000 feet agl in multi-engine aircraft.
Aircraft Description
G-OGTX was a Cessna T310R with two turbocharged, fuel injected, horizontally opposed six-cylinder engines each with a hydraulically actuated three-bladed constant speed, fully feathering propeller. Fuel was stored in wing tip tanks and bag tanks. It had six seats; the main cabin door was on the right side above the wing adjacent to the co-pilot's seat. The pilot's side window included an integrally mounted foul weather window (Direct Vision window) that could be removed in an emergency via a red pull ring.
Wreckage Examination
The aircraft impacted the ground at high speed in a nose-down attitude of approximately 45°, on a heading of about 110°M. The impact crater contained pieces from left and right wing tip tanks and debris from both wings. A strong smell of fuel and some liquid with the visual appearance of fuel was evident at the bottom of the crater; the wreckage had not burnt. The aircraft broke up on impact, with debris thrown forward up to 130 metres from the crater. The main cabin door latch mechanism was closed and locked. Pieces of transparency from the emergency exit window, including the foul weather window, were found between 40 and 190 metres from the impact crater, indicating they detached prior to impact. The window surround, with pins still extended, was found in the main debris field. It is considered probable that airflow entering via the periphery of the foul weather window during the final high-speed descent contributed to the detachment.