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Aviation History
1986
1986 - 1585.PDF
DEFENCE Hawk 200 crash—G-loc suspected DUNSFOLD British Aerospace's single- seat Hawk 200 prototype crashed at its Dunsfold base on July 2. Deputy chief test pilot Jim Hawkins was killed in the accident. Although the accident is still under investigation and a full accident report is not expected for some months, first indications are that g-induced loss of consciousness (G-loc) is suspected as the primary cause of the accident. The Hawk 200 had completed over 27hr of flying in 28 sorties and Jim Hawkins had practised his display routine on many occasions. To demonstrate the Hawk 200's agility and abundance of power, Hawkins had worked up two routines: a flat bad- weather display highlighting mainly the sustained turn rate, and a good-weather display utilising the vertical. The latter sequence pro ceeded normally until about half-way through the display when the aircraft behaved erratically. The planned sequence was for a sustained high-speed, low-level right- hand turn of 30 to 40sec duration, (The Hawk 200 had demonstrated its ability to maintain 8g/300kt indefi nitely), rolling out of the turn to run from west to east along Dunsfold's main runway before an abrupt rotation into a vertical zoom climb. (This demonstrated that the Hawk's low induced drag and extra thrust did not let the speed bleed off in sustained high g turns.) At 1 500ft the Hawk was to roll | right to head north, to position for the next manoeuvre, while continuing to climb vertically. At 3,000 to 3,500ft the sequence called for a gentle pull back over the top of a lazy loop to head south, inverted with the nose just below the horizon. From this position, the Hawk was to make a gentle roll right continuing around in a lazy Derry turn until the aircraft was in a 60° left bank to spiral down through a 270° heading change and run back across the airfield from east to west in a high-speed run. What happened on the last FLIGHT INTERNATIONAL, 12 July 1986 Jim Hawkins flight is that the long- duration tight turn was completed, as was the pull and zoom and the I vertical roll for positioning. The Hawk 200 then pitched slowly over the top to continue inverted. At this point the aircraft made several erratic rolls of 10° to 15° both left and right. One pilot commented: "It looks as if no one is flying it". The Hawk continued south, inverted, with the dive becoming steeper and steeper before disappearing from the view of observers at Dunsfold behind tall trees some 1\ miles distant. The Hawk impacted wings level at about 300kt and had, by then, completed a loop and was erect but still in a 25° dive and heading north, back towards the airfield. As far as can be ascertained at this early stage, there was no problem with the aircraft, engine, or systems. Had the ailerons jammed, and Hawkins was unable to roll the aircraft upright after the climb, then he had enough height (about 3,000ft when the normal sequence was broken off) to pull or push to the upright, or to use rudder. But apart from the erratic twitches in roll, and the steepening of the dive the Hawk was not seen to do anything. Although Dunsfold air traf fic's tape recording of radio calls had not been replayed before we went to press, the tower controllers do not recall any transmissions from Hawkins after his acknow ledgement of take-off clear ance, which is normal procedure for a display. Initial examination of the ejection seat shows that ejection was not initiated. The shoulder harness reel-in initiator cartridges and the cockpit miniature detonating cord initiator cartridges had not fired, and these are the first in the seat-firing sequence. The tailplane actuator rod was found to be fully extended, in the stick back, nose up posi tion. Although the evidence is circumstantial, it points heav ily towards G-loc. Centrifuge tests have shown that very sudden application of high g, as in Hawkins' pull to the zoom climb, causes subjects to go unconscious some several seconds later. This phenom enon should not be confused with grey out/black out. With G-loc there are no warning symptoms such as tunnel vision, the unconscious state is both total and immediate and can last for as long as 30sec. When unconscious, the centrifuge subjects have been observed to make random arm, leg, and head move ments. When they awake these uncontrolled limb movements continue, with rapid eye movements, severe disorientation, and lack of awareness. These symptoms seem to fit the Hawk's seem ingly random twitches in roll during its dive and there is evidence that Hawkins might have been coming around and starting to pull out of the dive, hence the tailplane position, when the Hawk hit the ground. Several previous accidents have been attributed to G-loc, including the two very similar fatal accidents to the proto type Northrop F-20 Tiger- sharks and several General Dynamics F-16 Fighting Falcon accidents. Research into the phenomenon is underway, and air force aviation medicine training courses now include expla nations of G-loc. Meanwhile British Aero space is adamant that the Hawk 200 project will continue and is planning to build a second aircraft. If the company works around the clock, the second Hawk 200 could be flying before the Paris Air Show next May. 11
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