The account below was originally published on the RAF Church Fenton website together with other accounts from the test piloting career of Dennis Witham. I have copied it here with permission from the site's webmaster. Dennis Witham was in the right hand seat when Rolls-Royce Chief Test Pilot Cliff Rogers flew G-AXLR for the first time. After the rebirth of Rolls-Royce in 1971 the VC10 test bed moved to Bristol and Dennis took over as the RB211 project Chief Test Pilot. He was flying the test bed when it got into trouble with the RB211's thrust reverser. Read on for his account from this day and some photos from the day of the first test flight.
"ON THE MORNING OF 7 AUGUST 1972, THE WEATHER WAS FINE with fair-weather cumulus cloud drifting across Bristol Filton airfield on a light westerly breeze. The flight-test crew of two pilots, flight engineer and four flight-test engineers boarded the Company’s VC10/RB211 flying testbed G-AXLR to carry out a programme of engine performance measurement tests at various altitudes and airspeeds. It was also the first flight with a new undercowl-pressure switch designed to keep the RB211 fan cowl locks in place to prevent reverse thrust deployment in flight.
Taking off to the west over the Severn Estuary, gear and flaps were retracted and the aeroplane was accelerating to climb speed when, at 3000 feet, the reverser unlock warning light illuminated on the pilot’s instrument panel. Throttling back to reduce airspeed the captain called for an instrumentation check and visual inspection of the RB211 through the rear cabin windows. Everything appeared normal and, after some discussion among the crew, it was decided to continue the flight programme. The aeroplane was carrying fuel for a five-hour flight and to abort at this early stage would mean dumping several hundred gallons of fuel into the Bristol Channel to reduce to an acceptable landing weight on Filtons 7000 ft runway. The aeroplane resumed the climb and, almost immediately, the reverser-unlock warning light went out.
At 20,000 ft the first performance measurement run at 250 knots was completed and the second run at 300 knots was being set up when there was a severe jolt and the aeroplane yawed and rolled violently to the left. The RB211 power lever was immediately slammed back to the shut-off position and at the same time the reverser-unlock warning light illuminated. The Conways were also throttled back, to reduce the huge asymmetric thrust condition, and the aeroplane was brought back on an even keel. Airspeed was decaying at an alarming rate and at 200 knots there was no alternative but to set up a descent. The initial rate of descent was 2500 feet per minute, even when the Conways power was restored to max continuous and the aeroplane trimmed.
An instrumentation and visual check confirmed that the RB211 fan cowl was in the reverse thrust position and the engine was windmilling. It says much for the VC10's flying qualities that she was controllable under the strong asymmetric force created by the RB211 windmilling reverse drag and both Conways at max continuous thrust. Thank heavens for rear fuselage-mounted engines! With the aeroplane grossly overweight for the predicament she was in, fuel dumping at maximum rate was initiated, even though the aeroplane was not in a designated dumping zone. With unspoken apologies to the residents of Wiltshire and Somerset, Air Traffic Control at Filton was informed of the emergency as the aeroplane headed for the Bristol Channel. Calculations of rate of descent and rate of fuel dumping revealed there was little more than ten minutes remaining before the aeroplane hit the ground, or water. As the descent progressed and the weight decreased, it became clear that the Bristol Channel was within reach. The crew was ordered to check their sea survival equipment and ditching drill. At 5000 feet over the Channel the rate of descent was less than 1000 feet per minute and the aeroplane was eased into level flight, allowing her to slow down until, at 3000 feet, she flew level with acceptable load on the flying controls.
Setting course for Filton airfield, fuel-dumping was stopped at the coastline and a detailed briefing was given on how the approach and landing would be carried out. Landing a VC10 in this configuration had never been done before and it would be one attempt only. There would not be enough power to make a go-round. Filton ATC had made the preparations. The circuit was clear of other aircraft and the emergency services were standing by. A wider- than-normal circuit was flown, flaps and gear were lowered at airspeeds 10 to 20 knots above normal. The landing run was almost an anti-climax. A post mortem revealed that the under-cowl pressure switch was sensing the wrong pressure."
Source: RAF Church Fenton website - A Test Pilot Remembers with thanks to David Mason