Newsletter 15
? Winter 2006
Updated on 9Dec2006
Aviation Heritage Project
Dunsfold Wings & Wheels
Female Angle
Flight Test from a Desk
Harrier News
Hawk News
Graduate Apprentices
Hawker People News
Hugh Merewether
  1924 - 2006, Test Pilot
  Flight Development
  Faster, Higher, Further
  Spinning With Hugh
JSF Progress
Sea Furies at Reno
Sea Harrier ZA195
Sea Hawk Recovered
Sir Sydney & Sir George
Sopwith & Bradshaw
Summer's Day at Dunsfold
Vulcan to the Skies
Published by the Hawker Association
for the Members.
Contents © Hawker Association

Editors note. I had planned for some time to put this piece, written by Eric Crabbe before his retirement in 1987, in the Winter Newsletter, when, quite by coincidence, I heard from Eric's wife, Pat, that Eric had died earlier this year.

Before working for HSA Eric had worked for Armstrong Whitworth, Glosters (where his father was Managing Director), Avros and Follands, as an aerodynamicist and flight test engineer, working on many types including the AW.52, the Gloster Meteor and E1/44, the Avro 707 and Vulcan, and the Folland Midge, Gnat and Gnat Trainer. When HSA took over Follands in 1964, Eric, already at Dunsfold with Follands' flight test department, transferred to the P.1127 programme...

Flight Testing From a Desk

top toptop toptop top top
After the conclusion of the Gnat spinning trials at Dunsfold I became involved in vectored thrust in the shape of the Hawker P.1127. I soon became engrossed in the wonders of short take-off (STO) performance measurement and in trying to non- dimensionalise the results. I was also introduced to the longitudinally destabilising effects of the Pegasus engine at high power. When I first measured it I thought that the aircraft should be very difficult to fly but Bill Bedford and Hugh Merewether did not report any problems, the bob weight in the longitudinal control circuit providing ample stick force per g. I was also concerned with rapid rolling trials. All the above testing was carried out using paper trace recorders, the reading of which was very long winded and tedious.

When the P.1154 was cancelled in 1954 there followed a short break from my direct association with aircraft when I worked with computers for two years with Benson-Lehner but returned to flight testing at Dunsfold in 1968 where the Harrier was undergoing development and clearance.

The first job I had on my return was to write reports on the handling aspects of the Harrier in eight Acceptance Standard configurations with various combinations of bombs, rockets and combat tanks. The surprising thing about it was the relatively small effect that stores had on the general handling characteristics. This proved to be case throughout the development of all variants.

Intentional spinning did not have to be demonstrated on the Harrier but we had to show that it could be recovered from an unintentional spin. Here we had the advantage of having the use of the Lille spinning tunnel prior to flight trials, and of having Hugh Merewether as the pilot for the majority of the trials. Little more need be said about Hugh's expertise as a pilot and his knowledge of spinning characteristics gained from his experience in the Hunter spinning programme.

The Harrier is very spin resistant and during tests it was found that there was a tendency for the engine to surge during spins. With the engine windmilling when shut down post-surge it was discovered that in a more sustained spin at higher incidence, a flatter spin, resulted. Hugh therefore chose to carry out the rest of the test programme with the HP cock closed and the engine windmilling. This says a lot for his courage, and his faith in the Pegasus relighting dependability; it did not let him down.

 VIFF, vectoring in forward flight, is a capability unique to the Harrier. The test programme added a bit of variety to the run-of-the-mill testing of the Harrier GRMk3.

The two seat Harrier TMk2 followed and one of the highlights, for me anyway, was a twenty-five hour programme on XW175 measuring fin loads during rapid rolling tests and rolling pull-outs in six different stores configurations. Duncan Simpson did most of the flying and it was amazing how well his 'seat of the pants' feeling tied up with the measured fin loads.

Another highlight was a sea trial carried out on G-VTOL, the Company demonstrator Harrier two seater, in 1972. The trial was flown from the Indian Navy carrier, INS Vikrant, off Cochin, to measure take-off performance in 30+ degree C temperatures. I'll never forget John Farley carrying out ten deck take-offs on the first day, and nine on the second, staying in the cockpit between flights. That's stamina for you. Twelve years later we would be testing the Sea Harrier ordered by the Indian Navy.

The story has not finished by any means, the Hawk and the Sea Harrier being my latest jobs. The Hawk first flew in 1974, with Duncan Simpson at the controls, very near the time of the SBAC Show at Farnborough, at which it appeared. The development programme went reasonably smoothly, the wing sprouting some vortex generators and a fence to cure handling problems at both the high and low speeds. Finally the Sea Harrier. I never imagined this would be the third aircraft I'd worked on which would see combat, in its case in the Falklands conflict.

It has been a real challenge to work with pilots of the calibre of Roly Falk, Jan Zurakovski, Ted Tennant, Dick Whittington, Bill Bedford, Hugh Merewether, Duncan Simpson and John Farley and Andy Jones, but one thing I regret is that I have never been able to participate in the actual flying; I was too old by the time I was working on two seaters. During all my years in flight testing I have worked closely with the A&AEE, Boscombe Down, and I must put on record my admiration for their unfailing consideration, and my praise for the high quality of 'A' Squadron pilots and Performance Division.

To sum it all up, things don't seem to change much in respect of the test methods but magnetic tape recorders have replaced the old paper trace machines. It is possible now to use the computer both for reading and plotting the magnetic tape data, and analysis programmes are available to calculate directly, for instance, aircraft stability derivatives and drag. So sophisticated computers do some of our work for us. I say some because if you're not very careful you find you're running out of files to put all the data in!

I think I have lived through the most exciting time in the history of the age of jet propelled aircraft, and wouldn't have missed any of it, and I feel especially proud of the achievements of all the firms for whom I have worked.

Editor's Post Script
At the time of his retirement in September 1987 Eric was in charge of analysis methods and test technique development at Dunsfold utilising the powerful computer systems and digital data recording equipment available to the flight test engineer. He died on 11th May, 2006.