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
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...
Testing From a Desk
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
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.
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
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,