As many of the avid followers of the ThrustSSC project will already know, there were a number of variants of the Spey turbofan jet engine built by Rolls Royce, with the majority of the Royal Air Force's Phantom aircraft being fitted with the standard Spey 202, which produces some 20,000lbs of thrust on maximum reheat. Other variants include the Spey 203 and the Spey 205. The 203 was fitted to naval Phantoms, the difference being the faster light-up for the afterburner - to cover the event of an aborted landing on an aircraft carrier. The 205 is the version of most interest to the ThrustSSC Team: fitted with a turbine made from what the metallurgists call a "single-crystal" of metal, these were designed to give longer service life - although they can be tuned instead to run at a higher exhaust temperature, and the higher the exhaust temperature of a jet engine, the greater the power produced!
Although they were never fitted to Phantoms in active service, a number of the Spey 205s were built, and the ThrustSSC team have been fortunate enough to acquire a working pair to go with their two Spey 202s. The 202s have already been tested, and are ready to be fitted to the car for test runs on the runway at DRA, Farnborough, and in Jafr Desert, Jordan - now it was time to try out the 205s!
Just across the road from the Defence Research Agency's Farnborough facility is their Pyestock site, including a fully operational test bed which was more than capable of handling a military Spey with full afterburner. DRA Pyestock generously offered to test and balance the Thrust SSC team's 205s for them - as well as checking the engines' health, balancing is crucial to ensure that the pair produce the same amount of thrust at all settings - an imbalance in power from the two sides of the car could have disastrous consequences.
Starting on Monday 1st July the staff at DRA, Pyestock, set about their work, led by Graham Stokes, and observed by Steve Wiltshire and Al Harkness of the ThrustSSC Engine Team. Starting each engine at idle, they gradually increased the throttle as the Spey strained against the mountings of the test bed. An initial problem with a fuel leak on one engine was soon cured, and slowly raising the power until the afterburners lit with a roar, they took both of the Spey 205s up to their maximum output of 25,000lbs of thrust - equivalent to 55,000 horsepower each.
For someone who has never before seen an afterburning military jet engine on full power at close quarters, the sheer power of the sight was quite extraordinary. The test team, however, were used to the sight and sound of a long cone of flames erupting from the end of an engine, and quietly continued their work taking measurements and monitoring readings. Both ran satisfactorily, and ThrustSSC project leader Richard Noble was elated: "We now have four good engines!" he said, pointing out that the 205s have 25% more power than the standard Spey 202s.
If you have never heard a jet engine under test before, we did manage to record some audio for you. As always it is available in WAV and Real Audio forms:
More information about jet engines, and in particular the Rolls-Royce Spey, is available in our Engineering section.
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