This might be taking liberties putting this in the “Flypast” forum, but as Tornado’s are finding their way into Museums, I hope you’ll not object.
Back in the old days, engines like the Avon,Sapphire, Conway, J-79 etc were built as one unit, given a life based on the fatigue life of the complete rotating bit, and were removed and scrapped when the engine reached that number of flying hours. Nowadays most engines are “Modular”. This means they are assembled from a number of self contained sub assemblies, each of which has it’s own “life”. When an engine goes unserviceable, can’t maintain thrust, or one of the modules reaches it’s life, it’s returned to a bay where it’s stripped down into it’s modules. These proceed independently through a repair/overhaul process. In the assembly area an engine is built up from a group of modules, which may or may not be the same bunch of modules it started out with. Piccie one is a cutaway of an RB.99 assembled, Piccie 2 is a diagram showing the breakdown of the modules.
If you’ve got any questions on this, I’ll try to answer them in later posts.
KeithMac
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By: Dazza - 3rd October 2002 at 19:27
RE: Modular Engines
Thanks for the info guys, its always far more revealing to hear from people with first hand experience than anything written in a book, obviously the material I read on the RB.199 was erroneous, so thanks for setting me straight on that one.:-)
Regards, Dazza.
By: keithmac - 3rd October 2002 at 18:56
RE: Modular Engines
I have to agree with Steve, I was part of the 4 man team which introduced the RB.199 into RAF service. The engine has always met with the spec to which is was designed. It has also been far more reliable than we ever expected. The amount of maintenance over-capacity is almost an embarrassment to me, as I made the initial recommendations for repair facilities, a lot of which we never needed after the first few years in service. Whichever way you look at it, the 199 has been a superb engine and has done everything we have asked of it. If we wanted to “tweek” the performance up a bit for combat, we could, but at the cost of turbine life. The new engines to which Steve refers have reverted to twin spool layouts, due to better computer designed compressor and turbines. You need to keep in mind that the original 199 series goes way back to the 1970’s, and the changes in computer technology since then have been staggering.
KeithMac
By: Bluebird Mike - 3rd October 2002 at 17:18
RE: Modular Engines
If the Tornado is whooshing about with down-rated engines, I’d love to see one that’s had a tune-up!!!
By: Steve Bond - 3rd October 2002 at 14:42
RE: Modular Engines
Don’t quite agree about the RB.199 being a disappointment. I managed an RB.199 engine bay for four years, and by and large the engine was pretty reliable, really only suffering from a few niggling little snags like persistent gearbox oil leaks.
Sixteen modules make up the RB.199, and yes it is a fairly complex beast being a three-spool engine. That was put right when the XG40 and later the EJ200 were developed from it, by going to a two-spool design for simplicity.
By: Dazza - 2nd October 2002 at 23:50
RE: Modular Engines
Good stuff as usual KeithMac, but from what I’ve read on the RB.199 it has never been the great success it should have been, despite providing high thrust for a compact powerplant it is my understanding that it does not meet its design requirements and has been down-rated thrust wise to increase engine life and reliability since introduction to service on the GR.1, is this still the case, or has the engine now been modified to operate at its original design thrust rating, not sure whether the Mk.104 variant installed on the F.3 suffered the same problems.
Regards, Dazza.
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October 2, 2002 at 9:04 pm