History of T56/501

Flight Engines

History of T56/501

Postby j79guy on Tue Jan 20, 2009 10:20 pm

Interesting engine this.
Started out as the T38 turboprop engine, designed in 1949 as a lightweight, high specific output engine. (Type-I engine) As all turbine designs at the time were in their infancy, there was a lot of corporate espionage, and cross pollination between manufacturers going on, as the dearth of good information and real experience with turbine engines led to a few innovative designs springing forth, which would quickly be copied and show up i a completely different engine line and manufacturer. Allison having enjoyed the position of selling as many piston aircraft engines they could possibly make during war time, and the subsequent contracts they picked up from GE to manufacture the early single stage centrifugal compressor turbojets, were flush with cash and wanted to scratch build their own turboprop engine line.
The T38 had a tremendous amount of great ideas incorporated, but for a few shortcomings. Mainly, fixed geometry compressor stators, and to a minor degree, external "flame tube" type combustors. Well, they certainly could not be looked down on for these tow less than stellar design details as everybody else were building their engines with the same two poor features.
Early flight trials were moderately successful, but the industry needed more power. Solution? bolt two T38s together onto a cojoining gearbox, and call it the T40!. It was a nightmare, and quickly died a natural death. Allison re-grouped, and did a re-design of the T38, using a couple new fangled ideas that seemed to be working for the competition. They added compressor bleed valves at the fourth and tenth stages of compressor, jacked up the overall compression ratio, and put the combustors within the outer engine case. Perfection. (Well, perfection in the late 1950's) They went on to sell several thousand in Military T56, and Commercial 501D guise. (Type-II engines.) Later major upgrades included incorporation of air cooling the first & second stage turbine nozzles, and first stage turbine blades. (Type-III engines.) Introduction of single crystal first stage turbine blades, improved cooling regimens, and honeycomb type gas path sealing led to the current Type-IV engines.

Some time ago I bought some "T56" overhaul tooling. What arrived had T40 stamped into each tool. I was dismayed at first, until I discovered that each and every tool fit the T56 engine I had perfectly. Close lineage or what?

Robin
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Re: History of T56/501

Postby TillamookTurbine on Wed Jan 21, 2009 10:06 pm

Robin:

Since you mention tooling; what amazes me as I view photos of your shop is the varied amount and quantity of tooling that you have.

Terry
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Re: History of T56/501

Postby j79guy on Fri Jan 23, 2009 12:07 pm

Price of entry, to effectively work on the engines.
Most of the tooling was made here, by our own machinists. If I happen to run across tooling at a good price, I'll pick it up. Otherwise we build it ourselves, often without any OEM blueprints to speak of.
The first Rolls Royce Olympus engine we overhauled, prior to being awarded the contract, I was asked; Can you overhaul Olympus engines?, "Yes I can". Do you have tooling and manuals? "No, and no." How can you do this work then? "Just watch me". Yes, we were given the contract, and we went on to successfully overhaul and test run the first Olympus unit outside of Rolls Royce/Rolls-Wood. This is the attitude we carry through on all aeroderivitive turbine units, we're just too dumb to know we cant do it.
More than once, I've had "spies" take pictures of my facilites from the road running adjacent to my GE shop. A couple months later, my customers will show me copies of the pictures that were taken as "evidence" of my inability to do the work we say we can, presented to them as part of the sales pitch against me by my competitors. We have a good laugh and carry on. Yes I know exactly who these "spies" are, and I'll get my digs back eventually.

Robin.
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