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LEM
12th Dec 2003, 20:57
Example: JT8D-15 and -17

Are these engines physically identical?

The -17 is more powerful, but exactly why?

If they are identical in shape, are the materials different?

Is the FCU the same?

Is the -17 simply more stressed, at the expense of its duration?



Appreciate any light...

lomapaseo
12th Dec 2003, 21:58
Typically you take a basic engine JT8D of some model (-15) configured for a specifica aircraft installation (Boeing) and at the request of a customer (Boeing etal) you uprate it for more performance by minor changes in the fuel control logic.

This increased performance typically raises rotor speed, temperature and pressure.

In repsonse to an increase in rotor speed, you might have to strenthen a specific rotor stage or two or reduce the life of a rotor stage to force it to be replaced earlier.

The more pronounced effect on the engine parts is typically felt in the front stages of the turbine blades. These often get upgraded in design by either new materials (if available) or more commonly by ducting some more cooling air to them.

Thus the change effect can be in some or all of these areas. About the only way to find out is to ask the seller or to reviewed the specific parts list for the models.