Alternative engines

[Joe Piche]

Howard Wilkinson wrote:
> 
> Joe:
>     you seem to be somewhat well versed in the matter of turbine
> engines.  I'm curious about one thing here.  Several folks in the
> experimental aviation community have tried to use APU engines for
> power in light aircraft and had poor luck..... engine troubles.  I
> have a theory on this.  From what little I can gather about it, and

APU engines are designed to do 2 things. Create bleed air (compressor
section discharge), and run a generator. Your right, they are governed
to a constant speed. The APU units I've seen, and operated, have simple
off -- start -- on controls. I don't think they'd be very good for much
with out serious mod's to the FCU.

In fact, all jet engines that I'm aware of, are governed. Just the fact
that the speed is controllable.

>     My thinking is that the correct way to use one of these is to have
> a controllable prop and operate at a constant RPM.... forget about
> controlling RPM.... let the system operate as it was originally
> intended and use the stock fuel control / governor system.  I strongly
> suspect that the problems people have had originated from changing
> RPM.

A constant speed prop might do the trick. Can't say for sure. Depends if
the engine can put out enough power to successfully accelerate the a/c
at a decent rate when the prop is in coarse pitch. Getting the oil
pressures correct for prop control unit could be a treat too.

I've heard of a company in the US (don't know the name), that sells
converted jet turbine starter units (a mini gas turbine). Might be the
ticket.

Joe