While the PT-6 is indeed a strange creature, it is perhaps the most
successful of all turboshaft engines. The ease and low cost of maintenance
has made it ubiquitous. I would trust my life to one.
Bill Pearce
-----Original Message-----
From: Chris Trask
Sent: Saturday, November 19, 2011 3:37 PM
To: Olympus Camera Discussion
Cc: Olympus Camera Discussion
Subject: Re: [OM] IMG: An Unusual Airplane
>
> While evaluating my first Leica lens, an Elmar 50/3.5 from 1946, I came
> across this Air Tractor company-owned Sky Truck airplane which appeared
> to be fitted out with flight test gear in the rear cockpit. Developed
> from a large agricultural aircraft, the AT-802U has been used for
> firefighting and for close air support in developing countries. It is
> a BIG airplane.
>
Nice. Looks like it has a PT-6 engine, which is a strange contraption
in itself. It's mounted backwards with the intake in the rear. It does not
have a "real" turboshaft. There's one turbine section for the accessories
and to drive the compressor, and a separate section to drive the propeller
without a gearbox. When you start it up, you can hold the propeller
stationary. The Ayers Thrush uses them, as well as lots of commuter planes.
A very popular and reliable engine.
Interstingly, another aircraft that was converted to firefighting many
years ago was the Northrop YC-125A Raider, which was used very briefly in
Viet Nam before being turned over for fire jumper duty. Now, can you name
four (yes, four) other trimotors using radial engines? Three are obvious,
the fourth is rarer than the YC-125A. Only one remains.
Chris
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