Capt.Doug wrote:
"Bret Ludwig" wrote in message There are two basic "families" of PT6
engines ....
Most twins are not really safe to to do
that with considering the dismal single engine performance and lack of
single lever power control (which coupled with their 1950s panels means
they desperately need a F/O or F/E in the right seat).

Apples to oranges- most twins equipped with PT-6s have decent single-engine
performance, and decent safety records.

I agree. The recips are the problem. The turbines have effectively
single lever power control, and surplus power at low altitude.
However, the insurers will insure Dennis the Doctor in a 414 but not a
King Air....ass-backwards.

Turbines are simpler to fly, and probably are cheaper to build per
horsepower than the LyCon engines. CNC machining and lowered high
energy metals prices reduced the production costs considerably, but the
prices didn't come down. They have in fact gone up at a higher rate
than inflation-the PT-6 has been in production since JFK was president.
The TBO has gone up and power and BSFC have come down, true. But the
profit margins are phenomenal now, and certainly weren't lean then-and
when it was designed it specifically was announced that it was made as
simple as possible so as to compete with the growing flat engines and
the radials which were still available new. I have heard numbers
between $12 and $20 thousand as production costs on these today. P&WC
is very coy with pricing but I don't think Joe Average can get a new in
crate PT6 for less than $500K today. (ST6s are available for less but
you can't get a prop drive on the front.)


The former Allison 250 series of engines is also a fair powerplant
especially in the Soloy remote redrive configuration with less fuel
burn, less weight, but is not so elegant or simple.

The C-250 series never caught on for fixed wing applications. There must be
a reason (says the former NOMAD N-22 driver).

Too expensive. The turbine Maule is $400K, the recip $100K.


The Garrett 331 is
a piece of ****, but if cheap enough I'd rather fly behind one of those
than a Lycoming, and its noise would rally the troops on the front of a
mini-warbird or aerobatic biplane, wouldn't it?

Fighting words to me. I have 5000 hours behind -331s. They are dependable
and have lower BSFCs compared to PT-6s.


The 331 Garrett takes a colossal amount of power to start (and has
only electric, not air impingement or cartridge start), is extremely
loud, and is not significantly cheaper than the PT-6. The PT-6 is
almost perfect, except it has grown in power and price like Topsy. I
had hoped the ex-WarPac nations would undercut P&WC and force their
margins (which are phenomenal!) down, but they aren't too smart at
business.

Single shaft turbines just don't make engineering sense for smaller
applications. I don't think Garrett has ever found much non-aviation
use for the 331 whereas the ST6 (the aeroderivative PT6 non-propulsion
engine) has been a phenomenal seller, relatively speaking.