Dear AREN Gang:

Rotary v. Gas Turbine

So now, they are going to put a gas turbine engine into that most
bread-and-butter of airplanes, the Cessna 206.

I have posted some information about this, as well as links, below.

Of course, you know me: I go with the rotary, But! how do you members of
the board compare and contrast this gas-turbine installation with the
rotary?  The good and the bad?

Curiously yours,

Les Nordman :-)

AVWeb has published this:

Soloy Receives FAA Certification For Turbine Cessna 206
http://www.avweb.com/eletter/archives/bizav/1245-full.html#199126

Soloy Aviation Solutions, of Olympia, Wash., received FAA certification
on Oct. 28 for its Soloy 206 Turbine Mk II, a turbine version of the
piston-powered Cessna 206H. Powered by the Rolls Royce 250-B17F/2
turbine engine, the Mk II provides an increase of 110 hp over the
standard Cessna 206H, Soloy said this week. With the turbine conversion
paired with a Hartzell three-bladed prop, the airplane can carry more
weight, fly faster and operate in high and hot conditions. The
performance also improves the airplane's STOL performance, especially in
its amphibious configuration, Soloy said. "The Mk II is the perfect
platform for vast number of applications, from law enforcement to
adventurous backcountry operations," said Dave Stauffer, president of
Soloy Aviation Solutions. "The lighter turbine engine increases the
power while reducing the basic empty weight by approximately 150 pounds."

The aircraft can climb at 2,460 fpm at sea level, cruise at 20,000 feet
at 213 ktas, carry 775 pounds with full fuel, and has a range of about
550 nm, the company said. The Mk II is initially offered in four
configurations, for law enforcement, skydiving, amphibious flight and
commercial/private operations. Soloy has started accepting orders and
plans to deliver the first aircraft later this month. The aircraft will
be on display this week at the AOPA Expo in San Jose, Calif.

Rolls-Royce publishes a description of the engine here:
http://www.rolls-royce.com/defence_aerospace/products/tactical/model250/desc.jsp

Description

"The Model 250 Series II turboprop engines are of two-shaft modular
design featuring four to six-stage axial and single-stage centrifugal
compressors, a two-stage LP turbine, two-stage HP turbine with a
hydromechanical fuel control system, and a gearbox with 2,800rpm output.
Compressed air is routed to the aft end of the engine for combustion,
with exhaust gases exiting upward from the middle of the engine.

"Developed from the famous Model 250 turboshaft, the first 317shp Model
250-B15 turboprop has spawned a family of highly successful derivatives,
culminating in today's 450shp Model 250-B17F.

"The Model 250 turboprop has found popularity due to its small size and
high power-to-weight ratio, which make it ideal for turbine conversions
of existing piston-engined designs."

Technical data
http://www.rolls-royce.com/defence_aerospace/downloads/tactical/model250_turboprop.pdf

Engine Model 250-B17F
Power (shp)  450
Bypass ratio  N/A
Pressure ratio  7.9
Length (in)  45
Diameter (in)  19.4
Basic weight (lb) 205
Compressor  4 (Axial) 1 (Centrifugal)
Turbine  2HP, 2

© Rolls-Royce plc 2004

Small turbines are gas hogs. The BSFC is .65 or above.
A rotary is about .47.
A turbo compound rotary may be as low as .4 or below.
A p-port four rotor would easily put out 450 HP NA.

Paul Lamar


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