New Powerplant

Time to weigh in with some facts.

First, for those who are skeptical of the jet Silent's
self-launch capabilities, I can assure you that I routinely
launch from my home airport at 6200' MSL. Ask anyone
who saw the demonstration during the 1-26 Nationals
this year. Granted, on hot days it does use some runway.
I have performed jet-launched aerobatic routines
at several airshows this summer, including full aerobatic
routines beginning at less than 1000'.

Noise has not been a problem. In fact, in the airshow
business, where noise equals dollars, the jets are
a bit too quiet. At 1000', they are MUCH less noisy
than any towplane. In fact, when I'm on a normal downwind,
the guys on the ground can't distinguish the jet noise
from the noise of the highway about 3 miles from the
airport.

TBO times are currently low, but an overhaul costs
about $300 (typically just inspection and new bearings).
These are NOT 'throwaway' engines. The engines can
be removed in about 15 minutes, and overnight shipped
back to the factory in a breadbox. My overhauls cost
less than the shipping for most powerplants. TBO times
are getting better as the engines develop. I predict
TBO times in the 100-200 hour range within a few years,
and over 1000 hours in the not-too-distant future.

Fuel burn is high, but for the brief time required
for a normal glider launch, tolerable. I carry 10
gallons, good for over 30 minutes of climb, or more
than 1 hour at 70 knot cruise. (I climb about 500
ft/minute at sea level)

There are other engines 'under development' with better
predicted performance numbers than the AMT-USA engines.
Some of these are garage-shop projects, some (including
one being advertised by a prominent US sailplane dealer)
are probably currently nothing more than plans and
a mockup. I do not know of any other microjet engine
currently available that has the performance, reliability
and factory support required for regular service in
a manned aircraft.

I know of several university projects in which a jet
assisted sailplane has been flown. Typically, these
have managed to barely sustain level flight under power,
and are a far cry from a serviceable aircraft.

Jet engines are not a 'perfect' answer. Like the early
military jets, there are still issues to be resolved.
But, in the next few years, microjets will definitely
play an important role in all aspects of sport aviation.

Videos of the jet sailplane, Salto sailplane and biplane
are available on my website at www.silentwingsairshows.com

Bob Carlton











At 01:12 30 August 2005, M B wrote:
The biggest issue against these engines is the TBO.
The AMT 45lbs engines are 25-50 hours for TBO.
Not bad in 20 minute spurts, but 160 launches
for $4000 just in engine costs ain't chicken feed.
$25 per launch? Good, but not fantastic. And for
2 of them
maybe a bit more... Still, glider self-launch seems

like a much better GA application than many other
options...

At 21:48 29 August 2005, Titoa wrote:
I had a look at the microjet engine. With 65 Lb of
thrust, and with 36
cm long, 16 cm diameter, a 400 Kg plane should be able
to climb at 1,3
m/s sustained (25 Lb for the aero drag, rest for climbing).
Going to
1000 m would take just 12 mins and 11 Kg of fuel. I
ignore the cost of
fuel, but at 1 $ /kg, that makes for cheap tows to
offset the cost of
the engine.

Next, could the exhaust temperature be solved by embedding
the tiny
engine behind the pilot and letting the exhaust out
throug some
openning in the aft taper of the fuselage, and well
below the tail
planes. This would however need some adjustable intake
port in the
fuselage. But in all cases it should all be much simpler
that folding
out a propeller with or without a piston engine....
.


Mark J. Boyd