On 11 Jan 2004 14:39:20 -0700, (Mark James Boyd)
wrote:

In article ,
Mike Borgelt wrote:
On Sun, 11 Jan 2004 09:40:25 -0800, Eric Greenwell
wrote:



I'm waiting until they have a chance to put that motor in the SparrowHawk...

Take a look at the movie clip of the Silent IN with the Jet engines. I
ran some numbers on the engines over the weekend and I'm convinced
I've seen the future of soaring.

Mike Borgelt

I've come to much the same conclusion as Mike. I'd use a single
more powerful turbine (maybe the 1500) instead of 2, but
the numbers seem to work for even fairly short fields.

The heat on the tail scares me though. Hmmm...how do we
get rid of the glider tail?


The guys with the Silent don't seem to have a problem with the heat on
the tail - the two AMT 450 turbines seem to be mounted parallel to the
centerline. If this still worries you a V tail as on HP gliders or the
Salto is the easy answer.

I first thought of using the AMT1500 but when you do the numbers two
AMT450s (and soon the XP versions with about 10% more thrust) are
quite adequate for a 400kg glider. 50 feet at 500m takeoff run under
standard day sea level conditions seems doable, over 500 fpm rate of
climb at about 90 knots, single engine out climb of close to 200fpm at
70 knots. It makes a pretty good sustainer. (A real "turbo"!) Fuel
consumption on one engine is about 0.5kg/min , two is 1kg/min. Given
that a 2000 foot launch will only take about 4 minutes it is about as
fuel efficient as a launch behind a Pawnee.

Imagine self launcher with engine out capability and a decent climb
speed where you have significant energy for manouever even if both
engines fail!

Don't worry about ducting - extend the engine(s) on a short pylon.
They weigh so little and don't vibrate that this will be a very
lightweight structure, easy to extend and retract, solves any local
structural heat problems and the hole in the glider is so small, that
there will be minimal structural reinforcement required. The AMT 450
is 5.1" diameter and 10.7" long and weighs about 2.4kg (5 pounds or
so).

Great for motorising motorless gliders as the weight in the fuselage
is minimal. Convert part of the water tanks/bags for jet
fuel.60Kg(75liters) will give you one hour.

Now look at a Sparrowhawk

70kg empty

add say 10 kg for 1 x AMT450XP pylon and structural reinforcing

30 kg for 1 hours fuel.

add typical say 100 kg for pilot and chute etc

Only 210Kg!

One AMT 450 will self launch this adequately.
Two smaller engines may still be optimum for slightly increased thrust
and engine out capability.

Hope the Windward Performance guys have a plan to increase production
because if this works they might be swamped by customers.


These small turbines are still being developed - they will get better.
Engine pressure ratios are still only 4:1 or so, fuel consumption can
be improved.

Mike Borgelt