New Powerplant

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The August issue of AOPA PILOT reports a "tiny jet engine" is being
developed with 150 lbs of thrust. Its 15" long, 8.6" in diameter and
weighs 19 lbs. I wonder what it costs? This sounds like a great power
to weight ratio.

[Pete S]

> wrote in message
oups.com...
> The August issue of AOPA PILOT reports a "tiny jet engine" is being
> developed with 150 lbs of thrust. Its 15" long, 8.6" in diameter and
> weighs 19 lbs. I wonder what it costs? This sounds like a great power
> to weight ratio.
>

It is, but what you gain from the engine you loose from the amount of fuel
yoo have to carry. Take a look at www.microjeteng.com for what's available
now. I seem to recollect that a video was published on the internet of a
glass glider with a pop out pod with two jets on it.

Peter

[Martin Gregorie]

On Thu, 25 Aug 2005 12:40:30 -0700, richard.kiray wrote:

> The August issue of AOPA PILOT reports a "tiny jet engine" is being
> developed with 150 lbs of thrust. Its 15" long, 8.6" in diameter and
> weighs 19 lbs. I wonder what it costs? This sounds like a great power
> to weight ratio.
>
I don't think power/weight is very significant for our use. Thrust/drag
ratio is a lot more use. Calculate that for your glider at typical
inter-thermal speeds, double it and that's probably all the thrust you'd
need. I did a rough calculation for an SZD Junior at 65 kts and got about
22kg of drag, Double it and you're looking at 40kg, 88 lbs thrust.

Fuel consumption is also important: a turbojet at sensible glider speeds
will be thirsty. Maybe you just carry jet fuel instead of water ballast to
bring you up to Mtow?

Finally, make sure the engine management system is as good as those on RC
models because this means that the engine will take care of its start
sequence all by itself: if you're low you don't want to be paying
attention to a manual start sequence.

Its all been done anyway: a German University project flew a Ventus on a
single 35 lb st. engine (climb rate .001 m/sec IIRC) and there is/was a
glider on the US display circuit with a pair of 35 lb st. engines: the
implication was that it was self launching from a sealed run.

--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Mike the Strike]

Snip
>
> Its all been done anyway: a German University project flew a Ventus on a
> single 35 lb st. engine (climb rate .001 m/sec IIRC) and there is/was a
> glider on the US display circuit with a pair of 35 lb st. engines: the
> implication was that it was self launching from a sealed run.

It's a not-so-silent Silent sailplane, based in Albuquerque:

http://www.silentwingsairshows.com/jet.html

Yes, it really does self-launch and is no worse than some motor gliders
I've seen. Personally, I'd like a bit more thrust if I were going to
self-launch.

Mike

[Bill Daniels]

"Pete S" > wrote in message
...
>
> > wrote in message
> oups.com...
> > The August issue of AOPA PILOT reports a "tiny jet engine" is being
> > developed with 150 lbs of thrust. Its 15" long, 8.6" in diameter and
> > weighs 19 lbs. I wonder what it costs? This sounds like a great power
> > to weight ratio.
> >
>
> It is, but what you gain from the engine you loose from the amount of fuel
> yoo have to carry. Take a look at www.microjeteng.com for what's available
> now. I seem to recollect that a video was published on the internet of a
> glass glider with a pop out pod with two jets on it.
>
> Peter
>
>

Originally, I thought the horrible specific fuel consumption would make
these 'dog whistles' unsuitable for glider use.

On second thought, the residual weight after all the fuel is burned is much
less than a piston engine and propeller. The extend/stow mechanism is much
simpler as well. If they were used only for self launch and the entire fuel
supply were to be consumed in that launch, the idea has merit.

One worrisome issue is the temperatures of the tail surfaces that are in
contact with the jet exhaust. Bob Carlson told me that the fin on his jet
"Silent" reached 140F during the engine run even with two small turbojets
canted slightly outward to spare the fin. I suppose it's possible to choose
resins and curing processes that would make those fin temperatures
tolerable.

I have to admit that I like Bob Carlson's idea that if the ballast tanks
were to be filled with Jet A instead of water and then when in trouble just
start the jet and fly home instead of dumping ballast. My Nimbus would hold
75 gallons of Jet A which is several hours of engine run.

Bill Daniels

[01-- Zero One]

140 degrees? Hell, sounds like Uvalde in August. Or Phoenix. I
wouldn't worry too much about it.



Larry




"Bill Daniels" > wrote in message
:

> "Pete S" > wrote in message
> ...
> >
> > > wrote in message
> > oups.com...
> > > The August issue of AOPA PILOT reports a "tiny jet engine" is being
> > > developed with 150 lbs of thrust. Its 15" long, 8.6" in diameter and
> > > weighs 19 lbs. I wonder what it costs? This sounds like a great power
> > > to weight ratio.
> > >
> >
> > It is, but what you gain from the engine you loose from the amount of fuel
> > yoo have to carry. Take a look at www.microjeteng.com for what's available
> > now. I seem to recollect that a video was published on the internet of a
> > glass glider with a pop out pod with two jets on it.
> >
> > Peter
> >
> >
>
> Originally, I thought the horrible specific fuel consumption would make
> these 'dog whistles' unsuitable for glider use.
>
> On second thought, the residual weight after all the fuel is burned is much
> less than a piston engine and propeller. The extend/stow mechanism is much
> simpler as well. If they were used only for self launch and the entire fuel
> supply were to be consumed in that launch, the idea has merit.
>
> One worrisome issue is the temperatures of the tail surfaces that are in
> contact with the jet exhaust. Bob Carlson told me that the fin on his jet
> "Silent" reached 140F during the engine run even with two small turbojets
> canted slightly outward to spare the fin. I suppose it's possible to choose
> resins and curing processes that would make those fin temperatures
> tolerable.
>
> I have to admit that I like Bob Carlson's idea that if the ballast tanks
> were to be filled with Jet A instead of water and then when in trouble just
> start the jet and fly home instead of dumping ballast. My Nimbus would hold
> 75 gallons of Jet A which is several hours of engine run.
>
> Bill Daniels

[titoa]

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.... .

[Stefan]

I've seen the video of the not so silent wings. Now how long do you
think it would last until your neighbours would shut down the
gliderport? At mine, I guess about two weeks maximum.

Stefan

[M B]

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

[nimbusgb]

It strikes me that these units are much more suitable for use as
sustainers rathe than self launchers. You may only use them a few times
in a season saving on engine rebuild costs, their drag profile is
significantly better than a prop and two stroke engine assembly,
the'yre lighter than an IC engine. Lots of good reasons.

[Bob C]

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
>
>
>

[M B]

I was unaware that overhauls were so very inexpensive.
I assumed the worst case, and am happy
this is unneccessary.

Thank you Bob for setting the record straight here.
Plus, thank you for doing this AT ALL.
I think you are definitely raising awareness of this
technology,
and have completely followed through on FAA
issues and have a better handle on this technology

as it applies to sailplanes than anyone else I have
encountered.

My only deep regret is that your airshow performances

are not scheduled in Calif. But I am glad many others
in the soaring community have had the privilege to

see you perform.

Your logged hours and experience go a LONG way towards
proving the viability of this technology. Thank you!

At 03:12 31 August 2005, Bob C wrote:
>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
>>
>>
>>
>
>
>
>
Mark J. Boyd

[Andreas Maurer]

On 31 Aug 2005 03:49:38 GMT, M B >
wrote:

>I was unaware that overhauls were so very inexpensive.
>I assumed the worst case, and am happy
>this is unneccessary.

Shall we bet that the overhaul is going to become expensive once the
engine is certified as a powerplant for certified gliders? ;)




Bye
Andreas