Re: gliders with Jet engines

[Eric Greenwell]

In article >,
says...
> Some disadvantages are: fuel can catch fire,

Have you ever seen the inferno a huge stack of batteries can generate?

> the engine
> is very hot,

How hot is it? They put these things inside model helicopters and
other model aircraft, so it must be manageable.

> have to figure out fuel routing and fuel
> tanks,

Doing this has got to be a lot easier than figuring out where to put
the batteries, which will occupy much more space and weigh far more.
Motorglider builders solved this decades ago.

> very noisy,

What does it sound like? I've never heard one. Worse than a DG 400?
Worse than a small/big/huge dirt bike?

> needs interesting engine instruments,
> needs overhaul, may be damaged by FOD (rocks and such
> in intake).

If mounted on top of the fuselage, it shouldn't be any worse than a
propeller.

--
!Replace DECIMAL.POINT in my e-mail address with just a . to reply
directly

Eric Greenwell
Richland, WA (USA)

[Tim Ward]

"M B" > wrote in message
...
> Some disadvantages are: fuel can catch fire, the engine
> is very hot, have to figure out fuel routing and fuel
> tanks, very noisy, needs interesting engine instruments,
> needs overhaul, may be damaged by FOD (rocks and such
> in intake). An electric engine seems to have only
> two major disadvantages: very heavy batteries and
> a prop that takes space to turn and to stow. There
> was a Luscombe that had a 150hp turbine that I saw
> up at Columbia, CA. I heard it caught fire in Texas
> a few years ago and was destroyed (although rumor had
> it the people survived fine). The turbine idea sounds
> neat, but I would personally be a little wary of all
> the heat it produces and the very real fire hazards.
> But I bet it'd be a real airshow pleaser!

Have you ever seen a lithium cell that had what the manufacturer delicately
referred to as "an outgassing event"?
Granted that fuel can catch fire, at least the oxidizer is not mixed in with
it. It only burns on the surface.
A high energy density battery is more like a rocket engine -- or a bomb.
The fuel and oxidizer are already mixed together, and so reactions can
happen very quickly.
This is not to say that batteries are bad, just that any high energy density
storage system is going to have safety concerns.
Tim Ward

[Spider]

<I'll try to remind again of the existence of "Bocian - Puls" - a SZD-9
Bocian equipped with two tiny pulse <jet engines for take off purposes.
<Of course it was an experimental design.
<
<Regards,
<--
<Janusz Kesik

<visit www.leszno.pl - home of the www.wgc2003.pl

Here you can find some photo of the glider:
http://www.piotrp.de/SZYBOWCE/pbopuls.htm
They are poor due to old paper scan.
Also some info available but only in Polish and German.

Regards
Jaroslaw Zaczek

[Stefan]

Eric Greenwell wrote:
>
> > very noisy,
>
> What does it sound like? I've never heard one. Worse than a DG 400?

It's obvious you've never heard one, if you ask this. Go to a model
aviation club (I don't know the correct word, but you know what I mean)
and listen to their model jets.

The relation of my club to our neighbours is not always without
problems, but all in all, we live in peace together. I guess this would
change very fast if we would operate jet driven gliders!

Stefan

[Martin Gregorie]

On Wed, 17 Sep 2003 20:43:14 -0700, Eric Greenwell
> wrote:

>
>> very noisy,
>
>What does it sound like? I've never heard one. Worse than a DG 400?
>Worse than a small/big/huge dirt bike?
>
I believe that model size turbines are quieter than the equivalent
glow-motor driven ducted fans. I've heard their sound described as
being similar to first generation full size jet engines.


--
martin@ : Martin Gregorie
gregorie : Harlow, UK
demon :
co : Zappa fan & glider pilot
uk :

[Bill Higdon]

Bob,
Your correct as to the spelling of Max Dreher's last name.
Bill Higdon
Bob Whelan wrote:
> Max Dreher...in (I believe) a Prue 215. Several articles by/about him in
> "Soaring" mags from the 1960's.
>
> Regards,
> Bob Whelan
> - - - - - -
>
> "Bill Higdon" > wrote in message
> ...
>
>>Janusz Kesik wrote:
>>
>>>I'll try to remind again of the existence of "Bocian - Puls" - a SZD-9
>>
> Bocian equipped with two tiny pulse jet engines for take off purposes.
>
>>>Of course it was an experimental design.
>>>
>>>Regards,
>>>
>>>
>>
>>First one I know of was a fellow by the name of Max Drayer(SP), he built
>>his own turbine engine back in the early 60's. The engine was
>>reatractable when not running. Oh yes he flew ME-262's during the last
>>of WWII.
>>Bill Higdon
>>
>
>
>

[Stefan]

Bill Higdon wrote:
>
> Your correct as to the spelling of Max Dreher's last name.

It's asking a bit much to be able to spell a foreign name when you can't
spell your own language, I guess...

Stefan

[Spider]

> Jaroslaw,
>
> thanks for the link. Would you be able to provide a translation of the
> text on this site? I am just curious about the strangely bent pipes in
> front of the pulse jet engines. Does the text make any reference as to
> why they have this shape? Looking at a German V-1 pulse jet at the
> Dayton Airforce Museum, it doesn't look anything like that.
>
> Thanks,
> Ulrich Neumann
> Libelle 'GM'

All right Ulrich

The answers for your questions you can find from links of Bill Higdon, so
let me just provide some simple translation from this site.

"The second prototype of SZD-9 "Bocian" was equipped with 4 tiny pulse jet
engines, developed by PhD Eng. Stanislaw Wojcicki at the Institute of
Aviation. MSc Eng. J. Sandauer guided redevelopment of the glider. The work
scope included rebuilding of the wing - airbrakes were removed, wing
ferrules were strengthened and elastic engines suspensions were installed
(due to pulsejet engine generates vibrations that can lead to construction
damage). In order to prevent heat defects (pulsejet engine heats up to very
high temperatures) bottom part of wings were covered with asbestos and
duralumin sheets. Also non-flammable paintings of bottom part of wings, rear
part of fuselage and tail were implemented.



Electrical, air (compressed air necessary for start-up) and fuel system of
engines let pilot to start them up in pairs during flight. Necessary
pressure for fuel system was supplied from nitrogen cylinder placed together
with fuel tank in adapted trunk.



Engines were built of heat-resisting metal sheets. Nominal thrust was about
10 kgf each (weight 6 kg), fuel consumption about 8 liters of gasoline per
hour. Ignition has been started after pressure generation in chamber and
mixture firing with spark from ignition plug. The ignition plug has been
turned off during engine operation. Also additional air supply was not
necessary. Fuel supply system needed pressure within the range of 2.8-3 atm.



Due to poor thrust the glider was not able for self-launching. MSc Eng. J.
Bojanowski and Eng. S. Makaruk have carried out the flight tests.



Further design works of implementation biggest pulsejet engines (total
thrust 80 kgf) have been going on in order to enable self-launching.
Unfortunately technical data and further lot of the glider are unknown for
author."

Two old photos below pulse jet engine scheme.
Left:
"Twin pulse jet engine below the wing. Take off and landing damage
prevention metal bow can be seen."
Right:
"Fuel control system - fuel pipes and valves can be seen."

Maybe there are some mistakes but I hope it could be understandable.
If you prefer German version here is link:
http://www.piotrp.de/SZYBOWCE/dbopuls.htm

Best Regards
Jaroslaw Zaczek

[Lou Frank]

Jet Noise...

Some 30 years ago, after a promise to let me fly it, I helped a visiting
pilot ( like me) to rig his jet equipped Diamant at Schanis (Switzerland).
I have no idea what the 'engine' make was, it was mounted on top of
fuselage - pilot was just about able to carry it!

After an eardrum shattering warm up and almost ready to fly, the owner/
Chief Instructor of airfield strolled across and asked if Diamant owner
proposed launching with engine. On getting an affirmative the owner of the
airfield bluntly refused permission - he said that the residents of the
nearby village were still complaining about the noise created when he last
flew there over a year ago. Imagine the din echoing off the mountains flying
at around 50kts for ten minutes in a country that has very strict laws on
noise!

The Diamant owner reluctantly removed the engine and took an aerotow. He
confided that he was seldom able to fly more than once at any given airport.

Later, on a particularly quiet night, I thought I heard a faint echo of the
Diamant jet, but it could have come from nearby Zurich International...

Never did get to fly it...

Lou Frank



"Eric Greenwell" > wrote in message
.. .
> In article >,
> says...
> > Some disadvantages are: fuel can catch fire,
>
> Have you ever seen the inferno a huge stack of batteries can generate?
>
> > the engine
> > is very hot,
>
> How hot is it? They put these things inside model helicopters and
> other model aircraft, so it must be manageable.
>
> > have to figure out fuel routing and fuel
> > tanks,
>
> Doing this has got to be a lot easier than figuring out where to put
> the batteries, which will occupy much more space and weigh far more.
> Motorglider builders solved this decades ago.
>
> > very noisy,
>
> What does it sound like? I've never heard one. Worse than a DG 400?
> Worse than a small/big/huge dirt bike?
>
> > needs interesting engine instruments,
> > needs overhaul, may be damaged by FOD (rocks and such
> > in intake).
>
> If mounted on top of the fuselage, it shouldn't be any worse than a
> propeller.
>
> --
> !Replace DECIMAL.POINT in my e-mail address with just a . to reply
> directly
>
> Eric Greenwell
> Richland, WA (USA)

[Robert Ehrlich]

Bill Higdon wrote:
> ...
> That is a example of a valve less pulse jet.
....

Or rather a pulse jet with an aerodynamic valve instead
of a mechanical one. A such pulse jet was also manufactured
in France under the name "Escopette" and tried on glider(s).
Probably some of these flights were on the field were I
fly since in the bar there is a picture of a vintage glider
on which you can read "Emouchet Escopette", although the
engine(s) is not visible. Emouchet is the name of this type of
glider.

The principle of the aerodynamic valve is based (as I understood
it) on the different flow of air/gases during intake and exhaust.
During intake the air comes from almost all directions into the intake hole.
During exhaust it forms a jet which is caught by the U shaped
tube and redirected by it in the proper direction, i.e. backwards.
There is some space between the U tube and the intake to allow
the incoming air to come from the outside of the U tube. The
formation of the jet is the thing that allows this to work during
exhaust despite this space.