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Jet turbine reliability



 
 
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  #21  
Old June 4th 15, 11:37 AM posted to rec.aviation.soaring
Craig Lowrie
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Posts: 32
Default Jet turbine reliability

Chris is exactly right. The HPH Shark Jet uses a industrial
powerplant with over 700 made for UAV / Drone use, so maturity is
high. Field reliability is very good with minimal issues... Normally a
"one-off" re-tuning exercise. You mix turbine oil with JET A1 and
this total-loss approach avoids the needs for a separate lubrication
system. Drag on deployment is not noticable at all. The Engine
management is achieved with a FADEC controller which leaves you
with a single 'Throttle' knob on the panel. HPH have been shipping
the Shark Jet for over 5 years now and into the UK Market (where I
live) for about three years. With "Double-digit" Shark Jets in the UK
I have never had to remove a Jet powerplant yet....

At 05:47 04 June 2015, wrote:
"They are MODEL engines and are not "man rated" by the FAA.

There are
seve=
ral YT vids showing how they are built and assembled."

A very inappropriate comparison. It's akin to comparing an

experimental
air=
craft with a certified, high capacity transport category

aircraft.=20

The Williams has undergone destructive testing, blade

containment testing,
=
is certified for flight into known icing, use on ground, use in rain

etc
et=
c.

Using M&D's engine as an example, it has no accessory gearbox

so no
lubrica=
tion; you add extra oil to the fuel like a 2-stroke. It has no

electrical
s=
ystem thus no self-sustaining fuel delivery nor command and

control. Both
=
of those functions are powered by the battery so it's essential to

leave a
=
battery untouched 'for Justin'. It's not approved for ground

operation
oth=
er than maintenance nor for flight in rain. It's a simple, elegant,

low
wei=
ght, low drag thrust source for sustaining. A 'getcha home jet'

with only
t=
he operating principle as a similarity with Williams and other

certified
pr=
oducts. And thanks heavens for that! It would be too large, too

heavy and
=
too *EXPENSIVE* otherwise.

CJ


  #22  
Old June 4th 15, 02:13 PM posted to rec.aviation.soaring
[email protected]
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Posts: 121
Default Jet turbine reliability

Comparisons aside, my point is simply this, never put yourself in a position where your safety or life is dependent on the operation of one of these small turbines. Several other previous posters agree with me on this.
  #23  
Old June 4th 15, 02:59 PM posted to rec.aviation.soaring
Simon Waddell[_2_]
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Posts: 7
Default Jet turbine reliability

Well, the same applies to ANY type of glider engine.

When Lord Derby was once asked why he always flew in four-engined aircraft
he replied that it was because there were no six-engined aircraft.


At 13:13 04 June 2015, wrote:
Comparisons aside, my point is simply this, never put yourself in a
position where your safety or life is dependent on the operation of one

of
these small turbines. Several other previous posters agree with me on

this.


  #24  
Old June 4th 15, 03:14 PM posted to rec.aviation.soaring
son_of_flubber
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Posts: 1,550
Default Jet turbine reliability

On Thursday, June 4, 2015 at 10:00:04 AM UTC-4, Simon Waddell wrote:

When Lord Derby was once asked why he always flew in four-engined aircraft
he replied that it was because there were no six-engined aircraft.


And to seque back to glider mounted jet engines... What happens if you mount two of these engines on a glider? Enough thrust for self-launching? Redundancy for sustaining (or to circle back on aborted takeoff)? Twice as many things to break? 2X the cost?
  #25  
Old June 4th 15, 06:52 PM posted to rec.aviation.soaring
[email protected]
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Posts: 114
Default Jet turbine reliability

Sure. But it's all about fuel. These thing gulp it down. Fueling system in the case of an SL can't be an afterthought. It must be designed into the ship, and would likely mean multiple tanks etc. Probably fuselage and wing tanks. A poorly designed fueling system can lead to all sorts of issues with turbines.

And to seque back to glider mounted jet engines... What happens if you mount two of these engines on a glider? Enough thrust for self-launching? Redundancy for sustaining (or to circle back on aborted takeoff)? Twice as many things to break? 2X the cost?


  #26  
Old June 4th 15, 06:57 PM posted to rec.aviation.soaring
[email protected]
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Posts: 374
Default Jet turbine reliability

I agree with Simon - it is crazy to bet your life or glider on the reliability of any type of engine. Personally I am far more concerned about windmill starting draggy 2 stroke turbos than a turbine which why my glider is at the workshop to get its turbine installed today.

It is clear from several posts that some contributors have absolutely no idea of the depth and intensity of the EASA certification process that the three new turbines have had to go through. A post mentioned broken blades so as an example of one test - the M+D jet is planned to have a 500 start and run cycles TBO but, as it was explained to those of us waiting, they had to demonstrate 3 times that number of starts and power runs with cracked blades with no failure - which tests alone took several months to run.
  #27  
Old June 4th 15, 07:18 PM posted to rec.aviation.soaring
[email protected]
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Posts: 114
Default Jet turbine reliability

A post mentioned broken blades so as an example of one test - the M+D jet is planned to have a 500 start and run cycles TBO but, as it was explained to those of us waiting, they had to demonstrate 3 times that number of starts and power runs with cracked blades with no failure - which tests alone took several months to run.

That is why I mentioned later, I expect the QA of these turbines to be much better than that of the typical model turbine. Good for them. I do hope they model FOD accurately though. Nice clean lab is one thing...
  #28  
Old June 4th 15, 08:17 PM posted to rec.aviation.soaring
J. Nieuwenhuize
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Posts: 83
Default Jet turbine reliability

Multiple engines (especially for self-launch) make a lot of sense since price scales neatly with thrust.

2X 230N thrust for a light single-seater, or 2X 800N for an open-class ship would allow a self-launcher with acceptable cruise fuel consumption and self-launch capability.

  #29  
Old June 4th 15, 09:07 PM posted to rec.aviation.soaring
[email protected]
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Posts: 114
Default Jet turbine reliability

On Thursday, June 4, 2015 at 12:17:49 PM UTC-7, J. Nieuwenhuize wrote:
Multiple engines (especially for self-launch) make a lot of sense since price scales neatly with thrust.

2X 230N thrust for a light single-seater, or 2X 800N for an open-class ship would allow a self-launcher with acceptable cruise fuel consumption and self-launch capability.


That's close to what I came up with when investigating for a single seater. You would probably want to carry at least 15 gallons of fuel for the single. Interestingly, when you throw in oil and anti-static, the runtime cost are quite high. You end up finding how economical the old fashioned internal combustion self launch really is. It accomplishes quite a lot with 4 or 5 gallons.
  #30  
Old June 4th 15, 10:05 PM posted to rec.aviation.soaring
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Posts: 190
Default Jet turbine reliability



That's close to what I came up with when investigating for a single seater. You would probably want to carry at least 15 gallons of fuel for the single. Interestingly, when you throw in oil and anti-static, the runtime cost are quite high. You end up finding how economical the old fashioned internal combustion self launch really is. It accomplishes quite a lot with 4 or 5 gallons.


So in the case of the M&D/JS-1, is it correct to assume the preferred fuel is Jet A? To Jet A, what specific oil and anti-static are added and what is the added ratio?

 




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