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.

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?

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?

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.

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...

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.

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.

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?

The M+D turbine manual specifies diesel or JetA1 mixed with 4% 2 stroke oil or Aeroshell 560 turbine oil. The tanks are about 42 litres. It gobbles fuel but a one way direct climb and glide retrieve flight will be cheaper than a return road retrieve (by the time you add fuel and vehicle depreciation etc)- but obviously more than a turbo retrieve.

On Thursday, June 4, 2015 at 5:34:36 PM UTC-4, wrote:
The M+D turbine manual specifies diesel or JetA1 mixed with 4% 2 stroke oil or Aeroshell 560 turbine oil. The tanks are about 42 litres. It gobbles fuel but a one way direct climb and glide retrieve flight will be cheaper than a return road retrieve (by the time you add fuel and vehicle depreciation etc)- but obviously more than a turbo retrieve.

Gobble as well as gulp...with Jet A at +/- $5 a gallon and AeroShell 560 at $15 a quart that works out to north of $100.00 to fill up the JS-1. Still certainly preferred to landing out a gold-platted crystal slipper 90 miles from home.

So lets round off to $1.00 per M&D jet sustainer mile. Retrieve would be $.65 to $.85 a one-way mile so 180 x $.75 = $135. Certainly not a Solo but still cheaper than a retrieve by road or aero.