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.

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.

....And let's not forget to amortize the extra $40-50,000 for acquisition
cost. So, if you land out 40 times during the life of the glider, don't
you also add $1,000+ to the cost of the retrieve?

Neglecting, of course, resale to someone else who doesn't want the
adventure of a field landing.

On 6/4/2015 7:54 PM, wrote:
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.


--
Dan Marotta

Neglecting the resale value is a big aspect to neglect. I have only once lost a little money after selling part or all of 9 gliders over the years. Moreover I would far rather have a sustainer than a motorless glider to sell. In Europe e.g Discus BTs and Duo Ts are selling for significantly more than the original cost.

I've been working on the jet glider concept for over 10 years. 5 years ago, after a false start with somebody who never delivered what was promised I bought a couple of AMT Titan engines and have almost finished fitting them to my Ventus C 17.6 A fuselage. They are fully retractable. Just some electrical connectors to go and we're ready to do engine runs.
Yes if one engine makes a turbo, two make a self launch and two are better than one even if the installation is a little more difficult. As a slight bonus two Titans of 400N each are in fact cheaper than one Nike of 800N thrust from the same manufacturer.

Fuel consumption: Should get to 2000 feet above ground for around 5 to 6 litres of jet A/jet oil 4.5% mix. Compares favorably with aerotow. Retrieves cheaper than by car, without the outlanding risk and way cheaper than aerotow retrieves. I made a jet performance spreadsheet for takeoff and climb performance. Seems to validate against flying jet gliders. Predicted climb without water ballast nearly 800fpm (SL, standard day at 70% thrust on both engines. Will still climb 280fpm on one and 400fpm on one at 85%. Retrieve range close to 250km. I got 45 litres of fuel and the engines into the A model fuselage without impinging on any space used by pilot or equipment.

Noise: Enough installed thrust and good rate of climb means you're away from the ground quickly. Use airframe shielding and aviation industry noise reduction methods. Existing jet gliders do none of this. I saw and heard Bob Carlton's Super Salto at Avalon in 2009. It wasn't very noisy at all. Neither, I am told, was the Jet Silent he flew a couple of years earlier. I've got a couple of translating ejector nozzles just like the early DC-8 although in this case they are translating in order to minimise engine length for retraction.
Don't forget the noise stops at top of launch, unlike that from a towplane.

Safety: There are two things that can go wrong with the jets. They could catch fire or have a RUD event. I have a fire detection system and Halon fire extinguisher system for the former and 4130 steel around the compressor and turbine sections and the engine compartment is lined with fiberfrax over 8 layers of 170 gram kevlar. The Titan turbine blades are almost the same mass and speed as a .22LR rifle bullet so I took out the .22 and made some samples and tested.
A few years ago a bad batch of compressors made it into model airplane jet world. I gather when they failed some bits dribbled out the front of the engines. I'm not too worried about this.

Operations: Two engines means that launch failures should be rare. You only need to get one out of two running to fly away from a potential outlanding and extending the engines is not a large drag increment. The engines will NEVER be run at 100%. 70% is enough to meet CS22 takeoff at 410Kg and at 500Kg 85%.
Best retrieve range is by running both engines. Should get to 17000 feet above engine start point after a 2000 foot launch.

As for a few other points raised he The engine in the 304 jet appears to be a Titan with external shielding and I'm told the M&D engine internals are bought from AMT and are the Titan. The Titan seems to be rapidly becoming the standard 400N thrust engine.Certainly seems to be from what I saw. No external shielding which may be why the difficult and expensive EASA certification process just like Draline with the AMT Olympus(8 years.Different starter and case and I'm told, combustor section.
Certification will be the death of this sport.It will make anything vastly more expensive, particularly in a low volume business like soaring.

Anyway, I'm looking forward to having this flying over the next few months and the test flying program should be a lot of fun.

I'm also looking forward to hearing about the flights of the GloW. Should be a fun glider and the electric wheel is a fine idea.

I'll also be testing the new total energy system which completely rejects horizontal gusts and two other new ideas which may change the way glider variometer systems are done.

Mike Borgelt
Borgelt Instruments