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Solar Turbines for the Mosquito
#1

There is a lot of discussion on what Turbine will or could work in a Mosquito Helicopter.  I will try to shed some light on the choices.

Solar Turbines, more specifically the T62 family I consider one of the nicest and best designed (for it's time) gas turbines to be found especially for the experimental world.  I believe there are over 30 different models ranging from about 25 HP to over 300 HP.  Many of the engines have interchangable parts and most all are based on the same basic design platform.

The Small series like the T62T-16B and T62T-2A1 range from 75 to 95 HP and there are about 6 other models that have parts interchangability with the T62T-2A1 and even the T62T-32 has some parts that fit the _2A1 engines.

So what is the best engine:  In my opnion the T62T-2A1 is about as good as you can get for the Mosquito application.  It produces 95 SHP, outputs 6000 RPM and is a mechanically governed engine (no electronics to fail) and only weighs about 65 LBS.  The Mosquito normally uses around 30-45 HP and maybe a Max of 60 HP under most conditions that leaves a very nice 30% engine reserve and the engine never has to work very hard.  This is good for long engine life.

What about the Solar T62T-32:  It's a great engine but it is physically 40% larger, 160 SHP with 6000 RPM output and weighs arround 140 LBS.  The size and weight are the main problem and then there is the electronic governor, although they can be converted to the mechanical fuel control the mechanical fuel controls are almost non-existant.  The engine is way over powered and drinks too much fuel so it really is not a good choice.  The power head can be fitted to a size and weight reduced gearbox like the Helicycle but you still have the 10-14 GPH fuel burn.

What about the Tierny TT-10 turbine:  This is an interesting little engine, it is all electronic fuel injection, weighs in at around I think 80 LBS and outputs about 75 KW (56 HP) and from what I know is a fairly reliable engine.  The major drawback is the 12,000 RPM output, which because it is so high it will have to use a secondary Planetary Gear set to reduce the RPM. Basically another gear box and it just doesn't have quite enough power.  So this engine is not a practical choice either.

What about the Garrett GTP30-67:  Another nice turbine, weighs about 85 LBS, rated at 67 SHP, physically a little larger than the Solar T62T-2A1, output RPM is 8000.  The draw back to this engine it is an older generation engine that are relatively hard to find parts for and still requires additional gear reduction to get to 6000 RPM.

What about the Solar T62T-40-1:  This is a current production engine that is used in the Black Hawk and several other aircraft. There are about 8 variations of this engine. the 40-1 is rated at 56 air and 56 SHP and output 12,000 RPM. It is a bleed air engine that also supplies shaft power.  These power heads can be adapted to the -2A1 gear box and configured in a non-bleed air setup giving only shaft power.  The main concen with this setup is the power head is capable of producing a lot more power than the -2A1 gear box can handle.  These don't show up very often and parts will be expensive because non-surplus parts availability.   I have built a few in the -2A1 configuration and the engines run good but are yet to be proven in a Helicopter. This would however be an interesting trial in a Mosquito.

I don't off hand know of many other engines that will work that might be generally available but if anyone knows of possibilities let me know.

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#2
Hi Chris, this is great information.

I'm sure you've been asked this before, are there any turbines that can operate vertically?

I believe that one of the things that adds weight to the XET is the gear box required for the horizontal shaft drive.

I dream of an ultralight turbine Mosquito, but I believe we'd have to have a vertical drive and close to 6000 rpm so an extra gear box would not be required for orientation or gear reduction.

Larry (Pfranc) has a turbine that he shows sitting vertically.
Larry, what kind of turbine is that?
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#3

Hi Lorne

I am not aware of a bolt up engine the can be mounted vertically.  The engine lubrication is the main issue.  In the case of the Solar T62, they were all designed to be operated horizontally with upto about a 15 degree angle.  You would have to re design the lubrication path and collection system and likely use a remote Oil Sump

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#4
I've seen pictures of a Garrett JFS 100 mounted vertically I don't know if that is recommended or not just sharing what I have seen. I do know that particular engine was never designed to be run continuous as it was a F-15 and A-7 starter motor with very little lubercation, but im not sure if it can be or has been modified. There are plenty of strange and funny applications of this engine, one being on a golf cart that can go 80 mph, pretty funny video on youtube!
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#5
Thanks for the information.

How immune to gyroscopic couples are these engines? Turning an engine rapidly in yaw or pitch would create an enormous sideways force on the bearings at the rotor speeds turbines run at and these engines weren't designed for that.

Thanks.
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#6
solar made these engines for GPU and APU formats. Our engine the T62-2a1 is a APU model which was used in the CH-47. It was also used as a powerplant and tested by the US Navy from the early 60's all the way up to the late 70's. The biggest issue I have read about with these engines is people who have tried to use these engines in a fixed wing application where a throttle would be used. This engine as you know is designed for contiuous use at a constant rpm and was never intended to be run at varied rpm's. In our helicopter we are running at 100% and the load of the rotor rpm would very similar to the load of an APU application such as controlling hydraulic flow packs.
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#7
Hoyte, that is a great question! Most of the life time on these while in a helicopter as an APU, it is on the ground. Almost no pitch, roll, or yaw. With the amount of energy that these have stored up in the spinning components, It must have an enormous amount of gyroscopic stability. To bring it off of these axis must require alot of force which should mean bindeing the bearings. I know they get away with this on other turbines, but is this built to be agile while running at 100%? Its a great question. Maybe they are built to with stand this problem. Or, maybe they are not built to with stand it so you lower the life cycle TBO, anticipateing this problem.
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#8
The JFS-100-13A is a nice little engine it has a free wheel power turbine and produces 100 SHP excellent power to size and weight.  The problem with them is they were designed as a momentary use engine and don't have very good bearings or lubrication system for sustained use.  In the hands of a competent individual those problems could be fixed.  The other issue is cycle limited wheels and easy hot start.  It only takes one hot start to ruin the hot section and a new wheel is around $3000.00.  I think it would be possible to make the engine work in a verticle situation but not very practical.
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#9
As far as I am aware the T62T-2A1 is specifically designed for helicopter application (CH-47).  The clearances inside these engines are pretty loose and appear to be more than  sufficent to counteract any Gyroscopic action.  Generally when these engines fail the grind to a hault from over temp or failed bearings.
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#10
Here is a website showing the t62 mounted on a single seat helicopter for the army.
http://www.gasturbine.pwp.blueyonder....
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