HP-18J Twin Turbine Self-Launch Sailplane

[cesse...@versevo.com]

Here are a couple of links from my latest project. The sailplane is a Richard Schreder HP-18 kit from the 70's that I built over the last 4 to 5 years. I am using twin Jetcat P300 turbines for self-launch and sustained flight. There are numerous modifications that have been incorporated into the aircraft including the turbine installation.

First flight: https://www.youtube.com/watch?v=YepD4f9igW8 The best section is from 1:30 to 2:00 into the clip.

Colorado fly by: https://www.youtube.com/watch?v=y9BjPPhgWxo Short take of a turbine fly by from Owl Canyon Colorado in June.

Cockpit self-launch and climb out: https://www.youtube.com/watch?v=Dsc3wvxr95Y Takeoff from our local soaring field in Wisconsin using the turbines.

Restart and fly by: https://www.youtube.com/watch?v=rpgpWOG-9jI In flight turbine start and fly by.

Thanks,
Chris

[AS]

Chris, thanks for sharing! Could you please post some photos of the jet installation? Inquiring minds want to know how you did it, i.e. are the jets retractable or do they stay outside?

Uli
AS

[dbra...@gmail.com]

Nice. what's your fuel capacity and are you running diesel?

[Bruce Hoult]

The last video talked about retracting the engines once they cooled below 30 C (preferably 25 C). Which seems awfully cold. I can't imagine what bad would happen if they were 50 or 60.

There doesn't seem to be an excess of power. More like sustainer than self-launcher.

I was surprised how slowly the glider was flown during climb (60 knots). Effective power should be a lot higher at 80 or 90 knots (constant thrust), without a lot more airframe drag.

I was also surprised how low and slow and far out the end of downwind and base were flown, especially considering there was already flap out on downwind. And considering that HP18s can do very steep approaches. It's not an ASW12 :-)

[Dan Marotta]

Very nicely done!

I'm interested in the FAA's take on this and will you, as the builder,
have to get a Letter of Authorization to fly it since it's a jet?

--
Dan, 5J

[tkn...@earthlink.net]

Noise is usually a big problem with this type of power plant.

If the noise is exceptionally loud, we could not allow a takeoff at our gliderport.

The towplanes (Pawnee) produce a lot of noise, however, it is in a different sound level, and more acceptable. Further, the locals are used to it after 40 plus years

A turbine launch would draw more attention to towing activities and perhaps draw more attention to noise made our conventional towplanes.

Tom Knauff

[lynn]

I timed the takeoff by watching the altimeter and it appeared to be climbing 500 to 600 fpm.

[Frank Whiteley]

I chatted with Chris while he was at Owl Canyon. This is his four project and he had to search for a good, uncompleted HP-18 kit. Nearing completion, he had to obtain a glider rating to fly it. He consulted closely with Bob Carlton during this project, indeed the engines are from Bob's jet Silent. Chris has an interesting story to share and I hope it will appear in Soaring or Sport Aviation.

Frank Whiteley

[casses...@gmail.com]

Uli,

The entire build was documented on the HP Glider Forum Web site https://groups.yahoo.com/neo/groups/hp-gliders/photos/albums/238228337

The turbines are retracted into the turtle deck.

Thanks,
Chris

[casses...@gmail.com]

On Saturday, July 23, 2016 at 12:38:11 AM UTC-5, dbra...@gmail.com wrote:
> Nice. what's your fuel capacity and are you running diesel?

I started with Jet A and switched to gas station diesel. 5% turbine oil is also mixed for bearing lubrication.

The fuselage fuel cell holds just under 7 gallons. I have wing tanks that hold an additional 7 gallons which I currently am not using.

Thanks,
Chris

[casses...@gmail.com]

Bruce,

The turbines retract into the fuselage, to make sure I am safe with the temps I leave them extended until until

[casses...@gmail.com]

> The turbines retract into the fuselage, to make sure I am safe with the temps I leave them extended until they are cooled.

The total thrust output is 135 pounds.

[Bruce Hoult]

I understand, but 30 C? They'd get hotter than that just sitting in the sun. Or even in the shade, a lot of places people fly at!

[Sarah]

Depending on where the temperature sensor is, other parts of the engine may be hotter. If they're not a huge drag penalty maybe it's worth it.

I think I saw somewhere it will be at Oshkosh this year. Is that right?

[casses...@gmail.com]

It will be on the flight line all week by the Home builders headquarters.

[casses...@gmail.com]

Tom,

I have flown at your field and agree, it would be quite loud in your valley. The sound output is similar to a piston twin but with a jet signature.

[casses...@gmail.com]

Hello Frank,

I had intended on using Bob Carlton's AMT 450's but the manufacture went out of business. I ended up using the Jet Cat P300's since they had a US sales and service facility.

I hope to have an article to share with the public thru the SSA or EAA later this year.

[cesse...@versevo.com]

Dan,

Bob Carlton worked with the FAA regarding the re-writing of the latest version of 8130.2H, which specifies that only turbojet powered AIRPLANES require a special authorization. Gliders or sailplanes are categorized as aircraft and not airplanes.

Nothing else was needed and the FAA inspector provided me with the limited airworthiness upon completion of the inspection and test runs of the turbines.

Prior to the flight testing I also receive the self launch endorsement.

Chris

[Dan Marotta]

That's great!

Bob has done a loot of good things with the FAA and this is certainly
one of them.

Enjoy that thing!

Dan

--
Dan, 5J

[mbor...@borgeltinstruments.com]

Congratulations! Nicely done. If you email me I'll send you my jet performance spreadsheet (not for widespread dissemination at this time). It seems to be validated by reports of performance of various jet projects.

My own jet is closing in on being finished. Just need to check out electrics and software in the extend/retract controllers. All automated with just a master switch for each engine and a retract/extend/run 3 position switch for each. Single throttle rotary pot.

Some observations:

Performance depends quite sensitively on the deployed engine/mount/airframe doors and hole drag. Minimising this is a REALLY good idea as jets like to fly fast. Power delivered to glider = thrust x true airspeed

A simple ejector nozzle as used on early Learjets as an add on for noise reduction can reduce noise by 3 to 5dB. That is one half to one third the noise level. If done right you should get a few percent thrust increase too. See some early turbojet powered DC-8 aircraft.
I've been to a few jet R/C model meets and the jets really don't seem all that noisy until they are moving away from you and you can see the exhaust pipe. Even then not so bad. Small turbines produce most of their noise in the ultrasonic range.

Mike

[Bruce Hoult]

It's quite noticeable with offroad motorcycles that 2 stroke bikes sound louder close up, but it's the thumpers you can hear from 5 km or a couple of valleys away.