Turbine power for self launch and sustained flight.

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delta

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Referring back to the older posts discussing engine options, does anyone make a high-bypass turbofan engine for models?

Bruce :)


That would be neat but all the ones I've seen had centrifugal compressors. Can you do a bypass duct with a centrifugal compressor? On another note I've seen a little 7hp turboprop

There was a UK company displaying a TF engine they were developing at Oshkosh in 2004. The centrifugal engine without the geared fan was probably in the 40lb thrust range. They were talking 2-400 lb thrust with the fan. I tried to contact them without success a few month later for a follow up. I'm sure the gear box was the deal breaker or we'd see them all over the place. Reducing that kind of rpm to a 20" fans useable level with reliability would be a project worth doing but certainly not easy.
 

Cozyflier

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After a number of years of construction, the project is nearing completion. I have replaced the US Micro jet turbines with two Jet Cat P300 turbines. These engines are greatly simplified in comparison to the older turbines (no propane needed to start). The P300's also provide 68 pounds of thrust each for a total of 136 lbs. The turbine extension and retraction is controlled by a linear actuator, the turbine frontal area will be similar in drag to the retractable landing gear. The fuel cells consist of a 6.5 gallon header tank and two 3.5 gallon wing tanks. Ideally I would prefer to only use the header tank if possible to keep the rigging and fueling procedure simplistic.

On paper or in theory, the climb rate will be in the 800 fpm range at full power. Here are my rough calculations: Gross weight 800 lbs. Glider L/D with engines and gear extended = 38/1. GW of 800 lbs./38 L/D= 21 lbs. (21 pounds of thrust to maintain level unaccelerated flight). Turbine thrust = 136 pounds minus 21 pounds = 115 pounds remaining for takeoff and climb. Best L/D speed = 60 kts. GW of 800 lbs./60 kts = 13.3 115 pounds thrust remaining/13.3 = 8.64 or 864 fpm climb rate.
 

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autoreply

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That looks awesome.

Note that your climb isn't realistic.

Best climb with a jet takes place at higher speeds. Noticeably in sailplanes (very low drag). A modern 15M class sailplane with a 60 kgf thrust jet will have best climb rate way beyond 100 kts, just a rough guess, but I'd think at 120-140 kts.
 

Cozyflier

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After a number of years the project has been completed and had flown. I am 6 hours into the flight testing stage as a true glider while using a tow plane for launching. Most of the flight envelope has been expanded and defined in the sailplane mode. Upon completion of the 10 hours of flight testing, the turbine testing phase will follow with an additional 5 hours of flight testing.
 

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Cozyflier

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The HP-18J is currently at the end of its testing phase as a true sailplane (non turbine powered) and has been a joy to fly. I am starting to get used to the plane but have a ways to go before I am one with the craft. It seems to be a bit weak on yaw control during cross wind landings and landing roll out, but it may be my lack of experience.

I am considering the construction of a new wing with a 18 meter span. This would be a one off project made out of foam and carbon with construction similar to the Rutan composites (hot wired cores, carbon shear webs,carbon spar caps and carbon wing skins. My thought is to build it with a 15 meter length and add removable polyhedral wing extensions for a 18 meter length with double duty winglets (15 and 18 meter wing).

My concern after reviewing this with our local club members is the yaw stability and possible compromised control with a 18 meter length. If the tail boom would need to be lengthened and the stabilizers and ruddervators would need to be increased in size, I my as well build another sailplane.

My question for the group is, would a 18 meter wing work with the current HP-18 fuselage geometry (current tail boom length and stabilizer/ruddervator area) and might anyone else have experience with such an idea.

Change ideas from existing design:

1: Increase the area on the stabilizers/ruddervators by some amount (possibly 4-6” in height with an extended ruddervator trailing edge). Goal is to improve yaw and elevator authority without extending the tail boom length. New surfaces could be manufactured like the new wings with foam cores and carbon spars, shear webs and skins. Currently my ship is nose heavy and I have weight in the tail cone for mid CG flight testing. Some added weight at the tail would actually be beneficial.

2: Build a 18 meter wing with a 15 meter platform and polyhedral removable wing tips. Both wing options (15 and 18 meter) would have removable wing tips for the winglets. The wing could use the Udo 15.3 geometry as I currently have and mount up to the existing fuselage mounting hardware with the flap driver blocks. Another more aggressive idea is to depart from the Udo airfoil and go with new geometry similar to the Ventus C 15/18 meter wing which also has flaps.

3: Install electric linear actuators into each wing for extension/retraction of wing stabilizer wheels for self-launch procedures. This would be similar to the Europa motor glider but faired into the wings for drag reduction. The reason for this addition is to keep the wings level and away from the runway and taxi lights. The self-launch operations will be conducted off of the hard surface to reduce the rolling resistance and takeoff roll length.
 

Topaz

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... My question for the group is, would a 18 meter wing work with the current HP-18 fuselage geometry (current tail boom length and stabilizer/ruddervator area) and might anyone else have experience with such an idea....

I'm afraid that nobody here can answer that for you. This is a "numbers" question. You're going to have to run the stability and control numbers (all three axes) for the increased wing area and span, and then decide if the existing tail is adequate. Since you're already reporting "weak" yaw control, the answer may clearly be, "no", but only running the numbers will tell. You're redesigning the airplane at this point.

If you end up having to either lengthen the tail or make larger tail surfaces, then you're not only redesigning the airplane aerodynamically, you're going to have to do it structurally as well, including the loads analysis and structural analysis. Am I saying not to do it? No. I'm saying you're going to have to do the engineering necessary to make sure it's safe. If you don't feel comfortable doing that, or have the funding to hire it out, then I'm saying, don't do it.

Fly your airplane for a while with the existing wings. See how you like it, once you're used to it. If it's still inadequate at that point, then consider "next steps".

... 3: Install electric linear actuators into each wing for extension/retraction of wing stabilizer wheels for self-launch procedures. This would be similar to the Europa motor glider but faired into the wings for drag reduction. The reason for this addition is to keep the wings level and away from the runway and taxi lights. The self-launch operations will be conducted off of the hard surface to reduce the rolling resistance and takeoff roll length.

I have a much easier solution to suggest: Ditch the fancy retractable outriggers and go for simple plug-in units. My thinking is that in situations where you need maximum soaring performance, you're almost certainly going to have a wing-runner available at any regular soaring operation. For the situations where you're doing a powered cross country or air-show performance, you can plug in the outriggers and take the slight drag penalty. In the rare situation where you want good soaring capability and there's no wing-runner, make sure you've got small (fixed) tip wheels (or skids) and do a wing-down takeoff. Should be a piece of cake from a paved runway. My soaring club had a usual deficit of wing-runners, so I've done more wing-down takeoffs in a pure sailplane than I have takeoffs with runners. It's really not a big deal, and certainly worth saving the weight and complexity of retractable outriggers, IMHO.
 

autoreply

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I am considering the construction of a new wing with a 18 meter span. This would be a one off project made out of foam and carbon with construction similar to the Rutan composites (hot wired cores, carbon shear webs,carbon spar caps and carbon wing skins. My thought is to build it with a 15 meter length and add removable polyhedral wing extensions for a 18 meter length with double duty winglets (15 and 18 meter wing).
Ditch the 2-part wing. Really.

The HP18 is a perfect design for a 3-piece wing. Put the split between flaps and ailerons and you've just reduced complexity, weight and build time by a large amount.

Construction technique, I would go for a Warren-truss wing. Ideal for this application, but unless you're a composite pro who doesn't shy away from some very advanced math and structures, don't even go there.

Foam-cored like you propose is likely lighter than molded sandwich core skins. Water-ballast in the fuselage? If volume works out, it only requires a few pounds more spar, that's it.
My question for the group is, would a 18 meter wing work with the current HP-18 fuselage geometry (current tail boom length and stabilizer/ruddervator area) and might anyone else have experience with such an idea.
It depends. Do the math and calculate Sv and Sh and share those with us. It's likely that we can then give a good answer.

Better, post those of the Nimbus 3, 4, Duo, LS4 or Discus and a few more popular designs. Instant, real-world comparisons.
Winglets (or polyhedral), tip ailerons that only go up (like the Nimbus 3, Ventus C etc) and large wing span but small area help a lot, so don't necessarily shy away.
Change ideas from existing design:

1: Increase the area on the stabilizers/ruddervators by some amount (possibly 4-6” in height with an extended ruddervator trailing edge). Goal is to improve yaw and elevator authority without extending the tail boom length. New surfaces could be manufactured like the new wings with foam cores and carbon spars, shear webs and skins. Currently my ship is nose heavy and I have weight in the tail cone for mid CG flight testing. Some added weight at the tail would actually be beneficial.
Torsional loads on the tailboom increase with the square of such an extension. Unless you do the math; don't extend them!
3: Install electric linear actuators into each wing for extension/retraction of wing stabilizer wheels for self-launch procedures. This would be similar to the Europa motor glider but faired into the wings for drag reduction. The reason for this addition is to keep the wings level and away from the runway and taxi lights. The self-launch operations will be conducted off of the hard surface to reduce the rolling resistance and takeoff roll length.
Don't. Your typical Nimbus 3 wing tips and self-launching in medium-sized grass works fine.

You really don't want all that weight out on the wing. Flutter, structures, complexity.
 

dino

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How about designing longer winglets for yaw stability? Would adding the span as a center section either fixed (think Diana) or removable get you there? Maybe too much added wing area but it would be simpler than a new wing.

Dino
 

Cozyflier

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The weather has improved in the Mid West and the flight testing of the HP-18J has resumed. Last weekend I took a 3,000' tow with the twin turbines at idle. Upon release I applied full power for a 2 minute duration climb for the first test. The climb provided a 1,200 gain or a 600' per minute rate. The turbines were shut down, cooled and retracted into the fuselage. The second test was to extend the turbines and see if they would re-light. Both engines started without any problems and a second 2 minute climb was conducted with the same results, 1,200' or 600'/minute gain. The turbines were shut down, cooled and retracted once again for some soaring. The next test was to establish the data using only one engine. The turbines were extended and one engine was lit. After a 2 minute climb the gain provided 500' or 250'/minute climb rate. After landing, a post flight inspection was conducted with no issues or red flags. The header fuel cell had 7 gallons of auto pump diesel with 5% turbine oil for bearing lubrication. Four gallons had been consumed with 3 gallons remaining in the cell.

In summary, I am quite pleased with the twin turbine and single turbine climb performance, fuel consumption and the positive results of multiple re-starts for climb and sustainer operations.

My next and most likely final test will be a self-launch off of the hard surface with no assist.

Chris
 

Cozyflier

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In general an airspeed of 75 to 80 mph seemed to be the the best range for climb. I did increase it to 105 mph for a short duration and it showed a slowing trend in the climb rate. Many more flights will provide more finite data as I get time to do further speed and climb exercises.
 

Cozyflier

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The weather and wind was favorable for the one remaining flight test last Friday. After assembly and one turbine test run the HP-18J was pulled out to the runway for the last remaining flight test - the self-launch exercise.

Wind speed and direction was 5 to 10 mph almost right down the runway. I strapped in and powered up the aircraft, extended the turbines and proceeded with the start sequence. Once both turbines were started and stabilized at idle (33,000 RPM) the thumbs up was conveyed to the wing runner. Full power was applied (105,000 RPM) and the takeoff roll was started.

Once the aircraft speed exceeded the wing runners pace the left wing dropped and the roller blade wheel at the end of the wing did its job. Within a short time the ailerons took effect and I was once again level and accelerating towards takeoff speed. The airspeed was climbing rapidly and the tail was next to lift followed shortly by the sailplane takeoff. I stayed in ground effect for a couple of seconds then started my climb.

By the time I crossed the end of the runway I had gained 400'. I continued the climb at 60 to 70 KTS until reaching my goal altitude of 3000' AGL. Upon reaching altitude the engines were shut down, cooled and retracted. I soared for 30 minutes, did some more spin exercises to spend my excess altitude and did one re-lite to verify the restart success for the previous weeks testing. Both turbines started successfully and were shut down after a couple of minutes. I returned to the airport for landing and was greeted by my support crew once I rolled onto the taxiway.

My Oudie flight computer provided all of the finite statistics from the flight. The runway takeoff run was between 850 to 900'. The time to climb to 3000' from a standing start was 4 minutes and 45 seconds. The climb rate from the standing start averaged 631' / minute. Total fuel burn for the takeoff, climb and one restart was 3.5 gallons. Remaining fuel in the header fuel cell was 3.5 gallons.

Anticipated flight sequence. Self-launch and climb to 3k, shut down the turbines and retract. Utilize one engine for sustained flight if needed at reduced throttle. This should provide a 25 to 30 minute duration run with the remaining 3.5 gallons of fuel.

Note: The flight test performance results came within 10% of what my preliminary calculations provided. This was quite satisfying and shows that the math can really work for predicting performance results.

Lots of fun but I am glad it is over,

Hoping for video and photos from the flight crew later this week,

Regards,
Chris
 

Cozyflier

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Waukesha, WI.
The weather and wind was favorable for the one remaining flight test last Friday. After assembly and one turbine test run the HP-18J was pulled out to the runway for the last remaining flight test - the self-launch exercise.

Wind speed and direction was 5 to 10 mph almost right down the runway. I strapped in and powered up the aircraft, extended the turbines and proceeded with the start sequence. Once both turbines were started and stabilized at idle (33,000 RPM) the thumbs up was conveyed to the wing runner. Full power was applied (105,000 RPM) and the takeoff roll was started.

Once the aircraft speed exceeded the wing runners pace the left wing dropped and the roller blade wheel at the end of the wing did its job. Within a short time the ailerons took effect and I was once again level and accelerating towards takeoff speed. The airspeed was climbing rapidly and the tail was next to lift followed shortly by the sailplane takeoff. I stayed in ground effect for a couple of seconds then started my climb.

By the time I crossed the end of the runway I had gained 400'. I continued the climb at 60 to 70 KTS until reaching my goal altitude of 3000' AGL. Upon reaching altitude the engines were shut down, cooled and retracted. I soared for 30 minutes, did some more spin exercises to spend my excess altitude and did one re-lite to verify the restart success for the previous weeks testing. Both turbines started successfully and were shut down after a couple of minutes. I returned to the airport for landing and was greeted by my support crew once I rolled onto the taxiway.

My Oudie flight computer provided all of the finite statistics from the flight. The runway takeoff run was between 850 to 900'. The time to climb to 3000' from a standing start was 4 minutes and 45 seconds. The climb rate from the standing start averaged 631' / minute. Total fuel burn for the takeoff, climb and one restart was 3.5 gallons. Remaining fuel in the header fuel cell was 3.5 gallons.

Anticipated flight sequence. Self-launch and climb to 3k, shut down the turbines and retract. Utilize one engine for sustained flight if needed at reduced throttle. This should provide a 25 to 30 minute duration run with the remaining 3.5 gallons of fuel.

Note: The flight test performance results came within 10% of what my preliminary calculations provided. This was quite satisfying and shows that the math can really work for predicting performance results.

Lots of fun but I am glad it is over,

Hoping for video and photos from the flight crew later this week,

Regards,
Chris




Here are a couple of video links showing the Sailplane while using the turbines.

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.
 
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I stopped by to see the HP-18J at Oshkosh today, and I have to say it is amazing. In terms of build quality and attention to detail and fit and finish, it is probably the nicest homebuilt glider I've ever seen, and is up there among the best of all the homebuilt aircraft I've seen.
 
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