Poll: Extremely light jets, a new homebuilt market segment?

Greetings David

Personally,  I'm not all that concerned about jet designs as I am about turbine and jet propulsion for existing designs. Sure, it would be nice to have something like a Javelin  with my name on it, but I think it would be great to put a turbine into any prop plane too, especially with all of the 100LL concerns. It's a great time to explore that avenue. Some one with the resources to develop a small, efficient, and relatively low cost (under $6,000) turbine/jet/turbofan could make a killing in the homebuild marketplace.

~Jon

I think that there would be a market for a 2 place. Im not so sure about a single place. Would love to see a small 160HP Turbo-prop available

The problem with anything jet, in terms of homebuilding, seems to be the cost of the powerplant.  If someone came out with a small turbofan in the 300-500 lb thrust range that cost less than $20,000 then I think you'd see a whole new category of aircraft born.

Imagine a modern interpretation of the SIPA S.200 Minijet or the tandem-seat S.300 (links not working for me, see <http://www.machdiamonds.com/s200.html>) but with lightweight composite materials and a more fuel-efficient engine.  Those planes had marginal performance, especially in the climb, using 1950s technology.  Knock a couple of hundred pounds of weight from the structure and reduce the fuel load for the same range and that marginal climb rate would go up dramatically and I think they would sell like hotcakes.

Of course, in this economy, low-cost ultralights are probably a better idea...

 Thanks a lot for your respones, keep sending them if you read the poll !

What I learn from the responses till now is:

Could be a market for it, I've had a high reply rate for the number of views until now, compared to other topics on the forum. So the interest is out there.

If possible should be a two seat. I agree, although building cost go up more quickly for a two seat than a smaller single seat aircraft. As a first guess the $200,000-$250,000 mentioned would not be far off, lets say it compares to a Lancair Legacy. A single seat could be build for probably less than one third that number, which is much more affordable for a lot of people.

There are a number of small (micro)turbines available on the market (look at the SubSonex) with reasonable good specific fuel consumption numbers. Although getting a 1000 Nm range would not be realistic. 500 Nm would be a more doable number, which is not to bad?

After all it's having the fun of flying the airplane and doing aerobatics with it. With modern composites you can have thrust to weight ratios of about 1 to 3 or 1 to 4. So the prformance will certainly be there.

Again thanks a lot for the replies, looking forward to receiving more opinions, also from other people.

David

I'd be very interested, though I'd be more inclined to support a more cross-country capable machine. 500nm would make for some short legs in a fast bird, but if it could be nudged a bit closer to the 1k mark I'd be happy with it. I'd prefer a 2-seat plane, but a single seater would have some utility for me, as frequently my family and I aren't able to fully synch our time off, so it'd be nice to be able to zip off to meet them for a weekend in Niagara or where my folks are, in NM.

The developement of micro jets may be a leap. However, affordable micro gas turbines have been around for most of the last decade. I'm talking about the Solar T-62. It was procured by the US for use as an APU for everything from the CH-47 to the M-1 tank. Called the "little Joe."They came on the market when they were replaced rather than be overhauled.

About 2004, an aquaintance in south Loisianna began buying run-outs when they came on the market. He overhauled them with new and surprisingly inexpensive hot end parts. He upgraded some of the bearings so that they could function as thrust bearings. He invented a simple, effective fuel control which he manufactured in his shop. I was flying Sikorskys about 2 miles from his shop and was invited to visit. He had about a dozen under conversion, some ready to ship. One was going to one of our "Igor" pilots who had a BD-5 project, who was also an A&P.  I forget his price but it was very reasonable.

Joe replaced the VW with one of his tubines in a KR-2 taildragger that he bought. Later, one of our Maint Techs helped Joe convert it to a nosewheel. I examined it in his shop and was awed with the propeller. It was a simple mechanical device where the cockpit control directly changed the pitch and the turbine governor commanded an adjustment on the simple fuel control. Any turbine pilot will find this familiar.

Joe was a marine maintanance tech and machinist for a local company that chartered supply vessels to the energy industry. He was the trouble shooter that was dispatched world wide on short notice. Joe was no hack.

No, sadly Joe cannot sell you a zero time FWF turbine. This is the link to his NTSB report. I was told that he was only a student pilot. The accident airport, L49 has since been redesignated to GAO. The T-62 was a success. It put out 100 HP plus and was very, very dependable. The KR-2 was a much lighter, hotter plane after the VW was replaced. In fact an eye witness said it went vertical. The Docket number is DFW05LA129 on or about May 21, 2005. All who know him were stunned and heartbroken.

http://ntsb.gov/ntsb/brief.asp?ev_id=20050527X00684&key=1

Bob

While it would be possible to build a jet aircraft as a homebuilt, it really really should NOT be done without some experience.

  Building jet airplanes or even turboprops are an order of magnitude (some might say several orders of magnitude) tougher than high performance complex aircraft.  Jets imply flying high and at speed and now you get into aerodynamic limits, mach tuck, pressurization, high pressure hydraulics, flight control flutter, structural flutter, aerodyanamic stiffness, the list goes on.  You also need redundancies in some of these systems so weight and cost become significant. Just compare FAR23 to FAR25 which is where most jets are certified and  you'll see the complexities involved.  

I too wish for a small turbo prop that could deliver 160 to 200 HP up to say FL250 and I think that would be a nice engine to have.  If the design life was 3000 hours and had a price of say 60K I'd be all over that like a bad coat of paint.  But they don't make one...

Joanne, have you seen the PBS TP 100 engine? Being developed by the same company that is producing the TJ 100 microjet that was selected for the Subsonex and Bob Carlton's jet glider The turbojets are quoted at 40K, haven't seen any pricing on the turboprops. 

http://www.pbsvb.cz/pdf/dlt_motor_tp100/en_tp-100.pdf

to answer the original question, I am very interested in the potential of the PBS TP 100 to power light aircraft.   My desire is for  a 2 seat aircraft that's relatively easy to fly.

I just don't see much of a market for a jet kit.

If memory serves me, this has come up before, though not necessarily in 'kit' form and they weren't called extremely light jets. A few years back, there was much ado about "Very Light Jets" (VLJs) and how the FAA would need new equipment and procedures just to have a chance to manage the thousands and thousands of VLJs that were to "darken the skies". 

I don't know how much money the FAA actually got, I only know that I'm not dodging VLJs daily. In fact, I've only seen one up close. One. Perhaps the FAA's new equipment might yet prove useful if the drones "darken the skies"... 

This is a subject near and dear to my heart. As I have designed a small jet based upon micro turbines. Single seat, twin 80lb thrust turbines. Thrust to weight of about .25, so also very small and light. I must disagree with Joanne's assessment that jet aircraft are more complicated to design. Actually, as I got into the design, I kept thinking, "thank goodness I am designing a jet, those propeller aircraft are much more complicated from a design standpoint." Now in fairness to her, I must add that my design is simple, only cruises in theory at mach .42, and is limited below FL250, so I am not dealing with hydraulics, pressurization, mach tuck, structural flutter, or aeroelasticity.

The biggest problems I have had, besides funding, is keeping up with the turbine makers going out of business almost faster than I can redesign. I built my scale RC model and flew it to verify the basic design and I still hope someday to build the real plane.

On a couple of other points. There are turbines in existence in the thrust range of interest, unfortunately they are unavailable to the public as they were all built for DARPA projects or cruise missiles. The cruise missile motors are really almost too high of thrust for most designs, 700-800 lbt, and of course Williams will tell you they are not "man rated". They have other engines in their inventory, but alas they will not part with them or make them available to the intrepid few who might like to give it a go.

Todd Parker

I am rather enamoured of the idea of a small jet  home or kitbuilt plane as well. I appreciate the simplicity of a turbofan or turbojet, particularly when married with a FADEC control system.  

 Things like Bob Carlton's Jet sailplane, which is territory tread nearly 50 years ago by the likes of the Fouga Sylphe/Cyclone: http://aircraftwalkaround.hobbyvista.com/sylphe/sylphe.htm 

Or if I really want to get excited, I can imagine a smaller version of a Yak-15/17/23 early jet fighter. Perhaps around the size of  Beech Mentor or DH chipmunk airframe, maybe smaller.  Straight-winged of course so I don't kill myself.

http://www.aviastar.org/air/russia/yak-23.php 

 I think the great majority  of us don't want speed above 200knts or anything, but just want to have fun spinning a turbine, burning kerosine and maybe having an engine whose performance does not fall off markedly as we go towards 10,000 feet.

I think if someone was able to produce a tubine/turboprop engine that put out similar power to lets say an io-540 or greater, for around what one of those engines costs new, there would really be a market for it.  Like someone said, with a target price around 60k and enough power to toss around a 4 place aircraft (or make a 2 place aircraft scream) it would be awesome!!

How long have turbine engines been around and they haven't taken over the market just goes to show how slow aviation moves...especially in the GA sector

My dream would be a Hummingbird Helicopter with a nice turboshaft engine in it

I think the closest this has come to reality was the Innodyn project - to put a turbine on a plane like an RV.   Unfortunately, despite being at multiple AirVentures with mockups, and the concept sounding pretty good, it never got off the ground, figuratively speaking.

 The question I always come back to when entertaining ideas like this is that of pilot certification. How does one get permission to fly a homebuilt jet, especially a one-off design? Getting typed in a unique turbine aircraft isn't the same as getting typed in a Citation, I would imagine. Does the FAA typically (typically = BD-5J I guess?) require X turbine hours + book work?

-Tony

Tony,

The FAA does not require type-certification for any experimental aircraft. No matter which experimental you build or buy, you just need a private pilot's license. If you are going to fly it above 18,000 feet, you'll need an instrument rating. If you have both of these, you are legal to fly any experimental aircraft from a Super Cub replica to the Space Shuttle!

Of course, just because the FAA allows it doesn't make it smart or safe. A sensible pilot will require of himself an appropriate training program.

Reiff