Jet Engines

Don't get me wrong, this is not something I'm even remotely considering. But I'm curious, does anyone know if anybody has ever attempted to put a jet engine into an RV? Is this even possible?

Yes

There is a jet-powered, self launching sailplane and the guy does incredible aerobatic shows with it. It has two small, retractable mini-jets manufactured in the USA. You could sling one under the RV I reckon. This is their site
http://www.usamt.com/
Regards,

This guy can fly with them...wonder the plane weighs.

The most powerful one makes 45 lbs of thrust and weighs only 5.3 lbs - but at $4000 each I'd bet you'd need to spend a lot of cash to get an RV into the air and flying like it was designed to.

I sure would like to see 6 or 8 of those things hanging on the wings of an RV though - would pretty cool if you ask me.

Those are model airplane engines.

Do you need a multi-engine rating for that?

Counting Shafts....

captainron said:

Do you need a multi-engine rating for that?

Click to expand...

One.....Two....yup, looks like a multi to me!!!

From below I think a 315lb thrust engine might work.


**warning below is rough calculations*

I have thought about this. Honda's jet runs off of two HF118 that produce 1,700lbs of thrust each. Max takeoff weight is 9,200lbs. So thats (1,700*2)/9,200= 0.369 power to weight ratio. Max speed is 420kts. Only need about half that for an RV so chop the power/weight ratio by half Brings it down to 0.1845 .

http://en.wikipedia.org/wiki/Honda_Jet

RV max takeoff weight is 1700lbs *0.185 = 315lbs of thrust to get close to the current performance. granted these are pretty gross figures and some sketchy interpolation.

Fuel. 2300lbs(384 gallons) of fuel for a range of 1,100NM
Again using the same interpolation 384*0.369*0.5= 70.8gallons
1100/70.8 = 15.5miles/gallon

Yeah 7-8 of those 45lb engines would do the job, kinda like a B-52 (Although the B-52 is going to only use 4 engines pretty soon)

Wish I could at least try it

Edit: Anyone know of jet engine suppliers besides GE, Rolls Royce etc? Smaller engines but not so small as the ones above.

There are other things to consider with a jet...

An RV is designed to have a propeller pulling th eplane from the front, so you need to have the weight of the engines up there, and I would think you'd also need to thrust from engines being derived from the front of the plane as well. I think you would have a use a setup more like the one I pictured above rather than just haning them off the wings, unless you planned on doing some rather substantial modifications to the airframe to move the wings rearward in order to the CG correct.

Also, I don't know the Rolls-Royce makes much in the name of smaller jet engines. I think your big names are going to be GE, Pratt & Whitney and Williams. Looks like the Honda jet is using engines built by GE as well.

*EDIT* - Looks liks Rolls Royce does make small jets as well...

Now you have seen everything

Jet Hang glider!

http://www.alexisparkinn.com/photogallery/Videos/2006_jetbug_jet_hanglider_.mov

And here is an aerobatic routine of the plane pictured above, Cri-Cri (Cricket) french home built (but with piston engines).

http://www.alexisparkinn.com/photogallery/Videos/2006-10-13-smallesttwinintheworld.wmv

I am pretty jaded watching aerobatics, but that's an impressive roll rate. I would not fly the thing straight -N- level much less roll it on takeoff. Here is the web site for these "world's smallest twin engine planes": http://flight.cz/cricri/english/index.php

Note the pre-shut down run0up to clear the plugs at the end of the video, I love it!!, ha ha, oh my, who says the French don't have a sense of humor. Here is another Cricket stunt: http://flight.cz/cricri/vids/cri5.qt

JETS ANYONE?

May be their is a future for small jet engine GA planes. The very light Bizz jets are coming, like the Eclipse and Honda jet. What engines do we have now for a little personal two seat jet?

The Williams Intl engine (http://www.williams-int.com/high/product/engines/fj33.htm) is the lowest thrust commercial jet engine they make for passenger planes, at 1000 lbs. The fj33 is still too much thrust for a light plane and cost a fortune no doubt. Need something in the 400-600 lb range, that cost no more than a Lycoming and gets great fuel burn. (right)

RC model jet engines top out at 50 lbs of thrust, burning 11 gal/hr, at about $6,000 each, you would need a couple of them; not practical, except for a novelty like Mr Jet Hang Glider or the Cricket dude.

Than I came across something interesting Amtusa. They are making a jet engines for the goverment. It's current thrust is spec'ed at 150-200 lbs, $32,500. Burns 23-31 gal/hr at max thrust (est). Could you get airborne with 200 lbs thrust. May be in a Cricket, not a RV size plane. It's even a little low on thrust for BD-5J, which uses about 300 lbs thrust with a microturbo TRS18: http://www.gasturbine.pwp.blueyonder.co.uk/TRS18.htm.

Are real, affordable, safe, economical personal jet's practical? Probably not. Single engine jets for the GA pilot masses is a dream, at least for now. Reading about the poor (terrifying) history of BD-5J's, I've no desire to fly one.

Here is another high powered jet engine (relative to RC models): http://www.microjeteng.com/hf150.html (150 lbs thrust at 39 gal/hr). They also have a 130 hp turboprop. http://www.microjeteng.com/prop_pics2.html The turbo prop looks like a mini P&W PT6. He uses his gas section to drive a turbine coupled to the prop dirve, meaning its no a direct drive turbine, aka PT6. Interesting.

These cruise missile engines are not man rated. Meaning I would not fly with one. You will not likely ever get over the fuel burn and poor takeoff performance with a small jet.

Want to get scared? Here are links on the BD-5J (jet). There are almost too many accidents to count. Almost every one that has flown, seems to have crashed at some point. The first link starts with a description of a toy model BD-5J, but at to bottom is an impressive list of accidents and links of real BD-5J's. The second (Wikipedia) list three notable BD-5J crashes, two of which tragically both just happened recently in June of this year.

http://www.xs4all.nl/~robdebie/models/bd5.htm (list at bottom of page)
http://en.wikipedia.org/wiki/Bede_BD-5

Little single engine micro jets are not for the GA public, but that's my opinion. From the list of accidents of jet powered BD-5J's (well all BD-5's) it seems like a dangerous way to fly. It remains to be seen what happens when the VLJ's (very light jets) start being flown single pilot by private pilots. Low time inexperienced pilots in jets is a recipe for an accident. Hope that does not happen.


Although the RV is not suited for a jet engine,
here's my jet powered RV project :

Some math for your reading pleasure

At 375 mph, 1 lb of thrust = 1 HP. Note that it's thrust horsepower, not shaft horsepower...the losses in the prop matter. So to calculate how much thrust it takes to propel your airplane at a particular speed, do this:

T = HP x 375 / mph

A 200 HP RV that goes 200 mph TAS @ 75% power and has an 80% efficient prop therefore requires 225 lbs of thrust for cruise. However, if you do the math during a full-throttle climb at 90 mph sea level:

T = (0.8)(200) x 375/90 = 667 lbs of thrust

That's a thrust-to-weight ratio of about 1/3, which is not unlike a bizjet...which is why RVs climb like bizjets. If you sized the engine for cruise, the airplane would climb like an underpowered brick.

Then there's the fuel consumption...model airplane jets have an SFC of about 2 lbs/lb-hr. At 225 lbs of cruise thrust, you'd be burning 450 lbs/hr. A "real" small turbojet has an SFC of about 1 lbs/lb-hr, which means you'd be cruising at 225 lbs/hr (or about 3x what a Lycoming burns).

Note that you won't be going any faster, at least not if you take the Vne limitation seriously.

Math is fun

mgomez said:

Note that you won't be going any faster, at least not if you take the Vne limitation seriously.

Click to expand...

Thanks for the math. love math. Interesting.

That is why a micro jet needs to be designed from the ground up around the engine. It would still climb like a brick as you say if you did not oversize the engine, w/ a basic minimalist thrust engine.

The FJ33 Williams with 1000 lbs of thrust would be nice, but that engine and an airframe that could use it properly would cost in the millions. There are already many used turbo prop and jets you can buy for less than a million. I just saw a nice Lear 24D go for 1/4 mil! If I had some change I'd buy it.

There are laws of scale working here. At some point a turbine does not fit a small planes. If you're going to a turbine you almost have to talk about a larger plane to make use of it. Most practical turboprop engines are +600hp and small turbofans at least 900-1000 lbs, which is what is on the Eclipse. You may recall Williams Intl where dropped due to poor performance for the PW610. The PW610 core is rated up to 3000 lbs thrust, so you can see the laws of scale working. It cost almost as much to make a 900 lb thrust engine as a larger one. Most small business jets have more like 2000 lbs thrust. The new Citation Mustang has 2x1500 lb PW615, and is a larger plane than the eclipse. The rest of the Citations are 2000 lb thrust and up. It just shows the min economics of making a turbines.

Piston engines fit small GA planes for personal use very well, where high average yearly utilization is less than 200 hrs. You can buy a Lyc for $20k, burn 9 gal/hr, build and maintain it yourself if you want, and people still complain about that.

If you can afford a turbine plane you'd buy one. I guess the closest thing we have is the PropJet Lancair. My understanding is the build cost is about 1/2 mil, with a used Walter turboprop. If you have to ask about fuel cost than you can't afford one. There has to be a tax right off in there somewhere for individuals and companies to make it work.

Even the rich & famous are not owning their own jets anymore; they are going to the co-op's, like Flexjet for obvious reasons. You suck a bird into your engine, your plane is down for a significant amount of time and its going to cost you hundreds of thousands of dollars to fix it. With FlexJet you land and they call out another plane for you, no extra charge.

It remains to be seen if the VLJ's is a boom or bust. They are small 6,000 lb planes with small cabins and limited range. Older Citations and Lear's have more performance and cost less used than newer VLJ's. However the idea is with their modern technology, VLJ's operating cost are suppose to be much less. Plus the owner/pilot, single pilot, private license aspect saves on crew cost. Older turboprops and bizz jets cost in fuel and probably in maintenance. The price of the Eclipse today is around 1.6 mil and the wait is a few years. When you close the deal at delivery the price will be adjusted (up) for inflation.

People have tried to make and market tiny jets but they never caught on. There was the Paris Jet, 4-seater and a few others, but the MATH did not work out. There is just NO way to do a plane turbine right, cheaply. I have a new found respect for the Lycoming.

Foxjet

Anybody remember the foxjet? Similar idea to today's VLJ even planned on williams engines like the initial eclipse. There are few truly new ideas in aviation it all comes down to execution and marketing. Seems like the ball is rolling pretty good now. I sure would like to be able to get a used VLJ some day for the price of a used barron.

http://www.machdiamonds.com/foxjet.html

Regards

I think the problem with small jets is not the making of them - any one of the big turbine manufacturers could come up with a 600lb thrust engine in a few hours if they had to. It's the fuel burn that kills them. They just aren't economical until they make huge power and carry a lot of people.

There's a company out there called Maverick that's gearing up to make some personal jets, but the cheapest one is a single-engined 5 seater at $1.2 million.

The problem is that there are two types of VERY good competitors out there - it's not big deal to get 6 or 8 people on a turbo-prop or even a twin that performs almost as well small jets.

Unfortunately they probably will never fly

xl1200r said:

I think the problem with small jets is not the making of them - any one of the big turbine manufacturers could come up with a 600lb thrust engine in a few hours if they had to. It's the fuel burn that kills them. They just aren't economical until they make huge power and carry a lot of people.

There's a company out there called Maverick that's gearing up to make some personal jets, but the cheapest one is a single-engined 5 seater at $1.2 million.

The problem is that there are two types of VERY good competitors out there - it's not big deal to get 6 or 8 people on a turbo-prop or even a twin that performs almost as well small jets.

Click to expand...

The prototype twin engined Maverick Air jet crashed in 2003. I see they now have three planes on the drawing board, a single engine jet, a twin and a seaplane jet! Here is their site: http://www.maverickjets.com/index.php I wounder if they ever get anything flying again. The new designs look nothing like the Maverick I.

The other one, Excel-Jet, which was a single engine jet, showed promise but crashed in Colorado in the last year, killing two of the companies principles, possibly from wake turbulence. http://www.sport-jet.com/. Status, looks like they have another flying prototype, cool. About 0.98 mil "experimental" and 1.3 mil for a certified one in 2-3 years; A single engine jet has appeal, but most serious Bizz jets are twins for many reasons, not the least is redundancy and safety. However I do think the single engine excel-jet is cool design at a cost of 1 mil. It would be an option for the (rich) individual. If I was going to a jet I would by a used Citation I or II. You can get one tomorrow and they cost the same as one of these toy jets. Cessna of course has been around and service is available.

Turboprops are good for short trips and runways, jets longer trips and runways. in general. Turboprops are more efficient at lower altitudes and a jet needs longer trips to climb and have time at altitude, where it's more efficient to be optimal. There will always be room for turboprops, kingairs and C130's, however turbojets are smooth and props noisy and not as smooth. Both have economics and optimal missions. Thats why a jet is not a good choice for a little flying holes in the sky fun planes, they are made to get-up and go somewhere at least 500 nm away. A sport plane, $100 hamberger getting or going up to get away, going no where for any reason except for fun of flying, pistons -N- props do that nicely.

I think you missed my point. Yes manufactures can make a 600 lb turbine and do. The little 300-600 lb thrust missile engines are maxed out. To take the next leap in thrust for a jet engine, that's really safe, economic and reliable takes sophistication. Once you go past that plateau of 300-400 lbs, its a quantum leap in complexity and cost. Now that you have a bigger "core", making it either 1000 lbs thrust or 3000 lbs is not significant. Also the market just calls for engines that are at least 1000 lbs thrust. Now you could derate a 1000lb thrust engine, but its still a 1000-3000 lb core. The little missile engine are 200 lb thrust engine that are straining to put out 300 lbs. That may be part of the reason BD-5J's have such a bad safety history?

The Eclipse is a very very small jet and has two 900 lb thrust engines. Its cabin is smaller than many piston twins. The same PW610's can grow to 3,000 lbs thrust. The little engines at 900 lbs will probably last at that lower thrust.

Often a manufacture "core" has a range of power. The engine is really the same. Where the PW610 that makes 900 lbs on the Eclipse, it can make 3000 lb with a different fan, but the basic core design is similar. Having a jet that runs at the lower end of its temp and pressure limits will mean it last and be super reliable.

A single engine jet, like the the Excel or the Maverick "solo" concept with one the larger engine like a JT15 (3350 lb) would be cool. The Citation II had 2,200 lb thrust JT15A's. The later Citation V which had 3,000 lb JT15D's. I flew both. Nice planes and good engines. You can get a old Citation I for a little over a Mil. An old jet is still a jet.

As mgomez pointed out you need excess thrust to get off the ground, climb and lift usable payload. Yes you can fly a jet powered hang glider, but its not practical. The idea is climb high and save fuel. That is why total thrust of 1800-2000 lbs is about min. for any practical size personal jet that can carry at least 4 people. Remember you have to carry more fuel, which takes more structural weight and so on. Again scale.

The sad safety history of the 300lb-450lb thrust BD-5J microjets makes me think that its just too small. The engine is too small and the plane is too small. Again scale. At some point turbines, jet or prop are not practical for a small light plane.

If the LSJ makes it, they predict several thousand flying by year 2017. Next down is the single engine turboprops. Any way you cut it, a turbine is big bucks and out of reach of all but the very rich.

The little cruise missle engine that was in the Fly-market at Sun 'n Fun about six years ago was just about the coolest thing I ever saw. As I recall, it was from a Boeing AGM-86 air-launched cruise missle, was a Williams engine, and I think it is a 600 lb thrust engine. That inspired a lot of daydreaming.

http://www.hill.af.mil/museum/photos/coldwar/williams.htm