Rutan's Bommerang-like high altitude twin STOL concept?

Hi everyone,

What's your thoughts on the conceptual design of a high altitude twin STOL airplane using the twin safety method of Rutan's bommerang? This airplane would be specifically used in Tibetan-like area for observation, search and rescue, supply and medivac. Like the old saying about bush flying:"Fly an hour or walk a week." so speed is the least concern of this airplane, but superior high altitude STOL performance would be the first priority. The performance requirement list would be like:
1. able to take off and land within 700 feet or 200 meters at 13000 feet or 4000 meters.
2. twin engine. Ignore the single and twin safety argument. When you fly at that altitude around that terrain, you want a twin. Single engine out controllability must be as good as possible. What about in-line push pull twin configuration compared with Rutan’s Boomerang?
3. three-person useful load capability.
4. 2.5 hour fuel capability is enough for the mission.
5. 100mph cruise speed is more than enough really, even 80mph is OK, considering you can only drive at 30mph on the ground--not in a direct route like in the air.
6. very tough landing gear.

We have this airplane dream because we believe all the people have the rights to have the convenience of air support no matter where he or she lives and how much he or she earns or which ethnic group he or she belongs to.
Please don’t recommend a turbine airplane model. We simply couldn’t afford to use it.

Thank you

Xin Gou
Chengdu, China

 

I would go for an inline configuration (like the C337). For high altitude performance you need massive HP, or a much larger wing. A fairly high aspect ratio helps a lot in improving climb performance.

As for existing designs, something like the Aircam with more affordable engines and a closed cockpit might make a lot of sense.

 

in-line twin engine configuration is the easiest way, but its disadvantages are obvious too: low efficiency(quite serious for this type of mission) and rear prop clearance on the ground.

 

It's ugly, but I'd be tempted to start with this

Transavia PL-12 Airtruk - Wikipedia, the free encyclopedia

and find a way to make it a twin with turbo normalized engines.

 

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How about an autogyro?

 

yeah, actually I am thinking autogyro seriously especially studying the modern European design. Autogyro is very resistant to cross wind and turbulence which is very useful for the mountain flying. The problem is no twin autogyro design.

 

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I described the exact mission you do in a previous post --Alex Zahnd is bringing modern technological solutions to the people of Humla province (most remote and over 4000 m altitude ) --things like PV solar cells, stream turbines even metal pots and window glass - all bought on human backs from the nearest track 18 days walk away.

I cannot see how Rutan's high speed Boomerang relates to this task and you still have to find somewhere to land which is not likely at this altitude as every bit of horizontal space (very little) is needed and used to grow food --the solution needs ATOL and an aircraft designed to ALLOW very low wing and span loadings and no copy of an existing design will do it . The government of Nepal was the first obstacle as the Maoist insurgents were still the major security problem and only very few tourist flights were permitted (see "world's most dangerous airport" thread on HBA for the available airport ) --Rutan did not pay much attention to short field operation and only the one off Grizzly came anywhere near to being feasible and it was unsatisfactory (as was the predator ag aircraft designed for similar ops )

 

You miss the point Aircar... he wants a SSTOL twin with asymmetry ala the Boomerang to help with engine-out-on-takeoff scenarios. Not a slick, fast, plane.

Something like a little larger Just Aircraft SuperSTOL with 29s would fit the bill with two 80 hp turbo HKS engines. Very little runway needed with this design.

https://www.youtube.com/watch?v=DFJJvFtbdV4

(this video is with 100 hp at Sun-n-Fun where they wouldn't let Troy do "high performance" landings)

 

thank you Harrisonaero for the clarification. That's right: I just hope to borrow the Boomerang's single engine out safety feature in the design. Could that be possibly done?

 

Correction to the correction- no I don't miss the point . As in any specific design of a flying machine you are constrained by immutable geometric facts to what a thing can do and if that involves extremely slow landing (in GROUNDSPEED terms @ 4000 metres alt ) then you will run into 'inconvenient truths' like trying to impose a very high lift airfoil system onto an airframe that uses the forward engines to do the primary balance and has the layout it does as a conseqeunce (eg you cannot just throw out some massive amount of wing area or fancy flaps from the trailing edge and not expect to just plunge into the ground with the stick in your guts . As they say' do the maths' -air density is about 2/3 rds of sea level if I remember my design investigation . The Configuration of the Rutan 'Pond Racer' is similarly 'safe' for thrust loss but neither are nearly as good as centreline thrust as already noted --maybe you should think about a hyrbid since at least you don't have TWO engines gasping for breath and putting out half power at 14000 ft. (nevertheless engine failure was not kind to the Pond- neither configuration was invented by Burt just for the record.) There are some IMPOSED constraints that just about rule out any significant morphing with twin fuselages (or triples)

And where are you going to land ? -just being on one side of the same valley compared to the village you are trying to get two can mean DAYS of mountain climbing in thin air --- if you really want to help those that are inaccessible it needs to account for their actual circumstances and the degradation of both lifting power and propulsive power at such altitude .

As stated before this task IS doable but has to be approached from first principles and a bit of study /experiment/experience -- just in passing, there are birds that fly over Mt Everest but they are not the ones that can land or take off from these heights as another example of the optimizing needed. (or just to work at all --what would be the take off run of the Terrafugia at 14000ft I wonder -easily calculated of course )

 

Why bother with the math? Just break out the tape measure and measure to the edge of the cliff!

 

Electric motors have same power at 14,000 feet as at sea level.
Might be cheaper than turbos, if only brief excursions of electric boost are needed.

 

aircar thank you for the comment. I will keep alert of the circumstances for sure. I am looking at the autogyro seriously now for its much better resistance to gusty and cross wind. Climb rate is important, but wind resistant capability is even more important considering the mountain and altitude conditions. As for hybrid engine, it's a good thought, but it'd be much easier and less costly to turbo an engine especially thinking about the battery weight and cost. I've seen a modified Rotax 914 with full power at least up to 5000 meters.

 

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I certainly wish the Honda CRV 2.0 I recently had around Shangri-La (thats the real Sichuan Shangri-La Mountain, not the fake Yunnan Shangri-La!) at 5000 meters had a turbo, man was it struggling, literally wouldn't move from a stop sometimes.

 

Since speed is not a priority, why not a blimp/airplane hybrid? I'm envisioning a large, thick, high aspect delta shaped wing filled with helium that will support about 1/2 the total weight atop a somewhat conventional fuselage with a single tractor engine.

 

You're balancing a few things. Tolerant to high winds, steep climb angles, slow landing speed (TAS!) etc.
A blimp is sensitive enough for wind to be pretty unpractical I'd think. Something like a Breezy/Aircam configuration with a huge wing and efficient flaps seems like the best approach.

 

gouxin,
How many place is this aircraft you are talking about? An autogyro is perfect for mountain flying if speed is not a primary objective. Also keep in mind that beside, multi-engine (for your requirement), you might need a more-than-two-blade rotor, which is more complicated and more expansive.

 

I was having a conversation turned argument with a former Airforce PJ after I asked what he thought about using light aircraft to support special ops, as they did in Vietnam. I brought up that you could buy 32-128 brand new GA aircraft for the cost of one blackhawk, but he quickly changed the subject to mountain rescue. He pulls out a distinguished flying cross he says he got on Mt. McKinley, and that no piper could rescue someone that high up. Regardless that it was completely off topic, I responded "Hate to tell you this, but someone rescued a climber on that very same mountain, decades before you did, and with a piper cub." Still not wanting to be outdone, he said a piper could never land where a blackhawk could, to which I showed him the blackhawk manual, which states a minimum of 100ft clearance from the blades. That makes the 50ft clearance of the supercub, and the landing area of the blackhawk almost identical. I dont think I ever saw a real life example of such a one sided argument being turned around so badly on someone.

Moral of the story, the cub is an excellent example to use when looking at mountain aircraft. Anything with a thicker wing would have insane bush performance.

That said, if you want the takeoff performance, want twin engines in an inline arrangement, and amphibious, you could base it off of a Lake-200 series. The Lake is faster than a similarly equipped Cessna 172SP, and has better payload, and an overhead engine, so the fuselage is a good starting point. If you equipped it with a thick enough wing to bring it down to the speed of the super-cub, it would be extremely thick and have insane lifting ability. On top of that, a raised wing could be used to create a crescent shape "tunnel wing" under the engines, as used in the extreme STOL Custer CCW-5 - Wikipedia, the free encyclopedia

This would produce something similar to this badly photoshopped image of a LA-200 that I just made. :gig: