A method to produce homebuilt aircraft by using existing components differently

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karoliina.t.salminen

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We once had a discussion couple of years ago with couple of aircraft builders at SIL Talvipäivät (equivalent of EAA Finland, and a yearly gathering of experimental builders and enthusiasts, much smaller scale than EAA though) about my specifications for the personal HALE-cruiser/personal globetrotting machine. This is hypothetical speculation and should not be taken as a promise of any kind to do any of this.

- We know that any wing at positive angle of attack will provide lift.
- We know that aircraft will fly with any wing provided that the CG location is correct and there is enough tail volume
- There is no such thing that a certain wing will work on this aircraft or this aircraft class only. The wing will work always, but the question is about optimality of the such design. Obviously optimality gets sacrificed when not using components designed for purpose.
- But this idea also mitigates (in configuration) some of the problems associated for using components not designed for purpose, ie. stall is mitigated by ensuring that rear wing will never stall and forward wing stalls always first.

So I presented my specifications on what I want. And we discussed about a crazy idea how to make a plane that meets
this criteria quickly with skipping design and fabrication of certain major components. The resulting plane would not be optimal
and it would not be as good as purposely designed for the purpose, but we thought out that:

- Buy two sailplanes, salvage their wings.
- Build a fuselage only
- Join the two wings of the sailplanes with the new fuselage like in Rutan Proteus, ending up a tandem wing with
each wing carrying roughly 50% of the load (or the forward wing a little more than the rear wing).
- Reduce the length of the forward wing a bit and replace flaps with the canard-type elevator mechanism.
- The rear wing's ailerons would be reused as ailerons
- Add vertical surfaces with booms like Proteus
- Add landing gear (like in Proteus, rear gears in the roots of the tail booms and the front gear in the fuselage)
- Reuse water ballast tanks as fuel tanks
- The fuel would be located unoptimally in relation of the CG, but it would not be hard to make a software that would
pump the fuel evenly from the tanks to ensure that the CG remains in the same location through the flight envelope.
- Add engine/engines and props

I was sceptical at the time about the idea, but I have been thinking it that actually it could make sense.
The sailplane wings have one not so good thing though, they have the optimum L/D optimised to high Cl/angle of attack,
which is typically unoptimal for a motor plane. However, the HALE thing would account for that, the plane
could fly at high altitude with relatively high angle of attack much nearer to optimal L/D with low IAS, but the
altitude would make the low IAS to reasonable true airspeed and actually the plane would cover distances without
going so fast in IAS.

This is not my plan and this is not exactly what I am going to do (at least have not decided anything like this currently),
but this was a speculation. Plan A is self-designed system from grounds up but this was discussed as a potential shortcut ticket.
So I would like to hear your opinion if it was good speculation or bad speculation or indifferent speculation.
We discussed this circa 8 years ago and did some rough estimation that it would probably just meet my specifications
despite of all the compromises made. Two sailplane wings with a low drag fuselage would still be low drag and especially low
induced drag vs. the more low aspect ratio typical planes. Since this would be a high altitude craft, the two wings would make
its wing loading low which would be advantageous for high altitude flight. The low wing loading would be also advantageous for
low landing and takeoff speed, and for optimising the cruise power as low as possible (ie it would be cruised at very low percentage
power, like 20% power vs a typical GA plane like DA40 that we cruise at 40-50% power as the Lycosaurus is unsuitable for lower power
setting as the SFC curve gets worse and 5.5 gallons per hour is the lowest we can get on it in cruise and also the DA40 is unsuitable
from aerodynamics standpoint for lower power cruise than that as the induced drag rises as the nose gets too much up, hence
suitable engines would be car or motorcycle engines with a hybrid system for transmission (ie not need to match prop rotation speeds
and engine power and engine rpm, and variable rpm for the props for the high altitude flight (ie high rpm at high altitude, low rpm at low altitude)).

And then one more thing to add, how to route the controls from the cockpit to the control surfaces: easy. There would be no pushrods, but just cablings and there would be servo motors on each control surface actually turning them. The stability would be augmented with software and it would be possible to move the CG a little bit aft (to a neutral position at least) during cruise for better efficiency by pumping more fuel from the forward wing than the rear wing, and end up later with a CG that is again positively stable for landing. Like sailplanes can release water ballast, in emergency, the fuel would have to be released quickly and the design would have such CG location that the plane with empty tanks would be at positively stable CG location.

Typical water ballast capacity is 190 litres per wing. Two wings = 380 litres. The 380 litres should last for 5500 km range. That would call for 6.9 litres per 100 km efficiency. I think better could be reached quite easily at high altitude high L/D cruise, exceeding Toyota Prius mpg would be the target. This is not so far fetched target as the DA40 already is more efficient in cruise than an SUV.

The tandem wing configuration makes it possible to use sailplane wings intended for lighter aircraft, to be used
in a heavier aircraft because the load is shared between the two wings. The resulting aircraft would not be optimal
in aerodynamics nor optimal in structures probably, but we discussed that reuse of components would allow potentially faster
and more likely completion for otherwise very ambitious project.
 
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DangerZone

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Any parameters that you could input?

Like, which wings you have the chance to buy affordably, their wingspan, materials, wingspars, ways to shorten the 'canard' wing in the tandem, their mass and G tolerance, etc? There could be a problem because these wings will be designed for one mass and your aircraft would have a higher mass. This might lead to a structural problem since loads don't divide linearly in a tandem wing aircraft like people mathematically expect.

Then the powerplants, which engines would you use and what kind of fuel? Would you go for twin engines or keep the mass low with a single one? Pusher, tractor or midfuselage/midwing? Retractable props or not?

Seating configuration, tandem (4 in a row, possible in such tandem wings) or 2 and 2, or 1 pilot and 2 plus one in the back? Twin flying wing maybe, all four seated/lying in the leading edge for a frontal view?

More information might help to see all aspects of your idea...
 

DaveD

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I'd be worried about repurposing ballast tanks for fuel storage, most composites are resistant to water, but that is not always the case for fuel!!
 

karoliina.t.salminen

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DangerZone: I do not have answers to your questions because I have not seriously contemplated on this project, this was just an idea. This is similar to my plan A idea where the main difference is that it has purpose designed and not reused components. So therefore I have not checked what the sailplane wings would actually cost and if these are available at any price.

Seating configuration 2+2 with wider cabin than DA40, otherwise similar dimensions. Rear seats could be replaced on globetrotting with something else (like survival equipment) that needs to be carried around, and might involve (or not) removal of the rear seats and dedicating that as a cargo area.

Basically the layout of the fuselage would be such that the rear seats or cargo area would end up in the CG, similarly than the cargo area in the Rutan Proteus,
that is behind its cockpit and its interchangeable component. In this design the middle portion does not need to be interchangeable as the purpose is very different,
but anyway would be located there. ICEs would probably be located into this location as well or at least one engine at that location, maybe another in the nose, maybe.
I have been thinking of two engines for redundancy. I would place the props to the leading edge of the rear wing because the rear wing is already in turbulent flow and placing the props behind the rear wing would make probably no difference to the airflow the rear wing sees in terms of drag, and the electric motors would be hence closer to the CG (and not that far behind the CG as they would be if they were pushers). The engines would have hence electric transmission and no props bolted on them.

For weight I would prefer two motorcycle engines, for practicality, I would prefer two diesel engines.

Props would not be retractable but they could be folding if it turns out relevant.

Basically same configuration as Rutan Proteus, no big differences. Except no jet engines and instead with props, and sans
those Proteus features that were designed for its purpose (as a communication system whatnot) or its interchangeable middle fuselage as this case would be much simpler, and also the craft as a whole could be smaller than the Proteus.
 
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DangerZone

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...
I have been thinking of two engines for redundancy. I would place the props to the leading edge of the rear wing because the rear wing is already in turbulent flow and placing the props behind the rear wing would make probably no difference to the airflow the rear wing sees in terms of drag, and the electric motors would be hence closer to the CG (and not that far behind the CG as they would be if they were pushers). The engines would have hence electric transmission and no props bolted on them.

For weight I would prefer two motorcycle engines, for practicality, I would prefer two diesel engines.

Props would not be retractable but they could be folding if it turns out relevant.

Basically same configuration as Rutan Proteus, no big differences. Except no jet engines and instead with props, and sans
those Proteus features that were designed for its purpose (as a communication system whatnot) or its interchangeable middle fuselage as this case would be much simpler, and also the craft as a whole could be smaller than the Proteus.
What you could do to reduce weight is to have two stacked electric motors on each wing and then have a drive shaft on centrifugal clutches to turn the electric motors. Thus when operating on electric power the shaft is still but when you want to enhance the range you fire the motorcycle engine, the engine sprocket drives the chain around the shaft (the other sprocket is mounted on the shaft) to the desired rpm for best cruise efficiency. Sprockets are cheap and very reliable but the most important thing is that you get to keep the gearbox to have finer adjustment if needed. This would reduce time and most of these parts (motors, engines, shaft, sprockets, chains) are readily available for motorcycle use. You would have to turbocharge the engine to be able to get to FL300 or so. An engine with a well cooled and oiled cylinder head is necessary, you might wanna have a look at Suzuki GSX-R or Kawasaki ZX-R one liter plus engines. Count to have an intercooler and place where it will be situated to have good cooling of both the oil and water radiators AND the turbocharger and intercooler. If you would put the engines in the pusher configuration under the trailing line or above the canards, you could have less turbulent drag on the wings and use foldable prop blades (readily available). Another smart idea would be to offset the wings, canard as highwing and rear wing as low, OR like in the Miles Libelula case the other way around. By smart designing you could completely get rid of one wing getting in the wake of the other. If kept realtively light, you might have pretty decent performance with only two electric motors and one GSXR or ZXR engine of 1000ccm&+.
 

Himat

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First two general comments:
- Traveling 5000km in a two seat light plane is not for everyone, at least not for me. Even if flying supersonic that is several hours in a rather cramped cockpit.
- Air traffic control might have an opinion on cruising a slow light plane at high altitude.

As for the reuse of parts, when designing prototypes there is a long tradition for this. Of the more recent ones both the X29 and the EAP incorporated large parts sourced from other airplanes. Trying to make a useful plane for other than research is not that easy, one failure that comes to mind is the Fisher XP75 fighter.

When it comes to light planes, the Volmer Sportsman did use wings from an Aeronca. Same story with other designs I think. To use components from another airplane is probably a viable option, the question arise when the overall design is very different.

One last ting when it comes to composite airplanes. One expensive and time consuming part is the mold. Reusing only the molds, the internal structure can be redesigned to suit the new application.
 

karoliina.t.salminen

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First two general comments:
- Traveling 5000km in a two seat light plane is not for everyone, at least not for me. Even if flying supersonic that is several hours in a rather cramped cockpit.
The range does not mean that landings in between could not be done or should not be done.
It just enables continuing travel without refueling. There are many places in the World outside of USA,
where one can stop but can not get fuel. So the specification supports the mode of traveling hops like with any plane, but
not fueling the plane where it can not be. For our travels we have needed to take canisters to cockpit sometimes to fill the tanks
to get back from some place without fuel. Not very nice, not very proper, and not so safe either. In arctic these places are the
norm, and not the exception. I happen to like seeing places in the artic.

A normal range is good for planes which are used only in USA, central Europe or southern Canada. For example Northern Canada is out of reach
for normal planes or requires complicated preparations, like pre-purchased barrels of fuel to a location and then hoping the barrel is there
(could happen that it isn't). Same goes for Asia, traveling there might be no problem, but AVGAS, only dream about it. And then it could be that some big place that would have fuel, is so corrupt that you have to pay the price of the aircraft to get back into air because they would expect you to be some rich person because you are flying a plane. These kind of problems do not exist in the West (USA or Europe or everything in between, this is the civilized side of the World).

There is only one hop where this long endurance would be necessary to fly non-stop: from Europe to India. Everything in between is not a good place to land. And according to some colleagues from India, one has to be careful there too to not end up paying to some corrupt airport manager a lot.

Some places in the arctic has JET-A but no AVGAS. One notable example is Honningsvag where we traveled, but it is not the only and last place here in Europe, more and more places will be serving Jetfuel only.

- Air traffic control might have an opinion on cruising a slow light plane at high altitude.
I think the air traffic control is a lesser problem than the regulations and the inability to meet them with the light plane.
Burt Rutan circumvented that by only crossing these altitudes and going straight to 65000 ft. However, that was Burt Rutan and the altitude was 65000 ft. For ICE it would require two or three turbochargers in cascade and intercoolers to achieve that altitude, and that altitude flight could become more realistic with hydrogen fuel cell flight than fighting with the ICE that is not getting enough air. This would be highly interesting for myself as well, but as a step one my expertise currently is not enough for dealing with the complicated turbocharger-intercooler install required for that. So I would rather opt for a simpler solution and airframe that is capable for the high altitude flight later if the enablers for it in the terms of power source can be later met.

As for the reuse of parts, when designing prototypes there is a long tradition for this. Of the more recent ones both the X29 and the EAP incorporated large parts sourced from other airplanes. Trying to make a useful plane for other than research is not that easy, one failure that comes to mind is the Fisher XP75 fighter.
I have looked the Diamonds how they are done. They are kind of funny. There was a wing design in a motorglider Super Dimona.
THey did DA20, they did DA40, they did DA42, they did different variants of DA40 and DA42, and still the same wing.
And indeed the DA40 and DA42 share exactly the same cockpit. They are building planes like lego bricks, lets take this and that part and glue them together.

When it comes to light planes, the Volmer Sportsman did use wings from an Aeronca. Same story with other designs I think. To use components from another airplane is probably a viable option, the question arise when the overall design is very different.

One last ting when it comes to composite airplanes. One expensive and time consuming part is the mold. Reusing only the molds, the internal structure can be redesigned to suit the new application.
That is true. However, the molds are largely unavailable. A crazy homebuilt person goes to talk to sailplane maker "can you borrow your molds, I will make one crazy homebuilt plane for circling the globe". They will maybe laugh the homebuilt plane maker probably out of the door and maybe call security to ensure that this crazy person is gone. And also it is also true that I would not dare to use somebody else's expensive mold because with mishandling in a more primitive conditions of own garage or its transportation could potentially have a chance to damage it. Sailplane maker would be quite unhappy as a result. "Whaaat? You ruined our expensive mold!?!". Well I have been as a matter of fact practising and I have ruined so far only inexpensive molds made by myself with my three axis CNC.

Best Regards,
Karoliina
 

DangerZone

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I think the air traffic control is a lesser problem than the regulations and the inability to meet them with the light plane.
Burt Rutan circumvented that by only crossing these altitudes and going straight to 65000 ft. However, that was Burt Rutan and the altitude was 65000 ft. For ICE it would require two or three turbochargers in cascade and intercoolers to achieve that altitude, and that altitude flight could become more realistic with hydrogen fuel cell flight than fighting with the ICE that is not getting enough air. This would be highly interesting for myself as well, but as a step one my expertise currently is not enough for dealing with the complicated turbocharger-intercooler install required for that.
It might be wise to realize that both humans and ICE could not function more than a few seconds at altitudes above FL450 without compressed oxygen. No matter how many turbocharges you would have, the engines could not work at all. The majority of turbine engines need heavy modifications and add-ons to be able to continuously fly at those levels. The lack of speed could also be a problem with air so 'thin' as in almost Space conditions, no matter how large the wingspan.
 

Himat

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The range does not mean that landings in between could not be done or should not be done.
It just enables continuing travel without refueling. There are many places in the World outside of USA,
where one can stop but can not get fuel. So the specification supports the mode of traveling hops like with any plane, but
not fueling the plane where it can not be. For our travels we have needed to take canisters to cockpit sometimes to fill the tanks
to get back from some place without fuel. Not very nice, not very proper, and not so safe either. In arctic these places are the
norm, and not the exception. I happen to like seeing places in the artic...
Ok, to me that makes more sense. A stout landing gear and baffling/dividing of the fuel tanks to keep the fuel sloshing around when landing is then called for. Actually I recall that I have been on commercial flights doing just this. The plane arrive with enough fuel to get to the next destination, which is nothing but a refueling stop.

I think the air traffic control is a lesser problem than the regulations and the inability to meet them with the light plane.
Burt Rutan circumvented that by only crossing these altitudes and going straight to 65000 ft. However, that was Burt Rutan and the altitude was 65000 ft. For ICE it would require two or three turbochargers in cascade and intercoolers to achieve that altitude, and that altitude flight could become more realistic with hydrogen fuel cell flight than fighting with the ICE that is not getting enough air. This would be highly interesting for myself as well, but as a step one my expertise currently is not enough for dealing with the complicated turbocharger-intercooler install required for that. So I would rather opt for a simpler solution and airframe that is capable for the high altitude flight later if the enablers for it in the terms of power source can be later met.
With the rise of the drones, you will probably just be stuffed together with the Predators and the like at the flight level they transit.;)

That is true. However, the molds are largely unavailable. A crazy homebuilt person goes to talk to sailplane maker "can you borrow your molds, I will make one crazy homebuilt plane for circling the globe". They will maybe laugh the homebuilt plane maker probably out of the door and maybe call security to ensure that this crazy person is gone. And also it is also true that I would not dare to use somebody else's expensive mold because with mishandling in a more primitive conditions of own garage or its transportation could potentially have a chance to damage it. Sailplane maker would be quite unhappy as a result. "Whaaat? You ruined our expensive mold!?!". Well I have been as a matter of fact practising and I have ruined so far only inexpensive molds made by myself with my three axis CNC.

Best Regards,
Karoliina
Borrowing a set of molds are probably difficult, but others arrangements might be made at a cost. Depending on the work load and utilization of the molds you may not be laughed at if you ask them about contracting them to make you a set of wings.
 

Topaz

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There is a long tradition of using components - especially wings and tails - from other aircraft, with a custom fuselage, for lower-performance sportplanes. In fact, that practice was becoming so common that it's the reason behind what we now call the "51% Rule" for Experimental-Amateur Built airplanes.

I foresee problems in attaching Proteus-like tail booms to an existing sailplane wing. And I would second what DavidD said about using an existing sailplane wing's water ballast tanks for holding fuel. The original wing was designed with the thought of it never being around fuel, so you don't know what the introduction of fuel might do to the structure. Resin choice is critical.

As an overall concept, I think the idea of reusing components for a wildly-different purpose such as this is likely to end up costing you more time and money than if you simply designed and built what you really want from scratch. The level of reverse-engineering alone necessary to turn a sailplane wing into a canard, and adapt your new fuselage design to someone else's existing components, is pretty much the same level of effort to design a new airplane in the first place. Finding two wrecked sailplanes of the exact type you want with only fuselage damage seems a long-shot. The resulting end-product will always be a compromise, and one that will require a lot of effort.

IMHO, roll out the clean sheet of paper and do it right.
 

ekimneirbo

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I think that as you said its an ambitious project. There will be many problems that will require a lot of time and effort to resolve....any of which
could scrap your project after a lot of money and effort is already invested. Why build something that is less than optimal for your needs and then
expect it to outperform other purpose built airplanes? Acquiring wings from two similar airplanes that have crashed would seem to be difficult
on its own, as wings are often damaged. Even if there is no apparent damage,there can be hidden structural issues from the crash or even the
original builders lack of experience. Converting water tanks to fuel is doable but probably just as much work as building new tanks.

Personally, I think you would have far fewer problems if you just purchase some plans and then make what ever changes you desire along the
way. Its kinda like restoring a house vs building a house.People often find that there are hidden problems with the restoration that cause a lot
of additional time and expense. Its often far more work to tear something apart and then rebuild it, than to just build it. With the restoration
you have to make compromises....with the clean sheet you can fix the changes on paper before you start. While I admire your creativity, I think
you are considering a project that would be fraught with setbacks and expense just to end up with something that as you said...is less than optimal.

I will state from experience that when changes are made to any project, the amount of time working thru the adaption process always seems to
be exponential to the result you obtain. Simply stated...."Even simple ideas often take a monumental amount of work and planning to implement them".

Good Luck however you decide to proceed with this.
 

TFF

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I would think the biggest problem with off the shelf glider wings is your cruse would be at VNE of those wings if not higher.
 

wsimpso1

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Repurposed wing for main wing... You would be lucky to need X main wing load capability and find a sailplane with that much or more. Then you would have to be extraordinarily luck to have a way of attaching that sailplane wing (with a fuselage 18" wide) to your 47" wide fuselage. After that, I suspect that it will be suboptimal for drag- the drag bucket is liekly to be in the wrong place. Then there is having suitable hardpoints for engine mounting... Then, will the flutter margins be adequate for a powered airplane?

Repurposed wing for canard... Canard aircraft design usually means using a higher Cl in the canard than in the main wing. Same issues as the wing, but more likely to have enough strength after truncating the span a little. Attachment could be problematic, and you will likely need to convert the flaperons to slotted flaps to give high enough Cl, and flutter margins are worrisome;

I suspect that you would be ahead just designing with appropriate foils and hard points and materials for fuel, etc.

As to configuration, it might be more satisfying to build a canard, but I think the Boomerang is the best configuration for a twin. Engines are out front so prop efficiency can be good is one of the most important issues for range. Configuring one fuselage for people, the other for bags, and the wings for fuel should be relatively straight forward airplane to build.

Billski
 

John.Roo

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Hello dear friends!
Idea is definitelly interesting.

Only…
I just think about comparison between the „aerodynamic profit“ of two sets of wings and technical complications of this solution. I personally like “motorgliders” design – for example Sinus, Phoenix (of course) :), Goshawk etc. - because of simplicity. Following your idea I would buy for example Arcus, take wings and tail and “redesign” fuselage to side-by-side. I am sure that with small modifications it will be the wing system strong enough to allow you to make also four-seater (2+2). From my experience with D-14 (side-by-side motorglider with electric motor) I am sure that you can achieve very low power requirements for horizontal flight. Question is if you can stay with price below motorlider highend – the legendary Stemme. Otherwise you can use already Stemme with larger fuel tanks :)

And last detail… due to certification costs I would prefer to stay in two-seater configuration and with only one engine :)

Best regards!
Martin
 

Workhorse

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29012013463.jpg

I made this experiment to see if XFLR5 matched. Both wings have same wing area/chord/wingspan and same airfoil. C.G. is located around 30% of the line joining the two 1/4 wing chord lines. Wing loading in the fore wing is far higher than in the rear, otherwise it could be like locating the C.G. a little forward of the centroid of a delta wing when in fact it is far ahead from this centroid point.
 

wsimpso1

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View attachment 43824

I made this experiment to see if XFLR5 matched. Both wings have same wing area/chord/wingspan and same airfoil. C.G. is located around 30% of the line joining the two 1/4 wing chord lines. Wing loading in the fore wing is far higher than in the rear, otherwise it could be like locating the C.G. a little forward of the centroid of a delta wing when in fact it is far ahead from this centroid point.
So, how does XFLR5 predict it will fly? And then, how does it fly? Given the size of it, I expect viscosity to dominate the wings and thus the stall behaviour. Does it?

Billski
 

karoliina.t.salminen

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It might be wise to realize that both humans and ICE could not function more than a few seconds at altitudes above FL450 without compressed oxygen. No matter how many turbocharges you would have, the engines could not work at all. The majority of turbine engines need heavy modifications and add-ons to be able to continuously fly at those levels. The lack of speed could also be a problem with air so 'thin' as in almost Space conditions, no matter how large the wingspan.
Burt Rutan certainly didn't know that, and because he didn't know that, he made Raptor UAV.

Check this: Scaled Composites: Projects - Raptor

"In order to reach altitudes of 65,000 ft, the Raptor used a two-stage turbocharged, 100 hp, highly modified Rotax engine. This propulsion package was successfully tested in an altitude chamber to over 70,000 ft altitude. "


NASA has released this article already in 1989:
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19980137599.pdf

There is neither lack of speed. 90 kts IAS at sea level is 90 kts IAS, and it is also 90 kts IAS at 65000 ft. The TAS is much higher, but if the 90 kts IAS can be achieved (which depends on the fraction of power left and if the prop can still move enough air, which will mean that the prop needs to be rotated faster to move the same amount of air than at sea level), the wings will lift the same weight as at sea level at 90 kts IAS. Winged flight should be realistic up to around 80000 ft or a bit more than that (with pure electric, no ICE).

We are talking about space grade pressurisation obviously for anything that flies that high. Nobody would fly that high without pressurization.
 

bmcj

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...altitudes above FL450....The majority of turbine engines need heavy modifications and add-ons to be able to continuously fly at those levels. The lack of speed could also be a problem with air so 'thin' as in almost Space conditions, no matter how large the wingspan.
Burt Rutan certainly didn't know that, and because he didn't know that, he made Raptor UAV.

Check this: Scaled Composites: Projects - Raptor

"In order to reach altitudes of 65,000 ft, the Raptor used a two-stage turbocharged, 100 hp, highly modified Rotax engine. This propulsion package was successfully tested in an altitude chamber to over 70,000 ft altitude. "
To add to that list, the White Knight launched Spaceship One around 50,000 ft. The Cessna Citation X has a service ceiling (still able to climb at this altitude) of 51,000 feet and the Scaled Composites Proteus has a service ceiling of 61,000 feet.
 

DangerZone

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Burt Rutan certainly didn't know that, and because he didn't know that, he made Raptor UAV.

Check this: Scaled Composites: Projects - Raptor

"In order to reach altitudes of 65,000 ft, the Raptor used a two-stage turbocharged, 100 hp, highly modified Rotax engine. This propulsion package was successfully tested in an altitude chamber to over 70,000 ft altitude. "


NASA has released this article already in 1989:
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19980137599.pdf

There is neither lack of speed. 90 kts IAS at sea level is 90 kts IAS, and it is also 90 kts IAS at 65000 ft. The TAS is much higher, but if the 90 kts IAS can be achieved (which depends on the fraction of power left and if the prop can still move enough air, which will mean that the prop needs to be rotated faster to move the same amount of air than at sea level), the wings will lift the same weight as at sea level at 90 kts IAS. Winged flight should be realistic up to around 80000 ft or a bit more than that (with pure electric, no ICE).

We are talking about space grade pressurisation obviously for anything that flies that high. Nobody would fly that high without pressurization.

Impressive. This 1998 report is really worth reading, it's almost unbelievable how they made it. The 543 lbs Rotax 914 is also a monster of a sort, I even found some pictures how they did the turbos in a cascade. Maybe Ross as an expert in turbochargers could provide some more information how complicated this machine was to build.
1996_02693.jpg
Rotax914Turbocharger3.JPG

Source:
GRC ImageNet - Still Image Detail

Prior to seeing the pictures I had a hard time believing because simple calculation of the pressure of low stratosphere at FL650 would indicate something around 3%. With maximum compression rates of 1:6 to 1:7 of modern centrifugal turbochargers this would come up to 1:20 tops. With best engineering in the world it would barely have 60% of air available at sea level, meaning they really pushed the 914 to the limits. I gotta admit this is a great achievement from the NASA guys who built such an engine. Sure, it weighs around 550lbs, but still... great job.

To add to that list, the White Knight launched Spaceship One around 50,000 ft. The Cessna Citation X has a service ceiling (still able to climb at this altitude) of 51,000 feet and the Scaled Composites Proteus has a service ceiling of 61,000 feet.
Well sure, the Concorde also flew at 60,000 feet and the Tupolev 144 at 65,000 feet, but this was a piston engine. Heavily modified, indeed, but still a piston engine. I doubt it flew well at that altitude yet the mere possibility to rise that high and achieve sustainable flight is almost incredible.

Karoliina, did you calculate the weight savings for the size of your aircraft if you would have only two (but larger size) wings as opposed to four glider wings (as in the Proteus case)..?
 

karoliina.t.salminen

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DangerZone: the remaining power is enough to fly. A good high altitude design cruises at low power and there is a lot of excess power, meaning
that eg 10-20% power is enough for level flight. So smaller engine power fraction
is perfectly fine. High altitude turbonormalisation is not pushing the engine to the limits, it
is as easy for the engine than low altitude without the turbonormalisation with one exception,
which is that intake air tends to be hotter because it is compressed.
 
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