Would this plane-concept work/be legal?

[Frank N. O.]

I've mentioned my special idea a few times now and I thought that with your experience here I might get some questions answered so I can get a little closer to finishing the design details on it. My plane is special in several areas compared to normal GA planes, exterior, interior and maybe also propulsion. Since the idea I had for propulsion is still intested in flying as opposed to driving then I'll ask about it first.

Propulsion in an aircraft is crucial in many ways and I've thought of how to make the best possible, both in terms of speed, manouvrering and fuel-economy and minimum polution. One concept I've gotten is pretty wild but here goes: Serial Turbo-Electric Hybrid. One gasturbine engine integrated behind the cockpit only working as a generator chargin a smaller pack of batteries that then via a computer (to maximize acceleration without using more power than can be used, and for synchronizing the engines to eliminate torque turning the plane) drives two parallel low-speed electric motors driving a set of ducted scimitar fans each. Electric motors have a ton of torque and can be made to go at low speed thus hopefully making them more silent and the torque will enable high-power fan-shapes for high thrust as well as enable direct drive instead of the need for a reduction gearbox to eliminate un-needed extra parts and service. Another thought is that the hybrid setup would mean that if the turbine had to switch off then maybe I'd have a minute or two of batterypower and thereby thrust left to perform manouvres to get out of a possibly bad area besides the idea that this setup would maximize fuel-efficiency and minimize noise with the turbine placed in the body with intake and exhuast over the fueselage it would be very silent for both me and the people underneath.

Btw to quickly explain how the plane is shaped then it's based partially on a fighter with a 2-seat side-by-side cockpit with a F-16-style two-piece canope in the nose of the plane, with partially forward-swept wings starting just behind the cockpit, placed in the middle, height-wise, to hopefully minimize the need for rudder to make the plane bank direclty on the centerline, where the drivefans are place also. The main idea with the wings were to give full visibility both up and down and I forward swept them slightly to try and keep the wing-lift on the good side of the cog but of course that's hard to plan without knowledge of propulsion system weight etc.
I had an idea of having the plane fuselage have lifting body proporties also since it only had two seats and two seperate fan-pods in the back. Another idea was to borrow the tail from the Black Widow II with a seperated V-Tail however only have them as elevators and use a split aileron as seperate rudders that could thereby also double as speed-brakes like on the Rutan LongEZ. The split surfaces are inspired from Bugatti's old fantastic race-plane that had a similar system developed for manouvrering. The inner part of the main wings would be designed like I understand the big Lancair is, to stall first so the outer wings can make the plane stable and manouvreable even in the stall, at least that's how I think they did it, they never explained what made the plane stable but I guessed since I know most planes have at least two different aerofoil shapes in the main wings. The plane would also have the ballistic airframe parachute or whatever it's correct name is. The projected performance is no more than a Mooney Bravo in terms of top speed, I'm pretty sure that'll be fast enough for me. Spoilers are also planned btw, for the inner wings specifically.

The third part of course is the cockpit that would be inspired in shape and seating position like a car but since I haven't figured out if the hybrid propulsion setup would work then I can't come closer to making a mock-up of the panel since there are a lot of switches that may or may not need to be placed. But the controls would be a side-mounted wide single throttle with a button for the thrust-reverse and a panel-mounted yoke.

So, how crazy am I? It's all planned to try and make the plane as effcient and safe as possible, while designed to be used strictly by me and not intended for general production.

Frank

[Inept]

interesting concept.   How much will your electric motors weigh... it sounds like a silly question, but I've looked into electric powerplants and found them impractical because of their immense(sp?) weight.

Secondly, what formulas and calculations do you use to calculate the airfoil design, lift/drag coefficients, lift requirements for the aircraft, required engine performance, etc?   I've not been able to figure those out, but I've also not been trained as an engineer.

[fireflyr]

Holy cow Frank,
You are ambitious aren't you?
Anything that flies sounds like fun but I'm one of those people who has no interest in inventing anything.
I like it when those fan things either push me or pull me fast enough for the wing things to catch enough air to lift me high enough to go someplace neat, and the faster it goes, the better I like it.
Your ideas sound fascinating, maybe you'll go on to make history with new concepts in aviation.
There is always room for a better idea!
Jim

[Gulfstream Driver]

I love this idea.  I do have a couple of concerns, mainly with the wing.  The nice thing about a forward swept wing is its maneuverability.  It'll do a snap roll without the pilot even thinking about it.  Unfortunately, that also means it's extremely unstable and will stall at the tips first.  I think it would be possible to design an outboard section with more lift than normal, possibly with slots, but it is something to consider.  Since you don't have too much forward sweep, you may or may not need a computer to keep the wings level.  I'll try to find a good website on wing design and aerodynamics.

Also, weight would be an issue, I think.  Will the gas-turbine engine and the batteries be light enough and hold enough juice?  Something to consider.

Will it use props or jets?  I realize there will be electric motors, but what will actually pull the thing through the air?  I'm also confused about the elevator/rudder concept.

Please don't take this as criticism.  And, I'm no engineer, so these are just a few tidbits I picked up in aerodynamics in school.   Good luck and good designing!

[Frank N. O.]

Thanks for the replies Sorry for my late reply though, I've had a bad few days sleep.

I'm not an engineer, although I did start a 3 1/2 year course before I got sick when the loss of my dad really set in, although that was for electronic engineering. I have however a natural sense of noticing and logically analyzing what I see and vehicles have always interested me greatly.

I sadly have no info on how heavy the things would be however I know there's an electric motor weighing 67 kg that can give 500Nm of torque so I thought that might work, plus the gasturbine would be a small one that's also capable of using multiple types of fuel to make it easy to fuel although it had to be ultra-clean burning for low emissions and high effiency but that was part of the reason for the whole hybrid setup since any combustion engine has a set rpm where it's the most effective at burning fuel.

The forward wing-sweep was in case I needed to move the wing-lift point further forward in relation to the cog without having the wing underneath the cockpit ruining the downward visibility, to make sure it wouldn't tip nose-up when stalling, I read that in a book somewhere that the cog and wing-lift position decides this, of course people, fuel and luggage will move the cog I know. However the gasturbine would be behind the cabin and the engines and fans further aft so maybe the forward wingsweep isn't needed to correctly place the lift point vs the cog. But thanks for pointing out the stall characteristic of forward-swept wings, I appreciate it

To clarify the propulsion system I'll try again. There is a small gasturbine engine in the fuselage that only drives a electricity generator. That generator keeps a smaller set of batteries topped off. Those batteries drive two electric motors that each drive 1 or two counter-rotating ducted fans that provide the actual propulsion. The idea about having two engines is to be able to use smaller fans and to have counter-rotating fans and electronic control of the motors should cancel any torque on the plane, plus the fans should be directly on the centerline further making the plane easier to fly. using ducted fans was also to further increase the effciency of the system both to help performance and fuel-use.

The electronics would just be for the powerplant itself, monitoring and controlling the gasturbine to keep the batteries topped-up, to make sure that no more power was applied that could be used for acceleration for the electric motors when giving full throttle and to make sure the two engines run at exactly the same speed to cancel torque so rudder-correction wouldn't be needed for that. The aerodynamic controls however would be fully manual like a normal GA plane, I don't see any need for fly-by-wire for a plane that size since others don't and with the wing-position (height wise) and torque-canceling centerline-placed propulsion then such a system shouldn't be needed anyway.

Btw, it's not totally grabbed out from thin air though. One thing about hybrid propulsion systems is the need for batteries that are capable of charging and discharging at a high rate and NEC recently announced a new cheap battery-type that could do just that, although they planned on making back-up power-systems for PC with it first. The batteries were also claimed to be very small and light and made by rather simple materials.

I hope this answers all questions there were I could anwer, if not then ask again.

Frank

[Gulfstream Driver]

If you're worried about CG placement in relation to center of lift, you could move the wings all the way to the back and put a canard on it...Just a thought. 

No matter what, you will need some way to control yaw.  If I read correctly, it sounds like you're trying to get rid of the rudder.  Even if your engines don't produce a yawing motion, you still get adverse yaw when you turn and will need some way to land in a cross wind. 

[Frank N. O.]

I have thought of a canard design but some said it wasn't very good due to the difference in lift, I think something concerning that a canard plane has lift from both surfaces meaning flaps can't be made easily whereas conventiontal planes use a downforce elevator. My concept does have a rudder though, it would be a split-function of the aileron's that work sperately like the LongEZ so you can activate both for speed-brake function. I chose this since the V-tail might make the rudder roll the plane and since the wing and propulsion positions were all made to reduce/remove asymetric forces on the plane then that would be a dumb decission.

I do admit that part of the design was to make the plane look different too, however for me there's no contest, function has the priority over form in case you can't have both.

A canard design to my knowlegde gives several other problems btw, stall characteristics for instance, and you can't have spoilers on them, but maybe the spoiler could be on the lifting body section instead so the plane could decend quickly if needed for a landing. But would it still be possible to create the plane to be manouvreable in a stall like the conventional winged Lancair? There might be benefits to the canard of course, a shorter distance for the elevator controls to go and better downward visibility. However with canards you can't have a V-tail naturally which means that it probably needs a vertical stabilizer to be aerodynamically stable and that means possibly higher drag than the V-tail configuration, although I have heard that the old Beech V-Tail had the same top-speed as the sibling model with the conventional tail so if it has any benefits except visual that I don't know.

Frank

[Roland]

I’m very concerned about the propulsion system in this concept. My problem here is weight. The e-motors will be very heavy as well as all the batteries necessary to fulfil the concept. Using a gas-turbine to keep the charging of the batteries on top level doesn’t make things easier.

Think about the loss of efficiency of the energy available (here within the Jet-A1 fuel) over the whole “power-train” to your fan-blades. According to the law of entropy (loss of energy) within the thermodynamic laws this concept of propulsion will have a tremendous loss.

But just start to calculate. What rate of thrust you will need for the plane to take off (not to fly!)? So then you know the energy needed. Next you calculate the source of energy transformation, i.e. from fuel to thrust.

See, the helicopter became so widely used only after installation of gas-turbines. Why? Well, gas-turbine engines can transform energy stored in fuel far better into thrust then piston engines can due to the better engine-weight/power-output ratio.

I think your aircraft will not fly due to weight problems. Batteries, especially Nickel-Cadmium, are bloody heavy.

[Sleek-Jet]

Battery weight would be a consideration.  Even "small" battery packs would probably end up weighing as much as the bare airframe.  But it might not be a bad idea to start working on now... "room temperature" super conductors are already in use in the utility industry (I believe Switzerland has built a transmission line using them in the last few years), so I would guess that industrial uses for them aren't that far off... say a decade or so. 

If you had super conducting motors driving the fans, you wouldn't need nearly as large a battery pack. 

[Gulfstream Driver]

The nickname for the Bonanza is the V-tailed Doctor Killer...The problem with the V-tail is that you don't have both a rudder and an elevator.  Combining the two reduces the effectiveness of both.  They look awesome, but they're dangerous.

[fireflyr]

I heard once that if it wasn't for Bonanzas there would be more doctors and that if it wasn't for doctors there would be more Bonanzas --Kind of a self canceling equation don't you think?

[Ted_Stryker]

The nickname for the Bonanza is the V-tailed Doctor Killer...The problem with the V-tail is that you don't have both a rudder and an elevator. Combining the two reduces the effectiveness of both. They look awesome, but they're dangerous.

Very true!  Also, when they originally were manufactured, Beachcraft printed incorrect airspeed data in the Bonanza POH, and the empennage wasn't strong enough.  With the V-tail configuration (rudder-vators) a harmonic caused by high speed airflow between the surfaces would cause a twisting motion.  The tails of the planes would, therefore, if flown near the middle of the yellow arc on the airspeed guage (originally), rip right off the plane!  Beachcraft never admitted fault, but they did, quietly, revise their Bonanza manual on the plane, and two ways of fixing the issue were introduced.  A tail reinforcment kit, or, later, an actual conventional tail replacement could be retrofit (a small cottage industry in such Bonanza conversions sprang up in fact).

The idea behind the plane's unique (at the time) design, was to help increase speed by getting rid of one more airfoil surface to reduce parasitic drag.  It does work for that aspect of flying, though the airfoil surfaces ideally should have been slightly larger.  The F-117A Stealth fighter takes advantage of this same concept very sucessfully.

Just an fyi. 

(I found some errors in my post and corrected them.... that's what I get for typing while brain is flying faster than fingers can keep up with )

[Sleek-Jet]

I wouldn't go as far as calling a V-tail Bonanza dangerous... no more so than any other high performance single engine airplane.  Not to say that there arean't flaws in the design, but it is an elegant solution to parisitic drag problems.  They do suffer from marginal directional stability in turbulance (that's why they are called the Wiggle Wagons...), and it should also be noted that the convetional tail Bonanza wallows around in the bumps as well. 

What didn't help things, is the control surfaces are very particular to static balance.  If an "elevon" had been worked on or painted and not re ballanced, they had a habit of coming off in flight, usually followed by the rest of the tail.  That's not a design problem, that's a maintenance/owner problem.

But what it boils down to... is why are you operating any airplane into the yellow arc routinely in the first place???  Cessna 210's have a habbit of shedding parts when operated into the yellow and the add a little turbulence.  But nobody goes around saying how many lawyers have died in Centurions.  (It has been my experiance, the doctors fly Beechcraft, lawyers fly Cessna... )

[Gulfstream Driver]

I wouldn't go as far as calling a V-tail Bonanza dangerous... no more so than any other high performance single engine airplane.

Good point.  I guess the main problem was people with a lot of money buying an airplane and then not getting enough training.  Cirrus is having the same problem right now.

[Frank N. O.]

Wow a lot of great posts

The idea for the hybrid was both optimum fuel-use even though this is a lot easier in an airplane vs. a car since they don't accelerate nearly as often, but also to try and clean up the cockpit of half a dozen levers per engine but maybe I should re-think and use the gasturbine to drive the ducted fans instead, but to have just one set of controls mean I can only have one engine and wouldn't that make it a problem to have twin fans? It would need to be co-axial correct? And how much power-loss would that be besides the reduction-gear? Furthermore, does ducted fans still have adjustable pictch or only conventional props? FYI I planned on using showels of some kind to provide reverse-thrust and I'd planned on having a transverse hand-grip handle for the throttle with the switch for reverse-thrust on a thumbswitch of something similar to be able to land fast with all needed controls within reach for increased safety.

The split V-Tail was inspired from the Black Widow II but I also though of what I've read about stall-problems with different tail-positions causing the elevator to be in the turbulence and therefore loose effectiveness and with a angled section then there should be at least part of the wing in clean airflow, bus as I said, I'm just an enthusiast that have picked up stuff here and there and not an engineer sadly.

One more question btw, how come even so-called wide cabin GA planes like the Commander 112/114/115 are still a lot smaller on the inside than even a european minicar, specifcally in width/shoulderroom? One place even said the Commander is slow because of it's big wide cabin give it a big drag.

Frank