ESTABLISHING C.G IN A UNIQUE DESIGN

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MLEVEN63

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I am in a wheelchair. I am designing an aircraft that I will be able to get into with my chair. I know the basics to C.G. placements and am researching every day on learning.
I am shooting for pusher config. with a tandem seating arrangement. With myself and the chair in the forward position. The question arises with myself as a solo passenger. the combined weight of myself and the chair is approx. equal to two people. This seems to neccesitate my(solo) position be moved further aft for balance. With two people I would use a custom lightweight chair which would allow the design to fall into a more traditional configuration.
The thought that comes to mind first is to make my forward position adjustable (which can be done since both rudder and pitch/roll controls will be hand controls) but may encroach on the rear control and seating area. Side by side seating would be easier to calculate but causes other design issues.
Anyone out there with more knowledge than I that might give me some advice or insight would be welcome. I have preliminary drawings done if they will help.

Regards,
Michael Levensaler
[email protected]
 

Jman

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Melven,

I do not have much insight in this arena but I just wanted to say that I am very much looking forward to seeing the solutions that come about from this project. Do you have details of the configuration yet? Are you thinking canard pusher, pod and boom, or something else? The reason I ask is that it might be easier for people to help if they know the general configuration.

Here is a link to an interesting design that has a huge cabin volume that is very close the ground. It seems to me that a configuration similar to this would facilitate a lift up canopy and swing away instrument panel.

I think this an Extremely interesting design challenge and I cannot wait to see what comes of it. Best of luck.

Jake
 
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In the book “Modern Aircraft Design” by Martin Hollman there are formulas on calculating the aerodynamic center of conventional , canard , and tandem wing configuration, he also has a program called “aerocenter” that will determine any aircraft configuration up to three wings
 

richard r

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Melvin, take anything by Martin Hollman with a HUGE grain of salt. He made a reputation by being the one of the few engineers willing to consult in the homebuilt market, but he's utterly wrong on a LOT of things, especially involving canards.

If you and your wheelchair are really equal to the weight of 2 people, you're in better shape than you think.

Crib the aerodynamics from the Cozy 4. Keep the same canard and wings, including the wingspan. Come up with a completely different fuselage that allows for easy entry. Probably make it a high wing, drop down door that becomes a ramp. With the engine high you can have short landing gear.

Put you and the chair in the front. The passenger goes in the back, directly on CG. If there is or isn't a passenger doesn't matter. If you ride in the back with a normal weight pilot, you will need about 50 lbs of ballast in the nose.

The key is minimum equivelant pilot weight. As long as theres (say) 300 lbs or more in the front seat (up to some very high number, around 500 lbs) you're fine. If there's less, you have to make it up. You can put weight in the front seat with you, or less in the nose, because it has a longer lever arm.

Did you learn to fly at the school with the 177's in Big Bear?

Best of luck. It's not that hard to design, if you lift from existing designs, but building is going to be a long, tough road.
 
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Jeremy

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Over here in the UK there is a pusher design that is very popular with wheelchair users and tetraplegics. The CFM Shadow has a canopy that lifts sufficiently clear that a wheelchair hoist can easily lift a severely disabled pilot aboard. Many wheelchair users find that they can slide into the low cockpit without using a hoist, certainly at my local airfield there are several disabled flyers who need no assistance at all to fly these aircraft. I would suggest that you contact the Aviation for Paraplegics and Tetrapegics charitable trust (see http://www.av-para-tetra.demon.co.uk/) as they have a wealth of knowledge on adapting/designing for severely disabled pilots. They are based at my local airfield, Old Sarum, near Salisbury, England, and I know them all well. They uses CFM Shadow aircraft, including one with powered controls and head operated brakes/flaps/intercom that is regularly flown by a tetraplegic pilot who has only extremely limited hand movement and no leg or arm movement at all. He gets on just fine with this design, using primarily shoulder twist and head movement to fly. Also, maybe the British Disabled Flying Club (see http://www.fly.to/bdfc) may be able to give you some ideas.

I also have a paraplegic friend who flies a Rans S6 without any problems. He has a hand lever for the rudder (a bit like a car handbrake lever) and a small built in electric pump to suck fuel into the tanks from a floor standing can, but otherwise has no other adaptations to the aircraft. He can certainly get in and out of the aircraft OK, either straight from a wheelchair or from a standing position (he wears lockable-knee leg braces and uses crutches to get to a standing position). Out of interest this chap holds the Guiness World Record for the greatest number of take offs and landings in one hour, 102! He is pretty much independent of outside help, at least as much as any of us are, and regularly competes in competitions and attends fly-ins with no extra help from anyone at all.
 

MLEVEN63

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WHEEL CHAIR ACCES. A/C

Richard R,
Thanks for the info about the Cozy 4. I had put a rough design of a canard on paper and applied the same solutions you mentioned. I strayed away from the idea because I had no knowledge of how to balance that type of plane,but I will re-examine the idea now because acces to the cockpit worked quite well. I have steered towards a more traditional highwing, highlift slower airplane with Cub like characteristics. One for the simpler construction techniques, and second for the fact that alot of the fields around me are grass strips and lend themselves to short field planes.
If you'd like I'd be more than happy to send you some drawings as they evolve, I'll take all the input I can get.

Thanks,

Mike Levensaler
[email protected]

P.S.
I took my glider instruction at Skysailing in Warner Springs, CA. northeast of San Diego.


Also thanks to everyone for tips to other disabled flying clubs, etc.
 

richard r

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The shadow/streak configuration might not be a bad choice. The underlying question is mission. Obviously #1 is wheelchair access and a passenger, but what after that? Canards are NOT STOL vehicles, they take off and land fast, with a lot of runway. They're not aerobatic, they're good cross crountry.

You might want to look at the V6 STOL airplane, or at the V-8 Magnum for inspiration. Or the BD-4, with it's strutless wing. In any case, CG isn't going to be the issue, just put the passenger on CG. Pilot *can* be on CG - especially in a conventionally configured airplane - but pilot weight is going to be relatively fixed, where passenger and fuel vary. I'd be much more concerned with the gross physical part of wheeling in and out.
 

MLEVEN63

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Richard,
Your right as far as my fight characteristics goal, I am not really looking for a cross country machine, although I love the looks of a canard, I have to stay away from the "funtion follows follows form" and keep to my design goals of a nice stable design with some STOL characteristics for local recreational flying.

Thanks,

Mike
 

Jeremy

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I've flown the Shadow a lot, it cruises at about 65kts easily (more for the Streak version) and is certainly STOL. It handles extremely well and the only real downsides to it are the cramped rear cockpit (which is OK for a small folded wheelchair) and the high noise level in the back (only a problem for a passenger).

It might be worth taking a close look at the Shadow configuration and seeing if you could design something that would meet your needs from it. As Richard says, C of G isn't really an issue. The Shadow does have a front seat weight limit of about 13 stone I think, due to the fact that the pilot's mass keeps the thing inside the C of G limits, but you could design the pilot position to suit your own weight.

The view from the front of the Shadow is outstanding, and makes this aircraft a delight to fly. I have a suspicion that the company is now owned by a US parent company, so maybe buying a kit might be an easy answer for you.
 

Holden

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Michael,

I have been working on a design (seaplane) that might work well for you.

I am looking for your specific issues (weight of you and chair) and a general understanding of issues faced by people in a wheelchair.

There may be a simple design change to my design that can work well for a large number of wheelchaired pilots and add benefit to the average pilot. The analogy made could be that of the ramped curb on street corners.

Holden
 

MLEVEN63

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Holden,
My primary design goal is for independant entrance to the cockpit. The demands of this criteria are:
1. A relativley low angle ramp entry, you mentioned curb cut aways, they are by law 1:12 a little steeper would be alright.
2. Head room, I myself require 52-54" floor to ceiling. I am 6'3 so others may not require that much.
3. Safe hand controls!

I ran into this problem while taking sailplane instruction. The FAA approved hand controls were fine for a parapalegics, they have full use of their hands and upper body strength to differing degrees. I myself am a quadrapalegic and the controls for quads do not lend themselves to uniformity because strengths and weakness' vary enormously between individuals. I had a weakness in my ability to get full left quadrant deflection in the stick, so I designed my own controls that were much safer for anyone with limited hand strength, but I couldn't solo with them because they were not FAA approved, even the instructors could see the improved controls were better but the approval process is daunting I was told. This sent me to the ultralight world, where I discovered alot of creativity in hand controls and got me started on this design project.
I would love to see what your working on and vice/versa and offer any insight I can, a seaplane sounds interesting (I live next to a large lake!)

Regards,

Mike

[email protected]
 

Holden

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Mike,

Thanks for the reply.

Can you post a 3 view sketch of you in the wheelchair with major dimensions and weights? Is your chair an "average" chair, if such exists. Is there any uniformity or standard to wheelchairs, or is it mostly custom design? Perhaps a web page url would have a picture of your chair with dimensions.

Holden
 

MLEVEN63

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central/midcoast Maine
Holden,
I have some ugly but close to accurate cad drawings of my chair and myselfs measurements. Chairs are usually custom fit to the individual but an average size could be exstrapolated easily.
You could try looking up manufact. specs on the web or going to a local supplier of chairs in your area. That is where I found the weight and specs for my chair (the web pages usually just show photos).
Do yiu have a cad program, I could EM you some .dwg files. But I will try to post them here along with the plane drawings soon. Or I could just mail you some hard copies.

Thanks,

Mike
[email protected]
 

MLEVEN63

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Holden,
Some of the major wheelchair mnfg. are Quickie & Invacare. Like I said your best bet for specs is to go to a vendor in your area. They may have brochures with specs that you could scan or trace.

Have a good night,

Mike
 

Holden

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Mike,

I checked on the web and saw several brands of wheelchairs, including the Quickie. The widest wheel base was 31 inches.

I suppose there are several ways to make a "wheelchair drive in" airplane: 1) twin, 2) pusher, 3) tractor with rear entry and twin booms.

In my case, I have been working on a pusher seaplane. The canopy will open up like a large mouth allowing the pilot to walk out of the front. The width will be 33 inches outside and around 31+ inches internal. Some sort of side stick controls, along with an instrument flat panel could be used that can rotate in and out of the way. The floor could be recessed around the front tire to allow wheelchair drive in. Getting from the pilots front feet at 18 inches above ground would be a trick. A kneel down system would not work (easily) on a seaplane because of swamping.

Such a design lends itself to great beaching for a seaplane and allows the pilot to get out on dry ground and avoid walking on the seats. Most all seaplanes, such as Seawind, Lake, Glass Goose, and others, except the Seabee, do not allow forward access. It also allows for large cargo hauling on the CG in the "back seat" area, including 50 Gallon drums and large "game" (deer, moose, overweight neighbors wanting a ride).

I read somewhere that there are around 200 paraplegic pilots. The volume would be very low, so the wheelchair features would have to be just part of the design and not special or unique to the airplane so that the average pilot would want the airplane and thereby increase demand and lower prices/costs.

Basically it is the ramped curb dual use thing again. The design must add utility for able people, and by chance meet the needs of wheelchaired pilots. The able body people will build them (homebuilts) and a paraplegic pilot could then buy one as a second owner. A specially designed airplane would NOT appeal to macho pilots if it was branded as a "wheelchair" airplane. However, a "go anywhere," big game hunting, fishing, Alaska machine would be for "real" men who need to hual real "stuff" around for camping and adventure. The wheelchaired pilot is then on equal "footing" in the market.

This is how I see it.

Thanks for the "heads up" on wheelchairs. I never gave it much thought until I read your post.

Holden
 

MLEVEN63

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Holden,
You really have my curiosity peaked. If I understand you correctly your kinda creating a flying SUV. in the form of a seaplane.
You want to have the pilots station designed as aconvertible space, so that you have clear access to the cargo area for larger items i.e game & cargo. and you have 31-32 in cabin width.... let me toss out some ideas in the spirit of "universal design"
You mentioned a nose wheel, That would pose an access problem for both parties. a trip point for the abled and an obstruction for the disabled and cargo loading.
The 18" jump to the pilots seat would not be a problem for parapalegics and low level quads. You'll find alot of mindsets in the disabled community. The ones who would be into airborne offroading are going to view a jump transfer to a pilots seat as simple as grabbing a glass of water. Minor obstacles are ignored, I have friends who yank themselves from a manual chair into pickups.
Let me toss out some design ideas: instead of a seaplane config., how about a taildragger amphibious, think like a boatbuilder first, then wrap a plane around it
1. It would allow for a clear shot through the fuse/hull with the swing away controls/panel etc. No nose wheel to contend with.
2. After a water landing the mains could be extended to the bottom to stabalize the plane for loading while up against an embankment or beach and allow for the jaw to act sort of like a beach landing craft. Also portable ramps could be stowed aboard.
3. The amphib. would allow for bringing the plane ashore if the location allowed. No inherent mooring troubles...I own 2 boats now and have grown up on them :) & :(

The ideas are spinning in my head but I think if you let your mind go a little to the boat design side of things, figuring tthe hull displacement and dead water line of the craft to see how much freeboard you'll have at the nose and then come around to the aircraft you might get some new i inspiration that could bridge the multi-use purpose use of the design!!
****, now I have to go grab my pencil!! :)

Later,

Mike
 

Holden

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Mike,

A tail dragger is dead on arrival. The insurance costs alone will drive most of the affordability out of the airplane. A tail dragger cannot be made to land in the water with the gear extended because of the lateral displacement and the variability of the drag forces on the tires. I believe my design can, or at least it will when I'm finished. Seaplanes and gear down landings account for a major cost factor, and are the most difficult part of the design. There are a lot of other issues which I will not go into that make a tail dragger one of the worst choices, especially for a person without the use of legs!.

The nose gear is under the pilots seat. The wheelchair wheels would straddle the wheel well and still allow access to the passenger area. I have a "trolling" motor that fits between the pilots legs and forward of the wheel that can be lowered and used for docking and control on the water, something a wheelchaired person would find quite useful, I would imagine.

As for a classical boat hull design, I know from experience that they do not work well enough to get the weight down and the speed up on an airplane to where I know they can be. The flip over issues also preclude their use to meet my safety requirements. Then there is the stray, drag, and on and on. I am a minority on this issue, but my research says there is a better way.

Like I said before, the primary focus cannot be on wheelchairs. The wheelchair ability is just a natural part of the true performance of the airplane. After all, Seabee has front access or could be made to have a ramp, but they have not been accepted in large numbers even by able body pilots. Why? Making another Seabee with a door/ramp in front would not be any more successful than a Seabee without a ramp, in fact less so, because the perception would be that the modification was for the handicapped pilot.

Would the average person buy a minivan with a ramp on it? I would say no. Why? Perception may be the major issue. People don't want to be known as the person who drives a "handicap" minivan. This is central to my point. It cannot appear to be designed for a handicapped person.

If you were to ask the average kid on a sidewalk why the corner curb is ramped they would likely say it was for bikes and skateboards, and NOT for wheelchairs. If the marketing was geared towards kids on skateboards and biker safety ("it is for the children"), instead of wheelchair access, there would have been ar less resistance.

Airplanes are about "status" for the sake of pride. Let's be honest...people don't want to be thought of as handicapped, especially those who are. When a wheelchaired pilot buys my airplane it is because he is on an adventure, not because it fits his wheelchair. I would NOT advertise the wheelchair ability at all. I'm sure word would get around fast enough in wheelchaired pilot associations if the airplane worked.

In fact I don't think a landplane could be made to accommodate a wheelchaired pilot without the negative perception because of the lack of a good reasons for design. However, in the case of a seaplane, the forward access onto dry land becomes a major driving issue. The forward access also allows for great fishing, diving, and access from swimming, and docking. The first thing that pops into the head of the person looking at the airplane is fun and utility, not handicapped. If they think wheelchair, the airplane's success will suffer. This is key to the success as a wheelchair capable airplane, IMHO.

Do you agree?

Request:

What I would like from you is a rundown on the issues you see as important to the average wheelchaired pilot.

Holden
 

MLEVEN63

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Hi Holden,
I mispoke when I said taildragger, I was thinking more of the classic amphib. design w/ retractable mains. You are aiming towards a low-slung pontoon type config.?
After thinking about it I can see the problems of stability while sitting still, let alone the control issues you mentioned. I was talking to a friend of mine whose rated for everything from Cubs to G5's and choppers. He had the same opinion of amphibs. We had a fellow when I was a kid that had a pusher amphib on our lake (an osprey or someting like that) The only way he could get the thing in the air was to run full throttle for what seemed like a mile and maybe if he had a good head wind he'd get airborne.
Unfortunately, your right about the perception of the disabled and the marketability of such a design. My design is a one-off so I don't have those concerns. But hey, its my duty as a crip to get up on a soapbox when I can, just think of all you bipeds tripping and falling if we took our cutaway curbs back.:):D
As far as your question, the primary need for a disabled pilot is easy access to the cabin and the ability to get a chair up and in if their doing any cross country flying. Once in the seat as long as the appropriate hand controls are installed, your on your way.
To put it in perspective, imagine having to drag yourself using only your arms into a lowing plane, or trying to get around a strut and wheel on a high wing and wresting a chair along with you. As an experiment try sitting on the floor parallel to the couch and using you arms only get yourself up onto it.
Let me know how the design comes along.

Have a good one,

Mike
 

Holden

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Mike,

No "low slung pontoon" config.

I am trying to avoid some of the issues that Oprey and similar configuations have. Takeoff should be less than 500-1000 ft on water.

So, having the wheelchair as the main chair is not important. Just so long as you can walk on your hands into the seat and then grab the chair and load it in.

It is doable with a light weight collapsible chair. Just open the canopy (gas shocks with small rope to control), pull to the side just behind the rudder peddles, slide onto a "shelf" or lip at 28 inches and then up a few inches to the canopy seal ridge which is at the same level as the seat (30 inch), slide in, reach over and grab the chair, lift it over head and put in rear, grab rope, close canopy, and you're off. No wheel, strut, or anything to get in the way, and not long slides along a wing.

You were talking about a ramp before. A ramp is not important? Either way would be doable, however a ramp would require special hardware. A 1:12 ramp would be over 30 ft long! Are there micro wenches that could lift 250 lbs, or maybe 100lbs. Perhaps a AL track (for the wheels) could be set up that pivots at the rudder peddles and "scoops" up the chair from the front? The wench could be hooked to the canopy forward area with two support tubes that would fold back for storage.

I have a single hand lever for the brakes (not a tri gear or tail dragger), so the only issue would be the rudder, assuming good upper body strength. A bar that grabs on the rudder cable that runs by the pilot would work. A standard joy stick for elevator, ailerons would be on the side.

I'll have to put some thought into how you would preflight it.

I don't see any major changes I would need if you could walk on your hands and sit in the airplane seat. Wheeling a chair in and out would require special structure to the canopy and floor, which could be a feature for loading in cargo that the average pilot might want. Not likely though because of weight.

Thanks for the help and discussion.


Holden
 
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