Backcountry Pilot

[175 magnum offline]

Very interesting machine,some observations:
1-when climbing out you want your oil pan sump at the firewall end.
2- radiator should be sized @ 3cubic inches of volume/hp. so 600x3 = 1800cubic inches of rad. that one looks a little small
3- the upper wing attach area seems a little light for a plane that size
4- it looks like the main landing gear could change wheel base up to a foot as each gear swings back and that might make for some interesting crosswind landings and the torsional load upon landing will try and force the nose into the ground.

[hotrod180 offline]

This thing belongs to a good friend of mine. No there are no wings. I tried to convince him to put on my Helio Courier H800 wings and to build out the fuselage area at the wing location with stubs 8'6" overall and attach the wings to those stubs to increase the overall wing span. ....

Is there an advantage to more wingspan gained by increasing cabin width (as opposed to wing length)? The cabin portion doesn't "fly" so I wouldn't think so, but I'm definitely not an aeronautical engineer.
And is that airplane gonna have a trailer hitch so it can pull a bass boat?

[flathorn offline]

This thing belongs to a good friend of mine. No there are no wings. I tried to convince him to put on my Helio Courier H800 wings and to build out the fuselage area at the wing location with stubs 8'6" overall and attach the wings to those stubs to increase the overall wing span. ....

Is there an advantage to more wingspan gained by increasing cabin width (as opposed to wing length)? The cabin portion doesn't "fly" so I wouldn't think so, but I'm definitely not an aeronautical engineer.
And is that airplane gonna have a trailer hitch so it can pull a bass boat?

No, not build the entire fuselage out , only stubs at wing area to match wing profile. Leave fuselage alone. Only add wing area.

[Aviatorpa11 offline]

Nope but it will haul a 3 wheeler he said

[dirtstrip offline]

4- it looks like the main landing gear could change wheel base up to a foot as each gear swings back and that might make for some interesting crosswind landings and the torsional load upon landing will try and force the nose into the ground.

That landing gear is just wrong. The landing impact originates at the axles and will try to flex the long tubes of the landing gear, which do not appear heavy enough. The lateral flex on those long tubes, if they hold, will then travel up to the forward pivot pin being cushioned by the airbag. The force changes at the airbag and becomes torsional as it makes that sharp corner into the lower frame and the leverage travels rearward down the frame toward the cg point and then turns upward again through the cabin tubes to meet the downward traveling force of the wing load as it becomes supported by the gear. That is way too many corners to make and every corner multiplies the stress on the tubes of the airframe. The impact of landing should travel a straight line from the axles upward toward the cg point of the wing. To do this without adding a lot of weight it needs a long oleo compression strut from the lower end of the gear tubes to a point near the top of the cabin fuselage to allow that force to go upward and in a straight line directly to the wing, similar to what is on the old Fieseler Storch and what you see on the new Highlander.

The issue of the gear moving rearward in compression should be addressed too. I can't see how it can be stable on landing when the cg moves forward as the gear moves back during compression. Its like allowing the balance point to change on a teeter-totter in motion. Its unstable. The wheels need to move sideways away from the frame at a right angle during compression to maintain their relative position to the cg rather than rearward which makes it increasingly more nose heavy while landing.

Farm engineering is a terrible thing to waste and its happening right here at my keyboard.

[Aviatorpa11 offline]

I am not an engineer, but from my seeing it in person, it is very strong and I am confident that he accounted for every possible load put on that gear.

[Terry offline]

The issue of the gear moving rearward in compression should be addressed too. I can't see how it can be stable on landing when the cg moves forward as the gear moves back during compression. Its like allowing the balance point to change on a teeter-totter in motion. Its unstable. The wheels need to move sideways away from the frame at a right angle during compression to maintain their relative position to the cg rather than rearward which makes it increasingly more nose heavy while landing.

I'm not seeing that the cg would change with the gear moving backwards?
The way I see it the pivot point don't change, so the cg won't.
Throw a set of scales under the mains or tailwheel and swing the gear forward or aft....I don't see the weight changing?
I can see that it would nose over easier the further aft the gear travels, but not that it would change the balance or feel on landing. Am I missing something?

[M6RV6 offline]

The beauty of a trailing landing gear


All kinds work

GT

[PilotRPI offline]

This thing belongs to a good friend of mine. No there are no wings. I tried to convince him to put on my Helio Courier H800 wings and to build out the fuselage area at the wing location with stubs 8'6" overall and attach the wings to those stubs to increase the overall wing span. ....

Is there an advantage to more wingspan gained by increasing cabin width (as opposed to wing length)? The cabin portion doesn't "fly" so I wouldn't think so, but I'm definitely not an aeronautical engineer.
And is that airplane gonna have a trailer hitch so it can pull a bass boat?

An airplane fuselage usually does create lift at positive AOAs. It does so much less efficiently than a wing, since a fuselage has an aspect ratio of <1. If you google "Lifting Bodies", you may see some neat NASA research aircraft that used a fuselage only to create lift (warning: I haven't tried this so who knows what other pics you'll get).

I wouldn't consider this an "advantage" in this case though. My thoughts are greater frontal area for more drag, more weight for a bigger fuselage, more wetted area for drag, and stuff like that.

One thing that may be of interest, is that when one sees a "wing area" number, that does include the wing area that is part of the fuselage. So if you have two airplanes with the same wing area, and one has a very wide fuselage, it may have less lifting capability, due to having less real wing. This always kinds bothered me during my classes, but since the fuselage can actually create some measure of lift, it is left in as part of the wing area.

[gearhead offline]

Flathorn just told me about this thread. I am the builder of the Condor and would be willing to answer any and all questions. Very intuitive comments by alot of you and some hilarious ones too.
As soon as I figure out how to up load pictures, I will post some.

[Stol offline]

A fellow auto engine conversion... ...

I am gonna stick up for him, come hell or high water.

[gearhead offline]

STOL, you have a very neat instalation. WOW

[S-12Flyer offline]

The issue of the gear moving rearward in compression should be addressed too. I can't see how it can be stable on landing when the cg moves forward as the gear moves back during compression. Its like allowing the balance point to change on a teeter-totter in motion. Its unstable. The wheels need to move sideways away from the frame at a right angle during compression to maintain their relative position to the cg rather than rearward which makes it increasingly more nose heavy while landing.

I'm not seeing that the cg would change with the gear moving backwards?
The way I see it the pivot point don't change, so the cg won't.
Throw a set of scales under the mains or tailwheel and swing the gear forward or aft....I don't see the weight changing?
I can see that it would nose over easier the further aft the gear travels, but not that it would change the balance or feel on landing. Am I missing something?

You are correct that the CG does not move. But incorrect in thinking that the pivot point is stationary. The pivot point is the axel and it will move in an arc towards the rear of the plane as the gear flexes. Shifting the pivot point a couple of inches may not have much effect if the attachment point if far enough ahead of the balance point. The big difference with the trailing link systems like the Wilga is that the moment arm is rather short and the arc is much smaller. On this aircraft the entire gear leg moves and the arc is fairly big.
If you put scales under all three wheels at once and moved the pivot point aft,(compress the gear) the tail will get lighter while the mains get heavier.

[Terry offline]

Yep, you and Dirtstrip are correct, I get it now.

[dirtstrip offline]

The trailing link of the Wilga is already near the 45 degree position. Compression of the short arc of the trailing link causes as much upward movement as rearward and as stated above is short enough not to be a big deal. The second aircraft photo above moves entirely upward on compression since it trails already at 90 degrees. Cg in flight is the balance point on the wing we are all familiar with but the second balance point I am referring to is the shifting of that weight from the wing balance point to the gear, which then also needs to be balanced and stable in the load change as the gear is compressed. The long gear on this plane, unless very stiff will travel a much larger arc, also as explained above by S12, and give a much larger rearward movement. Hard braking alone can throw weight forward and a shifting balance point on the gear's center of gravity will also. Stability could be compromised. How much will be determined by the testing. Not writing it off, but these are valid questions to someone doing test piloting.

http://www.dept.aoe.vt.edu/~mason/Mason_f/M96SC02.pdf

[Stol offline]

STOL, you have a very neat instalation. WOW

Thanks............

And coming from someone who has shared this disease, your compliment is taken in spades..

ps. I assume you watched the video ? http://www.youtube.com/watch?v=rCNnEgRk ... oBHd5YSUfu

[gearhead offline]

ps. I assume you watched the video ? http://www.youtube.com/watch?v=rCNnEgRk ... oBHd5YSUfu

Yes I did and looking at your pictures, I like how clean your installation is. I see you are using dual MSD boxes. Me too.
My project has caught me in bad times and I am selling it all off.

[gearhead offline]

The issue of the gear moving rearward in compression should be addressed too. I can't see how it can be stable on landing when the cg moves forward as the gear moves back during compression. Its like allowing the balance point to change on a teeter-totter in motion. Its unstable. The wheels need to move sideways away from the frame at a right angle during compression to maintain their relative position to the cg rather than rearward which makes it increasingly more nose heavy while landing.

I'm not seeing that the cg would change with the gear moving backwards?
The way I see it the pivot point don't change, so the cg won't.
Throw a set of scales under the mains or tailwheel and swing the gear forward or aft....I don't see the weight changing?
I can see that it would nose over easier the further aft the gear travels, but not that it would change the balance or feel on landing. Am I missing something?

Well to put you guys at ease on my landing gear, I assume Terry by "compression" you are speaking about the air bags compressing, as the strut or leg does not compress. By the way it is made of 4130 2.5" dia by .250 thickness. Bending is not an issue.
The gear moves backward only to a point of full stop on the air bag mount. If I can figure how to put pictures on here, I can better show this. The criticle point is the location of the axle in respect to the CG. At full forward CG the axle is far enough forward that the there is very little lightening of the tail. Prior to having the stops in place, I accidentaly lowered the plane on it's gear and the tail had only 20#'s on it. The further back the gear went the longer the lever arm and the more it compressed the airbags the further it let the gear go back....you get the picture. The lever arm is measured from the pivot point horizontaly back to the axle. The trick is to limit the aft movement assure no large weight shift.
The tires are lightly filled, 15 psi, and take up some of the initial landing load while the airbags take up the rest.

[Battson offline]

Does anybody know what became of this machine?