Kitfox abrupt departure sensitivity to low speed stalls

[Av8r3400]

A thin fiberglass leading edge cover, under the fabric.

It does not change the airfoil shape, just make it smooth over the leading edge across the ribs. Similar to the old Avid aluminum leading edge without the oil-canning.

[DesertFox4]

Paul, a couple photos from my build thread that shows highlights of a Laker Leading Edge install. It does slightly change the leading edge by bridging and maintaining the profile between ribs as originally designed by Harry Riblett. As we all know the wing as built without the L.L.E. works exceptionally well in all speeds. The L.L.E. wing does feel different than the stock wing. Certainly not needed for a fantastic performing Kitfox, just interestingly different.
IMG_3090.jpg

IMG_3091.jpg

[av8rps]

Thanks for clearing that up for me. I have seen those before, just didn't know what they were called.

I remember when Avid started doing that with their leading edges. They really make the wing look nice, we just never could determine if they did anything but add weight.

I really like the look of them on the Kitfox wing and would think they may improve top speed as it looks like it would reduce drag on the leading edges. (The Kitfox wing is much cleaner than the old Avid wing, that's why I say that).

[tx_swordguy]

James, while I am a low time pilot and I have an avid not a kitfox I think the differences in the flight envelope between the two are not very far off. While I am all for experimenting, do so after getting a few hours in the plane. I was told by the PO that after 10 hrs I would have it down. While I still feel I am learning every time I climb in, there was indeed a change at the8-10 hr mark where things really started clicking. I still put VGs on the wing and tail at about the 20 hr mark not so much to slow my stall but to keep a more stable feel on the wings right up to landing. It worked for me and the stall breaks very clean (might have dropped stall a hair).As for a climbing spin-good luck. I have the 582 and at 40 I can pop the flapperons and pull up off the deck in under 500' and be 40' in the air almost immediately(again a low time non-STOL trained pilot). I would be more concerned with a spin on landing than taking off. I land and take off on a 1000' grass strip with a power pole on the north end. I practiced for a month at the local airport before ever trying my stip. When I did I made numerous approaches at different speeds and slips before I ever tried putting the wheels on the ground. First landing I dropped over the power lines and slipped to a landing with 300' to spare. I was duly impressed with myself and the plane. Just get in it and fly, from there figure out if and what you want to do to it. Take it for what it is worth, many, many more here with loads more time and experience than I have. listen to them
Mark

[Av8r_Sed]

I have the 582 and at 40 I can pop the flapperons and pull up off the deck in under 500' and be 40' in the air almost immediately
Mark

^^^ This is OK as long as you don't try to continue the climb at that low of an airspeed. People can get in trouble with this design on departure with slow climb speeds. There isn't a lot of momentum in these light birds and if you do stall due to wind shear or whatever, recovery will be very difficult if not impossible. The climb rate at 50 or 60 is still pretty impressive and there isn't much reason for any slower climb.

[tx_swordguy]

I agree 100% I will usually get up about 40' and then let the nose down/ bring in flaperons and pick up speed to get over the power lines. by the time I am over the power lines I am pushing 50+ and climbing much slower but gaining speed. Once I hit 60 I increase my climb angle and hold 60. I only take off to the north over the power lines with a north wind usually only between Nov- april with the temps usually not above 70degrees. All other times I take off southbound with only a barb wire fence at the end. So far it is working out fine. Not saying something cant happen but I feel pretty good about the way things are working out so far. I am pretty particular about my wind patterns taking off to the north though.
Mark

[jamesbdunn]

...while I am a low time pilot

I practiced for a month at the local airport before ever trying my strip. When I did I made numerous approaches at different speeds and slips before I ever tried putting the wheels on the ground. First landing I dropped over the power lines and slipped to a landing with 300' to spare.

Just get in it and fly, from there figure out if and what you want to do to it.

Take it for what it is worth, many, many more here with loads more time and experience than I have. listen to them

Mark

Mark, your experience resonates with my experience with the Varieze; carefully pushing things around near limits to get the feel of impending departure from expected performance; in forgiving situations.

I respect everyone's offered experience. But if I replied individually to everyone, it would be messy; and a bit weird

But as the new guy, I want you to know your contributions are equally appreciated. It's up to me to use common sense to combine everything into a useful course of action; or in-action.

Thanks

[jamesbdunn]

...I will usually get up about 40' and then let the nose down/ bring in flaperons and pick up speed to get over the power lines.

Mark

That's interesting. I was reading an article about a fighter pilot in jet aircraft that studied aerodynamics and found a way to out maneuver his friendly opponents. This technique was later adopted and taught in fighter pilot training. I don't know if it would work in propeller driven aircraft, as these jets are moving at speeds unrelated to an unrecoverable stall because of the massive engine thrust.

But what he discovered was in a clean configuration he could gain altitude much faster by porpoising the climb, instead of a constant climb.

The engine could not sustain the most efficient climb speed, so by porpoising, the aircraft speed transitioned through regions of greater lift while being more aerodynamic in a clean configuration.

For SEL aircraft near stall speeds this is a BAAAADDDD idea.

But once well above stall speeds and with no flaps, I wonder if porpoising at cruise power is as effective as sustained climb at full power?

I remember there was something about the climb profile, but don't remember clearly.

[av8rps]

Another point on this interesting discussion;

We are not talking about identical airplanes here, so we really need to take that into account.. My early Avid Flyer weighed 400 lbs empty and would safely climb out at 45 mph at a 47 degree angle with no issues at all since the stall speed was 22 mph. But it (like Kitfox 1 -3 Models) had a completely different airfoil than later Kitfoxes. That airfoil will fly (and stall) much slower, and land much shorter than the newer airfoil design. So in this discussion it is almost like talking about two completely different aircraft.

By comparison, I climb out in my Model 4 Kitfox amphib at 65 to 70 mph. I can climb at 45 mph, but it doesn't feel right and makes me a bit uneasy since my stall in that configuration is approaching the 40 mph range. So I avoid using techniques like that.

And even though we need to consider the huge variety in our airplanes, this has been a very good discussion that could prove beneficial to all of us.

[PapuaPilot]

[QUOTE=tx_swordguy;61792] I have the 582 and at 40 I can pop the flapperons and pull up off the deck in under 500' and be 40' in the air almost immediately.

I would encourage you do think about what would happen if your engine has a hiccup or dies during this maneuver. I don't think things would end well. Where I work we do not allow simulated Vx power losses during takeoff because we have had a couple of serious incidents doing them. I'll never forget doing simulated power loss at Vy on the amphibious Caravan at 100'. It was almost unrecoverable and the pushover at the top was drastic (to keep it from stalling). It was like going over the top of a roller coaster.

One way to check this would be to simulate it at a safe altitude; note your altitude, slow down to just above stall, add full power, pull on the flaps, pitch up, then cut your throttle and see if it is possible to recover without stalling or going below the initial altitude.