Stall proofing the Kitfox – Answer found?

[rogerh12]

A while back I made a posting entitled “How can I keep my kitfox from stalling & spinning in too ????” as I was concerned about stalls and spins, and the possible results on me and the plane. This posting drew 57 comments, but no real answers outside of “keep your airspeed up” and “keep your turns coordinated” . Well, looking through some other post, I appear to have found the answer to my original question (at least on the Kitfox-4). While this solution appears to not 100% “completely” stall proof the kitfox, it does make it highly stall resistant. This posting was actually on Vortex generators. Here is the posting (and notice the effects of VG on stalls):


The vg's that come from Kitfox come with everything you need, right down to a little tape measure. They have vinyl decal material that is a template that you apply to the wing. It makes placement really easy. As far as placement, they're installed further apart near the wing root so that the inboard will stall first and the stall will progress outboard. I installed mine at 8% of cord after talking with the owner of Pacific Northwest Aero who is the owner of the company that the Mcbeans get them from.

Some people don't have much good to say about the vg's, but they made such a dramatic difference in slow flight. The plane is rock solid with very little mush. If you power off stall, with the stick all the way back, the airplane stalls then breaks, and instantly recovers without ever letting the stick forward. Power on the break is more abrupt with little warning. You used to be able to spin mine without much trouble, just stall it uncoordinated. With the vg's, it took three attempts before I could get it to spin. I would stall it uncoordinated and as the wing would drop a little bit it would recover. I've never flown something where you could stall it with the stick back and the ball off to the side and it wouldn't spin, or at least spiral. The plane just kinda slides off to the side, stalling and recovering. I was finally able to get it to spin by stalling it then kicking the rudder abruptly.


This posting was by Nick W. on his Kitfox-4-1200, which is the same plane I am building. I keep thinking VG just seem too good to be true, but when I read Nicks account of the test flight, I have to kinda believe it’s possible to really do something about stalls in the kitfox.

What do you think, too good to be true?
Roger

[Esser]

Airplanes stall and airplanes spin. If the VG's help in slow flight and help with wing drop go for it. But I would never rely on anything but your own capabilities. If you are worried about spins, go take a unusual attitudes course. You'l have a load of fun and walk away a better pilot.

[mr bill]

I owned an Ercoupe in the early 80s that could be made to do a slight stall, but only with power. The secret was a collar around the control wheel shaft, that limited up elevator travel. No stall, no spin. Very simple.

[DBVZ]

I owned an Ercoupe in the early 80s that could be made to do a slight stall, but only with power. The secret was a collar around the control wheel shaft, that limited up elevator travel. No stall, no spin. Very simple.Interesting. So on a stick plane, just adjust so the seat limits travel? Also limits climb.

[Av8r3400]

Will also keep you from flairing to land.

[t j]

I love to slip my kitfox when needed to lose altitude on final approach so always worried about being cross controlled that close to the ground. Rich stowell has calmed my fears on that.

Here is some good information on stalls and spins.
http://www.richstowell.com/documents/12StallSpinMyths.pdf see #3 about slipping and spins.

If you want to get more detail here's a 90 minute webinar on the above topic. at about 6 minutes in he gives very good detail on the dreaded base to final stall spin.
http://bcove.me/ka4iiz5c

[rogerh12]

Esser;

That’s good advice on the extra training. They teach Aerobatics only 30 minutes from here, so I think I will take a barf bag and get some spin recovery training in.

Also, I got my LS license in an ercoupe. Because the elevator travel was limited, I could never really get it to land very slow though, no full stall landings at all, it would just run out of elevator travel first.

Thanks for the input
Roger

[Wheels]

I have them on my plane. The stall is just as mushy and benign as your post explains. I have not tested the spin characteristics as my plane is not approved for spins. I did just complete 10 hours of aerobatic training and will say that if you are a new pilot like me, that training with a good instructor is worth all the time and effort. Just make sure he's more interested in teaching you safety and recovery than impressing you with all his cool tricks. Motion sickness slows your learning.

Maybe someone on the forum can tell you what plane you might train in that has similar spin characteristics to a model IV. I used a Decathlon and you practically have to be a weight lifter to get it to spin, but when it does ... Ride em Cowboy!
My VGs are "Land Shorter."

[kitfoxnick]

What is all this fuss about stalls anyway? With the power to weight ratio of the kitfox a little stick foward and a shot of power and she snaps right out of it. I enjoy flying my plane low and slow and the vgs definitely add to the safety margin but there is nothing to be afraid of.

Nothing can take the place of practice. I think if people would spend the same money on fuel that they spend on their latest wizbang anti stall gadget they would be much better pilots for it.

Stepping off the soap box now

Nick W.

[rogerh12]

Nick;

What’s all the fuss about stalling a kitfox you ask?

Lets see if I can say this delicately.....The Kitfox is super strong and protects the passengers in a steel cage so well that it’s a very safe plane to land badly in. You have to really build up a lot of energy to get enough of it transferred to the passengers to cause real injury. If you check the NTSB database, most (in fact almost all) of the fatalities in a kitfox have occur after a stall & spin near the ground as this is one of the few ways you can build up enough energy to defeat the built in safety features of the Kitfox.

Therefore, theoretically, if you can make the kitfox totally stall proof, you could drop the fatality rate of the plane down to darn near zero for all future flights. And that would be a wonderful thing (and thus all the fuss over the VG and their effect on the kitfox stall charicteristics).

Roger

[Esser]

You make a plane "stall proof" (which isn't even possible) and you lose aspects of controlled flight. Fly your airplane properly and you never have to worry about a stall spin turning on final. In Canada you have to do spins as party of primary flight training which is something I think they really should do in the states. It teaches you how to recognize before you enter a spin, how to pick up the wing with rudder and not aileron so you don't make it worse, and it teaches you how to recover confidently so well as practice. Now I know I am not going to change the FAAs mind but if you have the ability to go train with some spins it's money well worth and you don't take away from the handling of your plane. Bottom line if people are scared of spins and stalls then they are scared of flying and maybe should stay on the ground.

Modern Airliners are "Stall Proof". Air France 447 mushed down in a nose up attitude at 11,000 fpm because the pilot could not realize he was stalled and on the CVR was heard saying I don't know what is happening. That is a case of a pilot who lost the touch of how to actually fly because of reliance on airline procedures and aircraft safety features instead of the basics of piloting.

Just because your elevator limits your angle doesn't mean you won't stall. In fact regarding the ercoupe in AOPA mag they just wrote an article on how most owns of the ercoupe remove the elevator travel restriction.

[Geowitz]

Closest your gonna get to stall proof is to lighten up your airplane. Go with a lighter engine that can swing a bigger prop and create more static thrust, take off all the modifications except the vortex generators, and fly the plane.

[akflyer]

If you try to make something idiot proof, they just build a better idiot.

[HighWing]

Loved the last three posts. Especially Esser's

...pilot could not realize he was stalled and on the CVR was heard saying I don't know what is happening. That is a case of a pilot who lost the touch of how to actually fly because of reliance on airline procedures and aircraft safety features instead of the basics of piloting.

It reminded me of a conversation I had with a neighbor, a retired United 747 captain who flies a Baron and a Christen Eagle in his spare time. He said there was one scenario that most airline pilots failed in the simulator. Shut off all the instruments and radios - engines still good - point a finger at the airport and tell them to put the airplane down there. Most could not do it.

Regarding the NTSB reports on stall/spins. The airplane didn't initiate the conditions leading to the stall/spin. The pilot's control inputs put the airplane into the stall/spin. I would suggest that the tone of most of the comments would suggest that it is the pilot that needs to be stall/spin proofed, not the airplane. My current project is stall proof. I will do en engine start in the next few days, and it will remain stall proof until it leaves the ground. Maybe that is the real answer you are looking for.
Lowell

[rogerh12]

Closest your gonna get to stall proof is to lighten up your airplane. Go with a lighter engine that can swing a bigger prop and create more static thrust, take off all the modifications except the vortex generators, and fly the plane.

To add to that; one other improvement for exiting a spin more quickly is to increase or make more effective the portion of the rudder below the horizontal stabilizer, as in a spin this area of the rudder is still clean air (as discussed in Kit Planes a few months back). On the kitfox, adding a gap seal to this area would seem to be one solution to increase the effectiveness of the rudder and aid in recovering from a spin more quickly, if needed.

Roger

[szicree]

Roger,

With all due respect, do you think you're the first person in the 100+ years of aviation that thought to "stall-proof" an airplane? It's been tried a hundred different ways by many EXTREMELY knowledgeable engineers and has acheived only marginal success. The fact is that it's just not that big a deal if the pilot has adequate training. Go out and get some acro/spin trainning and you'll see that the inadvertant stall actually requires some pretty gross mishandling of a well designed airplane. The problem with most primary training is that it only teaches how to avoid the edges of the envelope without ever actually discovering where they are. It's sort of like wondering how fast you can take a corner in your car without spinning out. You won't know until you do it. The time/money/mental energy spent on fixing something that ain't broke would be MUCH better spent on training. History has borne this fact out quite well.

[rogerh12]

Steve;

Funny enough, when the new Cessna 162 came out (we have one for rent here locally), I was all crazy about flying it and as reading all I could on it, I even downloaded the flight manual. It was Plane and Pilot magazine I think that had the most interesting flight test in the 162. They could not get it to stall. The test pilot tried to stall it power on, power off, crossed controls, you name, they tried it but it would just dip the noise and start flying again. So I guess that’s where I got the idea that a plane could be made stall-proof, in practical flying terms. But that is not what I am after with the kitfox, just improving the stall characteristics so a spin is less likely to result.

From the responses I have seen on this posting, many pilots believe that good training and proper control of the aircraft will keep themselves from planting the aircraft into the ground, and I quite agree that these items are key. Furthermore, I for one am interested in making my Kitfox as safe as reasonably possible and am encouraged by the improvements to its stall characteristics that Vortex Generators seem to make. Additionally, I think I will continue to looks for ways to the improve safety of my Kitfox (including more training for the pilot) and I invite other to do the same and to share their imporvenents with all others.

Roger

[Geowitz]

Your title says "Stall Proof", not spin proof. If you don't enter the stall in the first place you can't spin the plane.


Closest your gonna get to stall proof is to lighten up your airplane. Go with a lighter engine that can swing a bigger prop and create more static thrust, take off all the modifications except the vortex generators, and fly the plane.

To add to that; one other improvement for exiting a spin more quickly is to increase or make more effective the portion of the rudder below the horizontal stabilizer, as in a spin this area of the rudder is still clean air (as discussed in Kit Planes a few months back). On the kitfox, adding a gap seal to this area would seem to be one solution to increase the effectiveness of the rudder and aid in recovering from a spin more quickly, if needed.

Roger

[Geowitz]

That dip of the nose IS a stall and if it's sitting at the airport right now it's stalled right now.


Steve;

Funny enough, when the new Cessna 162 came out (we have one for rent here locally), I was all crazy about flying it and as reading all I could on it, I even downloaded the flight manual. It was Plane and Pilot magazine I think that had the most interesting flight test in the 162. They could not get it to stall. The test pilot tried to stall it power on, power off, crossed controls, you name, they tried it but it would just dip the noise and start flying again. So I guess that’s where I got the idea that a plane could be made stall-proof, in practical flying terms. But that is not what I am after with the kitfox, just improving the stall characteristics so a spin is less likely to result.

From the responses I have seen on this posting, many pilots believe that good training and proper control of the aircraft will keep themselves from planting the aircraft into the ground, and I quite agree that these items are key. Furthermore, I for one am interested in making my Kitfox as safe as reasonably possible and am encouraged by the improvements to its stall characteristics that Vortex Generators seem to make. Additionally, I think I will continue to looks for ways to the improve safety of my Kitfox (including more training for the pilot) and I invite other to do the same and to share their imporvenents with all others.

Roger

[Esser]

If that "test pilot" couldnt stall it he isn't earning his pay. I guarentee you that with the stick full aft and the throttle chopped the wing is not producing enough lift to hold the airplane in the air. The nose does not have to drop to be a stall. That is jsut a design consideration with forward c of g. You can mush all the way down with your nose up and you are still stalled. The nose drop is part of the stall recovery. I remember reading in your other spin proofing post that you were considering moving the C of G aft. This is probably the worst thing that you can do because it can actually make a stall or spin unrecoverable. I can understand you want to make your plane more safe but honestly to me it sounds like you are making your plane more dangerous with very little resale value. And I don't jsut mean with the stall proofing. Maybe I am going out of line here but in other threads you have talked about a lot of mods that are unproven and increase weight where weight doesnt need to be added including a heavy engine. I'm not trying to put you down or defeat your dream but you bought a kitfox cause I am sure you heard it's a great plane and a lot of fun. You can't guarentee your plane will be fun and great to fly with unproven mods. I just don't want to see you get hurt. And I honestly mean that. I'm not trying to take the wind out of your sales. You are obviously an accomplished builder. You have built something like 7 planes? But reading sommething in a magazine and applying it to a different airframe doesnt always apply. Like I said, if I offended you I am sorry but I have been thinking this for a bit and like I said. I don't want to see you get hurt as the outcome.

[rogerh12]

Esser & Geowitz;

I really have not separated "stall" and "spin" very well in this posting, that's my bad, they really it should be disussed as separate topics in this forum. As for flying with lots of unproven mods, I certainly understand there are builders out there that really just want to make the "factory build" plane in there own home, and that's fine for them. But for me the E in EAA means something special (Experimental), I guess I am just more of the experimenter type (kinda like the wright bothers) and through experimentation improments can be made.

Roger

[jiott]

Admittedly small improvements to stall characteristics can probably be made on the Kitfox, but I agree more with stall/spin proofing the pilot as has already been said. IMHO there are really only two things a pilot needs to become proficient at to stall/spin proof himself: Fly angle of attack and Fly coordinated.

Stall only occurs at a given angle of attack which is constant for an airplane in a given configuration. It is independent of airspeed and most other factors.
If you fly coordinated (ball centered) you will never spin, even if you stall.
Jim

[Paul Z]

Stalls and Spins occur when you are flying. If you park it in the hanger , the problem is solved! I all depends on how much you want to fly!

[wannafly]

seeing as parking in the hanger is not an option for me...I read these posts and it gets me thinking about it again. I have a IV speedster with VG on the wing and under the stab. I have done many stalls with my kitfox at altitude in every possible configuration. Differant flap settings, skid ball off to the side, steep turns, power on and off, and have yet to get it to spin. I took a couple of hours spin/recovery training in a cessna 150 so I know what it looks and feels like in a cessna. When I try to duplicate it in my Kitfox it just seems to "mush". Even in a steep turn the top wing stalls first(depending on rudder position) and it seems to just fall ahead. My altitude loss is minimal. If I wait with adding throttle it is maybe 200 feet max. If I add throttle its not even 50 feet. So what am I doing wrong. I ask because I want to find out. I don't want to be on a slow final and find myself spinning in. What am I missing? I would like to know what it feels like to be better prepared if it does happen.

[Esser]

seeing as parking in the hanger is not an option for me...I read these posts and it gets me thinking about it again. I have a IV speedster with VG on the wing and under the stab. I have done many stalls with my kitfox at altitude in every possible configuration. Differant flap settings, skid ball off to the side, steep turns, power on and off, and have yet to get it to spin. I took a couple of hours spin/recovery training in a cessna 150 so I know what it looks and feels like in a cessna. When I try to duplicate it in my Kitfox it just seems to "mush". Even in a steep turn the top wing stalls first(depending on rudder position) and it seems to just fall ahead. My altitude loss is minimal. If I wait with adding throttle it is maybe 200 feet max. If I add throttle its not even 50 feet. So what am I doing wrong. I ask because I want to find out. I don't want to be on a slow final and find myself spinning in. What am I missing? I would like to know what it feels like to be better prepared if it does happen.

If you want to 'make it' spin try a power on stall (30% throttle max)so your engine is naturally torquing the plane to the left. Climb moderately steep to bleed off the speed, as soon as you feel it about to break, kick in full left rudder to help enter the spin and you will have one fun time on your hands. If you do this in a 172 you go inverted on the wing drop. If you use right rudder instead you will counteract the torque from the engine and it will be pretty docile.

Be safe and have fun!

[DesertFox6]

Oooookaaayyy, Alpha Fans; let's take a slow look at this "spin-proofing" thing. At the risk of getting errantly entwined in flight control techniques, I should recap what several have already so succinctly said: "No stall; no spin."

With VGs on board, or better yet leading edge slats/slots on the wing, you're gonna have a devil of a time getting the wing to stall and then KEEPING IT STALLED long enough to induce the yaw rotation required to enter a spin. See the sidebar on page 14 of the March 2012 issue of KITPLANES for a short, spiffy, comparison of VG and slat/slot leading edge technology.

What some of you are experiencing with your VG-equipped birds is a wing that not only stalls at a much higher angle of attack, but also one that re-enters an unstalled state so much sooner than a "slick" wing will, that you don't have time to fully develop the combination stall/auto-rotating moments needed to enter, let alone sustain, a spin. This comment applies equally to "speedster" style tail feathers as well as a "flat-wrapped" empennage but the speedster-style aerodynamics are more effective by design. The VERY short time lapse between reaching the airflow separation point at the VG-altered critical angle of attack and reestablishing usable, controllable airflow over the wing and stabilizer is an effective deterrent to entering a spin...as some of you have evidently discovered. :rolleyes:

Again, I'm not going to go into a "how-to" program to force a spin with slat/slots/VGs as many factors involving your individual aerodynamics and CGs will obviate as many techniques as would be validated. Don't wanna go there; that's where "blogging" stops and "briefing" begins.

So, have we found a stall-proofing fix? No way. A spin-proofing fix? Not really, but it will do until we learn more about flight dynamics by flying our own airplanes and getting some of the same high-alpha, post-stall, handling experience our Canadian compatriots get as a regular part of their basic flight schooling. I'm flat embarrassed that U.S. civil flight training programs are so lame by comparison.

Really, I can't stress enough the advantages of taking unusual attitude (aka "upset") training from a credible instructor experienced in aerobatics; NOT one of your local FBO 250-hour, spam-can CFI wonders. You owe your families, your lovingly-crafted machines and your own pink bodies nothing less. ;)

"E.T."

[wannafly]

ET

thanks for the post...it clears a few things for me...everyone have a safe day.