Kitfox abrupt departure sensitivity to low speed stalls

[av8rps]

Interesting info about Mr. Riblett. Pretty cool that someone here on the forum knows him.

Somewhere in my archives I have his letter where he explains to Avid what he did with their airfoil and why, but they never took him up on his suggestion to change their wing. But Kitfox did, which ultimately proved he was right about what he said in the letter. And I guess we can say the rest is history...

[Rooster]

AV8RPS has mentioned Steve Henry a post or two down.
What People must take note of is that he flies upwards of 5 hours per week, I'm told....

[DesertFox4]

I was told by Murle Williams some time ago that Harry Riblett passed away.

I found his obit. in a Delaware paper. See below. He and Murle communicated frequently. I've seen original drawings of new Riblett wing designs in Murles file. Very interesting work. I beleive Harry was instrumental in Murle adding the extrusion on Murle's earliest Kitfox build' wing, a model 3 that was awarded Grand Champion back in the late 80's or very early 90's. This leading edge extrusion was simply a pvc pipe of about 3/4 inch cut in two length-wise and bonded in the proper location to the front spar. My impression is it increased the wing's speed. I hope my recollections are accurate but it has been 10 years or more since Murle discussed this topic with me. I may inquire next time I stop at Murle's to varify specifics. Suffice to say that Harry was very skilled at wing designing. Would have enjoyed meeting him.



" Harry Calvin Riblett, Jr. was born in California on November 14, IMG_3050.JPG1929. He passed away in Wilmington on December 23, 2012.

Harry was a pilot and built two airplanes at home, a Starduster II 150 HP, 2-seat biplane and an 85 HP Piper Cub replica (as a group project with other pilots). He also researched airfoil designs, convinced that safer airfoils would save lives. His first book, "GA Airfoils" shows airfoils superior to the currently available NACA (government) airfoils. Both his first and second book, "Spin Resistant Airfoils", are currently being used by aircraft designers in the Experimental Aviation Association (EAA). Harry's expertise was renowned worldwide and he served as an expert witness on several legal cases involving airplane crashes."

[efwd]

Steve! Do you get "time" from some source in the universe that the rest of us aren't aware of? I mean, the work going on in skunkworks with the carbon fiber and all and you manage this forum with all the research of various stuff. Love it.

[jamesbdunn]

Don't mean to be rude James but get some spin training. I can't recommend it enough.

Based on everyone's input, I'm definitely going to investigate the details of installing the equivalent of a Sportsman Stall kit. Which I guess begins with contacting my local FAA Inspector.

For those who advised against modification, your input was equally as valuable. Providing me with perspectives I might not otherwise have considered. My choice is biased by my personality, to take on new projects.

I understand to avoid a low altitude spin, that about 20 mph of additional speed is desired above Vso before climbing out of ground effect, to offset the likelihood of a tail wind gust; in the case of a headwind, wind dying out; and in case of turbulent crosswinds and different wind directions above the treeline.

On takeoff the likelihood of recovering from a spin is unlikely.

My interest is in being better "equipped" to deal with rogue conditions. And be able to fly closer to the edges of expected performance, without abrupt consequences. I want to feel an expected approach to a flight limit, and have the time and performance resources available to respond.

I have received spin training, and I agree it should be required as part of certification. However, I can see how it might cause the cost of liability insurance for flight instructors to increase. Once a student learns spin recovery, bad judgement might cause more accidents during training. Where the student because of the fun factor, attempts spins during training on their own. Or recently certified pilots taking joy rides with passengers and doing spins without sufficient practiced experience. Hard call, because of legal system, insurance, and human factors.

I remember my first spin. The instructor asked if I studied the procedure; I had. He talked me through entering the spin, but did not prompt me on what to do. I knew what I was "supposed" to do. But my senses were overwhelmed. After struggling a couple of rotations I asked the instructor to recover; which he did in about 8 seconds.

He then did a spin and talked me through what he was doing, and why. He recovered.

Then he had me set up and enter a spin. This time my senses knew what to expect and it was cake. .... More like cake with frosting topped with Skittles !!

I really liked it and asked to do another spin. I couldn't help it ... I yelped Yeeee Haaaa

I did a couple more and our instruction was finished.

I felt so empowered to learn something in so short a time that previously put me on edge, to give me a total feeling of control.

But I'm not arrogant (loathing of others), I know my feeling of control can come back and bite me unless I stay diligent, and learn more from others.

===========

I'm a newbie. So if more experience chimes in here, I certainly take no offense.

When I sold my Varieze the pilot had many more hours of experience than I had. I warned him that to set down on the numbers he had to set up to land long before the numbers and bleed off ground speed because the Varieze floats in ground effect forever if above 70 knots. I warned him of the need to pump the brakes to minimize gear resonance during hard braking, and advised him to do his first landing on the widest and longest runway he can find. But he took off the following day with ice and snow on the short 3000' runway, clipped the top of a tree (witnessed by local A&P) most likely because of excessive braking to steer, flew to near fuel exhaustion to around St Louis somewhere, came in on a short and narrow runway too hot, floated to past the middle of the runway, tried to force it to stop instead of going around, went off the end of the runway into a ditch where a log severed the landing gear and the propeller chopped into the log. I know this because the pilot called me at work and asked how to take off the wings.

I have personal insight as to the importance of listening to experience.

I not only take no offense to your suggestion, I appreciate your concern.

James

[Av8r3400]

James,

First off, do you have a Kitfox now or how much time do you have in one? Or are you in the investigation to buy phase of things?

Second, before delving headlong into fixing a non-problem with an untried, non-solution, fly and get to know the airplane as it was designed. Kitfoxes work and perform very, very well as designed. This current airfoil has been in use on the Kitfoxes for over 25 years and has earned a very good reputation.

Adding 20 mph to your airspeed before climbing out of ground effect is ludicrous. This is not a VariEz. It is a very light and very forgiving airplane that will do just what you tell it to do. If you are flying in conditions of 20+ mph gusts, you need to pick another day to go flying.

Basing your course of action on accident records of questionable people doing questionable things with an aircraft and the trying to design out their mistakes, imo, will only lead to frustration if not outright trouble.

[Rooster]

James,

First off, do you have a Kitfox now or how much time do you have in one? Or are you in the investigation to buy phase of things?

Second, before delving headlong into fixing a non-problem with an untried, non-solution, fly and get to know the airplane as it was designed. Kitfoxes work and perform very, very well as designed. This current airfoil has been in use on the Kitfoxes for over 25 years and has earned a very good reputation.

Adding 20 mph to your airspeed before climbing out of ground effect is ludicrous. This is not a VariEz. It is a very light and very forgiving airplane that will do just what you tell it to do. If you are flying in conditions of 20+ mph gusts, you need to pick another day to go flying.

Basing your course of action on accident records of questionable people doing questionable things with an aircraft and the trying to design out their mistakes, imo, will only lead to frustration if not outright trouble.

WOW!
These are wise words!
One cannot do better than listen to sage advice and then add hours flown, when dealing with a really classy piece of equipment.

There is no doubt about the equipment and its capabilities in this case.

Kind regards
Reid

[jtpitkin06]

The FAA has long had a list of hot items related to accidents. At the top of the list for several years is loss of control. Instructors, check airmen and designated examiners are encouraged to address the problem during instruction and check rides.

The good news is that we are getting better in the experimental community. Loss of control accidents have decreased significantly.

Although slow speed low altitude loss of control is the leading cause of accidents in the Kitfox, it does not mean the aircraft is prone to stall and spin more than other aircraft. The number of accidents per hour flown is actually lower than many other aircraft to include both experimental and certified aircraft.

For those not familiar with the flight characteristics of the Kitfox, do not be alarmed.
In simple terms, the Kitfox is one of the safest aircraft you can fly.

John P
Greenville Tx

[jamesmil]

If I may I would like to add to this discussion on the Kitfox stall spin behavior,
My fox is a model 7 with the "laker fiberglass leading edge" it has the 912uls and 850x6 tires and the speed kit option for the tail.
I have found that with the stick full back and in full stall it is very easy to control a wing falling off with small rudder inputs. Also the ailerons / flaperons remain effective and will pick up the low wing without the rudder, not the right way to pick up a stalled wing on an airplane with just ailerons. In a full power on stalled configuration with half flaps it is still very controllable with rudder in to pick up the wing in fact it shows about 30/32 mph ias. I have tried to spin it but find it hard to get more then a spiral,not a fully developed spin.
I feel that the laker leading edge is the reason my airplane is so docile at slow speeds. This is the only Kitfox I have any time in, it just turned 350 hr, after first flight in April 2012 but i do have about 600 hr, acro time so am comfortable with spins.
A word of advice, " know your airplane" and always have an out.

[av8rps]

Can you please describe for all of us what the Laker leading edge is, and what it does?