I find this type of failure very interesting. Someone may correct my
thinking, but this spring design is very common in ground transportation.
Truck leaf springs are usually constructed of several leaves of ever longer
lengths with the terminal on both ends a single leaf usually wound into a
tube that a bushing and bolt is inserted through to attatch to a shackle
then to the frame.
What is wrong with our system that failures are as common as they are.
Could it be that the supplier needs to check his heat treating temps a bit
better? With the number of vehicles out there with essentially this set-up,
why don't we see more broken springs on the side of the road. And before
someone suggests the impact of landing on the spring, wait until you drive
over California's highways paved in potholes.
Regarding a stress riser, I agree with Gary that this may be part of the
issue. The only Grove tailspring failure I am personally familiar with was
right at the forward edge of the tailwheel attachment - a squared off sharp
edge. On my pickiup there is a plastic disk at the end of the aux leaf to,
I suppose, spread the stress over three or so inches rather than at the
immediate end of the aux leaf.
Lowell
----- Original Message -----
From: <gary.algate@sandvik.com>
To: <kitfox-list@matronics.com>
Sent: Thursday, January 01, 2009 9:34 PM
Subject: RE: Everybody ground loops?
Noel
I think my spring was poorly designed - It has two leaves but the upper
(shorter one) was finished with a pointed end, as the lower leaf flexed at
this point it raised considerable stress leading to the failure.
I think I would check any springs out there and if it is finished like
mine I would grind the point off and leave it flat with rounded corners.
I did not see an signs of cracking prior to the failure as it propagated
from below the stress riser and at the bottom of the spring.
I am having new leaves manufactured here in Adelaide and in future I am
going to change them biannually.
Regards
Gary
Gary Algate
Classic 4 Jab 2200
Office Phone: +61 8 8276 7655
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"Noel Loveys" <noelloveys@yahoo.ca>
Sent by: owner-kitfox-list-server@matronics.com
02/01/2009 12:07 PM
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RE: Everybody ground loops?
Is there any NDT way to test the tail wheel spring at regular intervals.
I?m thinking eddy current but not sure if it will work on ferrous metals.
Lots of FBOs have eddy current machines not to mention magnetic flux and
dye penetrate. Dye penetrant should work same as flux... check the
spring every annual.
It may not be perfect but it?s better than ripping up your rudder.
Noel
From: owner-kitfox-list-server@matronics.com
[mailto:owner-kitfox-list-server@matronics.com] On Behalf Of
gary.algate@sandvik.com
Sent: Wednesday, December 31, 2008 4:07 AM
To: kitfox-list@matronics.com
Subject: Re: Everybody ground loops?
I didn't ground loop today but I did break my tailwheel spring. I had just
landed and was taxiing past the main viewing area (of course) when I heard
a crunch and felt a bump.
I knew straight away what had happened and really didn't want to get out
and see the damage to my rudder.
Today was a good day as the spring broke just above the wheel and there
was enough left to hold the rudder about 1/2" above the ground. I have the
2 x leaf spring version and I check it before each flight so there was
little or no warning.
I am going to have a three leaf spring manufactured this week!
Gary
Gary Algate
Classic 4 Jab 2200
Office Phone: +61 8 8276 7655
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?This year, instead of sending you a Christmas card in the mail, we have
made a contribution to UNICEF Australia. We wish you a safe and happy
Christmas".
John Allen <kitfoxfugit@yahoo.com>
Sent by: owner-kitfox-list-server@matronics.com
31/12/2008 05:50 PM
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Everybody ground loops?
In response to Paul Folbrecht <paul.folbrecht@veribox.net> who wrote:
> I'm considering buying either a half share or a whole share in a
completed
> Fox (TD). I have no TD time and while becoming taildragger-proficient
is
> appealing to me, ground-looping one is *not*!
>
> So.... assuming I get a GOOD TG endorsement from a GOOD instructor, and
> GOOD training in the Kitfox, honestly, should I _seriously_ expect to
> ground-loop it at *some* point?
>
> How about this - everybody who's got 50, 100, 200, 500, etc. hours in
> Kitfoxes while never looping raise your hand! :)
The following is just my opinion for what it is worth to try to answer the
question you pose for someone considering transition from heavy nosewheels
to a light taildragger Kitfox. I don't think it is hours that determine
whether a groundloop will occur. I have flown over 5 hours at a time with
only one takeoff and one landing. It seems that there are a number of
factors that are involved, some of which are listed below, not in a
particular order.
1. Design of the aircraft. Width of mains, wider is better (Grove gear is
wider than tube gear on Kitfox). Springiness of gear, stiffness, ability
to absorb shock without bouncing (I found tube gear stiff and bouncy).
Ability to get tail down in flare (difficult in mine, especially with full
flaps). Side area exposed to crosswinds - low on a Kitfox is good.
Visibility over the nose when flaring (none in mine, I use peripheral
vision of the ground plane). Landing speed, slower is better. Speedsters
land faster due to shorter wings and probably the undercambered wing
models (I, II, III) land much slower.
2. Construction of Aircraft. Alignment of wheels (I had to align my tube
gear). Type tires, square shoulder (I had) or round (I have now). Proper
angle of tailwheel. Tailwheel spring slack. Gas line on inside of
firewall that will catch the sole of your shoe when stepping on the brake
(I had to fix that). Type of brakes installed (mine were very weak). Dual
brakes (easier to get an instructor; mine has brakes on LH side only, I
had to learn to fly it from RH side first). Type of tailwheel (I have
never changed mine). Type of prop; the Rotax cannot be idled below 1800;
the Ivoprop I have on it now acts like a speed brake in flatter pitch.
3. Maintenance of Aircraft. Brakes, too good is better but can grab or
nose you over if you apply them hard; too bad won't arrest an incipient
groundloop, sticking can cause one. Tire type and condition; you don't
want a flat. Alignment (of tube gear). Tailwheel condition. Tailwheel
spring (can loosen or break). Tailwheel turning springs and fasteners
condition (failure will leave you without steering). Bungees (if you have
them, you don't want them to break; also be sure you have snare cables
attached). Making sure all control linkages and surfaces are fully
functional.
4. Experience of pilot. Comfort level in the aircraft. Ability to be on
top of it, ahead of it, to make it do what is wanted and not overcontrol
it. Airspeed control; knowing and using appropriate speeds especially in
the area of reverse command over the fence and what is needed for turns
and gusts. Using tailwheel steering until rudder can take over on takeoff
(mine has little rudder authority at first and wants to shoot off to the
left if you lift the tail early). Adding rudder with throttle. Number of
takeoffs and landings, especially recent experience. More make you more in
control. Crosswind technique and experience, amount and strength of wind.
This is needed in mountainous areas where runways are not always oriented
into the prevailing wind. Techniques for gusts. Mountain strips. Type
of surface, hard, soft, grass, dirt, gravel, wet, soft, rough, short,
sloped.
5. Operation. Loaded Weight, heavier lands faster but is not as apt to
"float" if you come in too fast. CG, aft makes lifting tail harder but
helps get tail down on landing. Keeping controls free. Taxiing technique
with wind. Paying attention at all times while moving; no distractions.
S-turns. Pilot condition. You will find your technique flawless at times
and sub-par at other times.
My own observations:
Despite having learned in and flown mostly taildraggers in the past, I
found my Kitfox IV Speedster to be a handful at first. It was not for
beginners, the way it was set up. I never found out why. The Grove gear
finally tamed it. It is not easy to find an instructor for Kitfoxes. The
main tailwheel instructor I know in our area will not fly it, having tried
one he does not want to add a groundloop to his resume. Experience in a
Champ is not the same, since by contrast you can see well out the front,
it lands slowly, takes lots of control movement, and has very forgiving
gear. A Champ is so docile it makes a Cessna 150 seem hard to land by
comparison. The Kitfox is sensitive on the controls, calling for a light
but authoritative touch. It will do just what you ask it to do, whether
or not you realize what you are asking of it. You will consider a Cessna
to fly like a truck after flying a Kitfox.
You can do it if you make the commitment to develop and practice good
technique on every takeoff and landing; lots of people with varying
experience do it successfully as you can see from the list. If you start
on a suitable airport with a well-designed aircraft, assembled and
maintained properly, practice a lot, keep current, pay attention, and
expand your envelope as your experience increases, you should be OK.
Tricky conditions are, if course, riskier. Even if you stay on runways,
cross-countries can present you with challenging conditions for which you
have to be prepared to handle when you are tired. It is not going to be
as forgiving of slamming it into the ground nor will it jerk itself
straight out of a bad landing like a nosewheel-equipped Cessna will.
JA KF IV Speedster @ O70
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