My own Fookadidy

[Av8r3400 1178]

Backstory:  I've been monitoring my tailwheel leaf spring.  After 450 hours and 2500+ landings it was starting to sag.  It's the OEM 2-leaf Kitfox spring, BTW.  I had been noticing that the caster of the kingpin was such that some shimmying was beginning to happen on roll-out.  During my trip to North Carolina, I actually had a vey slow speed ground loop (a brisk walking speed) during a turn off after landing, because the wheel unlocked from shimmying.

 

Anyone with a Maul tailwheel should know that uncontrolled shimmying can cause the wheel to unlock - if the unlocking cam is installed.

 

Well, that's what happened to me last night at one of our EAA chapter Tuesday night fly-ins.   It was being held at an Airport, for a change, so I was landing on a long, paved runway.  The conditions were beautiful.  Calm winds and severe clear.  It was a lovely evening.  

 

After landing the shimmying started, fairly severe this time.  Well, the wheel unlocked and directional control was lost.  By the time the plane came around to the right I was slowed down to 15 or 20 mph at the most, so there was no wing tip contact or any damage at all.  I just got to see where I came from all of a sudden.

 

 

Here's the lessons I want to share:  

 

Tailwheel Springs - When they start to sag, do something to fix the problem.  Once the caster gets to be too much, the wheel will shimmy.  No matter the brand.  They all will.  Period.  End of story.  Shimmying causes problems.  If you have a (crappy) Maul tailwheel it can unlock and you will loose directional control.

 

Factory Brakes - The design of the factory master cylinder mounts means the more rudder you push, the more opposite side brake peddle gets pushed into your foot.  This is why, I believe, I went round-a-bout.

 

 

Today I re-arched the spring.  I also added a leaf to the spring pack from my Mangy Fox's OEM spring (1-1/4" wide).  Now I have a three-leaf set that will not be as likely to sag.  Some modifications were needed to do this, but it was easier than converting to the 1-1/2" spring set I'm using on the Mangy Fox.  (I have an extra three-leaf set for it.)  

 

 

I will report on reassembly and the test flight.

[C5Engineer 1170]

Been there done that but I didn't loop. I wasn't getting the shimmy on dirt landings but anytime I had to land on pavement it felt like the back of my plane was gonna come apart a few times. Lucikly the Matco Dual Fork TW set up puts up with it fairly well. With the 8" Matco TW that's 3.5" wide anything that is out of whack only get's exaggerated. I took my TW spring to a professional shop and had it rearched and hardened. Cost me $50 but my shimmy is gone...mostly...it still wobbles once in a while if I land just right on it. I also changed my landing style just a little bit when landing on pavement. I had gotten used to planting the tail after touchdown by hauling the stick in my lap to get some pressure on the TW for directional control. After lots of fime in the airplane I've learned to relax that pressure a little bit so the tail is a little lighter. That seems to help as well. It's also a good technique for off airport landing on rough stuff. If you watch Steve Henry in his Highlander or Greg Miller in his Bushwhacker Maule they touch down three point because they are super slow but they immediately transistiion to having their tail up in the air and in the case of Steve he never sets his down until he's in his parking spot.

[Av8r3400 1178]

What happened to me just reinforces the Fact that using a fulltime castoring tail wheel in one of these planes is not an option.

If there would have been any wind I don't know what would have happened.