Thorp Air Command - T18.net

I was flying my friends thorp yesterday and upon landing his planes tail wheel pops off the ground in fairly short durations, this is after it is below stall speed. It has done this since day one, and it is worse when the brakes are applied. The tail wheel has been changed so that is not the culprit, springs have just a little slop, but not much I have never encountered the problem with mine so I was wondering if any one else has had the problem or might expound on the remedy. It is standered body, non folding, 180 hp.

Lance

Just curious, Lance... what kind of tail spring & tailwheel? When brakes are applied the tail is going to "get lighter" of course. I'm assuming proper technique with enough elevator to hold the tailwheel on the ground. The tailwheel has been changed, but still should be considered if it's out of balance. A stiffer tailspring will be more "bouncy" than a softer one. Then, of course, the runway surface conditions. Those are just the first things that come to mind. I have a "standard" flat leaf spring and will get a little tail "skipping" sometimes. That may be diminished with a rod type spring.

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

I'd look at weight and balance. There is no reason for a tailwheel to leave the runway below stall with the stick aft. I was able to raise mine with the stick aft only once during extremely heavy braking.
Cubes

I'm with Cubes on this one. My current airplane is on the forward side as far as CG goes and I still have to work at pulling the tail off the ground. Not sure what prop you have but a 180 with a metal prop (especially with a CS) starts off at a disadvantage regarding weight on the tail.

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Lee Walton
Houston, TX
N51863,N118LW
KEFD

Tail wheel spring is flat,prop is wood, C/G is probably a bit forward because the owner is a bit on the heavy side and with both of us on board n baggage there is no tendency to be tail heavy like mine is,I have an O-290 in mine. I thought about the tail spring and will bring it up to him I have never encountered the problem with mine, if I can sort it out for him he might keep it, I keep instilling all of the T-18 s virtues, this is the set up currently

Lance, the old school leaf spring does have a life span. That one looks to me like its gone flat. My advice is that it's time to upgrade.

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Lee Walton
Houston, TX
N51863,N118LW
KEFD

Lee, what about the length n angle any thoughts?

Lance

Of primary concern to me is that the right sping clip is about to come off!

The tail spring may be getting weak and going flat on you. You would be surprised how much it dearches with someone in the plane. My plane has started to tail bounce some after landing. I'm going to have to get someone to sit in mine while I look at it.

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Bob Highley
N711SH
SN 835
KLAL

Bob, I caught that as well n fixed it after I took the pics today. How long has your tail spring been on? And is it flat?

Lance

Mine is a round one, but it has been on over ten years or more.

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Bob Highley
N711SH
SN 835
KLAL

I do have spring kits available. Is the runway grass? Is it in bad condition?
Cubes

No cubes it asphalt, r they flat springs

How's the weight and balance, nose heavy? full aft stick?
The tail wheel has hit the rudder. soft spring?
Check the spring mount at the fuselage, internal supports?
I would install AN42 eyebolts rudder horn and tailwheel to obtain a straighter spring alignment
mount a camera on the tail

Thanks Bill for the input hadn't thought of the camera

Search Ebay for borescope camera, they are about $12.00 and run on a USB port