GWS Tiger Moth 400 Undercarriage Mod

Been a bit slow on the blog this week. Only a couple of mornings flying, and nothing in particular to report. But there is something I wanted to share. A mate has himself a GWS Tiger Moth 400. I warned him about the snap happy landing carriage. He landed - the undercarriage snapped off, and he decided to "fix it".

Next time I saw his TM he had done this interesting mod on the undercarriage which has made it very strong. The one time I have seen it land with this arrangement there was no landing gear folding - he nosed it over instead... 8-) But I mustn't be too cruel cause he has very kindly agreed to share it with us.

Letting him describe it in his own words:

The plastic bits I slotted into the wing were on the black snap-off sheet which came with the TM. They're the bits used for the landing gear on a GWS Warbird. With the bottom wing off, cut holes right through the wing so that the black plastic bits end about 1cm behind the reinforcing rod. You've gotta make sure you don't accidentally cut near either the servo hole, or the aileron guides.

Then epoxy the black plastic bits in, with the LG wire poke-through holes closest to the front of the wing. Let that set strong, because there's a fair bit of working to get the wire through supporting holes later.

2mm tie-wire (fencing stuff, from the hardware store) was used for the extra struts, and wrapped in 3mm heat-shrink tube. Basically, you cut a nice long bit and straighten it roughly. Cut a piece of heat-shrink the distance between the original LG wheels, and centre that on the wire. You then make two 270 degree twists, measuring out from the middle of the tie-wire, to as close as possible to the ~1cm vertical section at the bottom of the original LG. I used the end of a pair of needle nose pliers to guide that turn.

With the wheels off, you can thread the LG through the loops you've just made in the reinforcing piece. Then put the original LG in its place, with the straight edge of the tie-wire supporting the tail-end of the LG. Roughly bend and measure the wire to where it will go down into the new wing supports, and bend the wire there so it will go up into the wing/fuse. You want this bend to actually put a tiny bit of forwards pressure on the original LG, so it's pre-tensioned prior to landing. Cut the ends off to about the depth of the wing, thread some more appropriate length heat-shrink on each rearwards section, and you're nearly done.

With the LG off the plane again, shrink the heat-shrink tight around the wire. I at first did this on the plane, and both the engine cowl and yellow paint don't like heat. Then back on goes the LG, first in the original slot, then work the new struts into their respective rear holes.