Tie-Down Weathervaning

[JJ Campbell]

I have a storage box with an old tire on top sitting under my LSA's tail to prevent tail strikes. Occasionally when I get to the plane, the tire is on the ground and the tail is to the side of the storage box. Also, the chocks have been jerked askew. Would purchasing a set of chocks for the other main wheel solve this problem?

[JimParker256]

If you're currently only using a chock on a single main gear, then by all means, get a second set to chock the other main. When it comes to chocks, a homemade set of chocks with a length of rope tying them together works just as well as the $50 set you can buy from a pilot shop. That 2nd chock will help to avoid weathervaning, but you'll also need to have the wings firmly tied down, with the tie-down lines running as vertically as possible (no fore-aft slant). If you can roll the plane forwards or backwards with the tie-downs in place, you're guaranteed to experience weathervaning... Chock the wheels only after you've got the tie-down lines arranged as described above.

And speaking of tying down the wings, be sure to take up all the slack in the tiedown lines. Do not leave slack in those lines. The folks who claim leaving slack in the lines avoids "shock" impact from wind gust are 100% incorrect in their belief. Any slack in the tie-down lines allows the wing to move up and down, thus developing vertical momentum prior to reaching the full length of the tie-down when a gust lifts the wing. At that point, any engineer will tell you that the force on the tie-down ring is MUCH higher than just the lift forces resulting from the airflow over a properly tied down wing surface...

You can prove this to yourself by using a piece of string and looping it over your arm. Tie it to a fixed point, and have someone else apply upward pressure to your arm... When the string is taut to begin with, the force is small. But leave a couple of inches of slack, and you'll feel the "bite" from the string as your arm extends to full string length...

[JJ Campbell]

Thanks Jim! I have a second set of chocks on order.