Wed May 23, 2018 1:27 pm
#1613231
It has nothing to do with levers or where the weight is positioned.
The simple fact is that an aeroplane weighing ~ 1,700 lbs will start to lift off the ground when the air flow over the wings reaches about 65 knots. This is for a TB. Maybe a bit higher because the flaps are retracted.
Note that the 1,700 lbs was the basic empty weight. Given that the same aircraft will lift off when weighing 2,535 lbs (MAUW) and airspeed only needs to be a few knots faster, it's fairly easy to see that adding 120 lbs of ballast will not make any real difference at all. And ballast is all it is - you may as well put the extra weight inside the cabin for all the difference it makes. Tying it to the underside of the wings might make it look like the aircraft is being 'held' down, but all you've done really is add weight, which is why high wing aircraft usually take off perfectly happily with concrete-filled tyres hanging under the wings.
To actually prevent an aeroplane lifting off in a sustained wind that exceeds the airflow across the wings necessary for flight, you need equipment that can withstand the strain of a 1,700 + lb object attempting to move. Remembering the basic forces in flight, lift opposes weight, so for this object the lift force will be a minimum of 1,700 lbs. Your kit needs a breaking strain of more than 1,700lbs, which in practical terms means ground anchoring based on metal set in concrete. Even then, your straps/ropes will probably snap when exposed to such a sustained force, unless you've bought high-breaking strain line designed for sailing boats. Anything less than metal-in-concrete will be pulled out of the ground like it wasn't there.
While not many tie-down systems will withstand full-on attempted flight, what they are very good for is stopping the aeroplane bucking, tilting and being blown around in winds which are insufficient for causing flight but strong enough to cause it to roll, or tip, or come free of the chocks, or whatever.
Schrödinger's cat walks into a bar. And doesn't.