Jay Honeck wrote:

But how did they determine what that useful load was? Did they keep adding
lead ingots until the plane couldn't climb more than "x" feet per minute?

They start by calculating the performance. Then they do take it up with weight.
Maule uses 50lb sacks of lead shot. Frequently the limiting factors are stall
speed and the requirement that the plane be able to climb with full flaps on a
standard day. Maule had to reduce the flap setting on the MX-7-160 after tests
showed it wouldn't do that at max gross.

Did they keep landing it at greater weights until the gear failed? You
always hear stories about the guy who "flew out with a moose in the back" --
which implies that useful load is set conservatively, with at least some
margin or fudge-factor built in.

Any light plane will fly when overloaded. Usually they can get off the ground at
about 1.5 times max gross, and this is sometimes done for overseas ferry
flights. You know from your experience in that Cessna 150 how this affects the
performance -- long takeoff runs and poor climb rates. Sometimes the W&B
envelope gets narrower at high loadings also. IMO, this is not a margin or
fudge-factor.

George Patterson
Why do men's hearts beat faster, knees get weak, throats become dry,
and they think irrationally when a woman wears leather clothing?
Because she smells like a new truck.