airplane construction

Robert M. Gary wrote:
Mike wrote:
Robert M. Gary wrote:
I'm guessing that's why there's wing struts How many bolts secure the
wings to the fuselage?

On the Cessna I don't remember how many "wing nuts" there were holding
the wing on, I just remember the very small area in which the wing
attaches to the body. There must be insane amounts of stress on that
small area of metal.

On the Mooney, there is but one single wing. The spar runs right under
the seats. No one has problems with wings coming off but the Mooney
design makes me more comfortable.

-Robert

The 172 has a 7/16" bolt on the front spar attach, and a 3/8" at
the rear, IIRC without going downstairs and looking it up. Both are in
double shear. The bolt is stronger than the aluminum fittings, and the
fittings are much stronger than they look or need to be. The airplane
is rated for 3.8g positive, with 150% design limits beyond that, and I
can't remember the last time I heard of a 172 shedding a wing unless
the pilot tried to fly through a thunderstorm, in which case he'd have
died anyway. The stabilizer is weaker than the wing in many light
aircraft.
The struts are connected with 1/2" bolts in double shear.

The Mooney's one-piece wing spar is made of many smaller
pieces, all held together with tiny rivets. No stronger than the 172, I
bet. The Mooney's POH should give a g rating for the airframe.

Which reminds me: a friend recently told me of an accident in
the Southeastern US where a new Commercial pilot flew a Monney into a
thunderboomer at night. They found the wreckage scattered far and wide,
and the Mooney engineers that examined the bits and pieces estimated
that the aircraft experienced an upward acceleration of between 20 and
23 Gs. The passenger, complete with seat, went through the bottom of
the airplane and was found some distance behind the rest of the mess.
Even if the airplane had held together the occupants would have been
incapacitated or killed by the damage wrought by the acceleration.

Dan