"Matt Whiting" wrote in message
...
Roy Smith wrote:
Matt Whiting wrote:

It isn't that hard to overcome the trim on a 172. There are probably
airplanes where this isn't the case, but the 172 isn't one of them.


In theory, it should be possible on any plane. 14 CFR 23.677 (d) says:

"It must be demonstrated that the airplane is safely controllable and
that the pilot can perform all maneuvers and operations necessary to
effect a safe landing following any probable powered trim system runaway
that reasonably might be expected in service, allowing for appropriate
time delay after pilot recognition of the trim system runaway. The
demonstration must be conducted at critical airplane weights and center
of gravity positions."

Like they say, in theory there is no difference between theory and
practice, in practice there is. :-)

I've never flown an airplane where this wasn't the case, but then I've
flown fewer than a dozen different airplanes so I was hesitant to say all.


In the Lear 24B, this would be a very close thing. In a normal landing,
the trim is run almost completely nose up. An attempted departure at this
setting will get an extreme pitch up starting at about 80 knots, with little
warning in advance. It is possible to control the aircraft, but you will be
pushing with more than 50lbs. Depending on the airspeed you let build, it
may take both pilots. Obviously retrimming is your first option, but if you
departed with the electric trim inop or shut off(there is a switch),
retarding the throttles or a very steep bank are your only options to
maintain control. There is no manual trim wheel. The requirement for trim is
massive as speed builds, which it does very quickly.

Al G