wrote in message
oups.com...
I assume he was referring to the increased thrust that was probably
obtained
with the turbine installation, which would create higher forces on the
structure transmitting that thrust to the airframe.

I assumed the same.

Curious you would introduce "run a whole lot smoother" and "power pulses"
then, if you thought those issues weren't relevant. Very odd. Even
stranger that those issues were the sum total of your rebuttal to his post.

The round Pratts were 550hp engines, and the STC'd
PT6A-27 engines are flat-rated to 650hp. While the increased thrust
might add stress, my assumption was the weight reduction of the
turbines and their much smoother operation might nullify the power
increase as it relates to airframe stresses. It seemed a safe
assumption that that's what he was suggesting.

I don't see how the smoothness of the operation of the engine relates.

As far as the weight reduction goes, if anything that would exacerbate the
problem, especially if that weight reduction is permitted to be moved over
to useful load. A heavier engine will dampen the initial acceleration (a
certain amount of the thrust is applied to accelerating the engine, rather
than the airframe to which it's attached), while a heavier airframe (ie
higher useful load) will allow higher forces to occur during that initial
acceleration.

Of course, once acceleration is relatively constant, the only real
difference is the difference in thrust, but again 100 more hp certainly
translates to more acceleration, and thus more force on the airframe.

All that said, as I mentioned before, I would expect certification of the
engine to take all of that into account.

Pete