Private wrote:
I have read that the P38 Lightning was equipped with counter rotating props
that rotated in the opposite (down going blades on outboard side of engines)
from normal direction resulting in an aircraft with two critical engines and
much increased yaw force when either engine failed.

This is definitely true, in the sense that the props did counter-rotate
opposite to what is now normal. However, the whole critical engine
thing is way overrated. Vmc is a control speed, not a performance
speed. It is quite a bit lower than Vyse, which is as slow as you ever
want to fly with anything close to full power (other than in a training
situation) whether you have an engine out or not. In other words, it's
really not a big deal, which is why it's rare to see counter-rotating
props in anything other than a trainer.

This was done despite
control issues because it resulted in 15 knots extra top speed as compared
with CR props using typical configuration (down going blade on inboard side
of engines)

That doesn't sound right. My understanding is that the reason was to
make the plane more maneuverable (using differential thrust for yaw).
Of course you could get the same effect by using a bigger rudder, but
that would mean more weight and drag, so maybe it boils down to the
same thing - a cleaner, lighter, and thus faster airframe with the same
maneuverability.

It is also my understanding that the extra maneuverability was rarely
used due to the complexity of engine management involved. Late in the
game, a prototype was built with single-lever engine controls. Richard
Bong, one of the most famous of the WWII aces, died test flying it when
an engine blew up.

Michael