Peter Twydell wrote in message ...
In article , frank may
writes
Well, counter rotating props eliminate torque on twin engined
airplanes & on at least some, improves the single engine performance &
handling. However, your question really seems to be about
contra-rotating props, which is the case of a single engine driving 2
props on a co-axial shaft, rotating opposite of each other. Same
thing, it eliminates the torque & therefore makes the airplane more
docile. Contra-rotating props are same shaft, same engine, like a late
Seafire or Shack or Bear. Counter-rotating are separate engines, like
the P-38 or F-82 or several twin engine Pipers.


Then there's the case (unique AFAIK) of the Fairey Gannet. The Double
Mamba engine is in fact two Mambas side by side, each driving one of the
two props. One half could be shut down to allow economical loiter.

As far as torque is concerned, although without a prop, don't forget the
Pegasus in the Harrier. Contra-rotating shafts to balance it so that
hovering is easier/possible.


Yes, apart from torque Gyroscopic precesion is a problem. I believe
the WW2 Me 109s nasty swing on landing and takeoff could be traced to
this prime effect with the problem worsened by the placing of the
undercarriage and the narrow track of it. Precesion is the tendancy
of a gyroscope that is spining on one axis and twisted on a second to
react by twisting on the third.

Also the turbulence of the corkscrew prop wash would effect
aerdynamics in nasty way.

AFAIKS if it weren't for the jet engine prop aircraft were heading for
pusher propellers and/or contra-rotating propellers and speeds of
540mph to 560mph.

There are some well researched German poposals by Heinkel
(contra-rotaing tractor) and Dornier (pusher) which would have pushed
piston engined speed on standard WW2 style V12 (jumo 213 and Daimler
Benz DB603 of about 1750 hp) to 540 mph or more. Given in "Secret
Lufwaffe Projects"

Without the jet taking over this is the speed piston engined aircaft
would have reached. They would have operformed the Jets in most areas
till 1947 at least.