Raoul wrote:

What advantages were being sought through the counter rotating
propeller and, if there were indeed advantages, why aren't they seen on
production propeller driven aircraft today?


Contraprops allow large amounts of shaft-horsepower to be turned into
thrust without making a single-engined aircraft unhandlable through
torque effects. At takeoff, full throttle can be applied with no
unbalanced effect on the aircraft. The extra number of blades also
allows the diameter to be reduced, helping to keep the ends off the
ground and tip speeds lower. They aren't seen today because nobody is
trying to put that much power through propellors.

Peter Stickney gave me some very good answers to a similar question a
little while ago. Here is an extract from our conversation:

------------------------

Peter Stickney wrote:
In article ,
Alan Dicey writes:
Peter Stickney wrote:

iii) How does this work with contraprops? On the face of it they
must interfere with each other horribly, but they seem to fly
quite well.

What you gain is a greater ability for a propeller of a particular
diameter to absorb power, adn the elimination of torque and
P-factor (destabilization of the airframe due to the rotating
airflow from the propeller affecting the airframe).

So, for an increase in power turned into thrust there's an
improvement in flyability and the ability to make the airframe
lighter because it doesn't have to absorb the stresses - they're
balanced out at the source. That explains to me how the Fairey
Gannet was able to shut off one half of the Double Mamba powerplant,
feather one half of the contraprop and achieve better endurance at
patrol speed.

Right. Another example would be the Griffon engined Seafires. With a
single rotation prop, the Griffon Seafires had 5-bladed single
rotation propellers, and were limited to roughly 66% power on takeoff.
This was because of 2 reasons - the Torque/P-Factor would drag the
airplane right into the carrier's island. (A bad idea), and trying to
hold it straight was overstressing the tire sidewalls, forcing tire
changes after only a couple of flights. It's tough when you've got to
explain that you need to pull your ship out of the battle because you
ran out of tires, rather than gas, bullets, or bombs. The contraprop
used on the later Seafire 47s (6 blades, 3 per bank) allowed more
power to be used without the swing, and better propeller clearance.

The same basic engine allowed the development of the Avro Lincoln into
the Shackleton - you could hang Griffons with contraprops in the same
wing center section without changing the location of the engine
mounts. That's basically a Lancaster wing, so they got a lot of
stretch out of it.