Counter rotating propellers

In article ,
Raoul wrote:
I've had a questions I'd like to foist upon the collective knowledge
here...

I've noticed that their were many planes during the prop-to-jet
transition years from about 45 to about 55 that used counter rotating
propellers. I'm wondering what the perceived advantage was?

Several: Main one was that the torque effects cancelled out, so that
the aeroplane wasn't always trying to turn itself over/around in flight,
which was getting to be a real pain even with the last generation of
WW fighters, let alone the more powerful ones coming along. I've spoken
to at least one pilot who flew Seafires (the carrier-based Spitfire
derivative) and he was lavish in his praise of the F.47 which used
contraprops - "it flew like a jet" - less so of the earlier
Griffon-engined types. And the Seafires "only" had 2200hp or so - imagine
what the torque effects would have been in something like the Westland
Wyvern (3600hp) without contraprops (and it was no delight with 'em).
A related issue was maintainance (this for multi-engine types): if you
wanted to avoid torque effects you had to have "handed" engines, turning
in different directions on each side (like the Lockheed Lightning or the
De Havilland Hornet), or you put up with the torque effects and had the
mainatainance/suppy gain of n identical engines. Go to contraprops (as on
the Avro Shackleton) and you had four identical engines and the torques
cancelling out.

Another issue was ground clearance - by the generation of fighters which
included the Corsair and its peers it was getting /very/ difficult to
put a big enough prop on the front to handle the power. Contraprops
cut down the size of the prop disc and made for easier takeoffs and
landings (the undercarriage didn't need to be so nose-up).

Seems to me that the added complexity and cost would be a disadvantage.
It's pretty simple with one propeller: Take engine. Fasten propeller to
flange on front. Put on airplane, Fly into the wild blue yonder, All
those gears and driveline parts were mighty complex and, in my reading,
the added complexity was usually the thing that put the plane into the
'world's worst' catagory.

Except that (almost - the Harvard is the exception I can think of)
pretty well all aeroplanes already used geared engines (and had since
rotaries went out of fashion in 1918 or so) - so you already had the
gearbox there.

Another issue is that it makes it easier to combine more than one engine
on one shaft (the fewer shafts the better for aerodynamics, but you might
not want a single enormous engine turning over for cruise, say). The
Fairey Gannet did this - two turboprops driving a contraprop. For takeoff
or speed you ran both engines, for stooging around (the Gannet did ASW
and AEW) you ran on one engine.

I notice that notable post war military aircraft such as the B-36 and
the C-130 (plus more) used one propeller per shaft. If there were an
advantage, you'd think you'd find 'em on a military plane. Yet, if my
reading is correct, the Soviet long-range Bear bomber had
counterrotating propellers.

Chack out the engine powers! The turboprops on the Bear are /big/ -
14000+shp, IIRC. There's no way you could fit in propellors big enough
to take that power and have an aeroplane which could be handled on the
ground - even with the contraprops the airliner derivative (Tu114)
wouldn't fit into normal airport gates..

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?

Not sure whether the Antonev 70 is actually in production yet, but it uses
four big contraprops..

--
Andy Breen ~ Interplanetary Scintillation Research Group
http://users.aber.ac.uk/azb/
"Time has stopped, says the Black Lion clock
and eternity has begun" (Dylan Thomas)