Counter rotating propellers

I've had a questions I'd like to foist upon the collective knowledge
here...

I have a few of those "World's Worst Airplane" books and enjoy reading
about the creations of those in the old days who were basically working
by the seat of their pants.

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?

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.

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.

So, that leaves me again with my initial question:

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?

raoul

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)

Andy,



ANDREW ROBERT BREEN wrote:
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?

Great reply.................

Major snip...................

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


IIRC, the An-70 is not a contraprop as such - the D-27 engine is a
twin-spool propfan - and the props are driven by the two shafts, not
through a 'normal' contraprop gearbox.

It has 8 blades in the front row and 6 in the rear - 14 blades per
engine - making a staggering total of 56 blades !!!

It is extremely fuel efficient.........

Ken

"Ken Duffey" wrote in message
...
Andy,



ANDREW ROBERT BREEN wrote:
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?

Great reply.................

Major snip...................

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


IIRC, the An-70 is not a contraprop as such - the D-27 engine is a
twin-spool propfan - and the props are driven by the two shafts, not
through a 'normal' contraprop gearbox.

It has 8 blades in the front row and 6 in the rear - 14 blades per
engine - making a staggering total of 56 blades !!!

It is extremely fuel efficient.........

Wait a sec. If this was such an extremely fuel efficient system, the
short-haul airlines would be banging down the various manufacturers' dorrs
demanding such systems--which they decidedly ain't doing. The prop fan
configuration was tested here in the US a few years back (on a DC-9
airframe, IIRC), and it apparently was found wanting (how much of a problem
in that regard the noise issue is I don't know). The An-70 has had a rather
troubled development history (so much so that the Russians have gotten
rather cold to it), and IIRC one of the major problems has been the
powerplant.

Brooks


Ken

Kevin Brooks wrote:
"Ken Duffey" wrote in message
...

Andy,



ANDREW ROBERT BREEN wrote:

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?

Great reply.................

Major snip...................


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


IIRC, the An-70 is not a contraprop as such - the D-27 engine is a
twin-spool propfan - and the props are driven by the two shafts, not
through a 'normal' contraprop gearbox.

It has 8 blades in the front row and 6 in the rear - 14 blades per
engine - making a staggering total of 56 blades !!!

It is extremely fuel efficient.........


Wait a sec. If this was such an extremely fuel efficient system, the
short-haul airlines would be banging down the various manufacturers' dorrs
demanding such systems--which they decidedly ain't doing. The prop fan
configuration was tested here in the US a few years back (on a DC-9
airframe, IIRC), and it apparently was found wanting (how much of a problem
in that regard the noise issue is I don't know). The An-70 has had a rather
troubled development history (so much so that the Russians have gotten
rather cold to it), and IIRC one of the major problems has been the
powerplant.

Brooks


Ken

Don't shoot the messenger - I'm only quoting what I read .............

From 'Antonov's Heavy Transports -The An-22, An-124/125 and An-70' by
Yefim Gordon, Dmitriy and Sergey Komissarov - No 18 in the 'Red Star'
series.......... purchased yesterday.

"Four ZMKB(Muravchenko) D-27 propfane engines with a takeoff rating of
14,000 ehp and a cruise rating of 6,750 ehp designed by ZMKB Progress at
Zaporozhye. The D-27 is a two-spool engine........

The engines are noted for their high fuel efficiency, the fuel burn in
take-off and cruise mode being 170 g/ehp.h (0.37 lb/ehp.h) and 130
g/ehp.h (0.29 ib/ehp.h) respectively.........."

I don't profess to know what that all means - I am just posting what I read.

As far as the dispute between the Ukraine and Russia over the engines -
again, from what I read - this has now been resolved...

From Air Fleet 5/2003 - "In spite of the RusAF top brass's stance on
the An-70 - (to do with structural flaws in the powerplant) -
representatatives of the Russian government believe that the An-70
trials must be completed 'as sooon as possible'. According to Russian
vice-premier Boris Alyoshin speaking on 15 August - 'there is no reason
for saying that the programme will not be accomplished or Russia is
pulling out of the programme. The commitments Russia made must be met"

Ken

"Ken Duffey" wrote in message
...
Kevin Brooks wrote:
"Ken Duffey" wrote in message
...

Andy,



ANDREW ROBERT BREEN wrote:

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?

Great reply.................

Major snip...................


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


IIRC, the An-70 is not a contraprop as such - the D-27 engine is a
twin-spool propfan - and the props are driven by the two shafts, not
through a 'normal' contraprop gearbox.

It has 8 blades in the front row and 6 in the rear - 14 blades per
engine - making a staggering total of 56 blades !!!

It is extremely fuel efficient.........


Wait a sec. If this was such an extremely fuel efficient system, the
short-haul airlines would be banging down the various manufacturers'
dorrs demanding such systems--which they decidedly ain't doing. The prop
fan configuration was tested here in the US a few years back (on a DC-9
airframe, IIRC), and it apparently was found wanting (how much of a
problem in that regard the noise issue is I don't know). The An-70 has
had a rather troubled development history (so much so that the Russians
have gotten rather cold to it), and IIRC one of the major problems has
been the powerplant.

Brooks


Ken

Don't shoot the messenger - I'm only quoting what I read .............

From 'Antonov's Heavy Transports -The An-22, An-124/125 and An-70' by
Yefim Gordon, Dmitriy and Sergey Komissarov - No 18 in the 'Red Star'
series.......... purchased yesterday.

"Four ZMKB(Muravchenko) D-27 propfane engines with a takeoff rating of
14,000 ehp and a cruise rating of 6,750 ehp designed by ZMKB Progress at
Zaporozhye. The D-27 is a two-spool engine........

The engines are noted for their high fuel efficiency, the fuel burn in
take-off and cruise mode being 170 g/ehp.h (0.37 lb/ehp.h) and 130 g/ehp.h
(0.29 ib/ehp.h) respectively.........."

I believe they have had not one but two accidents ('95 and '01) tied to the
engines and props?

From Pravda in '99 (not the best source, I'd agree--but it was saying the
same thing the Russian AF folks were saying): "Vladimir Mikhailov says that
the plane cannot be put into production because of its imperfect engine D-27
that is "unsafe, short-life and very expensive." Experts think it is
impossible to get the engine into shape."

english.pravda.ru/main/18/89/357/11829_aviation.html

That does not sound like a ringing endorsement of the powerplants.


I don't profess to know what that all means - I am just posting what I
read.

As far as the dispute between the Ukraine and Russia over the engines -
again, from what I read - this has now been resolved...

From Air Fleet 5/2003 - "In spite of the RusAF top brass's stance on the
An-70 - (to do with structural flaws in the powerplant) -
representatatives of the Russian government believe that the An-70 trials
must be completed 'as sooon as possible'. According to Russian
vice-premier Boris Alyoshin speaking on 15 August - 'there is no reason
for saying that the programme will not be accomplished or Russia is
pulling out of the programme. The commitments Russia made must be met"

"Moscow, 15 June: Russia will allocate about R30m for developing the An-70
military transport aircraft in 2004, Leonid Terentyev, director-general of
the Medium Transport Plane international consortium, told Interfax-Military
News Agency on Tuesday [15 June]. "The Russian side will most likely earmark
about R30m [indicated elsewhere by the same source as being $1 million USD)]
for the An-70 development in 2004. Russia is unlikely to provide more funds
in 2004," Terentyev said. He noted that the upcoming meeting of the
intergovernmental Russian-Ukrainian commission was unlikely to achieve a
radical breakthrough with regards to the An-70 programme."

www.gateway2russia.com/st/art_242733.php

That sounds like anything but a strong endorsement of the An-70 program,
which Russian senior defense officials have repeatedly commented of late as
not being a program they are very interested in pursuing. The Russian Air
Force apparently wants nothing to do with it, preferring its cheaper
Il-76's.

Brooks


Ken

In article ,
Ken Duffey wrote:
Andy,

ANDREW ROBERT BREEN wrote:
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?

Great reply.................

Thank 'ee, sir...

Major snip...................

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


IIRC, the An-70 is not a contraprop as such - the D-27 engine is a
twin-spool propfan - and the props are driven by the two shafts, not
through a 'normal' contraprop gearbox.

Aha.. Interesting.
That said, of course, the Fairey P.24-powered Battle and then the Gannet
weren't "classic" contraprops (in the gearbox-split sense), either - both
having separate engines turning the two props - but the props shared an
axis.
I can't remember off-hand how the two engines were combined onto the
contra-rotating props in the Brabazon. There were gearboxes, but where the
drives joined and split I'm not at all sure..

It has 8 blades in the front row and 6 in the rear - 14 blades per
engine - making a staggering total of 56 blades !!!

Curved blades as well, IIRC

It is extremely fuel efficient.........

Didn't the unducted fans trialled about 10 years ago (on DC-9s?)
have two rows of contra-rotating pusher blades?

--
Andy Breen ~ Not speaking on behalf of the University of Wales....
Nieveler's law: "Any USENET thread, if sufficiently prolonged and not
Godwinated, will eventually turn into a discussion about
alcoholic drinks."

On 18 Sep 2004 16:05:44 +0100, ANDREW ROBERT BREEN wrote:
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.

Couldn't you use identical engines, but mount them back-to-front on
one wing?

--
"It's easier to find people online who openly support the KKK than
people who openly support the RIAA" -- comment on Wikipedia
(Email: zen19725 at zen dot co dot uk)

"phil hunt" wrote in message
.. .
On 18 Sep 2004 16:05:44 +0100, ANDREW ROBERT BREEN wrote:
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.

Couldn't you use identical engines, but mount them back-to-front on
one wing?

There's not many engines you could do that with considering
the fittings for the accessory drives and power connections
tend to make the ends different. Then there are the stress loads,
were WWII aircraft engines structural?
I'm sure you could design an engine you *could* do it with
but it's most likely going to be a good bit heavier.

In article ,
phil hunt wrote:
On 18 Sep 2004 16:05:44 +0100, ANDREW ROBERT BREEN wrote:
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.

Couldn't you use identical engines, but mount them back-to-front on
one wing?

Tractor on one wing, pusher on the other? Could be done, I dare say,
though the nacelle design would be interesting to avoid asymmetric
drag or thrust.. Can't help but feel that contraprops might be easier!

--
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)