Counter rotating propellers

[Raoul]

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

[ANDREW ROBERT BREEN]

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)

[phil hunt]

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)

[Fred the Red Shirt]

Raoul > wrote in message >...
>
>
> 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?
>

One object of the exercise, I think, was to straighten the airflow
to get more trust from the same power. The idea is that the energy
that goes into making the air go 'round and 'round is wasted and if
the air can be pushed straight through the propulsion device then
it will be more efficient.

Two problems with counter rotating propellers are:

1) The airflow into the second propellor is turbulant which impairs
the efficiency of the second propeller.

and

2) The counter-rotating propellers put energy into spinning
the air and then put more energy into 'despinning' the
air. No energy is regained by straightening the flow.

IIRC ducted fanjets do spin the outerflow counter to the inner
flow through the turbine. I don't think that improves the
efficiency, rather it reduces the net torque on the aircraft.

There have been successful designs that used seperate engines to
spin a fore and aft propeller, the DO-335, the Cessna-337 and
it's military equivalent that you seen in the movie _Bat 21_, I
forget the designation, O-something.

These use counterrotating engines so that there is no net torque
on the fuselage, which improves handling rather than efficiency.
There is an additional advantage in that putting two engines inline
allows the use of the power of another engines without the additional
drag of another nacelle. I think Rutan has a GA aircraft with a
similar configuration to the DO-335.

--

FF

[frank may]

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.



Raoul > wrote in message >...
> 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

[Ken Duffey]

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

[Kevin Brooks]

"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
>

[Alan Dicey]

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.

[Peter Stickney]

In article >,
Raoul > writes:
> 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?

Other folks have been covering aspects of this well, so I'll leave out
the long treatise.
There's one things that is being messed. Since a contraprop allows
more power to be absorbed by a smaller siameter propeller, the tip
speed of the propeller is lower. This is important, since teh
efficiency of the propeller drops sharply as teh flow over the
propeller goes transonic and supersonic. Since the propeller tip
speed is the vector sum of teh propeller's rotational speed adn its
forward airspeed, it allows better overall efficiency at higher
speeds.
The Tu-95 uses this in two ways. Not only does the contraprop cut
down on the propeller diameter, but the props are geared to turn at
about 760 RPM. This allows that big meatgrinder to churn along at
Mach 0.85. (Which allows it to outpace a Tornado in dry (No reheat)
thrust.)

--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster

[John Keeney]

"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.

[Peter Twydell]

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.
--
Peter

Ying tong iddle-i po!

[Cub Driver]

Even by 1940, the world's air forces had discovered that there was a
problem with the more-powerful engines that were coming on line:
they'd drive the propeller too fast. Once the tips go trans-sonic, the
prop loses efficiency. So they went from two-bladed to three-bladed
props, and then to four-bladed. And they made the props longer. But
there are limits to both these solutions. Thus the notion of having
two sets of propellers, rotating in different directions.

On prop-jets these days, you routinely see multi-bladed propellers.I'm
not sure why airframe manufacturers didn't go in this direction for
warplanes, but perhaps it has to do with the power output of a plane
under combat conditions--that is, a seven-bladed prop will work on a
transport but not on a fighter. Dunno.

You're certainly right about the complexity of the counter- or
contra-rotating propellers.

all the best -- Dan Ford
email: (put Cubdriver in subject line)

The Warbird's Forum www.warbirdforum.com
Expedition sailboat charters www.expeditionsail.com

[ANDREW ROBERT BREEN]

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)

[ANDREW ROBERT BREEN]

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."

[ANDREW ROBERT BREEN]

In article >,
Peter Twydell > wrote:
>>
>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.

Unique in production, but didn't the Blackburn prototype offered for the
same spec have the same arrangement? And before that, of course, there was
the Fairey P.24 Prince engine (essentially a V12 and an inverted V12,
each driving its own proellor on the same axis) - that was trialled in
a Battle (which was said to have a fairly startling performance). It
was offered to Republic as a powerplant for the P47, but got canned
as the Min. of Supp. didn't want Fairey trying to do too many things at
once.

--
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)

[Ken Duffey]

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

[M. J. Powell]

In message >, Peter Twydell
> writes
>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.

Wasn't the Gannet designed for naval officers to fly standing up?

Mike
--
M.J.Powell

[Peter Twydell]

In article >, M. J. Powell
> writes
>In message >, Peter Twydell
> writes
>>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.
>
>Wasn't the Gannet designed for naval officers to fly standing up?
>

It could well have been, but I bet they couldn't have done it with the
same flair as Stringbag display crews do it now: White Ensign flying and
the Observer and TAG saluting to the side.
http://www.stringbag.flyer.co.uk/rnhf/images/ls326_6.jpg is the best I
can find at the moment.

--
Peter

Ying tong iddle-i po!

[Kevin Brooks]

"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
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
[i]
>
> Ken
>
>
>

[M. J. Powell]

In message >, Peter Twydell
> writes
>In article >, M. J. Powell
> writes
>>In message >, Peter Twydell
> writes
>>>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.
>>
>>Wasn't the Gannet designed for naval officers to fly standing up?
>>
>
>It could well have been, but I bet they couldn't have done it with the
>same flair as Stringbag display crews do it now: White Ensign flying
>and the Observer and TAG saluting to the side.
>http://www.stringbag.flyer.co.uk/rnhf/images/ls326_6.jpg is the best I
>can find at the moment.

Lovely!

Mike
--
M.J.Powell

[Ken Duffey]

Kevin Brooks wrote:
> "Ken Duffey" > wrote in message
> ...
>
>>Kevin Brooks wrote:
> I believe they have had not one but two accidents ('95 and '01) tied to the
> engines and props?

"10 February 1995.........Approximately at 17.30 local time, when
executing a manoeuvre not envisaged by the mission assignment, the An-70
collided with the An-72G that was flying ahead of it. The An-70 fell
into a wood near Velikiy Lis ....disintegrating utterly"

27 January 2001.......... at Omsk for cold-weather trials .... "Suddenly
the engine indication and crew alerting system (EICAS) indicated the
failureof starboard inboard engine; 20 or 30 seconds later the port
outboard engine cut as well..........

The accident investigation commission panel completed its work in March
2001......

.....stated that immediately after takeoff an overspeeding of the No 3
(starboard inboard) engines propfan occurred and the FADEC shut the
engine down. In so doing the second row of propfan blades failed to
feather due to a broken pipeline supplying oil to the blade pitch
control mechanism in the propfan hub .........The crew increased power
output of the other three engines, but at that moment the FADEC shut
down the No 1 (port outboard) engine....."

There is more - but from the above you can see that it has had two
crashed - one due to a mid-air collision with the chase plane, the
second due to a failure in the propfans - which has apparently been
fixed to the satisfaction of the Russians.

In neither case was the engine to blame.

The Ukrainian/Russian An-70 is a troubled program - but don't write it
off just yet!

Ken

[Kevin Brooks]

"Ken Duffey" > wrote in message
...
>
>
> Kevin Brooks wrote:
>> "Ken Duffey" > wrote in message
>> ...
>>
>>>Kevin Brooks wrote:
>> I believe they have had not one but two accidents ('95 and '01) tied to
>> the engines and props?
>
> "10 February 1995.........Approximately at 17.30 local time, when
> executing a manoeuvre not envisaged by the mission assignment, the An-70
> collided with the An-72G that was flying ahead of it. The An-70 fell into
> a wood near Velikiy Lis ....disintegrating utterly"

You are right there. The engine problem had arisen on the previous flight.

www.flug-revue.rotor.com/FRheft/FRH9711/FR9711b.htm

>
> 27 January 2001.......... at Omsk for cold-weather trials .... "Suddenly
> the engine indication and crew alerting system (EICAS) indicated the
> failureof starboard inboard engine; 20 or 30 seconds later the port
> outboard engine cut as well..........
>
> The accident investigation commission panel completed its work in March
> 2001......
>
> ....stated that immediately after takeoff an overspeeding of the No 3
> (starboard inboard) engines propfan occurred and the FADEC shut the engine
> down. In so doing the second row of propfan blades failed to feather due
> to a broken pipeline supplying oil to the blade pitch control mechanism in
> the propfan hub .........The crew increased power output of the other
> three engines, but at that moment the FADEC shut down the No 1 (port
> outboard) engine....."
>
> There is more - but from the above you can see that it has had two
> crashed - one due to a mid-air collision with the chase plane, the second
> due to a failure in the propfans - which has apparently been fixed to the
> satisfaction of the Russians.
>
> In neither case was the engine to blame.

OK, the "powerplant" was at fault. Which has had *lots* of problems:

"Having 386 flight hours An-70 demonstrated more than 382 serious faults, 52
events of in-flight engine shut-down including 30 afterburning shut-downs
and 22 without afterburning, - noted V.Mikhailov. - And there is one more
aspect of An-70 a/c problems - noise ICAO requirements. Should we produce
one hundred of these machines they will be allowed to operate between Russia
and Ukraine only." "There is possibility to cut down noise level in
turbo-jet aircraft. But it is quite difficult to do it with propfan engines.
If for example to space engines from each other we can miss all advantages
of the engines", - said V.Mikhailov.

www.tupolev.ru/English/Show.asp?SectionID=60&Page=2

That was the commander of the Russian AF commenting there.

>
> The Ukrainian/Russian An-70 is a troubled program - but don't write it off
> just yet!

Nor would I endorse it is being stae-of-the-art and exemplfying truly
wonderful powerplant design and operation.

Brooks
>
> Ken
>

[Eunometic]

(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?


Dornier made an amphibious flying boat known as the Do 26 that used
this technique. The rear engines even tilted up 13 degrees to keep
them out of the water during takeoff. It was a pretty aircraft.

Becuase the Do 26 was powered by diesels it could be refueled at any
port with diesel and it had an enormous range for a pre war aircraft
of 5500 miles.

I used to dream of taking one on a round the world trip refueling in
yacht ports as we go.

[Eunometic]

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.

[Eunometic]

(Eunometic) wrote in message >...
> 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.

This is the Heinker P.1076 a piston engined aircraft with a speed of
potentialy 546 mph based on refined aerodynamics, evaporative steam
cooling in the wing leading edges and contra-rotating propeller.
http://www.luft46.com/heinkel/hep1076.html

It would have been an awesome piston engined fighter opperating on
only a little more power than a Merlin.

This is the Dornier managing 514 mph on the same power:
http://www.luft46.com/dornier/dop247.html

This is a single contra rotating Dornier using two engines and a
single scimitar shaped contra-ratoating propeller to achieve a
remarkable 577 mph.
http://www.luft46.com/dornier/dop252.html

With that speed it could have outperformed most jets.

All theoretical of course but there is no reason to doubt them. The
Germans did have the world biggest wind tunnel at the end of the war
located in Austria. It could test a full sized fighter at near full
speed.