A aviation & planes forum. AviationBanter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » AviationBanter forum » rec.aviation newsgroups » Military Aviation
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

Counter rotating propellers



 
 
Thread Tools Display Modes
  #11  
Old September 19th 04, 10:10 AM
Peter Twydell
external usenet poster
 
Posts: n/a
Default

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!
Ads
  #12  
Old September 19th 04, 10:51 AM
Cub Driver
external usenet poster
 
Posts: n/a
Default


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
  #13  
Old September 19th 04, 11:11 AM
ANDREW ROBERT BREEN
external usenet poster
 
Posts: n/a
Default

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)
  #14  
Old September 19th 04, 11:16 AM
ANDREW ROBERT BREEN
external usenet poster
 
Posts: n/a
Default

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."


  #15  
Old September 19th 04, 11:20 AM
ANDREW ROBERT BREEN
external usenet poster
 
Posts: n/a
Default

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)
  #16  
Old September 19th 04, 11:43 AM
Ken Duffey
external usenet poster
 
Posts: n/a
Default

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



  #17  
Old September 19th 04, 12:17 PM
M. J. Powell
external usenet poster
 
Posts: n/a
Default

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
  #18  
Old September 19th 04, 02:54 PM
Peter Twydell
external usenet poster
 
Posts: n/a
Default

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/rnh...es/ls326_6.jpg is the best I
can find at the moment.

--
Peter

Ying tong iddle-i po!
  #19  
Old September 19th 04, 03:01 PM
Kevin Brooks
external usenet poster
 
Posts: n/a
Default


"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





  #20  
Old September 19th 04, 09:01 PM
M. J. Powell
external usenet poster
 
Posts: n/a
Default

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/rnh...es/ls326_6.jpg is the best I
can find at the moment.


Lovely!

Mike
--
M.J.Powell
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Aero Composites Propellers Badwater Bill Home Built 26 June 18th 04 05:30 AM
FS Performance Propellers 60 x 66 Sammy Home Built 0 December 19th 03 02:51 AM
Performance Propellers 60 x 66 Sam Hoskins Home Built 0 December 10th 03 02:03 AM
Wooden Propellers Dick Petersen Home Built 5 November 13th 03 01:41 AM


All times are GMT +1. The time now is 03:32 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.
Copyright 2004-2018 AviationBanter.
The comments are property of their posters.