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Counter rotating propellers



 
 
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  #21  
Old September 19th 04, 11:01 PM
Ken Duffey
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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

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  #22  
Old September 20th 04, 04:00 AM
Kevin Brooks
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"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.

http://www.flug-revue.rotor.com/FRhe...11/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.

http://www.tupolev.ru/English/Show.a...onID=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



  #24  
Old September 20th 04, 06:13 AM
Eunometic
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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.
  #25  
Old September 21st 04, 05:59 AM
Eunometic
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Posts: n/a
Default

(Eunometic) wrote in message . com...
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.
 




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