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#21
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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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"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 |
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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. |
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