what is the purpose of having contra rotating propellers on an aircraft
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- čas přidán 31. 07. 2024
- Hello everyone, you are watching another episode of Military TV. In today’s session, we are going to discuss “what is the purpose of having contra-rotating propellers on an aircraft?” the detailed answer is only available at this channel, stay tune and watch this video till the end!
As we can see that some aircrafts are equipped with contra-rotating propellers. Contra-rotating propellers refers to an installation in which two propellers are attached to the same engine with one is installed immediately behind the other. It applies the maximum power of a single piston or turboprop engine to drive two coaxial propellers in contra-rotation (rotating in opposite direction around the same axis) and power is transferred from the engine via a planetary gear or spur gear transmission.
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Tupolev TU-95 is the finest example where the engine maximize its full potential and speed , only the downside is loud. Coaxial contra-rotating propeller are one of the greatest invention. Kudos !
Tu-95 flew over my apartment during victory day parade, I didn't see much diffefent from jet engine, maybe it's louder from higher ALT.
@@TheKaMeLRo it's louder when it's above 30000 feet
@@TheKaMeLRo maybe because it's on low speed, it's gonna be louder when it's on high speed cause the propeller gonna spin faster
there are more downsides than being loud. extra cost, complexity, weight and maintenance are a few that come to mind.
@@fujii_natsuooooo no, the propellers are constant speed and turn relative slowly (750rmp at full power)
You completely forgot to tell that two opposite propellers put one after the other make a hell lot of noise and that's why you have not seen them in civil aviation.
When I was in the RCAF over 30 years ago, the people who used to man the submarine listening post in the RCN said they could hear the TU-95 Bears out over the Atlantic through the hydrophones on the bottom of the ocean, they were so loud.
@@Chuck59ish Wow,
Remember that the application of the theoretical advantages of the contra-rotation was to reduce the speed of the tips of the propellers but it is not easy to harness the Kuznetsov NK-12 Turboprop engine that develops nominal 15,000 hp each. Apparently it is one of the loudest airplane and it is curious that the engine, very advanced for its time, was designed by a German team of ex-Junkers prisoner-engineers!
Don't forget about Aeroflot's legendary Tu-114 that was jointly used by Japan Air Lines.
@@Chuck59ish Yes the TU-95 Bears emit lots of low frequency noise on top of all the other noise they generate. I like to think it's possible and hear those planes through hydrophones in the ocean.
0:15 As a aircraft engineer for the last 23 years, I'm so glad I watched your channel as you're special and are the only ones that have this information otherwise I'd never have known. 🙄
Hehehe I thought that funny as well ;)
Yeah he got a dislike from me for that
Yeah, that was a bit of a dumb introduction
Let me do a quick search....aaaaaand nope, there's nowhere on the internet but here that gives the explanation.
Oh wait, nevermind, there are thousands of results
Sounded a bit like an Indian scammer! 😂
I knew there had to be a very good reason. My first intro to the contra-rotating prop was the Shackleton. Knowing the financial situation of the UK when it was developed I asked why. The responses were mixed and not consistent. This was the first explanation that made sense; a long time economic saving of all components of material, maintenance, and airframe.
If a plane swings to one side due to prop rotation, I believe that it is called Yaw not Pitch which is movement of the nose up or down.
I would expect a single prop to produce contra roll, and Cessna pilots can feel that at a small level. But as evidenced by the Sopwith Camel, it's the gyroscopic effect that gets you when you try to turn - causing either nose up or nose down. But unlike the Russian aircraft shown here, in WW1 aircraft the spinning mass (of rotary engine + propeller) is a significant fraction of the total mass!
Yaw is the change in the direction the aircraft faces (like from rudder inputs).
Pitch is nose up or down.
Roll is one wingtip moving downward while the opposite wingtip moves upward.
@@bobinthewest8559 precise! Good Bob!
@@bobinthewest8559 precise! Good Bob!
Great Catch @Mark Fryer! I might have missed him saying it wrong -> 1:11 because I wasn't paying close attention.
Bob in the West is correct about Yaw, Pitch and Rol.l
The problem with counter rotating propellers is the gear box. There are many harmonics of forces between the number of blades, cylinders and teeth on the gears. If one of the harmonics focus on the same teeth the gear box will fail for no obvious reason. That is why some aircraft have a rpm range where they should not operate in. It would be interesting to see maintenance records of these aircraft with counter rotating props.
Apparently this blade set-up has some performance advantages but increases the mechanical complexity as well. More things to go wrong IMO.
@@daveinstlouis lets use then WWI aircrafts they are simple and easy to repair ^^
Gearboxes are a challenge in aircraft engines, it can be noted that aside from the Rotax series there haven't been any successful reduction-gear general aviation engines, mostly for the problems you mention. Larger piston engines, including the Merlin series, used reduction gears, and turboprops universally do. There are challenges like you describe, but for the most part aside from GA aircraft they've been successfully dealt with. Turboprops, as well as not being possible without them, are probably easier to have reduction gears on as they don't have power pulses from cylinders firing, the torque is very steady, so the gears have less shock loading. So there's already a gearbox there regardless. Contra-rotating propellers add complexity to the gearbox, which in turn would add more opportunities for damaging harmonics, but I wouldn't think that insurmountable, and many ex-Soviet designs have been running reliably for decades with contra-rotating propellers. I think the main reasons they aren't more common is more the cost, weight, and complexity, and that most high-performance large aircraft that would benefit from them are these days powered by turbofans. Plus I think interaction between the front blades' wake and the rear blades makes them quite loud, louder than single propellers (which in turn are louder than turbofans). That's a problem both for passenger comfort in an airliner (hence why the "propfan" concept, which used contra-rotating props, never took off) and increasingly limiting noise requirements. Basically there's a very limited niche they'd occupy between simpler single-propeller turboprops and higher performance turbofans - it's not that they are hard to build or make reliable, it's just there isn't a huge market for them. They have limited things they're better at than other designs and several drawbacks compared with them. Sort of a "solution in search of a problem."
@@quillmaurer6563 i think you counter your own point
-"Some Russian aircraft have used them reliably"
- "One reason they're not used more is complexity"
Complexity is not an issue if it's reliable.
@@gormauslander There are negatives of complexity other than reliability. More expensive to design and manufacture, higher maintenance, more mechanical losses in the gearbox, and typically heavier. Also reliability is relative - an engine shutdown on a four-engine bomber isn't a huge deal typically, and when you look at some of the things the US used for a long time - such as the C-5 - you can see that in some contexts things that aren't very reliable are considered acceptable. So that the Ruskies have been using these for decades and have no intention of replacing them (much like the US with the B-52) doesn't mean it's reliable by civilian standards, enough to make it appealing for airliners. Case in point, Lockheed actually tried to sell a civilian version of the C-5 as a freighter and airliner, and sold exactly zero. (Were a bit more successful with the L-100, civilian C-130). But the reliability was adequate for the Soviets/Russians to use them for decades, and not have any strong desire to replace them within the next several decades. Complex designs can be made reliable with enough design and manufacturing effort, and making the parts tougher, but that means expensive and heavy, which might not be the most appealing option.
Thank you for post... great explanation of Contra Rotating Props. Very few downside issues; mostly added complexity of gearbox and a second prop. Downside issues are nothing compared to all the benefits gained.
The contra rotating propeller graphic at 0:13, is rotating in the reverse direction, for which it is drawn. The small darkened rectangles that start at the spinner and run about 2/3 along one edge of each propeller blade, are deicing boots. Atmospheric water condenses as ice into the leading edges of blades and wings, due to the momentary pressure differential caused by encountering that hard edge. Mechanically induced sleet, if you will.
The ice adds catastrophic weight and also interferes with functionality. The boots are flexible, sometimes heated and usually expanded with air pressure, to break the ice free. Deicing boots are *always* on the leading edge. Consequently, credibility within the first minute, is undermined.
Thank you for pointing this out. I too was skeptical of the whole video after I noticed this error. That gives it a thumbs down from me.
*"...the detailed answer is only available at this channel..."*
And yet, no hint of contra rotating systems that employ different fore and aft prop sizes and/or drive ratios. While they may not have been widely used, understanding the engineering considerations is enlightening.
To date only An-70 uses different propellers. And not in diameter but in number and possibly shape of blades. They'd also spin at possibly different rates. But you don't want different prop diameters.
It makes ot a lot quiter right?
We used to live near a Avro Shackleton base in England in the 1960s. The contra rotating propellers had a distinct sound. The airplane was basically a derivative of the famous WW2 Lancaster bomber and the 37 litre Griffon engines were later versions of the 27 litre Merlin engine.
I'll have to search for a video of that.
I heard the Merlin then the Griffon back to back in Spitfires (on CZcams only). I used to think that I preferred the sound of the Merlin until I heard that video.
We've got two Shackleton's dumped at Pafos airport here in Cyprus. Such a shame to see them deteriorate over the 20 years I've lived here. I'd love to own one or even just a Griffon!
Shackleton is a mongrel of a plane.... bits from all sorts
We have a Shack at Coventry airport that they are trying to get flying
God I feel old! I have actually flown in a Shackleton
South African Airforce used Shackletons up to 91. There was talk of them being retrofitted with Turboprops in the '80s.
Very interesting, I never thought about the rotating air, I always thought the first propeller increased the density of air for the second propeller and that was the reason. I learned something new today, thank you!
das Rollmoment wird ausgeglichen! Besonders wenn an einer Seite das Triebwerk ausfällt.
Muito interessante!
E, melhor ainda, é a narração que não é cansativa, e com ótima pronúncia!
When I hear it said that airflow makes the airplane “pitch” left or right, it makes me immediately suspicious of the knowledge of the writers generally,
Video showing the props turning the wrong direction in animations also makes me suspicious of what they know about what they are showing.
@@bkailua1224 Yeah I noticed that too. Annoying as hell to have a documentary that cant get it right
That’s weird... my head spins in the wrong direction also.
I guess the correct answer would be "roll" left or right
Don’t pitch about it 😝
In 1968 I was a passenger of flight Habana-Moscow performed by Tu-114 with same engines as Tu-95. Operation of Tu-114 in civil aviation ended in 1977.
What was the experience like? I heard those planes were very loud and shaky, but I don't know if it's actually true or just rumors.
That was non-stop? It must have been a loud and amazing experience.
@@amramjose You get used to it quickly, immediately lays your ears. As a child, every year I flew on vacation with my father, from Karaganda to Moscow (2000 km ). First on the Tu 114, then the Tu 134, and in the mid-80s on the Tu 154. The difference is almost imperceptible, only the Tu 154 flew faster ( 3 hours, instead of 4), and the cabin in the Tu 114 was very narrow. I really liked to look through the porthole , as one by one , the Tu 114 engines are slowly starting up !
@@alte9751 I've watched documentaries about the TU-114, apparently the noise and vibrations from the NK-12 engines were particularly noticeable in the wing section of the aircraft. It's worth noting the TU-114 had a very successful career with Aeroflot; there was only one accident resulting in loss of life, and they were in service into the late 1970s.
The noise is something I'd be interested in knowing about on the Tu-114. That's one of the big limitations of the contra-rotating engine design for modern contexts, rear blades passing through the front blades makes a lot of noise. Louder than single propellers, which in turn are louder than turbofans. That would pretty much preclude their use on civilian aircraft, both for passenger comfort and noise restrictions at airports. This to my understanding is why experiments by Boeing and McDonnell-Douglas to put propfans on the 727 and MD-80 were abandoned, while it showed promise on efficiency it was unacceptably loud.
A pretty good overview, but with some omissions, the odd error and one absolute howler (which is quite appalling in mid 2022, to be honest). Other British aircraft that used contra props include late marks of Supermarine Spitfire, as well as their Seafang and Seagull, Westland Wyvern, Blackburn B.44 and B.54, Bristol Brabazon, Martin Baker MB.5, and the Saunders Roe Princess. There were also quite a lot of US designs, but none made it into production. Aircraft do not "pitch" left or right - they yaw. Pitch is in the vertical plain, not lateral. The increased efficiency is not "additionally" to the decrease in lateral flow, it's the result of it. "Mk.101" is the engine MARK, not "M K". And now the unforgivable... Antonov is a Ukrainian company, not Russian. Their main facility has been severely damaged by Russian forces in the current war.
About Antonov is more complicated. It is Russian company (branch from Yakovlev), during Soviet times it was moved from Siberia to Ukraine to increase industrial level of that territories. After dissolve of USSR, company de facto died, most of engineers returned back to Russia, so it mainly tried to finish soviet projects (but even failed to finish almost ready second AN-225, largest in world aircraft) and repaired old aircrafts. It continued until last rare soviet engineers not became too old and just gone. The company hasn't produced any plane in almost 10 years.
P.S.
About damaged (destroyed) facility. Several years ago Ukraine declared decommunization program (renamed thousands cities and streets, remove monuments, burn books and so on), so now in Russia exist joke: “we help to you with decommunization, everything what built communists, will be destroyed”.
@@juliap.5375 Nobody trust any more to Russian propaganda
* Pitch is in the vertical plane, not lateral.
Antonov was a Russian company. A lot of other companies were moved/created in Ukraine during the "great industrialization" project.
@@juliap.5375 Зачётная шутка про декоммунизацию! 👍 Товарисч Юля! 😀
I remember reading about a test pilot flying a prototype Spitfire with a Griffon engine and contra-rotating propellors. The drive system failed while he was flying and he had to land the aircraft at a nearby airbase with the engine at full throttle
The IJN used the contras on their Type 97 Long Lance torpedoes during WWII. This stabilized the 30 foot long weapon on its way to the target, making it the most deadly and accurate torpedo at the time.
subs are the future of defense,space technology is not yet
this has me wondering, what is the efficiency of a contra rotating prop compared to a geared ultra high bypass ratio turbofan, as the stators behind the fan seem to serve a similar purpose with less mechanical complexity.
No, it's not similar. The bypass fan is used for cooling the engine and turbine intake air, the later resulting in a better fuel/air mixture and additional (albeit minimal) cooling of the exhaust components.
The contra rotating is to make more efficient use of disk area and to straighten the airflow over the leading edge of the wing.
(Retired A&P)
@@deafmusician2 You are confusing bypass air (fan air) with the boundary cooling air flow in the engine. The fan air exits the fan air duct as pure thrust. That flow is higher density than the hot thrust. Remember MASS airflow is the thrust we are looking for. TW 670828
@@jayreiter268 Actually impuls is the thrust we are looking for.
@@rizzochuenringe669 I do not understand your comment. Naturally the inlet diameter is going to be larger.. The principles of mass airflow are if you want to double the thrust you can double the mass at constant velocity. You can also double the thrust by doubling the velocity of the mass. Thrust=Mass x Velocity squared. So in the first case it takes twice the energy to double thrust. In the second case it takes four times the energy (fuel). This has the same effect in wing span and disk size in helicopters. Do not feel bad if you do not get it the first time. Took me 20 years in the business to realize I could work the formulas and pass the tests but did not fully grasp the basic principal.
@@jayreiter268 No, thrust is mass per second times velocity
In SI-units: [kg/s*m/s]
This is the dimension of a Force F (and the definition of 1 Newton)
Google Newton (unit).
I've never even noticed these types of engines and propellers. Very informative.
The visual effect of the spinning propellers evokes strong emotions in me.
Some multi-engined propeller driven aircraft have engines that are "handed" in that the engines rotate in opposing directions on each side as an alternate method of removing the torque induced yaw of powerful piston engines.
Obviously not possible on a single engine aircraft such as the Supermarine Seafire or the Fairey Gannet where a contra rotating configuration is required. Unlike the Seafire the Fairey Gannet used a twin engine single shaft design so that it could loiter on one engine in its patrol area.
The De Havilland Mosquito used two 'handed' Merlin engines for that reason.
This is the same reason turbofan engines have stator blades in the fan duct. Without them a portion of the fan's power production would be lost to "swirl energy". The stator blades reduce the swirl and straighten out the airflow, which increases the efficiency of the fan.
Well explained!
Yea the 2nd prop has something to get its teeth into.
In theory you are correct, but in practice, not. with electric powered aircraft where energy management is even more critical than in fossil fuel powered aircraft, and a set of contra-rotating propellers would require no gearbox, just two electric motors one with a hollow shaft, that they are in common use speaks volumes.
@@johndavidwolf4239 My post doesn't say anything about what you are talking about. I never even mentioned anything about counter rotating propellers. I was talking about turbofan jet engines and nothing else.
@@johndavidwolf4239 I'm with you about theory/practice stator/contra - Likening them to stators is a simplification as compressor stages are built within a housing not open air, but more so the leading edge of the next compressor blades are biting "stator" air "w/o" rotational energy ("quoted" because imprecise) and contra #2 blades bite rotating air.
Thank You!!! Finally someone explained that to me! I'd Love to hear the sound it puts out.
I always liked this concept.
Did they ever try contra rotating props inside a fan duct?
Did they ever try this concept in the compressor side of a jet engine? You know, contra rotating impellors. I guess that would make it much more complex.
no: in a ducted prop or turbine is the reaction prop row static, doest need contrarotative props to achieve same efficiency
In all of your illustrations, you had the propellers spinning backward. The deicing boot is always on the leading edge of the prop, not the trailing edge. In the videos sometimes it appears to be on the back because the frame rate makes it look as if the prop is spinning backward.
There is, or was 15 years ago, an old aircraft hanging from the ceiling of the concourse at Minneapolis-St. Paul Airport that has its propeller fitted back to front.
The video leaves more questions unanswered than it answered.
Too true. Like for example if they're so good why aren't / weren't they employed on say, WWII fighters for example? Very simplistic and unclear vid!
Wow I'm lucky to have found the only source that explains this. Lucky me...
Many thanks fo bringing the clues to the puzzling idea of having two propellers rotating in opposite directions on a single engi shaft. May be the Kamov helicopters using the similar approach could have been also included. Best regards. Paul, 68, fan of aviation
First of all: it looks cool. And I understand it's a way to get more blade area instead of larger propeller diameter or more blades on the same propeller.
But I actually did not know it's more efficient than one propeller!
An uncommon and interesting aeronautical subject that I was aware of, but didn't know much about. Thanks for presenting it. A good presentation except... I hope that the producer will find my observation constructive. The voice dialog is excellent until the script uses "aircrafts" to indicate the plural. There is only one form of the word for describing both a single aircraft and multiple aircraft. The only time an "s" is added is with an apostrophe preceding it to indicate the possessive form.
I agree. Aircraft can be singular or plural, depending on the context of the statement.
This error is becoming more commonplace as education declines in America.
Speak English you child
@@Seregtir ...
It’s beyond “commonplace”, moving into the realm of “pervasive”.
A lack of knowledge of proper/correct word forms, horrific misspelling, use of the wrong words for the context, and use of “non words” (such as the rise in usage of “eggspecially”)... are all signs that the majority of our population is inadequately educated... and they don’t even care.
It’s just one of the “less dramatic” indicators that our society is rotting from the inside out (in my opinion).
You are most welcome🙏🏻🥰
Was a pilot in the Navy on aircraft carriers in the pacific. We were monitored and flown over by bears. Amazing aircraft still in service today.
Technically not Bears, but the naval version.
I served on Ranger for a while (CV-61 not CV-4).
Have you any idea what altitude they would've been flying at? They probably appeared small from sea level.
@@kiwitrainguy 500 feet OR LESS on one of the flyovers.
Perhaps 1000 the other one.
They did NOT appear small.
Both times they had an "escort" sitting right under each wing - I think it was a pair of Phantoms one time, a Tomcat and a Phantom the other time - and I could hardly hear those LOUD jet fighters for the noise from the Bear.
Thanks for replying. OH MY GOD they were out to intimidate you guys (as if you couldn't work that one out😆). I thought they must have just been observing from about 40,000 ft or something. I wouldn't mind getting a close up look at one them in flight like that, just remind me to bring my earmuffs.😛@@bricefleckenstein9666
@@kiwitrainguy occasionally they would do a low pass over the ship. Great to see. Normally they fly around 20,000 feet.
Este video está muy bien producido, gracias por compartir sus conocimientos.
I would've been nice to see the cost of maintenance increase. I suspect it is more than the 6 to 16% increase efficiency. And yes, i know you cant compare the percentages directly until you get the numbers and units the percentages are based off.
They do something similar with helicopters but in that field it is not popular either.
I have and still am amazed by the Tu-95 Bear.
Why ?
@@pauleyplay why not?
I think the reason why the engines are more efficient is because the contra rotating blades create a low pressure zone in front of the wings even at slow speed, which helps drive the airplane forward. Same with counter rotating blade helicopters.
Knew it 30 years ago! Isn’t the “ONLY” place to see this kind of info!!!
A hélice contra rotativa torna a aeronave equilíbrada com efeito rotativo reverso que neutraliza o sentido da rotação e permite um empuxo mais forte com maior economia de combustíveil na baixa velocidade de cruzeiro e na retomada uma velocidade maior que o mono hélice o próprio exemplo e' o TU 95 que atinge velocidade próxima a 1000 Km/h.
Exactly.... I couldn't say I better 😂
The most famous use of contrarotating propellers is on the Tu-95 "Bear" bombers. Soviet designers chose this solution to ensure that a lifetime later people on CZcams could enjoy its amazing soundtrack.
I think that Ferdinand Brandner chose the solution.
I would really be interested to know how that aircraft stalls, especially in a power on stall. Not sure, but maybe the reduced torque will not make that plane roll so fast in a stall like single prop aircraft do.
THAT'S A VERY GOOD QUESTION!
THAT''S THE QUESTION I WAS ASKING MYSELF FOR YEAR
FINALLY AN ANSWER!
FOR THE PURPOSE OF HAVING A CONTRA ROTATING PROPELLERS ON AN AIRCRAFT
That is only part of the reason and is not really as significant as you might think. The additional loss of efficiency by adding the differential gearbox eats up most of the gains. In addition, it adds weight and a major failure mode that has caused them to be shunned for most applications. The big gain is in reducing the number of blades and the blade diameter needed to utilize all of the engine power once we started making engines over 2000 HP. This means that you can have a much lower fuselage. That is great if you are making a cargo aircraft, lower is easier to load and unload, and makes for shorter stronger landing gear. The failure of the gearbox has been a real problem over the history, and the maintenance required to make them reliable pretty much limits them to military usage. Once we developed high bypass turbo-fans they became even more limited in value. There has been a slight increase in usage with the advent of advanced propeller design (curved blades), but the noise they generate is still a major problem. We used them in the B-36 and they were a constant source of problems. A former B-36 pilot i knew said the when you said that when you lost an inboard engine gearbox, the plane shook so hard that you could not read any of the gauges on the plane to see which engine failed, one of the rear gunners would have to jam his head into the gun blister to see which engine and call it over the intercom. The Russians needed the 6% increase in efficiency to get the range for their bombers, the U.S. developed and perfected in-flight-refueling instead.
First applications on the Spitfire family, mainly the Seafire, was to make the propeller smaller to avoid hitting the deck on landing, and adverse factors as torque, p-factor and helicoidal movement of the propeller slipstream. On multi-engine aircraft like the Shackleton, the idea was to have the smaller propeller disk as possible to kept the engines as close as possible to the wider fuselage with the shortest possible landing gear. On high power Tu-95 or An-22 having eight engines nacelles and propellers was not practical at all.
Tu-95 must have 8 propellers, because engines so powerful and 4 propellest should be bigger than 10 meteer diameter to transfer all power, additional propeller decrease diameter of all proppelers
@@Spectre4490 You are right the Kuznetsov NK-12 lists at 15000hp and 5400lb per hour fuel burn at takeoff. That is up there with the J57.
@@Spectre4490 the props are 6meters in each blade. Whereas the An22 was more than that, probably 8 meter blades
@@Spectre4490
そう、プロペラ径を小さくするためでしょう。
V−22でも二重反転プロペラに出来れば、ペラ径は7割程度(直径13mから10m弱)に出来る、
しかし、機械部分の重さ・故障率は倍増するのでは。
Just two words for you: Dornier 335!
A wonderful channel that deserves all respect, appreciation and pride. Accurate and useful information in a sophisticated and beautiful manner. I wish you lasting success. I have the utmost respect and admiration for your great honor for these wonderful works. I hope you success
Very good video indeed. I wish there was a video going into detail how the two props are attached to the shaft and how they can counter rotate with only one shaft.
Pues debe tener ,como la toma de fuerza de un tractor, sale un eje ,y también un caño ,los dos con la misma resistencia ,todo apoyado en boliyeros ,uno dentro del otro ,afuera cada uno con su hélice ,adentro cada uno con su engranaje satélite
There’s two shafts. One inside the other. They spin opposite directions.
@@stevenbeach748 exacto, pero el que va x afuera es como un caño o tuvo ,luego mas afuera esta el soporte de todo que podría desirce otro caño mas grande ,que es el sostén de todo
,en el caso de los tractores ,el primero es la directa ,el segundo es la toma ( que se nombra,toma de fuerza) y el tercero es la propia caja de cambios ,que unen la caja con los hembrayes ( son dos e independientes) ( la toma de fuerza es ,x ejemplo ,la que se usa para a ser dar vuelta una desmalezadora con transmisión a toma de fuerza) y cortar el césped en lugares como parques ,vanquinas
@@stevenbeach748 Really?! Wow!
I would've liked to have seen more of the technical side, i.e. how they are driven, how the contra-rotation affects gearbox stress etc.
Then go look it up. Google is your friend
Yes I agree with you that the technology would be interesting
One other reason not mentioned in the video was that only with contra rotating props could the power of the Kuznetzov NK-12 engine be used on the Tu-95 for which this engine was developed.
A single prop handling 12,000hp would be simply to large to fit on the wing of the Tu-95 due to the wing sweep, the engine nacelles then had to be lengthened forward even more than now already the case, and the landing gear would need to keep the plane even higher off the ground.
Also a single propeller of huge size couldn't be made stiff enough with materials then available, it would be more of a helicopter rotor mounted horizontally with blades flapping about.
Then why not use jet engines?
@@bowez9 tu-95 is a turboprop aircraft, that is a gas turbine driving a propellor. This was back in 1952 when jet engines were horribly inefficient (they still were 3 years later when the B-52 came out.) Back then there were no ICBM's and efficiency was very important in order to be able to fly from the Soviet Union to the USA, drop a nuke and get back without the need for refueling (compare the American B-36 bomber from 1946 designed for the same purpose, the only plane which ran piston engines and jet engines at the same time.) One reason it's so loud is that the blade tips exceed the speed of sound. Yes, they could have put all 8 blades on the same shaft, quadrupled the number to 64 (that would then get the tips below the speed of sound) and put a duct around it, essentially making a modern turbofan. Maybe that didn't occur to them, or maybe they preferred propellors because they can be feathered for a wide range of speeds and conditions.
@@londonalicante so it's an outdated application?
@@londonalicante not quite....The first mid-air refueling tankers, the KB-50s would run on both piston and jet engines. They needed to do so as the full power in a low angle dive airspeed was just barely above the stalling speed of the first generation of jet fighters. Even with the extra power provided by the jets, the fighters still struggled to stay above stall speed as the fuel was transferred and that aircraft became heavier. This is ultimately why the KC-135 was developed--to bring jet speeds to mid-air refueling.
Its amazing what I can learn from the comment section in a video. Thanks guys!
I'm not enough of an aerodynamics engineer to understand all of that. But as the former owner of an old canvas wing single engine, that's an interesting concept!
Don't forget about the Tu-114 Airliner. It was used jointly by Aeroflot and Japan Air Lines.
Yes but only for two years after which the collaboration ended.
Спасибо за ликбез, всегда задавался этим вопросом, теперь стало понятно. У Ту-95 очень сильный психологический звук от этих винтов, когда служил пролетал над нами, просто становится не по себе.
Я не знаю английский. Но по твоим словам, это для того чтоб меньшешума было?
@@Muzaffar_nv нет, для снижения потерь энергии на вращение винтов без увеличения их диаметра - там типа поток воздуха не завихряется, а сразу идёт "назад".
@@user-rt1hr4fd2y благодарю за ответ
@@user-rt1hr4fd2y дилетантский тут ликбез. Не надо быть великим физиком, чтобы догадаться что: 1. повышенный шум винтов както не вяжется со снижением потерь энергии. 2. Встреча вихря за первым винтом с лопастями второго винта со сложением скоростей это повышенное трение и затраты энергии на обратное завихрение. Выигрыш там лишь в "ровном", а не закрученном потоке воздуха за винтами, но это не так существенно - основное торможение создает вихрь, образующийся по периметру потока от винта, так что с энергоэффективностью мимо. Да и когда это воякам так сильно энергоэффективность требовалась?
Смысл сдвоенного на общей оси винта - скорость. Первый винт разгружается вторым и наоборот, что позволяет вращать их с большей частотой и пропускать больше воздушного протока. И потому скорость у Ту-95 существенно выше чем у большинства турбовинтовых самолетов.
@@Muzaffar_nv включи русские субтитры и читай)))
What you explained at the beginning of the video is only one of three turning tendencies! The one in the video is called the Spiraling Slipstream, which causes a *yaw* (not pitch) to the left or right depending on rotational direction.
The next one is called P-Factor, which has its greatest effect at lower airspeeds. At low airspeeds, the wing needs to have a higher angle to the relative wind to keep the airplane up. This causes the air entering the propeller to come from slightly underneath, so the side of the propeller going down has a higher angle to the oncoming air and makes more thrust than the side going up, again causing yaw to the left or right (same direction as Spiraling Slipstream).
The last one is Newton's Third Law of Motion. The airplane is pushing the propeller around through the air, so the propeller applies an equal and opposite force to the airplane, causing a roll in the same direction as the yaw.
i have a question, if i were to take this design and have four propellers instead of two, where 1 and 3 spin right and 2 and 4 spin left, would I generate more thrust?
first full controlable helicopters (1933 Breguet Dorand gyroplane laboratoire) had same counter rotative propellers
Always wondering why the Russian Tupolev Tu95 Bear Bombers spotted with these ContraPropellers >>> Now we know they're for Rebalancing the Rotational Torque & Smoothing out the Airflow with a 6% to 16% more Efficiency of Flight! Thank You for the interesting tutorial! 🕯
The wright brothers would be so surprised to see that their concept of flight has been so much improved
Thank you for answering a question I have wondered since I was a kid!!!
Subscribed!
"The detailed answer is only available at this channel."
Pretty sure it's not.
minimally useful video. Why didn't you go into the obvious question as to why nobody else went with this propeller design.
more gears and propeller means more maintenance cost... is about which powerplant(engine) designs has lower total operating cost...
This is just my hypothesis before watching the video; I would assume that it helps with the extra rotational force you get when you have a normal single prop. Similar to the use of the two propellers on an RC helicopter.
Not mentioned here is the matter of propellor blade pitch. I assumed that the blades of each propeller have opposite pitch, so both produce forward thrust while rotating in opposite directions.
Один раз в жизни я увидел Ту-95 вживую, но я сразу понял, что это Он!) Лет 10 назад я услышал этого "Медведя", подняв голову я увидел высоко-высоко в небе самолёт с необычно очень длинными и тонкими крыльями, и этот звук... действительно "Медведь"))) Я сам с Поволжья и подобные звери у нас не базируются, видимо это была перегонка своим ходом.
Вообще-то основное место их базирования - авиабаза Энгельс, на другом берегу Волги от Саратова. Так что как раз Поволжье для Ту-95 - дом родной.
Был в командировке в Саратове и поздно вечером услышал этот гул - ощущения непередаваемые!
@@mikesar1306 Спасибо, не знал. Я живу почти на берегу Горьковского водохранилища, 600 км до Энгельса. Сейчас на Яндекс Карты глянул и сразу же нашёл! 16 штук) И "Лебеди" тут же стоят)
@@Sergebearded Не за что! Вот, теперь будете знать. Рад, что смог сообщить что то интересное.
@@mikesar1306 болтун находка для шпиона
@@z72922 да это какбэ уже лет 30 как не секретные сведения
Why no word about suppression of nacelle/engine whirling by counter rotating props? Aero-elastic stability is certainly a major consideration for any aircraft with such large nacelle projections.
I'll say one thing!! It looks cool as hell!!!! The old RR Griffin was a V12 with counter rotating props!
There have been at least 2 P51 Mustangs with Griffon Engines using Contra Rotating Propellers that raced in the Unlimited Class Reno Air Races. Precious Metal and Miss Ashley.
General Electric (I believe K. O. Johnson at GE Aviation) looked into a counter rotating jet engine that they called the "un-ducted fan" engine. The relatively short propellers looked like boomerangs. It is my, very limited, understanding that in this engine there would be no stationary blades (or buckets), but counterrotating turbine blades (buckets) on two concentric shafts (inner and outer). As you mentioned, efficiency was (greatly?) improved, but noise was WAY up. As far as I know, it was never brought into commercial service......
An MD80 aircraft with one of the two jet engines replaced by the prototype "unducted fan" was flown at the Farnborough Air Show in about 1990. It was not objectionably noisy but the sound was very different. It was remarkably similar to the sound of the Yamaha RD/RZ 250 and 350 motorcycles of the 1980s. There are some video clips of this aircraft but you don't get to hear the engine properly because the videos have been dubbed with the sound of a commentator talking about the engine. The "unducted fan" was abandoned in the early 1990s because a fall in the price of fuel made its higher efficiency less attractive.
It was/is known as the Propfan.@@cedriclynch
I wonder to what extent the efficiency difference is actually that big. Even in the worst case provided here, 6% (so let alone a huge 16%) would be so significant in today's efficiency pursue that all the use woudl be the norm rather than the exception.
If the efficiency is only aerodynamic but it brings higher production and maintenance cost, such efficiency is simply gone.
On the other hand, I don't think you get a clean and straight airflow just by countering the rotation of the front propeller. The rear propeller faces a drastically higher angle of attack than the front one, and probably different depending on the speed, so you'd probably need the rear propeller governor to have a different pitch at all stages, complicating the engineering quite a bit.
For multi-engine it's quite easier to have the engines in opposite directions.
The schematics shown on the video suggest the two opposing rotors are connected with a differential, so maybe the difference in airspeed would be taken care by it. But I'm also very sceptical about the efficiency due to turbulent air hitting the second fan. can it actually produce significant thrust or does it only clear out the rotation in the air leaving the propeller.
Uma aula maravilhosa
wish they would produce these for single engine GA or LSA aircraft . Seems like there are a lot of advantages .. no right rudder yaw required . A well behaved air stream , more thrust , improved rate of climb and improved fuel efficiency . In fact I heard the TU-95 has a very high acceleration
I appreciate the efficiency gain advantage but the handling difficulties of single propellers only apply to single engined aircraft. This is the main reason they were used for the later, most powerful, piston-engined carrier aircraft, because the torque effects were so problematic with both acceleration for take off and for landing on a moving deck. Multi engined aircraft can have left and right-handed engines to balance this out.
Might be useful for a multi-engine airplane to improve handling if an engine fails. I’m guessing a lot less drag due to not having to use more rudder to fly straight.
Can be, but often aren't. AFAIK, counter-rotating engines in multi-engine propeller aircraft are still rare for the sake of maintenance and inventory simplicity.
@Charles Lyster - "Multi engined aircraft can have left and right-handed engines to balance this out."
They can do - but the only aircraft I'm aware of which had this feature was the De Havilland Mosquito. Other multi-engined aircraft have all engines rotating the same way - my guess is to simplify manufacture, and stocking of spares.
It was commonly noted that heavy bombers in WWII could be a b1itch to hold straight when starting a take-off - in some case the flight manuals telling pilots to only open the throttles for the engines on one side until the aircraft picked up enough speed for the rudder to become effective enough that the pilot could use it to hold the aircraft straight. Opening all four from a standstill could lead to a vicious ground-loop which, in a bomber with full fuel tanks and a full bomb load, could be an absolute disaster.
@@jackx4311 I was always told it was the other way around... Most PROPELLER driven multi-engine aircraft, military or otherwise went with left and right handed engines, and the Mosquito was one of the rarities that didn't... It was suspected of being further useless (since it was also the last wooden framed military aircraft to hit production) BUT it proved quite the opposite, give or take the take-off procedure, which wasn't as troublesome (apparently) as originally expected either...
The BIG benefit to the corporates in Aviation today with Jets is that you CAN have all the engines rotating the same direction to save entirely on engine parts inventory... not that it makes a huge difference anymore, since most aircraft are actually financed more as a "subscription service" than an airplane product... BUT that's a subject better explained by Mentour Now or Mentour Pilot... Petter, either way (channels on YT)...
One OUTSTANDING example of torque issues with a single engine and single propeller is the Sopwith Camel of the infamy in WWI, that it killed more pilots in training than got shot down in war... BUT there are still quite a few videos of the troublesome little bastards in more recent air-shows and the like struggling to get around on the ground and that archetypal Sopwith Camel sound from the funky ignition RPM control... which was another in the many wonky factors that made it dubious at the best of times...
BUT on the tech-spec's note, the Sopwith was one of the earliest radial engines, and they decided (from what I've been able to glean to date) to rotate the engine block on a static shaft, to increase the torque output and drive the prop... a great innovation at the time, but the result is a little, lightweight plane that physically twists with the accelerating engine, even to the point of lifting a main landing gear off the ground if you're not delicate with her... They had a FRIGHTFUL habit of rolling and yawing hard to the left (if I recall correctly) and were damn nearly impossible to turn right until you "decelerated" the engine...
Granted, NOT everything is 100% from exactly the advantages gained in contra-rotating prop's on a single shaft/hub... BUT it's a solid visual of the many troubles one can encounter with a big powerful engine rotating a single "big" prop'... and all the torque and losses that accompany such a thing...
AND it's always fun to see why some would say, "If you can fly a Sopwith Camel, you can fly anything." ;o)
@@jackx4311 Incorrect, the Mosquito DIDN'T have contra rotating propellers.
It may be somewhat picky. But Antonov is a Ukrainian company. Not Russian. I as unaware that the AN-70 was in production.
Development started back in 1978(USSR), first prototype production kicked in in 1991(USSR), first flight in December 1994(Ukraine).
~90% parts are supposed to be produced in Russia, including those fancy fans. Also, ~50% of the intellectual property of the design belongs to Russian companies.
So, you can guess yourself how Ukrainian AN-70 really is. As well as what will happen to programme itself since in 2014 Ukraine terminated it's military cooperation with Russia. Right before joint tests phase was completed. And in 2015 Russian Ministry of Defense refused to order AN-70s.
@@IaHulg is now 2022, and none of the details in this aircraft are manufactured in Russia
@@user-vv5hj1zr2v let me guess, that's because the plane's production itself was terminated ... forever basically ?
Same being said to Antonov company as a whole. How many planes have they produced, say, last 5 years ?
Formerly an aircraft design company whose main income nowadays comes from cargo services.
You should have put in moving animation showing airflow ( aerodynamic movement) in a contra rotating propeller vs a single propeller. That would have made things clearer.
It would have been nice if the video had addressed the two obvious unanswered questions: 1) what are the disadvantages, and 2) why don't more manufacturers use this design?
This is most interesting. I've long wondered this myself. But I was hoping he'd address the noise aspect.
The Tu-95 is legendary for being a very loud aircraft but I've not heard the same thing said about other planes with similar setups. Is the Bear's noise fully the result of its propeller configuration, partly so or is it something else entirely.
Thats why its huge propelers rotating with supersonic speed.
I believe the tu95 is the fastest ever propeller aircraft and loudest.
Its not the contra props, its the fact that the props tips are supersonic. Basically 32 sonic booms happening at the same time, all the time.
@@keithw4920 so loud it can damage your hearing permanently!
@@finlaymcdiarmid5832 WHAT??! I CANT HEAR YOU!
Toda mi vida he admirado dos cosas del Tu-95: su longevidad y la enorme potencia de sus motores, pero desconocía el porqué de las hélices contrarrotatorias, ¡¡gracias por el dato!!
A los rusos les importa un pedo el ruido de las hélices
Another Downside is the Insane Noise such engines can produce; Jet Fighter pilots can hear a Tu-95 Bear inside their planes and even the old hydrophones of the SOSUS line at the bottom of the Atlantic can hear one passing overhead.
I remember well the Gannet with Double Mamba engines and the Shackleton with the Griffon engines. Great planes in their time.
The P 38 had two propellers on each wings. The propellars turned in the same direction, which tended to flip the plane over in flight. They made one propeller turn in the direction, which soved the problem. P 38 was a beautiful aircraft.
...waitwhat? None of this makes sense. The P-38 had props that turned opposite of one another, # 1 turned CW, #2 turned CCW, to minimize uneven prop turbulence on the vert/horiz stabilizers that caused twitchy handling. The aircraft's design made it sensitive to turbulence over the rear air surfaces, which is why it was important to Not have the cockpit windows down during flight.
The only P-38 Lightning that did not have counter rotating propellors and engines was the version the British ordered, against the advice of Lockheed, and then refused to accept.
All other P-38's, from the very beginning, had counter rotating propellors and engines.
BTW there has already been an airliner with counter rotating props, it was from Russia and I think was just the airliner version of the “Nuclear-Bear”, even for poor Soviet citizens it was… unBEARably loud (see what I did there? 😉). They said passengers and the crew had to resort to passing little notes because they couldn’t hear each other. Those counter rotating blades were supersonic at the tips and crews that flew these planes including the crews on the “nuclear-bear” retired deaf or nearly deaf…
yes! it was the TU-114, beeing the fastest propeller driven airliner to date! tho with the downside of beeing extremely loud with heavy vibrations because of the engines!
Здравствуйте! Мне повезло знать одного такого пилота лично и всё у него прекрасно и зрение и слух , а вот супруга от онкологии умерла! И я его допекал расспросами, про медведя, но я не припомню, того чтобы он говорил что-то про шум,!
@@user-zk7rt7st2y He must have worn ear protection I think (hopefully they ALL do now)! But I did hear about passengers having to pass notes in the Tu-114 airliner.. Thank You for sharing your story! 🇺🇸 ❤️ 🇷🇺
😎
@@frankthespank I think it 's something like a beautiful story or a joke . My parents flew theTu144 in the past , and they don 't have such serious memories . It was a long time ago . It was probably noisy, but not that loud. Otherwise they would have told me . Well , in any case , they should have remembered if their ears hurt so much . . Although my mom has vision problems . Maybe it causes myopia, not hearing problems? Some strange magnetic fields from the propellers affecting vision?)
@@user-tf4lh8oq8u Our parents were quite a different breed than us but especially yours that lived during Soviet times! Our parents didn’t complain about things as much but again… especially your parents in their generation during Soviet times. But at the same time here in in the west some stories about the Soviet Union were overblown. I’m just going by what reports I’ve read and documentaries I’ve watched about riding in those planes but you have parents that were actually there which kinda holds more water than “what I’ve read” or watched, lol
Thanks for giving your parents experience, I think that’s awesome they actually rode in a Tu144! I read about history that they lived!
Interesting... I have to wonder how efficient this setup could be with toroidal propellers?
@1:52 they have a negligible effect on the torque of the engine. It is the torque of the other propeller that that is matched and countered.
The overall torque of the engines is countered by having engines rotate in opposite direction from those on the other side.
Almost all large turboprops have engines that turn the same way. Only a handful of smaller piston powered twins have counter rotating engines.
hey! 2:12 A2D1 is there! USA mass produced these too!
edit: oh wait, a2d1 is not mass produced vehicle..
Great. But an obvious question went unanswered: if the design is so great, why is it so relatively uncommon?
I would guess that the complexity of the design makes it more economically feasible for larger aircraft, the types of craft for which the jet engine replaced propeller technology altogether.
Hmm, Cessna 152 with contraprop?
Because the actual goal of contra-rotating props is not exactly what he said. The goal is to absorb engine power efficiently without increasing prop diameter. Most engine-prop combinations design this problem out at the onset, because contra-rotating props are extremely complex, heavy, and require lots of maintenance. There are better solutions, (reduction gearing, more blades, modifying blade planform, etc.) than contra-rotating props.
This is the first time I've ever seen this. I missed this somehow but I like this video
To offset torque in 1 direction keep things balanced. On helicopters it prevents retreating edge stall
Ya, but you forgot to mention that they are loud as hell!! Bugatti once designed a plane in the 30s that did the opposite; 2 engines 1 propeller system. It was one of the fastest prop planes ever built! to this day!! I think it was called the "P-100"
Do a search here on YT on a home built Bugatti 100-P ... sadly it was destroyed on a crash in 2016
Once again it relies on the experience of the pilot, but the narrator is absolutely right.
Contra rotation stabilize flight. (It stays on course)
Il-2 (Flight Sim) had Spitfire (Mod) with the contra prop, it was Jet Fast. I think the Fury (3rd Gen Sea Tempest) also has a Version with it.
0:34 That is a Major Gear, I can see why they did not employ it more during ww2, the weight of it and the armour to protect it from that one lucky hit were too much risk for a few MPH faster.
Did no one try having two engines running separate props on the same shaft line, (one inside the other). The he177 had two separate engines running one prop, I don't know how they did that except to make a Xcylinder engine into a XXcylinder engine.
Thanks for this great video. I only missed Airbus Atlas from it as of the latest and most advanced example of this technology
This video mentions the advantages of contra-rotating propellers, but not the disadvantages. The reason more countries do not use them is because a) they increase the weight of the engine assembly, b) they increase the complexity of the engine assembly which means there is more to go wrong, and c) they are loud as all heck. So loud that they cannot be used anywhere noise matters, such as civilian airports and aircraft. That's why when you see them used, it's almost always on military aircraft.
And they look Goofy 😅 where is Torque in this POS?
Best advantage: cool AF.
You Said It! My Favorite example is the Tu-114 jointly used by Japan Air Lines and Aeroflot.
Douglas A2D Skyshark ❤️ My personal favorite aircraft has this configuration. So unfortunately it was not mass produced.
Greetings of great admiration and greater respect. Your wonderful and esteemed channel for the wonderful and accurate information you provide. I wish you good luck and lasting success. Sincere respect, appreciation and pride for all your great efforts and all your wonderful work. A very beautiful and accurate way to raise topics.
There is also a reason why American aircraft never used it in a major use….. complicated mechanics, loud, heavy maintenance, and old technology….
COntra-rotating rotors aren't "old technology".
MQ-25 Stingray: A New American $155 Million Drone czcams.com/video/4VJA2R0Xp7Q/video.html
The project began in 1978, the aircraft is more owned by the Soviet Union. And the Antonov plant has already been destroyed.
У вас декомунизация🤦....
Это советский (русский) самолёт...
@@alexwoods2836 , the plant operates and produces new aircraft.
Putinoid lies in any language.
Where is the AN-70 now?
@@alexandrdolgy How many planes has the factory produced over the past ten years? What aircraft models does the plant produce? Which countries are the products delivered to?
Peut-on penser au même principe pour les bateaux?
Would it also reduce the vibration and aid in the torque vectoring?
Service comment:
The famous Kuznetsov_NK-12 turboprop engine /w counterrotating propellers was developed from a German wartime Jumo 022 engine. A team of German engineers, highjacked by the Soviets, under the leadership of the Austrian Ferdinand Brandner developed this masterpiece, which is until today the most powerful turboprop engine ever.
да, вы правы, после отъезда немецких инженеров , русский гений закончился -))) Большое спасибо немцам , настоящие инженеры !!!
@@user-ts3ou3zn9x Said who?
@@rizzochuenringe669 Желательно всем списком и показывать это 24 часа по русским каналам . Официально это долгие годы замалчивалось .
@@user-ts3ou3zn9x I bet you wasn't the only Soviet citizen who didn't know these facts. Totally unimaginable that foreign subjects could teach Russians how to develop high tech equipment.
I'm no engineer, so of course I bow to those who designed these time-proven, effective systems. But to this layman, it seems like an unnecessarily violent way to claw through the atmosphere: The front prop sends the air laterally one way - only to quickly meet an opposing force that must work harder to redirect it the other way. What a chaotic airflow - intuitively, it seems rife with wasteful pneumatic friction.
Well it was a solution to a problem which creates a smaller problem in my opinion of air turbulence which increases drag but you also have to remember this plane is the fastest of its type so drag didnt take that much of a toll in the end.
@@finlaymcdiarmid5832 Clearly they knew what they were doing. This is just me shaking my head at the counter-intuitive-ness of it all.
@@pbasswil to me it just seems like the best card on the table considering the positives to negatives but there havent been any big developments in propeller planes in decades so the quest is open to improving them which wont be achieved if we dont play devils advocate now and again with tried designs.
@@finlaymcdiarmid5832 None of us YT commenters have PhDs in fluid dynamics, so we can safely leave the design choices to those that do. My comment was just about how counter-intuitive this particular design seems - at least it seems so to this laymen. Just one of many good reasons no one has put me in charge of any new plane projects.
@@pbasswil you dont have to have a degree to innovate. The first intercooler was invented by someone who didnt even go to college, it was simpler back then but if you want to try theres no one stopping anyone. i know that you find it counter intuitive im not attacking you for that.
What is the maximum number of counter-rotating blades a plane can have, before reaching the point of diminishing returns? What affect would a third counter-rotating blade have on power and performance?
YES
They use that same concept in outboard boat propellers as well in some applications.