Talk:Helicopter/Archive 1

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Contents

Page quality, focus and coverage

This article is huge and hairy, with far too much on type recognition and not nearly enough about what makes them fly or how to control them, their advantages, benefits, limitations and hazards. The Helicopter rotor is the beginning of an attempt to redress this but it has been threatened with merging into the main article.

Eventually I or some other pilot or engineer need to drastically rewrite the Helicopter article to address these issues. Benet Allen 22:08, 23 December 2005 (UTC)

Misleading description of airfoil lift

It is said in the article that "an area of lower air pressure is created above the wing, and this "sucks" the aircraft up". This is highly misleading. Lift is created because of the opposite reaction of forcing an air mass down. The fluid dynamics of creating usable lift is quite complex and is well discussed in many places. This article should reference a more accurate description of lift creation.

Thanks for pointing that out. Our own article on lift gets it right, so I summarised that explanation here. -- Heron 20:01, 2 Apr 2004 (UTC)
Actually there's nothing "misleading" about the original description of lift (which is based on Bernoulli's Principle). The two descriptions are fully equivalent, as even the Wikipedia lift page says. ("The force on the wing can also be examined in terms of the pressure differences above and below the wing.") The simplistic "angled surface" description proposed by Heron is better suited for describing a lifting body while the air pressure (Bernoulli) description should be used whenever an airfoil is involved. Hopefully Heron will concede and make this fix. He should also present his credentials on this subject matter and provide reputable sources rather than taking information from other Wikipedia pages at face value.
Why is it that lift is so controversial? I think everyone will agree that pressure below an airfoil is greater than the pressure above. This is readily verified experimentally, if there is any doubt. Further, numerous references document the magnitude of pressure at all stations for common airfoils and at varying angles of attack. Of course, comprehensive, theoretical treatments are more involved, but I don't think the casual reader is prepared for that level of rigor. Madhu 02:51, 1 September 2005 (UTC)

Gyroscopic Precession

I would like to weigh in on this controversy - by stating that helicopter rotors do not really experience "gyroscopic precession." As some sort of proof, few helicopters have "precession" angles of precisely 90 degrees, and many have cyclic phase angles (so-called Gamma) of much more or less than 90 degrees. In fact, the phase angle of a rotor changes as the forward speed changes, and all rigging on production helicopters is a compromise. The convenient explanation by relatively unschooled flight instructors to explain Gamma has resulted in a backwards proof-by-popular-belief that helicopter rotors experience precession. In fact, the flapping frequency of a helicopter blade (and its phase angle) is governed by many physical principles, with conservation of angular momentum as a large term, but also with blade flap natural frequency, blade flap intertia, blade flap damping, forward flight speed and blade lift-curve slope as the driving terms. If a blade has sufficient flap inertia, the Gamma can be almost 180 degrees, with little flap inertia, the Gamma can be less than 90 degrees. I toss out these facts to attempt to entice the reader to understand that blade flapping natural frequency (Gamma) is not really gyroscopic precession at all, but a cousin, where conservation of angular momentum is an important but not solo term. I have found it best to explain to new pilots using gyroscopics, but to avoid this term among helo dynamicists to avoid a lecture! Nick Lappos, ex-Sikorsky Chief R&D Test Pilot and Aerospace Engineer.


Explanation of cyclic control lead angle by reference to gyroscopic precession is common (and convenient) but incorrect. Gyroscopic precession is a phenomena resulting from conservation of angular momentum. It is only true for a rigid body. Helicopter rotors are not rigid. Many are articulated and even the so-called 'rigid rotors' are really quite flexible. Indeed, if they were rigid and were gyroscopes, gyroscopic rigidity would require huge forces to change the plane of rotation and helicopters could not be adequately manoeuvred. Cyclic lead angle is quite easily understood if, in a cyclical sequence, the difference between maximum pitch angle and the maximum flap up of one blade is examined. (i.e. Maximum pitch angle gives maximum rate of flap up but not maximum blade height). While I agree that too complex an explanation would not be appropriate in this article, I would urge that factual inaccuracies should be avoided. The Gyroscopic Precession myth has confused helicopter students for too long and should not be perpetuated.

John Annan


But when the rotors are spinning at full speed they behave like a rigid body, right? Or at least semi-ridged. And they have some flexiblitly, but not that much, otherwise they would be useless for controlling the helicopter. This has come up recently in an RC heli forum, and the more I read, the less I know what to believe. Obviously there are gyroscopic forces being applied to helis, but just how much of an effect this has on the cyclic controls is the real question. Do you have any links to back-up what you are saying? — Soupisgoodfood 16:08, 14 March 2006 (UTC)

I'm going to remove the part about gyroscopic precession, as I think John is correct. It's better off not being metioned at all than having something that might be wrong. Here it is, incase it needs to be put back in at some stage:

A peculiar feature of the cyclic is that the lift is made to occur 90 degrees of rotation before the direction of tilt. This is because when one tries to tilt a spinning object (like a rotor), it moves at right angles to the direction of the force. This is called "gyroscopic precession". So control forces on the rotor are rotated 90 degrees before the desired motion. For example, forward motion requires less lift at the front of the disk and more lift at the rear of the disk, so the pilot pushes the cyclic forward. The helicopter's control linkages rotate the pitching forces 90 degrees backwards against the rotor spin, to push on the sides of the rotor rather than its front and back. It took inventors many years to recognize precession, and to learn how to arrange the cyclic's control system to overcome it.

— Soupisgoodfood 04:35, 23 May 2006 (UTC)

Oh great, i think John is wrong, should i change it back? I won't do this because you obviously have a greater insight into this matter than me. Short explanation what i think:
Okay, John also assumes that a rigid rotor would have gyroscopic precession. Short explanation for a rigid main rotor. The main rotor is rotating (even quite fast), has a mass, therefore has a angular momentum, angular momentum vectors wants to be conserved, cyclic pitch results in a external torque, rougly said "cross-product ... right-hand rule ... tilt shifted by 90 degrees (precession)". You can also use Euler's equations to calculate the resulting motion better.
Of course the helicopter is more than a rigid rotor and the rotor is not that rigid (hinges, flexibility). There is also the angular inertia of the rest of the helicopter, and more complex aerodynamic effects. E.g. RC helicopters have quite rigid rotors, they survive the huge force, and they suffer from gyroscopic precession (at least this applies to the most RC helicopter i know).
So this explanation is all an approximation (better for RC helicopters), that may be the reason why real helicopters don't rotate the control linkages by exactly 90 degrees, but i haven't calculated that through. But please don't tell me conservation of angular momentum does not apply to helicopters. The equations just get more complicated.
You can probably explain all this without explicitly using conservation of angular momentum by going back to even more basic laws like the Noether's theorem, but why? Most people do it wrong when they try it.
Btw. the book cited on this page (W.J. Wagtendonk, Principles of Helicopter Flight) gets it quite right in my opinion, even if some people think different. Just read the mentioned pages (sample pages are free on amazon.com if you have an account). -- DeQuibbler 22:04, 23 May 2006 (UTC)
I'm sure gyroscopic precession affects pretty much all helicopters to some dergee. My question is if gyroscopic precession is a fundamental principal of helicopter flight. I mean, if it is, then the downdraft created by the cyclic should also preceed by 90°, right?
I played around last night with my RC heli. It's a 2 blade teeter with a flybar system, CW rotation. When applying forward cyclic, there was a small downdraft on the right side, where the blade pitch would be at maximum angle of attack. But the strongest downdraft was at the rear, where the blade pitch would have been 0°. It also tilted to the right slightly; that was probably due to gyroscopic precession. It seemed to reinforce the idea that the controls are rotated 90° because of aerodynamic reasons, rather than gyroscopic.
I also came across a thread of people talking about why their coaxil RC helis had a 45° offset, rather than 90°. There was a lot of talk about gyroscopic precession, and two rotors cancelling out resulting in a 45° vector, but they never really came to a clear conclusion.
Also, I didn't know that most full-scale helis didn't rotate their controls by 90°. Can you provide some links? So is that removed paragraph wrong either way? — Soupisgoodfood
Greater downdraft should be at the rear. You pushed the cyclic forward, so the helicopter should move forward, right? The right tilt is due to translating tendency. Full scale machines do the same thing (left skid low for American models). It's a little annoying, IMHO.
Are you saying full-scale helicopters don't rotate their controls by 90°? I assure you they do. In general, most full scale swash plates tilt in the same direction as the cyclic. The pitch horns are on the leading side of the blades with pitch links at 90°. Take a look at image in this article. Madhu 23:47, 24 May 2006 (UTC)
No, I'm saying that they are generally rotated 90°, but for aerodynamic reasons, not because of gyroscopic precession. — Soupisgoodfood 14:45, 29 May 2006 (UTC)
Okay, just remove everything you don't understand. i should try that, wikipedia would be quite empty then ;) Another short try without starting a physic lesson. Of course its due to aerodynamic reasons: Aerodynamic effects (e.g. lift) are the cause of the external forces affecting the rotor. So if the main rotor would rotate in outer space, no lift, no external forces, no 90° phase shit. But if you have thrusters at the rotor blade tips you have your forces and 90° phase shift again, because of the gyroscopic precession. Btw. of course gyroscopic precession is not explaining all movements of the helicopter, and there are more complicated aerodynamic effects (e.g. induced velocity).
Btw. its right that coaxial helis should not observe 90° phase shift as both angular momentums cancel out as they rotate in the opposite direction. -- DeQuibbler 23:43, 29 May 2006 (UTC)
I understand what happens. But it seems that many people want to carry on the gyroscopic precession myth. Controls are not rotated 90° because of gyroscopic precession. Can we be clear on that? — Soupisgoodfood 04:06, 31 May 2006 (UTC)
No. There is no gyroscopic precession myth. Just a gyroscopic precession misunderstanding. You have misunderstood me. Short try again: cyclic pitch on the main rotor -> change of forces affecting the rotor (by aerodynamic effects) -> 90° phase shift of resulting motion (compared to what you expect for "normal" nonrotating objects).
Of course you can explain the 90° phase shift by the intertia of the rotor blades during their rotation (probably this is the same as the "to allow time for the blades to 'fly up'"-explanation somewhere on this page). Effectivly you would derive the gyroscopic precession then, that does not make the gyroscopic precession explanation wrong. I think gyroscopic precession explanation is easier to understand (if you accept gyroscopic precession as learned in school). -- DeQuibbler 18:55, 31 May 2006 (UTC)
I'm sorry, but the more I research this, the more I find that you are simply wrong. Have a good read of this: [[1]]. The (usually) 90° phase shift is not because the force applied to the rotor hub is lagged 90° because of gyroscoptic preccession, but because maximum pitch on the blade does not apply force to the hub immediatly on teetering or articulated heads, because the blade needs time to travel up (or down) before it applies a significant amount of force to the the hub. — Soupisgoodfood 05:57, 1 June 2006 (UTC)
If you think so, i know better. Sorry, but usually people who have no idea what gyroscopic precession is challenge the explanation. I don't know if this applies to you. Both explanations are valid. Inertia (because the blade needs time to travel up...) can also be used as explanation. Inertia in rotating system ... moment of inertia ... Conservation of angular momentum ... "gyroscopic precession". Conservation of angular momentum is also valid for non-rigid bodies, equations just get more complicated, and it won't be "pure" gyroscopic precession as we know it anymore. Think i said something like that already Well, but i don't want to convice you, think it is too time consuming ... -- DeQuibbler 20:19, 4 June 2006 (UTC)
OK, I've been reading threads on PPRuNe.org by factory test pilots and engineers who say the phase lag is not there because of gyroscopic precession. I'm not saying it doesn't exist, because it does. But it (or angular momentum, whatever you want to call it) is not the dominating reason for phase lag in most rotor systems. The phase lag is because in articulated and teetering systems, the blade takes time to travel up. Phase lag often isn't needed in rigid rotor systems. This goes against the gyroscopic precession theory, which says that a rigid rotor system would suffer from the 90° lag more than a non-rigid system. — Soupisgoodfood 04:06, 7 June 2006 (UTC)
A rigid rotor system would suffer not some 90° more phase lag than non-rigid. This was never claimed. The equations to model a rigid rotor are really simple. And they show 90° phase lag (+some minor other motions). Show me an example where phase lag is not needed for rigid rotor system. -- DeQuibbler 22:15, 14 June 2006 (UTC)
I don't have much info for rigid rotor systems as their aren't many out their, and out of the ones that are, they aren't truely rigid anyway. I could pull quotes from RC heli forums, but I don't think that's a valid source. Anyway, that still doesn't change the original point. Are you really saying that you know more about phase lag that someone who has worked at Sikorsky for over 30 years in the R&D area, including being a test pilot and director of test engineering? (Nick Lappos, in case you're wondering.) Have you even done any practical experiments yourself? — Soupisgoodfood 08:10, 16 June 2006 (UTC)
So were do you get your knowledge from, that rigid rotor systems would suffer 90 degrees more lag? Well probably from some forum, because thats nonsense. You gain your knowledge from some obscure sources, where everyone posts their rubbish (well similar than some wikipedia articles). You are quoting some people out of context. If this guy claims that the simple 90° gyroscopic precession is not really exact, he is perfectly right. It is an simple explanation which does not consider everything. You could also argue that gyroscopic precession is only called like that for rigid bodies. But as you allready said, no real body is really rigid. Conservation of angular momentum allways applies, even for non-rigid bodies, and you can derive the dynamic equations predicting 90 degrees "phase lag" for simple models of the helicopter from the conservation of angular momentum. For more complex models there more complex predictions of the dynamics.
Maybe you should read some books rather than some opinions of some people in some forums, so that you can derive your own dynamic equations for a helicopter and draw your own conclusions. -- DeQuibbler 19:14, 27 June 2006 (UTC)


Forget about ridge rotors, that's getting off topic. Have you considered that those books are wrong? Perhaps you should e-mail the lead engineer at Sikorsky and ask them? I mean, you still can't even answer a very basic question that I asked a while ago: If the phase-lag is 90° because of gyroscopic precession, then the strongest downdraft created by the cyclic when applying forward cyclic in a clockwise turning rotor system should be on the right hand side. Do you argree with this statment? --Soupisgoodfood 20:32, 30 June 2006 (UTC)
Okay, if you don't like rigid one. Yes, i always consider that books can be wrong, this really happens more often than you might think, but not this time. Why should i bother this busy man? Yes, of course the same lag can be observed in the downdraft generated by the cyclic pitch (of course for the "downdraft from collective pitch" there is no lag), but that should be independently true for both explanations.
But lets close the discussion, as long as you only delete the correct explanation and do not write in the article that the correct explanation is wrong, it is okay with me. -- DeQuibbler 12:46, 5 August 2006 (UTC)


I wouldn't normally link to web forums as proof, but if you do your research on who Nick Lappos is (as I mentioned before), it's pretty hard to argue against him: [2], [3].
Also, I don't mean that there's a lag in the downdraft relative to the helicopter, just relative to the blade. If you agree that there's an aerodynamic lag, then that still doesn't change the fact that if gyroscopic precession was such a large force, then the cyclic downdraft -- relative to the heli, not the blade -- should also preceed the movment by 90 degrees, which is doesn't.
If you are so sure that you are right, then why not re-insert the original paragraph? --Soupisgoodfood 18:08, 6 August 2006 (UTC)
This has to be one of the most interesting topics relating to helicopter flight. During my flight training many moons ago, I was given a copy of the Basic Helicopter Handbook (published by US DOT/FAA) for use as a reference. This book specifically suggests gyroscopic precession as a justification for 90 degree phase angle. If you look at a real rotor hub, it's clear the phase angle is about 90 degress, so I more or less accepted the gyroscope theory. As a physicist, it never quite sat right with me. There wasn't a simple, back of the envelope equation that screamed 90 degrees. Comments by Nick Lappos caused me to go digging through my copy of Helicopter Theory by Wayne Johnson (pp 184-187, 212, 222-225, 227-230). The math is not trivial, but not difficult to follow. Basically, Nick is correct (if that was ever in doubt). The problem is that there's no simple, intuitive way that I can think of to explain it (maybe a harmonic oscillator analogy?). In the ideal case, the phase angle is exactly 90 degrees. The numerous factors enumerated by Nick all contribute to a phase angle different from exactly 90. Many of these are analyzed in good detail in the book. The variation with forward airspeed is particulary interesting to me as a pilot. I never really thought about it, but some lateral cyclic is necessary to compensate for it. I think I noticed it in flight, but wrote it off as some other factor. Of course, it's probably easier to just to deal with it than to think about it ;-) I'm not sure it would be worthwhile to include the full analysis in an article somewhere, but it is worth explaining some of the contributing factors. At least that would help to objectively address the gyroscope controversy. Madhu 03:49, 11 September 2006 (UTC)

Why?

when viewed from below the rotor of a French, Russian, Soviet or Ukrainian designed helicopter rotates anti-clockwise, whilst a helicopter completed in Italy, the UK or USA rotates clockwise.

Are there laws that tell helicopter designers to do so? -- Toytoy 01:46, Jan 25, 2005 (UTC)

There are no laws as far as I know. I think it basically comes down to historical reasons. If you were trained in a clockwise helicopter, you might prefer clockwise. Any decent pilot can fly either one, you end up doing the right thing with the pedals anyway. I read in a helicopter theory book that the choice is arbitrary and the decision should be made on technical merits, e.g. engine shaft rotation, geometry of suitable transmissions etc. Madhu 16:35, 26 Feb 2005 (UTC)
Another possible explanation that I've heard is that during World War II the Germans were working with twin contra-rotating rotor designs as in the Focke-Achgelis Fa-61, and when the war ended, the French started their helicopter industry with leftover German parts. For some reason there was a preponderance of main rotor components that advanced to the left, so that's what they used, and it became entrenched in French designs. The Russians simply copied the French. If Igor Sikorsky had still been in Russia, it might have turned out different, but he had emigrated to the United States decades earlier. Sikorsky decided to make his single main rotor advance to the right, and the postwar British, German and Italian helicopter industries followed suit. Quicksilver 08:12, 5 November 2005 (UTC)

An interesting point to make here is that Sikorsky used a truck differential as the gearbox in his first prototype helicopter. What determined the direction of rotor rotation was that he probably put the crown gear at the top nearest the main rotor because he wanted to reduce oil frothing. As it went, when he demonstrated his prototype helicopter the gear box failed at the end of the flight anyway because the lower crown gear bearing was allowed to run constantly emersed under the oil level. This is a no no when designing a gearbox. Bearings have to be oil splashed to work properly. Simply the gears get hot and transfer the heat to the shafts. This heat is then transferred to the inner-bearing race of the lower crown gear bearing, which expands onto the bearings, which are held too tight because the outer race is being cooled excessively by the surrounding oil. All other helicopter experimenters in America used the same short cut of using a truck differential as the gear helicopter gearbox. So the direction of rotor rotation for American helicopters and all that copied was because they originally used a truck differential rather than manufacturing a gear box from scratch like the Russians and other European countries did. Those who are wondering why a truck and not a car differential well, its because truck differentials have a very low ration of about 8 to 1. Cars are about 4 to 1 which is way too high when considering the maximum power range of a combustion engine and the ideal rotator size and speed required for a helicopter. 7 Nov 2006. —The preceding unsigned comment was added by 210.84.17.252 (talk • contribs).

Countries

The article divides its list of helicopters into "Popular US army" (including at least two aircraft in common use internationally), "Other military", and "Civilian"

Why have a special category for US army helicopters on this page? There are thousands of similar customers who buy helicopters. Wouldn't a simple military/civilian or fighting/general-military/civilian scheme seem more logical?

Very Negative

I am interested in becoming a pilot and I find this article not very helpful. Instead of showing how the helicopter is actually mechanically controlled, like how the cyclic actually rotates the blades, all this article does is explain ways of how helicopters fail, crash, can be stalled, and destroyed. (67.83.10.27)

Then, you can improve. That's why we use wiki, isn't it? - Marsian // talk 23:09, 2005 Apr 11 (UTC) I apologize for my disappointing comment... - Marsian / talk 00:17:19, 2005-09-04 (UTC)
When I considered learning to fly helicopters at a newly opened training facility in the early 1980's, more than a dozen prospective students showed up for the introduction. When the chief instructor described the various ways one could get killed in a helicopter, four or five individuals stood up and walked out, never to return. Those are the brutal facts of life for helicopter pilots. Deal with them and live, or ignore them and die. Quicksilver 08:20, 5 November 2005 (UTC)
Some interesting statistical evidence: since the introduction of the Robinson R22, helicopter accidents and incidents have risen dramatically. After careful study by the FAA, it was concluded that there is nothing wrong with the R-22, the problem is pilot error. The R-22 was the first widely used trainer that was accessible to the average aviator. The dramatic rise in accidents was due to a large number of non-military pilots discovering helicopters. There's a great write up about it. Basically, 92% of accidents were due to pilot error and all were preventable. I don't have the exact numbers, but more than 10% of all R22s sold were destroyed in accidents. One that I flew was severely damaged once (with an instructor) and completely destroyed later by a solo student. When I learned to fly R-22s, the throttle governer was an expensive option that no one purchased. Now it's required. SFAR 73 is another example of efforts to try and deal with the challenges of helicopter pilotage. Most FBOs now make renters sign a statement restricting flight maneuvers to the basics: no autos of any kind, no settling with power, no slope landings, absolutely no low-G maneuvers. Given the stats, I can't blame them. Here's a vivid example of what can go wrong.

When I learned to fly the same story happened to me with the people walking out. After one month, one of the trainee student pilots took his hand off the cyclic control. The lesson finished at that point and I watched him walk out of the chief pilots office crying. You dont get a second chance. They politely tell you, "nothing personal but you have not got what it takes". I use to turn my head when talking to the instructor and he would cut the engine every time and you have three seconds to do everything you need to do to put the thing into an autorotation inorder to save your life. My instructor would sing or talk about girls and crack jokes and as soon as you smiled or laughed he would cut the engine. They do everything humanly possible to make you make a mistake including rushing you and overloading your work load. They ask you the best way to do an exercise and then make you do the exact opposite. Other than that I enjoyed every minute of learning to fly and I hope you do to.

Another reader here would very much like to know more about fuel types, engine and powertrain layouts and other such matters.

I've been thinking about these subject for some time now. I think there are several more articles that could be started:

  • Helicopter pilotage
  • Helicopter design, e.g. rotor, rotor head, tandem rotor design
  • Helicopter engine/powertrain (this might be combined with above)

Anyone have any ideas how this should be structured?? If someone gets it started, I can add a lot of content Madhu 15:20, 12 August 2005 (UTC)

Howabout something like Anatomy of a helicopter? Ojw 18:31, 12 August 2005 (UTC)
I intend to start an article on Helicopter Pilotage. Basically the flight control inputs and the resulting response from the aircraft.--Mbaur181 20:45, 31 August 2005 (UTC)

Sikorsky

Isn't Igor Sikorsky considered today the inventor of the helicopter? The history part of the article makes very little mention of it and sweeps Sikorsky under the rug with other inventors like the history paragraph was edited

Also what purpose does the phrase "Incidentally, the Wright brothers were given this toy as kids and were very much fascinated by it." serve in an article about helicopters?

I think this article has gotten way too big by itself. It really needs to be broken down somehow. There's so much information, some of it trivia, but a lot of solid foundation that it's just too hard to capture in a single article. Maybe this article should be just a short summary of the major topics which link to more detailed articles? For instance, the history of helicopter development can be an article by itself. There are a lot of people that had a hand in it and Sikorsky was a major player. Madhu 16:42, 21 August 2005 (UTC)
I don't believe we can consider Igor Sikorsky as the inventor of the helicopter. The puzzle of rotary wing flight was partly solved by many contributors before him, although his VS-300 design was among the first practical machines. To call Sikorsky the inventor of the helicopter is analogous to calling Henry Ford the inventor of the automobile -- historically inaccurate at best.  I agree that the article is getting a bit large and unwieldy. Helicopters are a complex subject, and perhaps the material on the mechanics and aerodynamics should be separated from the material about operating them.  Quicksilver 18:29, 4 November 2005 (UTC)

It does not say he is the inventor of the helicopter. It says "The first stable, fully-controllable helicopter placed in production was invented by Igor Sikorsky" The key word is production. Engineered is a better word rather than invented, perhaps. I dont think he viewed himself as an inventor. He actually went to many engineering schools in Russia and Europe to become an engineer not an inventor. Sikorsky is greater than Henry Ford because Ford mass produced something that was already in limited production elsewhere. Sikorsky invented very little but like the genius engineer that he was, he took the right parts and made them work to produce the most effective and efficient design which today 65 years on is still the most common design used. If it was that easy why didnt someone else do it in the 30 years previous. If you read the history every aviation scientist and engineer in the world had a go at this problem. They also had the knowledge of what had been done before. I believe he had the design in his head when he was in Russia around 1912 after he failed on his first two attempts at building a helicopter and probably he was greatly influenced by another Russian aviation scientist called Boris Yuriev who tried the right concept but did not engineer it properly. Also Sikorsky admitted after he was successful in 1939 that he did not show his cards until he knew that there was an engine with enough power to weight to do the task. I agree with the comment that the artical is a little too long. I was going to add to the articals history section about how and who invented each major component that eventually made up the Sikorsky layout. When I planned it out, with no exaggeration, it would have doubled the size of the artical. I also do not like how the author calls the rotors as propellers then it goes on to call the rotors as rotary wings which is correct. I think it should be rotary airofoils. Every book that I have read on helicopters refers to the main rotor and tail rotor as having airofoils. I also, do not like the reference to the Wright brothers. It’s not necessary. I also think the inventor of the turboshaft engine needs a mention. Joseph Szydlowski who was a Polish born and educated engineer who founded the French Turbomeca engine firm. About 60% of the western world’s helicopters have a Turbomeca turboshaft engine powering them. In the alternative layouts section it talks about the Ch-47 Chinook helicopter and its tandem rotor system but there is no mentioned of the inventor of that system Frank Piaseki. Like Sikorsky his company Vertol developed and flew the world’s first mass-produced tandem helicopter. The Vertol aircraft company was latter acquired by Boeing. This then became the helicopter division of the Boeing Aircraft Company. He developed the current day CH-47 Chinook. There also needs to be a bit more information given about NOTAR, in particular the Mc Donnell Douglas helicopter NOTAR design with a picture of the helicopter side on and a hyperlink page explaining its principles. It was the first accepted and mass produced NOTAR system in the world. Also there could be a whole new page dedicated to rotor head design as well. I feel that most of the pictures are the wrong choices. They’re not SEXY. The first picture seems to be an advertisement for the Canadian Helicopters company with a hyperlink to a page dedicated to that company. There should be a Robinson R22 instead of a R44. Its much more significant and is representative of the small helicopter class. There is a nice picture under Robinson R22 that could be used. Also the Kaman V Max, CH-47 Chinook, Sikorsky S-64 skycrane, Mc Donnall Douglas MD 520N and maybe Frank Piaseki's High Speed Compound Helicopter to show what is coming in the future. Also the American AH Apache and a Russian Ka-50 Werewolf to show what the cold war did for the development of the helicopter. Can anyone help here please with these pictures. All of these are very important examples of the different utilizations of the helicopter. I feel the Enstrom and Bristol should be taken out because they are not significant in the story of the Helicopter.

OK, can we stop with the Sikorski propaganda? First, the article credits him with "1st stable type in production", then FA-61 with "1st successful type", then some guy I never heard of with "invention". If the German '30s designs weren't stable, how'd they become successful? Luck? Stupid customers? The pix I've seen, they look pretty stable in flight, but then, I'm not working for the Sikorski propaganda dept. And the writer here? I'm damned if I know what to think, now. That's without mentioning any of the 1907 trials in Fr, either... Or the Rus twin-rot outrigger designs. Neither, I see, got mentioned here. Some research, & a lot of cleanup, seems in order.... Trekphiler 18:04, 4 December 2005 (UTC)

“The first stable, fully-controllable helicopter placed in production was invented by Igor Sikorsky” is entirely correct. The FA-61 developed by Heinrick Focke of the Focke-Wulf Company in Germany in the early 1930s, which you refer to, used a tilt rotor system for back and forward movement as well as rolling left or right. It also required the changing of rotor speed to control lift. This means that you could not rotate the aircraft around a vertical axis in the hover or fly sideways, and when transitioning into forward flight it was reported that this type of design was very unstable and in fact many crashed during this procedure. I personally don’t think any machine that was pushed into production because of Nazi aspirations could be classed as successful. But you are right, you would be “lucky” to have survived a flight in any of Fockes helicopter designs and the buyers of this helicopter who followed Adolf Hilter a confirmed psychopath with bipolar disorder would have been as you put it “stupid customers”. The article also states that the Focke-Wulf Fw-61 was the first practical helicopter, not as you state the “1st successful type” and this is entirely correct as well. It did achieve vertical and forward flight and was produced in limited numbers but not one of its design features are in any form of helicopter configuration which is in production today. The closest design would be the V-22 Osprey which has tilting wings with attached rotors for forward flight lift and thrust as well as the two rotors having swash-plate control which means it can rotate in the vertical axis in hover and fly sideways. (So was the Focke FA-61 really a helicopter if it could not perform all of the criteria of a helicopter.) Vertical take-off and landing with controlled flight are the fundamental helicopter criteria. Talk to any helicopter pilot and they will tell you it is critical to turn the helicopter in the vertical axis in ground effect hover fully loaded into wind before attempting to transition into forward flight. The same applies when attemting to hover out of ground effect like when attepting a person winch or load lift on the hook or rotate for camera angles. Rotation in the vertical axis is critical for stable flight of the helicopter. This is why many aeronautical engineers even before Sikorsky's 1938 VS-300 have argued that the Focke FA-61 was not a helicopter just like the gyrocopter is not a helicopter even though very similar.

The main point to make is Sikorsky patented the single large main rotor with smaller anti torque tail rotor design in 1931 which is before the Focke FA-61 design and the Sikorsky design incorperated the used a swash-plate rotor head. He also kept rotor speed constant and combined cyclic and collective control of rotor airofoil pitch. He devised a tail rotor head design which could vary thrust depending on blade pitch and overcame dissymmetry of lift in forward flight for both the main and tail rotor by designing main and tail rotor heads with flapping mechanism. All of these design features are still used as the base platform for multiple helicopter manufacture designs in many different countries today. That is why Sikorsky is considered the father of design of the current day helicopter. You have to study the design engineering aspect of helicopters to understand that, not just look at pictures. I am “the writer here?” you refer to. I have not edited or contributed to the main article in any way but I do follow its progress. The history of the helicopter is extremely complicated and I don’t think a 1000 page book would do it justice so for this reason many things are missing. Some people are going to be disappointed including me. On top of this is this old 20th century concepts of nationalistic pride, hence the reference to the Wright brothers which still bothers me. All of this makes the helicopter story so controversial. Many people want their national contribution to be the defining all-important turning point in what is a very complex and amazing machine. The fact is many people and nations contributed to the helicopter and for that reason perhaps it could be considered the first world invention because it came about in an era of people of different races being able to travel and integrate into other cultures and exchange ideas freely. I think without that it may not have happened as quickly as it did. Its the twenty-first century. It does not matter what side of the Atlantic something was made or if Germans are the master race or the English rule the world or American know-how gets it done. Get over it, Sikorsky invented the first stable, fully-controllable helicopter placed in production. Sikorsky was not born and trained in either America, England or Germany. Its not propaganda or a conspiracy to undermine your way of life. Hopefully one day you will be plucked out of the ocean by a rescue helicopter when you need it and you might go and visit Sikorsky's grave and thank him.

Getting onto something else other than Sikorsky, I note in the History section that "the Bell 47 designed by Arther Young was the first helicopter to be licensed" in the US. This should be "the first helicopter licenced for certified civilian use" in the US.

Wow! That's some great writing! Who are you, anonymous author? Madhu 00:10, 25 May 2006 (UTC)

It's just western propaganda. Yes a Russian invented it. Get over it.

-G

You wish. (Boy, I really p.o.'d somebody there, tho, didn't I?). FA-61's a tiltrotor? Every source I've seen (all I'd consider more reliable than such an obvious partisan) says "helicopter". That aiside, what's that make the Flettner Fl 282? A pipedream? (Ooops, sorry, I forgot, not designed by Sikorsky. My bad.) Not addressed by Mr PO is the contradiction in the article; if there's to be a "first", by definition, there should only be one, & in this case, Sikorsky ain't it. Was he brilliant? Yes. Was he the guy? No. Get over it. Trekphiler 01:37, 2 March 2007 (UTC)

poor tone

There is too much of a didactic personal tone to this article. It sounds like something you'd find in rec.aviation.military, not in Britannica.

Why do helicopters not use ring-protected rotors?

The article refers to the serious dangers of rotor-contact with a fixed object, the fuselage or people. Is there any reason that the rotors do not have some sort of ring fixed around the blades to protect them from contact-damage (or slicing someone in half)? Many of the (cheaper) radio-controlled model helicopters have this feature. Although I know you cannot apply the engineering principles for toys to full scale models, the article could be improved by addressing this issue, especially since it is implemented in model helicopters.

A ring attached around the outside of the rotors would (in theory) prevent the rotor damage and jolting of the hub mechanism that makes contact so dangerous. A ring could also support the rotors in tension when they sag downwards and reduce the problem of fuselage contact under low/zero-gee flight conditions. If each rotor was attached to the ring via a swivelling plain bearing shaft, the ring would not impede the ability of the blades to flex during forward and backward rotation when in forward motion. A ring would also reduce the radial flex of the rotors (assuming this is problematic, perhaps increasing vibration).

The above reads like a design proposal, but I'd like to know why this feature is almost or never-implemented in real designs (I guessed the reason is one of 'too much to go wrong', by the way).--ChrisJMoor 02:08, 7 January 2006 (UTC)

It's never implemented, even though blade strike accidents often have tragic consequences:
  • A ring would add a significant amount of mass, and hence rotor inertia, where it isn't wanted - at the blade tips
  • A ring would prevent blades from flapping up and down as they face towards or away from the translational airflow
  • A ring would prevent blades from leading and lagging, which is necessary on systems with more than two blades
  • In order to provide a realistic degree of blade strike protection, such a ring would have to be massively strong and contribute a big weight penalty

There may be more reasons. If other users agree I may add this to the main article! Benet Allen 10:54, 7 January 2006 (UTC)

I see, although if a hypothetical ring attached to the rotor blade tips via some flexible joint as detailed above I dont see why it would prevent desirable rotor flex. Good to see a pilot contributing to the discussion. Someone must have considered the feature at some point in helicopter development; you could add a reference or external link if one exists.--ChrisJMoor 07:53, 8 January 2006 (UTC)

The above question and answer has been adapted and incorporated into the helicopter rotor article

Is the Swashplate 90 degree phase shift really based on 'gyroscopic precession'?

On german wikipedia (http://wikipedia.de/hubschrauber) we had a discussion about the reason for the 90 degree phase shift (Phasenverschiebung) between the Swashplate (Taumelscheibe) actuation and its effect on the rotor circle plane. The first version of our text seems to have been simply a translation of the english text that is online here. It seems the gyroscope effect is a common but wrong explanation for the shift. We came to a different position - starting from here:
"A very peculiar feature of the cyclic is that the lift is made to occur 90 degrees of rotation before the direction of tilt. This is because when one tries to tilt a spinning object (like a rotor), it moves at right angles to the direction of the force. This is called "gyroscopic precession"."
But this way one can not tilt a gyroscope in a certain direction - instead the gyroscope will start to rotate based on the impulse from the 90 degree force - just try it out with your suns Top. This is a thing you dont want to happen on a helicopter.
A helicopters rotor-swashplate-assembly works different: Only by giving it the freedom to swing up and down (in a bearing or elastic housing) the rotor blade can tilt on its circle _without_ gyroscopic effects. We understand the blade is steered in the desired position by changing the blades Angle of incidence at certain angles on its circle. But the incidence does not affect the _position_ of the blade but its _acceleration_ into this position: The acceleration has to be the highest 90 degrees before the desired highest position because the blade continues to move into the higher position even with a decreasing acceleration for the next 90 degrees. Only then the blade will start to be accelerated into the opposite direction and will reach this another 180 degrees later.

Now I am not an english native speaker, furthermore, I am not sure if the laws of physics are seen the same way in the anglo-saxon world as in our central-european (after that Iraq discussion ... ;-). So I ask you to check your sources, consult your local helicopter engineer - and change the article accordingly. What I did was shift the phase-shift-discussion to the swashplate article (http://de.wikipedia.org/wiki/Taumelscheibe), shorten 'Helicopter' and link from there to Swashplate. --84.189.169.88 00:08, 14 January 2006 (UTC) (http://de.wikipedia.org/wiki/Benutzer:Bernd_vdB)

That's great, but I'd appreciate it if you could perhaps illustrate it with picture and words from Helicopter rotor and link back to same!
There is no gyroscopic precession involved in the operation of the rotor blades. Pitch commands are given 90 degrees 'in advance' to allow time for the blades to 'fly up' to the desired position, that's all. (I can't put it any more simply than that!)
Far too many helicopter students, who later become instructors, end up thinking this is a kind of gyroscopic precession - it simply isn't, that's all! Our German friend at the top is exactly right.
Feel free to quote me, and my excellently readable source, W.J. Wagtendonk, Principles of Helicopter Flight ISBN 1-56027-217-1, pp169-171 Benet Allen 00:45, 14 January 2006 (UTC)
Great, I just answered to a (BO-105) helicopter pilot in german wikipedia: Diskussion Taumelscheibe
...who claims to have not only the technicians and instructors behind him, but the "Luftfahrtbundesamt in Braunschweig", the highest authority for aviation issues in Germany. So I offered him a BET : champagne for his team if they are right, a free flight for me if I am.
So the discussion is getting some (non-gyroscopic) momentum. Would it not be fruitful to start some similiar process in the US - with tons of helicopter pilots, veterans etc.? Make it a big story, bring it on TV? - Think about it and let me know .. --84.189.170.174 12:40, 21 January 2006 (UTC) ( bvdb at kanka.de )
This phenomenon is now termed "phase lag" in U.S. Army Aviation manuals and instructions. Gyroscopic precession was used traditionally as a method of demonstrating and explaining the phase lag phenomenon of the rotor system. Inducing an input to a spinning gyroscope 90° from a desired direction caused it to tilt and move in the desired direction. I'm not sure if the issue between the two is based on the origin of the change in rotational plane forces. In a rotor system, the blade is induced to fly along a new plane by the cyclic change of pitch rather than a torque induced onto a gyroscopic system. It is possible that the gyro stabilizer bars on Bell products and the Lockheed rigid rotor systems introduced the idea of gyroscopic precession into discussions of rotor wing aerodynamics. —The preceding unsigned comment was added by Born2flie (talk • contribs).

Stanley Hiller

years ago I was doing research on toy makers in the bay area, and ended up researching Stanley Hiller due to his having invented and manufactured toy cars (Hiller Comet) as a teen in his dad's garage in Berkeley. Though I have since essentially forgotten everything I learned, there were many newspaper articles at the time that seemed to credit him as having been instrumental in making helicopters practical. They practically credited him with creating the first working copter... I realize there may have been some exaggeration, but does anyone know if he was important in copter development, and would a mention here be warranted? Jafafa Hots 05:15, 16 January 2006 (UTC)

There was some interesting info about Stanley Hiller, Jr. at the National Air and Space Museum Steven F. Udvar-Hazy Center. Great helicopter display, BTW. I don't remember the details, but he sounded like a very impressive guy. He built quite a bit at a relatively young age. There's a nice scene of a Hiller 12E (I'm guessing) towards the end of Goldfinger. I believe he built one of the first coaxial rotor systems. This website has some good info, but it claims Hillers H-23s were used in the M*A*S*H (TV series). I don't know, they look like Bell 47Gs to me. I guess you shouldn't believe everything you read on the Web ;-) Madhu 02:09, 18 January 2006 (UTC)
M*A*S*H shows the Bell 47, although both airframes were in use during that time. (Born2flie 07:49, 6 September 2006 (UTC))

History: Gyroplane-Laboratoire?

In german wikipedia we feel that the french "Gyroplane-Laboratoire" from Breguet was "the first stable flying helicopter". One might consider at least to mention this model in the History section: http://de.wikipedia.org/wiki/Gyroplane-Laboratoire --84.189.159.223 01:19, 19 January 2006 (UTC) ( http://de.wikipedia.org/wiki/Benutzer:Bernd_vdB )

first North American helicopter flight in Rossland BC?

The article below is from the link: http://www.flyingsteamshovel.com/site/index.php?history


History of the Flying Steamshovel


Named after the first helicopter flown in 1902 by Louis Gagnon. Rumoured safe house for fist Canadian union reps. Built in 1897 to accommodate mine workers, there are over 200 shafts under Rossland,

Red Mountain Ski Hill the old mining site.


The Flying Steamshovel is named after a contraption that an enterprising dreamer named Lou Gagnon built, flew, and crashed right next to this site. Lou Gagnon’s dream was to ferry the gold ore off the steep lopes of Red Mountain by air, and on a February afternoon in 1902, his mysterious machine was skidded into the nearby yard for its maiden flight.


The helicopter plain, built of iron, wood and brass, appeared with its wings fabricated of canvas and piano wire. It was fitted with two steam engines - one to power the large overhead rotors, and one to drive the rear propulsion propeller. It bristled with gauges, valves and levers. Smoke curled from the twin stacks.


Gagnon’s moment was drawing near. With his eye on the steam gauge, Gagnon reached up and slowly valved the steam into the turbines, causing the main rotor to turn. He then cracked the throttle of the horizontal engine to make the push propeller tick over. Soon both were a blur and an invigorating downdraft blasted everything loose from the scene, including the crowd. The rickety framework began to shudder and finally the front end of the thing lurched free of the ground. At the same time the back end began to revolve from the torque.


Through a series of frantic adjustments, Gagnon did manage to get the Flying Steamshovel in the air above the height of the Hotel/ But in a final effort to control the spinning machine he turned off the upper valve of the turbine’s casing which disastrously caused the main rotors to come to a groaning and sudden halt. The tail dropped first and the Flying Steamshovel corkscrewed down, barely missing the hotel, and crashed upside down in an explosion of steam, smoke and cinders.


Lou Gagnon was pulled unconscious from the burning wreckage by two local firemen. He suffered a badly broken leg and burns to upper body and face, but eventually recovered to take up a life as a haberdasher in Spokanne.


Info@flyingsteamshovel.com

© 2004 The F

Oszkár Asbóth

How much is knowen about him and his contributions? Is he worth mentioning in the first paragraph? — Soupisgoodfood 00:20, 29 April 2006 (UTC)

Probably the best thing to do is expand the article Oszkár Asbóth first, before mentioning him here. DJ Clayworth 17:13, 28 April 2006 (UTC)

"The first helicopter able to fly vertically and levitate was made by Hungarian Oszkár Asbóth. " From the article Jan Bahyl his helicopter was able to do both of these and predated Asboth. Some explanation of the difference should be given. DJ Clayworth 18:15, 28 April 2006 (UTC)

OK, I'm removing it untill the original contributer or someone else can give a better explaination. — Soupisgoodfood 00:20, 29 April 2006 (UTC)

Native Americans and attack helicopters

Attack helicopters are used in the military to engage the enemy using missles and machine guns. Native americans are the people that have lived in the Americas before the Europeans came to colonize America.

There are some attack helicopters that are named after Native American tribe names, such as Comanche, Apache, or Kiowa.

Isn't it ironic, how, after the USA destroyed the Indians, then name their own attack helicopters Indian names? Isn't it ironic how a "Native American" helicopter, used by the United States, is used to destroy the enemy when the name of the helicopter itself was destroyed 150 years ago?

Good friend100 04:12, 15 July 2006 (UTC)

Yup. Pretty ironic all right. --Guinnog 04:24, 15 July 2006 (UTC)
It just bothers me sometimes when I read helicopter names. Good friend100 12:27, 15 July 2006 (UTC)
Prior to naming a helicopter after a Native American tribe, the U.S. Army receives permission from the tribe. I'm not quite sure how they could receive permission from something that was "destroyed". For sure, the Native American tribes' lifestyles were drastically altered and thousands were massacred, but conquered, subdued, assimilated all seem to be more accurate descriptions of the events of history. (Born2flie 08:27, 6 September 2006 (UTC))

Its just a thought and its ironic. Good friend100 18:47, 10 September 2006 (UTC)

Vortex ring state and Settling with power

Is the same. But there is two articles; vortex ring state redirects to settling with power. so that's one. and there is vortex ring. I'm fixing this article, because it treated it as two different thingeys. --80.63.213.182 15:10, 31 July 2006 (UTC)

NPOV?

The subsection titled "Reduction & Elimination of Common Helicopter Flight Hazards" under section "Hazards of helicopter flight" reads like a marketing brochure for the coaxial design. I'm not qualified to address the specifics, but the terminology used doesn't seem NPOV to me. 63.161.86.254 16:53, 4 August 2006 (UTC)

contradicting pricing?

One line says, "more expensive to buy and operate" then the next paragraph says "helicopters are very efficient, (snip) and costing considerably less to buy and operate".

Which is correct? Stuph 03:44, 20 August 2006 (UTC)


The first paragraph begins with "Compared to conventional fixed-wing aircraft", the next paragraphy begins with "Compared to other vertical lift aircraft". It's not a contradictition. — Soupisgoodfood 06:34, 20 August 2006 (UTC)


Error in the article in section "Controlling flight" and the truth about gyroscopic precession

cite: More lift at the rear of the rotary wing will cause the aircraft to pitch forward, an increase on the left will cause a roll to the right and so on. This is also how the helicopter is manouvred, ie. pitching forward causes forward flight.

I do not know any helicopter acting this way. There is a phase shift between the input and the reaction of approx. 90° (as mentioned in this discussion). Sometimes this effect is explained by gyroscopic precession, sometimes with an harmonic oscillator near resonance.

The first explanation you get from understanding the rotor as a rotating object, and as every rotating object gyroscopic effects occur. The question is only, if they are negligible or not. They would be negligible, if the angular momentum of the rotor is small in comparison to the torque by the cyclic (or by a gust of wind). But the angular momentum is large compared to the cyclic torque (as a quick test: compare the resulting tilt-speed to the rotational speed of the rotor). Therefore there is gyroscopic precession.

For the second explanation (harmonic oscillator near resonance) you have to set up the equation of motion for the rotor blades (or even for a single point of the blades). First let us ignore aerodynamic forces (except the lift) and consider a rotor with its flapping hinges in the rotor center. You have two forces: the lift (as a function of the angular position angle) and the centripetal force. Depending on the flapping angle, the centripetal force can be split in a part parallel to the blade and a part perpendicular to the blade. The perpendicular force acts as a restoring force and is (for small flapping angles) proportional to the flapping angle. This is the setup for an harmonic oscillator. If you calculate the resonance frequency, you get exactly the rotating frequency of the rotor, which means that the rotor is in resonance. The cyclic (and every external torque on the rotor, e. g. by a gust of wind) acts with the resonance frequency on the rotor blades. And an oscillator in resonance responses with a phase shift of 90° on torques.

Before discussing the effects of further aerodynamic forces and flapping hinges placed not in the rotor center, let us have a look on the situation so far. We have two different explanations/theories for the 90° phase shift. But which one is correct? The answer is as simple as obvious: Both! Of course! The physics behind is the same. If you see the rotor as one large rotating object or if you set up the equation of motion for every mass point, the result must be the same. In fact, both "theories" are 100% equivalent.

Let us short think about the further aerodynamic forces and flapping hinges not in the rotor center. In the oscillator explanation the further aerodynamic forces can be considered as damping-forces (as a function of the time derivation of the flapping angle), which effect the resonance frequency of the rotor (and therefore the real resonance frequency is only near to the rotating frequency of the rotor). Flapping hinges not in the rotor center result in smaller restoring forces, which effects as well the resonance frequency. But now we have a torque from the flapped blades on the rotor mast which tilts the fuselage and therefore the effective flapping hinge is more to the rotor center (consequently a helicopter (with flapping hinges outside the rotor center) has a different phase shift on ground (where the fuselage can not tilt) than in air). Therefore real rotors are not exactly in resonance and the the phase shift is not exactly 90° (For a rotor without flapping hinges, the blades them self are flexible. You can calculate with an effective hinge somewhere outside the center). If you want to use the "gyro-theory" with aerodynamic damp forces and flapping hinges outside the rotor center you have to think of a not totally free gyro. Not all torque (which acts still with a phase shift of 90°) results in a tilting of the rotor. The air and the rotor mast resist (partly) the acting torque, a "anti-torque" acts back on the rotor (in opposite direction), which again acts with a phase shift of 90°. If you add these first torque with 90° phase shift and a smaller one in opposite direction and with further 90° phase shift, you get in sum a torque acting with less than 90° phase shift (of course the second one in opposite direction with 180° phase shift will cause a third (much smaller than) torque with 270° phase shift in the original direction and so on, but if you add them all you get a phase shift smaller than 90°; you get exactly the same angle as with the "oscillator-theory"). You can see, that for calculating a rotor with consideration of aerodynamic damping forces and flapping hinges outside the rotor center (and whatever), the oscillator-ansatz is much easier to handle and therefore (as far as I know) you find only this in the textbooks. But for a quick explanation of the 90° phase shift, the gyro is more handy (I think). --Maik789 23:34, 4 November 2006 (UTC)

You make an interesting point. It would be great if the analysis for both the oscillator theory and the gyroscope theory was presented somewhere (maybe here in the talk page for now). I for one would like to see the derivations, even if they ignore some of the esoteric effects. If you are correct, then the analysis would put the debate to rest. You can't argue with math. Madhu 16:27, 7 November 2006 (UTC)


Hi! Derivation for the gyroscopic precession is not necessary, its only vector addition. But of course you can do it with classical mechanics, I will get to this point later.
1.) Let's look on a single rotor blade, the rotor is rotating. Some assumptions: The incidence is zero (no lift). The flapping hinge is in the rotor center (like Bell 206 or Robinson R22). If the flapping angle α is zero, the centripetal force is perpendicular to the rotor mast and parallel to the blade. Ignoring the gravity there is no force which would cause an changing of α.
2.) In contrary to 1.) we assume, that the blade is deflected up by the angle α. For simplification we assume all mass of the blade is concentrating in one point with the distance r to the rotor mast. The centripetal force FZ acts perpendicular to the rotor mast, but nor parallel to the blade. With the parallelogram of forces we can split this force into two components, one parallel to the blade and one perpendicular to the blade (mainly in downwards direction). The component along the blade is FZcosα, and the component perpendicular to the blade is − FZsinα. This component perpendicular to the blade is opposed to the displacement (deflection). Therefore we have an oscillator. Note: The same formula we get for a pendulum. For small displacements sinα = α, and if the force is proportional to the displacement, than we have the setup for a harmonic oscillator. The resonant frequency is \omega_{res} = \sqrt{\frac {F_Z}{rm}}. With FZ = mω2r we get for the resonant frequency ωres = ω. The rotating rotor is (for small displacements) a harmonic oscillator with a resonant frequency, which is equal to the rotational frequency! An oscillator in resonance has a phase shift of 90° between force and reaction. (Note: the simplification, that the mass of the blade is concentrated on one point, is not necessary. Indeed you can do this calculation for every point of the rotor. And if you get the same behavior for every point of the blade, than you get the same for the whole rotor.)
How does this deal with a gyro? Very simple: This derivation is nothing else than the derivation of the gyroscopic precession with the classical mechanic. Not surprising, independent if you look on a gyro as a whole, or if you derive the equation of motion for every point of a gyro, you always get the same result, as always the same physic is valid. (You can replace gyro by rotor in the last sentence). --Maik789 20:48, 7 November 2006 (UTC)