# Why hasn't helicopter control methods improved? **URL:** \ **Category:** Factual Questions\ **Created:** [September 23, 2004, 3:59pm UTC](https://boards.straightdope.com/t/why-hasnt-helicopter-control-methods-improved/265694 "2004-09-23T15:59:19Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [September 25, 2004, 1:50pm UTC](https://boards.straightdope.com/t/why-hasnt-helicopter-control-methods-improved/265694/41 "2004-09-25T13:50:39Z")
**KP** : That looks like the clip I remember. Do you know if it’s from SoCal? The helicopter is the same, and the detail that the guy just bought it is the same. Thanks for the link. ---
**Author:** ![Hail\_Ants](https://avatars.discourse-cdn.com/v4/letter/h/dc4da7/32.png) [@Hail\_Ants](https://boards.straightdope.com/u/Hail_Ants)\ **Post date:** [September 25, 2004, 2:28pm UTC](https://boards.straightdope.com/t/why-hasnt-helicopter-control-methods-improved/265694/42 "2004-09-25T14:28:10Z")
KP, amazing clip! Wow was that guy lucky (and an idiot). > [@BobLibDem](#): > > It’s been a movie staple that persons with no apparent training can hop into a helicopter and take off with it. The movie staple where the pilot of even _a fixed wing aircraft_ has a heart attack and a passenger makes a shakey but survivable landing is not very accurate. With no flight training a person would basically try to fly a plane the way you drive a car. And if you do that you’d crash. Pretty quickly. > [@Johnny LA](#): > > In a helicopter with a semi-rigid rotor system (like a Robinson R-22 or a Bell JetRanger) this would unload the rotor disc creating a negative-G situation. This could cause “mast bumping” that might cause the rotor system to depart the aircraft. It could also result in a “boom chop” that severs the tail boom. [Here’s a clip of what can happen if you pull back too much.](http://images.military.com/Shock/0,,SA_HeloMishap_090104,00.html) ---
**Author:** ![Broomstick](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/broomstick/32/246_2.png) [@Broomstick](https://boards.straightdope.com/u/Broomstick)\ **Post date:** [September 26, 2004, 10:38am UTC](https://boards.straightdope.com/t/why-hasnt-helicopter-control-methods-improved/265694/43 "2004-09-26T10:38:40Z")
> [@Hail Ants](#): > > The movie staple where the pilot of even _a fixed wing aircraft_ has a heart attack and a passenger makes a shakey but survivable landing is not very accurate. With no flight training a person would basically try to fly a plane the way you drive a car. And if you do that you’d crash. Pretty quickly. Except that untrained people _have_ been “talked down” to a survivable landing in fixed wing airplanes on a few occassions - they almost always do damage to the airplane, I will concede that. I dunno, maybe you count someone coaching them over the radio as “training”. If a fixed wing airplane was trimmed up properly and in cruise and the pilot checked out, as long as he/she didn’t slump forward onto the controls, the plane would have a very strong tendency to keep going at the same speed, altitude, and heading for at least a few minutes, and possibly quite a long while if the atmophere was calm - giving a hypothetical passenger time to use the radio, call for help, and receive instructions. Maintaining altitude-heading-speed is relatively simple… it’s the landing that’s the hardest part. But people have done it. On the other hand, as I understand it, helicoptors require _constant_ inputs. If this hypothetical situation occured the passenger _would not have time_ to call for help or figure out anything for him/herself. Which is probably why _no one_ has ever been “talked down” in a helicoptor. It’s difficult with a fixed-wing - impossible with a fling-wing. Which sort of makes me wonder how Sikorsky managed to learn how to fly his invention without killing himself… I presume it was a LOT of pre-flight pondering and taking things extremely slowly. ---
**Author:** ![Fuji\_Kitakyusho](https://avatars.discourse-cdn.com/v4/letter/f/f0a364/32.png) [@Fuji\_Kitakyusho](https://boards.straightdope.com/u/Fuji_Kitakyusho)\ **Post date:** [September 26, 2004, 7:28pm UTC](https://boards.straightdope.com/t/why-hasnt-helicopter-control-methods-improved/265694/44 "2004-09-26T19:28:25Z")
What is the purpose or advantage of the lead/lag relationship between blades? ---
**Author:** ![W.Fikere\_Tomba](https://avatars.discourse-cdn.com/v4/letter/w/f9ae1b/32.png) [@W.Fikere\_Tomba](https://boards.straightdope.com/u/W.Fikere_Tomba)\ **Post date:** [September 26, 2004, 7:53pm UTC](https://boards.straightdope.com/t/why-hasnt-helicopter-control-methods-improved/265694/45 "2004-09-26T19:53:13Z")
> [@Broomstick](#): > > Which sort of makes me wonder how Sikorsky managed to learn how to fly his invention without killing himself… I presume it was a LOT of pre-flight pondering and taking things extremely slowly. Well, he wasn’t the first person to work on experimental helicopters, so I don’t think he was making it all up from scratch. But [this page](http://www.vectorsite.net/avheli2.html) describes his process a bit, and mentions that in the earliest tests, the helicopter was tethered to the ground. It also says there were “a number of accidents, most seriously a crash on 14 October 1940 that damaged the machine, though Sikorsky was unhurt.” ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [September 26, 2004, 9:10pm UTC](https://boards.straightdope.com/t/why-hasnt-helicopter-control-methods-improved/265694/46 "2004-09-26T21:10:46Z")
> [@](#): > > What is the purpose or advantage of the lead/lag relationship between blades? When a blade “flaps” is it subject to the Coriolis Effect. That is, when the edges of a rotating mass get closer to the centre of rotation, they speed up. The classic example is the ice skater who is spinning with her arms extended. When she brings her arms in toward her chest, the speed of her rotation increases. On a multi-bladed rotor system the blades flap individually; not as a unit. Thus, there is always one blade that is trying to fly faster than the others and another that is trying to fly slower. The lead-lag hinges allow the blades to speed up and slow down individually to compensate for the Coriolis Effect. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [September 26, 2004, 9:16pm UTC](https://boards.straightdope.com/t/why-hasnt-helicopter-control-methods-improved/265694/47 "2004-09-26T21:16:33Z")
Actually, a semi-rigid rotor system would also be subject to Coriolis; so my “flapping as a unit” statement isn’t really accurate. Also, why would a blade tip get closer to the hub? The reason why the blade tips get closer to the hub is because they are moving upward. When the blades are “coning” (as they do when they are supporting the weight of the aircraft) they move in the same amount, so Coriolis doesn’t apply. But in directional flight you’ll have a blade that is higher than the plane of rotation. Since the blade doesn’t change its length, the tip gets closer to the hub as the blade rises. Semi-rigid rotors are “underslung” (mounted lower than the centre of the hub) to minimise Coriolis. ---
**Author:** ![Princhester](https://avatars.discourse-cdn.com/v4/letter/p/3e96dc/32.png) [@Princhester](https://boards.straightdope.com/u/Princhester)\ **Post date:** [September 27, 2004, 12:10am UTC](https://boards.straightdope.com/t/why-hasnt-helicopter-control-methods-improved/265694/48 "2004-09-27T00:10:12Z")
> [@KP](#): > > WNBC (NYC Channel 4) had [a harrowing crash](http://www.alexisparkinn.com/photogallery/Videos/Ecureuil%20crash%20brooklyn%20tail%20rotor%20failure.mpeg) in May that brought back (to me, anyway) memories of what it was like to recover after “losing it” for even a few seconds. This was an experienced pilot, who flew that particular helicopter daily (Amazingly, there were no fatalities!) Do you know what happened there? The chopper seems to be careering all over the place. Was there some sort of failure that the pilot was desperately trying to work around? Or was it just a case (as you seem to imply) of him losing it for a moment and then having incredible difficulty getting it back? ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [September 27, 2004, 1:21am UTC](https://boards.straightdope.com/t/why-hasnt-helicopter-control-methods-improved/265694/49 "2004-09-27T01:21:03Z")
> [@](#): > > Do you know what happened there? The chopper seems to be careering all over the place. It’s hard to tell, but I’ll make a guess. It could be that the helicopter suffered a power failure and entered autorotation. Note that the helicopter seems to be stabilised in the early part of the video. It _does_ seem to be in a severe nose-down attitude at the very beginning, but once it gets over the buildings it’s stable. Next, you can see it flare. Looks like a typical autorotation landing as every pilot does over and over and over again in training. (Private pilots don’t do it to touchdown, but recover into a hover. Otherwise the emergency procedure is identical, and is practised until it’s second-nature. There are also “hovering autorotations” that are practised, and an autorotation-to-touchdown is basically a merging of the two techniques.) Then the helicopter banks left. Why? One possibility is that the pilot was trying to land on a rooftop or on the street next to the building. But then he loses control. What would cause that? The urge to pull up on the collective to cushion the “landing”, even though the pilot _knows_ he still needs to conserve his rotor RPM? Let’s back up a little. Suppose there _wasn’t_ a power failure, but a failure of the anti-torque rotor (“loss of tail rotor”, or LOTR). In this case, the pilot would no longer be able to counteract torque. His only option is to remove the torque – that is, to chop the power. The approach would look just like a normal autorotaion. If the pilot pulled up on the collective to cushion the landing without holding off the power, then the helicopter would spin left – which is to be seen in the video. Except… Except the Ecureuil is a _French_ helicopter. French and Russian helicopters’ rotor blades turn _clockwise_. If LOTR occured, then the helicopter should have yawed _right_. And I don’t think the throttles in jet helicopters works the same way as in piston ones. Would raising the collective without “holding the throttle off” add power? It _looks_ like an autorotation gone wrong. Was it a power loss? If so, then why does the helicopter appear to have some power available at the very end? Was it LOTR? If so, then why does a French helicopter turn _left?_ Was the pilot aiming for a certain landing spot, then tried to abort for some reason we can’t see on the video? Kids in the street, or something? **KD** : If you have any information, please let us know. ---
**Author:** ![KP](https://avatars.discourse-cdn.com/v4/letter/k/a9adbd/32.png) [@KP](https://boards.straightdope.com/u/KP)\ **Post date:** [September 27, 2004, 3:02am UTC](https://boards.straightdope.com/t/why-hasnt-helicopter-control-methods-improved/265694/50 "2004-09-27T03:02:22Z")
> [@Princhester](#): > > Was there some sort of failure that the pilot was desperately trying to work around? Or was it just a case (as you seem to imply) of him losing it for a moment and then having incredible difficulty getting it back? I linked that WNBC crash video because, it brought back memories of some scary moments in my own helo lessons. It was meant to convey a visceral impression, not make any factual assertions. Though I’d had a few sweaty moments of intense concentration in my fixed-wing training, it was a breeze compared to helo (for me, at least) and I didn’t think words would do the experience justice. I don’t know about the power loss, but the pilot had apparently reported a tail rotor failure to Kennedy Air Traffic Control minutes before the video. That model, the Aerospatiale AS-350BA, does have something fo a history of tail rotor failures, and has had at least 9 airworthiness directives since 1978 [an airworthiness directive is a warning, usually with repairs or checks that should be made, or changes to preflight procedure, etc.] I’m not aware if the preliminary NTSB report was released, or even if an investigation was made, given that no one was hurt. My impressions generally agreed with Johnny LA’s (I almost called him J.LA - but that sounds like J.LO with wings). By searching for “Ross Mowry” and helicopter (the pilot) I was able to find a couple of interviews that didn’t add much, but confirm J.LA’s scenario. [Here’s one](http://msnbc.msn.com/id/4945202/) (scroll about halfway down). He does say that he was aiming for that chimney, to arrest his forward motion. ---
**Author:** ![Princhester](https://avatars.discourse-cdn.com/v4/letter/p/3e96dc/32.png) [@Princhester](https://boards.straightdope.com/u/Princhester)\ **Post date:** [September 27, 2004, 5:54am UTC](https://boards.straightdope.com/t/why-hasnt-helicopter-control-methods-improved/265694/51 "2004-09-27T05:54:34Z")
What would cause a severe nose down? It’s not intuitive to me that loss of tail or main rotor power would cause a pitch problem. But then I suppose nuthin’s straightforward when it comes to helicopter control. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [September 27, 2004, 12:33pm UTC](https://boards.straightdope.com/t/why-hasnt-helicopter-control-methods-improved/265694/52 "2004-09-27T12:33:04Z")
> [@](#): > > What would cause a severe nose down? It’s not intuitive to me that loss of tail or main rotor power would cause a pitch problem. Just read the article. The pilot said he was in a hover. When he lost his tail rotor the first thing he would have done was chop the power and lower the collective. When you lose your power, you want to conserve your rotor RPM. At loss of power, the Sprague clutch (free wheeling unit) disconnects the rotor system from the engine. Because of the shape of the rotors, the uprushing air during the descent creates a “driving section” on the blades. That is, the aerodynamic forces pull that part of the blade forward. There’s probably a diagram od the “driving section” and “driven section” on the 'net, but I haven’t had coffee yet. In any case, as long as you have altitude and maintain your airspeed you have rotor RPM. In a hover, you don’t have the forward airspeed to keep the rotor turning, but you do have the inertia of the blades. As long as you lower the collective immediately, you’ll have enough energy to have some control until you gain forward airspeed. You get the forward airspeed by diving. Once you have your glide speed you can level out and prepare for the landing, as can be seen in the video. Helicopter operating manuals (POH) have the [height-velocity diagram](http://www.tpub.com/content/ahapache/TM-1-1520-236-10/css/TM-1-1520-236-10_318.htm) or “dead man’s curve”. The one I linked has a “caution” range, but the ones I use just have the “safe” and “avoid” sections. The V-H diagram shows the envelope in which you can perform a safe autorotation in case of a power failure. Basically, if you are slow (like in a hover) you want to be high. In the linked chart, you can perform a safe autorotation from hover if you’re above 760 feet AGL or below 20 feet AGL. So the pilot was in a hover, and his altitude was within the envelope. When he lost the tail rotor he chopped power. He entered a dive to build airspeed to preserve his rotor RPM. When he neared landing, he pulled back on the cyclic to reduce the speed of his descent (trading RPM for a lower descent rate) and lowered the collective to prevent overspeed followed by a rapid reduction in RPM. ---
**Author:** ![igloorex](https://avatars.discourse-cdn.com/v4/letter/i/858c86/32.png) [@igloorex](https://boards.straightdope.com/u/igloorex)\ **Post date:** [September 27, 2004, 3:36pm UTC](https://boards.straightdope.com/t/why-hasnt-helicopter-control-methods-improved/265694/53 "2004-09-27T15:36:00Z")
Looks to me like a loss of tail rotor, but with a failure to secure the engine. The inital aggressive nose down is to gain some forward airspeed so there’s some room to flare the nose, trade airspeed to slow rate of descent and cushion the landing. So far, so good. At this point, the helo wouldn’t be spinning out of control, because this maneuver is done without power on the rotor head (no torque = no need for anti-torque) aka “collective full down.” It looks to me like the pilot failed to secure the engine. After the initial nose down, the aircraft goes into a slight nose up as the flare and prep for landing begins. At this point, the pilot would normally be starting to add collective as well. In an unpowered condition, this would slow down the rotor head, but would not increase torque (again no need for anti-torque and the helo would not spin). If power is not secured, the engine increases torque to keep the rotor turning at a constant speed, thus creating torque, and therefore creating the need for anti-torque. In this video, the helo gradually begins spinning again as it finishes its flare (when the pilot normally pulls up on the collective). There is no apparent slowing of the main rotor in the video until impact, and the helo glides for much longer in the flare than I would expect in a power off auto (though this is much lighter helo than the one I fly and probably has a better glide). So, while it’s hard to say based only on the grainy video, my opinion is loss of T/R with a failure to secure the engine. BTW - thanks **Johnny LA** - I was really puzzled by the video until you pointed out that the helo is French. Now it makes sense to me. ---
**Author:** ![The\_Controvert](https://avatars.discourse-cdn.com/v4/letter/t/dec6dc/32.png) [@The\_Controvert](https://boards.straightdope.com/u/The_Controvert)\ **Post date:** [September 27, 2004, 3:58pm UTC](https://boards.straightdope.com/t/why-hasnt-helicopter-control-methods-improved/265694/54 "2004-09-27T15:58:04Z")
It hasn’t? [http://www.airscooter.com/pages/airscooter\_main.htm](http://www.airscooter.com/pages/airscooter_main.htm) > [@](#): > > By eliminating the need and complexity of swashplates, collective and cyclic control through a coaxial rotor design a number of benefits beyond conventional helicopter designs are immediately realized. First; enhanced, intuitive flight controls are achieved by simple motorcycle-style handlebars and the absence of a tail rotor. To gain altitude, simply throttle up like you would on a motorcycle, turn left or right on the handlebars for craft rotation and move the handlebar assembly as a joystick for directional control (including reverse). No pedal controls are necessary, which means someone without the use of their legs can just as easily fly the AirScooter. Handlebar controls represent the most distinguishable feature of the AirScooter. AirScooter’s patented design also provides an amazing level of stability while in the air and during flight. ---
**Author:** ![Princhester](https://avatars.discourse-cdn.com/v4/letter/p/3e96dc/32.png) [@Princhester](https://boards.straightdope.com/u/Princhester)\ **Post date:** [September 27, 2004, 11:35pm UTC](https://boards.straightdope.com/t/why-hasnt-helicopter-control-methods-improved/265694/55 "2004-09-27T23:35:37Z")
I did read the article, Johnny, it’s just that the pilot said “Next thing I know, I was just pointing straight down.” He made it sound like this wasn’t as a result of something he did, but rather something that happened without his input. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [September 28, 2004, 12:20am UTC](https://boards.straightdope.com/t/why-hasnt-helicopter-control-methods-improved/265694/56 "2004-09-28T00:20:59Z")
> [@](#): > > Just read the article. Followed by… > [@](#): > > I did read the article, Johnny :smack: I didn’t realise as I typed, that “Just read the article” could be read as an order to _read_ the article instead of my intention of saying that I _had read_ the article. My bad. In any case, if you lose power in a high hover (whether through malfunction or by lowering the cyclic) you need to get the nose down to get the necessary airspeed. > [@](#): > > BTW - thanks **Johnny LA** - I was really puzzled by the video until you pointed out that the helo is French. Now it makes sense to me. I was thinking that the (French) helicopter should have yawed the other way; but now that I think of it, it should have yawed the way it did. (I’ve never lost a tail rotor.) ---
**Author:** ![SenorBeef](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senorbeef/32/2220_2.png) [@SenorBeef](https://boards.straightdope.com/u/SenorBeef)\ **Post date:** [September 28, 2004, 2:37am UTC](https://boards.straightdope.com/t/why-hasnt-helicopter-control-methods-improved/265694/57 "2004-09-28T02:37:37Z")
> [@Johnny L.A.](#): > > In any case, if you lose power in a high hover (whether through malfunction or by lowering the cyclic) … You mean collective, right? Just making sure my understanding is correct. ---
**Author:** ![igloorex](https://avatars.discourse-cdn.com/v4/letter/i/858c86/32.png) [@igloorex](https://boards.straightdope.com/u/igloorex)\ **Post date:** [September 28, 2004, 4:44am UTC](https://boards.straightdope.com/t/why-hasnt-helicopter-control-methods-improved/265694/58 "2004-09-28T04:44:04Z")
**SenorBeef** , you are correct. For power loss in a helo in a high hover, you need to lower the _collective_ full down immediately and push forward _cyclic_. Lowering the collective prevents catastrophic decay of rotor speed and begins the autorotation. Pushing the cyclic forward increases forward airspeed. In the case of a loss of tail rotor, lowering the collective also removes torque from the main rotor, which should stop the helo from swapping ends. In any event, a high hover is pretty much the worst place a helo can lose power. Even with immediate and correct action by the pilot, odds of survival are pretty grim. It varies much by helo, but above 40’ or so and below 500’ you’re pretty much going to make a big smoking hole. (less than 40’ you might be able to cushion, more than 500’ you might be able to get enough forward speed to salvage an auto) ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [September 28, 2004, 12:04pm UTC](https://boards.straightdope.com/t/why-hasnt-helicopter-control-methods-improved/265694/59 "2004-09-28T12:04:58Z")
> [@](#): > > You mean collective, right? Just making sure my understanding is correct. Yes. I mis-typed. ---
**Author:** ![flight](https://avatars.discourse-cdn.com/v4/letter/f/bbce88/32.png) [@flight](https://boards.straightdope.com/u/flight)\ **Post date:** [September 28, 2004, 2:11pm UTC](https://boards.straightdope.com/t/why-hasnt-helicopter-control-methods-improved/265694/60 "2004-09-28T14:11:22Z")
Earlier I mentioned something erroneous about rigid rotor systems. Sorry, I was talking about REALLY rigid rotor systems, the kind that are being proposed where the blade actually stops and acts as a wing in forward flight. That airscooter thing is very interesting. There are several helicopters that have eliminated the need for an anti-torque device (tail rotor) by going with tandem (not necessarily co-axial) rotors. You control relative power or collective to the two rotors to control rotation. They still need some form of cyclic though for directional control. This apparently does not. They never give a firm description of how they get around this as they seem to believe it is a big secret that they are getting several patents for. They do make mention of it here though: > [@](#): > > AirScooter employs a hinged or pendulum effect allowing tilt between the transmission/rotor system and the rest of the craft. So basically they control the CG location to create a moment. This tilts the aircraft (much like a hang glider) which changes the direction of the thrust vector. I am surprised if they will get their patents as we played around with concepts like this as undergrads. I would hope someone had patented it by now, or at least considered it in the public domain. There are several problems with their design: 1. Control authority is dependent upon gross weight. Since you are controlling the helicopter by moving the CG, and how much it will move is entirely dependent upon the amount and distribution of weight, the helicopter will not only fly differently for different pilots, it will fly differently over the course of a single flight as gas is consumed. They appear to have attempted to compensate for the pilot by including what looks to me like a balast weight in a container sticking out the front, you probably fill this to different levels for different pilots. They have also apparently tried to locate the gas tank at the CG, and though this will prevent some changes in control, it will not prevent all. This is not an overwhelming problem though, and can be overcome. 2)Innefficiency Though they tout the efficiency of the aircraft, not changing the pitch of the blade around the azimuth in forward flight is very inefficient and likely will greatly limit range. 3)Forward speed They say they can get 60mph out of it, but I would be surprised. How fast you go depends on how far you can move the CG from the axis of rotation. It doesn’t look like they could get as much motion as they would need to overcome drag, and their efficiency will plummet as they move faster. Helicopters reach their best efficiency at a moderate forward speed, but I am not even sure that would be the case for this craft. 3)Safety If you cannot control pitch, you cannot autorotate. If you lose power you are dead. 4)Vibration and flapping response I do not have time now to finish, but it will have a lot of vibration and the flapping will result in worse efficiency in forward flight. None of these problems are insurmountable (except maybe the death thing) for a small recreational vehicle, but they describe why they are not used on full-scale or even RC helicopters (you wouldn’t be able to do a tenth of the cool stuff you can currently do with RC on one of these). [Previous page](https://boards.straightdope.com/t/why-hasnt-helicopter-control-methods-improved/265694.md?page=2) [Next page](https://boards.straightdope.com/t/why-hasnt-helicopter-control-methods-improved/265694.md?page=4)