# Could they design helicopters based on drones? **URL:** \ **Category:** Factual Questions\ **Created:** [May 9, 2017, 4:10am UTC](https://boards.straightdope.com/t/could-they-design-helicopters-based-on-drones/786180 "2017-05-09T04:10:17Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [May 10, 2017, 1:32am UTC](https://boards.straightdope.com/t/could-they-design-helicopters-based-on-drones/786180/21 "2017-05-10T01:32:20Z")
AFAIK the only production airplanes with thrust vectoring are military fighter jets. Tiltrotors such as the V-22 are arguably “thrust vectoring”. They certainly have mechanisms to alter the vector of engine power delivery. There are doubtless more oddball cases in the range of homebuilts, prototypes, proof of concept subscale models, etc. ---
**Author:** ![JHBoom](https://avatars.discourse-cdn.com/v4/letter/j/13edae/32.png) [@JHBoom](https://boards.straightdope.com/u/JHBoom)\ **Post date:** [May 10, 2017, 1:41am UTC](https://boards.straightdope.com/t/could-they-design-helicopters-based-on-drones/786180/22 "2017-05-10T01:41:44Z")
> [@Leo\_Bloom](#): > > Do only military jets (or fighters only?) have thrust vectoring right off the assembly line? The F-22, F-35B, and AV-8 (Harrier) all have thrust vectoring capability as standard equipment. TV provides STOVL capability for the F-35B and Harrier, and increased pitch authority for the F-22. ---
**Author:** ![Robot\_Arm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robot_arm/32/18280_2.png) [@Robot\_Arm](https://boards.straightdope.com/u/Robot_Arm)\ **Post date:** [May 10, 2017, 2:55am UTC](https://boards.straightdope.com/t/could-they-design-helicopters-based-on-drones/786180/23 "2017-05-10T02:55:38Z")
> [@LSLGuy](#): > > AFAIK the only production airplanes with thrust vectoring are military fighter jets. > > Tiltrotors such as the V-22 are arguably “thrust vectoring”. They certainly have mechanisms to alter the vector of engine power delivery. > > There are doubtless more oddball cases in the range of homebuilts, prototypes, proof of concept subscale models, etc. Does [this](http://sydneyparagliding.com/wp-content/uploads/2012/06/Sydney-Paragliding-Paramotors.jpg) count as thrust vectoring? ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [May 10, 2017, 12:33pm UTC](https://boards.straightdope.com/t/could-they-design-helicopters-based-on-drones/786180/24 "2017-05-10T12:33:09Z")
Good point. Sorta. As I almost said about the V-22, if the term “thrust vectoring” is to have any meaning, we need to keep it fairly narrow. After all, any ordinary airplane can alter the thrust vector versus the horizon simply by raising or lowering the nose. The thrust vector remains aligned with the aircraft, but not the horizon. In the case of powered parachutes, my reading of the FAA’s piloting manual for them ([http://www.faa.gov/regulations\_policies/handbooks\_manuals/aviation/media/powered\_parachute\_handbook.pdf](http://www.faa.gov/regulations_policies/handbooks_manuals/aviation/media/powered_parachute_handbook.pdf) (60MB PDF)) says that they fly at a fixed AOA and hence fixed speed. From steady state cruise, increasing power produces first a pendulum motion of the car forward hence nose up. Which a moment later translates into increased AOA & lift. Which a moment later translates into upward motion of the whole vehicle, a reduction in AOA back to steady state and a hence a re-alignment of the car with the overall vehicle motion. So thrust “vectors” instantaneously as a means of control but very quickly washes out and amounts to the same thing as an ordinary airplane: you can alter the thrust line versus the horizon, but not versus the vehicle. So I choose to define “thrust vectoring” narrowly: The ability to alter the thrust line versus the vehicle to a material degree for purposes of control or direct lift. In fact we could (should?) make pretty strong decision to separate that into the narrower enhanced control class, e.g. F-22, and the wider direct lift class, e.g. AV-8 & F-35B. I’d also argue against including rotorcraft in the “vectored thrust” category. Even the V-22. Also for reasons of not muddying the definition into uselessness. A rotor in any forward flight has a more complex interaction with the airstream than simply being a fan pushing air parallel to its rotational axis. To each his/her own; I’m certainly not the Minister of Definitions on this one. ---
**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:** [May 10, 2017, 2:09pm UTC](https://boards.straightdope.com/t/could-they-design-helicopters-based-on-drones/786180/25 "2017-05-10T14:09:06Z")
Aside: Yesterday was the first time I saw a V-22 ‘in the wild’. It was taking off from Boeing Field. ---
**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:** [May 10, 2017, 2:16pm UTC](https://boards.straightdope.com/t/could-they-design-helicopters-based-on-drones/786180/26 "2017-05-10T14:16:13Z")
> [@SamuelA](#): > > 1. Note that after leaving ground effect in a vertical ascent on a helicopter is probably peak engine stress. If you’re going to have an engine failure, it’s quite possible it happens then. That’s why they have the HV diagram, and why we’re trained to remain within the envelope. But we’re also trained to operate outside of the HV envelope with the understanding that it is a calculated risk, because there are situations where operating within the ‘dead man’s curve’ is necessary. Yes, hovering OGE at low altitude puts you in a risky situation; but the likelihood of a total engine failure is remote. > [@SamuelA](#): > > 1. We aren’t really talking about quad-helicopters. We are talking about copters with a \*lot \*of propellers driven by individual electric motors. What you are saying would be handled with a mesh of electric connections, where each motor has access to an electrical bus that is subdivided into sections across the battery pack. Protective switches of some type would activate automatically to isolate sections of the battery pack with too low or too high a bus voltage, so that the other motors still have power. (so a fire or other sudden battery failure would in theory only cause power loss to a couple of the motors. An isolation switch failure would still limit power loss to a small number of the motors) > > Electrical redundancy like this can be better (and much cheaper) than a method using mechanical driveshafts. So how do you supply power to the rotor on the failed motor? You’re going to want that, unless you have redundant rotors in every position. ---
**Author:** ![joema](https://avatars.discourse-cdn.com/v4/letter/j/a9adbd/32.png) [@joema](https://boards.straightdope.com/u/joema)\ **Post date:** [May 10, 2017, 2:19pm UTC](https://boards.straightdope.com/t/could-they-design-helicopters-based-on-drones/786180/27 "2017-05-10T14:19:37Z")
> [@LSLGuy](#): > > AFAIK the only production airplanes with thrust vectoring are military fighter jets. > > Tiltrotors such as the V-22 are arguably “thrust vectoring”. They certainly have mechanisms to alter the vector of engine power delivery… It’s not quite in production yet but the civilian AgustaWestland AW609 should reach certification next year: > **[Everything You Need To Know About The First Civilian Tilt Rotor Aircraft](https://jalopnik.com/everything-you-need-to-know-about-the-first-civilian-ti-1689618757)** > > The V-22 Osprey has dominated the rotary wing, vertical take-off market for years, but its only available to the military. Now, AgustaWestland is on pace to begin production of the AW609, the first civilian tilt-rotor, at its plant in Philadelphia... > **[AW609 tiltrotor climbs towards 2018 certification](https://newatlas.com/aw609-tiltrotor-icing-trials/48015/)** > > It's been a long road for the AgustaWestland AW609. Since the resumption of flight testing in April last year following a fatal air crash in 2015 that claimed the lives of two test pilots, the third tiltrotor prototype carried out several weeks of... ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [May 10, 2017, 2:50pm UTC](https://boards.straightdope.com/t/could-they-design-helicopters-based-on-drones/786180/28 "2017-05-10T14:50:41Z")
Hence my “such as”. The current V-22 is neither the first, last, nor only tiltrotor in history. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [May 10, 2017, 2:53pm UTC](https://boards.straightdope.com/t/could-they-design-helicopters-based-on-drones/786180/29 "2017-05-10T14:53:18Z")
> [@Johnny\_L.A](#): > > That’s why they have the HV diagram, and why we’re trained to remain within the envelope. But we’re also trained to operate outside of the HV envelope with the understanding that it is a calculated risk, because there are situations where operating within the ‘dead man’s curve’ is necessary. Yes, hovering OGE at low altitude puts you in a risky situation; but the likelihood of a total engine failure is remote. > > So how do you supply power to the rotor on the failed motor? You’re going to want that, unless you have redundant rotors in every position. Nope. If you have enough rotors spread appropriately then any one can stop turning and you make up the control difference with differential power on the others. And you make up the difference in total power required by bumping the output of all of them. Think cyclic and collective. But cyclic control is achieved by altering the thrust of the various other lift rotors, not by tilting their thrust plane. ---
**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:** [May 10, 2017, 3:00pm UTC](https://boards.straightdope.com/t/could-they-design-helicopters-based-on-drones/786180/30 "2017-05-10T15:00:36Z")
> [@LSLGuy](#): > > If you have enough rotors spread appropriately then any one can stop turning and you make up the control difference with differential power on the others. And you make up the difference in total power required by bumping the output of all of them. Then what is the minimum number of rotors needed, such that the failure of one or more of them may be compensated for by the remaining rotors, and what layout would allow the failure of one or more rotors, such that the aircraft can be held in a hover? ---
**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:** [May 10, 2017, 3:31pm UTC](https://boards.straightdope.com/t/could-they-design-helicopters-based-on-drones/786180/31 "2017-05-10T15:31:15Z")
Let me give an example. Suppose you have a hexagonal platform with motor 1 at 11:00, motor 2 at 1:00, and the others at 3:00, 5:00, 7:00, and 9:00. Motor 1 fails. You’d need to cut motor 2, or else the 11:00 corner would descend. So now you’re flying on four motors, but the aircraft is balanced. What happens if you lose another motor? Additionally, what happens when (not if) you lose all power? You can’t autorotate with fixed-pitch propellers. Even if you can vary the pitch, I think they would be too small for [autorotation](http://www.dynamicflight.com/aerodynamics/autos/). Of course the aircraft could be (or would have to be) equipped with a full aircraft recovery ballistic parachute system. But that’s a last resort in fixed wing aircraft, which can glide without power, and not an option on helicopters, which can autorotate. ---
**Author:** ![Chisquirrel](https://avatars.discourse-cdn.com/v4/letter/c/6bbea6/32.png) [@Chisquirrel](https://boards.straightdope.com/u/Chisquirrel)\ **Post date:** [May 10, 2017, 4:24pm UTC](https://boards.straightdope.com/t/could-they-design-helicopters-based-on-drones/786180/32 "2017-05-10T16:24:43Z")
> [@Johnny\_L.A](#): > > Let me give an example. Suppose you have a hexagonal platform with motor 1 at 11:00, motor 2 at 1:00, and the others at 3:00, 5:00, 7:00, and 9:00. Motor 1 fails. You’d need to cut motor 2, or else the 11:00 corner would descend. So now you’re flying on four motors, but the aircraft is balanced. What happens if you lose another motor? > > Additionally, what happens when (not if) you lose all power? You can’t autorotate with fixed-pitch propellers. Even if you can vary the pitch, I think they would be too small for [autorotation](http://www.dynamicflight.com/aerodynamics/autos/). Of course the aircraft could be (or would have to be) equipped with a full aircraft recovery ballistic parachute system. But that’s a last resort in fixed wing aircraft, which can glide without power, and not an option on helicopters, which can autorotate. Motors at 1:00 and 9:00 increase power, motor at 5:00 decreases, all relatively. Average motor is boosted by 20%. The goal is not to finish the flight, but to get to the ground in one piece. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [May 10, 2017, 5:00pm UTC](https://boards.straightdope.com/t/could-they-design-helicopters-based-on-drones/786180/33 "2017-05-10T17:00:25Z")
Johnny: As \*\*Chisquirrel \*\*says. All that matters is the centroid of lift be in the middle and the total be enough. Naturally there are failure modes that can overwhelm any redundant system. The certification FARs say you have to achieve 1:1 million or whatever odds of a catastrophic failure. You can do that with redundancy, reliability, or some of each. A twin-pac turbine engine is an example of the former. A very strong and carefully inspected “Jesus nut” is an example of the latter. The goal is not to design a vehicle that can’t possibly catastrophically fail. Every vehicle we’ve ever built fails at that standard. The goal is one that catastrophically fails rarely enough that the risk is _acceptable_. Just as you said about hovering within the no-autorotate zone: it’s safe \*enough \*when done infrequently _enough_. The more you install redundancy the less reliable the individual parts need to be. A twin engine aircraft needs highly reliable engines. An aircraft with 1000 engines that can stay airborne with just 800 running could have individual engines that are far less reliable than the twin and still work. The entire debate about all this stuff is how much redundancy is enough and how much faith do we put in calculations about non-interdependence between failure modes given that we don’t yet have the millions of hours of real world experience we already have with existing tech. One of the challenges here is social. And applies to many other things, including self-driving cars and solar power. The public and society and legal precedent has very high expectations based on the current highly mature state of highly mature tech. We are therefore far less tolerant of the teething pains inherent in revolutionary new tech. So our new, new tech must burst on the scene as safe as, and cheaper than, the current state of the art in current tech. Imagine that early aircraft had had to be safer than trains before they were accepted under the safety regs and also had to be both roomier and cheaper than trains before they were accepted in the marketplace. That’s a very tall order that early aircraft utterly failed at. It’ll be interesting to see how this effort at distributed propulsion rotorcraft goes. NASA is working on a X-airplane with 18 propellers, 9 on each wing. See [http://aviationweek.com/commercial-aviation/nasa-plans-tests-distributed-electric-propulsion](http://aviationweek.com/commercial-aviation/nasa-plans-tests-distributed-electric-propulsion) (maybe paywalled) and [NASA X-57 Maxwell - Wikipedia](https://en.wikipedia.org/wiki/NASA_X-57_Maxwell). See also [NASA GL-10 Greased Lightning - Wikipedia](https://en.wikipedia.org/wiki/NASA_GL-10_Greased_Lightning) for an X-rotocraft with 10 prop-rotors. With current computing we see thousands of small computers harnessed together instead of one big powerful one. Will we one day see aircraft with dozens or hundreds of power sources and thrust units? Perhaps. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [May 19, 2017, 7:03pm UTC](https://boards.straightdope.com/t/could-they-design-helicopters-based-on-drones/786180/34 "2017-05-19T19:03:36Z")
In response to this DARPA project [VTOL X-Plane - Wikipedia](https://en.wikipedia.org/wiki/VTOL_X-Plane) these guys [Aurora Flight Sciences - Wikipedia](https://en.wikipedia.org/wiki/Aurora_Flight_Sciences) have been working on some novel inventions. Like this: [http://www.aurora.aero/evtol/](http://www.aurora.aero/evtol/). This is a vid of what they’re working on that starts out with CGI of a full-scale product then transitions to real vid of real, albeit sub-scale experiments: [Aurora Flight Sciences' Electric VTOL Aircraft - YouTube](https://www.youtube.com/watch?v=BSFVvhQP7ws) This: [Programs - Aurora Flight Sciences](http://www.aurora.aero/lightningstrike/) is a different idea. Here’s a year old vid of it hovering: [The Aurora Flight Sciences VTOL Plane | Inverse - YouTube](https://www.youtube.com/watch?v=7vxgG-Wnf-o) The trade press now says they’ve just successfully flown it from hover to forward flight and back to a hover. AFAIK there’s no public vid of this latest test yet. This stuff is coming. It will blend a lot of ideas we’ve seen in hobbyist drones into what will be full-scale cargo and people-carrying aircraft ---
**Author:** ![PastTense](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pasttense/32/14550_2.png) [@PastTense](https://boards.straightdope.com/u/PastTense)\ **Post date:** [December 23, 2024, 8:55pm UTC](https://boards.straightdope.com/t/could-they-design-helicopters-based-on-drones/786180/35 "2024-12-23T20:55:31Z")
> [@scr4](#): > > Here’s another project along the same lines: > > [Electric flying car that takes off vertically could be future of transport | Automotive industry | The Guardian](https://www.theguardian.com/business/2017/apr/21/electric-flying-car-lilium-google-uber-vtol-jet-taxi) > > Looks like 36 small electric fans, 24 of which are mounted on the wings and can be pointed down for VTOL and backwards for forward flight. Lilium has gone out of business: > **[Electric Aircraft Startup Lilium Ceases Operations, 1,000 Workers Laid Off -...](https://tech.slashdot.org/story/24/12/23/186213/electric-aircraft-startup-lilium-ceases-operations-1000-workers-laid-off)** > > Lilium, once a darling in the nascent industry of electric aircraft that raised more than $1 billion before going public, has ceased operations and laid off about 1,000 workers after efforts to gain financing and exit insolvency failed. From a... ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [December 23, 2024, 9:00pm UTC](https://boards.straightdope.com/t/could-they-design-helicopters-based-on-drones/786180/36 "2024-12-23T21:00:13Z")
How would the size of the rotors scale going from 1 to 4? Would that affect the operating speeds of the rotors? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [December 23, 2024, 9:49pm UTC](https://boards.straightdope.com/t/could-they-design-helicopters-based-on-drones/786180/37 "2024-12-23T21:49:25Z")
> [@Johnny\_L.A](#): > > I was going to mention this. I think that to be safe, all rotors in a quad-helicopter would need to be interconnected, and that there be sufficient power to make a safe landing on a single engine. It seems to me that it’d be safer to require it to be able to land safely using n-2 engines, and just make it a requirement that if one engine fails, you land immediately. ---
**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:** [December 23, 2024, 10:14pm UTC](https://boards.straightdope.com/t/could-they-design-helicopters-based-on-drones/786180/38 "2024-12-23T22:14:41Z")
If all rotors are interconnected, then it’s given that you would not have asymmetric thrust. And the aircraft would have to be able to land safely with _no_ power. We have multiengine fixed-wing and rotary-wing aircraft. AFAIK, there isn’t a _requirement_ to land if one engine fails. Definitely a good idea, but I think any requirement would be spelled out in the type certificate. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [December 23, 2024, 10:21pm UTC](https://boards.straightdope.com/t/could-they-design-helicopters-based-on-drones/786180/39 "2024-12-23T22:21:04Z")
> [@HoneyBadgerDC](#): > > How would the size of the rotors scale going from 1 to 4? Roughly speaking, 4x the rotors means they can be half the diameter. But that’s not good enough for a large passenger craft (small craft like flying taxis are ok). I suspect that a few feet is the upper bound for rotor diameter with differential thrust controlled by RPM. But even a fairly modest conventional helicopter has a rotor diameter of 10+ meters… so you’d need 100 of those 1-meter rotors to be equivalent! You could have larger rotors and use differential thrust, but then they’d have to run at constant speed and you’d control thrust with blade angle. But that’s complex and you’re no longer getting the benefit of the quadcopter design. So I think the multi-rotor design really only works for 1-2 person craft. 4 tandem rotors (8 total) seems a pretty good balance and has good failure tolerance. Beyond that, there are more exotic designs but they’ll look at least semi-conventional with a large wing as the primary lift component. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [December 23, 2024, 10:30pm UTC](https://boards.straightdope.com/t/could-they-design-helicopters-based-on-drones/786180/40 "2024-12-23T22:30:18Z")
> [@Johnny\_L.A](#): > > We have multiengine fixed-wing and rotary-wing aircraft. AFAIK, there isn’t a _requirement_ to land if one engine fails. I wouldn’t expect so, with fixed-wing aircraft. First of all, they have a lot more zero-power capability than helicopters. Second, fixed-wing aircraft are pretty picky about their landing spots: If something goes wrong, you usually can’t land immediately: You have to make it to the closest runway (or settle for suboptimal landing strips like a freeway or field, but you don’t want to mandate landing on those). A dronecoptor, however, would be able to land almost anywhere, so “land immediately” is an order that it’s possible to carry out. [Previous page](https://boards.straightdope.com/t/could-they-design-helicopters-based-on-drones/786180.md?page=1) [Next page](https://boards.straightdope.com/t/could-they-design-helicopters-based-on-drones/786180.md?page=3)