64
$\begingroup$

I recently came across this XKCD comic which gives you a number of facts about autogyros:

XKCD Autogyros

Image is copyright XKCD, licensed under CC 2.5 BY-NC

I'm not sure if this is satirical or really drawing attention to some very odd real-world facts, or a mix of the two.

Statements:

  • Looks like a helicopter, but is nothing like a helicopter
  • Flies like a plane but is nothing like a plane
  • Cheap
  • Needs a runway to take off, but not a long one
  • Can land vertically
  • Cannot hover
  • Big blade on top is not powered […]
  • Never stalls
  • Sort of like a powered parachute
  • […] usually homemade.
  • Common in Europe. (I'm fairly sure I've never seen one in the UK)
  • Can often be flown without a licence

Are these things all true? How do they actually work?

$\endgroup$
  • 2
    $\begingroup$ While definitely niche, they're pretty common in the UK and most busy airfields with have them as relatively regular visitors. $\endgroup$ – Dan Mar 28 '18 at 12:29
  • 5
    $\begingroup$ See also aviation.stackexchange.com/questions/49865/… $\endgroup$ – Henning Makholm Mar 28 '18 at 12:39
  • 20
    $\begingroup$ Europe is a big place. For example, the statement "German is commonly spoken in Europe" is clearly true, despite the fact that I can't remember when I last heard it being spoken in the UK. $\endgroup$ – David Richerby Mar 28 '18 at 12:47
  • 6
    $\begingroup$ You left off the final statement, which abuses the word "instinctively". In fact, what anyone instinctively does in a stall is to pull back on the stick/yoke to try to climb faster, which is what caused the stall in the first place. Pilots have to be trained to recognize a stall for what it is, and fight their instinct to pull back, and instead push forward until they get out of the stall. This is similar to drivers learning to steer into a skid. No matter how much one practices these things, they don't truly become instinct. They can, however, become automatic. $\endgroup$ – Monty Harder Mar 28 '18 at 18:41
  • 4
    $\begingroup$ @MontyHarder There's a whole other question on just that one point. I decided not to step on their toes. $\endgroup$ – AJFaraday Mar 28 '18 at 18:41
80
$\begingroup$

Flies like a plane.

To a certain extent in that the controls are plane-like, you do not have helicopter controls (no cyclic, etc.), but you also do not have wing control surfaces, so in some respects like a plane, but not exactly.

Big blade on top is not powered.

True, the blades are unpowered; they rotate due to the wind. Some autogyros use power to rotate the blade to speed before take off, but the power is removed for flight.

Never stalls.

You can put it into a stall attitude, but it self-corrects; it is basically a rotating parachute.The fatal mistake that pilots made with early autogyros was that when they entered stall conditions they instinctively pushed forward on the stick which resulted in the 'fuselage' tipping forward and the blades chopping off the tail. There have been a few fatalities this way.

Sort of like a powered parachute.

Fairly good description. It is more like a powered paraglider than a helicopter or plane.

Common in Europe (I'm fairly sure I've never seen one in the UK)

Maybe this should be more common in Europe. They are still uncommon in Europe, but they are more common in Europe than the US. Wallis Autogyros used to make them in the UK in the 1960s. Check out the Bond film "You Only Live Twice" for one in action (ignore the missiles, etc.; they are not standard fit on autogyros).

Can often be flown without a licence.

Not in anyplace I have flown in Europe. The US may be different.

$\endgroup$
  • 89
    $\begingroup$ Thanks for alerting me to the fact missiles are not standard on Autocyros ;) $\endgroup$ – AJFaraday Mar 28 '18 at 9:11
  • 5
    $\begingroup$ Note, of course the statement made in the comic is that it "flies like a plane but is nothing like a plane", so it sounds like the full statement is pretty accurate. $\endgroup$ – Wayne Werner Mar 28 '18 at 12:53
  • 17
    $\begingroup$ "gnore the missiles etc, they are not standard fit on autogyros" - Dammit $\endgroup$ – Thebluefish Mar 28 '18 at 14:56
  • 7
    $\begingroup$ As mentioned in the answers to the other recent question about this comic, the "fatal mistake" is not about rotor/tail strikes but is about de-loading the rotor when a pilot pitches forward. Without load, the rotor stops spinning and you lose lift. $\endgroup$ – mbrig Mar 28 '18 at 15:09
  • 7
    $\begingroup$ Many of the them in the USA qualify as ultralights. Those don't need a traditional Airman's Certificate, so the last attribute is 'technically correct.' Many of the ones built in Europe, these days, qualify as a Light Sport Aircraft. Those do need an LSA certificate. $\endgroup$ – Meower68 Mar 28 '18 at 17:58
16
$\begingroup$

The "needs a runway to take off" statement is historically true of most autogyros, but many modern ones can take off vertically. It's called a "jump takeoff."

It works by flattening the blade pitch so no lift is generated, coupling the engine to the rotor, and spinning the rotor up to a higher-than-normal RPM. Then the engine is decoupled, and at the same time the blades return to normal pitch. This uses the stored energy in the rapidly-spinning rotor to pull the autogyro upward. From there it transitions to forward flight before it has time to settle to the ground again.

$\endgroup$
  • 1
    $\begingroup$ youtu.be/3RPYWmdv174?t=48 $\endgroup$ – spender Mar 29 '18 at 11:46
  • 6
    $\begingroup$ Arguably for as long as the main rotor is powered, and while that residual momentum remains after it’s removed, the craft as a whole isn’t really an autogyro, since the unpowered main rotor is kind of a distinguishing feature on an autogyro. Only once it starts going forward does it start acting like—read: being—an autogyro. $\endgroup$ – KRyan Mar 29 '18 at 14:37
  • $\begingroup$ @spender your link fails with a privacy error for me $\endgroup$ – Carl Kevinson Mar 29 '18 at 17:52
  • $\begingroup$ @KRyan: To argue in the other direction, a major distinction of an autogyro is that the rotor doesn't produce torque in flight thanks to being unpowered. As long as the rotor is only powered while the craft sits solidly on the runway and can dump excess angular momentum into the ground, having energy stored in the rotor afterwards could well be considered secondary in importance. $\endgroup$ – Henning Makholm Mar 29 '18 at 22:49
  • 1
    $\begingroup$ @HenningMakholm Interesting point! That almost sounds like it would seem different depending on your perspective—to the engineer who doesn’t have to figure out handling the angular momentum, it’s always an autogyro. To the pilot, though, powering the main rotor for lift-off induces very un-autogyro-like behavior, and therefore (again arguably) means it doesn’t really qualify as one for that time. $\endgroup$ – KRyan Mar 29 '18 at 23:21

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.