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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?

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    $\begingroup$ See also aviation.stackexchange.com/questions/49865/… $\endgroup$
    – hmakholm left over Monica
    Commented Mar 28, 2018 at 12:39
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    $\begingroup$ 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
    Commented Mar 28, 2018 at 12:47
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    $\begingroup$ Possible duplicate of Why does this XKCD comic say that autogyros will crash if the pilot reacts to a stall like in a normal airplane? $\endgroup$
    – Harper - Reinstate Monica
    Commented Mar 28, 2018 at 16:51
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    $\begingroup$ 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
    Commented Mar 28, 2018 at 18:41
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    $\begingroup$ @MontyHarder There's a whole other question on just that one point. I decided not to step on their toes. $\endgroup$
    – AJFaraday
    Commented Mar 28, 2018 at 18:41

3 Answers 3

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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.

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    $\begingroup$ Thanks for alerting me to the fact missiles are not standard on Autocyros ;) $\endgroup$
    – AJFaraday
    Commented Mar 28, 2018 at 9:11
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    $\begingroup$ 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
    Commented Mar 28, 2018 at 12:53
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    $\begingroup$ "gnore the missiles etc, they are not standard fit on autogyros" - Dammit $\endgroup$
    – BlueBuddy
    Commented Mar 28, 2018 at 14:56
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    $\begingroup$ 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
    Commented Mar 28, 2018 at 15:09
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    $\begingroup$ 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
    Commented Mar 28, 2018 at 17:58
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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.

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    $\begingroup$ youtu.be/3RPYWmdv174?t=48 $\endgroup$
    – spender
    Commented Mar 29, 2018 at 11:46
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    $\begingroup$ 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
    Commented Mar 29, 2018 at 14:37
  • $\begingroup$ @spender your link fails with a privacy error for me $\endgroup$
    – Carl Kevinson
    Commented Mar 29, 2018 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. $\endgroup$
    – hmakholm left over Monica
    Commented Mar 29, 2018 at 22:49
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    $\begingroup$ @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
    Commented Mar 29, 2018 at 23:21
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Re the "Can often be flown without a license" this is true in the US for certain types of gyro - small, one-person craft which are classed as part 103 aircraft. All the more modern, useful ones that carry two people and have more powerful engines require a license.

Re the "safe unless..." piece, this is kinda true. What Randall means is that most pilots, in situations where they are concerned about possible stalls, will push the stick forwards. If you do this in a gyro, it can unweight the gyro to the point where air is no longer flowing up through the rotor, which will then slow down - quickly. If it loses sufficient momentum (and this can happen very fast), it will stop AND IT WILL NOT START AGAIN. This is because although you will be falling and air will start rushing up through it again, it doesn't happen in a way that allows the blade to start rotating correctly. So gyro pilots have to learn not to do this.

I have 600 hrs in gyros (1200 total) and when I take pilots up they always marvel at the gyro's ability to slow to zero airspeed and its incredible turning radius, but they're always nervous when I pitch up steeply - always have to explain what I'm doing first!

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  • $\begingroup$ Wow! It looks like you’ve joined this area of SE just to give that interesting and informative answer. Thank you very much! $\endgroup$
    – AJFaraday
    Commented Feb 9, 2020 at 20:26

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