This is the third in a series of 5 (at this point) questions. It's not relevant to this question, but for anyone who's curious this was the first, this the second.

Conditions for this question are:

  • Earth-normal atmospheric pressure/content. (Or close)

  • I'm aware that over 38,000 feet has been achieved by exploiting thermals. This slow and steady way is not what I need.

  • I need the ascent to be sudden and unexpected (for an arguably inexperienced pilot), be it; meteorological, geothermal or by some other (not fantasy) means.

  • It should not kill the pilot - if you can plausably argue a volcanic erruption - then fine but the pilot must survive (unconsciousness is just fine though).

Any landscape type can be specified in supporting arguments within the answer, sea nearby, desert, mountains, geisers, volcanoes, icefields - anything that could feasably contribute to the desired sudden lift.

A hang glider, the pilot taken by surprise, there is a sudden unexpected lift to 25,000 feet altitude, what could do this?

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    $\begingroup$ I'd swear I read an article several years ago about someone over Australia having something like this happen. $\endgroup$ – Michael Richardson Apr 1 '19 at 21:37
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    $\begingroup$ Nevermind. Chasly's answer mentions this right away. $\endgroup$ – Michael Richardson Apr 1 '19 at 22:24
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    $\begingroup$ Gliding altitude records are not set using thermals, but by "wave riding" the airflow over mountain ranges. Just like an airfoil, the profile of a line of hills affects the air flow up to 10 times the height of the hills themselves. In the right weather conditions these flows can remain stable for several days, and nights (unlike thermals which only exist during the day). Even in the UK with hills of only a few thousand feet, altitudes of 20,000ft are not difficult to achieve - except for the problem of keeping out of commercial controlled airspace. $\endgroup$ – alephzero Apr 1 '19 at 23:54
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    $\begingroup$ pedantry: thermals can exist at night, if there is a heat source on the ground. (a wildfire or lava flow would do nicely :)) $\endgroup$ – Jeremy Friesner Apr 2 '19 at 3:16
  • $\begingroup$ @Michael Richardson Possibly a canopy (trike or parachute) during a thunderstorm. $\endgroup$ – mckenzm Apr 2 '19 at 4:19

Getting caught in a thunderstorm is the most likely cause. This can happen even to experts if they are incautious enough to take risks with the weather.

Here's an example with a paraglider. (I'll see what I can find for a hang-glider)

Ewa Wisnierska was sucked into a powerful thunderstorm while training for the world paragliding championships in Australia. She was carried, unconscious and wearing a layer of ice, to an altitude of more than 32,000 feet into the eye of the storm. https://youtu.be/IXLdsnB5VBw

Here's another - this is a good one because it is videoed with a live commentary from the pilot who escaped the updraft before it was too late.

Caught in Cloud Suck! - Life lesson from 3Km above sea level https://youtu.be/FdoGtqCQ2ZY

Some science

Hang-gliders are likely to find it easier to escape a storm because their forward speed can be much greater that that of a paraglider. They should be able fly out of it provided they can keep a sense of direction.

Hang-glider Beginner wing 14 mph to 45 mph. Advanced wing - 16 mph, to over 100 mph which has been clocked in speed gliding competitions http://www.hanggliding.org/wiki/A_Comparison_of_Hang_Gliding_to_Paragliding

Paraglider Beginner wing 13mph to 22mph. Advanced wing - 14 mph to 35mph http://www.hanggliding.org/wiki/A_Comparison_of_Hang_Gliding_to_Paragliding

EDIT (from the same source)

See under Wind penetration where my above suggestion is supported.


Here is a claim that it can happen to hang-gliders as well but there is no reference to back it up.

In one reported incident, two hang gliders were caught in cloud suck by the same storm clouds. Both gliders lost consciousness above 30,000 feet, one, happily, was released by the storm, and regained lucidity before crashing into the ground. The other glider was not so fortunate. His frozen body was discovered later and returned to his family. https://www.toysperiod.com/blog/extreme-sports/hang-gliders-in-the-sky/

Cloud suck

If you want to know how people get trapped and about emergency procedures for escape, then I suggest you Google "cloud suck".

Cloud suck is a phenomenon commonly known in paragliding, hang gliding, and sailplane flying where pilots experience significant lift due to a thermal under the base of cumulus clouds, especially towering cumulus and cumulonimbus. The vertical extent of a cumulus cloud is a good indicator of the strength of lift beneath it, and the potential for cloud suck. Cloud suck most commonly occurs in low pressure weather and in humid conditions.


Hypoxia due to Altitude

Helios Airways Flight 522 was a scheduled passenger flight from Larnaca, Cyprus, to Athens, Greece, that crashed on 14 August 2005, killing all 121 passengers and crew on board. A loss of cabin pressurization incapacitated the crew ... https://en.wikipedia.org/wiki/Helios_Airways_Flight_522

The Time of Useful Consciousness will vary depending on personal physiological factors (e.g. if you're a smoker your blood doesn't oxygenate as well - you will probably have less time. If you're a mountain climber in excellent shape and used to breathing rarified air on your climbs you'll probably have a little more time). https://aviation.stackexchange.com/questions/2766/how-long-will-one-remain-conscious-in-the-event-of-a-sudden-cabin-depressurizati

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    $\begingroup$ Ok, I'd no idea it was that easy for even the experienced pilot, I need to improve my research methodology. Good answer. +1 $\endgroup$ – Tantalus' touch. Apr 1 '19 at 20:24
  • $\begingroup$ @Agrajag - I've done a bit of paragliding and hang-gliding! $\endgroup$ – chasly - supports Monica Apr 1 '19 at 20:31
  • $\begingroup$ @Agrajag - Does it have to be a hang-glider or could it be a paraglider? I've yet to find any evidence of the former being trapped in a storm cloud. Probably due to the difference in forward speed (see edit to my answer). $\endgroup$ – chasly - supports Monica Apr 1 '19 at 20:44
  • $\begingroup$ I wasn't going to be specific 'till I'd decided. I'm just going with hang glider beginner, but keeping an open mind regarding the actual tech. I'll take it all in and use the ideas, or something different that springs from them. $\endgroup$ – Tantalus' touch. Apr 1 '19 at 20:51
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    $\begingroup$ This is definitive answer to the question. +1. $\endgroup$ – AlexP Apr 1 '19 at 21:12

A hang glider caught under a powerful cumulo-nimbus is unlikely to be able to 'outfly' the updraft without breaking the airframe.

I have flown a high performance sailplane capable of around 180 knots, flying fast with the airbrakes out, wheel down and with crossed controls and STILL showing a healthy 5 metres per second climb. With all that one would expect to be sinking at probably 15 m/s. or more. 'Assuming the glide angle of a brick' as we say. A hang glider would simply be sucked in to the cloud and spat out at random. I flew ( sailplanes ) with a chap who, in the early days of gliding got inadvertently sucked in to a South African CuNim and emerged from the anvil at well over 30 000' ( the instruments all froze well below that ) the airframe was caked in ice and he had no supplemental oxygen. Very fortunate to survive. I have seen rates of over 20 m/s in a sailplane under big CuNims ( that's around 80 kilometers per hour straight UP! ) and rates WELL in excess of that have been recorded inside big developed storms. A H/G would go from entry at say 5000' to exit at 25000' in around 5 ( very terrifying ) minutes. The pilot would be lashed with hail, probably suffering from the cold and damp and possibly annoxia.

I very much doubt that a H/G could enter wave without being able to avoid it. In conditions where they were lifted to 25 000' in a very short space of time no one in their right mind would be out with a hang glider at all. ( I have piloted a sailplane to over 32000 in wave ) The windspeeds required would be well beyond the capabilities of the H/G to get airborne, penetrate any turbulence or penetrate enough to stay in the lift. Its implausible.

Inadvertent entry into cloud is the most likely scenario. ( although a lot of people who do this are no longer here to tell the tale as without instrumentation and experience, it is highly likely that the airframe breaks )

This was on a forecast relatively benign thermal day. cloud entry

  • $\begingroup$ The recommended strategy is to fly away from the cloud until you exit the area of lift, rather than just trying to dive down against the lift. (and better yet, to keep an eye on the weather and your rate-of-climb so that you'll know well in advance when trouble is brewing, and apply an ounce prevention instead of a pound of cure) $\endgroup$ – Jeremy Friesner Apr 2 '19 at 3:35
  • $\begingroup$ That's as maybe but it doesn't answer the OP's question! :) $\endgroup$ – nimbusgb Apr 2 '19 at 9:51
  • $\begingroup$ If the hang-glider air-frame seriously breaks, then the only option is to cut yourself out of the harness, fall out of the cloud and hope you emerge before you hit the ground. You then deploy your emergency chute. (Don't do it while you are still in the cumulo-nimbus or you will just go up again with no hope of steering your way out.) $\endgroup$ – chasly - supports Monica Apr 2 '19 at 12:43
  • $\begingroup$ @JeremyFriesner: easier said than done. In the absolute majority of cases the pilot would not be very well equipped to fly blind, and if you are climbing 40m/s you might have just a couple minutes of consciousness by the time it's obvious you should not be there. There are documented cases of this happening to experienced pilots. $\endgroup$ – Martin Argerami Apr 2 '19 at 13:33

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