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In the manual that comes with my rock climbing rope I bought (black diamond) there's a picture with a death sign when the temperature goes below -62 Celsius. Temperatures outside of planes reach well below this so it's possible the checked bag can hit less than -62 C. So how exactly is it safe to check in rock climbing gear?

Also, I'm afraid of the TSA manhandling my equipment.

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    Don't forget live animals (pets) also travel in the hold, and they don't like that kind of temperature either. But it's not outside
    – Chris H
    Jan 3 at 7:00
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    @JonCuster, thinking purely hypothetically, if it was unloaded roughly while still below the DBT, it could get damaged. But that would require (i) it to get that cold in the first place, which it won't in a pressurised aircraft, (ii) it to stay that cold until unloading - which would take a lot of insulation, and that would act as padding, and (iii) it to take a hard enough knock; packing well so it doesn't get slammed together would seem reasonable anyway.
    – Chris H
    Jan 3 at 14:31
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    Related on SE TRavel: Will my checked luggage freeze in the airplane? The answer is NO. Jan 3 at 15:59
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    @JonCuster it's pointless to just say from experience that it hasn't happened yet when it comes to life-death equipment. But maybe I'll just put a bottle of wine in the bag as a canary Jan 3 at 19:14
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    @JobHunter69 - and the baggage handlers treat all bags carefully, or so they will swear. Your pack with the rack inside was never dropped from waist high? Never slid down a slab? I think you need to think deeply about risk management and your current approach to it.
    – Jon Custer
    Jan 3 at 21:00

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As noted in comments by WeatherVane, the baggage area of a commercial flight will never approach anything near -62C. Sitting out on the wing, sure, but consider there is only a thin piece of aluminum between your feet and the baggage are, and your feet don't freeze (and pets and liquids, not to mention fresh flowers, are carried there routinely).

This still leaves the question of understanding just why there is a minimum temperature stated for use of the climbing rope (and potentially other climbing gear). This is because key material properties can change dramatically with temperature.

For many metal alloys (e.g. steel), there is a defined ductile-to-brittle transition temperature. Normally one expects steel to deform slightly (elastically) under stress, and then rebound completely when the stress is removed. If you exceed the maximum tensile (or shear) stress, one expects the material to deform more (plastically), yet stay in one piece until a much higher stress finally pulls it apart.

In contrast, when brittle, an applied stress can result in a small pre-existing crack (and all manufactured items have pre-existing cracks) to rapidly and uncontrollably extend through the material, breaking it in half. The classic example would be Liberty Ships in WW2. But, if there is not an applied stress, there will be no brittle failure.

Your rope is not a metal alloy, but similar principles apply for many polymers - above one temperature they are elastic, below it brittle. Folks living in cold regions know this well, where many normal commercial items (plastic buckets, windshield wipers) will just shatter in sub-zero temperatures. Again, such failure requires a stress to be applied (although sometimes internal stresses are enough). So, yes, the manufacturer of your rope is telling you that your rope will not perform to spec below -62C and may well break upon you taking a fall while the rope is that cold. (You, personally, are unlikely to work to spec at -62C as well.)

A bag of climbing gear should happily take a stint at -62C without major issues. There are no applied stresses (none approaching normal fall forces), so no driving force for brittle failure.

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    At one time, the aircraft hold was exposed to atmospheric temperature and pressure, but this changed in the later part of the 20th century, I'm not sure exactly when. However, the wheel housings have yet to get the upgrade, as many stowaways discover. Jan 3 at 20:52
  • @WeatherVane - I believe that changed with jets operating at altitudes higher than the DC-3. They had to pressurize the cabin, and the stresses within the fuselage could not be tolerated if the baggage are was not also pressurized to match the cabin. That also means that the passenger cabin and baggage area partitions do not need to be sealed. Air flows intentionally between them (note there are not air intakes for circulation inside the passenger area - they are in the baggage area).
    – Jon Custer
    Jan 3 at 20:58
  • It certainly makes sense to seal the whole fuselage and not irregularly shaped parts of it. Jan 3 at 21:46
  • I'd add to this that your rope will not perform to spec below -62C and may well break upon you taking a fall while the rope is that cold. part, that -62 C is very very cold and unless you are climbing very high altitude (Himalaya) or in very cold parts of Russia/Arctic or Antarctica, then you are very very unlikely to experience these sorts of temperatures.
    – bob1
    Jan 3 at 21:57
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    @bob1 - indeed, I want no part of frolicking around in -62C.
    – Jon Custer
    Jan 3 at 22:00

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