Decompression over High Terrain

[Heidhurtin]

Guys, apologies if this is the wrong forum, but I didn't want to ask on the thread dealing with the Sichuan Air windscreen blowout. From a non-pilot, how do you plan for decompression events while flying over mountainous areas? Is there a planned route to descend safely, and a minimum descent time which (could) restrict possible planned routes? It strikes me as a huge task to keep this in mind during a flight since the descent route would obviously change as the flight progresses?

[parabellum]

Yes, the available time of oxygen supply and the Minimum Safe Altitude, (MSA) are critical and the primary concerns. Your company ops manual should have a diagrammatic planned route over high terrain, supported by text, that will show you the still air 'turn back' point and the 'continue point', variable according to the head or tail wind component and based on radio aids or LNav positions. Both turn back and continue routes should also show the respective MSA's as they change with your progress. Time and distance information will normally be included. It would indeed be a lot to memorize so you would expect to have an up to date copy of this chart to be available and to hand on the flight deck during this period of flight. A crew self briefing and discussion would be normal practice before transition of the high ground began and situational awareness to be maintained at a high level. Companies like Jeppesen, who produce a full range of en route and airfield charts, may include this necessary chart in their manuals, carried on the aircraft.

[wiggy]

(Parabellum beat me to it, but)

Depends how high the ground is and for how long....

Over the likes of the Alps you’ll be aware of the high terrain but probably won’t need an emergency route because the high terrain probably only lasts a handful of minutes.... so if you decompressed you’d descend to a high but safe minimum altitude initially, get over that little area and you can descend to habitable altitudes...

Other parts of the World (e.g parts of Afghanistan, China, Tibet, parts of Africa) where the ground is higher for “longer”, so to speak , you’ll probably have quite detailed escape routes detailed in your performance manuals, and if on an relevant route you may well have the required escape route loaded into the back up route/Route 2 of your Flight management computer, ready to go should things go wrong.

it’s one of those important things that one needs to be aware and emphasise that there is more to the job in the cruise than reading the paper and drinking coffee....:p

[Heidhurtin]

Thanks guys, makes sense but also adds more kudos to the Captain of the Shizuan flight - imagine trying to cope with the problem with the gale caused by the window blowout tossing the charts around, some of the automatics (navigation data?) not working and your FO incapacitated. Respect!