moose said:
When does everyone think "OK we have to jump now, we won't make it" and actually have time to jump out and get everyone out? Most of the time you wouldn't know you are definitely going to crash, and once you do, well, you wouldn't have time for parachutes. Plus, the added weight would make airplane tickets cost more because of more fuel usage. Why make something safe only slightly safer, yet uneconomically? I mean, couldn't cars have ejection seats, so that when you crash, instead of airbags, you get ejected in the air??
It's not only that. The FAA requires that reserve parachutes get repacked every 90 days, whether they're used or not. This has to be performed by an FAA Master Rigger and the going rate, on a civilian drop zone is about $50 per repack. Multiply $50 by 300 by 4 times per year, and you're looking at an additional $60,000 per year per plane. You'd also have to store the parachutes somewhere that the passengers couldn't get too them during a routine flight, otherwise they'd have to be inspected after every flight to make sure they hadn't been tampered with.
As bad as the financial problems are, they wouldn't be anything compared to the technical problems. You have 300 people scared out of their minds trying to don a piece of gear they are completely unfamiliar with, move to the rear of the plane, and jump out.
Assuming that's no problem, when 300 people run to the rear of the plane, the Center of Gravity will shift beyond the Aft CG limit and the plane will stall, the people will be pinned to the ceiling until the pilot recovers from the stall (if he can,) then slung to the floor. The plane probably isn't in very good condition in any case (everyone's jumping out after all) so this problem is more likely.
Next you've got exit speed. A commercial airplane cruises at about 400-500 knots. Standard parachutes are made to open at speeds more along 110 knots. No parachute I know of is designed to open at 4-500 kts. It would either rip the fabric of the canopy to shreds, break most of the lines on the chute, or rip the harness out from between your legs (maybe taking them along.) The only way to slow down to the proper speed would be to jump out and freefall for a while until you reached a slower speed, then deploy. Obviously, this isn't possible with a static line system, and even if you did give the passengers a manually deployed chute, how many of them are going to wait more than a nanosecond before they pull the ripcord or throw out the pilot chute.
Back when I jumped every weekend, I carried my rig on a commercial airliner a couple of times. I thought about every conceivable scenario, and the only time I could see using it was if the plane disentigrated around me and I was able to don it before I passed out from hypoxia. I ended up just putting it in the overhead bin.
) I'd rather take my chances with the pilot managing to get the plane back under control or landing with a plane still between me and the ground with emergency crews ready and waiting.
Well, with the exception of the rare mid-air collision I suppose.
