Duane

        I can assure you that you will never see this. Firstly, the speeds at which aircraft fly at are completely incompatible with parachute deployment. Any parachute would be torn to shreds. Even parachute deployment at speeds of the terminal velocity of a person (about 146 mph depending on posture) are very violent affairs. The decelerative effect goes up as the square of the speed. i.e. double the speed and you have four times the shock, triple the speed and it's nine times the shock. So even if it didn't kill the passengers, even if they were strapped securely in, the individual aircraft components would not and could not withstand that opening shock. What might happen if only one chute failed or if they all opened at different times? What would happen if the airliner was spinning and the chutes deployed? I think you would end up with 4 chutes nicely Roman Candled (i.e. twisted around each other).

 

The way it's achieved in ejection seats is (after ejection) for a small pilot chute to establish a level decelerating seat attitude. When a longitudinal g controller senses less than 400 knots it enables a barostatic trigger. If the seat is above 14,000 feet it enables the drogue chute to open (four times the diameter of the pilot chute) and stabilise the seat (so it's not tumbling). At 14,000ft the scissor shackle in the top of the seat is allowed to open and the main chute canopy is drawn out of the headbox (at the same time as the seat harness is disconnected at its anchor points). This is 8 times the diameter of the drogue chute. The main canopy, as it deploys, pulls the pilot from the seat (which falls away). This is an automatic process. There are also manual backup processes. It is very complex. The F111 has an escape capsule but its operation is very much similar to the ejection seat operation. Escape from the Space Shuttle at lower altitudes is via a hooked-up slide down off the end of a telescopic pole that is extended from a hatch, i.e. they don't have ejection seats. The extensible pole is a desperate measure they came up with following the Challenger disaster. I doubt very much that it would work in practise. The only chutes the Shuttle has are drag chutes for deceleration after landing.

 

Sorry Duane, but it's just not a practical solution. The practical solution is for airliner systems to be made as reliable and as trustworthy as possible. This doesn't happen now because there are cost cut-offs on what the airlines are prepared to spend to make it a safer operation. Things such as the wiring that gets progressively less safe as it ages, and the wire that was never safe to begin with, these problems are easier to ignore than to fix. This has been one of the inevitable issues arising from deregulation. Deregulation has meant very stiff cost-competition for business, because airlines are left to decide just how they run their operation. The airline that spends more on maintenance and safety measures must either charge more or spend less on inflight entertainment. Guess what they do? Mostly it works out that the passenger is not subjected to too high a level of risk. Sometimes the gamble fails and accidents like Swissair 111 can happen. They happen because all the short-cuts and unsmart decisions are links in a chain that is forged by the circumstances prevailing at the time. Any link is broken and the accident doesn't happen, i.e. it may be simply an incident. Far too frequently there are enough links ready to form up into that accident chain and we then have a disaster. TWA800 would not have happened if the fuel had not been heated by a long period of ground operation on such a hot day. But eventually the faulty wiring was going to run into that deadly combination of circumstances. If not on that day, then another day when they had no reason to fill the centre wing tank and it was hot on the ground.

 

So perhaps you can now appreciate that your solution was not really a solution at all. It wouldn't have saved TWA800, nor Swissair 111, nor EgyptAir MS990, nor Valujet 592, nor PanAm103, nor Air India 182 nor the ATR72 at Roselawn, even if that chute technology had been available and had worked. I think you might be able to appreciate that other considerations determine the level of airliner safety. IASA works at improving the infrastructural basis for aviation safety. We leave Flight Safety up to the pilots. If they're given the right tools they'll normally do a very good job. If the systems start failing haphazardly because the wiring arc-tracks then they will have smoke, failing instrumentation, loss of communication, breathing and vision problems, controllability issues and passenger panic. Eventually they reach a point called task overload where they just cannot cope any more. Best avoided by getting all the hardware right in the first place - that's the way to build a safer plane .....don't you think?

 

regards

IASA Australasia

www.iasa.com.au