MadSci Network: Engineering

Re: I would like to know why does not passengers airplanes have a parashute.

Date: Wed Dec 16 11:13:04 1998
Posted By: Fernando Grau, Staff, Aerodynamics, Embraer
Area of science: Engineering
ID: 912890828.Eg

Dear Friend:

To carry on a safe jump from an airplane some special conditions must be 
taken into account.  Air temperature, as well as atmospheric pressure are 
very important to our body life functions.  Itīs impossible for someone to 
survive more than 20 seconds or so in the high altitudes usually flown by 
most airliners nowadays (more than 35,000 ft) without some kind of 
"astronaut" clothes.  Itīs impossible to breath, the temperature is very 
low (-50 degrees below water freezing temperature), everybody looses 
consciousness in less then 30 seconds, freeze in less than one minute.  
Thereīs no time to free-fall and reach a lower (and warmer) altitude.

But, what about a low altitude accident?  In that case the time elapsed 
from the alarm failure and emergency procedures until the hipotetical 
parachute evacuation of the airplane (remember, just two or four doors for 
almost 200 passengers...) is so high that itīs almost certain that the 
plane had already chashed in the meantime.  Also, airliners doors are not 
prepared to be fully open during flight, so as you can see parachute and 
big airplanes does not team very well...

The only situation that I can imagine where parachutes would be useful is, 
perhaps, more common than accidents:  highjacks.  I think a controlled 
evacuation could be attempted. However the air speed impact over the 
passengers and the structure problems that would arise from opening doors 
are not predictable.

I hope to have been helpful in showing you some interesting points about 
that parachute business.

Best regards,

Fernando Grau

ps. just for the sake of curiosity, there is a new aircraft (a little one, 
just four seats) that has a new integrated parachute system for the hole 
airplane!!  It have been already tested and approved by FAA (Federal 
Aviation Administration, responsable for aircrafe security).

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