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I was watching an episode of "How do They Do it" on, The Discovery Channel the other day about putting parachutes on airplanes. It's extremely difficult to put a parachute on a plane because for a person to safely descend jumping out of an airplane, the parachute has to be one hundred feet wide. So for a parachute to work on just a small aircraft, you're going to need a massive parachute which is going to take up a lot of room.
Aviation experts asserted that putting a parachute on a small plane could not be done. Ballistic Recovery Systems was a company tasked to create the first airplane parachute, by a pilot who survived a plane crash. They faced multiple problems in being able to accomplish this. First is weight, you need a very large parachute for an airplane, roughly 1,000 square feet. A parachute of that size with regular parachute nylon would weigh as much as a small plane. The company made the parachute out of a super strong light weight composite and the parachute strings out of a special kind of nylon that is five times tougher and one hundred times lighter than steel. The parachute weighs just 30 pounds.
The next problem is bulk. You can't strap a parachute pack the size of an elephant to the back of an airplane. The company devised a folding technique that minimizes the amount of space the parachute uses. Then a massive hydraulic press is used to compact the parachute. Under a force of more than 11 tons the folded parachute is as dense as a block of wood. Another challenge of the airplane parachute was getting it to unravel quickly. The longer it takes to deploy the less time there is to decelerate the plane. The engineers came up with the idea of blowing the parachute open with rockets. Custom made rocket motors employ two linked electrical detonators which are housed in the base of the rocket. A one pound explosive charge is added which, when detonated, forces the parachute open.
One last major problem in getting the parachute to work was the speed of the plane. If the chute opened too quickly it would give the airplane such a pull that the parachute itself could rip the plane apart. The solution to this problem is the "slider"; a simple ring of fabric that prevents the chute from opening fully at the start but then slides down allowing it to open wider and wider as the plane slows.
The parachute is added to the airplane in a way that it doesn't rip open the airplane. The nylon straps are built into the body of the plane. When the rockets deploy they eject a five foot thick fiberglass panel from the body of the aircraft. This design is intended to release the chute with no harm being done to the plane. More than 30,000 parachutes are now installed on light aircraft throughout the world and have saved over 200 planes and more importantly, the lives of many pilots and passengers.
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