A hole blows open overhead. The wind surges in. The pilot can feel the chemical cartridge ignite under his seat, which activates a catapult that pushes his seat up a rail. The wind wants to flip the seat around like a milkweed seed, but the thrust from STAPAC offsets the rotation and keeps the seat and pilot upright and forward facing.
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These seats also double as restraint systems for the crewmembers both during an ejection and during normal operation. Ejection seats are just one part of a larger system called the assisted egress system. Not all planes have canopies. Those that don't will have escape hatches built into the roof of the plane. These hatches blow just before the ejection seat is activated, giving crewmembers an escape portal. Seats are activated through different methods.
Some have pull handles on the sides or in the middle of the seat. Others are activated when a crew member pulls a face curtain down to cover and protect his or her face.
In the next section, you will find out what happens once the seat is activated. When a crewmember lifts the pull handle or yanks the face curtain down on the ejection seat, it sets off a chain of events that propels the canopy away from the plane and thrusts the crewmember safely out. Ejecting from a plane takes no more than four seconds from the time the ejection handle is pulled.
The exact amount of time depends on the seat model and the crewmember's body weight. Pulling the ejection handle on a seat sets off an explosive cartridge in the catapult gun, launching the ejection seat into the air. As the seat rides up the guide rails , a leg-restraint system is activated. These leg restraints are designed to protect the crewmember's legs from getting caught or harmed by debris during the ejection.
An underseat rocket motor provides the force that lifts the crewmember to a safe height, and this force is not outside normal human physiological limitations, according to documents from Goodrich Corporation , a manufacturer of ejection seats used by the U. Prior to the ejection system launching, the canopy has to be jettisoned to allow the crewmember to escape the cockpit.
There are at least three ways that the canopy or ceiling of the airplane can be blown to allow the crewmember to escape:. The seat, parachute and survival pack are also ejected from the plane along with the crewmember.
After the seat and crewmember have cleared the cockpit, this rocket will lift the crewmember another to feet This added propulsion allows the crewmember to clear the tail of the plane.
Air Force. More than 90 percent of those ejections were successful. There were 42 fatalities. Once out of the plane, a drogue gun in the seat fires a metal slug that pulls a small parachute, called a drogue parachute , out of the top of the chair.
This slows the person's rate of descent and stabilizes the seat's altitude and trajectory. After a specified amount of time, an altitude sensor causes the drogue parachute to pull the main parachute from the pilot's chute pack.
At this point, a seat-man-separator motor fires and the seat falls away from the crewmember. The person then falls back to Earth as with any parachute landing. The one used is determined by the aircraft's altitude and airspeed at the time of ejection.
These two parameters are measured by the environmental sensor and recovery sequencer in the back of the ejection seat.
The environmental sensor senses the airspeed and altitude of the seat and sends data to the recovery sequencer. When the ejection sequence begins, the seat travels up the guide rails and exposes pitot tubes. Pitot tubes, named for physicist Henri Pitot, are designed to measure air-pressure differences to determine the velocity of the air. Data about the air flow is sent to the sequencer, which then selects from the three modes of ejections:.
Ejecting from an airplane is a violent sequence of events that places the human body under an extreme amount of force. The primary factors involved in an aircraft ejection are the force and acceleration of the crewmember, according to Martin Herker , a former physics teacher.
To determine the force exerted on the person being ejected, we have to look at Newton's second law of motion , which states that the acceleration of an object depends on the force acting upon it and the mass of the object. Regarding a crewmember ejecting from a plane, M equals his or her body mass plus the mass of the seat.
A is equal to the acceleration created by the catapult and the underseat rocket. Acceleration is measured in terms of G, or gravity forces.
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