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Q: How can a pilot ejecting from a fighter jet get hurt?

Krishna: In aircraft, an ejection seat or ejector seat is a system designed to rescue the pilot or other crew of an aircraft (usually military) in an emergency. In most designs, the seat is propelled out of the aircraft by an explosive charge or rocket motor, carrying the pilot with it. Once clear of the aircraft, the ejection seat deploys a parachute. Ejection seats are common on military aircraft.

There are two usual stages to the  ejection sequence.

  1. A gunpowder charge fires when the handles are pulled. This charge ejects the canopy and drives the seat up a set of rails.
  2. As the seat approaches the top of the rails a lanyard connected to the airplane pulls a pin on the seat’s rocket motor (‘secondary cartridge’) , which fires and propels the crew member well clear of the airplane.

All ejection seats have a sequence of events that occurs in microseconds after you pull the handle. From inertial reals that that pull you and your limbs tightly into the seat to help prepare your back against compression injury to prevent as much as possible flail injuries from your limbs being in the slipsteam to all the components and metal connection being severed before the rocket motor ignites and effectively knocks you out through instantaneous g force. Fortunately such instantaneous force is short lasting and you come too a few seconds later. Modern helmets which are all custom fitted with foamed in place insulation and a tight fitting oxygen mast do a fair job of protecting your face and head.

The turbulent process of ejecting puts pilots at serious risk of injury. Once the rockets fire under the seat, they blow a person up and out of the cockpit with enough force to seriously bruise both shoulders on the harness straps and possibly break collarbones. The pilot has to tuck in his knees and elbows, because if anything hits the side of the cockpit on the way out, it's coming off!

Each pilot (and co-pilot) wears a large parachute and harness that buckles into the seat of their aircraft. When he pulls one or both of the two levers positioned on the sides of the seat, charges fire to blow the aircraft canopy and then rocket boosters under his body take the whole seat, with pilot in it, up and out of the jet. Within seconds he should be floating over the falling aircraft with a parachute canopy fluttering over his head.

In newer two-seat jets, the ejection seats are synchronized so activating one triggers the other. But in the older versions, each person needs to take care of himself or herself. The co-pilot sitting in the rear seat needs to go first—otherwise the rockets from the pilot's seat will burn the person sitting behind. After you fly out, the seat itself falls away. The chute automatically deploys if you are at low enough altitude, and if all goes well, you should float to the ground at a speed that won't kill you.

Modern ejection seats punch you out of the plane with such acceleration that your body experiences 12–14 Gs (or more if you have a low bodyweight and can even go up to 24 g). The gravitational force, or more commonly, g-force, is a measurement of the type of acceleration that causes a perception of weight.  "G -force" is a type of acceleration that can be measured with an accelerometer. Since g-force accelerations indirectly produce weight, any g-force can be described as a "weight per unit mass" (see the synonym specific weight). When the g-force acceleration is produced by the surface of one object being pushed by the surface of another object, the reaction force to this push produces an equal and opposite weight for every unit of an object's mass. The types of forces involved are transmitted through objects by interior mechanical stresses. The g-force acceleration (except certain electromagnetic force influences) is the cause of an object's acceleration in relation to free fall. 

Your spine gets compressed as your butt accelerates upward while your head (and helmet) suddenly push downwards with an apparent weight of 50 pounds. There is a real risk of ruptured vertebral discs, even broken neck or back from being seated incorrectly, particularly with older model ejection seats which imposed even higher G-forces. Once out of the plane, your body is still moving forward at perhaps several hundred miles an hour into an airstream which is basically stationary. Air can be suprisingly dense at that speed. You are being accelerated vertically while being decelerated horizontally, so your body takes a battering from two directions. You will burst blood vessels in your eyes and suffer injury to your face, despite your helmet, visor and oxygen mask. Maybe nosebleed and burst eardrums too. The location of the firing handles is supposed to ensure that your body is in the best position to absorb the Gs when the seat fires. A retraction system will pull your legs towards the seat, otherwise you will lose your toes and possibly a foot or two. If your arms and legs flail around during ejection, you will dislocate/break something. Your head is not restrained, so whiplash injury is likely. The seatbelt webbing will inevitably give you severe bruising and skin abrasions.

Fortunately, you black out, so nothing is going through your mind and you are unaware of the pain … until you (hopefully) regain consciousness floating back to earth under your parachute.

In today’s ejection seats, it is not about taking the rocket ride, it is about what you encounter after you leave the comfort of the cockpit that causes whatever damage or injury you are going to get. Again, assuming you are in a proper position, otherwise standby for back injuries. And when there are more than one pilot, getting hit by the other's seat is quite common.

But your work is not done just because you pulled those levers and left the jet. The system is designed to be mostly automated, but there is no guarantee that everything will function like it's supposed to. A small metal key attaches to the main belt of your harness, and when you eject, it pulls and activates a small red knob on the left side of your harness, called the "red apple" by airmen. This activates your parachute, which will deploy automatically as long as you are 14,000 feet or lower. (Any higher and you could freeze, or go hypoxic from lack of oxygen, or both. Not to mention that canopy openings at high altitude are much more violent due to the thinner air, increasing the risk of injury upon chute deployment.)

If you fall below 14,000 feet and your chute fails to deploy, you can pull a rip cord manually to release the canopy.

If the chute deploys above 14,000 feet and you are having trouble breathing, there is a "green apple" knob on the right side of your harness that you can pull to buy yourself about eight minutes of oxygen supplied to your mask from a reserve in your parachute rig.

If you ever have to get out of a fighter jet, you will quickly want to assess your situation, which will determine the next step. You are over either water or land, and more importantly, you are either at a high enough altitude to prepare for the landing or too low to do anything but brace for impact.

While going into water, pilots say, they even think about sharks, sea snakes, and what not!

In the case of a low-altitude ejection, all you can do is glance at your canopy to make sure it opened fully and then tuck your feet, bend your knees, and prepare to hit hard. The proper technique is to hit with the side of one of your feet first, and then collapse with the momentum so that the impact spreads out over the side of your leg, your hip, and then below the shoulder on your back, dissipating some of the energy. If you land straight on the balls of your feet, or with stiff legs, you're liable to break something even if you have had adequate time to slow down with the parachute.

If you eject up around 10,000 feet, so you have a little time in the air, there is a standard checklist to run through, one that fighter pilots can rattle off in their sleep: canopy, visor, mask, seat kit, LPU (life preserver unit), 4-line jettison, steer into the wind, prepare for PLF (parachute landing fall). First you put your hands on the parachute risers and tilt your head back to get a good look at the chute. It's possible that in the chaos of ejection the suspension lines get twisted up, in which case you are supposed to grab the risers, pull them apart, and kick your legs like a wild man riding a bicycle to spin yourself around and untangle the lines.

Watch this video that shows how this happens...

If the chute doesn't open properly, the pilot has to correct it, by doing different maneuvers in the air if he has time.

 Once the canopy is fully deployed, the rest of the checklist is fairly straightforward. Lift your visor away from your eyes and then pull off your mask. Make sure the seat itself has fallen away from you and that the seat kit, full of survival supplies, is dangling behind you. After that, if you are going make a water landing, activate your life preserver unit by pulling down on two cords.

Then it comes time for the four-line jettison. Assuming you didn't have to cut any lines, your chute is fully deployed, and there are no holes in your canopy, you are instructed to pull down on both the steering lines, all the way to your hips, which shears four lines on one side of the parachute. This creates an indentation on that side of the chute, which propels the parachute forward at about 5 knots.

After the four-line jettison, the goal is to use the steering lines to steer into the wind so that when you hit the ground, you are traveling nearly straight down. You get into the correct body position for a PLF—feet together, bent knees, chin tucked in—and use the same technique mentioned before to fall along one side of your body, maximizing the number of impact surfaces.

Once you touch down, it's a matter of surviving until you are found and rescued. 

Anything can go wrong in all these exercises and it is possible that the pilot gets hurt. If you have to eject from a fighter plane, you will come away from the experience significantly bruised and battered, possibly with fractured bones and torn ligaments. But despite the risks of ejection seats, they do save pilots' lives.

Sometimes, it seems, the seats don't eject due to some snags! This was common in older versions of planes but in today's cockpits, this is very rare.The most common reason for ejection failure was the pilot ejecting while out of the ejection seat’s safe operating envelope. This usually happens in a very steep dive and with a high rate of descent whereby it was too late for the ejection to function properly and the pilot to survive. Another instance would be ejecting while inverted at a very low altitude and straight into the ground. Years ago, ejection seats were not, “zero-zero” meaning they would not function with zero airspeed and zero altitude. They needed some speed and some altitude, and could not function if static and on the ground.

The procedure then is to pull the guillotine to separate the pilot from the seat and then stand up on the seat and dive over the side hopefully missing the wing and horizontal stabilizer deploying the parachute manually! That is, if there is enough time and altitude to bail out! But ejection failure and survival rates are very low. 

Sometimes, temporal distortion( a state where the mind slows down time) occurs during stressful situations. In such cases, a person may momentarily perceive time as slowing down, stopping, speeding up, or even running backwards, as the timing and temporal order of events are misperceived. This makes the perceived lag in pulling the handle and seat ejecting!

Need I add, despite everything, it is a necessary risk?

It is all about training. And pilots do get a lot of it. When they have to get out of an airborne, moving and damaged plane, they just do it. 

Watch this video where a pilot who barely survived tells his own story ...

And, these fighter pilots are really great. Because they live on adrenaline day in and day out. And one fighter pilot told me when I asked him, 'Do you get scared?',  "We do, sometimes, but we are not supposed to talk about it!" 

I heard the same reply from an astronaut.  

They are  heroes because they are not afraid. They are heroes because they conquered their fear!

That is why these professions are some of my  favourite ones.

Sources: Pilot Narrations and Popular Mechanics

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