Thursday, September 17, 2009

Navy Briefing of the Week: Carrier Catapult Shot

When NavyGuy was doing his boat detachment off the coast of Virginia on the U.S.S. Truman, he was able to get some videos! First up is a catapult shot, in which the airplane is literally catapulted off of the deck. I'm going to let NavyGuy explain... (I'd recommend watching the video first, then reading, then watching again to make sense of it all :)

You'll see our airplane taxiing up to the "shuttle" which is the portion of the catapult that protrudes above the deck, and is what attaches to the jet's nose gear to launch us. The person standing in front of us is called a "Yellow Shirt" or "Taxi Director" and he or she is one of the people in charge of directing all the airplanes around the deck of the carrier. Believe it or not, even though the deck is over 1000 feet long and several hundred across, it gets really cramped when there are dozens of high powered jet aircraft moving around. At this point, he's trying to get us all set up and aligned so we're pointing straight down the catapult when we get launched.

The white smoke rising from the deck all around him is actually steam from the last catapult shot. We use steam because the nuclear reactor produces lots of it in the normal generation of power for the ship. Once we're all set up and aligned, you'll see the Jet Blast Deflector or "JBD" come up out of the deck to keep the hot exhaust from blowing anyone overboard. At this point, we're doing our final checks in the cockpit and the pilot is verifying the weight the catapult crew has for our jet. The weight of the aircraft is very important because the cat shot has to be powerful enough to accelerate the jet to it's minimum speed, but not so powerful that it damages the aircraft's nose gear in the launch.

Soon after the JBD comes up out of the deck, you'll hear our engines go to full power. This means that we're "In Tension" which means the the catapult is armed and ready to launch us off the deck. At this point, the only thing that prevents the aircraft from moving down the deck is a small bar called a "Hold Back" which is connected to the nose gear by a small piece of metal which is engineered to break at a certain tension setting, unique to each model of aircraft. When the catapult fires, this piece of metal, which looks a lot like a bar bell in a free weight set at a gym, breaks and releases the aircraft to be launched. Once we're "In Tension" the pilot keeps the throttles at full power no matter what happens, unless a deck crew member walks out in front of the jet and gives us the signal that the catapult has been safed so it can't fire.

Even on the top of the tower, you can feel the hot jet exhaust, which is why the camera starts to bounce a little more at this point. The ground crew checks to make sure that there is no one in the way of the jet, and the pilot checks all this controls. At that point, he salutes the "Shooter" who is the person responsible for firing the catapult, and he "shoots" the aircraft off the carrier deck. We accelerate from 0 to about 170 mph in about 1-2 seconds and we're flying. We climb up to 600 ft and turn left 180 degrees to come back in and land.


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