About this Article
Written by: Jeff Moring
Written on: September 5th, 2005
Tags: aerospace engineering, security & defense
Thumbnail by: Wagner, Jr./U.S. Navy
About the Author
In the spring of 2005, Jeff Moring was a student in Astronautical Engineering finishing up his junior year at USC. He enjoys playing ice hockey in his spare time.
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Volume IX Issue II > Taking Off and Landing on an Aircraft Carrier
The aircraft carrier is the centerpiece of the United States Navy because of its ability to transport aircraft all over the world. The main component of these ships is their ability to launch and land jets in such a small space. But with so much chaos in such a small area, engineers have had to design simple yet effective devices to help manage the process. The catapult system is used for taking off, while the Fresnel lens and arresting wires are used to help the pilot land. These systems have been in place for several decades, and even though technology will improve drastically within the next 20 years, the future systems will continue to be based on these initial designs.

The Floating Airport

Wagner, Jr./U.S. Navy
Figure 1: The USS Nimitz is the current class of aircraft carriers that the Navy uses.
Aircraft carriers have been the centerpiece of the United States Navy since World War II despite the fact that their most basic and important function, launching and landing fighter jets on a ship in the middle of the ocean, proves to be a very difficult task. Due to the extremely limited runway space on the decks of these mobile machines, engineers have been forced to develop powerful systems to accelerate and decelerate aircraft in a very short period of time.

Ship Basics

The Navy currently uses Nimitz class aircraft carriers, which are typically 1,094 feet in length and have deck space of approximately 4.5 acres, the size of four football fields (see Fig. 1). Below deck the ships hold up to 80 aircraft, 6,250 people, 2 nuclear reactors, and all the supplies needed for tours that can last several months [1], [2].
In order for the aircraft carrier to act as a true traveling airport, the pilots and crew rely on three key elements to launch and land aircraft safely. First, four catapults are specially developed to launch planes at high speeds. Second, a lighting system known as the Fresnel lens, or the "meatball" system, lets a pilot know if the plane has the correct altitude and position when approaching to land. Third, four arresting cables are in place to bring the plane to rest in less than 320 feet [3].

Launching From A Catapult

Aircraft typically require long runways in order to gather enough speed so they can successfully take off. Since the runway length on an aircraft carrier is only about 300 feet [3], compared to the 2,300 feet needed for normal aircraft to take off from a runway [4], engineers have created steam-powered catapults on the decks of carriers that are capable of launching aircrafts from 0 to 150 knots (170 miles per hour) in just 2 seconds [5]. The takeoff system can be broken down into two components - the above ground and below ground operations.
Zaragoza/U.S. Navy
Figure 2: Blast Deflectors push harmful jet discharge into the air and away from the crew.

Above Ground

Above deck, the crew hooks the aircraft's front wheel, or nose gear, to the catapult using a tow bar. The tow bar hangs off the front of the nose gear so the catapult can pull the aircraft [2]. In order to prevent harmful jet discharge from going into unwanted places, a jet-blast deflector is placed directly behind the aircraft, pushing the discharge up into the air (see Fig. 2). The pilot then pushes the engine to full throttle, creating a forward thrust that would traditionally move a jet forward [5]. A holdback bar is in place to prevent any motion at this time, despite the thrust of the jet.
Once the force from the catapult is added to the thrust of the jet, the excess force will cause the hold-back bar to release and the jet will move [2]. This is because the hold-back bar can only hold the force from the jet at full thrust, but not the additional force of the catapult.