SciTech

How Things Work: Aircraft Carriers

Taking off from an aircraft carrier requires more than just radio communication between a pilot and ground crewmen — it takes the mechanical power of massive catapults and fast-acting braking systems.

Aircraft carriers have enough engine power to launch one airplane every 25 seconds.

The most important component of an aircraft carrier is the flight deck, or the landing and launching strip. Because the flight deck is so short, pilots and ground officials must keep close watch over all aircraft that are located on the carrier and flying around the ship.

U.S. aircraft carriers belonging to the Nimitz class of carriers have a runway that is just over 300 meters long; for comparison, the runway at John F. Kennedy International Airport in New York is about 4400 meters long. In addition, Nimitz aircraft carriers have a flight deck that is about 250 feet wide, and they are capable of traveling at 34 miles per hour.

Nimitz aircraft carriers also consist of a hangar deck, island, and power plant. The hangar deck is the area of the ship where stationary planes are kept. Planes are also repaired in the hangar deck, and they are transported to the flight deck by giant elevators.

The  island, the building where officials regulate the movement of aircraft on and around the ship, is located on top of the hangar deck. Crew members in the island also steer the carrier.

The lower decks, on the other hand, contain machinery that powers the carrier. The engine pushes the ship forward with propellers.

The hull — or main body — of a Nimitz aircraft carrier is made of steel that is thick enough to protect the carrier against fire damage. The bottom of the vessel consists of two layers of steel to protect the ship against torpedo attacks.

For a plane to take off from an aircraft carrier, it must acquire enough lift force to take off from the short flight deck. Some of this lift force is produced by the wind, but most comes from on-board machinery. To generate lift, planes are launched by four catapults on the ship’s flight deck. The catapults are powered by pistons that are housed inside cylinders.

Prior to takeoff, the plane’s front wheels are attached to the catapult’s shuttle, or the part of the catapult that sits on the flight deck’s surface. Once the plane is prepared for takeoff, the catapult’s cylinders fill with steam. The steam creates a region of high pressure inside the cylinders. Eventually, the pistons unlock, and the catapults launch the plane forward.

Under the force of these catapults, it takes three seconds for planes to accelerate from zero to 150 miles per hour.

Similar to takeoff, landing an aircraft involves the work of several machines aboard the ship, in addition to monitoring by ground crewmen.

To land a plane, the pilot flies over the flight deck and attaches a hook on the plane to a steel wire on the ship, called the arresting wire. The arresting wire is attached to a hydraulic system that slows the plane down. It can stop the plane in a distance of 300 feet. There are four such wires on the ship, but pilots always try to catch the third wire because it’s safest.

Furthermore, because the landing strip is so short, landing a plane requires close communication between the pilot and ship crew.

When multiple planes await landing, they fly in an oval formation. One by one, air traffic control gives the planes clearance to land.

If a plane is not on target for landing, the landing signal officer (LSO) can use radio or light signals to redirect the plane. The LSO can request that the plane abort a landing attempt.

Pilots are also directed to the flight deck by the Fresnel Lens Optical Landing System (FLOLS). FLOLS is a collection of lenses that produces light beams at different angles. The different lights beams inform the pilot about his or her position relative to the aircraft.

In particular, if the pilot sees an amber light in line with a series of green lights, then the plane is correctly aligned with the runway.

However, if the amber light appears to be out of line with the other lights, then the plane is misaligned with the runway.
If the plane doesn’t catch one of the arresting wires upon landing, then the plane takes off again from the ship. As a safeguard, when the plane lands, it immediately turns its engines to full power.

If the plane successfully catches the arresting wire and comes to a stop, it is moved to the side of the landing strip.

While accidents involving aircraft carriers are rare, crew members can be thrown overboard by a jet engine or be injured by onboard mechanical failures.

In 1995, a sailor was killed on a U.S. aircraft carrier during a maintenance procedure. The crew member was maintaining the hydraulic system for one of the arresting wires when one of the piston caps flew out at him.

To help prevent injury during landing, aircraft carriers are equipped with fire trucks and tanks of water. Crew members also wear inflatable coats in case they are thrown overboard. The jackets have lights on them for search and rescue.