Flying an aircraft is not the simplest task but landing on the flight deck of a carrier is one of the most difficult tasks a naval pilot ever has to do. Most decks are only around 150 meters long and pretty narrow. For traditional landings, this is far shorter than what would normally be needed. Especially for high-speed jet fighters. So how do pilots land on aircraft carriers?
Pilot skill is an important factor but what technology is employed to help them? Most planes come equipped with tailhooks that snag arresting wires on the flight deck. Sounds simple enough, but how exactly do these work? Let’s take a quick look.
[Image Source: Wikimedia Commons]
Land on aircraft carriers might seem routine today, but it is far from easy. The pilot needs to line up the plane and approach the ship from the right angle. But before all of this, landing tends to start with airborne planes “stacking up” in a huge oval flight pattern around the carrier. This is all coordinated by the ship’s Air Traffic Control Centre. These chaps decide the landing order of the waiting planes, generally based on their respective fuel levels. Those running on fumes obviously take priority. Once given the all clear to land the pilot begins to make their approach.
Landing signal officers (LSO’s) help guide the plane in via radio communication as well as lighting on the carrier’s deck. All of these measures are combined to make sure the pilot is on the correct approach direction and angle of “attack”. If they are off, the LSO can correct them or “wave them off” to abort and retry.
The pilot also takes cues from the Fresnel Lens Optical Landing System, or “lens”. These consist of a series of lights and Fresnel lenses that are mounted on gyroscopic stabilizers. They focus light into narrow beams that are directed into the air at varying angles.
The pilots will see these lights on approach and depending on their angle of attack they will see different colors. If they are on the right approach, they will see an amber light in line with a row of green lights, called the “meatball”. If the amber light appears above the green lights, the angle is too high and needs correction and vice versa. Red lights will immediately tell the pilot he is way too low. These systems are nothing new, here is an information video from the cold war era.
Hit the deck
As previously mentioned the aircraft has a tailhook that is deployed prior to landing. This is a vital component in the process of being able to land on aircraft carriers. As soon as the plane touches down the pilot will push the engines to full power to stop the plane. This may seem counterintuitive, but if they fail to snag a wire, they will need to be able to get airborne again pretty sharpish. The landing runway is also in a slight elevation, about 14 degrees, to the rest of the ship. This lets a failed landing aircraft get airborne again without smashing into other planes on the deck.
Landed aircraft are pulled off the landing strip and either stored below decks or chained down on off to the side of the deck. Inactive planes are always securely stored to prevent issues when waves roll the ship.
Obviously, the tailhook needs something to snag. Enter the arresting wires (well cross deck pendant). These cables are made from sturdy high-tensile steel woven together and tend to be around 35mm thick. These cables are connected to a set of hydraulic cylinders below deck. The principle is pretty simple really. When the tailhook snags a wire, the wire is pulled along with the hook and plane. The hydraulic cylinders absorb massive amounts of energy to slow down the landing aircraft dramatically, eventually to rest. Amazingly, these wires are able to stop a 25,000 kg plane traveling at 240 km/h in less than 2 seconds or roughly 96 meters. Wow.
Usually, there are multiple cables and cylinder setups at the start of the landing pad. They tend to be spaced about 15 meters apart to give the pilot as large a touchdown area as possible. Apparently, the pilot tends to aim for the third wire as it is the safest and easiest to snag. Aiming for the first wire could bring the plane too close to the rear of the deck. If they came in too low, they risk smashing into the stern of the ship.
The actual arrestor gear is made up of two parts. The cross deck pendant (the wires) which connect to the sub deck cabling, gears, and cylinders. The cross deck pendant connects to 335-meter cables that run from the deck to the arresting gear engine. Each top deck cable has one gear engine, so each aircraft carrier will have a varying number of setups. Once the cable is pulled, a metal rod presses a plunger into a cylinder filled with hydraulic fluid. This then forces fluid through a valve that meters the flow depending on the aircraft’s mass and speed.
Once the fluid passed the valve it enters another cylinder called the “accumulator”. Here a plunger separates air from the entering fluid. As the accumulator fills with fluid, the plunger compresses the air to around 650 psi. At this point, the valve automatically closes and prevents further air compression. This in turn stops or arrests the cable and stops the plane letting it land on aircraft carriers. Neat right?
The final word
Amusingly, Squadrons tend to have ranking systems, “Greenie boards”, that they use to mark pilots on their landings. Generally speaking, it is acceptable to snag the second or fourth wires but catching the third wire consistently is the mark of a good pilot.
So there you go. This is how planes land on aircraft carriers. Well, it takes a combination of skill and engineering of course. A mixture of training, visual and audio instructions, hooks and cables and hydraulic systems all come together to safely slow down a fast moving plane. Incredible really.