So how does one park a 20,000-pound aircraft travelling 130 knots on the roiling deck of the USS Ronald Reagan? Very careful aim, and the incredible assistance of Mark 7 Mod 3 arresting gear.
Simply, arresting gear is the mechanical system designed to quickly halt an aircraft as it lands. The US Navy's current system—the Mark 7 Mod 3—can stop up to a 50,000-pound plane moving at 130 knots in just 340 feet, and in just two seconds. It can absorb up to 47,500,000 foot-pounds of energy (64.4 MJ).
The arresting gear comprises two parts: the cross deck pendant (also known as the arresting wire) that lays across the deck, and the arresting cables and gear which are located below deck. There are typically four arresting wires laid across the deck, spaced out about 50 feet apart. Pilots generally try to aim for the third wire, as it's the safest; the first wire sits dangerously close to the stern of the carrier, though the second and fourth wires are acceptable. Regardless of which wire the pilot snags on his 8-foot long tailhook, the arresting wire system is designed to consistently stop planes at the same spot.
The arresting wires themselves are up to 35mm thick, consisting of wire strands twisted around an oiled hemp center core (which keeps them lubricated). Each of these cables can be replaced in about 2 minutes if necessary and are swapped out every 100 captures for maintenance.
Connected to the arresting cables are two 1100-foot wires that run from the deck, down to each arresting gear engine (one engine per arresting wire, so generally four engines per carrier). As the plane lands, it snags onto the arresting cable. Once the wire is yanked, it pulls on a metal rod that presses a plunger into a cylinder filled with hydraulic fluid. This forces the fluid through a valve that meters the flow depending on the weight of the landing aircraft.
Once past the valve, the fluid collects in another cylinder known as the accumulator. This cylinder is also fitted with a plunger and, as the cylinder fills with fluid, it compresses the air to 650 psi. At that point, the fluid valve will automatically close, preventing the accumulation chamber from filling further and arresting the cable.
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