Sailors reconnect an arresting gear wire on the flight deck of the aircraft carrier USS Harry S. Truman (CVN 75).
YOU HAVE TO KEEP IN MIND THAT THE LIVES OF THE CREW AND GROUND CREW ARE DEPENDING ON THIS ROPE PERFORMING SAFELY.
U.S. Navy photo by Mass Communication Specialist 2nd Class Lyle H. Wilkie III/Released. Because of their specialized design and use, both WireCo®
ropes are tested to military specification, and are considered Critical Safety Items. “Tere are both Defense Contract Management Agency and Lakehurst Quality inspectors that witness portions of the manufacturing tests,” Scholl adds. “Testing of the components of wire, cordage, and the finished wire rope are done to qualify the product for government acceptance. You have to keep in mind that the lives of the crew and ground crew are depending on this rope performing safely.” And if you’ve ever seen a carrier deck in action while planes
are landing and taking off, a couple of things are immediately noticeable: this job is extremely dangerous for everyone involved, and this arresting system needs to be extremely precise in every way. Essentially, the system is made up of the wire rope hook cables (pendants), purchase cables (tapes), sheaves, and arresting engines. Te ends of the cable can actually be detached quickly, for replacement—equipped with terminal couplings (cables can be changed out on a carrier in two to three minutes). Wire supports—which are simply flexible, curved steel leaf springs— raise the pendants a few inches so they can be more easily hooked by a landing aircraft. A “donut” support is used to raise the cable on a land-based arrest system—usually a minimum of two inches.
Connected to the arresting cable is the purchase cable. Tese
wires are much longer and are not easily removed. Tere are two purchase cables per arresting cable—on opposite ends of the wire. When the aircraft engages the pendant with its tailhook, the purchase cables “pay out” by transmitting the force of the landing aircraft from the arresting gear to the arresting engine. Te purchase cables run through “sheaves,” either within the flight deck or along the runway—to the arresting engine. Tese sheaves serve as a hydraulic shock absorber that accommodates the landing speed of the aircraft. Every pendant (deck cable) has its own engine system that absorbs and dispels the energy accumulated when an aircraft lands. Aircraft carriers use what is known as a hydro-pneumatic system—oil fluid is forced out of a cylinder by a ram connected to a purchase cable. Te fluid is pushed through a control
valve—a system described as the “constant runnout control valve”—whereby any aircraft, regardless of weight or speed, can be stopped with the same amount of runnout. Te constant pressure for arresting gear is set at about 400 pounds per square inch, and this constant runnout valve actually stops the aircraft, rather than hydraulic pressure. As the aircraft assumes its approach, its weight is recorded by the arresting gear engine operator— having received it from Primary Flight Control. Te constant runnout control valve is then adjusted to the setting for that particular aircraft, and the system all but takes care of itself. Trough the years, carriers, and their amazingly efficient systems, continue to evolve. Scholl has noticed an increase in rope size as jets get bigger and faster, and even sees the deck cable’s role changing in time. “Eventually, synthetic (polymer) rope may be used. Te use of other types of planes that do not need a runway will also reduce the need for arrestors.” Until then, the arresting system itself is about to get a major facelift. Te USS Gerald R. Ford (CVN 78), is expected to join the Naval fleet in 2016, and will be fitted with the newest system—the Advanced Arresting Gear (AAG). Tis high-level system will employ the most technologically proficient digital arresting components and controls on the planet—and is designed to recover aircrafts of any size. Te AAG’s benefits will be numerous, and will set a new standard with built-in test and diagnostic capabilities—providing for less operational maintenance and manpower, and increased safety and reliability. In the modern age, perhaps nothing is more advanced than
an aircraft carrier. And these floating cities of maintenance and might would certainly have an entirely different purpose if it wasn’t for a familiar piece of twisted steel that most of us have come to know simply as, wire rope. y
WIRE ROPE EXCHANGE SEPTEMBER-OCTOBER 2014 23
Aviation Boatswain’s Mate 3rd Class Shantell Robinson monitors arresting gear pressure gauges.
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