When a pilot approaches an aircraft carrier, he is entering one of the most complex and least forgiving environments on Earth. Operations occur at hundreds of miles an hour, with a variable number of pilots, planes and deck personnel working on a bucking, wind-blown carrier deck. After a pilot radios his intention to land, air-traffic controllers either clear him for approach or direct him into a holding pattern. They also supply the pilot with weather and deck conditions. On the approach, the pilot typically relies on the landing signal officer (LSO) to guide him using light signals and visual cues. The air boss, an officer in the primary flight control tower, or PriFly, oversees the operation as well. Seconds before touchdown, the LSO makes a final landing determination, waving off the pilot for another try if the glide slope or course looks risky.
The process of landing planes on a carrier deck, called recovery, has not changed significantly since World War II, nor will it in the near future. The challenge, then, is how to fold the X-47B into a highly fluid human system without disrupting it. Engineers approached the problem in a few different ways. First, they automated much of the chatter that goes on between pilots and air-traffic controllers. Instead of verbally reporting fuel levels or altitude readings to air-traffic control, the aircraft beams that data directly over its link to the tower. Rather than relying on a verbal description of conditions, it downloads the carrier’s position, speed and pitch from sensors on the ship 100 times a second and adjusts its path to match.
Where direct communication between aircraft and human is unavoidable, designers translated verbal commands into a digital language. They started with the 100-plus-page carrier operations manual and boiled it down to 53 critical commands. Many involve taxi and takeoff, along with flight checks and other safety routines. Engineers then built a software interface that displays the commands. Working through the interface in the PriFly, air bosses can issue the same orders to the X-47B that they might to a pilot. The LSOs got a new tool, too. Designers updated the handheld device known as the “pickle,” which LSOs use to grant or deny final landing clearance, so that it can communicate directly with the X-47B.
The team also determined what would happen if communication were to break down. If the data link failed on approach, or the LSO waved off the X-47B from final landing, the craft would fly past the carrier and clear of other aircraft and settle into a wide loop that would bring it back around for another approach. If communication were irreparably severed, it would search for a terrestrial landing spot or, as a last resort, ditch into the ocean.
By the time the UCAS group developed the basic communication software and interfaces, the X-47B could technically have made a carrier landing. Even on a heaving carrier deck, researchers predicted, the margin of error during a landing would be within a few feet. The question was not whether the X-47B could work with people, but whether people could work with it.
In December 2011 the Navy shipped the X-47B to Patuxent River, known as Pax River. The test facility is one of two in the world with a mock carrier deck, outfitted with a steam catapult and arresting cables. Engineers also built simulation rooms for working out software bugs and training carrier personnel. One is a replica of the air-traffic control center, complete with radar screens and communication equipment. The other is a re-creation of the PriFly, where four flat screens display the same view an air boss might see.single page
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.