PALMDALE, Calif. – Northrop Grumman and the U.S. Navy are devising a series of control devices, visual aids and protocols to enable the X-47B unmanned combat air system (UCAS) demonstrator to operate seamlessly alongside manned aircraft within the confines of an aircraft carrier flight deck, as well as in its airspace.

Some of the innovations were shown during ceremonies marking the rollout of the first X-47B at the company’s site here on Dec. 16. The first air vehicle, AV-1, is scheduled to make its first flight on Nov. 11, 2009, while a second demonstrator, AV-2, will be completed around December 2009. Both will be used to demonstrate the viability of carrier operations with an unmanned combat aircraft, with the first X-47B carrier landing expected in November 2011.

Following first flight, AV-1 will undergo a yearlong envelope expansion test period at Edwards Air Force Base, Calif., before being ferried across the country to the Navy’s test center at Naval Air Station Patuxent River, Md.

That phase will focus on working up to carrier demonstrations and will include catapult certification tests at Lakehurst Naval Air Engineering Station, N.J. Further tests will also include a period at Norfolk, Va., where it will be craned onto the deck of a Nimitz-class carrier for dockside taxi trials. A final phase of carrier workup tests at Patuxent River will be followed by a November 2011 landing on a carrier while at sea. This is likely to be the USS Harry S. Truman (CVN 75), which “right now looks as if its going to be in the right place at the right time,” says Capt. Martin Deppe, N-UCAS program manager.

Carrier suitability work will assess methods for controlling the unmanned aircraft both in the air and on the deck. Last summer, two high-profile Center for Strategic and Budgetary Assessments analysts launched a campaign to warn Washington that the Navy’s bureaucracy appeared to be on its way to dooming the nascent N-UCAS effort by rolling back its demonstration program (Aerospace DAILY, June 24). Bob Work and Tom Ehrhard said a carrier deck demo was critical to gaining adoption from the naval aviation community.

Best approach

Deppe says the “best approach is to have somebody taxiing it around by itself.” UCAS squadron personnel would watch the aircraft directors, or “yellowshirts” as they are usually nicknamed, and stand behind them controlling the aircraft on the deck using a hand-held remote control device. This could be a particularly crucial aspect of the suitability trial, as the role of the yellowshirts is vital to the safe and smooth functioning of the crowded flight deck. There are typically about 12-15 yellowshirts on deck during standard flight operations or during a “re-spot” when aircraft are moved. “We don’t want to have two or three people trying to control the same aircraft,” Deppe adds.

A series of nose-leg mounted lights will indicate the readiness of the X-47B to deck crew. A green light will show it is under control of the deck handlers and a blue will indicate it is under control of mission operators, while a red indicates a fault.

The UCAS will approach and land autonomously using the Joint Precision Approach and Landing System ship-relative GPS-based landing system. As with all other aircraft, the UCAS will be monitored on its approach by the Landing Signal Officer (LSO), an experienced pilot with responsibility for the visual control of aircraft on short finals. If a UCAS appears to be approaching incorrectly, or the landing area is not clear, the LSO will be able to “wave off” the landing by releasing an interlock switch. This will digitally signal the UCAS to add power and execute a climb straight ahead to 1,200 feet and wait for instructions from approach control, or follow pre-programmed directions.

The X-47B will have a maximum takeoff weight of 45,000 pounds but a max landing weight of around 35,000 – 36,000 pounds, similar to Northrop’s A-6. Touchdown speeds are expected to be in the 120-130 knots range, depending on weight and windspeed.