Boeing's Unmanned Little Bird can also fly with a pilot on board - and that makes the helicopter an ideal test asset for development work on other programmes

Boeing's Unmanned Little Bird (ULB) is a misnomer. The significance of this light helicopter is not that it is unmanned, but that it can also be flown manned. Near term, this provides the ability to test unmanned systems without the present restrictions on flying pilotless aircraft - longer term, it promises the capability to operate manned or unmanned depending on the mission.

The ULB takes its name from Boeing's A/MH-6 Little Bird, a military version of the MD Helicopters MD 530F used only by the US Army's 160th Special Operations Aviation Regiment. First flown in September 2004, the single-turbine helicopter had logged more than 450h flying with a safety pilot on board before it made its first unmanned flight at the end on June.

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Both images © Boeing 

 ULB demonstrator lifts off for its first unmanned flight on 30 June

Little steps

"It looked like a huge leap, but we had taken a lot of little steps, adding incremental capability," says Dino Cerchie, ULB programme manager at Boeing's rotorcraft division in Mesa, Arizona. "We could work control, sensor and communications integration separately because it was manned, and was safe to fly while doing the unmanned systems work."

In contrast, Boeing argues, unmanned air vehicle manufacturers usually have to solve the complete system integration problem before they can begin flying - and secure approval to fly in civil airspace, a lengthy process that is proving to be a bottleneck for UAV development. "When we do technology development, we have a safety pilot on board," says Cerchie.

The significance of this flexibility is only now becoming clear as the ULB begins to be used by other Boeing programmes, and sensor providers, as a low-risk testbed for unmanned systems development. "We can do some interesting stuff with high-end sensors that UAVs will not get to look at for several years," says Cerchie. "The risk is no different to flying on a manned aircraft."

The ULB also spearheads Boeing's work on unmanned rotorcraft systems, which includes programmes to demonstrate a 40h endurance with the A-160 Hummingbird rotary-wing UAV and to field the capability for manned/unmanned teaming by enabling the crew of the upgraded Block III version of the US Army's AH-64D Apache Longbow attack helicopter to control a UAV.

While the ULB is a commercial 530F modified to act as testbed for unmanned helicopter technology, Boeing is now completing two new-build A/MH-6Xs - prototypes built for manned and unmanned operation. Due to fly in September, these take the company a step closer to offering both a manned/unmanned Little Bird and a kit that would allow optionally piloted operation of other helicopters.

Fly by wire

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 Based on an MD 530F, ULB is now being used as a test asset
Boeing's concept with the ULB was to take an existing helicopter and use available civil-certificated and military-qualified parts to produce an unmanned aircraft. Fly-by-wire actuators were installed on the 530F's mechanical flight controls. These operate in parallel and when engaged move the pilot's controls, says Cerchie. The flight-control computer (FCC) and air-data, GPS and inertial sensors are mounted in the rear cabin where they are easy to access.

The ULB is capable of fully autonomous operation, with the safety pilot monitoring the system. The transition between unmanned and manned takes less than a second, and the pilot took back control several times during expansion of the flight envelope, says Cerchie. The cockpit was modified with a touchscreen to enable the pilot to access the FCC in flight. "He was able to disengage the flight control system and fly manually, change the gain and re-engage the system," he says. "It took just three days to do the software to define the flight envelope."

A Wescam electro-optical/infrared sensor can be carried under the nose, its signal processor mounted in the rear cabin. There is also a 1553B databus recorder, which Cerchie says has proved useful for health monitoring. A second crewmember can fly as a sensor operator, and there is a fold-out screen for sensor control on the left side of the cockpit. The standard Little Bird weapons "plank" is bolted to the cabin floor, and the ULB has demonstrated autonomous gun and rocket firings and Hellfire missile launches, but with the safety pilot on board.

Before its first unmanned flight in June, the ULB had completed more than 250 autonomous take-offs and landings. During the 20min flight over the US Army's Yuma Proving Ground in Arizona, the helicopter took off, hovered briefly, flew a programmed armed reconnaissance mission and landed back within 150mm (6in) of the planned recovery location. "After the unmanned flight, the pilot flew it back to Mesa, which shows the manned/unmanned deployability aspect," says Cerchie.

The ULB is now being employed as a test asset, most recently being used for flight testing on a brown-out sensor under development for manned helicopters. "It's heaviest use will be as a test asset, which is what it was planned for," says Cerchie. The ability to fly autonomously with a safety pilot on board allows the aircraft to be used for high-risk testing of expensive payloads, "some of which cost more than the helicopter", he says. Getting permission to fly is also easier: "We have done high-risk testing and been approved in a day, versus a year," he says.

Development of the optionally piloted system will now shift to the two company-funded A/MH-6Xs nearing completion at Mesa. Originally planned as prototypes for Boeing's unsuccessful bid for the US Army's Armed Reconnaissance Helicopter programme, these aircraft are based on the A/MH-6M Mission Enhanced Little Bird operated by the 160th. Changes include a six-blade main rotor and uprated, digitally controlled Rolls-Royce 250-C30R/3M engine that increase payload by 360kg (800lb) over the ULB demonstrator.

The A/MH-6X is designed for manned/unmanned operation and the flight control system has increased redundancy. There is a new cockpit for manned operation, with two multifunction displays, and unmanned capability is built in - it comes "for free", says Cerchie, as the FCC is also used as the autopilot in manned operation, and will reduce pilot workload. The A/MH-6X will be flown initially by a safety pilot, then operated autonomously from a ground station using an open mission management system developed by Boeing. This will allow the helicopter to be operated from any NATO-standard ground station, he says.

While there is as yet no military requirement for a manned/unmanned Little Bird, Cerchie says, "we see a market if we project out a couple of years, and Boeing is willing to take the risk". Boeing vice-president and rotorcraft division general manager Mike Tkach agrees: "We have got to spend time maturing it. If we build a good product, they will buy it."

Meanwhile, the ULB will continue as a research tool. Earlier this year, the helicopter was used to demonstrate control of a UAV from an AH-64D as part of the Block III upgrade for which Boeing has just signed a $619 million development contract.

Apache plans

Scheduled for production beginning in 2011, the Block III Apache will be the first helicopter capable of Level 4 control of a UAV and its payload. While demonstration of manned/unmanned teaming continues, the US Army is already developing procedures to allow Apache crews to control its new General Atomics Warrior extended-range, multi-purpose UAV, a derivative of the fixed-wing Predator.

Boeing is also continuing work on the rotary-wing equivalent of the Predator, the A-160 Hummingbird. This unmanned helicopter demonstrator uses an "optimum-speed" rigid rotor that can vary its rpm over a range from 50% to 100% to provide extended endurance. Designed to hover efficiently at 15,000ft (4,570m), and cruise at up to 30,000ft, the A-160 has flown for a maximum 12h so far, and Boeing plans to demonstrate 24h by early next year after installation of a new powerplant - either a larger Subaru gasoline engine or a Pratt & Whitney Canada PW200 turbo­shaft. Plans call for the target of 40h endurance to be achieved after installation of a diesel engine.

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Source: Flight International