Imagine an upgrade that leaves an aircraft's cockpit and avionics unmodified, but completely swaps out the airframe. Not a scaling up, as with Boeing's F/A-18E/F Super Hornet fighter, but a switch to a different air vehicle from a different manufacturer.

That is what Northrop Grumman and the U.S. Navy have done with the Fire Scout ship-based vertical-takeoff-and-landing unmanned aircraft system, developing the 6,000-lb.-gross-weight MQ-8C air vehicle, based on the commercial Bell 407 light helicopter, to replace the 3,200-lb. MQ-8B, which is based on the Sikorsky/Schweizer S.333.

The air-vehicle change, to increase the endurance and payload of the Fire Scout and enable longer-range maritime intelligence, surveillance and reconnaissance (ISR) missions, justifies use of the term unmanned aircraft system and illustrates the flexibility available to designers when the cockpit is separated from the airframe and connected only by data links.

Northrop and the Navy are targeting the end of 2014 to have the extended-endurance Fire Scout ready for deployment on DDG-51 Burke-class destroyers to support special-warfare units operating under U.S. Africa Command. The MQ-8C had its first flights from NAS Point Mugu, Calif., Oct. 31, barely 18 months after award of the $154 million rapid-development contract.

The MQ-8C is being fast-tracked to meet an urgent operational requirement from Africom to provide longer-range maritime ISR from ships than can be performed by the in-service MQ-8B. The basic requirement is to fly to a radius of 150 nm and remain on station for 8 hr. carrying a 300-lb. payload, says Capt. Patrick Smith, Navy Fire Scout program manager.

The Bell 407 has been modified with a more-powerful 700-shp Rolls-Royce M250-C47E engine and increased fuel capacity, giving the MQ-8C twice the endurance and three times the payload capacity of the -8B. But the unmanned avionics, payloads and ground control station are carried over from the -8B, with 80% software reuse, says George Vardoulakis, Northrop Grumman vice president for medium-range tactical systems.

The MQ-8C has a maximum endurance of 12 hr., a maximum internal payload of 1,000 lb. and an external sling load of 2,600 lb. The Navy is switching Fire Scout procurement to the -8C, which at an average unit cost of $11.8 million for the initial 12 aircraft, is $1.5-2 million more expensive than the -8B, says Smith. But, he adds, the Navy “will be able to replace two Bs with one C” for cost savings.”

The Navy will receive two more MQ-8Bs, for a total of 23, then take delivery of a planned 28 -8Cs to meet the urgent operational requirement. “We plan to procure MQ-8Cs beyond the 28 for future LCS [Littoral Combat Ships],” he says. The MQ-8B is deployed operationally on FFG-7 Perry-class frigates and is intended to be the initial version of the Fire Scout to deploy on the LCS, planned for early 2015.

A second test aircraft was to arrive at Point Mugu last week. The initial stage of testing is envelope validation, says Vardoulakis, to confirm the MQ-8C flies the same as the Fire-X demonstrator, built and operated by Northrop and Bell ahead of contract award. “In December/January, we will go into payload integration flights. The Navy has identified several payloads,” he says. Beginning with land-based tip-table tests, the program will then work up to dynamic interface trials with a DDG-51 in the first half of next year to meet the early operational deployment target of year-end 2014. Initial operational capability on the LCS is planned for 2016, Smith notes.

On its Oct. 31 first flight, the MQ-8C flew autonomously for 7 min., hovering for 5 min. at 50 ft. to assess rotor track and balance. The plan was to land, check the data with the engine at idle, then launch again to transition into forward flight. But on landing, Vardoulakis explains, the two weight-on-skid switches activated 8 sec. apart instead of simultaneously as expected. So the engine was shut down and switch gaps were adjusted. The aircraft was then launched on a second, 9-min. flight around the airfield pattern, to an approach and landing.

“Because we shut down the engine, what was planned as a single flight was logged as two,” says Smith. “We did the entire mission test card as planned,” says Vardoulakis, adding that the aircraft landed squawk-free and ready for its next scheduled flight.