By John McHale
RANCHO BERNARDO, Calif., 23 Dec. 2009. The Fire Scout unmanned helicopter from Northrop Grumman Aerospace Systems in Rancho Bernardo, Calif., uses commercial-off-the-shelf (COTS) avionics for its flight control system (see related story entitled U.S. Navy avionics systems integrators embrace open architectures to combat parts obsolescence).
The Fire Scout's avionics are similar to those of manned systems, says John VanBrabant, Fire Scout domestic maritime business development manager at Northrop Grumman Aerospace. The main exception is with redundant vehicle management system that has a vehicle management computer (VMC).
The unmanned aerial vehicle (UAV) is autonomous with a pre-programmed mission, VanBrabant says. The operator onboard ship or the ground can take over with the click of a mouse, but otherwise it flies on its own, he adds.
The flight control system is separate from the UAV payload system to enable payload changes without recertifying flight-control software, VanBrabant says. "The Navy has spent a lot of money on software development and wants to reuse as much as possible," he adds.
Northrop Grumman designed the system to uses as much COTS equipment as possible and use an open architecture to manage component obsolescence, VanBrabant says. The COTS vehicle management computer and other parts of the avionics are designed and produced by GE Fanuc Intelligent Platforms in Charlottesville, Va., VanBrabant says.
In the case of Fire Scout, GE Fanuc also supplies a payload interface computer and the router/switch for each Fire Scout, explains says Peter Cavill, general manager of military & aerospace products at GE Fanuc.
"The VMC is a self contained digital computer containing processors, memory, input/output circuits, and associated support circuits required to perform the flight control and vehicle management functions," Cavill says. "The VMC is intended to function within a dual redundant vehicle management system (VMS), with one additional identical VMC operating in frame synchronous fashion, providing fault-tolerant control of UAV flight control and subsystems. Each VMC includes cross channel data links (CCDL) for the exchange of input signals.
"The Vehicle Management Computer (VMC) functions as the core computational and control element within a redundant control system on critical airborne platforms," Cavill continues. "The VMC performs functions critical to flight safety including guidance and navigation, flight path, and vehicle stability control, and vehicle subsystems control."
The compact VMC has six 3U CompactPCI slots, makes use of a single-board computer with a PowerPC 750/755 400-500 MHz processor, and support for the Wind River Systems VxWorks and Green Hills Integrity real-time operating systems (RTOSs), Cavill says.
The computer also "interfaces with aircraft sensors, inceptors, actuators, and utilities/subsystems equipment primarily via high speed serial data networks," he explains. "The VMC performs the core flight control computing and failure monitoring functions while relegating the bulk of input/output interfacing to Remote Input/Output Units (RIU), which are also components of the VMS.
The UAV performs an autonomous landing through its UAV common automatic recovery system (UCARS) from Sierra Nevada Corp. in Sparks, Nev., VanBrabant says. At the end of its mission it will hover behind the ship, wait for a signal from the ship to land and use its instruments to determine the speed of the ship and its pitch and position in the water to make a proper landing, VanBrabant explains.
These are all actions that a pilot would normally make using instinctive visual cues, VanBrabant says. With a UAV the system must be completely preprogrammed to perform those functions automatically, he adds.
According to the Sierra Nevada website "he UCARS-V2 was developed to provide day/night, all-weather, automatic landing and takeoff capabilities for unmanned aerial vehicle (UAV) systems operating from shipboard and/or fixed-base land environments. The UCARS-V2 is a direct descendent of the UCARS UPN-51 system that is in service today with the U.S. Marine Corps Pioneer UAV. The UCARS-V2 consists of two primary components: a ground based radar track subsystem (TS) and an air vehicle mounted airborne transponder subsystem (AS). UCARS-V2 can also provide an automatic take-off capability for both fixed and rotary wing UAVs. UCARS-V2 has been integrated to perform automatic take-off and/or landing operations on numerous different UAS."
The Fire Scout is currently flying off of a U.S. Navy guided-missile frigate -- the USS McInerney -- and performing naval operations in the Pacific Ocean and Caribbean Sea, VanBrabant says.
According to Northrop Grumman data sheets the system is based on the "Schweizer Model 333 manned helicopter, can autonomously take off and land on any aviation-capable warship and at unprepared landing zones in proximity to the forward edge of the battle area."
It is basically a unmanned version of the H-60 helicopter and primarily H-60 pilots are the operators of the Fire Scout, VanBrabant says.
Fire Scout's endurance exceeds eight hours and it can provide coverage 110 nautical miles from the launch site. The aircraft's tactical baseline payload includes electro-optical/infrared sensors and a laser pointer/laser rangefinder to help the system "find tactical targets, track and designate targets, accurately provide targeting data to strike platforms, and perform battle damage assessment," according to the data sheets.
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