Page 1 of 1
For most air vehicles, first flight is typically the milestone that holds the greatest significance. Not so for the Navy’s Fire Scout Vertical Takeoff and Landing Tactical Unmanned Aerial Vehicle (VTUAV). For it, the far more historic event happened in mid-January off the coast of Naval Air Station Patuxent River, Maryland when two RQ-8A Fire Scouts completed nine fully autonomous shipboard landings on board USS Nashville. During the two-day test two different Fire Scouts were used, which logged over nine total flight hours during the ship landings and takeoffs (Figure 1).
The test was ground breaking because it marked the first time a UAV performed vertical landings on a moving ship without a pilot controlling the aircraft. The Fire Scout has proved itself as more autonomous than any other tactical UAV that’s out there flying now, according to Cmdr. Rob Murphy, the Navy’s VTUAV integrated product team leader. “Because it flies on and off board ships, there’s an added level of complexity and decision making that the mission plan has to take into account. There’s no fixed landing point, so rather than flying based on GPS waypoints, the air vehicle instead returns to the area of the ship and commences to follow a relative flight plan based on its proximity to the ship.”
For typical aircraft landing—whether rotary or fixed-wing—on a runway or any prepared site, an aircraft gets to rely on level ground that isn’t moving. The vehicle knows how far away it is from its touchdown point. But when landing on a ship, you have to factor relative motion into the equation. The air vehicle not only must translate its closure rate to the landing spot in a different way, it must also take into account winds over the landing spot, including the “wind burble” that’s created by the superstructure of the ship.
Autonomous Landing a Complex Challenge
While an air vehicle landing on a fixed-site need only orient its landing path into the wind, landing on ship requires the UAV to make corrections based on the relative motion of the ship. On top of all that, throw in the unpredictable nature of a flight deck at sea—the pitching, rolling and heaving of the deck—and the problem become even more of a challenge. The pitching and rolling deck presents a challenge because the aircraft won’t be landing flat as it would on a fixed runway, so that typically one skid will touch down higher than the other. To ensure a normal safe landing, the system has to adjust the gains so that the power was taken off the aircraft in the correct proportion to weight being applied to the skids.
All that complexity requires a level of embedded computing power beyond that of any previous UAV. The Fire Scouts that flew in the January test were RQ-8As, which are a test version of the newer MQ-8B Fire Scout being developed by Northrop Grumman for the Navy and the U.S. Army. The MQ-8B Fire Scout is the aircraft element of a complete system called the Vertical Takeoff and Landing Tactical Unmanned Aerial Vehicle (VTUAV) system. After it was launched from the naval air station, the Fire Scout flew to the designated test area, where the USS Nashville was waiting for the air vehicle to land and take off under its own control. The flight was monitored from a ship-based control station called a tactical control system, and the air vehicle was guided onto the ship using an unmanned air vehicle common automatic recovery system.
Second-Gen Fire Scouts in Development
Northrop Grumman is in the process of developing the second-generation Fire Scout, the MQ-8B, the first two of which were delivered in February to the company’s new Unmanned Systems integration center in Mississippi. They are being integrated and are expected to fly before the end of this year. In contrast to the RQ-8A version, the MQ-8B brings a fourth blade and an increase in gross weight from 2,600 to about 3,100 lbs. Most of added the weight is for payload. The MQ-8B version also provides for a longer endurance, which meets the Navy’s key performance parameter of launch, proceed 110 nautical miles, stay on station 5 hours and return.
The Fire Scout has been selected by the Navy as its Vertical Take Off and Landing Unmanned Aerial Vehicle for its new Littoral Combat Ship. In fact, the UAV has become a key enabler for that ship, and the LCS program is now a primary customer of the Navy Fire Scout. The missions are anti-submarine warfare, surface warfare and mine warfare, and Fire Scout has payloads that will contribute to all of those missions. The original vision for the Fire Scout VTUAV when it was started a couple years ago was for it to be used on an air-capable ship. To serve that need, the Navy and its program partners designed roll-on/roll-out shelters to provide the portable ground control stations for the Fire Scouts. With the advent of the LCS program, the ground control stations will be integrated and resident directly on the LCS ships.
Embedded computers and the payload interface unit aboard the MQ-8B are 3U CompactPCI boards supplied by SBS Technologies. Offering size, weight and power advantages compared to 6U VME, 3U CompactPCI has become a popular choice for UAV designs. Also on the air vehicle are three Rockwell ARC-210 Radios, with a growth path that accommodates substituting those for JTRS Radios when they become available. Rounding out the onboard avionics are Raytheon’s Tactical Control System (TCS) and BAE Systems’ IFF (Identification Friend or Foe) system. The Unmanned Combat Automatic Recovery System, residing on the ship, is supplied by Sierra Nevada Corp.
Army Fire Scout for FCS
The Army has also selected Fire Scout for as its Class IV UAV for its Future Combat Systems program. For the Army Fire Scout, Northrop Grumman provides just the air vehicle for Boeing and SAIC—the Lead System Integrators for FCS—while Boeing does the avionics, including a different control system than the Navy version and a different datalink. Although Fire Scout isn’t technically a Joint Army/Navy program, the two branches are cooperating closely on it. An Army Lt. Col is embedded in the Navy program office (PMA). Eight Army Fire Scouts are under contract, with about one to be delivered per month for integration, starting last month. But while the Navy Fire Scouts are scheduled to go into services in FY 2008, the Army Fire Scouts, for now, will have to go into storage until the Future Combat System program can make use of them.