Aviation Week & Space Technology, Jul. 26, 2010, p. 59


Web headline: Pilot Report On Hawker Beechcraft AT-6B

Low-Cost CAS COIN Candidate

Hawker Beechcraft modifies its popular trainer in answer to a USAF call for a light-attack aircraft

By Fred George Wichita, Kan.

Hawker Beechcraft Corp. is morphing its T-6B Texan II military trainer into the AT-6B, a welterweight contender in the U.S. Air Force's upcoming Light-Attack and Armed Reconnaissance (LAAR) competition. The attack variant utilizes a beefed-up T-6 airframe, capable of carrying 3,350 lb. of external stores on six wing hardpoints.

For Mil-Spec-1760 "smart weapons" delivery, AT-6 is being fitted with the A-10C's Central Interface Control Unit (CICU) mission computer, providing net-centric secure data-link communications capability.

The aircraft will feature a night-vision-compatible cockpit, along with the hands-on throttle-and-stick (Hotas) sensor and weapons controls carried over from the second-generation T-6B Texan II trainer. This year, a helmet-mounted cueing system will be added.

The Air Force has said any LAAR candidate must have tandem seats with dual controls so that it can function both as an advanced trainer and LAAR platform. The aircraft also must have zero/zero ejection seats. "Desired requirements" include a 30,000-ft. service ceiling, implying that the aircraft should be pressurized, and the ability to cruise at 180 KTAS or faster at 10,000 ft. AT-6B meets all those requirements.

Initially, the aircraft is being fitted with an L-3 Wescam MX-15Di electro-optical/infrared/laser-designator system. Provisions to accommodate Raytheon 's Multi-Spectral Targeting System also are being developed.

Self-protection features include light armor for the crew and engine compartments, foam lining for the fuel cells, plus AAR-47 IR missile detection and ALE-47 counter-measures systems. More advanced electronic counter-measures may be offered in production aircraft, depending upon customer requirements.

The aircraft will be able to host Paveway II laser-guided 250- and 500-lb. bombs, laser-guided 2.75-in. rockets and GPS-guided munitions, plus Hellfire missiles. Conventional arms include twin 0.50-caliber RN Herstal HMP-400LC guns, Mk. 81 250-lb. and Mk. 82 500-lb. bombs, and LAU-68/131 rocket pods. The AT-6B will be able to operate autonomously from austere runways at forward-operating bases.

The result is a Close Air Support (CAS) and Counter-Insurgency (COIN) aircraft that is priced under $10-million and can be operated for less than $750 per hour, including engine reserves, Hawker Beechcraft officials assert. Support burden is expected to total less than three maintenance staff hours per flight hour, particularly in light of fleet commonality with the 600-plus T-6 Texan II trainers in service around the world.

Such cost considerations are critical to the U.S. military, which rapidly is wearing out such legacy combat aircraft as F-16 , A-10 and F-15 in CAS and COIN operations in Iraq and Afghanistan. As a LAAR aircraft, Hawker Beechcraft officials say AT-6B can perform many of the missions of legacy attack and fighter aircraft, thereby prolonging their service lives.

In mid-June, Aviation Week & Space Technology had an opportunity to strap into the front seat of AT-1, the first AT-6B prototype, to sample its handling qualities, performance characteristics and capabilities of its sensor suite, plus simulate weapons deliveries. Our instructor pilot for the flight was Derek "Turk" Hess, Hawker Beechcraft 's director of AT-6 programs.

The prototype was powered by the Texan II trainer's 1,100-shp. Pratt & Whitney Canada PT6A-68 engine, but it had the additional drag of six under-wing pylons, two external fuel tanks and the EO/IR/laser ball. Production aircraft will have a 1,600-shp. -68D turboprop to help offset the additional weight and drag.

AT-1's computed takeoff weight was 6,875 lb. for our demo flight. Beech Field's elevation is 1,408 ft. and the ouside air temperature was 98F (37C). A clean T-6B would have had a 3,253-ft. takeoff distance under such conditions, assuming a rotation speed of 93 KIAS and flaps at a 23-deg. setting, according to the FAA flight manual. In contrast, we planned a 105 KIAS rotation speed because of the additional drag. Computed takeoff distance was 4,981 ft., according to the company's flight-test engineers.

Start and pre-taxi checks took less than 2 min. Rolling out of the chocks, we found that the aircraft's hydraulically actuated nosewheel steering, controlled by the rudder pedals, provides easy and precise ground handling. Differential braking only is needed to maneuver in tight quarters.

Light right rudder pressure was needed to maintain directional control on takeoff roll. Acceleration was tame, about what one might expect from a turboprop with a one-to-six power-to-weight ratio. The delayed rotation speed produced a crisp liftoff. We climbed out at 500-1,000 fpm. because of the additional drag.

Once level, we accelerated to 200-210 KIAS at full power because of the additional drag. A clean wing T-6B trainer will cruise at 250 KIAS under the same conditions.

Hess then simulated a target assignment from a command and control, intelligence, surveillance and reconnaissance (C2ISR) network. Target position was displayed on the left Tactical Awareness Display as a "sensor point of interest" (SPI). Once an SPI has been designated, it can be used to slew the EO/IR ball to the selected position. This enables both the crew and other C2ISR team members to see images of the target in relation to non-combatants and friendly forces.

Hess then made a quick transition from simulation to real-time targeting of a tower target near a dam spillway. He locked the EO/IR ball onto the tower, designating it as an SPI. We could see EO video of the tower in color, and as IR images. The imagery also could have been relayed to other air and ground forces, had we been connected to a C2ISR network.

After the demonstration, we climbed to 10,000 ft. and began a series of stability and control, and aerobatic maneuvers to evaluate the handling and performance characteristics of the aircraft.

Roll rates with external stores, even with empty external tanks, are modest if only the aileron is used. Higher rates may be achieved by augmenting the roll with plenty of rudder, but then plenty of rudder work is needed to return to balanced flight. A yaw damper will fix that in production aircraft.

We also stalled the aircraft in both clean and approach-flap configurations. High-angle-of-attack maneuvers are one of the aircraft's strong suits. In both maneuvers, we held back the stick throughout the stall break, with no loss of roll control or wing-drop tendency.

Upon completion of the air work, we headed to Beaumont, Kan., for a simulated laser-guided rocket attack on enemy combatants holding up at a building in the vicinity. Hess designated the site as an SPI and locked on the EO/IR ball. We circled the SPI at a 5-mi. radius, thereby reducing risks of small-arms and shoulder-launched anti-aircraft missile fire, had we been operating in a combat environment. It also was apparent that small bank angles cause the bottom of the wing to block the view of the EO/IR ball at such ranges.

We flew south of Beaumont about 10 mi. to begin our attack run. Using head-up display guidance, we began a shallow dive and simulated weapons release. We pulled off the run and banked sharply away from the target. The laser designator on the EO/IR ball remained locked on the simulated target as we maneuvered out of the area, an action that would have enabled the precision-guided munitions to reach the target.

AT-6B proved to have landing pattern speeds and characteristics similar to those of an entry level, light business jet. We adjusted technique for the typical tight racetrack pattern and steep glide path needed to minimize exposure to small arms fire when landing at a forward operating base in a combat environment. Using 45-deg. turns and 10-15-deg. nose-down pitch attitudes, we could hold approach speeds of 125-130 KIAS, descending from 1,500 ft. AGL (above ground level) abeam to short final with little or no power.

The aircraft is easy to land and it has virtually no tendency to float, if the crew maintains desired angle of attack to touchdown. This results in landing speeds of 100-106 KIAS at typical operating weights. Notably, the landing gear is stressed to absorb descent rates up to 780 fpm., so only a slight flare is needed to check a steep approach to touch down.

We returned to Beech Field and landed with 600 lb. of fuel after the 1-hr. 40-min. flight. Conclusions? AT-6B is quite capable, but it needs the 500-shp. increase and full integration of its avionics suite with the CICU.

However, archrival Embraer's Super Tucano got a jump-start on AT-6B when it participated in Phase I of the U.S. Navy's Imminent Fury (IF) program in 2008-09. IF was a platform "agnostic" attempt to evaluate several "find, fix and finish, exploit and analyze" aircraft, that when fitted with a full ISR package could operate with U.S. special forces in Afghanistan. Similar to the current LAAR requirements, the aircraft would have to have to be survivable against small arms and shoulder-launched anti-aircraft missiles.

Sources close to the Imminent Fury program told AW&ST that the team initially looked at a number of candidate aircraft, including Hawker Beechcraft 's proposed AT-6, but it would have been at least 18 months before a prototype would be operational. The Vietnam-era OV-10 Bronco was briefly considered, but none could be found in time to participate in the program.

The IF team wanted to evaluate other candidates, but Embraer 's Super Tucano was the only contender then available.

During IF, Super Tucano met all objectives, according to the same sources. The twin 0.50-caliber FN Herstal machine guns, mounted internally in the wings, along with 2.75-in. rocket pods and laser-guided and unguided Mk. 81/Mk. 82s were qualified onboard the aircraft.

After Phase I, the IF program wound down due to lack of additional funding. That pause gave the AT-6B time to catch up. The USAF issued a Capability Request for Information in July 2009 for LAAR aircraft, with initial deliveries in FY 12 and an initial operating capability in FY 13. Up to 100 LAAR aircraft could be procured, depending upon Defense Department budgets.

AT-6B and Super Tucano currently are the only aircraft in the $10-million range that meet all LAAR requirements. Embraer claims its aircraft is superior because it was designed from scratch as a CAS platform, not as a derivative of a trainer. Compared to AT-6B, Super Tucano has a larger aft fuselage to accommodate additional avionics, 19% more wing area and a 13% higher maximum takeoff weight with external stores.

Hawker Beechcraft officials counter that AT-6B's being a derivative of the T-6 Texan II trainer is one of its strengths. The trainer has been in service for a decade and the fleet has logged more than 1.2-million flight hours. The officials assert that the company has a well-established, worldwide logistics network supporting the T-6 and its other special missions aircraft, thus AT-6B will have similar support.

This year, AT-6B was given a chance to show off its capabilities during the biennial Joint Expeditionary Forces Experiment (JEFX '10), the ninth such event conducted by the Air Force.

Similar to Phase I of IF, the theme of JEFX '10 was irregular warfare. C2ISR aircraft, fighters and tankers, plus CAS airplanes and helicopters, participated along with AT-6Bs and a prototype T-6C.

The overall objectives for JEFX '10 were to engage multiple, mobile targets in an urban setting, decrease the time required to locate, positively identify and destroy hostile forces while minimizing collateral damage and share multiple sources of data, including near real-time video, between friendly air and ground forces.

JEFX '10 was "pay to play." The AT-6B was sponsored by the Air National Guard and Air Reserve Command Test Center. Super Tucano did not have a military or defense contractor sponsor, so it was excluded. Thus, AT-6 was the only LAAR contender to participate in the exercise.

Detailed results of JEFX '10 remain classified, but company officials claim that the AT-6B and T-6C prototypes completed 100% of assigned missions. AT-6B demonstrated the capabilities of its full-color electro-optical camera, infrared sensor and laser target range finder/illuminator/designator. It also tied into the Link 16/enhanced position location and reporting system/situational awareness data-link network and flew simulated attack missions on both fixed and moving targets.

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