Wednesday, December 7, 2011

Stealth fighter marks important anniversary

Alamogordo Daily News
By Arlan Ponder, For the Daily News
Posted: 12/06/2011 10:31:20 PM MST

Click photo to enlarge

"Have Blue," is the predecessor of the Air Force's famed F-117A Nighthawk ... (U.S. Air Force photo)
To many people, Dec. 1 marked a realization that there were only 24 more shopping days to Christmas. But to people who are involved with stealth fighters, an event happened on this date that forever changed the world of aviation.

It was the first flight of "Have Blue."

Have Blue was the predecessor of the Air Force's famed F-117A Nighthawk -- the first "stealth fighter" in the Air Force's inventory.

On Dec. 1, 1977, just after sunrise at Groom Lake, Nev., HB1001 made its maiden flight, and history, as Lockheed test pilot Bill Park took it through its flight.

Ben Rich, the former head of Lockheed's Skunk Works that built many of the nation's most advanced aircraft said, "This flight will be every bit as important to the nation's future and the future of the Skunk Works as the first test flight of the U-2 spy plane."

This came after the prototype was flown disassembled, via a C-5 Galaxy, from the Lockheed Plant in Burbank, Calif., to the classified Nevada base. The crew who made that historic flight in the middle of the night Nov. 16, 1977, never knew they had the first Experimental Survivable Testbed prototype in their cargo hold until years later after the F-117A came out of "the black."

The Have Blue prototypes, or XST, were the first fixed-wing aircraft designed from an electrical engineering (rather than an aerodynamic) perspective and, while similar to the later F-117, were smaller with greater wing sweep and inward-canted vertical tails.

Weighing only

8,950 pounds empty, the Have Blue aircraft topped out at a max takeoff weight of only 12,500 pounds. Lockheed engineers exploited as much off-the-shelf technology as practical to reduce design risks and keep costs and design turnaround times to a minimum.
The production aircraft used an environmental control system adapted from the C-130 Hercules; flight controls from the F-16 Fighting Falcon; brakes from the F-15 Strike Eagle; an ACES-2 ejection seat common to the F-15, F-16 and A-10 Warthog; and comm/nav equipment used in other Tactical Air Command aircraft. The ground support equipment used for the aircraft was common to 95 percent of other aircraft, thus facilitating deployments and cutting life cycle/logistical costs.

Have Blue had only three objectives:

• In-flight validation of the four low-observable signatures the program had previously identified.

• Demonstrate acceptable flying qualities and performance.

• Demonstrate modeling capabilities that accurately predict low-observable characteristics of an aircraft in flight.

Additional variations of Have Blue included the absence of flaps, a speed-brake and weapons bays on the XSTs. With regard to the inward-canted vertical tail section, initial beliefs that the inward-canted tails would help shield the hot exhaust from infrared detection proved exactly the opposite; it funneled the hot exhaust straight down beneath the aircraft, increasing its infrared signature.

The F-117A also employed a targeting Forward Looking Infrared, or FLIR, system mounted in a recess below the windshield. Target acquisition and weapon delivery is carried out with a ventral FLIR/laser turret, to the right of the nose wheel bay. Due to the absence of radar for ranging to bomb release, the laser provided both range finding and designation for weapons, its ventral position providing a similar field of view to established FLIR/laser targeting systems such as Pave Tack. 5

The navigation/attack system was fully digital and built around IBM mission computers and MIL-STD-1553B busses, integrated with Honeywell inertial navigation equipment. The cockpit employed a Kaiser HUD derived from the F-18 Hornet's AVQ-28, Honeywell color multi-function displays coupled to a Harris digital tactical (moving map) display system.

The Air Force has revealed the existence of a ground based automated mission planning system that used a ground based computer, graphics consoles and the aircraft's Delco 1553 bussed cartridge tape system for uploading mission particulars into the navigation/attack system. In addition, the flight instrumentation included a Honeywell radar altimeter and air data computer.

Sadly, on May 4, 1978, HB1001 met its demise on its 37th test flight, when landing gear trouble resulted in a decision for Park to eject. Park was injured in the incident and never flew again. As a result of his injuries and the subsequent removal from flight status, Lockheed named him their director of flight operations.

A short 13 months later HB1002 met the same fate as Air Force test pilot Ken Dyson ejected from it after experiencing engine and hydraulic failure. By this point, the program was within a few sorties of its planned completion and had achieved all of the Have Blue program's objectives.

Considered an overwhelming success, the Air Force closed the doors on Have Blue. Both of the prototypes are buried at Groom Lake.

As a result of the testing on Have Blue, numerous changes were made from the prototypes to the final F-117 design. The most noticeable difference was the arrangement of the vertical tail. On Have Blue, the tails are inward-canted, while on the Nighthawk the tails are outward-canted.

In the end, it was determined the inward-canted tails acted as reflectors and bounced the exhaust heat toward the ground and made the aircraft more visable from below. Designers ultimately moved the tails back on the F-117 so they weren't directly over the exhaust. This move also increased the tail moment arm by 50 percent, though later versions of the plane required larger tails for better control.

For the trivia minded, the windowless Skunk Works hangar where the Have Blue prototypes were engineered, fabricated and assembled is the same building that produced the F-104 Starfighter, U-2 Dragon Lady and SR-71 Blackbird aircraft. In addition, in March 1976 the radar range at White Sands Missile Range, which used the most sensitive and powerful in the free world, was used to test a wooden, flat paneled, 38-foot, black painted model nicknamed the "Hopeless Diamond."

Alan Brown, former director of engineering at Lockheed, said there couldn't be an F-22 Raptor without the F-117; however, without a test flight on Dec. 1, 1977, in a dry lake bed in Nevada, neither aircraft might have made it to the Air Force inventory.

Arlan Ponder is the media relations chief for the 49th Wing Public Affairs Office at Holloman Air Force Base.

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