After a few months, 780's desert camouflage was removed, and it was repainted light gray. The plane had no national markings (in common with most of the other Groom Lake aircraft), but 'Hal,' 'Skip,' and 'Dave' were painted on the canopy rail.[413]
Between mid-1981 and early 1982, the other four FSD Senior Trend aircraft were delivered to Groom Lake. While the first two (780 and 781) were aerodynamic test aircraft, the other three (782, 783, and 784) were systems aircraft. As such, they had the full set of cockpit displays, just as on the operational aircraft. It has been reported that 782 and 783 had the Skunk Works emblem on their tails. The fifth FSD aircraft (784) reportedly sported a full- color painting of Elliott, the dragon from the Disney film
Initially, the FSD aircraft were painted gray. The commanding general of the Tactical Air Command then ordered they be painted black. (Although most of the test flights were done in daylight, the aircraft's operational missions were flown at night.) Markings became more formal: national insignia, 'USAF,' and the aircraft number on the tail.[415]
FLYING ON THE EDGE
With the full complement of FSD aircraft on hand, along with additional test pilots, the test program got under way in earnest. The flight-test program explored a number of unknowns related to the Senior Trend's stealth design.
Many test hours were required to calibrate the air-data system for angle of attack, sideslip, airspeed, and altitude. A critical part of the flight control system was the angle of attack limiter. Angle of attack (AOA) refers to the angle between a plane's wing and the direction of the airflow. Wind-tunnel tests and free flights of unpowered models indicated the Senior Trend would pitch up at high angles of attack. (The nose would abruptly and uncontrollably rear up.) The aircraft would then enter a 'deep stall' and would not be recoverable. The AOA limiter would have to automatically move the control surfaces to prevent the aircraft from exceeding the critical value.
Because of the risk, the AOA testing was done in slow steps. There were literally hundreds of individual tests run.
Validation of this approach came on May 23, 1983. One of the FSD aircraft was on final, with its left wing low, when a strong wind gust hit it.
This caused the AOA and sideslip to instantaneously reach levels higher than any tested — higher, in fact, than could be tested in the wind tunnel.
The AOA limiter countered with full down eleven in less than 0.4 seconds and moved the fins 90 percent of their full travel. The plane successfully recovered.[416]
Flutter testing was also prolonged. The early tests showed no problems, but during a weapons compatibility test, an air force test pilot put the aircraft into a sideslip while flying at near maximum speed. The left fin underwent 'explosive flutter' and disintegrated. The pilot made it back to a successful landing despite very poor stability. Farley called it, 'a very professional response by a real pro.'
The problem was traced to the redesign of the fins — the added area had reduced the fin's stiffness. The problem had been hidden during the earlier tests by the friction of the fin bearing.[417]
One of the more unusual problems was testing the Senior Trend's inlet grids. There was some concern they could distort the air flow to the engines. In fact, they acted like 'flow straighteners,' giving the engines a constant flow of air.
More serious was grid icing. Tunnel tests indicated that, in Farley's words, 'the inlet grids not only looked like a giant ice cube tray, but acted like one as well.' A wiper system and alcohol dispenser was developed.
Ironically, airframe icing was not judged to be a problem; chief aerodynamicist Dick Cantrell said that any ice buildup would only help the plane's aerodynamics.[418]
If the Senior Trend was to be an effective bombing platform, the avionics systems would have to show capabilities never before achieved. The pilot would have to find the target, which was not an area or a wide-spread factory but rather a specific part of one specific building, then direct the LGB to the aim point — all in the dark.
The heart of the Senior Trend's bombing system was a pair of infrared turrets — the forward-looking infrared (FLIR), located in the front of the plane, and the downward-looking infrared (DLIR) on the plane's underside.
Each turret was mounted in a well that was covered by a fine-mesh, radar-absorbing screen. The two-turret design was able to scan from just above the horizon to below and behind the aircraft. The image from the system was displayed on the instrument panel's central cathode-ray tube.
The design posed many problems. To give one example, the FLIR turret would have to pick up the target at long range, then track it as the plane approached. The FLIR would then have to 'hand off' the target to the DLIR without losing the target lock. To create this seamless display, the two turrets had to be exactly aligned (called boresighting).
Flight testing of the system revealed numerous problems. It proved impossible to electronically boresight the two turrets, which created problems in the handoff. Problems with the video display included 'windshield wiper noise,' 'jello,' 'shimmering,' 'picket fence noise,' and 'horizon shadow-ing.' Added difficulties included problems with level and gain controls, turret slew rates, and target acquisition and illumination.
Some of the problems were purely subjective, which made it even more difficult. There were three test aircraft (FSD 3, 4, and 5) and six test pilots; what one pilot judged unacceptable on one plane was called good by another pilot. A 'Tiger Team' was organized to sort out the systems problems.
It was headed by the Skunk Works chief scientist and drew man power from other Lockheed divisions.
Like the engineers who had worked on earlier Black airplanes, the team came up with innovative, simple solutions to the complex problems. They abandoned efforts to electronically boresight the turrets and used a mechanical procedure. The aircraft was rolled up a thirty-inch-high ramp.
This raised the nose and allowed both turrets to view the same target board simultaneously. They could then be aligned. To prevent the control surfaces from scraping the ground, mattresses were placed under them when the hydraulic system was shut down. A portable boresight fixture was developed, the turret mounts were fixed in place with epoxy, and tolerances were tightened. Reliable handoffs could then be accomplished even in 'dive-toss' drops: this involved the plane going from level flight into a dive, then pulling up and releasing the bomb. Three FLIR-DLIR handoffs were required for this maneuver. Another difficult flight maneuver was loft bombing, where the plane goes from level flight into a steep 4-g pull up. The bomb is released during the pull up and is 'thrown' toward the target. The video display problems were traced to electromagnetic interference due to poor shielding. The target lock-on problems were corrected with new software.
For flight testing of the modifications, the team developed what was described as 'a broadband, wide- spectrum, inexpensive, expendable, point-source IR target.' This was a barrel filled with glowing coals — a backyard barbecue.
In all, it took a year and some 100 test flights to correct all the problems.
When the work was completed, one aircraft dropped a 2,000-pound, inert GBU-27 laser-guided bomb, which scored a direct hit on the barrel.[419]
Major Alton C. 'Al' Whitley had flown two tours in Vietnam, one in F-lOOs and the other as a search and rescue A-7 pilot, but this was a new and novel experience. He had been called to a small interview room at Nellis Air Force Base. When he knocked on the door, a man opened it an inch and asked if he was Whitley. He said yes, and the man asked for his ID card. The man took it and closed the door. A minute later, he reopened it and said, 'Yeah, you're Whitley.'
Once Whitley was in the room, he was offered a chance to fly with a top-secret unit. The duty would require constant separation from his family, and he could not be told much more. He had five minutes to decide, and when he left the room, the decision stood. Whitley did not know what airplane he would be flying, or what the unit would be doing. He responded, 'Sign me up. I'll do it.'
Whitley thus became a member of a secret brotherhood composed initially of about ten officers and a dozen enlisted men — the 4450th Tactical Group.
The unit commander was Col. Robert A. Jackson. He was to select and train the initial group of pilots. He was looking for pilots who were both experienced and mature — majors and senior captains with a thousand hours
