During the Vietnam War, the United States had developed laser guided bombs (LGB), better known as "smart bombs." The stealth fighter would be equipped with a laser. The pilot would put the laser beam on the aim point, and the bombs would home in on the laser light reflected from the target.
The guidance system would compensate for shifting winds: all the pilot had to do was hold the beam on the target. It was now possible to hit a target within inches of the aim point.
Stealth meant a single aircraft could penetrate the heaviest air defenses. LGBs meant this single plane could then destroy any target, no matter how small or hardened against attack. No longer was it necessary for massive formations to […] one bomb, one target. This was the attack profile the stealth fighter was to undertake. It would change airpower.
The aircraft which emerged from the redesign had a shape similar to that of the Have Blue, but the fuselage was wider and more squat. The Senior Trend was 65.9 feet long, with a wingspan of 43.25 feet. The high canopy trailed off to a very thin rear fuselage. Seen from the front, it resembled a pyramid; from the rear, the plane looked almost flat. By late 1979, a wooden mock-up was completed. This was used to check placement of equipment and systems. A full-scale Senior Trend pole model was also built for RCS testing. This posed a security problem — such testing was done outdoors where the model might be photographed by Soviet reconnaissance satellites.
To prevent any sightings, the testing was done at night.[405]
In December 1979, a contract was awarded to Lockheed to build five full-scale development (FSD) test aircraft and fifteen production aircraft.
This would provide a full squadron of the aircraft.[406] The first Senior Trend was given the aircraft number 780, for its scheduled first flight date of July 1980.
Because of the short time, existing systems were used. The General Electric F404-GE-F1D2 turbofan engines were from the navy F/A-18, without the afterburners of the fighter. The F/A-18 also provided the multifunction cathode-ray tubes, HUD, fuel controls, stick grip, and throttles. The sensor displays were from systems developed for the OV-10D and P-3C. The navigation system was from the B-52. Other systems came from just about every Lockheed aircraft built since the T-33; these included the SR-71, C-130, L-1011, and even the F-104.[407]
Of critical importance was the flight-control system. Like the Have Blue, the Senior Trend was aerodynamically unstable. Harold C. "Hal" Farley Jr., the Lockheed test pilot selected to make the first flight, later described the plane's "aerodynamic sins": "In fact, the unaugmented airframe exhibits just about every mode of unstable behavior for an aircraft; longitudinal and directional instability, pitch up, pitch down, dihedral reversal, and various other cross axis couplings. The only thing it doesn't do is tip back on its tail when parked."
It was obvious that a computer-controlled, fly-by-wire system was needed.
There was no manual backup system because it was impossible for a pilot to control the plane without the computer. To reduce risks, it was decided to use a proven off-the-shelf system. The F-16's fly-by-wire system was selected; actuators, flight-control computer chassis, and power supply were modified slightly. New computer programs had to be developed.
The control system was designed so the Senior Trend would handle like "an ordinary plain vanilla aircraft." Programming was tested on an NT-33, "by real pilots flying in a real airplane in real turbulence." Some flight tests assumed the directional stability of the Senior Trend was even worse than predicted.[408] It would prove to be a wise precaution.
Despite the Skunk Work's best efforts, by the summer of 1980 the project was behind schedule, and the first flight was nowhere in sight. Each day seemed to bring new problems and no solutions. Ben Rich said years later that this was the low point of his life. The meetings went from before dawn and continued long after dark. In the midst of this, Ben Rich's wife, Faye, died of a heart attack, leaving him emotionally devastated. When he returned to work, Alan Brown, the Senior Trend program director gave him a note. Written on it was Rich's next birthday "June 18, 1981." When Rich asked him about it, Brown said, "That's the date we test-fly the airplane."
He continued, "The date is firm. In granite. Count on it."[409]
SENIOR TREND TAKES FLIGHT
By the fall of 1980, aircraft 780 was beginning final assembly at Burbank. By early June 1981, final checkout was completed. The wings were removed and crated. The fuselage was covered in a shroud, and a wooden framework was added to the nose to further hide its shape. Under cover of darkness, number 780 was loaded aboard a C-5 and flown to Groom Lake.
Upon arrival, 780 was taken to a hangar at the south end of the flight line and reassembly began. Even here, security remained paramount: a camouflage net was stretched across the open hangar door. Once assembly was complete, static engine test runs were made. The plane was kept inside the hangar, with the exhaust vented out the open door.[410]
When delivered, 780 was a dark gray color. Before the first flight, patterns of light blue and light brown were painted on the aircraft. As with Have Blue 1001, this three-color finish was meant to hide the faceting. (780 was the only one of the FSD aircraft to be camouflaged.) The paint finish was ragged looking and appeared to have been hurriedly done.[411]
On June 18, 1981, just as Brown had predicted during the dark days of nearly a year before, everything was ready. As dawn broke, 780 was rolled out of its hangar for the first time. Hal Farley ran up the engines, and 780 started down the runway. As with the first hops of both the U-2 and A-12, it was to be an eventful flight.
It was a difficult task to design an air-data system that was stealthy. Four probes extended from the nose, along with a conventional boom. Because the air-data probes had shown erratic readings during ground vibration testing, it was decided to ballast the aircraft to a far forward center of gravity point, turn off the angle of attack, and sideslip measurements to the flight-control system.
Immediately after 780 lifted off the runway, it became apparent to Farley that the directional stability was much worse than predicted. Farley immediately switched on the sideslip feedback to the flight-control computer. The plane's handling "stiffened up," and the rest of the flight was routine. Subsequent analyses indicated the Senior Trend's directional stability and directional-control power were less than predicted. The solution was to increase the area of the fins by 50 percent. The new fins were installed by the fall of 1981. This cured the instability but would cause other problems later in the test program.[412]
Two more test pilots soon joined the program — Skip Anderson (air force) and Dave Ferguson (Lockheed). 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 Pete's Dragon. This was in honor of Col. Pete Winter, air force commander at Groom Lake. (For the uninitiated, Elliott was invisible to everyone except Pete.)[414]
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 th
e 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]
THE 4450TH TACTICAL GROUP
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 of flight time and air-to-air and/or air-to-ground backgrounds (F-4s, F-15s, F-llls, A-7s, and A-lOs). Colonel Jackson met with each candidate. Once they agreed, the pilots were told to go back to their units and wait for a call.
Although the 4450th Tactical Group was formally established on October 15, 1979, training did not begin until June 1981. Whitley and the other pilots spent time at Lockheed in the cockpit procedures trainer. This was a model of the cockpit on which the pilot could learn the layout of the various consoles, but not how the plane would fly. On seeing the FSD aircraft under construction, the pilots' initial reactions were to wonder if that strange-looking airplane could really fly.
Ironically, the unit that was to fly the world's first stealth aircraft had no airplanes. All the FSD aircraft were used for testing. Soon after the unit began training, they received A-7s. These were organized into the P-Unit (later called the 4451st Test Squadron). The
A-7s were to provide both pilot-proficiency training and cover. The 4450th Tactical Group's cover story was that it was an A-7 avionics and evaluation unit.[420]
At the same time, the base the unit was to use was under construction — the Tonopah Test Range (TTR). It had originally been built to support drop tests of nuclear weapons. The TTR was on the north side of the Nellis range, 140 miles from Las Vegas and northwest of Groom Lake. The nearest town was Tonopah, Nevada. The area was open range, with wild horses running free.
The base was immediately staffed with air force security police. The flight line was walled off with a double fence; the only access to the runway was through gates. The area between the fences was lighted at night and had intruder detectors. At first, the facilities were limited to a few buildings, a small mess hall, and sixteen winterized trailers. These were soon replaced by dormitories and hotel-style rooms for the pilots and support personnel.
Because all the flights were done at night, the rooms featured blackout cur-tains to keep out the sun during the daylight sleeping hours. The runway, taxiways, and aprons were all improved, while maintenance facilities, fuel and water tanks, fire stations, and a dining hall were built. Individual hangars were also constructed for each aircraft. In addition to providing protection from the weather, these hangars also hid the planes from prying eyes during the day.[421]
Before the 4450th Tactical Group could become a fully functional unit, it would need the production Senior Trend aircraft. It was the spring of 1982 before the first aircraft, 785, was ready. Its first flight would end in a near fatal crash.
The accident occurred on April 20, 1982. With Lockheed test pilot Robert L. "Bob" Riedenauer at the controls, 785 began its takeoff roll. The plane lifted off correctly, but moments after the main wheels left the runway, it yawed violently and went out of control. Within seconds, the plane went inverted going backward and slammed into the ground on the shore of the lake bed. It took rescue crews some twenty minutes to pull Riedenauer from the wreckage. He had suffered major injuries. He recovered, but never flew again.[422]
Dark Eagles: A History of the Top Secret U.S. Aircraft Page 23