Two more days of the same routine followed, with direct hits rising to six on day two and seven on day three. Day four was a day of rest for the pilots and maintenance for the F-15Is. The mechanics made a decision to swap out one of the two engines in F-15 airframe number 261 for one of the spares that had been brought from Israel. The plane’s Digital Electronic Engine Control software indicated that the third stage variable stators on the high pressure compressor turbine were failing to adjust to the commanded angle of attack. The engine still operated, but the mechanics were nervous and there was no reason to risk an engine — and perhaps an airframe — on any scenario that was not fully controlled.
Day five started with a review of the video from day three. At the end of the review the squadron commander stood. “The bullshit ends today. Everyone here should know how to put that weapon on target. We have more advanced work to do and a limited number of bombs to work with. Get your heads out of your asses and get the job done today.”
The pilots had indeed learned and the day off allowed everyone to shake off the lingering effects of jetlag. The results showed. Sixteen of twenty-five bombs dropped were direct hits. Of the remaining nine, four were near misses, just outside the plywood doors.
On day six, each crew flew one sortie with one pass over the target. This time, however, the sorties were flown at night, the crews using night vision and forward looking infrared to see the terrain and their targets, which had been moved to a new hill during the day. The results were encouraging, with eighteen direct hits and four near misses. As during the day, video had been taken, this time with a night vision lens attached to the same camera. The video was reviewed the next morning.
The training intensity was accelerated during days seven through nine. The poorest performing aircrew — the only one without a direct hit — was excused from further participation, leaving twenty-four aircrews. The remaining aircrews started simultaneous attacks, first with two aircraft during the day, then with three, this time using laser designators on the targets.
On day nine, the crews began using the Tunnel Defeat system, with three aircraft at a time targeting three plywood doors in a single hillside. During the day, each set of three planes made three practice runs without dropping any bombs. The exercise was intended to get the aircrews used to the close flight coordination necessary to successfully use Tunnel Defeat. If the planes were not properly coordinated, the onboard computers would not allow them to release their weapons. By the final pass, all of the groups successfully coordinated their timing. Following a late afternoon review, the crews prepared for nighttime sorties.
The results were good. All eight groups were able to drop their bombs, with 22 of 24 bombs hitting their targets.
Day ten started with a review of the prior night’s mission What had each crew done right and wrong? All of the 48 airmen in the room were asked for their opinions. Finally, the men were briefed on the next assignment, a repeat of the prior night’s mission. To raise the pressure, the squadron commander made an announcement at the end of the briefing: Any group that failed to drop its bombs on the first pass would be dismissed from further training. The men were given the afternoon off.
That night all eight groups flew and all eight groups succeeded in ordering the release of their bombs. However, one bomb failed to release, the error being quickly traced to a short in the centerline pylon circuitry that was repaired within a half hour of the plane’s return. Of the 23 bombs actually released, 22 hit the plywood doors as intended. None of the aircrews were dismissed.
Day eleven was a day off for the crews, with movies and beer being delivered to the briefing room. The day passed quickly.
Day twelve was a daytime attack in coordinated groups of four. The smaller practice bombs were now used up and each plane was armed with a full sized practice bomb. The RAAF, at the request of the commanding Israeli officer, had built four plywood doors along a distance of 850 feet on the east face of Delamere’s longest hill structure. To increase the difficulty of attack, one of the tunnel entrances was placed on a north-facing segment of the ridge. The men were briefed on their assignments during the morning. Sorties would begin at noon.
The first of six groups of four aircraft took off in quick succession just minutes after the noon hour. Gadget flew in the second group and assumed the role of the northern plane. His plane had to break away from the other three, wheel to the north and turn back to the south to make the run at its designated target. The timing of this plane was critical, so the best pilot was picked for this maneuver.
In the rear seat, Pacer counted the time to begin their turn to the north. “Initial point at three, two, one, bank,” said Pacer into the intercom system. Gadget initiated his turn at precisely the right point. He pushed his two throttles forward through full military power to apply his afterburners for the calculated amount of time, quickly accelerating the F-15I to 521 knots. After twenty-two seconds of flight, he had created 1.7 miles of lateral distance between his plane and the nearest in his group.
“Turn in,” said Pacer. Gadget began to bank slowly back to his left. In the rear seat, Pacer tracked the plane’s position on a navigation map versus the known GPS coordinates of their target. He called out corrections to his pilot in a code the two men had worked out over several years of partnership. “One right,” said Pacer, indicating to Gadget that the correct vector was one degree further right, meaning that the plane was banking too hard to the left.
The plane continued on its arc, its speed being critical to arriving at the right release point at precisely the right time. The onboard targeting and release computer was communicating with the three other aircraft, continuously calculating all four relative positions as well as the position of all four aircraft relative to each plane’s designated target. The computer gave important feedback to Pacer.
“Minus ten,” said the weapons officer, indicating to Gadget that they needed to decrease their airspeed by ten knots. Gadget eased his power just slightly, an amount that would be imperceptible to an outside observer.
“Speed good. One left.” Gadget increased his angle of bank just slightly. The plane was now on the right vector and flying at the right speed. The plane continued its arc, coming around to a heading of 185 degrees. Inside his DASH helmet-mounted display, the onboard flight computer, synched into the targeting and release computer by the Boeing engineers, projected a red triangle over the precise spot that was being targeted. Gadget leveled the wings. “Zero final,” came the comment from Pacer, indicating they were properly on their planned attack bearing. “Zero speed.” The plane’s speed was exactly correct.
“Fuze hot,” said Pacer, indicating that the bomb’s fuze had been armed by the targeting computer. “Weapon lock,” came the final comment from Pacer. They were properly synched with the other aircraft and on the precise approach for attack. On a video screen on the right of the cluster of instruments in front of Pacer, the target tunnel entrance was clearly visible and in the middle of the crosshairs on his screen. Pacer squeezed the trigger on his targeting joystick to lock his laser designator on the target and send a beam of light from the LANTIRN pod onto the center of the plywood doors.
In Gadget’s ear, a tone sounded. It was an electronic beep of the type and tone heard on the BBC when counting down to the hour. Gadget knew it was the first of four tones and that the computer would release his bomb at precisely the instant the fourth tone sounded. He also knew the cadence of the tones, having heard them now many times over the prior two weeks. As the third tone sounded in his ear, just like he had done on every previous bomb run, he pulled his short joystick back just slightly, the pressure and distance being determined not by a computer but simply by his experience and gut feel. The nose of the F-15I rose a few degrees and the inert BLU-121 released from the centerline pylon precisely at the instant the fourth tone sounded in Gadget’s ear. He immediately swiveled the joystick to his right to begin a five G turn. He added power to compensate for the forward momentum being robbed by the turning action of the plane. At the low altitude they were flying at, there was no margin of error.