Space Shuttle Enterprise sits atop the fuselage of a specially modified Boeing 747 during the three taxi tests conducted in the early morning. "These taxi runs would evaluate the technique of setting thrust for takeoff. They would also assess directional stability and control, elevator effectiveness during rotation prior to takeoff, airplane response in pitch, thrust reverser effectiveness, use of the 747’s brakes, and airframe buffet."
"Three taxi tests took place with Dryden research pilot Fitzhugh 'Fitz' Fulton at the controls, all in the single day of February 15, 1977. The first taxi test reached 76 knots, well below takeoff speed. Fulton then reversed thrust and slowed to 23 knots before applying the wheel brakes. Inspection showed no damage or overheating within the wheel assemblies, and Fulton received permission to turn his plane around and taxi in the opposite direction, at higher speed. This time he reached 122 knots. Fulton evaluated the elevator effectiveness during this run, raising the nose wheel momentarily between 95 and 100 knots. Again he reversed thrust and slowed, applying the brakes at 20 knots as his plane rumbled to a stop.
The third taxi test simulated an aborted takeoff, making good use of the 15,000 feet of runway length. Fulton accelerated to 137 knots, then cut the engines from takeoff power to idle. Pulling back on the controls, he applied elevator and raised the nose to a 5-degree pitch-up. The 747 rotated smoothly; Fulton held the nose wheel off the runway for some 1,500 feet before lowering it again. He then pushed the throttles forward and reversed thrust. This time he carried out a more demanding test of brakes, braking between 49 and 40 knots. He indeed had come close to taking off; the plane would have lifted from the runway at around 145 knots and a pitch angle of 6.5 to 7 degrees.
"Fulton declared that his 747 responded so well that at times the flight crew could not tell that the orbiter was atop the fuselage, with a weight of 143,600 pounds. 'As is oftentimes the case,” he added, the actual carrier aircraft-orbiter combination handled better than what we experienced in the simulator.'"
Date: February 15, 1977
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