Zoom climbs in the rocket-boosted NF-104 could top out at 120,000 feet in zero gravity. (Courtesy George J. Marrett)

Sky High in a Starfighter

My climb to the top in the F-104.

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(Continued from page 4)

Our second child was expected to be born about two months into my year of test pilot training. We already had a four-year-old son, and Jan did not want her children to grow up without a father. Asked about the risk, I explained that I had had the best training in the world, the test aircraft were maintained to a higher level, and that we flew during the daytime and in clear weather. I wasn't sure how much of that was accurate, but she seemed to accept my explanation.
All but three of the pilots in our class were married, and most had children, so Jan and I weren’t the only couple having such discussions. The school may have known this: They planned an open house—an opportunity for the families to visit the school.

On the appointed day, we gathered in the auditorium for Colonel Charles Yeager to make his entrance. When he arrived, he had on rows of ribbons for combat in World War II and for flight test accomplishments. But he also wore a large white bandage around his neck, and his left arm was in a sling. If the premier test pilot in the Air Force was this banged up, it seemed clear to Jan that flight test could be a very dangerous business.

The tour of the hangar held another surprise. Yeager was bandaged up because he’d recently punched out of an NF-104, the wreckage of which was spread out on the hangar floor for an investigation. No piece of his crashed aircraft was larger than a refrigerator, and everything was covered in gray ash. The sight of wreckage was familiar to me, but most civilians, and certainly Jan, had never viewed such a shocking sight.

Jan’s concerns would prove to be well founded. Over the next 25 years, 32 test pilots—friends of mine—would be killed in aircraft.


Now Departing: T-Tails and Other Killers

The T-tail on the McDonnell F-101 Voodoo and the Lockheed F-104 Starfighter could create major problems. At high angles of attack, the outer wing sections stalled before the inner wing sections did, and that tended to move the center of lift forward. At the same time, the downwash from the wing began to impinge upon the horizontal tail, changing the angle of airflow over it and reducing its effectiveness. The combined effect caused the aircraft to pitch up.

Most aircraft pitch down when they stall. The nose drops, the aircraft picks up speed, and it returns to controlled flight. In a pitch-up, the angle of attack increases even with the control stick full forward. The aircraft goes out of control and may end up in a spin from which, in both the F-101 and the F-104, it was sometimes impossible to recover. If a pilot could recover by deploying a small drag chute attached to the tail, the ensuing dive recovery could take up to 10,000 feet. A pitch-up below 10,000 feet resulted in an automatic ejection. Pilots were directed never to intentionally pitch up or spin either the F-101 or the F-104; the pilot’s flight manual called those prohibited maneuvers.

Lurking in the background was another serious phenomenon. Beginning with the North American F-100 Super Sabre, “Century Series” fighters (those with numerical designations from -100 up) like the F-101 and F-104 were designed with a high concentration of mass along the fuselage. This led to a dynamic characteristic known as inertial coupling, a phenomenon that can best be explained by considering a rapid rolling maneuver. Picture the aircraft at a positive angle of attack. It begins a rapid roll around its longitudinal axis, which is displaced from the direction the aircraft is moving in by the angle of attack. As the high mass along the fuselage begins rotating at an angle to the flight path, it tends to diverge from that path, increasing its displacement in pitch and yaw the longer the roll continues. So in addition to needing a big vertical tail for directional stability, an even larger tail was needed to prevent inertial divergence.

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