X-15 Extending the Frontiers of Flight by Dennis R. Jenkins

Author:Dennis R. Jenkins
Language: eng
Format: mobi, epub
Tags: X-15, NASA, X15, Aerospace
Publisher: NASA
Published: 2010-02-01T09:00:00+00:00

Researchers at Ames modified a North American JF-100C (53-1709) Super Sabre into a variable-stability trainer that could simulate the X-15 flight profile somewhat more convincingly than the NT-33, making it possible to investigate new piloting techniques and control-law modifications without using an X-15. The most limiting factor was that the JF-100C was a single-seat aircraft, meaning there was not a safety pilot to assist if things went wrong. (NASA)

There were two other answers to the PIO problem at high angles of attack. The first was to make the stability augmentation system truly redundant, at least in the roll axis, by installing the alternate stability augmentation system (ASAS); however, this took almost a year to accomplish. Another answer–discovered by Dick Day and Bob Hoey using the simulator–proved to be remarkably easy, and unexpected: remove the ventral rudder. With the lower rudder on, a considerable portion of the reentry from an altitude mission would be within the uncontrollable region should a damper fail. However, a similar reentry with the lower rudder removed would not enter the predicted uncontrollable region at all. The downside was that the pilots faced significantly reduced flying qualities at low angles of attack without the rudder. Despite a few gripes from the pilots, everybody eventually agreed to remove the lower rudder for almost all of the high-altitude missions. Only a few missions of the X-15A-2 used the ventral rudder, which in this case provided an adequate stand-in for the eventual dummy ramjet. In all, the program would make 73 flights with the ventral rudder on and 126 with it off.[74]

By the time of the 1961 industry conference, researchers had determined that the fixed-base simulator and the F-104 in-flight landing pattern simulator were the two most valuable training tools available to the program. The centrifuge and variable-stability aircraft contributed to the overall pilot experience level, but were not necessary for use on a flight-by-flight basis. This mostly explains why only the first group of pilots got the thrills of "riding the wheel" at Johnsville and flying the NT-33 trainer.[75]

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