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National Advisory Committee for Aeronautics, Research Memorandum - Precautions for Flight Testing Near the Speed of Sound

From experience gained by RACA test pilots in flying at high
subsonic Mach numbers and from interpretation of the data obtained,
some general precautionary rules for test flying near sonic Mach
numbers have been formulated. The reasons for these rules are
discussed and observations are made with respect to the hazards
arising from undesirable stability and control characteristics
which have been noted in test flights of various airplanes.

This paper, although written primarily for the attention of
test pilots, contains general information of interest to those who
are concerned with various phases of flight testing near sonic Mach
numbers. It includes a check list for use in organizing and summa—
rizing pertinent information relative to the stability and control
characteristics of airplanes undergoing tests at high Mach numbers.

It is an indication of the progress made by aviation that there
are increasing numbers of test pilots now being confronted with the
special problems of‘flight testing near sonic Mach numbers. In this
special realm of study, the RACA has acquired a good many years of
experience with a variety of high—speed airplanes. Out of this
experience have come certain general rules of action and precautions
which have proven of such sound value that they should be useful to
all engaged in conducting high—speed flights. And in this work,
safety has more than its usual significance; it means not only the
safe return of the pilot and airplane but also the acquisition of
the knowledge which was the aim of the project. It is the purpose
of this report to present a technique for the safe conduct of flight
tests at high Mach numbers. Examples of troubles encountered with
a discussion of their significance are- included.

Based on flight—test experience it has been demonstrated that
several precautionary rules can greatly increase the safety of
flight tests near sonic speeds. These rules will be presented in
turn, and the reasons why the rules are considered advisable will
be discussed.