human factors

15-2 Handbook of Aviation Human Factors
Sperry Flightray was evaluated on a United Air Lines “Flight Research Boeing” (Bassett & Lyman, 1940).
The fact that all operators, private, commercial, and military, have flown with instruments incorporating
all three designs also makes the era’s boundaries fuzzy.
For the purpose of this section, we shall consider the mechanical era as that time from the beginning
of flight until the introduction of the Integrated Instrument System by the Air Force in the late
1950s (Klass, 1956). The E-M era extends from that point until the introduction of the U.S. Navy’s
F-18 aircraft, which makes extensive use of multipurpose CRT displays. The issues of the E-O era, and
beyond, comprise the primary subject matter of this chapter.
15.1.1.1 The Mechanical Era
The importance of instrumenting the information needed to fly an airplane was recognized by the
Wright brothers very early in their flying adventures. The limitations of measuring airspeed by the force
of the wind on one’s face were not very subtle. From the time these famous brothers first installed an
anemometer, a mechanical device used to measure wind velocity, and a weather vane to measure the
angle of incidence, aviators and designers have been concerned about crew station instrument issues
such as weight, size, shape, accuracy, reliability, and environmental effects (Nicklas, 1958). As aviators
gained more flying experience, they recognized the need for additional pieces of information in the crew
station, which in turn meant that there was a need for some kind of instrument. It did not take many
engine failures before the need for data that would warn of an impending failure became obvious.
The requirement for displaying most pieces of information in a crew station can be traced to the need
to identify or solve a problem. So the research process during most of the mechanical era was to invent
a device or improvise from something that already existed in the nonaviation world. Any testing was
generally done in flight. Simulators, as we have come to know them over the past 35 years, were virtually
nonexistent during the mechanical era. The first simulators were modified or upgraded flight trainers,
and were not generally regarded as an adequate substitute for flight trials. During this era, it was not
unusual for a potential solution to progress from conception to a flight trial in a matter of weeks as
opposed to the years it currently takes.
It would certainly be wrong to leave one with the impression that the mechanical era was one of only
simple-minded evolutionary changes in the crew station. On the contrary, the history of instrument
flying, even as we know it today, can be traced back to the early flying days of Lt. James Doolittle of the
Army Air Corps (Glines, 1989). In 1922, he performed the first crossing of the United States accomplished
in less than 24 hours. Hampered by darkness and considerable weather, he claimed that the trip
would have been impossible without the “blessed bank and turn indicator,” an instrument invented in
1917 by Elmer Sperry. In his Gardner Lecture, Doolittle claimed that it was the “blind flying” pioneering
exploits of a number of other aviators that provided the “fortitude, persistence, and brains” behind the
blind flying experiments of the 1920s and early 1930s (Doolittle, 1961). In 1929, Doolittle accomplished
the first flight that was performed entirely on instruments. It was obvious to these pioneers that instrument
flying, as we know it today, was going to become a pacing factor in the future of all aviation.
Although many milestones in the development of instrument flying technology took place in the
mechanical era, technology had advanced sufficiently by 1950 to begin to shift the emphasis from
mechanical instruments to instruments powered by electricity.
15.1.1.2 The Electromechanical Era
As mentioned earlier, this era began when the United States Air Force (USAF) introduced the Integrated
Instrument System, often simplistically referred to as the “T-line” concept, for high performance jet aircraft.
This was the first time that the USAF had formed an internal team of engineers, pilots, and human
factors specialists to produce a complete instrument panel. The result was a revolutionary change in how
flight parameters were displayed to pilots. These changes were necessitated because aircraft were flying
faster and weapons systems were becoming more complex. This complexity reduced the time available
for the pilot to perform an instrument cross check, and the fact that each parameter was displayed on