Flight instruments are the gauges, indicators and warning systems in the cockpit of an aircraft. This equipment helps the pilot fly the aircraft safely under a variety of flight conditions, day or night. The instruments relay vital information about the aircraft's systems, condition and performance throughout the flight, and it is possible, and sometimes necessary, for a pilot to operate the aircraft relying solely on the instruments.
The variety and complexity of an aircraft's flight instruments depend upon the type of aircraft and its intended use. Single propeller airplanes generally require less sophisticated instrumentation than twin propeller planes. While most aircraft — airplanes and helicopters — require an altimeter, airspeed indicator and heading indicator, there are certain types of aircraft such as homemade experimental aircraft, ultralights, gliders and others, that can be flown entirely free from the reliance on flight instruments in favorable weather conditions. Many pilots, private, commercial and military, also rely on radio navigation aids such as very high frequency omnidirectional range (VOR) finders to help maintain course.
In the United States, there are two sets of regulations that govern flying — visual flight rules and instrument flight rules. The former govern the operation of aircraft when the pilot is flying primarily on visual cues, while the latter govern instances in which pilots choose to or are forced to use their instrumentation only. In practice, pilots use a combination of both visual cues and instrumentation during flight, but a pilot must earn a supplemental certification in order to fly an aircraft on instrumentation alone. The additional training includes extended flight hours with an emphasis on instrument flying. The certification is issued by the aviation authority of the country in which the pilot resides.
For larger commercial aircraft, such as jetliners, and military planes, flight instruments are much more technologically advanced. Electronic heads-up displays allow fighter pilots to keep their eyes on the skies, showing the most pertinent flight data on a see-through projection that is always in the pilot's line of sight. Sophisticated navigation equipment, including a computer-actualized compass, automated course maintenance computer, and other instruments, are used on large commercial airliners to allow the flight crew to better control the aircraft.
Flight instruments are usually organized within the cockpit of the aircraft in a way that provides the pilot with a fluid, seamless view of the gauges and indicators. Traditionally, flight instrumentation is displayed in either an analog or a digital format, but with the growing computerization of flight controls, instruments are becoming completely electronic. Electronic flight instruments differ from digital instruments in that a digital readout displays the data from the same sensor that analog instruments utilize. Electronic instruments, on the other hand, use computing processors rather than mechanical devices to gather and transfer flight data.