How Airplanes Work

By: Marshall Brain, Robert Lamb & Brian Adkins

Flight Instruments

Flight instruments help pilots keep an eye on conditions.
Flight instruments help pilots keep an eye on conditions.
Sami Sarkis/ Photographer's Choice RF/Getty Images

To the untrained eye, a panel of flight instruments may seem like a smorgasbord of dials. But all these crucial gauges provide a pilot with critical data during the flight. The six most basic flight instruments, as found in a simple prop-driven plane, are as follows:

  1. Airspeed indicator: Essentially, this gauge tells the pilot how fast the aircraft is traveling in relation to the ground. The indicator depends on a differential pressure gauge, not unlike a tire gauge.
  2. Altimeter: As the name implies an altimeter measures altitude. The indicator in this case is a barometer, which measures air pressure.
  3. Attitude indicator: Remember the three primary principle axes we mentioned before (pitch, yaw and roll)? Well, an attitude indicator illustrates the aircraft's orientation along all three. By use of a gyroscope, the indicator provides spatial clarity even in disorienting flight conditions.
  4. Heading indicator: The heading indicator simply tells the pilot in which direction the plane is heading. The device depends on both a gyroscope and a magnetic compass, however, as both are susceptible to different errors during flight.
  5. Turn coordinator: A typical turn coordinator indicates the plane's yaw or roll rate while also indicating the rate of coordination between the plane's bank angle and the rate of yaw. This device depends on a gyroscope, as well as an inclinometer ball in a glass cylinder to indicate when the aircraft is skidding or slipping.
  6. Variometer: Also known as a vertical speed indicator, this device indicates the rate of a plane's rate of climb or descent. Working along similar lines as the altimeter, the variometer depends on atmospheric pressure readings to determine how swiftly altitude changes are occurring.

The total number of flight instruments has increased over the years with the speed, altitude, range and overall sophistication of the aircraft.