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Aircraft Instruments: Types & Examples

Instructor: David Wood

David has taught Honors Physics, AP Physics, IB Physics and general science courses. He has a Masters in Education, and a Bachelors in Physics.

An aircraft cockpit is a dizzying array of dials and instruments. Learn about the various types of instruments that pilots use to understand the position, orientation and motion of the plane.

What Are Aircraft Instruments?

When you're driving a car, it's pretty easy to see where you are and what direction you're going. You just look out the window. There are signs to help you, and your phone's GPS can even direct you. But imagine if the GPS was all you had - imagine if there was a fog so thick you can see more than a few feet in front of you. This is a lot closer to what it's like to fly an aircraft.

Aircraft instruments are the various displays and dials in an aircraft that the pilots use to allow them to understand where the plane is and what it is doing. Pilots rely on these instruments, especially when they're tens of thousands of feet in the air and might not be able to see anything because of the clouds. But even if they could see, the earth is so far away that it is extremely difficult to tell, for example, how your altitude is changing. You can drop a long way before the earth starts to look any different. That's where an aircraft's instruments become useful.

Basic airplane cockpit
Basic airplane cockpit

In this lesson, were going to take a look at the various instruments you'll find inside the cockpit of a typical plane: instruments to describe your position and instruments to describe the way the plane is moving.

Describing Position and Orientation

Describing a position is about figuring out exactly where you are in relation to the features of the earth. If you're flying above Paris, you might know exactly where you are when you see the Eiffel tower. But most of the landscape is pretty nondescript and hard to identify.

You can describe the position of a plane in terms of the altitude of the plane and what part of the earth it is above. But you can also describe the position of plane relative to a planned course and how the plane is tilted or oriented.

An altimeter is an instrument that describes the aircraft's altitude above sea level by measuring the atmospheric pressure.

Altimeter
Altimeter

A course deviation indicator (or CDI) is an instrument that describes an aircraft's lateral position (side to side) relative to a planned course.

Modern aircraft will have a regular satellite navigation system (GPS system) that shows the plane's position relative to the features on the ground. Though this is mostly used by pilots - air traffic control is done through radar systems.

An attitude indicator is a display that shows an artificial image of a horizon and how the aircraft is positioned relative to the horizon. Basically, it tells the pilot whether the wings are level or tilted to one side (the roll or bank of the plane). It also tells the pilot whether the nose of the plane is pointing above or below the horizon (the pitch of the plane). Pilots know how to fly the plane without this instrument, but it really helps in low visibility and is considered extremely important.

Attitude Indicator in Detail

The attitude indicator can be a little hard to understand, so let's take a closer look at its components. The attitude indicator contains three main elements: the fuselage silhouette, which represents the plane, the horizontal line that represents the horizon, and the carrot (small triangle at the very top), which shows whether the plane is level, banking left, or banking right.

Attitude indicator
Attitude indicator

The fuselage silhouette is probably the hardest to identify: it's a line with a semi-circle or triangle in the middle, that has a vertical line in the middle. The center of the silhouette is the main thing to focus on: if that central dot is below the horizontal line (artificial horizon), the plane is descending (diving), if it's on the horizon, the plane is level, and if it's above the horizon, the plane is ascending (climbing).

The carrot tells you whether the plane is banking. If the carrot points to the right, the plane is banking left, and if it points to the left, the plane is banking right.

Describing Motion and Direction

The other kind of instruments you'll find a plane our insurance to describe the motion of the plane - how fast it's moving, whether it's going up or down, and what direction it is moving.

An airspeed indicator tells the pilot how fast the plane is moving relative to the surrounding air (measured in knots). It does this by comparing the pressure moving through the aircraft to the atmospheric pressure nearby. The number on the airspeed indicator is known as your perceptual speed. To know your true speed, you have to adjust for the local air pressure and temperature.

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