How Are Airplane Engines Numbered?

Nothing in aviation is left to chance, everything must be clear and avoid any type of ambiguity. That is how flying has become over many years the safest means of transportation. So you might be asking yourself how are airplane engines numbered on modern jet airliners? I’ll be answering that question in this post.

How Are Aircraft Engines Numbered?

In many ways aviation resembles sea transportation. Starting from the flight crew uniforms which took inspiration and closely resemble those of maritime crews.

There is though another similarity to the maritime world. The left side of any boat and plane alike are referred to as the port side. That is the side passengers will always be boarded under normal circumstances.

Therefore engines will be named with progressive numbers with the smallest number further to the left and the highest on the end of the right wing.

Some Real Life Examples

Let me explain a little better with some real life examples. In the case of a twinjet, such as a Boeing 777 or an Airbus A350, the engine on the left hand side wing will be number 1 while number 2 would be the one mounted under the right wing.

In the case of a trijet number one will be under the left wing, number 2 will be mounted on the vertical stabiliser and number 3 under the right wing.

Last but not least the quadjet case. In this case the engine further on the left will be number 1 engine, the inner left will be number 2, inner right number 3 and outer right number 4.

Why Is This Important?

Numbering engines in a standard way is extremely important. In case of a malfunction and when declaring an emergency there must be no ambiguity regarding which is the affected engine. Getting these mixed up can lead to making errors with catastrophic implications. That is the reason jet-engines are numbered always in the same way as I just explained.