Understanding the Start-Up Process for Jet Engines

Summary: The jet engine startup process does NOT require ground support in certain occasions.


When it comes to airplanes taking off while sitting amongst the traffic queue of other airliners, there needs to be a spark, per say to ignite the engines and fire them up so they can launch at full speed to become airborne. Now, back in World War II, jet engines have a motor built-in that possessed the capability of getting the turbines to spin fast enough for a start, but in today’s modern airline industry, modern commercial engines needs some type of external assistance to fire up.


Contrary to what many people think about the liftoff process, there are numerous engines that can fire up without the need for ground support or a portable power pack for example. Modern jet aircraft have APUs built-in that will be running if the engines aren’t.

Now, the batteries on the jets typically do not work very long with the electrical buses energized and one of the first things that one must do is after turning on the batteries is to see if they are correctly working, followed by starting up the APU – this is assuming that there is no Ground Power Unit (GPU) hooked up at the time. If a GPU is attached from Start Pac, then the APU will be deferred until the GPU is completely disconnected.

Bleed Air Source

Any aircraft on a no-engine taxi to the runway will have an APU running constantly to provide electricity throughout the plane along with bleeding air to provide air conditioning to the passengers while in waiting. Now, it’s important to remember that some aircraft are better at doing this than others, so keep this in mind. Now, when it’s time to start the engines, they can be started utilizing the APU, which is essentially a bleed air source and an ideal method of starting the plane.