Summary: Auxiliary Power Units (APUs) are common in today’s commercial airliners.
One question that’s often asked by aviation enthusiasts and onlookers alike are whether or not airplanes can operate without an Auxiliary Power Unit (APU). The answer is yes, you can. If the APU is not operating, maintenance will operate under the stipulations of the MEL. Now, it’s important to remember that it may restrict certain operations, but if the route was completely over land, there is no effect other than the need for ground maintenance equipment like a lithium ion starting unit for example.
What Are the Requirements?
An airplane that does not have an APU requires a ground cart at the airport. Ideally, there would be one at the end locations as well, but if that is not available, then the engine could be left running during the run. If there is no ground power unit or any other Start Pac unit on hand, the aircraft will be directed to an area where designated ground power is available.
The general process of a non-APU plane is to keep ground power and air conditioning hooked up to the airplane for pre-flight activity and during the boarding process. Once the plane closes up, the ground crew will coordinate with the maintenance team to provide air via the ground power unit or card, followed by one of the engines starting up.
Once the engine is running, the maintenance team will disconnect the ground equipment and start pushing back. During the taxi phase, if one engine is started, there will be a crossbleed performed to start the other engine. The configurations may be different than those that do have an APU but once the