Technology
Are Jet Engines Turned Off While the Plane is on the Ground?
Are Jet Engines Turned Off While the Plane is on the Ground?
When you're at the airport, you might notice that the jet engines of parked aircraft aren't always turned off. This can be a bit confusing, especially if you're not familiar with the inner workings of commercial aircraft. Let's delve into the reasons why jet engines are sometimes left running and when they are turned off.
Why Jet Engines Aren't Always Turned Off
The primary reason for leaving jet engines running while the plane is on the ground is the Auxiliary Power Unit (APU). The APU is a small gas turbine often located in the tail of the aircraft. It serves several purposes, including:
Generating electricity for onboard systems Providing air for cabin ventilation and air conditioning Supplying bleed air to the air conditioning packsDuring the initial taxi and during short layovers, the APU is activated to ensure a steady supply of power and conditioned air. Additionally, it simplifies the process of getting passengers on and off the plane by providing additional power to operate equipment like the air conditioning units and catering services.
When Are Jet Engines Turned Off?
Typically, the jet engines are turned off when the plane has finished its duties on the ground. This happens during the following scenarios:
When the plane has arrived at its destination and is being prepared for disembarkation During long layovers where the plane will be parked for an extended period When the plane has left the gate and is taxiing to the runway for takeoffHere's a more detailed look at these transitions:
1. After Landing
Immediately after landing, the engines are reduced to idle and often start shutting down. This process takes a few minutes, during which the APU is typically turned on to take over the power and air conditioning duties. Once the APU is functional, the engines are allowed to cool down and eventually shut off.
2. Long Layovers
During long layovers, the engines may be turned off as the plane is parked in a hanger or tied down and locked up for the day. This is because extended periods without engine operation allow for maintenance checks, refueling, and preparation for the next flight. The APU can still provide power and air conditioning during these layovers, ensuring that no systems are affected.
3. Taxiing to the Runway
Before a plane taxis to the runway for takeoff, the engines are fully shut down. This is a standard procedure to prepare for departure and ensure safety. The APU is also turned off at this point, and all systems revert to pre-takeoff configurations.
Parking and Maintenance
When a plane is parked between flights, it is usually either in a hanger or temporarily secured on the tarmac. In hangers, planes can undergo maintenance and checks without the need for the engines to remain running. On the tarmac, the plane may be tied down for safety reasons and secured with chocks to prevent movement. The engines are shut down in these conditions to prevent unnecessary fuel consumption, wear, and to ensure the safety of ground personnel.
Safety Measures
To ensure the safety of passengers, crew, and ground staff, jet engines are turned off when the plane is on the ground. Engaged engines pose a significant risk of injury or engine ingestion accidents during taxiing and takeoff. By shutting down the engines, these risks are greatly reduced, making the boarding and disembarkation processes safer.
Conclusion
While it may seem unusual to see jet engines running on parked aircraft, there is a practical reason behind this practice. The APU serves as an essential power source during short layovers and taxiing, ensuring that the aircraft remains functional and efficient. Understanding the roles of the APU and the engine shut-off process helps demystify the operations at the airport and enhances the overall safety and efficiency of commercial aviation.