Center of gravity shift refers to the change in the position of an aircraft's center of gravity (COG) during different phases of flight or as a result of loading and unloading operations. These shifts must be continuously monitored and controlled to ensure that the COG remains within the certified range, which is critical for safe and stable flight.
When and why the COG shifts
Before the flight (static displacements)
Passenger seats
An uneven distribution of passengers can influence the COG. For example, if many passengers are seated at the front of the aircraft, this can shift the COG forward.
Placement of the load
The distribution of the cargo in the front or rear cargo compartments can influence the COG. Uneven loading can lead to a shift in the COG.
Fuel distribution
The distribution of the fuel in the main tanks and trim tanks can influence the COG. Different fill levels in different tanks can lead to a shift in the COG.
During the flight (dynamic displacements)
Fuel consumption
Fuel is consumed during the flight, which leads to a shift in the COG. If fuel is consumed from the front or rear tanks, this can shift the COG forwards or backwards.
Fuel transfer
Some aircraft, such as the Airbus A340, use trim tanks to actively control the COG. By redistributing fuel between different tanks, the COG can be specifically influenced.
Payload drop
In the case of military or cargo aircraft, it may be necessary to drop loads during the flight. This can lead to a sudden shift in the COG, which must be controlled accordingly.
Crew/passenger movements
In smaller aircraft, moving people can noticeably shift the COG. If passengers or crew members move around inside the aircraft, this can affect the COG.
Importance of monitoring and controlling the COG
Security and stability
Continuous monitoring and control of the COG is crucial to ensure the safety and stability of the aircraft during all phases of flight. A COG outside the certified range can lead to instability and dangerous flight conditions.
Flight performance
An optimally positioned COG contributes to improved flight performance, including fuel efficiency and maneuverability.
Compliance with certification
Compliance with the certified COG limits is a prerequisite for certification and safe operation of the aircraft.
Monitoring and controlling the center of gravity shift is therefore a key aspect of flight safety and efficiency that requires careful planning and continuous adjustments during the flight.
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