Use of trim weights

Trim weights, also known as ballast, is additional weight intentionally added to an aircraft or vehicle to maintain or adjust its center of gravity (COG) within allowable limits. This practice is critical to ensure the stability and safety of the aircraft or vehicle during flight or cruise.

Purpose of the trim weight

Correction of imbalances

Trim weights are used to correct an imbalance that occurs when the natural loading of the aircraft/vehicle results in a COG that is too far forward or aft.

Compliance with the certified COG range

The use of trim weights ensures that the aircraft is operated within its certified COG range, which is essential for safe and stable flight.

Use of trim weights

Permanently installed fixtures

These weights are often placed in structural parts of the aircraft or vehicle such as tail sections, nose cones or equipment bays to ensure permanent balance.

Removable ballast

This is often used during flight tests, when reconfiguring payloads or during transfer flights to compensate for temporary imbalances.

Military or unmanned aerial vehicles

In these applications, trim weight is often used to compensate for asymmetric configurations of weapons or sensors that could affect the balance of the aircraft.

Operational considerations

Increase in unladen weight

The use of trim weights increases the empty weight of the aircraft, which in turn reduces the payload capacity. This must be taken into account during flight planning and execution.

Documentation:

The use of trim weights must be carefully documented. This includes:

• Weight and center of gravity reports: These reports contain detailed information on the weight distribution and COG of the aircraft.
• Flight books: All relevant data and changes that affect the operation of the aircraft are documented here.
• Loading documents: These documents contain information about the loading of the aircraft and the distribution of the payload.

The use of trim weights is therefore an important aspect of flight safety and efficiency that requires careful planning and documentation.