Creating a CG envelope is accomplished by following the three steps listed below.
- Locate the forward and aft CG limits for the aircraft. CG limits are either in the Limitations or Weight and Balance section of the aircraft's flight manual. The Weight and Balance section generally uses a two-dimensional graph to display limits.
- Flight manuals use weight and arm or weight and moment to define the aircraft's CG envelope. ForeFlight requires limits to be entered using weight and arm. If necessary, convert the moments from the aircraft's moment table to arms. For more information see: How to convert moment to arm.
- Once the aircraft's CG limts are located using weight and arm, enter the values in ForeFlight.
Locating CG Limits
If the aircraft's CG limits are given in a graph, the forward CG limits are typically on the left and aft limits on the right. To define an envelope, a minimum of four points are needed. At least two forward points are used to define forward CG limits (at the minimum and maximum weight). And two aft points are used to define aft CG limits (at the minimum and maximum weight).
If the aircraft's CG envelope is not rectangular in shape, each point where the CG envelope changes its angle will need to be added as a CG limit.
For example, the CG envelope below has three forward CG limit points in blue and two aft CG limit points in orange. The numbered list below corresponds to the numbers in the example CG envelope.
- The forward CG limit at the aircraft's maximum takeoff weight.
- The point (or points) where CG limits change with weight (depicted as a bend in the envelope).
- The forward CG limit at the aircraft's minimum weight. If no minimum weight is defined, use the aircraft's basic empty weight.
- The aft CG limit at the aircraft's maximum takeoff weight.
- The aft CG limit at the aircraft's minimum weight. If no minimum weight is defined, use the aircraft's basic empty weight.
Example CG Envelope
Entering CG limits in ForeFlight
To create a CG envelope, open your W&B Profile and select Edit.
- Scroll to the CG Limits section.
- Tap Add Foward Limit or Add Aft Limit until there are enough rows to define your envelope.
- Tap a forward or aft CG limit and enter the CG limit and its corresponding weight.
- Repeat step 3 until all limits are defined.
CG Limits from the flight manual CG envelope entered in ForeFlight
NOTE: Entering CG limits in order is not required. To help with the visualization of the CG envelope, entering higher weights at the top is recommended.