How is weight and balance curtailment calculated?

ForeFlight multi-pilot business and MFB accounts support weight and balance curtailment to accommodate standard average passenger weights. A curtailed envelope is more restrictive than the manufacturer’s envelope to account for variables. A curtailed envelope sacrifices loading capabilities for ease of use.

NOTE: In-flight passenger movement, average baggage weight, and passenger seating variation curtailment are not yet supported.

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Weight and Balance Envelope with Curtailed Limits

When the Standard Weights option is enabled in Weight & Balance, a dashed curtailed envelope is graphically displayed. The envelope is determined according to the guidelines and requirements of Advisory Circular 120-27F, which encompasses the following steps:

To protect against an all-male passenger flight, the difference between the male and average passenger weight is determined.
The standard deviation weight specified in More > Settings > Standard Weights (47 lbs by default) is multiplied by the aircraft’s row factor derived from Advisory Circular 120-27F Table D1.
The values from steps 1 and 2 are added together to determine the weight for curtailment.
To determine the curtailed weight’s moment, the curtailment weight is multiplied by each seat’s arm.
To determine the cumulative effect of curtailed weights, the curtailment weights and seat moments are added (forward to aft and aft to forward) to generate two running totals.
The aircraft’s cabin centroid is determined by multiplying the number of seats in a row by the row’s arm, adding those values together, and dividing by the number of total seats.
The cabin centroid moment is determined by multiplying the total curtailment weight (step 5) by the cabin centroid (step 6).
The difference between the forward-to-aft total seat moment and the aft-to-forward total seat moment (step 5) are compared to the cabin centroid moment (step 7).
The largest moment deviations from each comparison are identified and used to calculate the curtailment amounts. The deviation is divided by the corresponding weight to determine how much to curtail the envelope. For example, a deviation of 7980 in lbs at 10,000 lbs results in a 0.79-inch weight and balance curtailment.