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Aircraft Weight and Balance

Weight Shifting & Payload

Next to a good preflight plan and current weather report is a thorough Weight & Balance calculation. This is a matter of serious concern to all pilots as well as many other people involved in the flight.

The pilot has to personally assume the responsibility (and is required by law) because he has control over both the loading and fuel management, the two variable factors which can change both total W/B and the center of gravity.

This information is available to the pilot in the form of aircraft records, operating handbooks and placards in baggage compartments and or fuel caps. The owner of the aircraft has the responsibility to make sure that up to date information is available to the pilot.

While performing the W/B calculations it is sometimes necessary to move cargo or passengers about the aircraft to remain within the center of gravity limits, on this page we show some easy formulas to do just that.

Weight shifting

The pilot has a couple of things when the C of G is not within limits after calculating the numbers. Defueling the aircraft (may not be viable) or redistributing cargo or passengers are some of the options. But how much and how far? You can shift a passenger in your W/B form and recalculate but there is an easier solution.

For this problem we have this basic formula:

distance weight shifted x weight shifted = total weight x Change of C of G

Thus, to recalculate the distance to shift a certain weight do this:

distance weight shifted = (total weight x Change of C of G) / weight shifted

Alternatively, if we knew the distance the weight must shift but want to know how much weight:

weight shifted = (total weight x Change of C of G) / distance weight shifted

The above formula makes it easy to recalculate any weight change in the aircraft without redoing the complete W/B form all over again.

Maximum payload available

On some aircraft there maybe an requirement to find the payload available. This may depend on the MZFW (aircraft limited), the MTOW or even the MLW. The last two will apply to any flight.

To be able to calculate the payload, one will need the aircraft Basic Empty Weight and the weight of the crew and everything they need. This results in a Basic Operating Weight (BOW). The table below then gives an idea on how to calculate the payload under different circumstances.

minus---nil---total fuel weightlanding fuel weight
= max payload available

MZFW is the maximum weight the aircraft may have without fuel. Any weight above this MUST be fuel, simple as that. This is a limitation in the airframe structure.

Finally: remember to always secure the cargo just in case unexpected turbulence is more than comfortable.

Written by EAI.

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