Getting to Grips with Aircraft Weight and Balance(106)

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Due to the large surface of the wings, the wind can affect the stability of the aircraft on ground by providing a lift force ahead of the center of gravity and as a consequence a rolling moment around the main landing gear group or the center gear if any. The following graph, provided in the limitation chapter of the weight and balance manual, enables to determine the maximum allowable wind for a given aircraft weight and center of gravity position, as shown in the example. It can help the operator establishing its own recommendations for loading and off-loading rules in windy conditions.

A. LOADING GENERALITIES

6. SECURING OF LOADS
6.1. Introduction
As per IATA AHM 311, all individual items of load, which by their nature, shape or density may constitute a hazard, shall be restrained. Restraint can be achieved by filling volumetrically the compartment, the net section or the ULD, or by tie-down.
Note: In IATA Airport Handling Manual (AHM) Compartments, net sections and ULDs are
considered to be volumetrically full when they are filled up to three-quarters (75%) of their
height.
Note 2 : this value is indicated as 80% of the height in Airbus Weight and Balance Manuals.

Pieces weighing 150 kg or more, when loaded as bulk in compartments or net sections should always be tied down, except on single sector flights when the compartments or net section is volumetrically full. Pieces weighing 150 kg or more, when packed in certified ULDs should be individually tied-down except when the unit is volumetrically full.
Note : the 150 kg figure is the value recommended in the AHM document, nevertheless each individual operator may define a lower value for Heavy Items definition.
6.2. Aircraft acceleration
6.2.1. Influence on cargo items
Anytime an aircraft accelerates, decelerates or turns, forces are generated on each cargo item. As a consequence, hazardous or heavy items must be tied-down in order to prevent them from moving, damaging the structure of the aircraft or crashing other cargo loads. The force generated by the movement of the aircraft depends on the aircraft acceleration and the weight of the piece.
LOADING LOADING

A. LOADING GENERALITIES

6.2.2. Load factor
The load factor represents the —apparent weight“, in a given direction, of an item submitted to an acceleration that can be caused by: a speed increase, a slow down, sideway movements or vertical drops.

Therefore, if an item weighing 1000 kg is submitted to a load factor of 1.5 in a given direction, the apparent weight of this item is equivalent to the weight of an item with a mass of 1500 kg and no load factor applied.
The operator has to forecast the restraint of heavy items in each direction, taking into account the maximum admissible load factors published in the limitation chapter of the weight and balance manual of each aircraft type. Each restraint must resist to the maximum apparent weight in each direction.
　
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