Powered parachutes have many of the same characteristics as weight-shift control aircraft when it comes to weight and balance. They have the same limited loading, with only one or two seats and a fuel tank. They also act like a pendulum, with the weight of the aircraft hanging beneath the inflated wing (parachute).
The point at which the inflated wing attaches to the structure of the aircraft is adjustable to compensate for pilots and passengers of varying weights. With a very heavy pilot, the wing attach point would be moved forward to prevent the aircraft from being too nose heavy. Figure 4-39 illustrates the structure of a powered parachute with the adjustable wing attach points.
Weight and Balance for Large Airplanes
Weight and balance for large airplanes is almost identical to what it is for small airplanes, on a much larger scale. If a technician can weigh a small airplane and calculate its empty weight and empty weight center of gravity, that same technician should be able to do it for a large airplane. The jacks and scales will be larger, and it may take more personnel to handle the equipment, but the concepts and processes are the same.
Built-In Electronic Weighing
One difference that may be found with large airplanes is the incorporation of electronic load cells in the aircraft’s landing gear. With this type of system, the airplane is capable of weighing itself as it sits on the tarmac. The load cells are built into the axles of the landing gear, or the landing gear strut, and they work in the same manner as load cells used with jacks. This system is currently in use on the Boeing 747-400, Boeing 777, Boeing 787, McDonnell Douglas MD-11, and the wide body Airbus airplanes like the A-330, A-340, and A-380.
The Boeing 777, utilizes two independent systems that provide information to the airplane’s flight management computer. If the two systems agree on the weight and center of gravity of the airplane, the data being provided are considered accurate and the airplane can be dispatched based on that information. The flight crew has access to the information on the flight deck by accessing the flight management computer and bringing up the weight and balance page.
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