Figure 3-19.Stationary pit-type scales.

 of gravity of aircraft (as well as wheeled vehicles and cargo loads). The complete system is portable and includes a trailer for storage and transport, or it is mounted on a single 88- by 108-inch pallet. Typical installation setup time by two men is 30 minutes.

HEAVY-DUTY PORTABLE SCALES. This system is designed to provide weight only. Wheeled vehicles and cargo may also be weighed on these scales. The complete system is portable and completely self-contained. Platform size is small, but it may be increased by connecting two scales with a factory provided charnel. Because of the small platforms, you must exercise care when using this system. Typical installation setup time by two men is 10 minutes.

STATIONARY PIT-TYPE SCALlES. Most of the large scales are of the stationary-beam and lever-balance type. See figure 3-19. These scales are commonly flush floor installations, although some are used as surface-type portable scales. The flush floor installation generally is in a permanent location, and the aircraft must be taken to it. However, some flush floor scales have the capability to be removed from their installations, when necessary, and taken to the aircraft. These scales are usually expensive and normally require a special building or hangar.

Weighing with calibrated scales is the only sure method of obtaining an accurate basic weight and center of gravity location on an aircraft. The large stationary pit-type scales must be calibrated or certified correct at least once every 12 months. Heavy-duty portable scales and MEWS scales must be calibrated at least once every 6 months.