Learning Objective: Identify the various methods of weighing aircraft, and recognize the flight characteristics of the improperly weighed or balanced aircraft.

Figure 3-18.Mobile Electronic Weighing System (MEWS).

Flight characteristics of aircraft are directly dependent upon their weight and balance conditions. An aircraft whose weight is greater than its allowable maximum gross weight, or whose center of gravity (cg) is located outside its prescribed cg limits, may experience one or more unsatisfactory flight charact-eristics. Some of these conditions are longitudinal instability, increase in takeoff distance, increase in control forces, increase install speeds, decrease in flight range, and a decrease in rate of climb. The requirements, procedures, and responsibilities for aircraft weight and balance control are defined in the technical manual, USN Aircraft Weight and Balance Control, NAVAIR 01-1B-50. Additional requirements and/or procedural instructions for specific TYPE/MODEL/SERIES aircraft weight and balance control are specified in the aircraft's NATOPS manuals and the technical manual, Weight and Balance Data, NAVAIR 01-1B-40. In case of conflicting requirements, procedures, or instructions, OPNAVINST 4790.2 and the NATOPS manual shall take precedence over this manual and NA01-1B-40, and this manual shall take precedence over the NA 01-1B-40, pending mandatory resolution of the conflict through the procedures described in the NA01-1B-50.

One of the basic elements of aircraft design is aircraft weight and balance. The estimated weight and balance of an aircraft is used in determining such design criteria as engine requirements, wing area, landing gear requirements, and payload capacity. Any weight change, either in manufacturing, modification, or maintenance, will have distinct effects on aircraft performance and/or payload capability. Figure 3-17 shows the meaning of, and relationships between, aircraft weight terminology. All aircraft are designed with a number of weight limits. These limits are determined by performance, control, and structural restrictions. Exceeding these limits may result in a loss of the aircraft, and is expressly forbidden.

If the aircrafts actual weight exceeds the design weight, the result is reductions in performance and/or payload. An increase in gross weight increases takeoff speed, stalling speed, and landing ground run. The rate of climb, ceiling, and range decreases with increasing gross weight. If the operating weight increases while performance requirements remain the same, then the payload and/or fuel load must decrease. The weight of an aircraft is determined through a combination of actual weighing, accurate record keeping, and proper use of the aircrafts NAVAIR 01-1B-40.

A variety of scales and equipment maybe used for weighing aircraft. At the present time, the method that has become the standard is the Mobile Electronic Weighing System (MEWS). Weighing systems now being used to weigh Navy aircraft are the MEWS, the heavy-duty portable scales, and the stationary pit-type scales.