W&B 2-6

The position of the fore and aft CG limits is measured as a percentage of MAC from the MAC leading edge. Usually for a single or two-seat aircraft, the most forward position would be forward of 30–35 percent MAC. Thus, the allowable CG range in a light aircraft should not exceed 20 percent MAC. Note: For a rectangular width of constant airfoil section dimensions, MAC is just the chord. For a symmetrically- tapered wing, it is the average of the root chord and the tip chord. FAA-Furnished Weight and Balance Information The information discussed to this point can be readily applied to any aircraft weight and balance problem. To apply the techniques, certain elements of information are required. This information is obtained from both FAA documents and manufacturer provided data. Before an aircraft CG can be computed, certain information must be known. This information, furnished by the FAA for every certificated aircraft in the Type Certificate Data Sheets (TCDS) or Aircraft Specifications, can be accessed at www.faa.gov. When the design of an aircraft is approved by the FAA, an Approved Type Certificate and TCDS are issued. The TCDS includes all of the pertinent specification for the aircraft; at each annual or 100-hour inspection, it is the responsibility of the inspecting mechanic or repairman to ensure that the aircraft adheres to them. A note about the TCDS: aircraft certifi ated before January 1, 1958, were issued Aircraft Specifica ions under the Civil Air Regulations (CARs), but when the Civil Aeronautical Administration (CAA) was replaced by the FAA, Aircraft Specification were replaced by the TCDS. The weight and balance information on a TCDS includes CG range, empty weight CG range (EWCG), maximum weights, number of seats, maximum baggage, fuel capacity, oil capacity, and datum location. Data pertinent to an individual model is located in its respective section of the TCDS. Use the TCDS excerpts in Figure 2-15 to verify the following for a Cirrus Design Corporation SR 20 normal category: CG Range S/N 1005 through 1147: Forward Limits: 138.7 inches at 2,110 lb with a straight line taper to 141.0 in at 2,694 lb and 143.0 in at 2,900 lb Aft Limits: 144.6 in at 2,110 lb, with straight line taper to 147.4 in at 2,570 lb, and to 147.9 in at 2,745 lb, and 148.2 in at 2,900 lb S/N 1148 through 1877, 1879 through 1885, and S/N 1005 through 1147 if Cirrus Service Bulletin SB 20-01-00 is complied with: Forward Limits: 138.7 in at 2,110 lb with a straight line taper to 141.0 in at 2,694 lb and 144.1 in at 3,000 lb Aft Limits: 144.6 in at 2,110 lb, with straight line taper to 147.4 in at 2,570 lb, and to 148.1 in at 2,900 lb, and 148.0 in at 3,000 lb S/N 1878, 1886 and Subsequent: Forward Limits: 137.8 in at 2,100 lb with a straight line taper to 139.1 in at 2,700 lb, and to 140.7 in at 3,050 lb Aft Limits: 148.1 in at 2,100 lb, with straight line to 148.1 in at 3,050 lb Empty Weight CG Range (EWCG) When all of the seats and baggage compartments are located close together, it is not possible (as long as the EWCG is located within the EWCG range) to legally load the aircraft so that its operational CG falls outside this allowable range. If the seats and baggage areas extend over a wide range, the EWCG range is listed as “None.” Maximum Weights The maximum allowable takeoff and landing weights and the maximum allowable ramp weight are given. This basic information may be altered by a note. Notes are found in data pertinent to all models. An example would be Note 6 at the end of Figure 2-15. Number of Seats The number of seats and their arms are given in such terms as: 4 (2 at 143.5 aft of datum, 2 at 180 aft of datum). Maximum Baggage Maximum baggage for this model is 130 pounds at 208 inches. Fuel Capacity This important information is given in such terms as: 60.5 gal at 153.75 in. Usable: 56 gal (See Note 1). Notes can be found in data pertinent to all models. Oil Capacity (Wet Sump) The quantity of the full oil supply and its arm are given: 8 quarts at 76.2 in.