Mass and balance, performance and navigation logs
Mass and balance, performance and navigation logs
This domain tests whether the aircraft is legal and whether the numbers on the nav log survive a change of wind or load.
Mass and balance. Moment = weight × arm. Total moment divided by total weight gives the CG arm. Percentage MAC = (CG arm − LEMAC) / MAC length × 100. Check maximum take-off and landing weights, zero-fuel weight, and the forward and aft CG limits for the take-off and landing configuration.
Performance. Density altitude = pressure altitude + 120 × (OAT − ISA temperature). Use the AFM/POH charts for take-off and landing distance, then apply wind, slope, temperature and runway surface corrections; the result must not exceed TODA, TORA or ASDA as appropriate.
Nav log. Columns: leg, track, TAS, wind, heading, GS, distance, time, fuel, ETA/ETI. Recompute the remaining legs after each fix rather than carrying a stale GS.
Worked example. Weight 2,000 kg at arm 40 in; add 200 kg at arm 80 in. Moment = 2,000×40 + 200×80 = 80,000 + 16,000 = 96,000 kg·in; weight = 2,200 kg; CG = 96,000/2,200 = 43.6 in. If the aft limit is 44 in, the load is legal but close.
Traps. Forgetting crew and fuel in the basic empty weight; using the wrong arm for a seat row; treating density altitude as pressure altitude; and not rechecking landing weight and CG after fuel burn.