Performance and Weight and Balance
Core concepts
The flight engineer must compute takeoff, climb, cruise, and landing performance and verify the aircraft stays within weight and balance limits. Know maximum takeoff weight, maximum landing weight, maximum zero-fuel weight, and operating empty weight, and how each constrains the others. Understand the takeoff distance components (ground roll, rotation, airborne segment to 35 ft), the effect of density altitude, wind, slope, and contamination. Climb performance depends on excess thrust; cruise performance on specific range. For weight and balance, know the datum, arm, moment, and center of gravity, and how CG position affects stall speed, stability, and trim drag.
Traps in questions
A classic trap is forgetting that maximum landing weight may require a fuel jettison or hold before landing after an overweight takeoff. Another is assuming aft CG always improves performance - it reduces trim drag but degrades stability and can reduce stall margin. Watch for questions that mix density altitude with pressure altitude; density altitude is what the aircraft 'feels'.
Worked example / rule of thumb
To find CG: divide total moment by total weight. If a 100 kg load moves 2 m aft, the moment change is 200 kg·m; divide by total weight to find the CG shift. Rule of thumb: high, hot, humid, and heavy all hurt performance - the 'four Hs' of degraded takeoff.