Performance, Weight and Balance, and Flight Planning
This domain ties the airplane's certified limits to the runway, terrain, and fuel you actually have. Expect chart reading, required climb gradients, CG arithmetic, and fuel/reserve planning in both normal and single-engine cases.
Takeoff and climb requirements
- Transport-category takeoff data must satisfy accelerate-stop distance, accelerate-go distance, and the net takeoff flight path.
- Second-segment climb gradients are 2.4% (two engines), 2.7% (three), and 3.0% (four). The net flight path is the gross gradient minus 0.8%, 0.9%, or 1.0% respectively. The landing climb requirement is 3.2%.
- V speeds (V1, Vr, V2, Vmcg) shift with weight, temperature, pressure altitude, and bleed or anti-ice configuration.
Weight, balance, and runway
- Compute %MAC from the leading edge of the mean aerodynamic chord. Fuel burn moves the CG, so check the zero-fuel-weight CG as well as takeoff CG.
- Weight-shift formula: (weight moved × distance moved) ÷ total weight = CG shift.
- Jet fuel is about 6.7 lb/gal; avgas is 6.0 lb/gal. Convert volume to weight before any comparison.
Flight planning
- Fuel = taxi + trip + contingency + alternate + final reserve (45 minutes for turbine aircraft) plus any holding or ETP penalty.
- Regulated takeoff weight is the lowest of the structural, performance, and field-length limits.
- Driftdown and equal-time-point planning show whether a single-engine diversion stays terrain-safe.
Worked example
A 10,000 lb airplane with CG at 140 in moves 200 lb aft from station 100 to station 250. Shift = 200 × 150 ÷ 10,000 = 3.0 in aft, so the new CG is 143 in. With LEMAC at 120 in and MAC 100 in: (143 − 120)/100 = 23% MAC, inside a 12–30% envelope - but the zero-fuel case must still be checked.
Traps
Reading gross instead of net gradient; using avgas density for jet fuel; forgetting that fuel burn changes CG; omitting APU fuel; taking chart values for the wrong bleed configuration.