Performance and limitations — density altitude, weight & balance
**Density altitude** is pressure altitude corrected for nonstandard temperature. It determines aircraft performance. Rule of thumb: DA increases ~120 ft for every °C above standard (15°C at sea level). A hot, high, humid day can easily add 3,000 ft of DA, extending takeoff rolls by 25% or more and reducing climb rate proportionally.
**Weight and balance:** the aircraft must be loaded within both the maximum gross weight and the published CG envelope. Forward CG increases stability but raises stall speed and extends takeoff/landing rolls. Aft CG reduces stability (and in extreme cases, recovery from stalls/spins) but improves cruise efficiency.
Calculation: for each item loaded (pilot, passengers, fuel, baggage) compute Moment = Weight × Arm (distance from datum). Sum moments and weights; CG = Σmoments / Σweight. Verify the point falls within the CG envelope at both takeoff and landing weights (fuel burn shifts CG).
**Takeoff and landing distances** in the POH are given for standard conditions on a paved, dry, level runway. Correct for pressure altitude, temperature (density altitude), wind (headwind reduces, tailwind extends — typically 10% per 2 kt tailwind), runway surface (grass adds ~15%; soft surface more), and slope. Always plan to use no more than 50% of available runway for a normal takeoff/landing — the remainder is safety margin.