PPL Flight Performance and Planning cheat sheet

Density altitude = pressure altitude + 120 x (OAT - ISA temperature at that level); ISA is 15 degC at MSL dropping 1.98 degC per 1000 ft.

Takeoff and landing ground roll varies roughly with the square of the density-altitude-induced true-airspeed change; a 10 percent increase in TAS at rotation increases ground roll by about 20 percent.

Headwind component = wind speed x cos(angle between wind and runway); crosswind component = wind speed x sin(angle). Use the 30/45/60 rule: sin 30 = 0.5, sin 45 = 0.7, sin 60 = 0.9.

Maximum crosswind demonstrated is published in the AFM/POH limitations section; it is a demonstrated value, not an absolute structural limit.

For climb gradient: gradient (percent) = (climb rate in ft/min x 60) / (ground speed in knots x 6076) x 100, or approximately climb rate / ground speed in nm/min.

Rate of climb depends on excess power; angle (gradient) of climb depends on excess thrust. Vx gives best angle, Vy gives best rate.

Service ceiling is where maximum rate of climb falls to 100 ft/min; absolute ceiling is where it reaches zero.

Landing distance increases with weight because approach speed (and hence kinetic energy) rises approximately with the square root of the weight ratio.

Wake turbulence avoidance: fly at or above the preceding heavier aircraft's flight path and touch down beyond its touchdown point.

Weight and balance: moment = weight x arm; CG position = total moment / total weight. Keep the result inside the forward and aft CG limits for all loading scenarios.

Forward CG raises stall speed, increases landing distance and elevator forces, and can reduce climb performance; aft CG reduces stability and can make stall recovery difficult.

Zero fuel weight = basic empty weight + payload; maximum zero fuel weight is a structural limit that must not be exceeded before adding fuel.

Use the load sheet or graph to convert fuel volume to mass: AVGAS 100LL is about 0.72 kg/L (6 lb/US gal); Jet A-1 is about 0.80 kg/L.

Fuel planning: trip fuel + contingency (typically 5 percent) + alternate fuel + final reserve (30 min for VFR, 45 min for IFR in many states) + taxi fuel.

Endurance = usable fuel / fuel flow; range = endurance x true airspeed. Convert TAS and fuel burn to specific range (nm per unit fuel) to compare cruise settings.

Pressure altitude = indicated altitude with altimeter set to 1013.25 hPa (29.92 inHg); true altitude corrects pressure altitude for temperature error, roughly 4 percent per 10 degC of ISA deviation.

QNH is the pressure at sea level; QFE is pressure at the aerodrome. Setting QFE makes the altimeter read height above the reference point.

Takeoff distance chart inputs: pressure altitude, temperature, weight, wind component, runway slope, and surface condition. Apply each correction multiplicatively in the order given by the chart.

Runway slope effect: approximately 5 percent increase in takeoff distance per 1 percent upslope; landing distance increases about 10 percent per 1 percent downslope.

Grass, wet, or contaminated runways increase ground roll; standing water can add significantly to landing distance and risks aquaplaning above about 8-9 knots per unit of tyre pressure.

V speeds: V1 decision speed, VR rotation, V2 takeoff safety speed, Vref landing reference speed (typically 1.3 Vso).

Stall speed increases with the square root of the load factor: Vs at 60 degrees bank (n = 2) is about 1.41 times Vs level.

For a given weight, the glide speed for maximum range is the speed for minimum drag (best L/D); headwind raises it, tailwind lowers it.

Cruise altitude selection balances true airspeed gain (about 2 percent per 1000 ft) against fuel burn, wind, and oxygen requirements.

Mass and balance must be checked for takeoff, zero fuel, and landing conditions, since fuel burn shifts CG as fuel is consumed.