About Your Result

All weather data comes directly from the Aviation Digital Data Service, which apps like ForeFlight use to get up to date weather data for airports. It's important to note that wind in METARs are displayed relative to true north, unlike in ATIS and AWOS readings over the radio, which are read in magnetic north. The wind direction printed on the TOLD card are in true north, however magnetic variation is considered when calculating headwind and crosswind components. Here is the simplified code that calculates crosswind and headwind components:

true_wind_direction = int(wind_direction) + magnetic_variation
wind_difference = abs(true_wind_direction - int(runway) * 10)
wind_difference = min(wind_difference, 360 - wind_difference)

crosswind_component = abs(wind_speed * math.sin(wind_difference))
headwind_component = abs(wind_speed * math.cos(wind_difference))

Pressure altitude and density altitude are calculated with this code:

pressure_altitude = field_elevation + ((29.92 − altimeter) * 1000)
density_altitude = pressure_altitude + (120 * (temperature - 15))

Calculations for takeoff and landing distances as well climb rate all follow the rules published in the pilot's operating handbook for the Cessna 172R, taking into account headwinds, temperature, density altitude, etc. Maneuvering speed (Va) is also calculated based on gross weight via this formula:

maneuvering_speed = 99 * math.sqrt(gross_takeoff_weight / 2450)

All weight and balance calculations are done exactly how we are taught in private pilot ground school using numbers published by the school. Make sure to double check that the weights for the airplanes are correct, because it might take a few weeks before I update the data to reflect any changes. If any numbers are different, I highly recommend selecting "Custom" in the aircraft dropdown. From there you can enter the correct values so you can ensure that the weight and balance calculation is accurate. Also, I would greatly appreciate it if you reported the inaccuracy here. Thank you for using the site. Make sure to tell all your friends about it.