C152 – Take-off Performance

On a hot humid day, the aircraft will require more runway to take off, you can test this in the simulator yourself, start on the runway (Offline) set the weather to 40 degrees Celsius and open the throttle. Then reset and change to 0 degrees Celsius and do the same and you will notice the difference in how the aircraft performs. Being aware of this is very important.

We need a few things to calculate the takeoff distance. These are

  • QNH
  • Airfield elevation
  • Outside temperature
  • Wind component

QNH and Airfield Elevation we need to calculate the pressure altitude.

Our QNH is 1016, elevation is 709ft

Formula is PA (ft) = ( 29.92 – AltSet.(in/hg) ) * 1000 + FieldElev.(ft)

To make this easier to explain let us assume the press altitude is 1000ft and the outside temperature is 20 degrees. We can see that we have a ground roll of 825ft and if we need to clear a 50ft obstacle we need 1530ft simple yes? if the temperature is between 15 degrees you will need to do some maths and work that out.