Hi everyone,

So I’m currently studying to resit the performance exam (69% on first attempt...) and have started to get paranoid over a particular problem.

When calculating GSto and GShome for ETP and PNR questions that aren’t a direct head or tailwind, should your heading be adjusted on the flight computer to combat the effects of a crosswind which would result in a new value for headwind or tailwind, or should the wind strength just be read directly from the flight computer and the real life issue of overcoming a crosswind be ignored?


Thanks,

Ben.

The most efficient way to get the ground speeds is to check the table in ERSA GEN - CON - 6, CONVERSIONS - WIND COMPONENT. Simply check the angle between the wind direction and the flight planned track and extract the headwind component (Remember that forecast wind is always °T while flight planned tracks are usually given as °M). If you apply that component to your TAS, (+ for a tailwind and - for a headwind) you will get perfectly acceptable ground speeds for the calculation. The feed-back I've had from students is the exam questions usually have a simple whole number of degrees difference, such as 30° or 40°. That makes it easy to use the table.