Can someone explain the question below in details?

You plan to fly a cross country flight at 2 000 feet at a true airspeed of 120 knots. Your track is 270° (True) and the wind is from 225° (True) at 24 knots. Using the Mental Dead Reckoning Clock Code, what true heading would you steer, and what would be your magnetic heading if the local magnetic variation is 4° West?

  • $\begingroup$ "Mental Dead Reckoning Clock" Not even a whizz wheel? $\endgroup$ Apr 28 '19 at 17:02
  • $\begingroup$ I'm afraid not. It's a question from the PPL theory questions book. I know how to determine the 'max drift angle' and but don't know how to include this material to find the magnetic heading. $\endgroup$
    – Canberk
    Apr 28 '19 at 17:10

Step 1: Calculate maximum drift.

Max drift $ = \frac{wind speed}{TAS (NM/min)} = \frac{24}{120/60} = \frac{24}{2} = 12$

That means if you have a direct crosswind, you'll need to correct 12$^{\circ}$.

Step 2: Determine how much of the wind is crosswind

The mental clock code is a way of estimating crosswind component from total wind. There are 60 minutes on a clock face. If the wind direction is 60$^{\circ}$ or more, it's considered all crosswind, just as 60 minutes is considered the whole clock face.

By extension, a wind angle of 30$^{\circ}$ means 30 minutes, which is half a clock, so half the wind would be considered crosswind. 15 degrees would be a quarter of a clock, therefore a quarter of the wind, and so on.

Your maximum drift is 12 degrees with a full crosswind, but you don't have a full crosswind. Instead you have a 45$^{\circ}$ angle, so 45 minutes of a clock, which is $\frac{3}{4}$.

$ 12 * \frac{3}{4} = 9$ so you'll need to apply 9 degrees of crosswind correction toward the wind. $270 - 9 = 261^{\circ}$

Step 3: Correct for variation

"East is least, West is best". If variation is west, add to true to get magnetic.

$261 + 4 = 265^{\circ}$


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.