Navigation – Intro to MDR

Adrian Willis
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In addition to aerobatic training, we teach other flying skills including Navigation. We even deliver PPL training aiming for the quality end of the market rather than a quick skim through to gain a “boy scout badge” only to lack sufficient confidence to enjoy flying later.

As I have a background in navigation, it seems natural to endeavour to develop navigation skills in our students so that they can fly with a greater degree of professionalism and gain more enjoyment rather than being slaves to GPS. When I chat to other flying schools about the merits of mental dead reckoning (MDR), they always “Poo Poo” me and say its far too complicated and students even struggle with standard closing angle. Well I believe this is a problem with the instructors rather than the student. Having said that, I will introduce mental dead reckoning and using the 1 in 60 rule very gently so that I don’t cause you to join the band of heathens who believe MDR is too difficult. If it is too gentle, don’t worry, this is only the first of many very short bloggs that together will deliver the full package!

Using MDR to estimate cross wind component prior to take off or landing

This is desirable so that you know if the wind is inside your and your aircrafts limits.
We will presume a runway heading of 270 and you are given a wind vector of 300/10. So the wind is 30 degrees off the runway heading. Using the clock code, where 60 = 1 and 30 therefore = a half, we estimate the cross wind to be 5 knots. If we now use a calculator to calculate the answer sin(30)=.5, so our rough MDR answer is exactly correct.
If we are given a wind vector of 230/10 using MDR where 60 = 1 we get a crosswind component of 10. Using a calculator sin(60)= .866 which rounded up gives us a 9 knot crosswind. The 1 knot error is acceptable!
If we have a wind of 315/10 using MDR we see a 45 degree wind and 45 minutes on the clock is 3/4 of an hour so we use 3/4 of 10 =7.5knots rounded down is 7 knots. Using a calculator sin(45)=.707 which is pretty close.
Remember that we are using the wind direction relative to runway heading.

Using MDR to calculate the headwind component prior to take off or landing

This uses and identical technique to the above, except that the angle is taken from the beam. So using a runway heading of 270, if you are given a wind of 300/10, that is 60 degrees off the beam, 60 minutes is one in our clock code system, so we use all of the wind so estimate a 10 knots headwind component against a calculated component of  .866 rounded up to 9. If we are given 315/10 the wind is 45 degrees of the beam so we use 3/4 of it, 7 knots

Of course to use this technique properly, you need to practice it.  I suggest whenever you are given a wind prior to take off or landing, you calculate the cross wind and headwind component in your head.  After a few trips it will become second nature. Remember the drunken dart player is not really a genius mathematician, he has simply played darts a lot!

Of course if you would like to attend one of our advanced navigation course, please get in contact.  Further details will eventually be added to our website.

Adrian.Willis@BritishAerobaticAcademy.com

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