Day 15

More NAV today, this time 'diversions'.

Yesterday's exercise was planned beforehand on a nice big desk, with a calculator, plotters, the map spread open and plenty of time to work out the calculations. Of course there was also the opportunity to make doubly sure that the lines drawn on the map were accurate, straight and correctly measured.

However, as you may have guessed, a diversion is by definition something other than a pre-planned route. What happens is that you are flying from A to B (in my case today from Wellington to Frome) with about 3 minutes to run when the instructor says "when you get to Frome, we will be diverting to Puddletown. Please continue to Frome and then set your new course, and when convenient please provide me with details of your planned heading, altitude and ETA for Puddletown"

Aargh! First thing, continue to fly the aircraft. Second get out the map and pen and plotter (how many hands have I got?), draw a line from Frome to Puddletown. Fly the aircraft. Keep a lookout. 2 mins 30 to Frome.

Then measure the track (in degrees from true north) of the line, and the distance in nm. Fly the aircraft. Keep a lookout. 2 mins left to Frome.

Then calculate (or guestimate) the wind component and magnetic variation, and add or subtract these from the track to come up with a planned heading. Fly the aircraft. Keep a lookout. 1 min 30 to Frome.

Use the wind component to estimate the groundspeed, and use that to calculate the enroute time for the diversion. Fly the aircraft. Keep a lookout. 1 minute to Frome.

Now we need to look for Frome, making sure we pass overhead already set up on our new heading. A quick glance at the map again to see whether once we have turned there are any hazards or obstacles to deal with, such as controlled airspace, airfields, danger areas etc...

...and guess what? We are at Frome, so we turn onto our new heading, reset the timer and make a radio call. We'd better hope that all those calculations were correct, because now we are relying on them to get us to Puddletown. Time now to do a systems check, all the time flying the aircraft and keeping a good lookout! Half way to Puddletown (in about 4 minutes) we'll try to estimate position and decide if we need to make any adjustments. For now, its time to relax, take a breather, all the time flying the aircraft and keeping a good lookout!