No doubt you've covered (or about to cover) the procedure for executing a diversion in the course of your flight training. But have you internalized its purpose?
Sometimes new students concentrate so much on the procedure taught, they find themselves getting lost in minor details, to the detriment of the overall purpose of the exercise.
It is always useful to hear a perspective of an experience instructor/pilot on an exercise, and I recently had the privilege to sit on a PPL flight test debrief with a very experienced and enthusiastic examiner, who, among other things, shared his insights into this exercise with us.
The main point he tried to drive home was this: there is often a sense of urgency to a diversion situation; most diversion scenarios involve some manner of time sensitivity. If the weather is deteriorating, getting into better weather or landing soon is critical to avoid flight into IFR conditions. If your passenger is having a heart attack, every second counts! That's why one of the most important things for a diversion, once you've figured out where you are diverting to, is to get going in at least the rough general direction of your new destination as soon as possible, and figure things out on the way.
Add a Little Reasoning to Your Training
This very possibly contradicts the procedure you've been taught: you know, the one where you are to slow down (perhaps even put down some flaps) and fly a racetrack pattern around a landmark in the area planning your diversion on a straight leg. Sometimes it might be a necessary thing to do in order to positively establish where you are and avoid getting lost later in the diversion. However, this is an extra step that can add several minutes to your diversion, which in some situations could make a critical difference.
That's why, if you at all can, you should depart for you diversion as soon as possible, and figure out the rest of the planning along the way.
Transport Canada: "Undue Delay"
The PPL Flight Test Guide has in fact been amended recently to indicate that. Whereas before it was implied that a racetrack or similar pattern was acceptable for a PPL candidate, the guide now states: "The candidate is expected to initiate the diversion without undue delay. This will require extensive ground training and practice to improve the candidate’s ability to quickly determine a track to follow, an approximate heading and an approximate time enroute without the need to loiter in a holding pattern."
Remember your Mnemonics
To help flight students initiate quick and accurate diversion, I use the following acronym:
Circle-circle-line-line SHITTTEEE MAC (It's a little bit rude... but it works!)
Circle-circle-line-line refers circling the point from which you're diverting and your destination, drawing a line connecting the two of them, and then a shorter line to mark the halfway point.
Indicator - make sure that's done in straight and level flight!
Turn - figure out the heading you need to fly by putting a pencil over your track and sliding it over to the centre of a VOR rose - and then turn to that heading (adjust as necessary for drift)! You are now going towards your destination less than a minute after you've started your planning!
Time - record the time (to know when you should be at your destination)
Track - this is a very important point that often gets skipped... Look around you and make sure that your departure angle makes sense! If you're supposed to be crossing a north-south road at about a 30-degree angle but you're flying parallel through it - double-check your planning! Also, monitor drift due to crosswinds and adjust your heading to crab into the wind as necessary in order to maintain a desired track over ground.
Estimate distance - now that you've convinced yourself you're actually going in the right direction, you can complete your planning. Your instructor probably showed you how to use your pencil or your hand to measure distances on your VNC or VTA chart - use whatever method you're used to, to get the idea of how far you're going.
Estimate time - a typical light trainer flies at about 90 knots. That means covering 1.5 miles every minute. So to get the idea of how long it should take you to get to your destination, you can divide your distance estimate by 3 and then multiply by 2. Of course, adjust your estimate if you have a strong headwind or tailwind, or if your plane flies faster or slower than 90 knots.
Estimate fuel - hopefully you know how much fuel your plane burns per hour (you certainly should have looked it up during your cross-country planning!) So just double-check to make sure you have enough (use your E6B if necessary). For this you also need to know how much fuel there is in your tanks (e.g., if you need 10 gallons of fuel to get to your new destination, and the fuel gauges are at half, do you have enough?)
Now that you're done with the planning, time to figure out the enroute stuff:
Mixture - lean as appropriate
ATC - contact as appropriate (and generally communicate with other ground stations and traffic). This could mean a call to the FIC to amend your flight plan, a call to the tower a few miles out if you're diverting to a controlled airport, or talking to other pilots in the area to keep them updated of your position and intentions.
Carb heat/checkpoints checks - if your plane has a carbureted engine, conduct carb heat checks every 15 minutes. Watch for checkpoints/landmarks that should be showing up on your route. Note time at midpoint and adjust ETA as necessary.