I have a PPL checkride and the first portion of the exam is a long cross-country journey of about 300 miles. I know I'm expecting a diversion in there somewhere. But in general and for checkride purposes, how many alternates should I prepare?
In my opinion, I'd think one alternate for every 30 minutes of flight. Because, if there was some issue such as losing my alternator, then I have about 30 minutes left on the battery.
Is this the right way to think about it?
If you are asking about a Private Pilot Airplane certification check ride in the U.S. you should refer to the "Private Pilot Airplane - Airman Certification Standards" (ACS), Item VI Task C., Diversion (shown below) for general guidance.
In my experience a "diversion," where the examiner would expect you to select a suitable alternate airport to divert to in flight, could happen at anytime during the check ride.
As you are aware, for the check ride the examiner will have you plan a cross-country flight (see Item I, Task D. in the ACS linked above). Unless you know ahead of time what general route the examiner will have you plan for your "cross-country planning task" it may be difficult to do comprehensive advanced "alternate" planning. Also, depending on the location where your check ride will take place there may be many potential alternates available or only a few (i.e., Southern California vs Northern Wyoming)
However, as you do your cross-country planning during the "Preflight Preparation" portion of the check you could evaluate some of the potential alternate airports along the route and perhaps gain a reasonable idea of what airports may be suitable for selecting as an alternate (diversion) airport once the examiner initiates that Task.
Keep in mind that with all of the Tasks required to complete the check ride the cross-country and diversion will likely be reasonably close to the departure airport (check rides only last so long).
But definitely, also discuss this issue with your CFI.
Maybe a little bit better way to approach this problem is not so much preselect in a series of alternates, but as part of flight planning and periodically assess during the flight where, if something happens are you going to go and what contingency plans are available to you.
Keep in mind that an alternate course of action is going to be your best course of action available to you given the circumstances. That may or may not be an airport. For instance, and examiner may opt to put you in a situation where no airport is available to you and see how you react, either in a simulated situation with the aircraft boxed in by storms or have an in-flight emergency were a power off glide to the nearest airport is simply not possible. These are some contingencies that you need to think about for alternate courses of action. Now an examiner might give you a scenario where an alternate airport is available to you, for instance a fuel urgency situation, and see if you select another airport nearby and evaluate your decision making process for selecting this, the criteria you used to evaluate this and make your decision, etc.
Please keep in mind that what your examiner wants to see is how safe a pilot you’ll be after you pass your checkride. The planning you do should therefore be a realistic representation of what that will look like.
I don’t research every airport along my route for every flight, nor do I evaluate alternates at all for VFR flights. I do try to keep my route near airports when possible in case a diversion is necessary, and they make great VFR checkpoints too (a habit I picked up before GPS), but I don’t look any deeper than that, nor did my instructors or examiner expect me to.
If something does go wrong, then you quickly decide the best place to divert based on how urgent it is to get on the ground; a fire may have a different answer than a passenger needing a restroom or unforecasted weather ahead, for instance. The examiner will want to see you use all resources available (sectional, EFB, glass panel, ATC, etc.) to make that decision live, like you would on a real flight, not checking an unrealistic canned list of diversion points.
Note that if you planned your route to fly over/near airports (see above), the answer is usually going to be pretty obvious, which is another reason to do that. Worst case, crashing at an airport (which should have fire/rescue services readily available) is probably more survivable than crashing somewhere else.
