It never ceases to amaze me how simple but very important things are overlooked when teaching simple VFR navigation be it the RAF, or civil FTOs.
Countless times I have come across the following situation when dealing with VFR navigation tests or PPL re-training;
A flight is planned from A to B and an alternate is chosen which is either further along in the direction of travel or close abeam the destination.
The pre-flight planning for the diversion is taken from overhead the destination.
I ask the pilot where they will divert to if the visibility and cloudbase at destination are below the required minima. The answer is always to the alternate to which I say......if the weather is below VMC at the destination, how can one overfly or fly past the destination to the pre-planned alternate.
When dealing with diversions due to lowering cloudbase and/or reducing visibility, such a diversion will never take place from overhead the destination because one can't get that far and if one could, one would land. The simple fact seems to be missing from most VFR navigation training these days.
OK blocked runway/ comms failure/ ATC delays and winds are different factors but many pilots expect to use the alternate in every situation.
Thus having some MDR skill is important because when the pilot is placed with the need for a diversion it will be somewhere downroute and the computer is too cumbersome to use in the air at the same time as flying the aircraft and maintaining an adequate lookout in reducing visibility!
IMHO - computer for pre-flight, MDR in-flight.
Regards,
DFC