I have had several students turn up for their first cross country navex without a watch. It seems very common nowadays for young people to rely on their iPhones for time - not very convenient in flight. On one occasion the lack of watch was not realised until we arrived at the first checkpoint. I had to lend him mine
You don't need a stopwatch for PPL nav, but it is useful to have one available.
My current watch of choice is a Citzen Ecodrive. Black face, nice big white numbers and a built in stopwatch. Cost around £200, but worth it.
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