The A320 flight management and guidance system uses different types of keyboards depending on the aircraft’s age and revision cycle. If you look closely you will see that the lower right key of the num pad is either a forward slash or a plus/minus sign. This is very confusing for a pilot who sometimes flies different aircraft on the same day.
Luckily the system validates the input and will reject wrongly formatted entries, but this still causes frustration and delayed input.
