A real world example of how to determine which minimums are applicable to your aircraft for an IAP according to FAA guidance:
Lear 60 max ldg wt Vref = 139 KIAS. Airplane is an approach category C aircraft. Aircraft only fit into ONE approach speed category according to the MLW Vref or 1.3 Vso. The LR60 is a Cat C aircraft. Cat C landing minima are the lowest which may be used. However if the approach speed to be flown is greater than 140 KIAS then cat C minima is no longer applicable. The minima which are applicable to the ACTUAL approach speed to be flown during the approach MUST be used.
A typical situation encountered on a routine basis might go like this:
A single runway airport has a GPS-A as it's only published IAP. No straight-in mins are published and circling will be required. Calculated Vref at arrival weight will be 136 KIAS. For circling the 60 a speed of Vref + 12 (Vac) is indicated so Vapp will be 148 KIAS. Therefore the Cat D minima are the lowest which may be used even though the LR60 is certified as a Cat C aircraft. Clear as mud now? Anyway that's how we have to do it in FAA land unless we were flying in the airspace of another country with more restrictive rules. We are obligated to respect whichever is more restrictive.
Best,
westhawk