Aviatorhi,
I'm not sure I understood what you meant but in both TERPS and PANS-OPS the Aircraft Approach Category is determined
only with reference to speeds and not to size. The size of the aircraft is only being taken into account by PANS-OPS to determine the OCA for Precision Approaches - thus determining the DA. Not the Aircraft's Approach Category. Check out the following quotes:
1. TERPS: (taken from FAA FAR 97.3):
Aircraft approach category means a grouping of aircraft based on a speed of VREF, if specified, or if VREF is not specified, 1.3 Vso at the maximum certificated landing weight.
2. PANS-OPS: (taken from ICAO doc. 8168 which can be found in Jeppesen Airway Manual p. 525):
1.3 CATEGORIES OF AIRCRAFT
1.3.1 Aircraft performance has a direct effect on the airspace and visibility required for the various manoeu- vres associated with the conduct of instrument approach procedures. The most significant performance factor is aircraft speed.
1.3.2 These categories provides a standardized basis for relating aircraft manoeuvrability to specific instru- ment approach procedures. For precision approach procedures, the dimensions of the aircraft are also a factor for the calculation of the obstacle clearance height (OCH). For Category DL aircraft, an additional obstacle clear- ance altitude/height (OCA/H) is provided, when necessary, to take into account the specific dimensions of these aircraft.
1.3.3 The criterion taken into consideration for the classification of aeroplanes by categories is the indicated airspeed at threshold (Vat ), which is equal to the stall speed Vso multiplied by 1.3, or stall speed Vslg multiplied by 1.23 in the landing configuration at the maximum certificated landing mass. If both Vso and Vslg are available, the higher resulting Vat shall be applied.