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FAR 91.3 says:

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. VREF, Vso, and the maximum certificated landing weight are those values as established for the aircraft by the certification authority of the country of registry. The categories are as follows—

(1) Category A: Speed less than 91 knots.

(2) Category B: Speed 91 knots or more but less than 121 knots.

(3) Category C: Speed 121 knots or more but less than 141 knots.

(4) Category D: Speed 141 knots or more but less than 166 knots.

(5) Category E: Speed 166 knots or more.

So an aircraft category never changes because it is always Vref at max landing weight.

What if I fly an approach at a speed that falls into a different category? For instance, a jet may land at significantly less than this speed if very light, or more than this speed if landing with less than full flaps due to a failure (or any other operational reason). Which minimums do you use then?

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New answer due to updated FAA guidance:

TLDR
The short version is that a pilot is only required to use the approach category for the aircraft's maximum certified landing weight and to stay within the protected area while circling.

However, it is recommended that if a speed higher than the maximum for that category must be used that the pilot either should use 1) the corresponding minimums for the higher category, or 2) an alternative method (i.e. company or pilot provided).

EXPANDED ANSWER
AIM 5-4-7(a) states that an aircraft must stay within the circling approach protected area during the approach.

It then says in AIM 5-4-7(b) that "one acceptable method" is to use the approach category corresponding with the speed that will be flown (certified approach category or higher).

It continues in AIM 5-4-7(c) with considerations for a pilot who chooses an "alternative method" to remain within the protected area. One example that they provide is that this may be done where higher category minimums are not published.

There is a very nice writeup on this that the NBAA released at the beginning of 2020.

From a safety perspective, the most commonly used method is that stated in 5-4-7(b), which used to be what the AIM said must be done prior to this change.

I can see where an alternative method may be useful (such as a side-step which doesn't actually require you to maneuver out of the protected area), however keep in mind that you must remain inside the protected area at all times, including during the missed approach (even if you don't expect to go missed). In some cases, the only reason for having higher minimums (or even NA) is due to the missed approach procedure obstacle clearance.

FULL TEXT OF SUMMARIZED PARTS:

AIM 5-4-7. Instrument Approach Procedures

a. Aircraft approach category means a grouping of aircraft based on a speed of VREF at the maximum certified landing weight, if specified, or if VREF is not specified, 1.3VSO at the maximum certified landing weight. VREF, VSO, and the maximum certified landing weight are those values as established for the aircraft by the certification authority of the country of registry. A pilot must maneuver the aircraft within the circling approach protected area (see FIG 5-4-29) to achieve the obstacle and terrain clearances provided by procedure design criteria.

b. In addition to pilot techniques for maneuvering, one acceptable method to reduce the risk of flying out of the circling approach protected area is to use either the minima corresponding to the category determined during certification or minima associated with a higher category. Helicopters may use Category A minima. If it is necessary to operate at a speed in excess of the upper limit of the speed range for an aircraft's category, the minimums for the higher category should be used. This may occur with certain aircraft types operating in heavy/gusty wind, icing, or non-normal conditions. For example, an airplane which fits into Category B, but is circling to land at a speed of 145 knots, should use the approach Category D minimums. As an additional example, a Category A airplane (or helicopter) which is operating at 130 knots on a straight-in approach should use the approach Category C minimums.

c. A pilot who chooses an alternative method when it is necessary to maneuver at a speed that exceeds the category speed limit (for example, where higher category minimums are not published) should consider the following factors that can significantly affect the actual ground track flown:

  1. Bank angle. For example, at 165 knots groundspeed, the radius of turn increases from 4,194 feet using 30 degrees of bank to 6,654 feet when using 20 degrees of bank. When using a shallower bank angle, it may be necessary to modify the flightpath or indicated airspeed to remain within the circling approach protected area. Pilots should be aware that excessive bank angle can lead to a loss of aircraft control.
  2. Indicated airspeed. Procedure design criteria typically utilize the highest speed for a particular category. If a pilot chooses to operate at a higher speed, other factors should be modified to ensure that the aircraft remains within the circling approach protected area.
  3. Wind speed and direction. For example, it is not uncommon to maneuver the aircraft to a downwind leg where the groundspeed will be considerably higher than the indicated airspeed. Pilots must carefully plan the initiation of all turns to ensure that the aircraft remains within the circling approach protected area.
  4. Pilot technique. Pilots frequently have many options with regard to flightpath when conducting circling approaches. Sound planning and judgment are vital to proper execution. The lateral and vertical path to be flown should be carefully considered using current weather and terrain information to ensure that the aircraft remains within the circling approach protected area.
    ...

OLD Answer:

According to the FAA Safety Alert for Operators issued on 09/20/2012 (SAFO 12005):

  • A pilot may never use the approach minimums specified for an approach category lower than their certified approach category, even if the actual approach is flown at a speed that would be in the lower approach category.
  • A pilot must always use the approach minimums specified for an approach category higher than their certified approach category if the actual approach will be flown at a speed that would be in the higher approach category.

Note that this is different in other areas of the world (Canada for example uses the actual approach speed of the aircraft to determine the approach category).


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  • $\begingroup$ So when you have an ILS with a GS steeper than usual, and Cat D mins are NA... And you're in your certified-as-Cat-C aircraft, but due to being fairly heavy & less than full flaps and adding speed for gusts, you're into Cat D speeds. No circling involved -- straight-in ILS. Are you legal to fly those speeds on that approach? $\endgroup$
    – Ralph J
    Sep 10 at 22:06
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    $\begingroup$ @ralph According to the new guidance, yes, as long as you remain within the protected airspace at all times (including if you have to go missed). They still recommend an alternate procedure to ensure this (Note that paragraph B in the AIM text includes an example very similar to this). That being said, unless you have an ironclad plan which you can execute to guarantee that you won't overshoot a turn, I don't think that this is very smart.... $\endgroup$
    – Lnafziger
    Sep 11 at 13:49

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