Your approach category deals with more than just the circling approach. It determines your maximum speeds, maneuvering airspace, and obstacle clearance on approach as well as missed approach. It is always based on your maximum certificated landing weight, though that can be changed through manufacturer approved maintenance logbook action. The speed that is used might be different between ICAO and U.S. FAA, depending on aircraft.
The United States FAA used to subscribe to a dangerously narrow circling approach area that has killed and will kill again if you don't understand the problem. (See Circling Approach Area for more about this.) The case of Air China 129 is one where a Boeing 767 was trying to circle to what were TERPS standards back then and ended up losing the airplane and 129 lives. TERPS standards have since changed but many U.S. circling procedures have not.
So what's the bottom line here? You need to understand exactly what your aircraft's circling capability is, what the correct approach category is, when you can change it, and what all that gives you for any particular airport.
Everything here is from the references shown below, with a few comments in an alternate color.
[14 CFR 97.3] Aircraft approach category means a grouping of aircraft based on a speed of VREF, if specified, or if VREF is not specified, 1.3VSO at the maximum certificated weight. VSO, and the maximum certificated landing weight are those values as established for the aircraft by the certification authority of the country of registry.
These categories are as follows:
There are some who would argue that maximum certificated weight only applies to 1.3VSO based on the placement of a comma in the regulation. The debate raged on for decades but the FAA finally provided some clarity in 2013:
[ICAO Doc 8168 PANS-OPS Vol 1, §4, ¶1.4]
1.4.1 Aircraft performance has a direct effect on the airspace and visibility required for the various manoeuvres associated with the conduct of instrument approach procedures. The most significant performance factor is aircraft speed. Accordingly, categories of typical aircraft have been established.
1.4.2 The criterion taken into consideration for the classification of aeroplanes by categories is the indicated airspeed at threshold (Vst).
1.4.3 Aircraft categories will be referred to by their letter designations as follows:
These speeds are the same as used in the United States but the criteria is slightly different. If you have a VSO and a VS1G for your aircraft, you must use the higher of VSO times 1.3 or VS1G times 1.23.
Regardless of the speed used, it must be based on the aircraft's maximum certificated landing mass.
More on this below under The Variable Approach Category Mess.
While the speeds used for determining approach categories are based on maximum certificated landing weight, the maximum speed actually used for approach can be different. But must it be different?
[Aeronautical Information Manual §5-4-7] A pilot must use the minima corresponding to the category determined during certification or higher. 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 must be used. For example, an airplane which fits into Category B, but is circling to land at a speed of 145 knots, must 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 must use the approach Category C minimums. See the following category limits:
For as long as I have been flying the rule has been that if you bump into the next category's speed range, you must go into the next category. It is no longer a "must" but now it is a "should."
[Aeronautical Information Manual §5-4-7]
NOTE−VREF in the above definition refers to the speed used in establishing the approved landing distance under the airworthiness regulations constituting the type certification basis of the airplane, regardless of whether that speed for a particular airplane is 1.3 VSO, 1.23 VSR, or some higher speed required for airplane controllability. This speed, at the maximum certificated landing weight, determines the lowest applicable approach category for all approaches regardless of actual landing weight.
In the U.S., the maximum speed for determining an approach category is also the maximum speed for maneuvering. If the pressure altitude, winds, temperature, or any other factor requires you to increase your maneuvering speed, your turn radius goes up and the obstacle clearance is no longer guaranteed. You should increase your approach category.
[ICAO Doc 8168 PANS-OPS Vol 1 §4, Table I-5-1-2]
While the speed ranges used to determine an aircraft's approach category are identical to 14 CFR 97.3, ICAO Doc 8168 PANS-OPS Vol 1 §4, ¶1.3.5, the maximum permitted speed for visual maneuvering is significantly higher. Additionally, speed ranges are specified for other segments of the approach. While it is true the speeds permitted are higher, the circling approach area is larger too.
See Circling Approach Area for more about this.
The maximum glide path angle depends on vertical guidance.
If you have vertical guidance and are flying a PA or BARO NAV approach, the maximums are listed as follows:
[TERPS, ¶2-6-2, Table 2-6-1] GPAs must not exceed the values specified in table 2-6-1.
|A (80 knots or less)||6.4|
|A (81 - 90 knots)||5.7|
|D & E||3.1|
We used to say you can move your category up, but never down. Alas, that isn't really true. In the case of the T-38, we thought of ourselves as Category E unless we were light enough to be Category D. Not too long ago most Gulfstreams had Aircraft Service Changes that allowed the pilots to simply turn a placard in the cockpit to magically change from Category D to Category C. The FAA got wind of this and those days are over. Now, for us civilians, there is just one recognized method of lowering approach categories.
The FAA allows operators to legally reduce an aircraft's maximum certificated landing weight which allows them to reduce to a lower approach category. This is not something a pilot can do, it requires maintenance logbook action. In the case of the G450, for example, Gulfstream Aircraft Service Change 007 must be installed. Once that is done, the aircraft's maximum landing weight drops from 66,000 lbs to 58,500 lbs and the aircraft becomes Category C. To undo this action, the ASC must be legally removed from the aircraft by logbook action. Some would say even the paperwork instituting ASC 007 must be physically removed from the airplane.
More on this at: G450 Approach Category.
14 CFR 97, Title 14: Aeronautics and Space, Standard Instrument Procedures, Federal Aviation Administration, Department of Transportation
Aeronautical Information Manual
Gulfstream G450 Aircraft Service Change 007C, Maximum Landing Gross Weight, 58,500 pounds, Category C, Provisions, October 26, 2011
ICAO Doc 8168 - Aircraft Operations - Vol I - Flight Procedures, Procedures for Air Navigation Services, International Civil Aviation Organization, Sixth Edition, 2018
United States Standard for Terminal Instrument Procedures (TERPS), Federal Aviation Administration 8260.3B CHG 25, 03/09/2012
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