When should I slow to approach speed?

Question

When do I have to slow to approach speed in order to qualify for a particular category? Specifically, if I want/need cat A minima, what is the exact point at which I need to be at 90 kt (or less)?

I’d assumed it was the FAF, because I can’t see how anything before that should affect your minima. My usual CFII says it’s the IAF, and another CFII says 3 miles before the FAF, but neither could cite a rule to support their position; it was just what their CFII had taught them.

(For the sake of argument, assume no legs are marked with explicit category restrictions, as I’ve seen on some teardrop procedures.)

Answer 1

A look through the U.S. Terps document (N8260.3E) states this:

• The minimum PT distance is 10 NM when CAT B, C, or D minimums are authorized. Decrease this distance to 5 NM where only CAT A aircraft or helicopters are to be operating, and increase to 15 NM to accommodate operational requirements, or as specified in paragraph 2-4-5.d. No extension of the PT is permitted without a PFAF. When a PT is authorized for use by approach CAT E aircraft, use a 15-NM PT distance. (page 2-23) (section 2-4-5)

• 2-1-7. Approach Categories. Aircraft performance differences have an effect on the airspace and visibility needed to perform certain maneuvers. Because of these differences, aircraft manufacturer/operational directives assign an alphabetical category to each aircraft (see 14 CFR Part 97). The categories used and referenced throughout this order are CAT A, B, C, D, and E. The authorized CAT must be used to determine OEAs [obstacle evaluation area] for circling and missed approaches and used to establish landing minimums. (page 2-5) (section 2-1-7)

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My opinion is simply this: If there is a required procedure turn, hold-in-lieu-procedure-turn (HILPT) or DME arc, these are all based on the category aircraft approved for the approach. I would fly these segments at a speed lower than the maximum authorized category on the approach.

Once I cross the PFAF or FAF, I will fly a speed that does not exceed the category I am using for that approach. For a stabilized approach, I will be at my VREF speed by 1000' AGL in IMC or 500' AGL in VMC and that will ensure I am in the category I need for the landing mins, circle and missed approach.

I found nothing in the TERPS that requires you to fly at VREF at the PFAF or FAF. You could cross at 200 KIAS if you wanted to or told to by ATC. You could slow down to VREF by minimums and be in the correct category... I suppose. I mentioned a stabilized approach for a reason, a great landing is preceded by a great stabilized approach. Am I willing to risk becoming unstabilized to fly faster and slow down by the (M)DA? I am not personally willing to do that... so I go with my previous statement. 1000' AGL in IMC or 500' AGL in VMC.

Answer 2

I don't have an FAR reference to support this, but logically, you should be at category A approach speed before you descend below category B minimums.

But something else occurs to me. The concept of having lower minimums when approaching at lower speeds is flawed in this respect. It is based on the need to maneuver to avoid obstacles, perform circling approaches, procedures turns, etc. and assumes that maneuverability (primarily tun radius), is better the slower you fly. But, for any given aircraft in a given configuration, this is actually backwards. In actuality, The closer you get to stall speed, the less maneuverable you are - (See this question).

So, unless you artificially limit yourself to 10 or 15 degrees of bank, your actual maneuverability, and the category you should use should probably be determined more by your aircraft`s stall speed (or 1.3 x stall, to be fair), than by the actual speed you are flying.

Answer 3

I know it's tagged faa-regulations, but ICAO's guidance could prove useful in finding the FAA's equivalent table shown below:

1.4.2 The criterion taken into consideration for the classification of aeroplanes by categories is the indicated airspeed at threshold (V_at). [...]

5.2.2 FAF location This segment begins at a facility or fix, called the FAF [Final Approach Fix] and ends at the MAPt. The FAF is sited on the final approach track at a distance that permits selection of final approach configuration, deceleration to final approach speed, and descent from intermediate approach altitude/height to the appropriate MDA/H either for a straight-in approach or for a visual circling manoeuvre.

— Doc 8168, Procedures for Air Navigation Services — Aircraft Operations Volume I — Flight Procedures

Answer 4

In the airline world, even with the weather at mins, it's common to be assigned "170 to the marker". That would make us all Cat E, and plenty of approaches don't have Cat E mins published. A few only have Cat C and not Cat D. So unless there is some waiver, your speed at the marker is NOT what matters.

A good CFI should know better than quoting "what I was told" as if it had regulatory weight per se!

Your AFM or OpSpecs or POH should tell you when you have to be at V-Target; the approach categories deal with what that speed is, not when it happens, AFAIK.

Answer 5

There are two reasons to slow to the approach speed for the category of aircraft you are flying. Visibility on straight-in approaches and the protected area on a circling approach. The AIM 5-4-7 Instrument Approach Procedures directly addresses when you should be at the approach speed for your category of aircraft for a circling approach. Basically, you want to be sure that you don’t fly outside of the protected area when maneuvering for a circling approach.

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.

For straight-in approaches the logic is the same, but it is not spelled out in the AIM. The faster the airplane is flying the less time the pilot has to avoid obstacles and see the runway. If there is a difference in visibility by category for descent below the altitude of the FAF it means that the aircraft will not be able to see the runway at the MAP and make a normal approach to landing. I would say that neither CFII is right and the speed has to be maintained at and after the FAF.