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Approach Categories

Asked by: 5376 views Airspace, FAA Regulations

I understand how the approach categories are computed (1.3  x Vs0)and understand the logic for the higher mins. as you move to higher categories for circling approaches but I would like more clarity for straight in approaches.

Assume straight in approach and assume a airplane is Cat. A ( using 1.3 Vso ) and I have elected to land straight in with a tailwind (although typically I would not approach or land with a tailwind) .My usual IAP speed is 85 KIAS.  The tailwind puts my ground speed at 95 knots yet my indicated is 85 knots. Based upon the categories,  95 knots ground speed puts me in category B but 85 KIAS puts me in category A.  Assume the IAP has higher mins. for Cat. B.

QUESTION: Do I use Cat. A or Cat. B mins?

Thank you for the feedback.

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2 Answers

  1. John D Collins on Jan 03, 2014

    The definition of approach categories can be found in 97.3:

    “As used in the standard instrument procedures prescribed in this part– 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”

    At VSo there is typically a significant difference between CAS and IAS, whereas at approach speeds these values are much closer together. 1.3 VSo is a calibrated airspeed that should be converted to an equivalent indicated airspeed.

    The category speeds are IAS/CAS and do not take winds into consideration. An aircraft is only in one category, but if operated at an IAS/CAS of a higher category, must use the minimums associated with the IAS/CAS of the higher category. You can read this in the Terminal Procedures Legend information.

    So to answer your question, if you use an approach speed of 85 Knots and the aircraft is a category A aircraft, then a GS of 95 knots does not change which category of approach minimums you are required to use, category A is still applicable. On the other hand if you are flying a category A aircraft and have a 10 knot headwind, but are flying the approach at an IAS of 95 Knots and therefore have an 85 Knot GS, you must use the category B approach minimums.

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  2. Dan Chitty on Jan 04, 2014

    Thank you John for the feedback.

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