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Aviation Learning Center Document Descent to MDA or DH and Beyond - P-8740-09
Author: Federal Aviation Administration Date: 1996
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When to Descend
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What Do you Need?

When you are on an instrument approach, the regulations (14 CFR 91.175(c)(3)) state that you may descend below MDA or DH only if:

  • The aircraft is continuously in a position allowing for normal rate of descent to a landing on the intended runway;

  • The flight visibility is at or above the visibility required to complete the approach; and

  • At least one of the following visual references for the intended runway is distinctly visible and identifiable to the pilot:

  • The approach light system, except that you may not descend below 100 feet above the touchdown zone elevation using the approach lights as a reference unless the red terminating bars or the red side row bars are also distinctly visible and identifiable
  • The threshold.
  • The threshold markings;
  • The threshold lights;
  • The runway end identifier lights;
  • The visual approach slope indicator;
  • The touchdown zone or touchdown zone markings;
  • The runway or runway markings;
  • The runway lights.

VASI or PAPI

When you have visual contact with the runway, fly the Visual Approach Slope Indicator (VASI), if it is available. If you have the aircraft established with a crosswind correction, do not immediately point the nose of the aircraft at the runway when you break out (a natural tendency). Trust your wind correction angle, which will keep you tracking toward the center line until the point you would normally straighten and lower the wind for a normal crosswind landing.

VDP

The Visual Descent Point (VDP) is a defined point on a straight-in, non-precision approach from which you can descend below the MDA, as long as you have the required visual reference. If a VDP is available, it will be indicated by a "v" on the profile view portion of the instrument approach procedure chart. Do not descend below MDA before reaching the VDP.

Stay on the Procedure

The CDI will be more sensitive as you fly closer to the VOR or as you fly inbound on a localizer course, so make your corrections smaller as you get closer. Once you spot the runway, or one of the required visual references, it may be tempting to give up on the procedure. Don't! Unless you are VFR conditions and you have canceled your IFR flight plan with ATC, do not deviate from the published approach procedure. With respect to canceling the IFR flight plan, please do cancel whenever you are in a position to proceed to the airport under VFR conditions. If there is another aircraft awaiting a departure release, especially at a non-towered airport, your IFR cancellation will permit ATC to release the other aircraft.

Circling Approaches

So far, this discussion has focused primarily on straight-in approaches. What are the rules and good practices for safe circle-to-land approaches?

A quick review: a circling maneuver is initiated by the pilot, with ATC approval, to position the aircraft for landing on a runway when a straight-in landing from an instrument approach cannot be done. You must have visual contact with the airport before attempting a circle-to-land maneuver, and you must maintain visual contact with the airport at all times while circling to land.

In a two-pilot operation, the flying pilot should brief the non-flying pilot, before circling, on the direction to be flown after gaining visual contact with the airport. The briefing should also include the missed approach procedure and other pertinent details (see approach brief format in previous chapter). when flying the maneuver, the pilot should limit the bank to 30 degrees, and should remain at or above the MDA while circling. You will be circling well below pattern altitude, so be very careful. Also, remember that you cannot descend from MDA until you are in a position to descend to the runway using normal maneuvers and a normal descent rate.)

After doing the straight-in portion of the approach, you may find it helpful to turn 30 degrees to the runway, if you are landing on the opposite end, and then fly a parallel downwind until in proper position for a base turn. You must execute a missed approach if you lose visual contact with the airport at any point during the maneuver. The recommended practice is to make a climbing turn toward the landing runway until you are safely established on the missed approach course. Unless you have alternate instructions from ATC, fly the missed approach procedure for the approach that you used to get to the circle-to-land point.

A few additional reminders on circle-to-land:

  • Protected airspace for circling approaches is determined by the aircraft's approach category (see tables below.)

used for alignment Maneuvering Table used for alignment
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used for alignment Approach Category   A   B   C   D   E used for alignment
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used for alignment Speed (Knots)  0-90  91-120  121-140  141-165  Above 165 used for alignment
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used for alignment Circling Approach Area Radii used for alignment
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used for alignment Approach Category  Radius (Miles) used for alignment
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used for alignment A  1.3 used for alignment
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used for alignment B  1.5 used for alignment
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used for alignment C  1.7 used for alignment
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used for alignment D  2.3 used for alignment
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used for alignment E  4.5 used for alignment
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  • Plan your approach to arrive at the MDA prior to reaching the missed approach point.

  • Always) know your position relative to the initial/final approach fix when you are being vectored. Sometimes ATC might get busy and give you a late turn, which could require a steeper bank than you would like. Since you are pilot in command, ask for vectors to another approach if things don't feel right. If you cannot do what ATC asks you to do, say so.

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