Three Key Things
Don't complete an instrument approach without them
When executing an instrument approach to an airport in poor weather conditions, certain altitude restrictions are placed on the execution of that approach. One of those restrictions relates to the decision height (DH) or minimum descent altitude (MDA). Sometimes, when pilots reach that altitude during the approach, the weather seems to be clearing, and there is a reluctance to execute a missed approach if a landing can otherwise be safely accomplished. Federal Aviation Regulation 91.175(c) sets out the requirement that no pilot may operate an aircraft at any airport below the authorized MDA-or continue an approach below the authorized DH-unless all three of the following conditions are met:
- The aircraft is continuously in a position from which a descent to a landing on the intended runway can be made at a normal rate of descent using normal maneuvers.
- The flight visibility is not less than the visibility prescribed in the standard instrument approach procedure being used.
- At least one of the visual references set out in the regulation for the intended runway is distinctly visible and identifiable to the pilot.
Once the airplane reaches the missed approach point (MAP), the pilot cannot descend any farther unless the flight visibility is above minimums and one of the following references is visible and identifiable to the pilot:
- The approach light system, except that the pilot 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 touchdown zone lights.
- The runway or runway markings.
- The runway lights.
The regulation is intended to allow a pilot to execute a safe approach to a landing in poor weather conditions. It is not permission to proceed with an approach when the conditions are unsafe. The regulation is specifically written to prevent the pilot from reaching the MDA or DH and staying there in hopes of catching a glimpse of the runway references.
For example, the pilot is not permitted to stay at the MDA or DH until the runway can be seen passing below the aircraft, at which time the pilot pulls the power and drops the aircraft. The pilot cannot see and identify a runway reference, then lose it, and still continue the approach.
Also, even though flight visibility-not reported visibility-is the controlling factor, the pilot's word on this could be disputed. The FAA could take action against the pilot using the reported weather conditions, as well as other relevant information, as evidence that the flight visibility could not have been above what was required. The issue becomes one of credibility in such actions, though it would seem that the pilot's assessment from the cockpit would be the most probative.
This regulation allows pilots to safely take a look and safely complete an instrument approach to a landing when the weather is actually better than reported. It is an advantageous regulation but should not be taken for granted. It is important for pilots to honestly estimate the flight visibility, to truly see and identify at least one runway reference, and to maintain the aircraft in a stable approach for landing, in order to stay in compliance and stay safe. Otherwise, divert to another airport to land.
Kathy Yodice is an attorney with Yodice Associates in Washington, D.C., which provides legal counsel to AOPA and administers AOPA's legal services plan. She is an instrument-rated private pilot.