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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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Estimating Flight Visibility

How do you determine flight visibility when coming out of the clouds on an approach? If the approach has a lighting system, there are a number of clues in the system itself.

  • Decision bar. Every approach lighting system has a "decision bar" located 1,000 feet from the runway threshold. These lights (or bar) are perpendicular to the approach lighting system.
  • "Rabbit." There is another 1,000 foot clue in the sequenced flashing lights, known to pilots as the "rabbit." The sequenced flashing lights stop at the decision bar.

If you are at the middle marker (MM) and you cannot see the runway threshold, look for the decision bar. Assume that you spot the decision bar. If you know that the MM is six tenths of a nautical mile (0.6) from the threshold, then you have 3,650 feet from the runway. Subtract the 1,000 feet from the threshold, which you cannot see, to the decision bar, which you have spotted, and that leave 2,650 feet -- just under 1/2 mile. If the minimum visibility for this approach is 1/2 mile, then you have the required visibility.

Other Information Sources

  • CFIT Advisory Circular (http://www.airweb.faa.gov/Regulatory_and. . .9FE4D96586256D04006F2065?OpenDocument)

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