Altimeters on Approach

Reader David Novelli asked an innocent but probing question. His primary airport has an approach that says if the local altimeter setting is unavailable you should use one from a nearby field and adjust the minimums. Weve all seen that, although few of us have actually had to take advantage of it.

IFR Staff

Saturday, November 11, 2017 at 12:00 AM ET

Verified

Key Takeaways:

Instrument approaches in the U.S. legally require a certified altimeter setting; if no authorized local or nearby setting is available, the approach is unusable.
Altimeter settings must come from certified sources (e.g., AWOS/ASOS or a certified observer with certified equipment).
While generally an approach is unusable without a certified altimeter, in extreme Part 91 emergencies, a pilot might intellectually consider cautiously estimating a setting if weather is comfortably above minimums, but this is not standard procedure.

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Reader David Novelli asked an innocent but probing question. His primary airport has an approach that says if the local altimeter setting is unavailable you should use one from a nearby field and adjust the minimums. We’ve all seen that, although few of us have actually had to take advantage of it.

Philosophically digging deeper, Novelli’s question was what to do when both the primary and the secondary airport aren’t reporting an altimeter. This yielded some interesting discussions of both the legal and the practical that are just the stuff we’re known for.