Definition
Differences between the navigation information stored in an aircraft's onboard navigation database and the information published on current charts, instrument procedures, or NOTAMs. These differences may involve waypoint names, fix coordinates, altitudes, course values, procedure sequencing, or the presence or absence of specific procedures.
Plain English
When what your aircraft's navigation system shows for a route or procedure does not match what is printed on the official chart or notice. The two sources disagree, and the pilot has to recognize it and resolve it before flying the procedure.
Context Anchor
Encountered during preflight planning, when loading an instrument procedure into the aircraft’s navigation system, or when comparing the loaded procedure against the current chart.
Derivation
Discrepancy comes from a Latin root meaning to sound differently or fail to agree. That helps here because a database discrepancy is exactly a failure of two sources of flight information to agree.
Why Pilots Care
Unresolved discrepancies can cause the aircraft to follow incorrect routes, altitudes, or procedures, compromising safety and regulatory compliance.
Analogy
It is like using a phone map that has not been updated after a road change. The map may still look official, but it may not match the route that actually applies today.
Grounding Statement
If the chart shows one route point or altitude and the aircraft’s navigation system shows another, that mismatch is a database discrepancy.
Intuition Check
Do not assume database discrepancies are always small paperwork errors. In aircraft navigation, a mismatch in stored data can affect the path the airplane is guided to fly.
Example Sentence 1
While briefing the RNAV approach, the crew noticed a database discrepancy: the final approach fix altitude in the FMS was 200 feet lower than the altitude printed on the chart.
Example Sentence 2
After a procedure amendment, database discrepancies may exist until the next update cycle is loaded.