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Difference between revisions of "Flight Level or Altitude Confusion"
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== Further Reading ==
== Further Reading ==
*[http://www..aero/bookshelf/books/138.pdf Level Bust Briefing Note Gen 1 - Level Busts: Overview];
*[http://www..aero/bookshelf/books/139.pdf Level Bust Briefing Note Gen 2 - Pilot-Controller Communications];
*[http://www..aero/bookshelf/books/134.pdf Level Bust Briefing Note ATM1 - Understanding the Causes of Level Busts].
Revision as of 13:23, 29 October 2008
Flight level or altitude confusion occurs when a pilot is cleared to fly at a particular level and correctly acknowledges this clearance, yet levels at a different flight level or altitude.
Flight level or altitude confusion is usually the result of the combination of two or more of the following factors:
- Read-back/hear-back error because of similar sounding phrases;
- Mindset tending to focus on two digits, e.g. “one zero” and thus to understand more easily "FLIGHT LEVEL ONE ZERO ZERO" when the clearance was to FL 110;
- Failing to question the unusual (e.g. bias of expectation on a familiar standard terminal arrival (STAR); and/or,
- Subconsciously interpreting a request to slow down to 250 kt as a clearance to descend to FL 100.
A common example of this is confusion between FL 100 and FL 110 (i.e. the pilot is cleared to fly at FL 110 but levels at FL 100, or vice-versa).
ICAO standard phraseology is "FLIGHT LEVEL ONE ZERO ZERO" and "FLIGHT LEVEL ONE ONE ZERO";
Alternative non-standard phraseology used with success by a number of European air navigation service providers (ANSPs) is "FLIGHT LEVEL ONE HUNDRED", and some states have extended this phraseology to include "FLIGHT LEVEL TWO HUNDRED" and "FLIGHT LEVEL THREE HUNDRED".
Similar confusion can occur at other flight levels or between altitudes, although it is much less common and FL100/110 confusion is both the most common and the most hazardous flight level confusion seen in Europe and North America.
Sound Standard Operating Procedures (SOPs), especially with regard to:
- Adherence to the pilot-controller confirmation/correction process (communication loop); and,
- Cross-checking between flight crew to ensure that the selected altitude is the cleared altitude.