Definition
The position the Flight Management System (FMS) calculates and displays when it cannot establish a fully reliable fix from its primary navigation sources. The FMS blends whatever inputs remain available — such as inertial reference, dead reckoning from the last known position, or degraded signals — to produce its best estimate of where the aircraft currently is.
Plain English
When the FMS isn't getting good enough information to know exactly where the aircraft is, it uses what it does have to make its best guess and shows that as the aircraft's position.
Context Anchor
Seen in flight management system discussions when the system is deciding where the aircraft is and using that position for route guidance, distance, and navigation displays.
Why Pilots Care
It provides the position reference used for flight plan navigation, waypoint sequencing, and approach guidance.
Grounding Statement
If the system receives more than one source of position information, it uses its rules to decide which information gives the best present-location estimate.
Intuition Check
“Best” does not mean exact or guaranteed. It means the system’s best available estimate based on the information it is receiving.
Example Sentence 1
After losing GPS signal over the ocean, the FMS continued navigating using a best computed position based on inertial inputs.
Example Sentence 2
When GPS signal was lost, the system reverted to the Best Computed Position using inertial data.