Definition
A capability of an area navigation (RNAV) system in which the equipment continuously monitors its own position solution, detects when one of the navigation inputs (such as a GPS satellite signal) has become unreliable, and excludes that bad input so the displayed position remains trustworthy. This is the core function provided by Receiver Autonomous Integrity Monitoring (RAIM) and Fault Detection and Exclusion (FDE) in GPS receivers approved for IFR use.
Plain English
The navigation system can spot when one of its information sources has gone bad and stop using it, so the pilot is not flying off a wrong position without knowing.
Context Anchor
Seen when planning an instrument departure that depends on onboard navigation equipment, especially when the departure procedure requires reliable position guidance.
Derivation
Detection comes from a Latin idea meaning “to uncover.” Isolation comes from a word related to “island,” meaning to set something apart. Together, the phrase means uncovering bad navigation information and setting it apart so it does not affect the flight path.
Why Pilots Care
Prevents use of incorrect position data that could cause deviation from the cleared departure path or loss of situational awareness.
Grounding Statement
The key idea is that the system must not only notice a navigation problem, but also identify the bad input so the aircraft does not keep following it.
Intuition Check
Isolation does not mean separating the aircraft from something outside. Here it means identifying and excluding the bad navigation source.
Example Sentence 1
Before filing the RNAV SID, the crew confirmed their GPS receiver had detection and isolation of faulty navigation information, so it would alert them if a satellite signal went bad during the departure.
Example Sentence 2
During preflight planning the pilot confirmed the system could handle detection and isolation of faulty navigation information on the planned SID.