Definition
In Required Navigation Performance (RNP), containment is the statistical assurance that the aircraft will remain within a defined lateral distance of the intended flight path for a specified percentage of total flight time, typically 95%. The containment value is expressed in nautical miles and matches the RNP value for the procedure (e.g., RNP 0.3 means the aircraft must stay within 0.3 NM of the centerline 95% of the time, with an additional layer of integrity monitoring out to twice that distance).
Plain English
A guarantee, backed by the navigation system's accuracy and monitoring, that the aircraft will stay inside a narrow corridor around the planned route almost all of the time.
Context Anchor
Seen in RNP procedure design and discussions of how much protected space exists around the route or approach path.
Derivation
From Latin 'continere' meaning 'to hold together' or 'keep within bounds.' In RNP, the system is literally holding the aircraft within bounds — a defined corridor of airspace.
Why Pilots Care
It ensures safe separation from terrain and other aircraft during RNP operations.
Analogy
Think of containment like the lane markings on a road, with extra protected space built around the lane. The procedure assumes the airplane will stay inside that protected space, not wander outside it.
Intuition Check
Containment does not mean physically trapping the airplane. Here it means keeping the aircraft’s actual path within a defined protected area around the intended path.
Example Sentence 1
For this RNP 0.3 approach, the aircraft's navigation system must meet the containment requirement before the procedure can be flown.
Example Sentence 2
Before flying the RNP approach the crew confirmed their equipment met the required containment limits.