Definition
Onboard devices or receivers that detect navigation signals or measure aircraft state, and feed that information to the flight management system or navigation computer to determine position, track, and guidance. In the navigation database context, sensors include GPS receivers, VOR receivers, DME receivers, ILS receivers, and inertial reference units (IRUs).
Plain English
The pieces of equipment on the aircraft that pick up navigation signals or measure how the aircraft is moving, then pass that data to the flight computer so it knows where the aircraft is and where it is going.
Context Anchor
In this chapter, the term appears in discussions of airborne navigation databases and the aircraft equipment that supplies or uses navigation information.
Derivation
From the Latin sentire, meaning 'to feel' or 'to perceive.' A sensor is something that perceives — in aviation, it perceives signals or motion and reports what it finds.
Why Pilots Care
The accuracy of any FMS-flown procedure depends on which sensors are available and working. If a sensor fails or is deselected, the system may revert to a less accurate position source, which can affect whether a procedure can legally or safely be flown.
Analogy
A sensor is like a thermometer in a house: it does not heat or cool the room, but it measures the temperature and sends that information to the system that acts on it.
Intuition Check
Do not think of sensors as only small warning devices or cameras. In aircraft use, a sensor is any device or input that measures or receives information for another system to use.
Example Sentence 1
Before commencing the RNAV approach, the crew confirmed that all required navigation sensors were available and that the FMS had a valid position.
Example Sentence 2
If one of the sensors loses signal, the system may alert the pilot that database guidance is no longer reliable.