Definition
The portion of altitude-keeping error attributable to the aircraft's altimetry system itself — including the static source, air data computer, and altitude display — as distinct from errors caused by the pilot or autopilot failing to hold the assigned altitude. In RVSM operations, avionics error must remain within tightly specified limits so the aircraft can be safely separated from traffic 1,000 feet above or below.
Plain English
It's the amount of altitude error caused by the aircraft's own altitude-measuring equipment, rather than by how the pilot or autopilot is flying. In RVSM airspace, this equipment error has to be very small.
Context Anchor
Seen in RVSM discussions, where accurate altitude keeping is required for aircraft flying with reduced vertical spacing.
Derivation
Avionics' combines 'aviation' and 'electronics' — the electronic systems on board the aircraft. 'Avionics error' therefore points specifically at the equipment side of altitude-keeping, separating it from human or autopilot errors.
Why Pilots Care
In RVSM airspace even small avionics errors can cause loss of required vertical separation and trigger airspace violations.
Intuition Check
Do not read error here as a pilot mistake. In this context, it means a measurable difference between the altitude the system shows and the altitude it should show.
Example Sentence 1
Before flying in RVSM airspace, the operator must show that the aircraft's avionics error stays within the limits set by the certification standard.
Example Sentence 2
The pilot reported an avionics error after noticing the altitude readout differed from the assigned RVSM level.