Definition
An aircraft system that warns the pilot, by visual and aural signals, when the aircraft approaches or deviates from a preselected altitude. It typically gives an advance alert as the aircraft nears the selected altitude during a climb or descent, and a separate alert if the aircraft subsequently drifts away from that altitude once level.
Plain English
A system you set to a chosen altitude. It beeps and flashes a light to tell you when you're getting close to that altitude, and again if you wander off it after leveling out.
Context Anchor
Seen on instrument panels and electronic flight displays during climbs, descents, and level-offs, especially when flying an altitude assigned by air traffic control.
Derivation
Altitude comes from the Latin word altus, meaning “high.” Alert comes from an old Italian phrase meaning “on the lookout.” Together, the term points to a system that watches the aircraft’s height and gets the pilot’s attention when needed.
Why Pilots Care
Helps prevent altitude deviations that can trigger ATC conflicts, traffic alerts, or loss of separation.
Intuition Check
Do not assume the system flies the airplane for you. An altitude alert system warns the pilot; it does not necessarily climb, descend, or hold altitude unless it is connected to other equipment designed to do that.
Example Sentence 1
Before starting the descent, the captain set 10,000 feet in the altitude alert system so it would chime as they approached the new level-off.
Example Sentence 2
As the aircraft climbed through 9,500 feet the altitude alert system sounded to confirm the 10,000-foot target.