Definition
Departures from the target altitude or target airspeed planned for a given phase of flight. In energy management, these deviations are observable signals that the airplane's total energy state, or the way energy is being distributed between height (potential) and speed (kinetic), no longer matches what the pilot intended.
Plain English
The airplane is no longer at the altitude or airspeed the pilot planned for. It is higher, lower, faster, or slower than it should be — and that difference tells the pilot something about the airplane's energy that needs correcting.
Context Anchor
Seen during climbs, descents, approaches, pattern work, and any time the pilot is checking whether the airplane is staying on the planned height and speed.
Derivation
Deviation comes from the Latin deviare, meaning 'to turn off the road.' Here it simply means a measurable departure from the planned altitude or airspeed — the airplane has wandered off the intended path of flight values.
Why Pilots Care
Uncorrected deviations can lead to loss of control, airspace violations, or failure to meet performance requirements.
Grounding Statement
If the target is 80 knots and 1,000 feet, but the airplane is showing 90 knots and 900 feet, both airspeed and altitude have deviated from the target.
Intuition Check
Do not read “deviation” as a small error that can be ignored. In this context, any meaningful difference from the intended altitude or airspeed is a cue to notice, evaluate, and correct as needed.
Example Sentence 1
On final approach, the instructor pointed out small altitude-airspeed deviations early so the student could correct with pitch and power before they became a stabilization problem.
Example Sentence 2
Early recognition of altitude-airspeed deviations prevents an energy state from becoming critical in the traffic pattern.