Definition
Published altitude, speed, or crossing requirements that an aircraft must meet at specific points along an instrument approach procedure. These are charted on the approach plate as fixed restrictions the pilot and the aircraft's flight management system must satisfy during the descent and approach.
Plain English
The required altitudes and speeds you must hit at certain points when flying an instrument approach. They are not suggestions — they are rules printed on the approach chart that you have to meet.
Context Anchor
Seen during vertical navigation planning, when checking whether the planned descent will meet the requirements on the instrument approach chart.
Derivation
From 'approach' (the segment of flight leading to landing) and 'constraint' (from Latin constringere, 'to bind together' or 'restrict'). A constraint is something that limits your choices — here, it limits what altitude or speed you can be at over a given point.
Why Pilots Care
Meeting these restrictions keeps the aircraft clear of terrain and traffic while maintaining a stable path to the runway.
Intuition Check
Do not read constraints as general advice. In this context, approach constraints are requirements or limits that shape the descent during the approach.
Example Sentence 1
Before starting the descent, the crew checked that all approach constraints had been loaded correctly into the FMS.
Example Sentence 2
The FMS automatically adjusted thrust to meet the approach constraints at the final approach fix.