Height Above Aerodrome (HAA)

Height above aerodrome (HAA) is the height of the minimum descent altitude (MDA) above the published aerodrome elevation. HAA is used on circling approaches to give a meaningful indication of the aircraft’s clearance above the aerodrome surface during the circling manoeuvre.

HAA vs. HAT

• HAA (Height Above Aerodrome): MDA referenced to the aerodrome elevation; used for circling minimums
• HAT (Height Above Touchdown Zone Elevation): DH or MDA referenced to the touchdown zone elevation of the runway in use; used for straight-in approach minimums

On Instrument Approach Charts

Canadian instrument approach plates list minimums as: Decision Height (DH) in feet MSL for precision approaches, Minimum Descent Altitude (MDA) for non-precision, and then the HAT or HAA in parentheses. For example: “MDA 1,800 (600-1)” means the MDA is 1,800 ft MSL, the HAT is 600 ft, and the required visibility is 1 SM.

Related Terms

See also: HAT, MDA, Decision Height.