Aircraft certification bodies (EASA and FAA) have certain regulations related to aircraft performance requirement. Part 25 of regulations require that procedures must be established for the execution of go-arounds from landing configurations (balked landing) and from approach configurations (missed approaches). These procedures should analyze aircraft approach climb and landing climb capacities and restrict the operational limits accordingly.
Compliance must be shown at each weight, altitude, and ambient temperature within the operational limits established for the aeroplane and with the most unfavorable CG for each configuration.
Approach Climb Gradient
Considering that the aircraft is in approach configuration (intermediate flaps), if a missed approach is executed with one engine becoming inoperative, landing gear retracted and with go-around thrust, the minimum climb gradient must be 2.1% for twin engine aircrafts (2.4% for three and 2.7% for four engine aircrafts).
Landing Climb Gradient
In landing configuration, the steady gradient of climb may not be less than 3.2% with the engines thrust available within 8 seconds of movement of thrust from minimum flight idle to go-around thrust. (Impact of icing is also catered in regulatory requirements)
For Airbus A320 aircraft landing climb is never limiting.
This post is written from pilot’s point of view and all efforts have been put to share only necessary information.
Reference Video