Definition
The act of an aircraft making first contact with the landing surface during a landing. Under the ICAO definition, touchdown is the moment the wheels (or, for a flying boat or seaplane, the hull or floats) first meet the runway, water, or other landing surface.
Plain English
The instant the aircraft first touches the ground or water at the end of the approach.
Context Anchor
Seen in approach and landing discussions, especially where ICAO wording is used for glide path or runway reference points.
Derivation
From everyday English 'touch down,' meaning to make contact with the ground from above. Aviation borrowed it directly because it describes the moment exactly: the aircraft, until that point airborne, finally touches the surface.
Why Pilots Care
Knowing the precise touchdown point allows pilots to judge landing distance remaining, avoid runway excursions, and maintain safe rollout margins.
Intuition Check
Do not read this as only “the moment the wheels touch.” In the ICAO definition, it means the runway point where the planned approach path reaches the surface.
Example Sentence 1
The pilot held a slight nose-up attitude through the flare and felt the main wheels touchdown smoothly on the centerline.
Example Sentence 2
On short runways the pilot must confirm the touchdown point is within the first third of the pavement to ensure adequate stopping distance.