Definition
A sudden, abrupt pitching of the aircraft's nose downward that occurs without pilot input, typically caused by a tailplane (horizontal stabilizer) stall when ice has accumulated on the tail. The iced tailplane loses its ability to produce the downward aerodynamic force needed to hold the nose up, and the nose drops on its own.
Plain English
The nose of the airplane suddenly pitches down by itself, even though the pilot did not push the controls forward. In icing conditions, this usually means the tail has stalled.
Context Anchor
Seen in icing discussions, especially when recognizing symptoms of a tailplane stall during approach, flap use, or other low-speed flight.
Derivation
Uncommanded' means not ordered or requested -- here, not commanded by the pilot through the controls. The phrase emphasizes that the airplane is doing something on its own, which is a key warning sign.
Why Pilots Care
This is a critical warning sign of tailplane icing that can rapidly lead to loss of control if the pilot does not immediately reduce angle of attack.
Grounding Statement
The key point is that the nose drops on its own, not because the pilot deliberately pushed it down.
Intuition Check
Do not read “uncommanded” as meaning mysterious or impossible to explain. It means the aircraft moved in a way the pilot or autopilot did not ask for. Do not read “pitch” as speed or sound here. In this context, pitch means the aircraft’s nose moving up or down.
Example Sentence 1
After lowering the flaps on approach in icing conditions, the crew felt an uncommanded nose-down pitch and immediately suspected a tailplane stall.
Example Sentence 2
Recognition of an uncommanded nose-down pitch allows the crew to apply the correct recovery procedure before the situation worsens.