A very uncomfortable time. Trim is there to ease controls pressure, so pilot has little to no need to push or pull the yoke if properly trimmed. So at landing, a poor trimming technique (or forgetting to do so) will lead to a very uncomfortable controls setting.
The take off is another tale, because you there you don’t have a previous reference, you only can pull the controls until nose goes up, so if not properly trimmed when enough lift is generated the tail may go up causing the nose to crash into runway (specially if it has a propeller), or the plane may prematurely pitch up causing a tail strike (in some circumstances, it may cause the engine to loose performance resulting in a runway excursion).
Hopefully, most modern aircrafts have an aircraft unsafe to fly alarm, a horn that starts to sound when you set takeoff power but the flaps or trim is out of operational envelope (operational envelope is a funny word for limits). In more modern planes with sophisticated MCDUs like Airbus planes, or the Boeing 737-NG series, the FMS computes (or requires a pilot input) the pitch trim setting for takeoff, and it will automatically set the trim in such position.
Author – David Emiliano Vidal Escudero
