In the aircraft design context, the PITCH TRIM Wheel (DSC-27-20-30 P 2/16) is a crucial component integrated into the aircraft's control system. Its primary function is to automatically reset the pitch trim to zero under specific conditions, specifically following a nosewheel touchdown. The trigger for this reset is the pitch attitude decreasing to less than 2.5 degrees and maintaining this attitude for a duration exceeding 5 seconds.
This mechanism is designed to enhance the aircraft's stability and control during and after the landing phase. By resetting the pitch trim to zero, the system helps maintain optimal pitch attitude for safe and efficient post-landing operations.
It's important to note a conditional aspect of this functionality. The automatic pitch trim reset is rendered inoperative when either the green or yellow hydraulic system is not pressurized. This constraint ensures that the system is reliant on hydraulic pressure for its operation, emphasizing the need for hydraulic functionality during the post-landing phase to enable the automatic pitch trim reset.
In summary, the PITCH TRIM Wheel plays a vital role in optimizing the aircraft's pitch attitude after nosewheel touchdown, promoting stability during critical phases of flight. The conditionality regarding hydraulic system pressurization underscores the interdependence of various aircraft systems for seamless and reliable functionality.