Why does the GL8 head-up display not show?

[MaggieFitz]

GL8 head-up display does not show because the power signal line is aged. Head-up Display: It refers to a display device that projects the main driving instrument attitude indicator and main flight parameters onto the pilot's helmet front or windshield. This allows the driver to see the main driving instruments and important flight parameters while looking forward at the external view. Developed from military aircraft, military planes generally use helmet-mounted head-up displays to facilitate piloting while searching for targets. Civil aircraft have also begun to adopt this technology, typically using a head-up display projected onto the windshield, mainly for approach and landing. Function of the Display: The head-up display can project flight parameters, targeting and attack information, self-test information, etc., in the form of images and characters, through optical components onto the combined glass in front of the cockpit via an optical/electronic display device.