Answer :
Final answer:
The 'Runway Threshold Bar' signifies the start of the runway for takeoff and landing in airplane terminology. It acts as a visual indicator for pilots, marking the beginning of a legally valid zone for take-off or landing.
Explanation:
The 'Runway Threshold Bar' in airplane terminology is a visual indicator on an airport runway that signifies the start of the runway from which the takeoff run or landing roll begins. It's typically represented by a series of parallel white lines painted across the width of the runway. This bar signals to the incoming pilot that they are approaching a suitable place to land.
When an airplane is ready for takeoff, it will line up with this indicator, as it shows the earliest point they can legally start their takeoff roll. Conversely, when landing, safe landing must not be initiated before this threshold bar to prevent any potential accidents. Other marks may exist on the runway, such as a centerline or end markers, but these have different purposes and appearances.
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