Definition
Two indicator arrows on the side of a Horizontal Situation Indicator (HSI) that show the aircraft's position relative to the glideslope during an ILS approach. When both pointers are centered on the reference marks, the aircraft is on the correct glide path; if the pointers are above center, the aircraft is below the glideslope, and if below center, the aircraft is above the glideslope.
Plain English
Two small arrows on the HSI that tell you whether you are above, below, or on the correct descent path during an instrument approach. Center the arrows and you are on the slope.
Context Anchor
Seen on an HSI during an instrument approach that provides glideslope guidance, especially while tracking the descent path to the runway.
Derivation
Dual' means two, because there is one pointer on each side of the HSI for redundancy and easier scanning. 'Glideslope' refers to the angled radio beam that defines the correct descent path to the runway. 'Pointer' is simply the moving arrow that indicates a value.
Why Pilots Care
They provide immediate visual confirmation that the aircraft is maintaining the proper vertical path for a safe landing.
Intuition Check
“Dual” does not mean there are two different descent paths. It means the display shows two matching pointers for the same glideslope indication.
Example Sentence 1
On the ILS approach, she scanned the dual glideslope pointers and made a small power reduction to settle them back onto the center reference.
Example Sentence 2
A slight upward correction brought the dual glideslope pointers back into alignment with the reference marks.