The VS-17 is a signaling device used by military personnel to send signals to aircraft, and to mark improvised landing sites.
The VS-21 is a replacement for the VS-17 that provides an infrared signature, allowing use in low visibility conditions via thermal imaging.
See also Air-to-ground communication Air navigation Signal square
References
External links
MIL-P-40061, Panel Marker, Aerial Liaison, VS-17/GVX