Takeoff Hold Lights (THL) in vatSys

The same automatic runway-conflict monitor as EuroScope. It draws a double row of red lights down the runway for an aircraft lined up to depart. They light whenever the runway ahead is occupied or about to be crossed.

• It is fed from your live vatSys tracks.
• It runs on anticipation.
• It needs an active controller.

For the full picture see Takeoff Hold Lights.

Arm and release

• Arm it. Each runway in the tree has a THL child node. Tick it. The monitor lights and clears the runway from live traffic automatically. You do not switch it bar by bar.
• THL is independent of the bar claim, but is itself a claim: one controller per runway. It follows the same eligibility, heartbeat and expiry rules as a bar claim - see who can claim what.
• Unticking releases it.

Nothing draws on the vatSys radar

Unlike EuroScope, the THL picture appears only inside the XPGuard window’s own map:

• The lit extent as a thick red line.
• An amber ring around the conflicting aircraft.
• A THL <runway> label at the aircraft in position.

Rather not watch the window? Turn on THL sound.

THL never replaces a verbal clearance

Exactly as in EuroScope, THL is an advisory aid. It does not issue or imply a takeoff clearance, and the lights going dark is not one.

Keep clearing takeoffs verbally - pilots are told the same.

Further reading - RWSL in the real world

XPGuard’s THL follows the Runway Status Lights (RWSL) system. RWSL is an ICAO-recognized runway-safety concept operated in the real world by EUROCONTROL and the FAA:

• FAA - Runway Status Lights
• EUROCONTROL - Runway Status Lights
• SKYbrary - Runway Status Lights (RWSL)