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Lighting

Every cockpit light has to pass four gates before it illuminates: the bus has to be powered, the circuit's slot switch has to be closed, the potentiometer has to be turned up, and the emissive itself has to be working. A lamp that stays dark has failed one of those four, and they fail for different reasons.

From the README

Interior

  • Battery terminal voltage now sags under heavy load. It's most visible during engine start — the voltmeter dips and the cockpit lighting (including the glareshield annunciators) dims as the starter pulls the bus down.
  • Interior light dimming reacts to bus load.
  • Annunciator brightness now uses a per-lamp aging factor.
  • Added battery packs to emergency lighting. Armed emergency lights turn on when main power is lost and are powered for at least 15 minutes. (Limitation: the batteries are magically charged by the sim when the flight starts, trickle-charge is currently missing because of... erm... topological challenges.)
  • Corrected emergency exit lights logic; they now illuminate correctly in the ARM position upon loss of power.
  • Gated cockpit lighting and spoiler triggers to stop spamming events.

Exterior

  • Included hobanagerik's landing and taxi light tuning, with intensity brought up to MSFS 2024 values.

From the release notes

Verbatim from docs/release-notes-*.md. The tag is the version each item first appeared in.

Interior

  • [NEW] Interior light dimming reacts to bus load. (v2024.2.x)
  • [NEW] Annunciator brightness now uses a per-lamp aging factor. (v2024.2.x)
  • Added battery packs to emergency lighting. Armed emergency lights turn on when main power is lost and are powered for at least 15 minutes. (v2024.2.x)
  • Corrected emergency exit lights logic; they now illuminate correctly in the ARM position upon loss of power. (v2024.2.x)
  • Gated cockpit lighting and spoiler triggers to stop spamming events. (v2024.2.x)
  • [NEW] Annunciator lights work again (regression introduced by SU5 release 1.7.21.0). (v2024.2.x)
  • Battery voltage now sags under heavy load. Most visible during engine start — the voltmeter dips and the cockpit lighting dims as the starter pulls the bus down. (v2024.3.68)
  • Each glareshield annunciator bulb now has independent age and cycle counts. Bulbs dim continuously as they age and can burn out. (v2024.3.19)
  • Fixed the missing cockpit flashlight at night. (v2024.3.183)
  • Fixed incorrect default lighting, avionics and system states across the spawn scenarios. (v2024.3.183)

Exterior

  • Landing and taxi lights: cones tuned by hobanagerik <3, based on reference images, with intensity brought up to MSFS 2024 values. (v2024.3.183)

L:vars

For home-cockpit builders: every light switch, not a selection. Bind these from FSUIPC, Axis&Ohs, SPAD.neXt or MobiFlight. R is read-only state; R/W can be set.

Exterior

L:var R/W Meaning
DHC6_LIGHT_LANDING_1 R/W Left landing light
DHC6_LIGHT_LANDING_2 R/W Right landing light
DHC6_LIGHT_TAXI R/W Taxi light
DHC6_LIGHT_NAV R/W Navigation lights
DHC6_LIGHT_BEACON R/W Beacon
DHC6_LIGHT_STROBE R/W Strobes
DHC6_LIGHT_WING R/W Wing inspection light

Interior

L:var R/W Meaning
DHC6_COCKPIT_LT R/W Cockpit lighting
DHC6_UTIL_LTS R/W Utility lights
DHC6_UTIL_LT_CPT_RED R/W Captain's utility light, red mode
DHC6_UTIL_LT_FO_RED R/W First officer's utility light, red mode
DHC6_READING_LTS R/W Reading lights
DHC6_ENTRANCE_LTS R/W Entrance lights
DHC6_EMER_LT_STATE R/W Emergency lighting: off / armed / on
DHC6_SEAT_BELTS R/W Seat-belt sign
DHC6_ANNUN_LT_BRT R/W Annunciator panel brightness
DHC6_DIMMER_INT_FACTOR R Interior dim factor the load model is applying — drops as the bus sags
DHC6_DIMMER_EXT_FACTOR R Exterior dim factor
DHC6_DIMMER_ANN_FACTOR R Annunciator dim factor, reconstructed from battery current

Input events (B:)

MSFS 2024 Input Events are the sim's own binding mechanism, and unlike L:vars they are enumerable — MobiFlight, SPAD.neXt and Axis&Ohs discover them from the sim without anyone publishing a list, and Dev Mode's Behaviors tab shows the one under your cursor with Ctrl+G. That is why most aircraft publish L:var lists but not Input Event lists.

The Twin Otter currently exposes only two lighting Input Events:

Input event Covers
B:LIGHTING_IE_CEILING_LT_Set Ceiling light
B:LIGHTING_STROBE_1, B:LIGHTING_STROBE_1_Set Strobes

Everything else in the tables above is L:var only. For a hardware panel that is a real gap, not a documentation gap — Input Events accept _Set / _Inc / _Dec / _Toggle variants and are the better target for a physical switch.

Bulb ageing and burn-out are part of the Wear and tear system, not of lighting itself.