Pinky Switch.

I've been messing around with the external lights and I wanted to share my findings and also point out some behaviors which are potentially not correct programatically.

PINKY SWITCH
According to the ED A-10C manual the pinky switch (located on the left throttle) is a 3-position switch that controls the external lights. The positions and functions are:

Forward - "Default"
Center - "Off"
Aft - "According to Panel"

This is not a whole lot of information. The A-10A manual (TO 1A-10A-1) has more to say about this switch.

Forward
Retention of illumination level set set on panel for formation lights, nose floodlights, and nacelle floodlights.
Changes position lights from bright to dim steady.
Removes power from the anti-collision solenoid switch so that the switch automatically returns to off.

This is a default "dim" mode. The formation strips and nacelle floods are set to a moderately dim level and cannot be manually adjusted. The anti-collision lights are forced off. Position lights and nose illumination however are still up to the pilot to control. The off/flash/steady switch still controls the position lights as normal except all position lights are forced to be dim (as required for taxi.) The nose illumination on/off switch determines whether the nose floods will be on at the moderate-dim level enforced by pinky-forward or off. This mode might be desirable when air-air refueling.

Center
(...)turns off position lights, formation lights, nose flood lights, nacelle floodlights, and anti-collision lights regardless of control panel settings. To reactivate anti-collision lights following (center position), the (pinky switch) must be moved aft and the anti-collision panel switch must be reset.

This is a mission-expedient way to set all lights off, usually for fencing in. It is impossible to use any of the white floods, formation strips, or position lights, or anti-collision ligths* when set to this "blackout" mode.

*It appears that the solenoid anti-collision switch behavior is slightly in error. The switch properly turns itself off but does so with regards to the wrong pinky switch positions. The A-C light switch is unable to remain on in the pinky-forward case and is able to remain on in the pinky-center and pinky-aft cases. It should be unable to remain on in both the pinky-center case as well as the pinky-forward case. The result is setting the pinky switch to center believing that the enemy will be searching for a dark aircraft when in fact the A-C lights are still blinking.

Aft - (...) allows for operations of the lights as set on the control panel.

This is what I like to think of as the "full manual" mode. The AAR nacelle floods are able to be set at any level. The formation light strips and nose floods can be set at any level. The position lights are forced to be full bright in either off, flash, or steady as the panel switch is set.

FORMATION LIGHTS
The formation lights consist of two lighting systems. One is the series of greenish panel strips placed around the aircraft skin surface. The other is a pair of white flood lights mounted on the wing leading edges pointed at the sides of nose exterior. When the pinky switch (master exterior lights switch) is set to forward the formation light strips and the nose illumination are set to a dim level regardless of the position of the dim-bright rotary or the nose illumination switch in the cockpit. With pinky center all formation lighting systems are off. With pinky aft the panel strips are controlled in brightness by the dim-bright cockpit panel rotary. If the nose illumination switch is in the on position then the nose flood lights are also controlled in brightness by the rotary switch. Otherwise the nose flood lights are off.

AIR AIR REFUELING LIGHTS
The AAR lights also consist of two lighting systems. One is flood illumination of the AAR nose receptacle, when the AAR door is open. The other is a pair of white flood lights mounted on the fuselage spine pointed at the fronts of the engine nacelles. The pinky switch has no effect on the operation of the receptacle flood lights and the receptacle lights may be used any time the AAR door is open regardless of the pinky switch's position.

The AAR nose receptacle lights should be steady white flood lights that are dimmable by the bright-dim rotary. However as of Beta2 this light is mistakenly coded as a single-intensity white strobe type light.

POSITION LIGHTS
The position lights are a set of three lights, red, green, and white around the aircraft. They have three modes of operation (steady, flash, off) as set by the panel switch and two brightness levels (bright, dim) as dictated by the pinky switch position.

ANTI-COLLISION LIGHTS
These lights flash red (A-10A manual describes them as white strobes but in DCS A-10C they are red) when the the anti-collision light switch is in the on position. This switch is a spring-loaded solenoid type that can only be held in the on position when the solenoid circuit is energized. Only in the pinky-aft "full manual" position does the anti-collision switch stay on when released. Anti-collision light use is not intended, recommended, or practical in all other positions of the pinky switch.

NVIS COMPATIBILITY
The Aux Lighting Panel has a switch which controls NVIS lighting. The "top" position turns on NVIS for the light on the top of the aircraft while the "all" position turns on all NVIS external lighting. I have not been able to witness this switch do anything meaningful mostly because I cannot view through NVGs in external view. I do not fully understand this switch or NVIS.