NVG lighting system design process
Def Stan 02-587 Part 3
Categories of NVG lights
Treatment of each category
Consolite has unrivalled experience in the design of warship lighting systems for use with night vision goggles (NVGs, sometimes also referred to as night vision devices, NVDs).
The design process starts with an in-depth understanding of all requirements for the lights, including their “normal”, non-NVG related functions, and the performance parameters required to permit their safe and effective use in the presence of NVGs. This frequently requires a careful balance between intensity, colour and NVG compatibility.
The performance requirements for NVG operations are defined in the UK Defence Standard Def Stan 02-587 Part 3, originally drafted by Consolite. This separates lights into various categories according to function and location on the ship, and covers all light types that could be visible to NVG-aided aircrew. It also takes account of the needs of ship’s staff who may or may not be using NVGs.
Broadly the categories are:
Aviation related lights. Those that the approaching aircrew wish to see through NVGs as they provide visual cues and an enhancement to spatial awareness during the approach.
Non-aviation related lights. Those that the aircrew do not wish to see, as they are not required and may even prove confusing. They may, however, have important functions for the ship’s personnel.
They can be sub-divided into:
Category B1. Required. Those that have a function in various areas of the ship to allow ship’s staff to perform their tasks during night operations, and so cannot be switched off.
Category B2. Not required. Those that are not required at all during night aviation operations.
Lights in areas of the ship where NVGs will be used.
Lights in areas of the ship where NVGs will not be used but where light could leak out and become visible to approaching aviators.
For completeness, everything else, i.e. lights in areas of the ship where NVGs will not be used, and which will never be visible to NVG users.
Def Stan 02-587 Part 3 goes on to consider in detail the requirements for each type of light in each category.
Approach to NVG Lighting System Design
In order to make the whole ship safe for NVG-aided aviation operations, all lights visible to aircrew must be considered and treated as a complete system.
Lights in Category B2 should be switched off or otherwise screened from view.
Lights in Category A are typically visual landing aids (VLAs), and can usually be treated as point sources. This means that NVIS Radiant Intensity (NRI) is the most useful parameter to define. NRI needs to be set to a range that is high enough to permit acquisition through NVGs at an appropriate range, while at the same time low enough that it does not disturb NVG performance at short ranges when the aircraft is close to or on the flight deck (this is termed NVG friendly). Not only that, but they also have to meet their requirements for unaided operations, so visibility to the naked eye must not be impacted.
Lights in Category B1 need to be fully NVG compatible as they do not need to be seen by aircrew.
Similarly lights in Categories C and D should be fully NVG compatible to avoid disturbing NVG operations.
Consolite uses its experience and its dark room test facilities to ensure that all lights on a warship will meet their respective requirements. This may be through the modification of existing lights by adding special filters, or it may be through supply of completely new lights, designed from scratch to have the required performance.