V4002

=Night Vision Goggles and Accessories= NIGHT VISION GOGGLES NVGs are passive sensors that utilize image intensifier tube technology. An image intensifier tube is an electronic device amplifying available atmospheric illumination or light (i.e. moon, stars, sun, cultural lighting, etc.) NVGs rely upon the illumination reflected off the terrain or a target to form an image presented to the aircrew as a green monochromatic representation of the world. NVGs operate using the same principles as the human eye (reflected energy) with the following two exceptions:

NVGs are exponentially more sensitive to illumination than the human eye.

NVGs are sensitive to a different portion of the electromagnetic spectrum than the human eye.

If you didn't diagram and discuss the goggles (objective lens, photocathode, MCP, phosphorous screen, fiber optic inverter, diopter lens, ABC, and BSP) on your T4401 expect it on the T4402.

ACCESSORIES

a. Quick Don Lock Mount Possesses the vertical adjustment control, the lock release button and the low battery indicator (goes off when voltage drops below 2.2 volts signaling the user that remaining batter life is low).

b. Power Sources Two types of power sources used with the AN/AVS-9R, the Low Profile Battery Pack (LPBP) and the clip on battery supply. Clip on is designed for hand held use of the NVGs.

=NVG Performance Factors= Three major performance factors that influence NVG performance are illumination, terrain contrast, and atmospheric conditions
 * Tactics FTI NVG scene interp p 8-41

Illumination (lunar, night sky, solar influence, and artificial)
Learn to use the SLAP program for lunar and solar illumination data on a particular night.


 * Lunar illumination is determined by several factors; lunar cycle, moon angle, lunar albedo, and earth-moon distance.
 * i. The primary lunar illumination factor is lunar cycle or phase (e.g. new, full, quarter, etc.). each moon phase provides different levels of illumination. A lunar month is approximately 29.5 days. Moon phases are influenced by the time of year and global position.
 * ii. Moon angle, elevation, or altitude in relation to the horizon is the second most significant factor affecting lunar illumination. The moon is at its brightest when it is directly overhead and provides less illumination as it rises or sets. Moon elevation is also important because of the phenomenon known as terrain shadowing.
 * iii. Lunar Albedo is the reflectance of the sun off of the moon. The reflectance of the surface of the moon is better during the first quarter (waxing) than the third quarter (waning). Therefore the waxing moon is 20% brighter than a waning moon.
 * iv. Earth-moon distance is the least significant factor of lunar illumination. The moon's orbit is elliptical creating slight differences in the distance between the earth and the moon.  This 26% difference is deemed insignificant for NVG purposes.


 * Night sky illumination comes from a release of energy in the near-IR spectrum from atoms in the upper atmosphere known as air glow. Star light provides about .00022 of lux.


 * Solar influence comes from the sun's energy when it is below the horizon. Civil twilight is too bright (0-6 degrees below the horizon) and astronomical twilight (13-18 degrees below the horizon) is too dark as the only source of illumination. Nautical twilight (7-12 degrees below the horizon) can provide useful light for NVG's. Flying into the sky glow of the already set sun will cause the goggles to de-gain and you will lose detail.  Flying away from the set sun while give useful illumination.  NVG's will be most effective after the EENT (end of evening nautical twilight = sun set more than 12 degrees below horizon).


 * Artificial Illumination sources are anything that is man-made. These can be good or bad as they can provide useful illumination or they can cause the goggles to bloom or shutdown from activation of the BSP (bright source protection).

Terrain Considerations (terrain albedo, contrast, shadows)

 * Terrain albedo is the reflectivity of the surface of the earth. Surfaces such as snow or sand will reflect more light than asphalt or rock therefore the snow and sand will appear lighter in the NVG image.  The ability to see terrain features with NVG's is only a factor of the terrain's albedo.


 * Terrain contrast is the difference in albedo between two or more surfaces. The greater the difference, the easier it is to see the terrain.


 * Terrain shadows come from objects blocking moon light. Shadows during the day still have light energy in them allowing us to see in a shadow.  At night, there is very little light in a shadow not allowing us to see into them.

Atmospheric Effects p 8-5; 8-44(humidity, scattering)

 * Humidity is the presence of water vapor in the atmosphere. Water vapor in the form of thin clouds or fog does not allow us to see through them with the unaided eye. However since we can see near-IR light with the NVG's it is possible to see through the thin clouds and fog.  The NVG image becomes worse as the humidity level rises.


 * Scattering occurs when light strikes particulate matter in the air and changes it's path. If there is a lot of dust or smoke in the air it causes a loss in NVG performance.


 * Sometimes, scintillating is the only indication of degrading atmospheric conditions

=Aircraft NVG Compatibility= From FTI Pg 8-40:

To make aircraft interior lighting compatible with the most current NVGs, we must ensure that NVG "compatible" interior lighting is designed so that it does not fall within the spectral sensitivity range of the NVGs. Therefore, the NVG does not "see" the output from the lights, however the light output is sufficient for viewing around the NVG monoculars with the unaided eye.


 * INTERIOR LIGHTING NVG cockpit compatible lighting provides the capability to view interior aircraft instruments and to complete other aircraft tasks with the unaided eye, while not negatively impacting or degrading the NVG image. Due to increased gain, even the smallest escape of unfiltered light in the cockpit with have a negative effect on the goggles either directly or through windscreen glare.


 * EXTERIOR LIGHTING Exterior lights on the TH-57 are designed to be visible to the unaided eye and will generally have adverses effects when viewed through the NVGs. Searchlight/Landing light will primarily be used for low work. When flying in well lit areas with increased cultural lighting (i.e. the runway at NDZ during takeoff) use the searchlight/landing light to offset NVG "washout", as one instrutor told me "Fight light with light". Position lights should be set with the highest intensity consistent with NVG compatibility. Anti-Collision ("smacks") can have adverse effects when close to the ground.

=Emergency and Safety Considerations= RWOP 3.10.2

=Engine Failure at Night=

"Every attempt should be made to become familiar with the terrain over which night flights are made. If an emergency autorotative landing is necessary, normal daylight procedures are followed using the landing light to observe obstructions and select a landing area.