UH-1N FAM-115

Goal: Introduce NVD techniques during HLL.

=Requirements=
 * 1. Brief and discuss the Light Level Planning Calendar Computer Program, cockpit lighting, external lighting, NVD scan, HLL, LLL, meteorological effects, and cultural lighting.
 * 2. Demonstrate/introduce takeoff to a hover, takeoff from a hover, normal takeoff, low work, basic airwork, normal approach, landing from a hover, and autorotations.  PUI to complete a minimum of 5 autorotations.
 * 3. Review SFAM-114 in the aircraft.

=Light seo services and Lighting=

Light level planning calendar computer program (Helo NVD Manual Ch 2)
Solar/Lunar Almanac Program (SLAP). Due to the wide and rapid changes in lunar illumination, a computer program was developed to help night systems squadrons properly plan their missions. seo services This information is provided in the Solar/Lunar Almanac Program (SLAP) that is available for fleetwide distribution. In addition, the program will also be incorporated into the Joint Mission Planning Software (JMPS). The computer program provides a global prediction of sun and moon position for most areas of the world, and can output this information in various formats through a number of menu options. The two most useful options are the Light Level Planning Calendar and the Sun and Moon Position Chart.

Cockpit lighting
As low as possible to still read gauges but not wash out goggles. Ensure gauges are clean to make them easier to read. Must be NVG compatible (blue-green inst light).

Helo NVD Manual Ch 7:
Any incompatible lighting introduced into the cockpit will affect the NVG gain to some degree. A large change in gain that leads to an obvious degradation in visual acuity will be apparent to all aircrew regardless of NVG experience. The real problem occurs when there are subtle degradations in visual acuity that may not be readily apparent to the aircrew. In these cases, important details may be missed. Additionally, an incompatible light does not have to be within the NVG FOV for it to have an effect on gain. Aircrew should also keep in mind that incompatible cockpit lighting cannot be turned down enough to make it compatible. If the lights can be seen with the unaided eye, they will affect the NVGs. In fact, even if an incompatible light is turned down too dim for the unaided eye to see, the NVGs will still likely be adversely affected due the IR signature of many lamp filaments. Thus, the danger of attempting to turn down incompatible cockpit lights to make them compatible is double edged: first, they will continue to degrade NVG performance; second, when turned down to a very low intensity, vital instruments may not be readable.

External lighting
Single-ship: Nav lights ON Steady Bright, Anti-Collision light ON, Form lights ON (highest level).

Formation: last a/c in form has Anti-Collision light ON, all a/c with Nav lights ON steady dim, IR lights ON (highest level tolerable by other a/c in formation).

NVD scan 40ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ° FOV only, Field of regard is how much you can see during your NVG scan. By scanning, you build into memory where things are for when you are no longer looking at them.

High Light Level (HLL) Above .0022 lux Low Light Level (LLL) (Helo NVD Manual Ch 19) NVG performance in conditions of low ambient illumination is characterized by decreased resolution, visual acuity, contrast and hazard detection range. Low ambient illumination also creates an increase in the blooming effect from artificial illumination sources (i.e., aircraft lighting, muzzle flashes, rocket motors, flares, and cultural lighting). The decreased resolution, visual acuity, contrast and hazard detection ranges are a result of the small amount of light (photons) available to strike the photocathode. Since the photocathode is not completely saturated by light, the image at the eyepiece lens has "video noise" commonly referred to as "graininess", "sparkling" or "snow". This situation is similar to television reception with a weak signal. The picture quality is poor and will remain so until the signal becomes stronger. Signal strength is a function of illumination with a stronger signal occurring with higher light levels.

In a low light level (LLL) condition, the combination of incompatible lights and the ABC feature results in an increase in the blooming effect. The ABC is the gain control functions to maintain constant output brightness at the eyepiece lens. Under LLL conditions, the ABC is at maximum gain. When a light source enters the NVG field of view (FOV), the light appears extremely bright with a significant halo effect. If the light source is bright enough, as with a flare, both the NVGÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂs Bright Source Protection and (BSP) and ABC will be activated to reduce system gain. The resultant decreased gain increases difficulty with seeing the surrounding terrain features.

Visibility is further degraded by the halo effect or blooming around the light source. This phenomenon occurs when electrons from the area of the photocathode, which receives the light source photons, "bleed over" into neighboring channels of the microchannel plate (MCP). The NVG image nuances are not necessarily unique to NVG performance below 0.0022 lux. However, these effects become much more significant in determining NVG performance in the low light regimes than they do in high light conditions. Mission planning should reflect this phenomenon.

Meteorological effects (Helo NVD Manual Ch 5)
Water vapor exists at all temperatures. Because the amount of water vapor a cloud formation can hold increases with temperature, summer clouds generally have higher liquid water content than winter clouds. Dense clouds can be easily seen with NVGs, especially when silhouetted against the night sky. This also means that thick clouds can reduce the amount of illumination that strikes the ground, thereby reducing the available luminance to the NVGs.

Thin and wispy clouds have greater space between particles, therefore a greater amount of the near IR radiation will be passed without scattering. Near IR wavelengths have a greater chance of passing through these clouds without being scattered than do the shorter visible wavelengths. For this reason, it is possible for thin, wispy clouds to be seen by the naked eye (visible light or shorter wavelengths) but remain invisible when viewed through NVGs. This potential ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂinvisibilityÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ of thin clouds, fog or marine layers is possible given three conditions: (a) The clouds are thin and wispy, at least on the edges. (b) The clouds are low level and set in against the terrain. (c) The ambient illumination is either very high or very low, degrading NVG performance.

The presence of thin clouds that progress into thicker ones can result in hiding terrain features. This can obviously create a severe hazard for NVG operations. Low clouds lying upon and between hills present a particularly dangerous situation due to the inability of the aircrew to distinguish between the clouds and the terrain. Clouds reduce illumination to an extent dependent on the amount of cloud coverage and cloud density or thickness.

For example, a thick, overcast layer of clouds will reduce the ambient light to a much greater degree than will a thin, broken layer of clouds. The aircrew must be alert for a gradual reduction in light level and notice the obstruction of the moon and the stars. The less visible the moon and stars, the heavier the cloud coverage.

If the NVG image becomes grainy and begins to scintillate (sparkle), this is an indication that weather may be causing a low ambient light condition. Also, shadows caused by broken or scattered cloud layers blocking the moonÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂs illumination can be seen on the terrain. Although clouds can decrease illumination and resulting luminance from the moon Acting Corps and stars, they can, especially if low and broken to overcast, reflect enough cultural lighting to help offset the loss of lunar illumination. Obviously, this will only occur in and around areas with significant cultural lighting and is only helpful if it is clear beneath the overcast.

Since fog tends to stay close to the ground, it is more a navigation hazard to rotary wing aircraft than to fixed wing aircraft; however, fog can mask or partially mask ridgelines and other navigational features making it more difficult to navigate or use funneling techniques in the target area. One way to note an increase in the moisture content of the air while utilizing NVGs is to observe a decrease in the intensity of ground lights. This is especially obvious if you are flying at an altitude high enough to use as a comparison ground lights that might be out of the area of increased moisture content. In addition, the halo effect noted around lights when viewed directly with NVGs will tend to get larger and more diffuse in an area of increased moisture. The enhanced contrast in an area illuminated by ground lights will also be lessened or absent.

Due to small droplet size and low density, light rains or mists cannot be readily seen with NVGs. However, contrast, distance estimation and depth perception will be affected due to light scattering and the resulting reduction in light level. Heavier rains will be more discernible due to luminance blocking and more obvious signs such as rain on the windscreen.

As with other forms of moisture, the density of the flakes will determine how much illumination and luminance is blocked and therefore how much degradation occurs to the NVG image. Snow can occasionally be of help, however, in that it can reflect available light and thus enhance luminance when on the ground. In addition, consideration should be given for the potential of "white out" when conducting landings in snow. The rotor induced "white outÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ will effectively block luminance and therefore, significantly impact the NVG image.

The effect of blowing sand or dust is similar to that created by snow except that the particles are far less reflective and much larger. This condition is significant since dust/sand particles completely block the near infrared light from striking and reflecting from the terrain. Since there is less luminance, the scene is darker. During vertical operations or with strong winds, there can be an almost total block of IR radiation resulting in a ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂbrown out.ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ The impact of battlefield obscurants on NVG performance is similar to those mentioned above and depends on particle size and density. NVG visibility ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂinsideÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ these obscurants is poor.

Lightning will temporarily increase illumination, but looking directly at it will cause NVGs to shut down briefly. However, when not looking directly at it, lightning will briefly illuminate the area giving you an enhanced NVG image. The brief duration and enhanced image clarity can create the impression that objects are much closer than they really are. Whether it this is a help or hindrance depends on the frequency of lightning and its source relative Fresno Lawyer to your flight path. Since lightning has no particulate matter and does not affect thermal contrast, it will not affect the FLIR image.

Cultural lighting
Can wash out goggles. Step-down is sometimes necessary in a form to be able to see the lead aircraft. With on overcast layer, can provide reflective light Acting Corps to make objects that may not otherwise be visible able to be seen.

=Night Vision Goggles (Helo NVD Manual Ch 3)= Night Vision Goggles (NVGs) are passive sensors that utilize image intensifier tube technology. An image intensifier tube is an electronic device that amplifies available atmospheric illumination or light (i.e., moon, stars, sun, cultural lighting, etc.). NVGs rely upon this illumination reflected off the terrain or a target to form an image that is 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: (1) NVGs are exponentially more sensitive to illumination than the human eye and (2) NVGs are sensitive to a different portion of the electromagnetic spectrum than the human eye. The first optical component Acting Corps of the NVG is the objective lens. The lens is actually a combination of optical elements that function to focus the incoming rays of light onto the I 2 tube. The AN/AVS-9R objective lens possesses variable focus with a focal range spanning from 25 mm to beyond optical infinity. NVG "minus blue" objective lens filtering facilitates aircraft cockpit and display compatibility by restricting wavelengths of energy entering the intensification process. This allows the use of cockpit lighting that will not adversely affect NVG gain and ultimately, NVG image quality.

GEN 3 tubes possess three primary internal components:
 * (1) Photocathode,
 * (2) Microchannel Plate (MCP) and
 * (3) Phosphor Screen.

The photocathode is responsible for converting the incoming visible and NIR energy into electrical energy in the form of electrons. Since the sensitivity of the photocathode extends into the near infrared, they are able to detect energy in that region which is invisible to the human eye. Third generation tube is far more sensitive in the region where near infrared light from the night sky is plentiful.

Electrons exiting the photocathode are channeled next through the MCP (Figure 2-6). The MCP is a very thin (1 mm) wafer comprised of millions of tiny glass tubes or channels, and is located between the photocathode and the phosphor screen. The inside passages of the MCP tubes are coated with a material that causes secondary electron emissions when a passing electron strikes them. For each electron that enters the a MCP, 1,000 or more will exit.

These electrons are in turn accelerated forward, maintaining their relative spatial position, until they strike and excite the phosphor screen. The phosphor screen is comprised of a very thin layer of phosphor deposited on the inside of the rear window (fiber optic). The basic function of the phosphor screen is to convert the electron beam energy to light.

Image inversion is accomplished by attaching the phosphor screen to a fiber optic inverter. The fiber optic inverter also collimates the image, making the image at the eyepiece lens appear to be at the appropriate distance from the viewer. Without collimation, the eye's focus would be set for the distance to the eyepiece lens (about 25 mm), which would place severe strain on the eye and lead to significant human factor problems.

The eyepiece lens is the final optical component of the AN/AVS-9R NVG. As with the objective lens, the eyepiece lens is a series of optical components. The function of the eyepiece lens is to focus the light from the phosphor screen and fiber optic inverter onto the eye. The diopter adjustment for this lens allows wearers to move the focus point to the appropriate location at the back of the retina. The majority of personnel that use corrective lenses to correct for astigmatisms will still need to use spectacles or contact lenses when using NVGs.

All Omnibus-III / IV AN/AVS-6 and AN/AVS-9R NVGs possess a 25mm designed eye relief which allows the NVGs to be kept farther away from one's eyes while still maintaining a 40 degree Field of View (FOV). This increased eye relief translates into greater look-under ability and clearance for use of special mission equipment (i.e., LEP, CBR gear, etc.). Fleet aircrew must properly set the fore and aft adjustment in order to realize the full benefits of the increased eye relief. Proper focusing procedures are discussed later, but the essence of proper placement is to keep the NVG as far away from the eye as possible, while retaining 40 degree FOV.

The primary function of a Night Vision Goggle is to amplify the photons of light that enter into the system. This is loosely called ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂgain.ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ Gain is used loosely to represent both ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂLuminous GainÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ and ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂSystem Gain.ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ The luminous gain is defined as the ratio of the NVG's output brightness to the input illumination. Luminous gain is measured solely through the Intensifier tube. Essentially, gain will govern the NVG image brightness for low light level inputs. NVG gain increases as light levels approach approximately quarter moon illumination levels. Below approximately quarter moon, subsequent drops in illumination will not result in substantial increases in gain. Constant exposure of the image intensifier tube to bright light sources may result in damage to the photocathode or the MCP. To prevent damage to the I2 tubes, the power supply has been designed with two automatic protection features designed to control the gain of the I2 tube, extend NVG service life, and have a direct effect on the performance and resolution of the NVGs.

Automatic Brightness Control (ABC) Circuit. The ABC circuitry automatically adjusts MCP voltage to maintain NVG image brightness at a preset output for a wide range of illumination levels by controlling the number of electrons that exit the MCP. This function causes the NVG to ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂgain upÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ or ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂgain downÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ according to the light level. Therefore, the benefit derived from high gain intensifier tubes is realized only at low illumination levels since above a certain illumination level, the ABC holds image brightness constant. The ABC circuit also provides a protective function to aircrew by limiting the effect of sudden bright flashes (i.e., forward firing munitions, etc.).

Bright Source Protection (BSP). Image intensifier tube exposure to bright light sources, left unchecked, could result in damage to the photocathode, the MCP, and the eye. The bright source protection (BSP) circuit limits the number of electrons leaving the Photocathode by reducing the voltage between the photocathode and the input side of the MCP. This feature automatically activates when high input light levels cause excessive photocathode current to flow. Aircrew will notice activation of the BSP when an incompatible light source enters the NVG field of view and the I2 tube shuts down or ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂdegainsÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ leading to reduced NVG image contrast and detail.

=Image Defects=

1. Shading.
Shading is that condition encountered when a full image cannot be obtained. It appears as a dark area along the edge of the image. Attempt to eliminate shading by readjusting the controls, i.e., tilt, IPD and vertical controls. Shading can also occur because of a shift in the MCP caused by the goggles being dropped or handled roughly. If shading can not be corrected by control readjustments or repositioning the mounting bracket on the helmet, turn the goggles in for maintenance.

2. Edge Glow.
Edge glow appears as a bright area along the outer edge of the image. It is usually the result of an incompatible light source in the goggles FOV, although it can be the result of a MCP shift due to mishandling. If noted, move your head or cup your hand around the periphery of the objective lens in an attempt to alleviate the condition. If the edge glow does not disappear, turn the goggles in for maintenance.

3. Honeycomb Pattern.
At times of very high luminance, a hexagonal (honeycomb) pattern may be visible across the entire intensified FOV. This pattern is an artifact of the manufacturing process in which the fiber optics are assembled within the tube. Normally it is faint in appearance and does not affect NVG performance. If you see a bold outline during normal NVG luminance conditions, write a MAF and do not use the goggles.

4. Bright Spots/Dark Spots.
Bright spots and dark spots are actually the same condition in early and later phases respectively. The spots occur as the result of irregular emission points on the Photocathode and are generally caused by turning the NVGs on in a bright room, subjecting them to strong point sources of illumination or Laser damage. Bright spots may appear constant or occasionally flicker in the early stages. In time, the bright spots turn into dark spots as electron saturation literally "burns through" the photocathode. Neither condition necessarily means that a tube is unusable. There is a specification that limits the size, location, and number of dark spots on the NVG image. If the number and/or size of the spots present in the image seem excessive or is distracting, turn the goggles in for maintenance.

5. Distortion.
The most common types of distortion noted in the NVG image are ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂbendingÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ or wave distortion and ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂshearÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ distortion. Bending distortion results in a wavy appearance, usually in the horizontal or vertical directions. Shear distortion results in a choppy appearance somewhere in the image. If distortion is present and it is deemed likely to interfere with normal operations, do not use the NVG.

6. Flickering.
Flashing, flickering, or intermittent operation of the NVG may indicate an impending failure of the tube, faulty wiring, or impending battery failure. If replacing the batteries does not alleviate link building service the condition, turn the goggles into maintenance. If airborne, take appropriate action.

7. Scintillation.
At low light levels, resolution is limited by internal noise that prevents a clear build up of the image and effectively reduces image contrast. The key parameters are photocathode sensitivity and the noise figure for the tube. This noise signal is seen by the pilot as a sparkling effect, and is referred to as image scintillation. The higher the noise, the lower the resolution. The higher the photocathode sensitivity, the higher the resolution for low light levels.

8. Tilt Defects.
The tilt lever on NVGÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂs aligns the optical axis of the monocular assemblies with the visual axis of the eyes. If this tilt lever is too loose or too tight it can cause operational problems. The most stable position for the tilt lever is center of movement. If the tilt lever is too loose or too tight, then return the NVGs to flight equipment.

9. Tube Alignment and Optical Image Differences.
In a binocular helmet mounted system, such as AN/AVS-9, there are two images, one for each eye. The two images may differ because of horizontal and vertical alignment error or image differences. Alignment errors may result because the two optical axes are not parallel. Some imperfection can be present without appreciable adverse effects.

10. Collimation
Collimation is process by which the NVGs take the separate pictures from the two monoculars and align them for viewing. Collimation can be seen when using NVGs that are biocular or binocular. When proper collimation does not occur the aviator can see an oblong field of view, two separate pictures or shadowing on the edges of the field of view. This will increase eye fatigue and eyestrain, and have possible negative physiological affects. Mechanical problems may also cause improper collimation.

=Illumination (Helo NVD Manual Ch 2)=

Lunar Cycle.
The primary lunar illumination factor is lunar cycle or phase (i.e., new, full, quarter, etc.). Each moon phase provides different levels of illumination. A lunar month is approximately 29.5 days. There may be times as a new NVD player that you will find yourself ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂchasing the moonÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ in order to find nights where illumination is sufficient for High Light Level (HLL) operations. Moon phases are influenced by the time of year and global position (latitude and longitude).

Moon Angle.
Moon angle, elevation or altitude in relation to the horizon, is the second most significant factor that affects lunar illumination. The moon is at its brightest when itis directly overhead and provides less illumination as it rises or sets. Many people will look at a low angle full moon and assume high illumination. However, a quarter moon high overhead can actually be brighter. Moon altitude is also important because of the phenomenon known as terrain shadowing

Lunar Albedo.
A difference in the albedo (reflectance) of the illuminated portions of the moon surface during the lunar cycle is the third factor. For example, the moon is about 20% brighter during the first quarter (waxing) than it is during the third quarter (waning) due to differences in the lunar surface.

Earth-Moon Distance.
The final and least significant factor is the variation in the earth-moon distance due to the elliptical nature of the lunar orbit around the earth. The changes in illumination resulting from this 26% change in distance are deemed insignificant for NVG purposes.

Night Sky Illumination.
Moonless nights also have significant usable light for NVG operations. This is due to the large near IR composition of night sky illumination. This night sky near IR energy matches the peak sensitivity of the AN/AVS-9R. It is possible to fly effectively with NVGs under these conditions with a good training program and proper pre-flight mission planning. On a moonless night, about forty percent of the light is provided by emissions from atoms and molecules in the upper atmosphere known as air glow. Starlight is the other significant light source and provides about 0.00022 lux (about 1/10 the level of a quarter moon). In addition, other possible night sky illumination sources include: auroras (luminous rays, ribbons, and arc patterns caused by charged particles), gegenscheins (diffuse, faint light caused by sunlight reflecting off of air particles), zodiac lights (faint elliptical disks around the sun caused by reflection  DiamondLinks off particulate matter) and noctilucent clouds (usually colored, thin clouds with unknown origin).

Solar Influence.
Depending upon the azimuth and relationship to flight path, the sun can provide adequate light for NVG operations at nautical twilight (7-12 degrees below the horizon). Civil twilight (0-6 degrees below) is too bright and astronomical twilight (13-18 degrees below) is too dark for NVG operations (considering only the contribution of the sun).

Although the sun may provide helpful illumination if aircrew are flying away from it; a sun that is well below the horizon can continue to be a significant nuisance if flying toward it, especially in mountainous terrain. For NVG aided operations, aircrew should plan for NVGs to be most effective following the end of evening nautical twilight (EENT) or when the sun has set at least 12 degrees or greater below the horizon.

=Artificial Illumination sources= Artificial Illumination source (i.e., lights from cities, vehicles, weapons, flares, etc.,) can provide illumination for NVG operations. As with the sun, these artificial illumination sources can be helpful or hazardous depending upon the relative placement in or out of the NVG field of view (FOV). As with a low moon angle or the setting / rising sun, a potential exists for the NVG automatic gain control system (Bright Source Protection) to be activated causing the NVGs to ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂbloomÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ or ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂshutdown.ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ

Artificial Light Sources (Ch 5)

 * 1. NVG. Highly populated areas can generate very significant levels of ambient light. Many of the discrete artificial sources exhibit overlapping halos in the NVG image. This substantially reduces contrast and detail between sources. Improvements in NVG technology through the AN/AVS-9R replacement program have decreased the size of the halos around cultural lighting, but the halos do remain.  Although lighted areas can be seen from great distances, specific buildings or objects within the lights cannot always be distinguished.


 * When associated with overcast, city lights can supply increased illumination to less illuminated areas by reflecting light from the bottom of the cloud layer. Sodium lights used on the back of farmhouses can make a rural area look like an industrial complex. A baseball field lit up at night can look like a small town.  Automobile lights can provide excellent cues to the presence of a road, but direct light from an automobile, especially halogen types, can be very disconcerting at low altitude.  The red lights on top of radio and microwave towers are visible from 10-30 miles, depending on the atmospheric conditions, but their range and relative distances can be hard to judge.  Aircraft anti-collision lights can be seen at even greater distances.


 * Weapon flashes, flares, and explosions, all of which contain significant levels of near IR radiation, are intensified by the NVGs. Since dark adaptation is unnecessary for NVG use, the bright flashes are of minimum impact on the unaided eyeÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ¢ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂs capability to see the intensified image. Simply scanning away from the source or changing aircraft heading can help compensate for unwanted illumination. If you must look into the bright light source it may be necessary to revert to instrument flight for brief periods realizing that maneuverability is adversely impacted during this time.