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 The tremendous changes in the balance of military alliances worldwide in the last year or so will have a tremendous effect on military planning. Options range from no change from previous plans to complete abolition of the Department of Defense. Somewhere between these extremes falls various options for upgrading, instead of replacing, our present fleet of tactical airplanes. For such options to work, the people writing the upgrade specifications need to know what they are writing about. From some of the specifications I've seen for the F-16, this is not always the case.
Every model of the F-16 has many systems that can be upgraded. For the sake of brevity (and editorial restraint), I'll limit today's sermon to two areas: night vision goggles, or NVGs, and head-steered or fixed forward-looking infrared, or FLIR, systems. I'll sing praises and blast faults of other systems in future issues.
To be effective, a night vision goggle system must have three ingredients. The first has to do with the placement of its light intensification tube.
Light intensification tubes are wondrous. They can amplify ambient light between 8,000 and 12,000 times. From the latitude here at Fort Worth (thirty-two to thirty-three degrees north), you can see the Northern Lights (Aurora Borealis) with them as soon as you get to any altitude and away from the city's lights. If you know where to look, you can see various gas nebulae without optical magnification. Those billions and billions of stars that Carl Sagan keeps mumbling about pierce the black. The Milky Way looks milky.
Closer to Earth, you can see airplanes at night (if their lights are on) from distances that would blow away ol' Chuck's most outrageous – and patently bogus – claims of daylight vision. The first time you look through a pair, you' be scared when you realize that all those airplanes have been there in the past.
Depending on where these tubes are placed, NVGs can be divided into two broad types. For the sake of this discussion, I'll refer to them as ANVIS (short for Aviator's Night Vision Imaging System) and Cat's Eyes. With the ANVIS type, you look directly through the light intensification tube. With the Cat's Eyes, you look at an image that has been piped to your eyes from a remote intensification tube. Although you will see or hear about many different NVGs from many different contractors, they all fall into these two categories.
The distinction is important because the ANVIS-type does not work well in a fighter cockpit. ANVIS NVGs make it extremely difficult to see cockpit displays. If you are trying to view a forward-looking infrared image on the head-up display, or HUD, (an image from a Low Altitude Navigation and Targeting Infrared for Night, or LANTIRN, pod for example), you must now view the real world through two levels of less-than-optimal resolution. Not good. Since all Cat's Eyes NVGs use a combining glass arrangement, you can see what you need through what is essentially a thick pair of glasses. These goggles work especially well if some sort of automatic cutoff is provided for them when you want to look inside the cockpit.
If you haven't already guessed, an automatic cutoff is numero dos on my three-part ingredient list. Depending on the cockpit configuration, NVGs must have an automatic cutoff for one or more parts of the cockpit. I won't take time to explain how this is done, but take it on faith that an automatic cutoff system is not too complex.
 ANVIS goggles can be shut off automatically as well. But you'll find yourself staring down two black, and I mean really black, holes. The relatively clear combining glass of the Cat's Eyes NVGs provide a much more direct view of the cockpit.
The third ingredient has to do with the cockpit lights. NVGs don't discriminate between a panel light in your cockpit and a bright star in the sky. They amplify every light between 8,000 and 12,000 times. Even though you turn down your panel lights to a level that you think is essentially off, the cockpit will be filled with bright constellations of green, glowing orbs. Those very dim lights will cast 8,000 to 12,000 times brighter reflections in the canopy as well.
An automatic gain control in the tubes modulates the light amplification to protect you and the system from sudden bright lights. The gain control responds to cockpit illumination as well (and will lower the light amplification accordingly). This will, in turn, lower the system's effectiveness to outside lights.
This conflict can be resolved by adding NVG-compatible lighting, the third ingredient. Since the goggles are sensitive to light in the lower part of the visible spectrum and just below (near infrared for you Scientific American readers), blue-green lighting (which is just above the lower part of the visible spectrum) will go undetected. Voila. Eight thousand to 12,000 times zero is still zero. The exact frequency of this invisible color for the NVGs varies from application to application, but it is essentially what you and I would call blue-green.
While the goggles can't pick up this blue-green lighting, the human eye actually sees best in light from this part of the spectrum. Our increased sensitivity to this part of the spectrum is an indirect benefit of the NVG-compatible lighting; you can read the gauges better with the blue-green lighting than you can with the red, orange, or blue-white lighting currently in vogue. But this benefit has its drawback as well. Your eyes will be more sensitive to the canopy reflections of the cockpit lights. Although some people would try to pass this off as a minor irritation, it can be very distracting.
Furthermore, light intensification tubes can be tuned so that they intrude into this blue-green part of the spectrum. They can then be used to detect NVG-compatible cockpit lighting of other planes. You thought you were being sneaky by extinguishing your exterior lights, eh? It is possible to see LANTIRN guys, who typically fly with their blue-white cockpit lights turned up bright, as much as ten miles away. This fact could make life very unpleasant for our intrepid night fliers.
To solve this problem, you must determine what lights are mission essential and then provide a switch to turn all the others off and on as necessary. Mission-essential lights in the F-16 would probably include the HUD, the REO/SMS (radar and stores management system) in the F-16A, the multifunction display in the C/D, the fire control navigation panel in the A/B, the integrated control panel/data entry display in the C/D, and probably the radar warning receiver and the chaff/flare panel in all models. A few other lights might qualify, but this is fodder for an operational test and evaluation program.
NVGs improve situational awareness tremendously. I'm certain that, if the LANTIRN guys had them, the last two pilots who bought the farm in LANTIRN-related accidents would still be here to discuss the pros and cons of NVGs.
 As I'm writing this piece, I am waiting to go out tonight and fly with one contractor's new integrated NVG helmet. It appears to work very well. With a few minor changes, it would go a long way to properly integrate an NVG device into the cockpit. It is not operational as yet, but I don't think it is necessary to wait for the perfect solution to a problem when you have an effective solution with the clip-on Cat's Eyes at present. If you consider and include all the items I listed above, NVGs work very well. (If you don't, they work poorly or not at all.)
NVGs amplify light in the visible spectrum, with only a small intrusion into the infrared. As we continue into the invisible IR region, we get into FLIR territory and into the second part of my sermon.
Videos from FLIR systems look magical; they appear to turn night into day. This initial impression, however, can be misleading. The marketing video you're seeing was probably recorded on a flight in the Edwards or Nellis area, where the 140-degree daytime temperatures and the incredibly low absolute humidity provide nearly perfect thermal contrast and transmissivity conditions. The same system, under poor conditions of thermal contrast and transmissivity, does not perform nearly as well.
Flying a FLIR-only system for a night-attack mission, you run the risk of encountering many nights when you can't see at all. As a result, you are forced to fly minimum enroute altitudes, won't find any of the bad guys, and risk getting your a-- shot off (or hitting the ground) in the process.
What I said is true of NVGs as well. On some nights, NVGs are just so much excess baggage. You really need both parts of the spectrum available at the same time if you want to be a true round-the-clock attack jet. In other words, you need a fixed FLIR on the HUD and some sort of NVG. Similarly, head-steered FLIRs, which can be superb in their own right, need as a minimum some sort of low-light-level device on the HUD. The two-turret head-steered systems are better yet. One turret has a two-field-of-view FLIR. The other incorporates some sort of low-light-level TV sensor.
Some really forward lookers and forward thinkers are working on systems that fuse information from the two types of devices. Put simply, an algorithm makes a pixel-by-pixel analysis of pictures from both devices and produces a single image that contains the best information from both parts of the spectrum. I am not talking concepts here (they're cheap). Although the system is not operational by any means, I have seen the basic principle in operation. One contractor's efforts with a fused infrared/electro-optical or infrared/low-light level-TV images are quite remarkable. The fused image was superior to an independent picture from either of the two sensors. This approach makes both parts of the spectrum available all the time. It also greatly simplifies the helmet-mounted display since it displays a single image on the helmet.
Make no mistake. Even with this device, there will still be nights when I should stay at home. The reason has to do with the physics behind the sensors. Those making the decisions for this equipment should try better to understand these fundamental characteristics.
What I've said here is vital if we are going to add new capabilities and to improve existing ones. Everyone likes to play in the technological sandbox. But this predilection should not overshadow what's in the best interest of those who will eventually use the products of our technofun, the operators. We must provide them with the best possible weapon system that we can.
End of sermon.
Check Six.
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