I can say without a doubt, flying a helicopter while using Night Vision Goggles (NVGs) is exciting, exhilarating, frightening, terrifying, difficult, challenging and some of the most fun I have ever had all rolled up into one mish-mash of feelings. First a bit of technical background again, as without this information the majority of my comments will not make a great deal of sense. The NVGs we flew with amplified available light 3000 to 4000 times, which is pretty cool. You could go outside on a starry night and turn them on and see all kinds of things that you just couldn't see under normal conditions. You didn't give away the fact that you were there to the enemy, which was a big deal. (Ask the Iraqi army after Desert Storm).
I was first introduced to NVG technology in basic training in 1978 with the "Starlight Scope". This was a rifle mounted scope that was huge (nearly half the weight of an M16 and the view in its display was incredibly difficult to make out any details. It was a demonstration only and I never saw anything like it again until my NVG training.
The goggles we used in this training we modified goggles that had been designed for the infantry. AN/PVS-5 was their designation. The original design was known as a full face goggles. They fit your face very similar to the "Virtual Reality" headgear you see today and you had no vision except out the goggles. It was quickly determined that this was unsuitable for aviation. You had no ability to see inside the cockpit wearing goggles to operate the aircraft. Two pilots were needed, one pilot with goggles and one without them, and this also turned out to be an unsuitable combination. The results of these attempts prompted the "Cutaway design".
Three quarters of the goggle mounting chassis were discarded as well as a foam cushion to pad where the goggle frame met your face. The battery holder and switch were moved to the top (only real remaining part of the goggle chassis) and the frame then fastened to the front edge of your flight helmet. This allowed you to see the instrument panel and view your maps and allowed limited peripheral vision which was deemed necessary during testing to help avoid spatial disorientation. This was important as disorientation lead to crashes. We now had an infantry tool that has been modified for aviation use and we strapped it to our helmets. Did I mention this apparatus is about 6 inches long and weighed a pound and a half? To help balance this out you, had a weight bag Velcroed to the back of your helmet adding another pound or so to your helmet load. This lead to hot spot pain points where your helmet pressed against your scalp and a lot of neck fatigue too.
Now that you have an idea of the physical constraints of the goggles, let’s talk about limitations, because those goggle had plenty of limitations. Here is a list:
- Limited field of view (40 degrees)
- Mono-color (EVERYTHING was GREEN)
- Low visual acuity (Best possible vision was 20/50)
- No depth perception
- Short battery life (Maybe 90 minutes)
- Quality (Each had been massively individually customized to be used in aviation)
- Expensive
- Hard to maintain
- Affected by lights in the environment
Now you also need to remember that since we were in training and not a front line combat unit, we had older, "Well Used" equipment. (This stuff was very expensive.)Well used is a good term for nearly worn out and close to end of the useful life equipment. It worked, that was the main thing. How well they worked varied wildly.
Taking all this into consideration, this is what it meant to the pilots. The 40-degree field of view is best understood by taking a pair of toilet paper tubes using them like binoculars they way you did as a kid. That was roughly the same field of view the you had in these goggles. The single color was green. The images you saw in the NVGs were all shades of green as that was the color emitted by the display. The main issue was that color helps distinguish details and with limited detail, is just made seeing harder. Low visual acuity just meant that they did not focus to a crisp and clear image you would see @ 20/20 acuity. For example, if you had a newspaper laying in the ground unfolded in dark and you walked up to it using the goggles, you would be able to make out that it was a newspaper. You might be able to make out the title banner across the top if it was in 2-inch-tall font. You could see there was text and photos, but all of that is just a big blur. You would never drive a car with vision like this, but we were going to fly helicopters using that same vision.
No depth perception was the second hardest limitation to deal with flying goggles. Most of us took it for granted and never really thought about it because it was always there, until you strapped on some goggles. Our instructors had learned a lot from experience and we were taught the visual cues to depth perception. I'm not going to go into this in great detail as it could be a story all unto itself and I'm pretty sure you'd fall asleep reading it. Not exciting information, but for us, quite necessary. We had to be able to judge a three-foot hover, visually and under goggles that wasn't always easy. There was no radar altimeter and the altimeter we did have was accurate on a scale less than 50 feet, so the altimeter was not an asset at a hover.
The single battery in these goggle was a high output lithium battery about the size of a stack of 6 quarters. The battery lasted roughly about an hour and were not rechargeable. Since they couldn't be recharged, you always got 1 "used" battery and two "new" batteries. You started with your used battery, We we flew until the used ones were drained to failure as a cost savings device. If this happened while you were flying, you announced "Goggle Failure" and the other pilot took the controls while you changed the battery in the dark, by feel.
The other limitation of these goggles was how they were affected by lights. Car headlights and brake lights, street lights and aircraft interior lights. We were using Vietnam era helicopters and these had been equipped with red cockpit lighting very similar to the red dash lights in a Pontiac Firebird. The problem was, red is the absolute worst light in the color spectrum for NVGs, as they function in the "Near Infrared" spectrum of light. Red light caused the goggles to shut down due to overload. A simple red LED light would shut down these goggles. So, all the instrument and console lights in the cockpit were turned OFF because they were red. The warning lights were also red and to mitigate this they had a NVG filter that was put into place for NVG flights, as you could not fly without these warning indicators. To see inside the cockpit, each pilot had a "lip light" mounted on their microphone boom of the helmet and a finger light on one index finger. These used a pale blue LED light that did not affect the NVGs but allowed you to look at the instrument panel and the center console to tune radios, read maps and check gauges and instruments. The helicopter was also equipped with an Infra-red (IR) searchlight that could be used to help you in a really dark spot (and unless your enemy had NVGs too), would not give away your location to the opposing force.
Now, with all this information, we flew around in the dark and saw if we can avoid killing ourselves. NVG training started out just like the Huey transition as with the same maneuvers, except we were doing them at night and wearing the NVGs. That sounds simple enough, but it wasn’t. Learning to fly without depth perception is a lot of hard work. You really had to use your brain a lot more to do the things you had developed as almost second nature. The 3-foot hover in daylight was a piece of cake, you did it and didn't have a second thought about it, especially in a helicopter that hovered as easy and steady as a Huey hovered. Under goggles, you had to look at the grass and if you were low enough to make out that there were blades in that sea of green, then you were likely low enough.
Fatigue was your biggest enemy flying goggles. You had to manage your sleep cycle to make sure you got enough rest. In the flight school environment, we were always short on sleep. You really needed to be in good physical shape too as just moving you head around was tiring. You were constantly turning your head left and right to scan an area that you just glanced at with your normal 170-degree field of vision. Remember your helmet gained two and a half pounds of extra weight and some of that is hanging off the front, so your neck got tired too.
My instructor for NVG’s was CW2 Nelms. Mr. Nelms was one of the most skilled instructors I’d ever flown with. He had by far the best control touch I’d seen in a helicopter and he really knew how to make those old UH-1s dance. We were doing basic maneuvers at Longstreet Stage field and I was having a really hard time finding my sweet spot performing a simulated engine failure at altitude. Each time we were approaching the ground during auto-rotation I was misjudging either my height above the ground or airspeed or both. He told me he had the controls after the latest power recovery at the bottom of the maneuver and he started around the traffic pattern again.
Mr. Nelms then demonstrated a perfect precision auto-rotation. A standard auto-rotation is where you glide down to the runway, then pull initial pitch to shallow out your approach and then apply more pitch as cushion and go sliding down the runway. Normally this is a tad hard on the aircraft as the landing skids are aluminum and not really designed for going for a slide on asphalt. Ft. Rucker dealt with this by adding steel skid plates on the landing skids that can be replaced during the maintenance cycle. But what he showed me that night just made me feel inferior.
The airspeed for a standard auto is 70 knots. So you try to hit that airspeed, and kept your rotor rpm in the green (324 RPM) on the rotor tach. Mr. Nelms showed me that by reducing airspeed a touch (he was closer to 62 knots) and maintaining everything else to standard if you were good you could land that helicopter any place you wanted. He chose the numbers on the approach end of lane 2 and started his decent. Our airspeed was a little slow but other than that we were in a “perfect flight envelope” as he was explaining the visual cues he was using to help determine his references he needed to make this maneuver. We got down 100 feet and is waited just a touch longer than I would before he applied initial pitch to flatten the guide path and he also brought the nose up to 5 or 6 degree high instead of the usual 2 degrees. I noticed the rotor RPM started to decay as he added more pitch and ever so deftly set us down with on the numbers stopping our forward movement and touching down at the same exact moment. We landed as lightly as a feather. I’d never seen an auto-rotation done that well in the daylight, so seeing it done that well at night was very impressive. My respect for his pilot skills soared.
Mr. Nelms than said, “Ok, it is your turn.” He did a really good job talking me through how he completed the maneuver and I tried my best to emulate him, with moderate success. It wasn’t nearly as pretty and I had a 150-foot slide, but it was a large improvement from my last attempt and I tried to perfect his technique every chance he gave me until we finished training.In NVG’s we flew either Night 1 or Night 2 training periods. Night 1 was annoying because your training period was 8 PM to Midnight and you had to wait for sunset and then at least another 45 minutes for it to get dark enough to fly. Night 2 was annoying because of a weather effect known as “Advection Fog”. In southern Alabama, as the night continued to cool and the winds blew in from the coast, the moisture laden air tended to condense quickly forming a very dense fog. Flying goggles made observing this fog formation a challenge and it often caused for cancelled flights due to low visibility.
The last of our challenges before graduation was NVG “Nap of the Earth, aka NOE” navigation. To fly NOE in the training area you had to fly specifically approved routes. These routes were flown in the daylight by someone from flight operations at least once a week to ensure that no new obstacles were erected for you to fly into. Before every flight you compared your map to the hazards map in operations to make sure you had the most current information. You learned pretty quickly how fast power lines and radio towers could be erected in rural areas.
These routes were laid out in very rural areas to both take advantage of the natural landscape and to avoid disturbing the populace. (People tend to get annoyed when you fly 50-feet above their houses at 3 AM.) NOE was literally skids in the treetop low. Very low and very slow, essentially hovering above the trees at about 25 knots. It was also very nerve wracking, very tiring and very exciting. The hardest part wasn’t so much flying NOE, it was navigating.
Mr. Nelms knew every tree and rock of the NOE routes and I spent more time with him taking me back to a check-point and saying try again as we followed the routes. It was slow and tedious as being so low it is really hard to make out terrain features, then add the limitations of the NVGs as listed above, and it really became a challenging task.
Apparently Mr. Nelms knew how to teach me as I got my best check-ride score ever on my end of course check-ride. About two weeks later, I had finally earned my prize and was awarded my Warrant Officer One (WO1) bar and my Pilot Wings.
I was first introduced to NVG technology in basic training in 1978 with the "Starlight Scope". This was a rifle mounted scope that was huge (nearly half the weight of an M16 and the view in its display was incredibly difficult to make out any details. It was a demonstration only and I never saw anything like it again until my NVG training.
The goggles we used in this training we modified goggles that had been designed for the infantry. AN/PVS-5 was their designation. The original design was known as a full face goggles. They fit your face very similar to the "Virtual Reality" headgear you see today and you had no vision except out the goggles. It was quickly determined that this was unsuitable for aviation. You had no ability to see inside the cockpit wearing goggles to operate the aircraft. Two pilots were needed, one pilot with goggles and one without them, and this also turned out to be an unsuitable combination. The results of these attempts prompted the "Cutaway design".
Three quarters of the goggle mounting chassis were discarded as well as a foam cushion to pad where the goggle frame met your face. The battery holder and switch were moved to the top (only real remaining part of the goggle chassis) and the frame then fastened to the front edge of your flight helmet. This allowed you to see the instrument panel and view your maps and allowed limited peripheral vision which was deemed necessary during testing to help avoid spatial disorientation. This was important as disorientation lead to crashes. We now had an infantry tool that has been modified for aviation use and we strapped it to our helmets. Did I mention this apparatus is about 6 inches long and weighed a pound and a half? To help balance this out you, had a weight bag Velcroed to the back of your helmet adding another pound or so to your helmet load. This lead to hot spot pain points where your helmet pressed against your scalp and a lot of neck fatigue too.
Now that you have an idea of the physical constraints of the goggles, let’s talk about limitations, because those goggle had plenty of limitations. Here is a list:
- Limited field of view (40 degrees)
- Mono-color (EVERYTHING was GREEN)
- Low visual acuity (Best possible vision was 20/50)
- No depth perception
- Short battery life (Maybe 90 minutes)
- Quality (Each had been massively individually customized to be used in aviation)
- Expensive
- Hard to maintain
- Affected by lights in the environment
Now you also need to remember that since we were in training and not a front line combat unit, we had older, "Well Used" equipment. (This stuff was very expensive.)Well used is a good term for nearly worn out and close to end of the useful life equipment. It worked, that was the main thing. How well they worked varied wildly.
Taking all this into consideration, this is what it meant to the pilots. The 40-degree field of view is best understood by taking a pair of toilet paper tubes using them like binoculars they way you did as a kid. That was roughly the same field of view the you had in these goggles. The single color was green. The images you saw in the NVGs were all shades of green as that was the color emitted by the display. The main issue was that color helps distinguish details and with limited detail, is just made seeing harder. Low visual acuity just meant that they did not focus to a crisp and clear image you would see @ 20/20 acuity. For example, if you had a newspaper laying in the ground unfolded in dark and you walked up to it using the goggles, you would be able to make out that it was a newspaper. You might be able to make out the title banner across the top if it was in 2-inch-tall font. You could see there was text and photos, but all of that is just a big blur. You would never drive a car with vision like this, but we were going to fly helicopters using that same vision.
No depth perception was the second hardest limitation to deal with flying goggles. Most of us took it for granted and never really thought about it because it was always there, until you strapped on some goggles. Our instructors had learned a lot from experience and we were taught the visual cues to depth perception. I'm not going to go into this in great detail as it could be a story all unto itself and I'm pretty sure you'd fall asleep reading it. Not exciting information, but for us, quite necessary. We had to be able to judge a three-foot hover, visually and under goggles that wasn't always easy. There was no radar altimeter and the altimeter we did have was accurate on a scale less than 50 feet, so the altimeter was not an asset at a hover.
The single battery in these goggle was a high output lithium battery about the size of a stack of 6 quarters. The battery lasted roughly about an hour and were not rechargeable. Since they couldn't be recharged, you always got 1 "used" battery and two "new" batteries. You started with your used battery, We we flew until the used ones were drained to failure as a cost savings device. If this happened while you were flying, you announced "Goggle Failure" and the other pilot took the controls while you changed the battery in the dark, by feel.
The other limitation of these goggles was how they were affected by lights. Car headlights and brake lights, street lights and aircraft interior lights. We were using Vietnam era helicopters and these had been equipped with red cockpit lighting very similar to the red dash lights in a Pontiac Firebird. The problem was, red is the absolute worst light in the color spectrum for NVGs, as they function in the "Near Infrared" spectrum of light. Red light caused the goggles to shut down due to overload. A simple red LED light would shut down these goggles. So, all the instrument and console lights in the cockpit were turned OFF because they were red. The warning lights were also red and to mitigate this they had a NVG filter that was put into place for NVG flights, as you could not fly without these warning indicators. To see inside the cockpit, each pilot had a "lip light" mounted on their microphone boom of the helmet and a finger light on one index finger. These used a pale blue LED light that did not affect the NVGs but allowed you to look at the instrument panel and the center console to tune radios, read maps and check gauges and instruments. The helicopter was also equipped with an Infra-red (IR) searchlight that could be used to help you in a really dark spot (and unless your enemy had NVGs too), would not give away your location to the opposing force.
Now, with all this information, we flew around in the dark and saw if we can avoid killing ourselves. NVG training started out just like the Huey transition as with the same maneuvers, except we were doing them at night and wearing the NVGs. That sounds simple enough, but it wasn’t. Learning to fly without depth perception is a lot of hard work. You really had to use your brain a lot more to do the things you had developed as almost second nature. The 3-foot hover in daylight was a piece of cake, you did it and didn't have a second thought about it, especially in a helicopter that hovered as easy and steady as a Huey hovered. Under goggles, you had to look at the grass and if you were low enough to make out that there were blades in that sea of green, then you were likely low enough.
Fatigue was your biggest enemy flying goggles. You had to manage your sleep cycle to make sure you got enough rest. In the flight school environment, we were always short on sleep. You really needed to be in good physical shape too as just moving you head around was tiring. You were constantly turning your head left and right to scan an area that you just glanced at with your normal 170-degree field of vision. Remember your helmet gained two and a half pounds of extra weight and some of that is hanging off the front, so your neck got tired too.
My instructor for NVG’s was CW2 Nelms. Mr. Nelms was one of the most skilled instructors I’d ever flown with. He had by far the best control touch I’d seen in a helicopter and he really knew how to make those old UH-1s dance. We were doing basic maneuvers at Longstreet Stage field and I was having a really hard time finding my sweet spot performing a simulated engine failure at altitude. Each time we were approaching the ground during auto-rotation I was misjudging either my height above the ground or airspeed or both. He told me he had the controls after the latest power recovery at the bottom of the maneuver and he started around the traffic pattern again.
Mr. Nelms then demonstrated a perfect precision auto-rotation. A standard auto-rotation is where you glide down to the runway, then pull initial pitch to shallow out your approach and then apply more pitch as cushion and go sliding down the runway. Normally this is a tad hard on the aircraft as the landing skids are aluminum and not really designed for going for a slide on asphalt. Ft. Rucker dealt with this by adding steel skid plates on the landing skids that can be replaced during the maintenance cycle. But what he showed me that night just made me feel inferior.
The airspeed for a standard auto is 70 knots. So you try to hit that airspeed, and kept your rotor rpm in the green (324 RPM) on the rotor tach. Mr. Nelms showed me that by reducing airspeed a touch (he was closer to 62 knots) and maintaining everything else to standard if you were good you could land that helicopter any place you wanted. He chose the numbers on the approach end of lane 2 and started his decent. Our airspeed was a little slow but other than that we were in a “perfect flight envelope” as he was explaining the visual cues he was using to help determine his references he needed to make this maneuver. We got down 100 feet and is waited just a touch longer than I would before he applied initial pitch to flatten the guide path and he also brought the nose up to 5 or 6 degree high instead of the usual 2 degrees. I noticed the rotor RPM started to decay as he added more pitch and ever so deftly set us down with on the numbers stopping our forward movement and touching down at the same exact moment. We landed as lightly as a feather. I’d never seen an auto-rotation done that well in the daylight, so seeing it done that well at night was very impressive. My respect for his pilot skills soared.
Mr. Nelms than said, “Ok, it is your turn.” He did a really good job talking me through how he completed the maneuver and I tried my best to emulate him, with moderate success. It wasn’t nearly as pretty and I had a 150-foot slide, but it was a large improvement from my last attempt and I tried to perfect his technique every chance he gave me until we finished training.In NVG’s we flew either Night 1 or Night 2 training periods. Night 1 was annoying because your training period was 8 PM to Midnight and you had to wait for sunset and then at least another 45 minutes for it to get dark enough to fly. Night 2 was annoying because of a weather effect known as “Advection Fog”. In southern Alabama, as the night continued to cool and the winds blew in from the coast, the moisture laden air tended to condense quickly forming a very dense fog. Flying goggles made observing this fog formation a challenge and it often caused for cancelled flights due to low visibility.
The last of our challenges before graduation was NVG “Nap of the Earth, aka NOE” navigation. To fly NOE in the training area you had to fly specifically approved routes. These routes were flown in the daylight by someone from flight operations at least once a week to ensure that no new obstacles were erected for you to fly into. Before every flight you compared your map to the hazards map in operations to make sure you had the most current information. You learned pretty quickly how fast power lines and radio towers could be erected in rural areas.
These routes were laid out in very rural areas to both take advantage of the natural landscape and to avoid disturbing the populace. (People tend to get annoyed when you fly 50-feet above their houses at 3 AM.) NOE was literally skids in the treetop low. Very low and very slow, essentially hovering above the trees at about 25 knots. It was also very nerve wracking, very tiring and very exciting. The hardest part wasn’t so much flying NOE, it was navigating.
Mr. Nelms knew every tree and rock of the NOE routes and I spent more time with him taking me back to a check-point and saying try again as we followed the routes. It was slow and tedious as being so low it is really hard to make out terrain features, then add the limitations of the NVGs as listed above, and it really became a challenging task.
Apparently Mr. Nelms knew how to teach me as I got my best check-ride score ever on my end of course check-ride. About two weeks later, I had finally earned my prize and was awarded my Warrant Officer One (WO1) bar and my Pilot Wings.
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