Tuesday, September 1, 2009
NVGs Made Simple
If you ask pilots about Night Vision Goggles (NVGs), you will normally get one of two responses: I wouldn’t fly at night without them or I have no interest in flying with them, period! Perhaps you are undecided about whether NVGs fit into your program.
Night vision goggles, NVGs or simply "goggles," certainly have their share of controversy, but not if you speak to the pilots that routinely fly with them. If you are currently undecided, please read on, and hopefully after our visit you will have a better appreciation of where the technology, resources and regulatory process resides today.
A discussion about night vision goggles would not be complete without first understanding the limitations of the human eye. The eye has many components, the pupil, iris, cornea, retina, optic nerve and other factory-installed components that all work together creating an interpretation by the brain we understand as vision. Focusing on night vision requires a look at the receptor cells, called rods and cones, located in the retina. These cells absorb and process the visible light that enters the eye.
According to the American Optometric Association, "the dual receptor system of rods and cones allows the human eye to maintain sensitivity over an impressively large range of ambient light levels." Rods control dark adaptation and cones provide more refined detail and show color resolution. To get the best night vision it can take upwards of 30 minutes to allow the photo pigment chemical rhodopsin (also known as visual purple), to take shape in the rods and provide the benefits of illumination and adaptation in darkness. Once the adaptation is complete, it can be quickly reset if you are exposed to bright light. If you have ever exited a movie theater into daylight, or had a cop shine his flashlight directly into your eyes at a drive-in theater, well the reaction is the same — you lose your night vision, and may not be able to see anything until the light and photo pigments return to equilibrium.
Another key component on the anterior wall of the eye is the fovea. The reason it’s worth mentioning is that during reduced visible light, there is a central blind spot. This occurs because of the concentration of cones in the center of the fovea. This phenomenon can also be called the night blind spot. To eliminate this, one must look 15 – 20 degrees above, below or to the side of the object to engage the rods. To defeat this limitation one can be trained to use the proper scanning procedures. Knowing the limitations of human eye can greatly prepare pilots to overcome night vision design flaws.
Just in case you were wondering how animals get around so well at night without goggles, many animals are manufactured with an extra layer of tissue in the anterior wall called a tapetum lucidum. This tissue reflects the incoming light, increasing the light level for the photoreceptors and creating "eyeshine." We have all seen a dog, deer or maybe a larger (hungry) critter’s eyes glowing at us in the night hours. This is a result of the tapetum lucidum.
Since the human eye was not designed to see in the dark as well as animals, especially nocturnal ones, we rely on strategies and technology to get the most effective vision. (Hopefully your drive-in theater date didn’t have eyes that "eyeshined" back into that flashlight.)
Evolution of Goggles
Night vision technology dates back to the 1950s and is based on photocell imagery of electromagnetic radiation. Initially created for the infantry, it was adapted for aviation use by the helicopter community. I received my introduction to NVGs while attending flight school in the U.S. Army (Purple Flight 83-11) during the Aeroscout phase of training.
At the time, it wouldn’t have mattered if there was any controversy or mixed feelings about NVG flying, since if the Army would have wanted you to have feelings, they would have issued them, and the Army removed mine, along with my wisdom teeth. I would relate flying a helicopter with these early AN/PVS-4 goggles to flying a helicopter with a large cardboard refrigerator box over my head. Even worse was having to fly NVGs during the day with "day filters" installed at the end of the tubes, with an unaided safety pilot. It was like staring into a murky green swimming pool!
Amazed by the ability of NVGs to amplify ambient light, and eventually transitioning to "cut-away" goggles, we forged an uneasy, if not resilient relationship that would outlive a couple marriages, three services and a multitude of different aircraft.
In the Army we were able to fly night, low-level, contour and nap-of-the-earth (NOE), in familiar and unfamiliar terrain. In early night vision goggles, the power supply all hinged on just one battery. A battery that might fail without warning, and had the minor issue of overheating and exploding.
If I experienced goggle failure while in a hover, the technique called for the pilot to smoothly lower the collective and apply some forward cyclic until locating the ground, and the motion stopped, kind of like my last Boeing 767 landing in Hong Kong. Since the goggle assemblies were designed for use by ground troops, they were adapted to attach to our flight helmets with Velcro, metal snaps and surgical tubing. When properly installed, the "full face" would completely cover our eyes, eliminating all prospects of peripheral vision. Did you know that much of our vision is peripheral?
Then there was the issue of visual acuity and goggle focus. NVG pilots had to either "fly the blurs" in order to read the flight instruments, or reach up and focus one of the goggle tubes out of the infinity position to see the gauges. To offset the weight of the goggles on the front of the helmet, pilots would fashion their own counterweights derived from Velcro-covered pouches or even metal bandage boxes, filled with lead fishing weights. Since none of the aircraft lighting was compatible, the crew chiefs would cover interior lighting with cardboard and 100 mph tape, using chem sticks to illuminate the cockpit.
Even so, the goggles required some illumination to provide adequate resolution of the terrain. Yet, in an urban setting or area of heavy illumination, the goggles tubes would shut down. It was almost impossible to see "wires" contributing to the mounting number of NVG accidents in that time. While not easy to use or particularly comfortable, we all quickly adapted and learned to work within the limitations of the NVG equipment of that era. Tremendous credit goes to the early pioneers of who developed these goggles for aviation use and created the early training programs that evolved into what we enjoy today (see related story on NVG training on page 48). I mention this history because much has changed since then, and if you’ve only heard the war stories, you are truly missing out. As I mentioned, the "full face" NVGs eventually gave way to "cut-aways," which restored unaided peripheral vision in addition to allowing the NVG pilots to tilt their head to scan the instruments or recover from an NVG failure. The AN/PVS-4 gave way to AN/PVS-5, providing lighter, more capable goggles.
Helmets and mounting brackets became standardized with clip on, swing away NVG mounts, connected to switchable, non-exploding dual battery packs, lasting 80 – 100 hours today. Aircraft lighting was vastly improved both in the cockpit and along the aircraft’s exterior. The advent of adjustable intensity "slime lights" made NVG formation much easier. The latest generations of AVS-9/4949 and NIVISYS NVAG-6 are extremely capable, robust devices, resulting from decades of experience and improvements.
During my tenure in the Air National Guard, we flew HH-60 NVGs single ship, two ship formation and during in-flight refueling. I also flew the HC-130 on NVGs and found the same principles of helicopter NVG flying worked equally as well. We flew both training and tactical missions over water, desert, urban and mountainous terrain, and everything in between. I’ve flown NVG chase to HMX-1 carrying more than one U.S. President and a visiting Pope, all in urban areas without experiencing any of the goggle tubes shutting down as in earlier models.
We transitioned between instrument and NVG flight with much precision. Oddly, during a long oceanic rescue mission, we were asked not to refuel at night. But if we did, the preference was for the crew not to use the NVGs. Fortunately, we had all brought NVGs with us, and chose to wear them since we were far more comfortable flying at night with NVGs, especially mid-air refueling, than flying unaided. Although we had several other great contributors on this 15-hour mission, the NVGs really helped save our bacon that December night in the North Atlantic.
I had the opportunity to attend a night vision goggle training session at Bell Helicopter at the invitation of Capt. Scott Baxter, assistant chief flight instructor. Baxter is a former Army (Royal Blue Flight 85-31) OH-58D pilot, and a current Bell Helicopter production test pilot. He started the first FAR 141 NVG training program, which created the first FAA accredited NVG training curriculum.
For the first time, pilots could participate in a standardized night vision goggle training program, producing a durable, industry-wide, recognized standard with FAA’s accreditation. This qualification as an NVG pilot is recognized wherever you operate. As a NVG pioneer, Baxter has been eager to share his hard work with anyone that is interested in starting a FAR 141 NVG school of their own, and promoting the safe and professional use of night vision goggles.
Baxter’s student that evening was Capt. Rick Fletcher, who was attending the NVG instructor pilot course. This is a week-long curriculum and I was joining them on the third night. Fletcher is also a former Army aviator (Maroon Flight 76-11) with a diverse flying background with the military, airline, government and manufacturing. He has experience with both night vision goggles and forward looking infrared (FLIR) night vision systems from his tenure as an AH-64 Apache pilot.
Today, Fletcher is a factory pilot for AgustaWestland helicopters. With more than 600 hours of NVG time, he was both experienced and discerning as an instructor student. Now, you might think this is easier because of Fletcher’s experience, but it takes the same level of dedication and professionalism regardless of experience and occasionally even more to avoid negative habit transfer and adapt to new skills and standards.
After a through briefing and roundtable discussion, we boarded one of Bell’s B206B training aircraft, and goggled up using 4949’s. Aside from the NVG panel, the helicopter was equipped with air conditioning, making this training flight very comfortable, even in the Texas heat.
Observing Baxter conduct his lesson was amazing; like watching a skilled surgeon at a teaching hospital. Fletcher demonstrated several maneuvers and then instructed Baxter (in the role of student) in these same maneuvers.
Normal approaches, steep approaches, confined areas, out of ground effect hovering, slope landings and emergency procedures were all part of the syllabus that evening. I was very impressed by the organization of the syllabus and the quality of the equipment and instruction. If you investigate this method of training, you will not be disappointed, and you will have a blast!
NVG NRPM Part 61
The FAA recognizes the significant role that NVGs are having in civil aviation, and submitted proposed changes (NRPM) to FAR Part 61 on Feb. 7, 2007. The FAA acknowledges the significant improvements in NVG equipment, improved ease of use, and lower acquisition costs of NVG equipment. Under FAR 61.31(k) and 61.195(k), NVG training and qualifications are delineated for pilots and flight instructors for the first time. Visit FAA’s website — www.faa.gov — and look for the publication of the final rule, expected later this year.
U.S. Air Force ANG 101st Rescue Squadron (RQS)
I met with Maj. Rodney Lisec, chief of flight standards, aircrew standardization and evaluation for the squadron. Maj. Lisec is an instructor/evaluator pilot, flying NVGs for about 15 years, with over 800 hours of NVG experience, operating primarily in HH-60L helicopters as a special operations and combat search and rescue pilot. Lisec told me it takes about 10 hours to get comfortable flying with NVGs and about 100 hours to become seasoned in their many complex mission profiles as a NVG pilot. He explained that the Air Force doesn’t fly much during the day. Most training and missions are flown using NVGs at night, and most of his pilots would not feel comfortable flying at night without them. The HH-60L has all NVG compatible interior and exterior lighting. This aircraft is also equipped with a "heads down" display with a FLIR, adding another dimension in night vision.
U.S. Army Air Ambulance Detachment, NTC-Fort Irwin
To see how much progress NVGs have made since I departed the U.S. Army, I visited with U.S. Army Capt. Josh Thompson. Capt. Thompson is a medevac pilot assigned to the air ambulance detachment at the U.S. Army’s National Training Center at Fort Irwin, Calif. He is currently flying the military version of the Eurocopter EC-135, also known as the Lakota, and has considerable experience flying the UH-60 Blackhawk.
After discussing my Army goggle history with him, he chuckled and told me the Army has come a long way since then. Thompson told me "NVGs are essential to the medevac mission."
"The areas we operate in the California desert are terrain-challenged and dark. Brown-out landings are not uncommon. While most Army NVG operators have moon illumination restrictions of 23 percent illumination and 30 degrees moon angle to the horizon, medevac pilots are exempt. The glass panel displays of the Lakota are great for night vision goggle operations, providing great acuity of the instruments without compromising the sensitivities of the NVGs."
While this makes it easy to transition between NVG and instrument flight, Capt. Thompson reports this is not nearly as functional as the heads up display (HUD) image that was part of the Blackhawk NVG package. "Once you get used to flying the NVGs with the HUD, it’s hard to go back," Thompson said.
If there was one thing he would change, it would be the size of the cockpit area he said. At 6 feet 4 inches tall, the extra room to maneuver the helmet with the goggles on can be challenging.
U.S. Customs & Border Protection, Office of Air & Marine (CBP OAM)
Recently I had the opportunity to meet with Supervisory Air Interdiction Agent Tim Bagot assigned to CBP headquarters in Washington, D.C. and discuss CBP’s night vision goggle program. If you don’t know Tim Bagot, he’s a "pilot’s pilot" who’s been flying NVGs for more than 20 years, and just about every type of aircraft imaginable. Bagot has flown in combat, for two airlines and is a veteran of the early U.S. Customs Drug Air War.
Today, CBP operates almost 300 aircraft, performing missions around the clock in urban, desert, mountainous and maritime environments.
"We view the use of night vision goggles as both risk mitigation and a mission execution enhancement tool. NVGs enable us to perform law enforcement operations far more safely in environments where flying without them would severely limit our ability to successfully perform our mission," Bagot said.
CBP OAM possesses hundreds of Mil-Spec ITT 4949 Gen III NVGs, and is in the process of upgrading to Pinnacle image intensifier tubes. "Training depends on the experience of the crewmember," Bagot explained. "Agents who have no experience flying with NVGs are required, at a minimum, to complete a 10 qualification syllabus, where as experienced pilots only require a transition."
CBP also operates single-pilot NVG missions with pilots possessing more than 50 NVG hours in type, who have flown more than 10 NVG house in the past six months and three hours in the previous 30 days. However, in order to engage in an enforcement action, two qualified NVG crewmembers must be on board.
USCG Air Station Miami: "Busiest Air Sea Rescue Unit in the World"
Miami is an amazing place, and so is Coast Guard Air Station Miami. "Often a law enforcement mission turns into a SAR case," according to Cmdr. Don Taylor, operations officer at Miami Coast Guard Air Station. Within Coast Guard Aviation, Miami has always been innovative in the use of technology to accomplish their mission. Cmdr. Taylor told me they really enjoy the benefits of using goggles, and jokingly wonders how they got by before them. Today, the Coast Guard is 100 percent goggle flying in their helicopters and moving in the same direction in fixed-wing aircraft. The Coast Guard is also transitioning to HUD displays, increasing situational awareness and mission success.
Once reserved strictly for the military, there are a host of training and repair facilities, equipment manufactures and FAA support to help you get started. With many helicopter accidents occurring at night due to controlled flight into terrain (CFIT), a business case can be made for a night vision goggle program in your company. If you are currently flying NVGs for the military or law enforcement, new equipment, techniques and applications continue to move forward, enabling new missions, increased safety and ownership of the night. So, if you’ve been thinking about starting a night vision goggle program, or getting back into goggles after not flying with them for a while, now is a great time to get started.
NVG Terminology Explained
There are many terms floating around the industry as to what type of NVGs should be purchased.
Mil-Spec – This term means the NVGs meet the same stringent criteria established by the military for purchasing NVGs. Mil-Spec NVGs can withstand reasonable exposure to the elements and a wide variety of operational conditions and continue to deliver reliable performance. So, assuming you maintain your NVGs in accordance with the FAA’s specifications, you can wear your goggles in a wide variety of temperatures, altitudes, hot and damp environments. Most goggles manufactured today meet the Mil-Spec requirements.
NVG Repair – There are several certified FAA Part 145 service centers that can repair, maintain and perform 180-day airworthiness inspections on NVGs and their subcomponents as specified in RTCA/DO-275. For small or medium size organizations that may not have the technical staff or equipment, these Part 145 repair stations can provide a turnkey cost advantage.
TSO – Technical Service Order issued by the FAA Administrator for parts, processes and appliances used on civil aircraft. NIVISYS currently has the only TSO-approved night vision goggle, under TSO-164, the NVAG-6. This goggle is certified and produced for civilian use in civilian aircraft.
Class A, Class B, Class C – These classes have to do with the type of coating or "filter" that is applied to the NVGs in the manufacturing process. The objective of these filters is to block certain frequencies of light, allowing for the illumination of cockpit instrumentation that would not affect the performance of the NVG. As cockpit lighting and instrumentation evolved beyond blue-green flood lighting and chem sticks to flat panel displays, Class A filters gave way to Class B filters. With the proliferation of HUDs, modified Class B filters and Class C filters became popular. Class B filters are the most common filters in use today.
Goggle Generations 0, I, II, III, IV – Like the Sham-wow and David Hasselhoff CDs, the Generation 0 NVGs were a product of WWII German engineering and not available in any store at any price. Generation I NVGs, such as the Starlight scope, were used during the Vietnam War by ground forces. The lines get a little blurry between Generation II, Generation III and Generation IV NVGs, depending on models and modifications. However, it was with Generation II that NVGs took to the skies with AN/PVS4 and the later AN/PVS5. As the goggle manufacturers evolved from earlier generations of goggles, the eyepiece was increased from 18mm to 25mm, enabling the goggle user to see more with less ambient light, and wear the goggles further away from the eye. This was great for pilots that wear glasses and a lot more comfortable for pilots who don’t. Today, most NVGs are designated as Generation III or III+.
Top 10 Reasons to Consider NVGs
10. You will see what you are currently missing.
09. It will enhance your ability to see and avoid potentially hazardous obstacles.
08. Provides greater access to locations unreachable flying unaided at night.
07. Can prevent accidents resulting from CFIT.
06. Most new-delivery aircraft are equipped for NVG operations.
05. Several FAR 141 schools to choose from, making it easier than you think.
04. Pending NRPM mandating NVG use for night helicopter operations.
03. New TSO’d goggles are now available.
02. Today’s NVGs work well in both urban and rural environments.
01. Tremendous increase in safety.