Night vision

Night vision is a perennial problem for pilots.

Nature did not design us for night operations. Our eyeballs are too small, our pupils too narrow, and the rods in our eyes that allow us to see in the dark are located 20° off center.

That is why to scan for traffic at night, we must use our peripheral vision.

Turns out sailors as far back as Aristotle’s ancient Greece have known they needed to use their peripheral vision for night navigation. Our eyes can adapt to the dark in as little as four seconds, but only if exposed to complete, uninterrupted darkness. It takes another 30 minutes to achieve 80% vision in the dark.

[contextly_auto_sidebar]Whether we achieve full vision depends on our cardiovascular condition and general health. High blood pressure, clogged arteries, low stamina, and retinal disease all affect how well our eyes function at night.

All in all, adapting to the dark is an elaborate and delicate physiological process. Any exposure to light requires starting the entire process again.

That’s what tripped up a Cessna P-210 pilot. After landing at an unfamiliar airport, the pilot missed the first available runway exit.

In his report to NASA’s Aviation Safety Reporting System, he wrote that the airport controller dispatched the airport police to guide him to the ramp.

“The police vehicle had its overhead light bar on with red, blue and white lights. I informed the Tower that the light bar was blinding me, but the controller said the officer needed to have it on.”

The police lights destroyed the pilot’s night vision. Without alternative, indirect lighting to guide him, the pilot was rendered temporarily night blind.

He missed a turn and taxied his plane off the pavement and into the grass.

Fortunately, neither airport property nor the plane was damaged.

“I believe that this occurrence could have been totally avoided if the police officer had just shut off his light bar,” the pilot concluded in his NASA report.

The policy mandating that the police officer keep his light bar on when moving on airport property was put into effect in the interest of safety. It is a requirement common to every airport where I’ve flown.

Yet a pilot robbed of night vision while taxiing becomes a safety hazard to ground personnel and property. Instead of taxiing onto the grass, the P-210 pilot could have driven into the back of the police vehicle.

Had the officer used a dimmer light setting, his vehicle still would have been clearly visible both to the pilot and airport personnel.

In another case, a turboprop flight crew filed a NASA report after an assault on their night vision occurred at a de-icing station.

“While de-icing at Coastal Carolina Regional Airport (KEWN) in North Carolina, the ground crew marshals you into a dedicated de-icing area northeast of Runway 22. Either the company or the airport has installed a giant 1,000-watt halogen light AT GROUND LEVEL that blasts the flight crew with blinding light so bad that you cannot even see the marshal. This is a major safety issue in several ways…”

The de-icing crew turned off the light after the flight crew complained about the light blinding them and making it impossible to see the marshal. The de-icing crew informed the flight crew it was local procedure to use that light during de-icing operations.

Blinded by the halogen light, the turboprop flight crew could have run over the marshal, or taxied a propeller into him or the de-icing truck.

Mounting the de-icing light at a low level could be for the benefit of the de-icing crew. It’s likely positioned at an average wing-level height to help the de-icing folks better see the accuracy of their work.

It seems, however, that whoever put up that light did not seek input from pilots, or at least take into consideration the effect the light’s position would have on them.

Both reports highlight the importance of night vision education for all airport personnel.

Until the subject of night vision becomes part of employee training, airport personnel will unwittingly continue to create dangerous situations where they think they are acting in the pilot’s best interest.

Exposure to a single source of light is not the only potential threat to night vision. Light pollution from street lights, traffic lights, billboards, and office buildings can make an airport indistinguishable from a nearby city.

Such was the case for a pilot on approach in Miami airspace one night. Light pollution prevented him from making out his destination airport, KMIA. So he requested the localizer approach. The controller denied and gave him the visual and advised the pilot to call the field when able.

“It was a very clear night and the bright city light pollution made the airport indistinguishable from the city lights. From 15 to 20 miles out, I was repeatedly told to report the field in sight and I repeatedly told ATC that I did not have it.”

The controller became increasingly frustrated, as did the pilot. Only after the pilot responded for the third time that he did not have the field was he vectored around for the localizer approach.

And it’s not just the big cities that burn bright.

A GA pilot flying into Athens/Ben Epps Airport (KAHN) in Georgia reported overflying the airport because light pollution around the airport obscured it and its rotating beacon.

“From 20 miles to 15 miles to overflying the airport from the west to the east, I never saw the rotating beacon,” he wrote. “Not having flown into KAHN very often at night, I was trying to locate the beacon visually, while transitioning from the GPS system to outside of the cockpit, and as I was trying to locate the beacon, I lost sight of the airport as depicted on the GPS.”

Two miles past the airport, ATC asked the pilot if he was aware he’d overflown the airport. The pilot had to use his GPS for situational awareness. He eventually found the airfield and landed without incident.

In his conclusion, he wrote, “I have spoken to two other pilots and a flight instructor who regularly fly into KAHN at night, and they confirmed and affirmed the trouble I had finding the beacon, let alone the airport.”

Another pilot complained about the light pollution coming from a golf course driving range near Watsonville Municipal Airport (KWVI) in California. The plane was on instrument approach.

“As we approached the published minimums and were just about to execute a missed approach, my second-in-command called out: “Runway in sight, 11 o’clock, go visual.” The problem is that we were both staring at the extremely bright golf course driving range lights just a few hundred yards south of the runway threshold and did not actually have the runway lights in sight.”

Before they commenced their approach to KWVI, the crew briefed the possibility of the golf range lights interfering with their ability to see the airport’s approach lights. They knew the potential for mistaking golf course range lights for runway lights. Yet it still caught both pilots by surprise. Had they not course corrected, they would have ended up in a grove of Eucalyptus trees.

Some communities have replaced municipal lighting that shines in all directions with lights that only illuminate downward, toward the ground. Ironically, the communities that have replaced lights did so to preserve the night habitats of nocturnal birds, bugs, and animals.

Maybe we could convince communities surrounding our airports that night-flying pilots are an endangered species worth preserving. Maybe that would motivate them to rid the night sky of light pollution, and help the environment, too.

Ultimately, we are responsible to ourselves for keeping what little night vision Nature gave us.

For all pilots, maintaining good cardiovascular health may be the best method available.

For instrument-rated pilots, treat every night flight as a flight in instrument meteorological conditions. Using navigational aids and shooting an instrument approach are two great ways to stay situationally aware.

I also encourage all pilots to wear sunglasses at night until airborne. That may seem extreme, but it’s not the most unusual action a pilot has taken to preserve night vision. A Piper Mirage pilot may own that distinction.

“I was parked in transient parking facing a Cessna 400, across the taxiway. I started up my airplane to fly to home base. After getting the engine running and going through part of my start-up procedures, I realized that one of the cabin lights behind me in the plane was on. At night these lights create nontrivial light pollution in the cabin, so I wanted to turn it off. I put on the parking brake and went back to the cabin to turn the light off.”

As he made his way toward the objectionable light, his passenger screamed that the airplane was moving. The pilot raced back to his seat, but not before the plane had sliced into the fuselage of the Cessna 400 parked opposite him.