Glass Cockpits and Polarized Sunglasses

Polarized sunglasses are wonderful on the water, on the road and on the ski slope. They cut glare so well that many pilots assume they must be the best choice for the cockpit too. For flying, and especially for flying behind a glass cockpit, they usually aren't.

Both the FAA and the UK Civil Aviation Authority advise pilots against polarized lenses. This post explains why, what happens when polarized lenses meet the screens in a modern cockpit, and what to wear instead.

The Quick Answer

• The FAA says: "Polarized lenses are not recommended for use in the aviation environment."
• The main reasons: polarized lenses can dim or black out some cockpit displays, show distortion patterns in windscreens, and hide the flash of sunlight off other aircraft that helps you spot traffic.
• The better choice: high-quality non-polarized lenses with a neutral tint, which block 70 to 85% of visible light.

Hear It From the FAA

In this short Pilot Minute video, Federal Air Surgeon Dr. Susan Northrup covers the aeromedical and safety considerations for choosing sunglasses to fly with.

How Polarized Lenses Work

Sunlight travels as waves that vibrate in every direction. When that light bounces off a flat surface like water, a wet road or the hood of a car, much of the reflected light ends up vibrating in one direction: horizontally. That concentrated horizontal light is what we see as glare.

A polarized lens contains a filter that works a bit like a set of very fine vertical slots. It lets vertically vibrating light through and blocks most of the horizontal light. The result is a dramatic cut in glare from horizontal surfaces, which is why polarized lenses are so popular for fishing, boating and driving.

The problem is that the filter doesn't know the difference between glare you want to block and light you need to see. In a cockpit, some of the most important light is polarized too.

What Happens With a Glass Cockpit

Most modern cockpits use LCD screens: primary flight displays, multifunction displays, engine monitors and the panel-mount and portable GPS units and tablets many pilots fly with. LCD screens work by controlling polarized light, so the light coming out of many of them is already polarized.

When you look at one of those screens through polarized lenses, the two filters interact. Depending on the display and the angle of your head, you may see:

• The screen dim noticeably.
• Uneven or patchy brightness across the display.
• Color shifts or rainbow-like patterns.
• The screen go almost completely black when you tilt your head.

The UK CAA notes that polarized lenses "can reduce the conspicuity of some LCD displays." The FAA's brochure Sunglasses for Pilots warns that polarization "can reduce or eliminate the visibility of instruments that incorporate anti-glare filters."

How strong the effect is varies a great deal from one display to the next. Some screens look almost normal through polarized lenses, while others black out. That inconsistency is part of the problem. A screen that looks fine in straight-and-level flight can disappear as you bank or turn your head to scan for traffic, which is exactly when you need it.

You can see this for yourself on the ground. Put on a pair of polarized sunglasses, look at your phone, tablet or panel display, and slowly tilt your head side to side.

Windscreens and Distortion

Glass cockpits aren't the only issue. Many aircraft windscreens are made of stretched acrylic or laminated layers. These materials contain internal stresses from manufacturing that are normally invisible.

Polarized lenses can make those stresses visible as streaks, swirls or rainbow patterns across the windscreen. The FAA says polarized lenses "may also interfere with visibility through an aircraft windscreen" by enhancing striations in laminated materials. The CAA notes that they can "cause distortion patterns from certain multi-layered cockpit windshields."

Those patterns are distracting at best. At worst they sit right in your line of sight when you are looking for traffic or the runway.

Seeing Traffic

One of the earliest clues to another aircraft is often a brief flash of sunlight reflecting off its windscreen, wing or prop. Pilots learn to react to that glint.

Because polarized lenses are designed to block reflected glare, they can hide that flash. The FAA notes that polarization may "mask the sparkle of light that reflects off shiny surfaces," which can slow your reaction in a see-and-avoid situation.

The CAA adds that polarized lenses can change how clouds look and reduce ground reflections that VFR pilots use as visual cues, such as the shine of a lake or river you are using for navigation.

What to Wear Instead

The answer isn't to fly without sunglasses. Bright sun at altitude causes eye fatigue, and the FAA recommends good sunglasses for flying. The answer is to choose the right lenses.

Choose non-polarized lenses

High-quality non-polarized lenses cut brightness without interfering with displays, windscreens or traffic spotting. Many of the best pilot sunglasses are sold non-polarized for exactly this reason.

Pick the right darkness

The FAA recommends lenses that screen out 70 to 85% of visible light. Lenses darker than that can make it hard to see into shaded areas of the panel or read charts. For more on choosing lens darkness, see our guide on how to select the darkness of sunglass lenses.

Use a neutral tint

Gray and other neutral tints keep colors true, so you can read color-coded displays, charts and light signals accurately. Some lenses use other tints or filtering technology to boost contrast. If you consider one of those, make sure colors on your displays and charts still look right through it.

Look for quality optics

Good lenses should be free of distortion and offer full UV protection. Mineral glass lenses offer excellent clarity and scratch resistance, while quality polycarbonate and resin lenses are lighter and more impact resistant.

Non-Polarized Pilot Sunglasses We Carry

All of these are available with non-polarized lenses. Some also come in polarized versions, so be sure to choose the non-polarized option for flying.

• Scheyden C-130: hand-crafted titanium with true mineral glass lenses. $309 to $349.
• Scheyden Mustang: inspired by the P-51, with hand-polished mineral glass. $309 to $349.
• Scheyden B-24 Liberator: pure titanium with slim temples for headsets. $289.
• Flying Eyes Peregrine: pure titanium with non-polarized lenses and 1mm Resilamide temples. $299.
• Flying Eyes Cooper: a classic aviator shape with ultra-thin temples. $239.
• Method Seven Interceptor: non-polarized lenses with ultra-thin temples. $175.
• Method Seven Altitude FLT18: notch-filtering FLT lenses in an ultra-thin frame. $225.
• AO Original Pilot: the classic American-made pilot sunglass with bayonet temples. $250 to $335.
• Eagle Eyes Freedom Non-Polarized: a military-style aviator at an entry-level price. $79.95.

Browse our full pilot sunglasses collection for more options.

Keep Your Polarized Pair for the Ground

None of this means you should throw out your polarized sunglasses. They are still excellent for fishing, boating, driving and skiing. Many pilots keep two pairs: a non-polarized pair in the flight bag and a polarized pair in the car.

Just make it a habit to check which pair you grabbed before you climb into the cockpit.

Sources

• Federal Aviation Administration, Sunglasses for Pilots (OK-24-1154).
• UK Civil Aviation Authority, Use of sunglasses for pilots.
• Federal Aviation Administration, Pilot Minute: What are some important safety considerations regarding sunglasses?

Questions about choosing sunglasses for your cockpit? Call us at 1 (866) 440-2461 or email jetaviator7@aviator-sunglasses.net. Every pair comes with free returns and exchanges within 30 days.

Until next time, keep your eyes safe and focused on what's ahead of you!