Training and Safety Tip: Remove frost before flight

January 21, 2025 By Kathleen Vasconcelos

The name of everyone’s favorite snowman—Frosty—is not the word we want to use to describe the wing surfaces of an airplane we’re preparing to fly.

Photo by Tom Haines.

It’s not unusual to find frost on wings and other exposed surfaces of aircraft parked outside on cold nights. This can be expected any time the air temperature falls below freezing and decreases below the dew point. But that frost must be removed from an aircraft before flying.

Any contamination of an aircraft’s wing—whether that is accumulation of snow, ice, or even a thin layer of frost—disrupts the flow of air over the surface of the wing. This is also true of other airfoils, including the horizontal stabilizer, which also generates lift but directs it downward rather than upward. Any disruption of airflow causes an increase in drag, decrease in lift, and increase in stall speed—a dangerous combination that could have a negative effect on the aircraft’s ability to take off and climb.

When frost is present during preflight, completely clean the wings and other lift-producing surfaces so all frost is removed. If there is any moisture left on the wings after cleaning them, dry the wings to prevent contamination refreezing during taxi and takeoff, because contamination on the wings could have serious consequences. According to the FAA’s Pilot’s Handbook of Aeronautical Knowledge, as little as 0.8 millimeter of buildup could reduce lift by 25 percent.

The AOPA Air Safety Institute’s Icing and Cold Weather Ops Safety Center includes videos, publications, and quizzes on the topic of contamination. Other relevant material can be found in FAA Advisory Circular 91-74B and on the National Weather Service’s website.

Frost removal

Removing frost and ice is critical—remember, you want the aircraft to become airborne and you want to be able to see where you are going. Use approved deicing fluids liberally, but do not apply these products on the windshield or windows—you can use a clean towel or shop rag to clean those. Do not use ice scrapers and credit cards as they can damage paint, windshields, and windows. If you do have access to the ultimate defroster/deicer, a heated hangar, the products mentioned below are the next best solutions (pun intended) for removing frost and ice from wings, stabilizes, and control surfaces:

Glycol is the most expensive deicing fluid and is generally only available at select FBOs.
Polypropylene antifreeze is pink in color and available at recreational vehicle, automotive, or marine stores. It works quite well using a spray bottle, or a small garden sprayer. Use caution with composite aircraft. Apply a small amount to an inconspicuous area first, as there have been reports of staining.
Automotive windshield deicer in a spray can is inexpensive and can be purchased at gas stations and department stores. Do not use it on aircraft windshields or windows.
Rubbing alcohol, sold in relatively small quantities in drugstores and supermarkets, can work in a pinch using a spray bottle with a hand pump.

Tip: Dress warm in cold, often windy conditions. A parka, boots, gloves, and hat will encourage you to give this critical job the time and attention it deserves.

—Air Safety Institute Staff

Kathleen Vasconcelos

Kathleen Vasconcelos is an instrument-rated flight instructor and a commercial pilot with multiengine and instrument ratings. She lives in New Hampshire.

Go to Kathleen Vasconcelos's Profile

Topics: Training and Safety, Flight Instructor, Icing and Cold Weather Ops

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