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Training and Safety Tip: Melt before flight

Early on during flight training, we learn that wings will not develop lift if they have frost on them. Frost contamination disrupts the airflow over the wing, increases drag, and alters the airplane’s flight characteristics.

Morning frost covers the wing of a Van's RV-12. Photo by Tom Haines.

Let’s review two examples that illustrate the effect of airflow disruption.

During the flight of a prototype airplane, the gritty black traction pad applied to the wing’s inboard area—used to walk on when boarding and deplaning—was found to affect the airplane’s flight characteristics. The traction surface increased the stall speed slightly and reduced cruise speeds at specific power settings. Making the traction material narrower solved the problem. It was impressive that something that seemed so trivial would have such a notable effect.

Insect and bug contamination of the laminar flow wing’s smooth leading edge caused another airflow disruption, also increasing the airplane’s stall speed. Wiping the leading edge clean after every flight resolved the issue.

If a few bugs or a strip of sandpaper can affect wing aerodynamics and stall characteristics to such a degree, imagine what an entire wing covered in frost might do—and what it might not.

So, how do you prevent or remove frost contamination?

If possible, warming the airplane up in a hangar is ideal. If that’s not an option, place the airplane in a sunny location and wait for the frost to melt.

Some pilots polish the frost smooth with a broom or a rope or strip of carpet moved back and forth with a seesaw motion with the help of another person. Note, this procedure is prohibited by FAR Part 91 Subpart F for large airplanes. Although the regulation does not specifically address small airplanes, I do not recommend it. Wing covers are a better and common alternative to prevent frost from accumulating on the wings. To remove frost, you can use a deicing fluid called TKS.

TKS fluid is approved by the FAA and all airframe manufacturers. It is available at most FBOs in wintry climates. However, it is expensive. If you’re flying a lot in the wintertime, TKS fluid is a good investment and it can be purchased for less through aviation supply companies.

Be careful what you use on the airplane’s windshield and windows. Ammonia and other household chemicals or household deicing agents will create a permanent haze in the plastic. Also, the FAA prohibits use of automobile windshield washer fluid.

Ed Helmick
Ed Helmick has been a flight instructor since 1988. He formerly managed a flight school in Spanish Fork, Utah, as well as schools in Scottsdale, Arizona; and Honolulu, Hawaii.
Topics: Training and Safety, Student, Flight School
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