Polish It Smooth?

Pop Quiz: Is it against the Federal Aviation Regulations to take off with ice and snow on the wings? Will “dry snow” blow off the wings and tail during takeoff? Can you eliminate any takeoff ice hazards by “polishing” frost on the wings until it’s smooth?

A few years ago I was flying a Cessna 172 through Charleston, West Virginia, and was delayed by an approaching snowstorm. I paid for the Skyhawk to be hangared, but the following day when I returned, I found that the FBO at Yeager Airport had not pulled my aircraft inside. It was covered with snow and ice. After some discussion the FBO manager agreed to pull my airplane into a heated hangar free of charge to melt the ice. But the snow and ice was thick and even after a couple of hours (in a hangar heated maybe to just above freezing) there were still irregular clumps of ice that resisted removal even by scrubbing. The FBO employee and “high time” flight instructor (he repeatedly told me he had just been hired by a commuter airline) that had been temporarily re-assigned to me as an ice remover the was tiring of the chore (as was I), and eventually, in all seriousness, offered a “solution“:

Why don’t we pull the plane out onto the ramp” where it was well below freezing, he offered, “then throw a couple of buckets of water on the wings and tail. That’ll fill in the rough spots on the ice and make the wings smooth.

I told him in no uncertain terms that I too was a flight instructor and that advice like that was going to get somebody killed. Although the FBO manager seemed to support his employee’s unorthodox thought process, I prevailed and waited another two hours until all the ice was off the airplane. But on the trip home I wondered, how many pilots would have taken that “experienced” instructor’s advice, and tried to take off with an ice-coated airplane? How easily might someone defer to the “authority” of a recently hired airline protopilot … especially when already a day and several hours behind schedule?

Flying surfaces are designed to be efficient. The idea is to make the airplane able to fly, and controllable, using the least amount of power and pilot effort. To achieve efficiency air must be able to flow, unimpeded, across wings, tail and control surfaces. Even a very small amount of frost can disrupt airflow, as relative wind bounces and burbles through the nooks and crannies between almost microscopic ice crystals on the airframe. Worse yet, the effect is entirely unpredictable. Sure, it’s possible that all those little rifts and moguls will act as perfect vortex generators and your short field performance will actually improve. Then again, perhaps that would be the effect on the left wing, while the right — carrying a slightly different frost pattern — would not fly at all. Plus, stall-warning devices won’t accurately predict the danger; the usual aerodynamic pre-stall warnings (buffet, shaking) may not occur before the bottom drops out. One contaminated wing or stabilizer may stall before the other, causing a spin or loss of control surface effectiveness at an inopportune moment. If I’m not making this clear… You have no way of knowing before it’s too late. Consider this preliminary report from National Transportation Safety Board (NTSB):

This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed.

On February 4, 2003, about 0510 Pacific standard time, a Beech E18S twin-engine airplane, …sustained substantial damage after impacting terrain shortly after takeoff… The commercial pilot, sole occupant, was not injured during the 14 CFR Part 91 positioning flight. Visual meteorological conditions prevailed and a flight plan was not filed. The flight was originating at the time of the accident.

In an interview with the NTSB investigator-in-charge, the pilot reported that during his preflight inspection he noticed ice and frost adhering to the airplane. He stated that after applying glycol to the wings and polishing and brushing off the frost, “then they were smooth.” The pilot further stated that he let the engines warm up for 15 to 20 minutes before “taking it around the patch once to clear the airplane of the ice, and to make sure everything was working properly.” Before releasing the brakes to take off, the pilot brought the power up on both engines “to make sure everything was in the green.” After releasing the brakes, the pilot stated “I slowly brought the power up, maintaining 2000 rpm on the propellers.” He said the tail of the airplane came up about 3/4 of the way down the 5,477 foot runway, and “seeing the end of the runway coming up, I added more power and pulled it off the ground.” The pilot also reported that after seeing a “positive rate” he retracted the landing gear, and shortly thereafter “I felt the airplane mushing, like a stall. I then added more power, but the aircraft kept mushing, and then it impacted terrain with power on both engines.

Even a short “test flight” didn’t predict the stall characteristics of the Twin Beech under a load of frost and re-frozen ice.


Another recent NTSB Preliminary Report reads:

This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed.

On February 4, 2003, about 0755 Pacific standard time, a Beech F35 (Bonanza) collided with fences and a house during an aborted takeoff from a private dirt airstrip… The pilot/owner was operating the airplane under the provisions of 14 CFR Part 91. The commercial pilot, the sole occupant, sustained minor injuries; the airplane sustained substantial damage.

A police officer interviewed the pilot. The pilot said he was “ice heavy” during takeoff, ran out of runway, and tried to abort the takeoff. The airplane went through two fences and then impacted a house. An on scene officer reported that the wheels of the airplane touched down approximately 300 feet from the house.

The Bonanza pilot apparently got the airplane airborne for a short distance, but ice on the wings prevented it from getting out of ground effect.

Fortunately, as general aviation pilots, when we make mistakes we generally only hurt ourselves and our loved ones. The results for air carriers — though substantially more rare — can be significantly worse. The January 13, 1982, crash of an Air Florida Boeing 737-222 in Washington, D.C., killed 78 people … not all were on the plane.

Federal Air Regulation (FAR) 91.527(a) tells us:

No pilot may take off an airplane that has —

  1. Frost, snow, or ice adhering to any propeller, windshield, or powerplant installation or to an airspeed, altimeter, rate of climb, or flight attitude instrument system;
  2. Snow or ice adhering to the wings or stabilizing or control surfaces; or
  3. Any frost adhering to the wings or stabilizing or control surfaces, unless that frost has been polished to make it smooth.”

Problems: (1) there’s absolutely no guidance on how to “polish” frost “smooth,” or to test that operation before takeoff to ensure frost presents no adverse effects; and (2) FAR 91.527(a) applies only to large (maximum gross weight over 12,500 pounds) and turbine-powered multiengine airplanes … not the types most of us fly. (Even that Twin Beech doesn’t fall under the scope of this regulation.)

For the lightplane pilots, FAR 91.7 (Civil Aircraft Airworthiness), 91.13 (Careless and Reckless Operation) and 91.103 (Preflight Action) are our only guidance on taking off with a load of frost or ice … and none of these references mention the threat directly. FAA-H-8083-3, the Airplane Flying Handbook, (Note: this is a Powerpoint presentation) advises under the heading “Airplane Preflight Inspection“:

Ice and frost may be factors during the winter months. There is no amount of ice safe for takeoff (author’s emphasis). Even a thin layer of frost can have a dramatic effect on a wing’s ability to produce lift. The best solution for deicing is a heated hangar.

BOTTOM LINE: There’s no such thing as “a little ice” where airplanes are concerned. Weight isn’t the issue; even a light coating of frost or ice is dangerous because of the dangerous and unpredictable adverse effect it has on aerodynamics. The Federal Air Regulations don’t give lightplane pilots an option of taking off with ice, or trying to “polish it smooth.” Make sure the flying surfaces and controls are completely ice-free or you’re risking your life in an unairworthy airplane.