It was just a little bit of frost

Chock to chock
by Dale Nielsen

We have all heard the stories about what can happen to us if we do not clean all the frost or snow off the wings and tail of our aircraft before we go flying. We also have heard the "hangar" stories about pilots who have departed with just a little bit of frost on the wings, and claim it didn’t affect aircraft performance. We may have done it ourselves. We were lucky.
The pilot of a float-equipped Murphy Rebel intended to do a local flight around the lake with his wife. He attempted to brush some of the snow from the top of the aircraft wing, but was unable to get all of it. He decided to go anyway. Once airborne, the right wing dropped. The pilot attempted to keep straight with left rudder while he aborted the takeoff. The aircraft touched down on the lake in a forward slip. The left float failed, the left wing and the left side of the fuselage were damaged, and the aircraft gradually rolled over. The pilot and his wife were able to exit the aircraft and swim to an island. They stayed in a cabin on the island until they could attract the attention of a passing boat.
A float-equipped Cessna took off from a river, attained a steep nose high attitude, stalled and crashed into the ground. Witnesses reported the engine was running erratically, and that after the crash they noticed the aircraft was covered with a heavy layer of hoarfrost. The investigation revealed a significant amount of ice and water in the fuel system.
A Cessna 421 pilot was observed brushing snow off the wings of his aircraft. He then loaded the eight-place aircraft with nine persons and departed with granular ice on the wings and horizontal stabilizer. The aircraft crashed shortly after takeoff. The pilot and two passengers were killed, four passengers received serious injuries, one passenger received minor injuries, and one passenger was unhurt. The 258-lb over gross weight condition of the aircraft added to the problem.
Two of the pilots in the incidents described above added to their snow or frost contamination problems to make a bad situation even worse. One didn’t check for water in the fuel, and the other was over gross weight. In each case, the onset of the stall was accelerated. Would stalls have occurred if the float-equipped Cessna engine was running normally, or if the C-421 had not been over gross weight? We can’t positively say they would have, but it is highly likely that this would have been the case.
The folks at Transport Canada continue to harp about the clean wing concept. They have spent considerable time and energy educating us about the dangers of taking off with any ice, snow or frost on the critical surfaces of the aircraft. They define the critical surfaces as being the wings, and the horizontal and vertical stabilizers.
Whenever possible, prevent ice, frost or snow from accumulating in the first place. Hangars are perfect for this, but not always possible or practical. Any shelter with a cover will work. It doesn’t have to be enclosed.
Wing and tail covers are available from several sources for most types of aircraft. They are relatively inexpensive and work well. Cheap tarps can be used to make wing and tail covers. They may not fit as well as professionally made covers, but they work.
If the worst case happens, and you are not prepared for the snow or frost that unexpectedly occurs overnight, clean the snow off the entire aircraft, and clean the remaining frost or ice off the critical surfaces, right down to the paint. A heated hangar is the best option.
De-icing fluids such as isoproponol work well, especially if heated. Care must be taken with de-icing fluids so that the fluid is not sprayed directly onto windscreens or into static or pitot inlets, as damage may occur. Loose ice, snow or frost will sometimes slide down into the crevices between the wings and the flaps and ailerons, or between the horizontal stabilizer and the elevators during the de-icing process. This ice, snow or frost may re-freeze and jam a control surface. Make sure these areas are carefully cleaned out while de-icing.
Let the aircraft sit in the sun. The sun will clean off the frost, even on very cold days. It just takes time.
A rope rubbed gently over aircraft surfaces will loosen most of the frost. The aircraft can then be wiped off with a broom, cloth or a glove.
Gentle use of plastic windshield scrapers will clean off cranky ice and frost, and in a pinch a credit card will do.
Hot water has been touted by some as a de-icing method. The problem with hot water is that a very thin and hard to see layer of ice tends to form on the surface. You only think the wing is clean. Ice may also form around hinges and push rod joints, jamming control surfaces.
High wing aircraft are difficult to manually de-ice. Float aircraft are even more difficult. There is a very real tendency to get tired and frustrated and say that a partial job is good enough.
Even after the aircraft has been defrosted right to the paint, keep an eye on the wings. Atmospheric conditions may be such that frost may form again before takeoff. Seaplanes taking off in sub-zero weather may get ice on the tail caused by the spray on take off.
Any ice, snow, or frost on the critical surfaces, or even a suspicion of contamination on the critical surfaces should be grounds for aborting a flight. The clean aircraft concept means no ice, snow or frost on any critical surface.
Ignoring this simple rule is really tempting fate. You may survive the takeoff, but you probably have a better chance of winning a lottery.

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