By Robert N. Rossier, EAA 472091
This piece originally ran in Robert’s Stick and Rudder column in the December 2021 issue of EAA Sport Aviation magazine.
Winter has arrived with its usual array of challenges. The wind is biting cold, the darkness daunting, and my bones are beginning to rattle. It’s times like this that I really envy old St. Nick. The elves must certainly have his back — and I’m sure they tend to such matters as completing his frigid preflight checks. The rest of us must suffer through the process ourselves and try to maintain that all important focus even when the numbing cold taunts us to make the inspection short and sweet.
Sadly for us, the winter weather doesn’t typically cut us any breaks. When it comes to identifying potential hazards in the preflight, there are more possibilities for problems than there are presents beneath the Christmas tree. We sure don’t want to miss anything that might give us a possible surprise in flight, so here are a few items we should beware of.
Winter Aircraft Prep
The first thing we need to do is make certain the aircraft is prepared for the winter season. That includes checking that the cabin heat and defroster function properly, confirming that door and window seals are in working order, and ensuring the vents close properly and securely. We should have our mechanic check out the exhaust muff that provides hot air for the cabin heat system. Leaks in the system can result in deadly and odorless carbon monoxide (CO) entering the cabin. Personally, I like to have a CO monitor in the cockpit for peace of mind. For aircraft equipped with combustion heaters, a thorough checkout by a certificated mechanic is also a good idea to ensure the safety and comfort of proper operation.
One of the challenges we face in winter operations is just getting the engine started. The installation of a plug-in engine oil pan heater can make cold weather starts much easier and reduce wear on the engine. We should also ensure that the aircraft has been serviced with the proper grades of oil and grease for winter operations to keep all parts moving properly. Some aircraft manufacturers recommend the installation of a baffle or cover to shield the oil cooler or other critical components for in-flight operations with those brutal winter temperatures.
We should also have the battery and charging system checked out to ensure we have ample energy for those cold weather starts. A battery that worked fine in the heat of the summer might be woefully inadequate for winter starts. This is also a good time to review any recommended starter limitations — the maximum number and length of cranking sessions before a cooling off period is required.
Finally, many pilots find that removing the wheelpants for winter flight operations is a good idea. Wheelpants make it less likely snow and slush will accumulate and freeze the tires or brakes.
Checking It Twice
If there is one nicety we could all enjoy when preparing for a winter flight, it’s the gift of a heated hangar. Consider carefully any opportunity to hangar the airplane overnight or for several hours before flight — especially if the airframe is contaminated with ice, frost, or snow. Airframe ice, snow, and frost is a serious — yet sometimes overlooked — hazard. As we all should recognize, ice, snow, and frost on the surface of the wings can cause a marked decrease in lift and increase in drag, with chilling results. According to NASA sources, this can sometimes result in a departure stall when climbing out at normal climb speed without even triggering the stall warning. Contamination of control surfaces can result in asymmetric forces that cause an uncontrolled roll or lack of elevator effectiveness. Likewise, contamination of the propeller blades can reduce thrust, and slinging ice can cause impact damage.
A heated hangar helps with decontamination efforts and reduces the cold stress on us, allowing a more focused and complete preflight inspection. A heated hangar also provides better illumination, allowing a more thorough examination of details that could be important.
When performing a preflight on a cold dark morning (or night for that matter), recognize that numerous details can remain hidden in the darkness, including cracks, leaks, blockages, and various forms of damage. A good flashlight or headlamp is a must for any preflight conducted in darkness. When checking the fuel, look for water and ice crystals that could accumulate and clog a fuel line or filter. Shining a light through the side of the fuel sampler can help reveal those tiny ice crystals, along with other forms of contamination that might be present. Remember too that water can freeze in the fuel tanks and then melt later in the day when temperatures rise.
Carefully check the pitot tube and static ports to ensure there are no blockages by ice or snow. Any form of blockage can result in erroneous readings for our airspeed, altimeter, and vertical speed indicator, and can affect operation of autopilots with altitude hold features. Similarly, make sure the crankcase breather vent is free of any blockage from ice or snow. A blockage there can cause a seal to fail or the oil cap to unseat, allowing oil to be blown out of the engine.
Those of us not lucky enough to have a heated hangar might need to add a couple steps to the preflight preparation. Without an engine or oil pan heating element, we may need an engine preheat before we get started. It helps prevent the engine damage that can occur during the first few seconds of operation. In some cases, we’re lucky to get the engine started at all without a preheat. While we’re getting that done, we should also consider a preheat of the cockpit. In bitter cold conditions, gyroscopic instruments in particular may need some additional heat to get their bearing lubricants to work properly. Some pilots report “rain” in the cockpit as frozen condensation melts during a cockpit preheat. Use a towel draped over the glare shield to protect sensitive electronics.
It seems there is no limit to the number of avenues by which winter’s cold can cause issues for unsuspecting pilots. Any number of cold weather maladies can turn up in the winter preflight. We’ve seen tires frozen to the tarmac where freestanding water had accumulated on the tie-down spot and then frozen overnight. Water collecting in and on control surfaces can freeze, causing imbalances or stuck controls that can be dangerous in flight. Snow and ice can accumulate in the prop spinner, causing an imbalance and sometimes severe vibration. I’ve even seen contamination (water) in a brake line freeze, causing a brake to be inoperable.
With the holidays upon us, it’s not unusual to have our minds on gifts, family travel and gatherings, and taking a break from our work routines. But when it comes to flying, we need to stay focused and beware of the preflight issues that the chill of winter can cause. Still, I do wonder if there are any elves out there who might be available to help with winter preflights. That would sure make a fine holiday gift.
Robert N. Rossier, EAA 472091, has been flying for more than 30 years and has worked as a flight instructor, commercial pilot, chief pilot, and FAA flight check airman.