It’s summertime and the weather is hot! Over this dry, sunny season, winter flying is probably the last thing on your mind. However, now is the perfect time to start getting things in place for winter and that includes having a plan for taking care of your airplane.
Why are preparations for winter ops needed in the first place? Cold weather, especially during the engine start and warm up period, can be very damaging to your engine if precautions aren’t taken to ensure that safe temperatures exist inside the engine before you turn the key. I always thought that the biggest problem associated with cold weather was engine oil. The logic is since cold oil is thicker and less viscous as the temperature drops, it is not able to circulate quickly throughout the engine to provide proper lubrication upon starting.
While cold oil may be a factor, the introduction of multiviscocity oils has greatly reduced that issue. The real problem is created by the different ways that various parts of the engine respond to heat. Because aluminum expands more quickly when heated than steel does, the pistons (made of aluminum) expand more quickly than the cylinders (made of steel). This can lead to scuffing on the sides of the cylinder barrel. In the same way, differential heating can reduce clearances which are designed to provide cooling oil to bearings and other vital engine parts, thereby causing damage which greatly reduces the life of the engine.
So how cold is TOO cold? Unfortunately, that is a difficult question to answer. Because there is so much variation between engines, airplanes, and environments, there really isn’t any one specific answer. An older, more worn out engine may actually be less susceptible to cold weather damage than a newer, tighter engine because its internal clearances are probably not as tight as they were a few thousand hours ago. I have heard of some people who preheat their airplanes anytime the temperature falls below about 40 degrees. For us northerners, this seems excessive. On our E33A Bonanza which has a Continental IO520, we generally preheat the airplane when it is cold soaked in temperatures below freezing (32° F).
Here are a few of the best ways to get your machine ready for a cold weather flight:
- Heated Hangar: Nothing beats a heated hangar for warming up an airplane. The warm air is evenly distributed around the engine and in the cockpit (your avionics and gyros will thank you!). The airplane will need to be in the hangar for a while in order to warm up the guts of the engine. Often, the easiest way is to have the airplane pulled in the evening before the planned departure and left overnight. Many FBOs will hangar airplanes overnight for a small fee and it is well worth the price. We almost always have our charter airplanes put into hangars overnight when on a winter trip to ensure that we don’t have any trouble when we depart the next day. This practice has the added benefit of keeping the airframe clear of any ice and snow that may accumulate before you are scheduled to leave.
- Electric Engine Heaters: Multipoint electronic heaters use heating pads that are placed around the engine in order to heat up the various components such as cylinders, the oil pan and crankcase. Most of these systems are designed to be activated by being plugged into a wall outlet with an extension cord. Preheating for a winter flight is as simple as going to the airport the night before and plugging it in. Two well known manufacturers of multipoint engine heaters are Reiff and Tanis. These systems are relatively inexpensive and can be a life saver if you regularly travel in colder climates. If an engine heater is the right choice for you, it is recommended to avoid less expensive models that heat only the oil pan.
Pictured above is the Reiff system. The heated bands go around the cylinder bases and the pad at the bottom of the picture heats the oil pan. Picture Courtesy of www.reiffpreheat.com
- Covers and Blankets: If it is especially cold or you have to preheat outside, having something to insulate the cowling and keep the wind out can be very useful. Regular blankets will work long as you can secure them in place. If you have an ongoing need for additional insulation, there are companies that make custom blankets and propeller covers to fit your airplane. If you are landing and then taking off again relatively quickly, using a few blankets and cowl plugs will work nicely to keep the engine warm while it is sitting outside. In a pinch, placing a couple of powered light bulbs in the cowling overnight with insulation on top can result in sufficient temperatures for starting the engine.
Even with the multipoint electric heater, we still use a blanket while preheating to help keep everything toasty.
- Forced Air: This method is used widely by FBO’s and flight schools. Hot air is produced in a portable heater and is then pumped into the engine compartment via the openings at the front or bottom of the cowling. This method has the benefit of not requiring any additional equipment to be installed on the aircraft beforehand and can be very effective provided there is adequate time for the engine to heat completely before removal.
Pictured above is a Red Dragon engine preheater. Photo courtesy of Red Dragon’s website: www.flameengineering.com
- Winter Baffles: When the air temperature starts to drop into the teens and lower, you may find it difficult to keep your engine temperatures warm enough in cruise flight. The problem is that the air entering the cowling inlets is so cold that it overcools the engine. The solution is to install additional baffling in the engine inlets to reduce the amount of airflow into the cowling. These additional baffles are usually just sheets of aluminum that are cut to the correct size and are bolted in and removed quickly and easily as needed. Some pilots swear by them while others complain that they can cause uneven cooling. If you have questions about winter baffling, I’d suggest talking to your mechanic about your specific airplane.
Winter flying can be extremely rewarding. After their hands thaw from preflight, a pilot is often rewarded with smooth air, improved performance and outstanding views. Just don’t forget to prepare the airplane for the cold. The preparation is often as simple as plugging in an extension cord or making a phone call to the FBO. So whether you live in the north or the south, take good care of your engine so that it can keep taking good care of you.