The Joys of Winter Flying??
Some look forward to winter each year, perhaps because they ski or snowmobile or simply enjoy the fresh winter air. Others think about shoveling snow, driving on icy roads, starting frigid cars and all the related hassles. Of course, there are the vacation plans to a warm climate that help make it worthwhile!
Winter flying is another world that many pilots don’t understand. Unless you have had the need to fly your Mooney on a -20 degree Fahrenheit day, you may have no idea what it is all about. That temperature sounds treacherous and it is actually dangerous. Even if properly prepared, airplanes simply do not work as well when extremely cold.
What can one do to prepare? First, there are a few service items that must be accomplished. Attempting to fly on a cold day with a summer grade oil can lead to disaster. A proper grade of oil has trouble enough flowing with cold temperatures. An improper grade oil or no winterization of an oil cooler can lead to a congealed cooler, an immediate high oil temperature and loss of oil pressure. The only cure is to slow the airspeed while maintaining power. This requires a gear extension to minimize air flow through the cooler until oil flows again. There is an oil cooler winterization kit available from Mooney for the M20K and the rest of us must improvise. High power on a takeoff with cold oil will also put excessive pressure on oil seals and gaskets. I can tell you from first hand experience that a blown crankshaft seal puts a lot of oil on the windshield in a very short time!
Extra care must be taken with your preflight. Frost, ice or snow on any part of the airplane could do nasty things. An inoperative pitot heat or a partially open ram air door could spoil the day. Frozen brakes after taxiing through snow could cause a blown tire when landing. If the possibility exists that brakes are frozen, a slightly hard landing may be the best choice. Use of aviation isopropyl alcohol should be the norm during the winter. Moisture in the fuel system will freeze and the resulting suspended ice crystals can lead to fuel screen blockage and engine failure. A cracked or leaking muffler system can lead to carbon monoxide poisoning. It absolutely needs to be kept in proper condition. If it has been many years since exhaust repairs, a close look may be warranted. Poor cabin heat could be an indicator of a failing muffler.
A proper preheat is extremely important before starting an engine and should be completed when temperatures are at or below freezing. Failure to do so can lead to cylinder scuffing and excessive starter and accessory wear. An aircraft fuel system simply does not allow for fuel vaporization to occur when cold; starting may not be possible. Often times, an engine may run momentarily and then stop. An immediate frost occurs on the spark plugs and preheat is the only option. At initial engine start, 1200 RPM will provide oil pressure for camshaft lubrication. Then, reduce power for a gentle warm-up. Adequate oil and cylinder temperatures are critical when applying takeoff power as shock heating can be just as detrimental as shock cooling.
If the weatherman has been good to you, and if the sky is clear, you will enjoy a high performance, uneventful flight. However, if the sky is filled with clouds and there are forecasts for icing, you are going to have to use your experience to help make a sound go, no-go decision. Most of our aircraft are not certified for flight in any icing. Reports of a trace may be acceptable but could easily turn serious in a hurry. Does this mean that we must park our airplane for the winter? Not at all. It simply means you must educate yourself. Certainly if the temperatures are above freezing, at some appropriate altitude, you are not going to experience ice. Conversely, if the temperature is quite cold, any significant ice is not likely. If you are able to top the clouds and fly in the clear, both the air and performance are very good. But, if clearing the cloud tops requires a climb through light to moderate rime or mixed icing, there may be a better day if VFR below the overcast is not an option. Many pilots have picked up significant ice when making an approach and having to descend through the ice again. If you should have to descend through icing conditions on an approach, demand to stay on top as long as possible. Then use the landing gear and a low RPM setting to make a rapid descent to landing. Use of speed brakes is not recommended as they, too, can pick up ice. Remember, the most significant icing is normally found in the top few hundred feet of a cloud layer. Cloud tops on a cold winter day are normally not high and getting over them can be easy and fun. However, it is a must to learn from other pilots reporting the actual conditions. DO NOT BE A TEST PILOT.
If encountering unanticipated icing, what are the options? Certainly, a 180 degree turn may be the best. However, if you have been using the services available, you already know from pilot reports whether continuation of a flight is advisable. The tops may have gone higher but are still well within your limits. Climbing early may be a good choice as it may not be an option later if ice is actually encountered. If the decision is made to climb, keep in mind that every flight ends with a descent and if that means icing on an approach, climbing could have been the wrong decision.
How much ice will a Mooney carry? This is a question asked by many pilots. The thin leading edges of the Mooney wing and tail are made for speed and efficiency and it is susceptible to icing. Keep in mind that if wing ice is experienced, tail ice will be even more critical. We have all seen pictures of airplanes full of ice that landed safely and some of us have seen pictures of those that didn’t I simply wish to advise you that any ice on a Mooney is too much. Your life and the lives of your passengers are worth too much to take the risk. Upon encountering any type of icing, a conservative decision needs to be made immediately.
Airframe ice is not the only hazard facing you on a cold winter day. At least you can see ice building on your wing. Something that may be significantly more serious concerns what is happening inside your engine. Induction icing is actually possible at any time of the year to both carbureted and injected engines. All that is required is the ideal combination of moisture and temperature, which does not necessarily have to be below freezing. The first indication of ice in a carburetor equipped engine may be a subtle loss of power ultimately seen in a manifold pressure drop. If icing is present, an application of carburetor heat can result in an extremely rough running engine. If this should occur, leave the heat on and lean to the best operation possible. As the ice is removed, power will be regained.
Contrary to what many people think, fuel injected engines can ice. Normally, power is maintained through automatic alternate air systems. The turbocharged Mooneys also have a manual system that can be used in the case of a manifold pressure loss. This could occur if icing took place in the throttle body area rather than only in a blocked filter. To eliminate the possibility of induction ice, consider manually opening the alternate air system when flying in visible moisture and below freezing temperatures. Be aware of this icing possibility and avoid flight in visible moisture, if possible, when temperatures are below freezing. This is even more critical if safe flight requires the need for high altitude operations in a mountainous area. Induction icing could create enough power loss to force an undesirable descent.
The possibility of induction ice causing a power loss or complete loss of engine is real. We expect induction ice was the cause of an engine out, at night, over western Wisconsin in a M20J. While flying at 9,000 feet in clouds and below freezing temperatures, a local pilot experienced complete loss of power. Since it was at night, options were few and ATC advised the location of the nearest airports. A heading decision was made. Attempts to restart the windmilling engine were futile. All that could be done was to prepare for a forced night landing into unknown terrain. The pilot was more than relieved when the engine came to life approximately 2, 500 feet AGL. He had descended into warmer air and whatever ice was present, disappeared. The landing at their destination was uneventful. An evaluation of the induction air system, including the alternate air and ram air doors, found everything normal. For whatever reason, it is likely induction icing occurred in the throttle body causing interruption of fuel flow and serious mixture concerns. The alternate air source did not resolve this problem as it only alleviates loss of induction air due to a plugged air filter.
Another situation that can lead to engine stoppage is the improper use of the ram air system found on any 200 horsepower Mooney. Ice that may have formed on a ram air door can be forced directly into the fuel injector impact tubes if the ram air door is opened at the wrong time. I have experienced this when opening the ram air door on a M20J after all airframe ice seemed to have disappeared. Opening the door resulted in an immediate loss of significant power and excessive vibration followed by loss of altitude. Closing the ram air door did not resolve the problem. I was fortunate enough to be able to keep the engine running through adjusting power settings and leaning until the ice was melted and power returned. Others have not been as lucky and forced landings have resulted. Make absolutely sure you understand the differences between alternate air, static air and ram air. Use them all correctly; your life could depend on it.
Freezing rain (Z) is another concern. It could turn a wonderful flight into a time to remember. Certainly, it means you have warm air aloft and liquid moisture at the higher altitudes. But, descending into colder air and freezing rain on that approach, could give you an unwanted experience. Freezing rain creates clear ice. This can accumulate quickly, totally covering your airplane, including the windshield, making that landing seem impossible. I have cleared a small spot on the windshield by putting my hand out the vent window. Another hazard due to freezing is no braking action. Try cutting the mixture and coasting to a stop. An idling propeller may be simply too much thrust on an icy runway.
Winter flying can be very enjoyable, but both you and your Mooney must be prepared. Make the conservative decision and stick to it.
Originally published MAPA Log
Revised October, 2009