Cold Weather Preparation Tips For Pilots And Aircraft
Time has run out for those pilots still waiting to winterize their aircraft. Cold weather is here, and snow has fallen in many parts of the country. This winter checklist is dedicated to those procrastinating pilots, from the seasoned pro to the newest student, to help prepare both their aircraft and themselves for a winter of safe flying. Fliers from some of the coldest areas of the country, including Alaska, helped in preparing the list.
Ron Waterman at the Rapid City, SD, Flight Standards District Office (FSDO) told of one winter problem he has seen involving general aviation pilots. He calls the problem the "big iron" syndrome. He said it describes a typical pilot who formerly flew small aircraft, such as a Cessna 152, but who now, instrument rated, fliers a "big" aircraft, such as a Cessna 182, during winter IFR conditions. The pilot thinks the "big" aircraft can fly in the same weather conditions as the "big iron" aircraft of the airlines. What the pilot does not realize is that the aircraft is not capable of flying in, nor certified for the same winter conditions as the "big iron" planes.
One cold winter day while on an IFR cross-country flight, the pilot has to descend through some clouds for an approach. The aircraft picks up ice and crashes. the pilot may have had the skill but not necessarily the aircraft to handle the freezing conditions. Because cold weather can harm the unwary in many ways, pilots and their aircraft need to be ready for winter's hazards. This list will help the unwary prepare for some of those hazards. Aircraft are easy to prepare for cold weather operations. The problem is preparing pilots to make good, safe, cold weather decisions.
First, the pilot must decide if the aircraft will be flown during the winter or not. Some aircraft are primarily warm weather aircraft-ultralights are a good example - and some pilots simply do not like winter flying. If the aircraft is not going to be flown, the owner should follow the manufacture's special requirements for long-term storage.
Aircraft tied down out in the weather require special attention because of the hazards of ice and snow buildup. The wings and horizontal tail are not designed for the stress of heavy snow and ice loads a winter storm can leave on their upper surfaces. Helicopters also require special attention because their rotor and control systems' vulnerability to ice and snow.
Pilots flying during the winter season must follow the manufactures instructions for servicing and operating their aircraft. The instructions will vary depending upon the type aircraft, its complexity, and such local environmental conditions as temperature and type of precipitation.
FAR Part 43 allows an owner to do some seasonal preparation work under the preventative maintenance rules. In fact the FAR lists 29 specific things an owner can do. Work not listed must be done by a licensed A & P mechanic. A mechanic should also know about unique requirements for the local flying area.
Once an aircraft is prepared for cold weather operations, if it is then flown into a warmer area, such as an aircraft from Minnesota being flown for a mid-winter vacation, the aircraft must be serviced for the warmer operating conditions. The aircraft could be damaged if not properly serviced. An example is removing a winterization kit to prevent possible overheating the engine and damaging the exhaust valves.
Once the operator has made the decision to fly in the cold and has appropriately prepared the aircraft, each pilot operating it needs to ask the following questions.
Oil and Lubricants:
Was the correct grade of engine oil installed? Was the correct grade of lubricant used to grease the aircraft?
Winterization Kits: Is a winterization kit needed? Some manufactures recommend baffles, winter fronts, and oil cooler kits for their aircraft during low temperature operation. If installation approval is not provided by the kit's manufacture, FAA approval may be needed. If baffles are installed, one source recommends the installation of a cylinder head temperature gauge to avoid overheating the engine. If a kit was installed, was it properly signed off and placarded? Do you know at what ambient temperature it should be removed?
Oil System Insulation:
Some manufactures recommend insulating oil lines, oil pressure lines, and the oil tank to prevent oil from congealing and causing damage to the engine and other oil dependent systems. If insulation was installed, is it fireproof and is it the correct type?
Hose clamps, hoses, hydraulic fittings and seals:
Have all hoses, fittings, and seals been inspected and replaced if necessary? Were all parts installed to cold weather specifications?
Does you aircraft need a modification? Some aircraft require a system modification, a breather hole, to prevent the tube from freezing. (In cold weather, water vapor, a normal by-product of engine combustion, may freeze in the end of the oil breather tube, blocking the engine crankcase ventilation system. Internal oil pressure can build up to the point where it can rupture an engine-nose-case oil seal and blow the oil cap off, with the resulting loss of oil and a damaged engine.) If a modification is required, was the installation FAA approved? Is checking the breather tube part of your preflight inspection?
Control cables: Did the A&P mechanic check the control cables for proper winter tension?
(Colder temperature changes can cause control cables to contract, which can lower the cable's tension and make flight controls less effective.)
Was the fuel system inspected for water contamination? Water in the system can freeze and prevent an engine start by blocking fuel flow, or worse, it can freeze after takeoff, causing an engine failure in flight. Freezing water can also rupture fuel lines and components. Another bad situation is an aircraft taking off in the early morning with ice in the fuel tanks. The ice can melt in flight as the temperature gets warmer and stop the engine because of water ingestion. To combat water problems, pilots should only use filtered, pure, water-free fuel and keep the tanks filled to avoid condensation. Pilots should drain the fuel sumps before and after each flight to remove any water in the fuel system. If a fuel additive is used to combat water, is it mixed using the manufacture's instructions to avoid damage tot he aircraft?
There is a fire risk in taking a cold aircraft with full fuel tanks into a warmer hangar. As the cold fuel in the tanks becomes warmer, it will expand and possibly overflow onto the hangar floor causing a potential fire hazard. Care should be taken when servicing a cold aircraft in a hangar because if the increased fire risk. Plus, any fuel will flow over the wing possibly removing any wax or other surface protection you may applied for the winter.
Controllable propellers: Has the aircraft's operating manual been reviewed for the proper cold weather servicing and operation of the controllable pitch propeller/s? Oil pressure-controlled propellers require special care because of the possibility of the oil congealing. Installation of a recalculating system may be required. One manufacture recommends cycling the props periodically during flight to flush the cold oil from the hubs to ensure safe operation.
There are several types of cabin heaters installed in general aviation aircraft. Combustion heaters should be inspected for safe operation to prevent a possible fire. The heater's fuel flow also needs to be checked, because excessive heater fuel flow reduces flight time since the fuel comes from the aircraft's fuel tanks.
The most common heating system in light general aviation aircraft is where outside air is heated by passing it through a shroud or covering on the exhaust system before venting the heated air to the cabin. The system must be inspected for exhaust leaks. A leak could let exhaust gasses, including carbon monoxide gas, into the cockpit, incapacitating the pilot and passengers. Pilots need to be alert to the signs of carbon monoxide poisoning. Tightness across the forehead, headache, tingling in the fingertips, fingernails possibly turning a bluish tint, a feeling of nausea, a ringing in the ears, and not being able to concentrate are all signs of carbon monoxide poisoning. Because of the risk of carbon monoxide in a closed cockpit and the fact it is not readily detectable, pilots, if they so desire, can purchase and use one of the carbon monoxide detectors sold at most fixed base operators.
Detectors vary from the small, simple, chemical spot device which changes color when exposed to CO (They react very slowly and are good for about 30 days.) to complex electronic devices (more reliable but require a mechanic to install them).
Another safety tip is to open an outside air vent or the cabin air knob slightly for some fresh air in the case there is any carbon monoxide leakage in either type heating system.
Air intakes and filters: Have the alternate air sources and air intake been inspected and serviced as required? Snow and ice can block an air intake filter and prevent the engine from developing full power either for takeoff or a go around.
Wheel wells and wheel pants: Do you know the winter operating procedures for your aircraft's landing gear and brakes? Mud and slush can freeze in wheel wells and interfere with the operation of retractable landing gear. Brakes can freeze, locking the wheels. Do you know what to do if you have a problem? Some manufactures recommend delaying retraction of the landing gear to allow wheels to spin a moment to throw off any slush on the wheels or brakes to prevent them from freezing. Another suggestion is to spray the torque links and retraction mechanisms with WD-40 or LPS-1 to force any moisture out of the gear. As always, follow the aircraft operating handbook's recommendations.
The FAA Accident Prevention Program's "Tips on Winter Flying" pamphlet recommends recycling the gear to clear slush buildup only as an emergency procedure. FAA Advisory Circular, "Cold Weather Operation of Aircraft," AC 91-31C, says simply to avoid those types of surfaces in retractable gear aircraft. It also recommends removing wheel pants on fixed-gear aircraft to prevent slush or mud from freezing in the pants and locking the wheels or adding weight. Owners should check with an A&P mechanic before removing the wheel pants though, as removal may require an A&P to recompute the aircraft's weight and balance data, and a form 337 may be required. Removal of the wheel pants will also affect aircraft performance, so pilots should review their flight manual for any change in speed range, performance, or weight and balance.
Have you checked the electrical system of your aircraft? Batteries require special care during cold weather. Wet cell batteries should be kept fully charged and if possible removed from the aircraft if the aircraft cannot be kept in a heated hangar. As the temperature drops, a battery's performance and charge decreases, which increases the risk of cold damage and freezing. Freezing can destroy a battery. If an aircraft battery needs charging, do not use the local gas station's high amperage, fast charging battery charger. It can damage an aircraft battery. Aircraft batteries need to be recharged at a low rate for a longer period of time. A good example is a 24 hour charging period at about 1.5 to 2 amps for most lead-acid aircraft batteries. Because of the importance of the battery and its decreases output in cold weather, the aircraft's electrical system should be checked to ensure optimum performance and recharging capacity.
Dry cell batteries, such ELT or portable transceiver batteries, should be checked as per the manufactures recommendation. Finally, do you know the electrical requirements of the deicing equipment installed in you aircraft and what to do in case of an electrical problem?
Fuselage and control surfaces:
Have the following been done, Control surfaces checked for freedom of movement and defects? Any damage discovered repaired? All drain holes open?
Surfaces cleaned and waxed or covered with the manufacturer's recommended anti-corrosion compound? Hinges serviced with the recommended grade of lubricant? If covers are used to prevent snow and ice from entering the various openings in the fuselage and control surfaces of your aircraft kept outside, have the manufacture's instructions been followed because some covers can damage windows and other surfaces. Are the wings and other surfaces protected from the heavy stress loads snow or ice can cause? Is an overhead roof available or is the snow and ice simply removed as soon as possible?
Materials provided by the Aircraft Owners and Pilots Association (AOPA) identified a relatively new winter danger involving composite aircraft and freezing water. Composite skin damage needs to be repaired immediately to prevent water from penetrating the outer skin and the composite material. If the water freezes, the expanding ice can delaminate the composite material causing structural damage.
Static vents, pitot heat, and alternate static source:
Were the static ports checked to make sure they are open? Was the alternate static source checked for proper operation? Was the pitot heat checked for proper operation?
Carburetor heat control:
Was the carburetor heat system inspected and adjusted as required?
Deice and anti-ice systems:
Was the system inspected and serviced as required? Were all of the solution containers filled, if so equipped?
Tires and brakes:
Were the tires and brakes inspected and serviced as required? Was the tire pressure checked? Do you know the recommended technique for setting the brakes during freezing conditions? Some manufactures recommend not setting the parking brakes if there is a chance they can freeze. If your brakes freeze, do you know how to deice them?
Special winter equipment:
Special winter equipment such as ski gear should be installed and preflighted as per the manufacture's instructions.
Because of the increased fire risk during winter operations, fire extinguishers deserve special attention. Did you inspect and service yours as required for cold weather. Is it one of the units not suitable for cold weather use?
Both Alaska and Canada have specific survival gear requirements that must be complied with for aircraft operating within their areas. It is hard to describe a typical survival kit because of different aircraft operations, routes, and conditions flown in. But each aircraft should carry the type of equipment, including food and shelter, that will enable the people on board to survive until rescue. The kit should be designed for the worse case combination of terrain, temperature, precipitation and time needed for rescue for the route of flight.
The rule is be able to survive the environment after surviving the crash. Many airmen have died from exposure while waiting for help. If the weather is bad enough to cause a crash, it is probably too bad to start a search, so rescue could be delayed while the weather clears.
Once the aircraft is prepared for cold weather operations, the second part of the flight equation is the pilot. The basic question is, "Is the pilot prepared to fly the intended flight and for whatever the weather might bring." The following questions may help you prepare for a typical winter flight.
Do you know and understand the aircraft's systems and what procedures are required if the systems malfunction?
Do you know all of the aircraft's limitations, such as whether or not flight is permitted into known icing conditions?
Do you know the operational effects of low density altitude on your aircraft and its systems?
(Low density altitude can effectively increase the power output of an engine and possibly cause engine damage if proper adjustments are not made.)
Do you understand winter weather and the risks of freezing conditions?
Do you know how to get a complete weather briefing?
Do you know the unique operational requirements for your flight route or area?
Are you qualified and current in the aircraft?
Are you medically safe: no cold or flu for example?
If you are instrument rated, do you know the risks of encountering ice and what must be done when icing is encountered?
Can you fly your aircraft with ice on it?
If not IFR rated, are you prepared to turn back if the weather starts to drop below VFR minimums?
Do you know where to find better weather conditions or warmer temperatures along your route of flight?
Do you have the fuel to get to those conditions or your alternate airport?
Can you takeoff or land on a snow or ice covered runway?
Do you exercise or move your engine, propeller, and flight controls every 10 minutes or so on long flights to make sure they have not frozen?
Are you prepared for extended night operations?
Do you carry a working flashlight in case of an electrical failure?
Are you prepared to survive a crash landing?
Do you have a survival kit? Do you know how to use it?
Have you prepared your passengers for a possible accident?
Have you ensured everyone is properly dressed, including proper winter footwear and hats for the environment over which you will be flying? If the required items are not being worn, are they readily available? In an accident, an injured pilot may not be able or have the time to unpack needed gear stored in the baggage compartment. In one case, a pilot's survival gear sank with his aircraft after a water landing. Fortunately the pilot survived. When asked about cold weather clothes Ron Waterman said, "Pilots need to dress for the cold, even if it is only because the heater quits." Are you prepared if the heater quits? Will you be warm enough to continue the flight or will you have to land to get warm?
These are only a few of the items a pilot must consider when preparing for a winter flight. Winter flying can be safe. But the problems of freezing temperatures, conditions such as ice and snow, and shorter periods of daylight combine to make a pilot's job more demanding and the risks greater during this period of the year. A safe pilot tries to reduce those risks through planning. Proper flight planning and a good preflight are two of the best ways to reduce the risks of winter. Good planning includes:
Having the latest weather information, including freezing levels
Having an alternative plan ready if the weather changes
Having the latest pilot reports, if available
Allowing extra time to preflight because of the need for a thorough ice and frost check of the aircraft and having time to deice if required
Avoiding the urge to cut a preflight short because of the cold and your failure to dress warmly
Reviewing the aircraft's operating handbook for the proper cold weather preflight procedures
Being aware that an aircraft's controls can freeze while the aircraft is taxiing or waiting for takeoff
Remembering that deicing an aircraft does not guarantee the aircraft is ice free
Remembering that if an aircraft is taken into a warm hanger to deice, then taken back outside, new precipitation falling on the now warm aircraft can melt and later freeze while the plane is taxiing or preparing for takeoff
Remembering to always check the flight controls on the runway just before takeoff for freedom of movement because they could have frozen while the aircraft was taxiing to the runway or waiting to takeoff
Following the instructions when using a preheater
Preheating the cockpit to reduce wear on the instruments and avionics equipment
Avoiding the dangerous practice of using an automobile's exhaust heat to warm an engine or cockpit. Carbon monoxide and other harmful gases can buildup in the cockpit plus the gases can damage the aircraft. If everything has been checked by the book, the safest route in terms of survival planned, and the aircraft and pilot are both ready to fly, the single most important thing a pilot can do for a safe flight is to file a flight plan. (If it is a VFR flight plan, the pilot must activate the plan on takeoff and close it after landing.) A flight plan is a pilot's best assurance help will be available if an otherwise perfect flight fails to arrive at its destination. When time is critical, an activated flight plan is a pilot's best hope for rescue.
There are many excellent sources of information on cold weather operations and survival, including the instructions in each aircraft's operating manual. But for a simple and practical guide, airmen can review the FAA Advisory Circular (AC) 91-13C, "Cold Weather Operation of Aircraft." Pilots can request the AC by writing to Department Of Transportation, Utilization and Storage Section M443.2, Washington, DC 20590. The Accident Prevention Program's "Tips on Winter Flying" pamphlet FAA-P-8740-24, is also a good source. It is available from your local FAA district office or by writing to the Accident Prevention Program Branch, AFS-20, 800 Independence Ave., S.W., Washington, DC 20591.
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