Winter Operations

Anti-icing Additives

 Since 1975, the investigations of 50 airplane accidents disclosed ice in the fuel system of the airplane.  These accidents resulted in 15 fatalities and 13 serious injuries.

While proper fuel sampling and sumping is essential in preventing the formation of ice due to free water in the fuel, it will not eliminate the hazard of ice blockage of fuel flow.  Under certain conditions, water in suspension or solution may form ice crystals. Since water in suspension or solution is not removed by sumping, the formation of ice crystals must be prevented by adding anti-icing additives, such as isopropyl alcohol or ethylene glycol monomethyl either (EGME), to the fuel.  Both additives absorb water and reduce the freezing point of the mixture.  Teledyne Continental Motors and Avco Lycoming approve the use of both additives in their engines, subject to approval by the respective airframe manufacturer’s recommendations regarding the use of anti-icing additives in the fuel for your specific aircraft. DO NOT USE THE HEET USED BY MUSHERS TO HEAT THEIR WATER. 

Draining Sumps

Proper sumping is very important during the preflight check.  Sufficient fuel should be drawn off into a transparent container to see if the fuel is free of contaminants.  Extra care should be taken during changes in temperature, particularly when it nears the freezing level.  Ice may be in the tanks, which may turn to water when the temperature rises, and may filter down into the carburetor or fuel controller causing engine failure.  Water can freeze in lines and filter causing stoppage.  A small amount of water, when frozen, can prevent proper operation of fuel pumps, selector valves, and carburetors. 

Snow and Ice Removal

Aircraft easily accumulate snow, ice, and frost.  Snow and ice are obvious and must be removed before flight.  Frost, however, is more deceptive.  Frost not only increases gross weight, it drastically alters the lift-drag ratio of an aircraft making takeoff extremely hazardous.  There is no such thing as a little frost on aircraft surfaces.  The only conditions that apply are none or some - and some is too much.  Never risk aircraft damage by chipping or scraping it off; let the warmth of a hanger or deicer do it gently.

Where removal of deposits must be accomplished outside, the use of a nonflammable deicing fluid, such as one containing a glycol base, is quite effective.  This type of remover has an additional advantage in that the slow rate of evaporation coupled with its viscosity leaves a protective film on the surfaces which dissipates slowly thereby providing a latent degree of protection.  Protection decreases with time and melting snow diluting the fluid.

The glycol solution should not be applied to acrylic plastics as it may cause crazing.  Do not spray deicing fluid into pitot tubes, static ports, or engine inlets.  The inaccessibility of the horizontal stabilizer on T-tail aircraft makes it easy to overlook when inspecting and deicing these aircraft.

An item often neglected and the source of many problems, is the landing gear of aircraft operating from mud, snow, and slush covered surfaces.  Experience has proven it wise to remove most types of wheel streamline covers from fixed-gear aircraft, during winter months even though it results in a never-ending job of trying to keep the aircraft clean.  This practice eliminates the possibility of mud, slush, etc., building up between the tires and streamline covers and then freezing into a solid mass.  On retractable-gear aircraft, the integrity of shields, boots, and curtains used to protect actuating devices and switches must be maintained.  In addition, retraction mechanism lubrication, in accordance with the manufacturers recommendations, cannot be over stressed.  Oleo struts should be serviced with nitrogen for winter operations.  Otherwise, ice crystals can form in the hydraulic fluid and cut the seals.  The struts should also be wiped with clean hydraulic fluid to remove snow, ice, and dirt.  Improperly rigged skis are also a relatively common source for accidents each winter. 

Refreeze Problems

 Make sure there is no melted ice (water) on the aircraft that can refreeze on surfaces, in flight control areas, or landing gear mechanisms when they are out in the cold again.  Small quantities of water accumulating in places such as control surfaces may create a condition of static unbalance that would seriously impair the operational control of the aircraft in flight.  Check the pitot head area and static ports for any  refreeze problems that may create turbulent air flow.

Water freezing in accessories may also cause a problem.  For example, a pilot could not get either alternator on the line after starting both engines.  Investigation revealed that moisture trapped in the alternator had frozen the rotor preventing rotation.  When the starters engaged, the alternator drive pad couplings sheared.

Check drain holes in pitot tubes, wings, stabilizers, flight control surfaces, fuselages, and air scoops to make sure they are unobstructed and capable of serving their intended purpose.  Systems should be checked for the presence of water in accordance with the appropriate aircraft manufacturer’s recommendations.  Special attention should be paid to deicer boots and prop deicers.

Maintenance and operations personnel should leave propellers on parked aircraft in a position that will reduce the chance of water accumulating in the spinner cavities causing unbalance and resulting in damage when the engine is started and run.  In order to prevent prop oil congealing and the prop becoming inoperative during flight in very cold weather, it may be necessary to exercise the constant speed prop every few minutes by moving the prop controls forward and back during flight.  Be careful and avoid over speed. 

Winterization Kits and Procedures

 Cold weather operation of the aircraft engine involves conditions that require special preparations and precautions as compared to normal weather operation.  Vaporization of the fuel becomes difficult, and high viscosity of oil causes reduced cranking speed with accompanying high loads on the starter.  Often  the accessories fail because of congealed oil.  This is very evident by the increased number of oil cooler failures on reciprocating engines in cold weather.  Excessive priming washes the oil from the piston rings and cylinder wall causing piston scuffing and scoring of the cylinders.  If your aircraft has 50 weight oil for operation in warm weather, consider changing to a lower viscosity oil (generally 30 weight), before flying in very cold weather.

Some aircraft use winterizing kits to maintain desired engine operating temperatures and to prevent oil coolers and vapor vent lines from freezing.  Any questions regarding the utilization of such kits should be directed to the appropriate aircraft manufacturer.  Attention to such details as warming up the engine before takeoff and allowing the engine to cool down prior to shutting it off pays dividends in many ways, especially at overhaul time.  Good practices would also include a check of the carburetor air heat system and the degree of heat rise available.  At the same time, the engine idle r.p.m. and mixture, with and without carburetor air heat, should be checked. 

Engine Preheat

 Some precautions should be considered when using aircraft preheat.  The following recommendations regarding aircraft preheat are from Advisory Circular 91-13C:

A.  Preheat the aircraft by storing in a heated hangar, if possible;

B.  Use only heaters that are in good condition and do not refuel the heater while it is operating

C.  During the heating process, do not leave the aircraft unattended and keep a fire extinguisher handy;

D.  Do not place heat ducting so it will blow hot air directly on combustible parts of the aircraft; such as, upholstery, canvas engine covers, or flexible fuel, oil, and hydraulic lines;

E.      When using a “fire pot” (salamander) for heating, it is suggested that wire mesh be inserted in the ducting between the pot and the engine to stop flaming pieces of carbon from entering the aircraft or engine compartment. 

Things to Watch For

 The crankcase breather deserves special consideration when preparing for cold weather.  Frozen breather lines have created numerous problems.  Most of the water of combustion goes out of the exhaust; however, some water enters the crankcase and is vaporized.  When the vapor cools, it condenses in the breather line subsequently freezing it closed.  Special care is recommended during the preflight to assure that the breather system is free of ice.  Reports are common of engine oil loss from blown crankshaft seals caused by pressure generated by frozen breather tubes.

Breather tubes should be inspected to ensure that the inside surfaces are clear and unobstructed.  It is normal practice for the airframe manufacturer to provide some means of preventing freeze up of the crankcase breather tube.  The breather tube may be insulated, designed so the end is located in a hot area, equipped with an electric heater, or it may incorporate a hole, notch, or slot which is often call a “whistle slot”.  The operator of any aircraft should know which method is used and ensure that the configuration is maintained as specified by the airframe manufacturer. 

Cabin Heaters

 Of utmost importance is the cabin air heating systems and the dangers associated with any form of system leakage that would allow carbon monoxide to enter the area occupied by the crew and passengers.  It is good practice to supplement cabin heating system inspection with periodic carbon monoxide detection tests, especially in those cases where visual inspections are infrequent.  Carbon monoxide tests are reliable and may be accomplished quickly without any disassembly operations.  Such tests, however, are not conclusive as the state of the preservation and actual condition of the component parts of any heating system can only be determined by visual inspection.  Fifty-five different arriving aircraft were checked at an airport and seven appeared to be exposing the occupants to increased levels of carbon monoxide.  Carbon monoxide is a colorless, odorless, and tasteless gas that has long been suspected as a cause from some aircraft accidents.  Don’t guess about this gas, as you can’t see it or smell it.  By the time you feel it, it may be too late.  Further, the susceptibility to carbon monoxide poisoning increases with altitude.

After all these precautions and inspections, remember to be careful as winter is hostile to man and machine!

 Very Cold Weather Flying Tips

Rev 3/2/07

 Besides being unpleasant, very cold weather flying (let’s say colder than -20F) can be deleterious to your airplane and your body.  Here’s a compilation of cold weather flying tips from various Iditarod Air Force pilots.  While there are many opinions, I think most would agree that flying small piston airplanes in weather colder than -35F should be avoided and -30F would be a better guideline. 

Start w/carburetor heat on.  You'll be drawing from inside the "warm" engine cowl.  You should get better atomization. Jim Kintz. 

Even if your heater light is on, check cylinder head temperatures when you come out in the morning because the power could have been off until just before you came out 

Cessna recommends a minimum of +20F for starting. The oil expert in General Aviation News (Ben Visser) recommends you shoot for 40F.  He recommends this because it might be 40F at your sensor and colder elsewhere in your engine.  He said that because of different coefficients of expansion, you could get metal on metal contact at 0F.   For example, one morning when I found the engine cold and began a preheat, after about 30 minutes I noticed the cylinders on one side (side heater was discharging on) were in the 60s and the cylinders on the other side were still in the 20s.

Prop covers do make a difference when it's cold. The prop acts as a heat exchanger to draw heat right out of the critical part of the engine (crankshaft and its bearing).  I've never needed one before but can't remember many starts at -34F either.  The morning I didn't wrap my prop with my wing covers, it would stop my engine when I tried to cycle the prop.  It took me a while before I could get warm oil through the prop. 

With my wing covers wrapped around my prop and a rag stuffed in the bottom cowl openings, my 300 W pan heater held my cylinders in the mid 60s F at -37F outside.  Wes, and I believe Greg, were successfully keeping their engine’s warm using the small propane catalytic heaters.  The Coleman Survival Cat puts out 800 BTU/Hour.  800 BTU/HR is equal to 235 Watts.  So with a good engine and prop cover (properly installed), you don’t need all that much heat. 

I put my drop light in the engine one morning, thinking I needed it there, and my instruments and tach made so much noise when I started the engine, it was scary.  I had to adjust the prop RPM by sound because my tach was bouncing around so much.  This can't be good for the instruments.  Also, I didn't get oil pressure for a long time.  The next night, I put my 150 W drop light under the panel and put my parka over the dash and draped it down in front of the panel.  The following morning, which was the coldest of our stay there (-39F), there wasn't any loud screaming from the instruments, the tach worked normally and I was able to get a little oil pressure indication.  It had warmed up to -34F when I tried to start.  I think the oil in the small tube to the pressure gauge congeals in the portion of the tube that is inside the cockpit.  Ed says if you can cycle your prop you have oil pressure.  He didn’t say how much. 

If you have a rear battery, take it inside at night.  Richard Dowling 

Be sure to have a rag handy to wipe the frost off the inside of the windows.  Richard Dowling 

If you plug the windshield defroster vent with a rag, you can minimize or stop the frost forming during the night on the inside of the windshield above the vent.  Wes Erb 

    Think of the carburetor heat as another mixture control.  With mixture at full rich on a carb engine, and the temp way down there, consider the density altitude. Low temperature is generally associated with high pressure, which aggravates the problem.  Check pressure altitude, set 29.92 in the window and read the altimeter, then apply the temperature.  MCG is 338 MSL. With a local altimeter of 30.50 that would be a .58, or 580 foot correction. When you apply -40 (C or F is same) it comes out to a density altitude of about 8,000 ft below sea level.  Unless your carb is jetted super rich, the only way to adjust the mixture to where your engine will run worth a damn (and safely), is to use carb heat.  It makes the engine think it in San Francisco instead of MCG. Maybe some of you have density altitude computation capability with your GPS, I don't, but have an E-6B whiz wheel, and have computed density altitudes as low as 11,000 ft below sea level. Spectacular performance, but without carb heat your engine may be running way too lean!  Mike Koskovich  The plate on the front of the air filter helps and some engines, like Bob’s, need it to keep from running way too lean.  And I agree with Kosko.  In addition to the intake plate, I have to use carburetor heat to keep my EGTs below 1,500F and my combine EGTs + Cylinder head temperatures below 1,825. 

Be very careful when you grab things like door handles on your airplane with big mitts or gloves.  Be gentle!  They will break off right in your hand if you get too aggressive.  Mike Koskovich  I broke off Kenn’s door handle on a very cold morning in 1996, I believe.  I’m much more gentle now. 

 Aviation gasoline is very difficult to ignite when it is cold.  It has a low vapor pressure.  You’re better off using white gas or car gas in your stove.

 To get a stove to light, wet a small piece of paper (like a piece of paper towel) in gas and light it.  Then use the ignited paper to start your stove.  Jim Kintz

 Make sure you use low temperature grease in your tail wheel.  If you don’t it won’t caster and may destroy the phenolic washer in the tail wheel.  This happened to Jim and Wes this year

 Tire pressures should be checked prior to departing for the interior, the arctic or any known extreme cold.  26 lbs. in ANC on a 25F day will not cut it at -40 & below.  Particularly in the case of wheel penetration type skis with heavy loads.  The tires with reduced pressure due low ambient temp will balloon and rub on the inside of the ski well.  This creates drag and abrades & damages the tire. I usually head West with a solid 35-40 lbs in the mains, and 40 to 50 in the tailwheel.  Nitrogen if you can get it as it is less subject to expansion & contraction.  Learned that from the SeaAirmotive boys, & that was the S.O.P. for North Slope ops. 

Mike Koskovich  I over inflate my tires prior to pulling my bird out of the hangar as I always loose about 8 to 10 psi once outside. 

Russ Dunlap  Theoretically, a tire pressure of 35 PSI (recommended by Landis for their penetration skis) at 70F would be 28 PSI after cooling down to -35F. 

I wrap my cross over tube (runs from one side of the intake to the other) with pipe insulation, I noted a much smoother running engine when cold.  I also wrap my vent tube with pipe insulation. Keep heat in and allows more moisture to exit the vent pipe before it freezes up.  Russ Dunlap  And don’t forget the vent hole in your breather.  It needs to be above the bottom of the cowl where it is still warm.  Hopefully your IA has checked for this. 

Many don’t sump their tanks when it is cold, colder than 15 degrees to prevent the valves from freezing up.  I think this is a questionable process but I have had leaky fuel drains from water freeze up.  In my opinion, if you have tight fuel caps, you regularly drain your sumps (to remove collecting moisture, probably from condensation), keep your tanks as full as comfortable (to minimize condensation) and add Heet or isopropyl alcohol when you see ice crystals, you won’t have a problem.  I do carry a standby fuel drain so I can make a field fix if necessary.  I’ve gone years now since I’ve had a problem.

If you ever spill any gas on the windshield never ever wipe it off in cold temps as static electricity is real nasty when cold just let it evaporate.

Be careful priming or using the throttle to prime, you can get an engine fire if the engine backfires or there is another ignition source.  If you get an engine fire and it is possible to immediately start, go ahead and start the engine, then shut it down and address the fire if it is still burning.  Usually starting will suck and blow the fire out.  I personally, don’t see a problem with minor throttle priming as long as you do it only when the engine is turning over.  This will result in the fuel being sucked into the engine and not dripping out the carburetor.  The fuel that drips out is what causes the fire risk.  I believe it was Danny who recommended doing your priming (using the primer / fuel pump) a few minutes before trying the start.  This allows the fuel to vaporize a little.

Place a 100 watt light under the instrument panel and cover the panel with an insulated cover or jacket

 WINTER SKI TIPS AND TECHNIQUES         

 GENERAL:

 1.  When determining ice thickness, take into account the following:

a.  Current and tides

b.  Cracks

c.  Size of the ice-covered area and the amount of snow cover

d.  Recent temperatures.  With clear ice use the full measured value and with white ice, use only half measured value.

2.  Risk of breaking through increases as the aircraft slows and peaks as the aircraft stops.

 3.  When taxiing, ice cracks should be crossed at a 90 degree angle.

4.  During preflight, check the oil breather line for a hole for winter operations.

5.  Moose tracks usually indicate the ice should be thick enough for a super cub.

6.  If you check unknown ice conditions on snowshoes, keep the bindings loose in case you fall through.

7.      C-185/C-206 with wheels or skis - 8" of new ice recommended - freshwater.

8.  PA-18 with wheels or skis -6" of new ice is recommended - freshwater. This does not apply with spring ice.

9.  For overnight parking, a PA-18 requires 10" of ice, a C-185 requires 13" of ice.

10.  For wheel landings in snow conditions (known or unknown), be prepared to add power and controls back to prevent craft from flipping over onto its back.  Do not relax until the aircraft is completely stopped.  The most critical time for flipping is just prior to a full stop.

 11. Using small logs or pieces of 2x4's to block up the skis will prevent the skis from freezing to ice or snow.  In areas where you have a lot of blowing snow, garbage bags fitted over the ski or visqueen under the ski will prevent the ski from freezing down.

 12. (Optional) Draining the oil in very cold weather and keeping it warm will enhance lubrication to vital areas of the engine when the oil is put back in the crankcase.

 13.  Winter plates should be installed as per the operating handbook for the temperature you will be operating in.  Check the upper air temperature charts.  You might have an inversion.

 14.  Inner tube stems that stick out from cover plates will snap off in crusted ice or wet (near freezing) snow conditions.  Remove the cover plate and reposition the stem inside.

 15.  Use only credit-card type plastic or a plastic scrub brush to scrape frost off the windshield.  (Too much heavy pressure or rubbing can scratch the Plexiglas).

 16. Upon entering a cold cabin (prior to starting the engine), leave the doors and/or windows cracked.  This will help the frost from building up on the windows.

 17. When over-flying the intended landing area, try keeping the sun behind you.  This will help you to determine the conditions better.  In addition, a low level look from the side as well as over the top will yield additional information about the surface conditions.

 18. Sometimes in bright light conditions, it helps to place a set of tracks downwind, so when you turn into the sun you have something to shoot for.

 19. Never land in low light conditions unless you can be certain of the surface.  Never land in an unknown area in low light conditions.

 20. Always verify ski down position before landing.  Use a mirror mounted on the window. (Co-pilot side).

 21. If stuck in wet snow or overflow, place small logs or limbs in front of ski, then taxi up onto them.  You might have to place visqueen under the ski to get started. Visqueen, placed on the bottom of the ski, helps in wet, sticky snow conditions.

 22. When on wheel/skis, you can raise a ski to help you turn in deep snow.  The side having least resistance will raise first.  If on straight skis, cut a hole in the ice or anchor a rope to the ground and the aircraft will pivot toward the tie-down rope.

 23. Never let anyone hand prop your plane unless they have had experience.  The surface under the propeller is often slick

.24. Do not force fuel drains if frozen. This will sometimes break the “O” rings and cause a fuel leak.

 25. Use extreme caution when flying below -25 degrees F.  The temperature can drop; you may find yourself in -45 degrees F.

 26. When you have a Red Line CHT and oil temperature, and a near zero oil pressure, you may be experiencing a frozen oil cooler.  Slow the airplane and maintain a nose high attitude near stall speed (slow flight).  This will directly heat up the nose of the cowling and sometimes unblock the oil cooler.  You can also land and put on engine covers.  Remember, flying at –30 degrees is not recommended.

 30. Over priming a carbureted engine and  pumping the throttle will occasionally backfire and blow a flame back through the carburetor.  Ensure your fire extinguisher is fully charged and available.

 31. Pulling the prop through is not recommended.  To help with the starting, set the prop just past compression after the engine is preheated.  Engine preheating is recommended below 30 degrees and ALWAYS below 20 degrees.  Make sure some who knows the control system is in the cabin and tie the plane down! MAGS OFF!

 32. Aerosol cans of alcohol solution will help remove frost from the wings and tail surfaces.  Stand up-wind to avoid frostbite.

 33.On hard, wind-drifted snow, land parallel to and between drifts, rather than across drifts.  The roughest areas have long cup-shaped ridge patterns (would appear as if you were looking at frozen waves or swells).

 34.  Plan to land on hard wind-drifted snow using the same techniques as for rough water landing on floats, i.e., slow speed, low sink rates, and power on approach.

 35. When landing in semi-whiteout conditions on snow or ice, use the same techniques as for glassy water landings on floats, IE., power on approach, controlled low rate of descent, and maintain speed until touchdown.  Remember: Do not attempt unless you have used the landing area the same day.

 36. Avoid ice-fog.  It looks thin from above but horizontally it is an IFR situation.

 37.  Avoid flight in white-out conditions.

 38.  When taking off in very deep, soft snow, sometimes setting full flaps at the start of the run will help lift the plane up and out of the snow until some speed is gained; flaps can then be reduced to takeoff setting.

 39. If you plan on doing some serious ski flying, off airport, consider a lightweight ice chisel for digging an ice bridge to secure the aircraft.  Dig two holes two feet apart in the ice under the wing. Dig at a slight angle, so the bottoms connect.

 40. Taxi slow when turning on ice and snow.  The edge of the ski can hang up on an obstruction. Given enough momentum, this will bend or buckle the landing gear.

 41. Turning one mag off and applying carb heat will allow you a slower taxi speed on skis.  This technique is especially useful for operating in a congested area or on glare ice.

 42. Rolling the trim all the way to the forward position in the C-185 will make it easier to turn in deep snow.  Be sure to return it to the take-of position.

 43. It is often difficult to stay in your ski tracks at the beginning of your takeoff run.  If you are having this problem, start your next takeoff run pointed to 30 degrees to the right.  Instead of using full deflection to stay on course, allow the torque to turn the aircraft to the left.

 44. While dragging a possible landing site in the C-185, if you hear the forward limit cable or bungee slap against the bottom of the cowling, it’s generally too rough to land.

 47. If you preheat the interior of a wheel/ski equipped airplane or move it into a heated hanger, cycle the hydraulic cylinder and then leave it in neutral position.  Heat on the brake reservoir may expand the fluid and lock the brakes.

 47. Snow frozen to the skylight can be as dangerous as snow frozen to the wings.  This snow can disturb the airflow over the tail surfaces and cause buffeting.

 48. It is very easy to overheat an engine in the springtime when taxiing in deep, wet, sticky snow.

 49. If you get CHT right up close to red line with repeated takeoff runs and still cannot get off, reduce the power to idle and let the CHT stabilize before shutting the engine down.  Stuck valves are a common problem with engines that are shut down too quickly.

 50. Before starting to taxi on straight skis, make certain the tail wheel steering mechanism is engaged.

 51. Rocking the wings at the upper attach point and/or kicking the toe of the ski during pre-flight, will allow you to determine if your skis are frozen to the ground or if the brake disks are frozen to the brakes.

 52. In the springtime, wet, sticky snow will reduce takeoff performance.  If you are operating out of short lakes, you may need to plan your takeoff after the sun goes below the horizon and the temperature drops a few degrees.  The change of temperature will often reduce a large portion of the drag.

 53. In  times of drifting and blowing snow, beware of snow in pitot tube, tail cone, and ailerons.  These areas can pack full and cause very serious control problems.

 54. Wheel/ski takeoff run is increased significantly.   

 55. Mountaineering Ice screws have a holding strength of over 2000lbs ea. When screwed into a frozen substance. 5 will anchor a plane safely

 56. Aerodynamic drag with wheel skis is increased, which results in increased fuel consumption.

 57. If using a tail ski aircraft with tail ski only, control is minimal until speed has increased for the rudder to be effective.

 58.  Sticky snow increases ground run.

 59. After landing, ground friction heats up the bottom of the ski.  Stop 1 - 2 seconds, taxi length of ski; stop 1- 2  seconds, taxi length of ski, etc.  (Helps cool skis down from heat build-up due to ground friction).

 60. Check fuel selector and fuel shutoff for freedom of movement.

 61. Check all controls, including trim, for freedom of movement.

 62. Aircraft on skis have a tendency to carve a turn once a turn has started.

 63. On shutdown, you may want to consider leaving the mixture full rich, in case it freezes in the idle cut-off position and you don’t have any heating source with you.  Also carb  heat should be in and the trims and controls set for takeoff.

 64. If stuck and ground personnel are available, rock wings with power applied.

 65. If stuck in a super cub, bring tail off the ground and sharply reduce power to help unstick aircraft.

 66. Wheel skis - Retract skis and keep aircraft on wheels overnight.

 67.Slow taxiing over glare ice downwind with a strong tail wind,  rudder application can turn the aircraft opposite of your intended direction if your taxiing speed and air flow is lower than tail wind velocity.  It may help to keep the wheels down for better directional control in the wheel/ski configuration.

 68. If volcanic ash or sand is present, you may not be able to takeoff or the takeoff  run will be very long.

 69. Turning around on beaches, hills, etc., jack the down-hill ski up and pivot around it.

 70. If volcanic ash or sand is present, you may not be able to takeoff or the takeoff  run will be very long.

 71, Mounaineering Ice Screws will hold 2000lbs each 5; 2 for each wing and 1 for the tail will safely secure your plane to Ice or frozen ground.

TIPS AND TECHNIQUES

LAKES:

1.      During freeze-up, ice freezes first along the shoreline.

2.   In spring time, Ice breaks up along the shoreline and ice is thicker in the middle of the lakes.

A. during spring, all operations should be in the middle of the lake, without attempting to taxi to the shoreline for ease of passenger or cargo handling.

 3.  Do not operate near inlets and outlets of the lake and avoid any known or suspected hot spots.

 4.  Hard packed snow (areas of continuous winter operations) melts more slowly than soft snow.

5.  When parking aircraft overnight, park over a known shoreline or as near the beach as possible.

6.   A lake situated at the foot of a mountain or extensive slope will receive considerable ground water.  Sometimes small springs can be seen in the lake bottom on the side of the mountain or slope.  These lakes freeze later than others do and frequently have thin ice on the side near the mountain.

7.  If you see a star-shaped depression on a lake in the snow, stay away.  The depression is weak ice or more likely, overflow.

8.  Avoid marsh areas.

RIVERS:

1.  During warm periods, the water eats away at the ice; during colder periods, ice accumulation is greater than erosion.  River ice thickness varies due to currents and outside temperatures.

 2.  If possible, choose wide areas of the river where the current is calm.

 3.  During mid-winter, slush can often be found near the center of rivers due to water levels dropping, and the ice sinking or settling in the center of the river.  As temperatures fluctuate or rain occurs, the water runs to the low spots and are covered with snow.

 4.  Landing in snow/ice covered stream beds should be avoided.  You probably will encounter overflow or thin shelf ice.

 5.  The thickest river ice is usually found in the dead area of the river or ox bow lake.

 SALTWATER/SEA/PACK ICE:

 1.  When operating on sea ice, consider the following:

a.  Saltwater freezes later than freshwater.

b.  Saltwater freezes at lower temperatures than freshwater.

c.  The best sea ice is usually found in bays.

 2.  Saltwater ice thickness should be double that of freshwater.

 3.  Ice that is dark blue or green should be ok.

 4.  Polar bear tracks are not a reliable indication of ice thickness.  A polar bear can cross ice where a person could not walk.

 5.  Black ice should be avoided.

 6.  New sea ice will increase takeoff distances due to the high salt content of the ice.

 7.   Pressure ridges will usually exist on sea ice and change with the ice movement.  Use extreme caution when attempting a landing on sea ice.  If possible, use a chase plane.

 8.  Refrozen sea ice leads are safe when light green or white and are dangerous when dark green or black.  There is no safe black sea ice like on freshwater lakes.