As per some previous discussions on our Discord and some very alarming PIREPs during these winter months at AKV we are happy to bring you what we can in the way of tips to avoid crashes or stalls due to icing conditions in the air. By no means is this our condoning flying in visible moisture during icing conditions, the best defense against icing starts on the ground with a forecast after all.
This guide will not go into depth about why icing occurs nor will it cover anti-ice equipment. Simply “what to do when you’ve got ice” Sometimes these situations are unavoidable and a lot of times IFR can lead to icing unexpectedly. Without further ado:
“Ice Flying”: The Strategy
Smart “ice flying” begins on the ground. For VFR flight operations, with the exceptions of freezing rain, freezing drizzle, and carburetor icing, staying clear of the clouds by a safe margin solves the icing problem. For pilots choosing to go IFR, it becomes more complicated.
Use the many resources available to you:
Direct User Access Terminal (DUAT) system
Flight Service stations
ADDS (Aviation Digital Data Service) found online at https://www.aviationweather.gov/adds/
AOPA Online https://www.aopa.org/
Aviation Weather Center’s current icing potential (CIP) http://aviationweather.gov
Continue to request pilot reports—and make some of your own—along your route if you suspect icing to be a potential problem. Ask the right questions, and remember that conditions that appear to be similar to weather you’ve dealt with before may be much different.
Where are the fronts? Know the big picture because most ice is in fronts and low-pressure centers.
Where are the fronts moving? Where will they be when I depart and when I arrive? Check “upstream” weather reports and trends. If the destination is Cincinnati, what’s the weather in Indianapolis 100 miles to the northwest? Remember that forecasts are not guarantees and plan accordingly.
Where are the cloud tops? You cannot climb through a front with tops to 30,000 feet. For most light non-turbocharged aircraft, once the tops reach 8,000 feet, climbing is no longer an option. Once on top, can you stay on top? Expect much higher clouds over mountains.
Where are the cloud bases? Below the clouds where freezing rain or freezing drizzle is not present, there will be no structural icing.
Where is the warm air? If the freezing level is high enough above the IFR minimum en route altitude (MEA), the flight may be feasible. However, air traffic control may not be able to guarantee you the MEA due to traffic or conflicts with other sectors. If it’s freezing on the surface and the clouds are close to the surface and more than a few thousand feet thick, it is foolish to attempt to climb through to clear conditions on top.
Air mass clouds or frontal clouds? Know the difference between air mass clouds and frontal clouds. Frontal clouds are usually indicative of large areas of significant weather, so an aircraft flying through frontal clouds can be exposed to icing conditions for a longer period of time. Air mass clouds may have snow showers but do not have large areas of steady snow. Unless you are flying in the mountains, steady snow or rain means significant weather is building.
With the exceptions of freezing rain and freezing drizzle, the only way to gather structural ice is in an actual cloud. Flying in snow or between cloud layers will not cause structural ice, although wet snow may adhere to the aircraft.
What alternate routes are available? Flying the flatlands with lower MEAs is likely to provide much better weather, a smoother ride, and less ice than the same trip over the mountains. Detour if necessary. Avoid flying south through a front that is 200 miles long when you could fly west and be through it in 35 miles.
What are the escape routes? At any time during a flight where structural ice is a possibility, you need an alternate plan of action. That could be a climb, descent, 180-degree turn, or immediate landing at a nearby airport. It will depend on traffic, terrain, cloud conditions, visibility, and availability of suitable airports. Quickly tell ATC you are in ice and want out. Ask for a higher or lower altitude or a 180-degree turn. If ATC won’t let you climb due to traffic, let them know that you are willing to accept a climb at any heading.
What pireps are available? Pay particular attention to pireps. Because icing is forecast for extremely broad areas, pireps may be the only information you’ll have as to where the ice is actually occurring. They tell you what the conditions really were at a particular time in a specific place. Think about whether those conditions are likely to be duplicated during your flight. How will you handle it? What are your escape plans?
Pireps are individual judgment calls, so having several for the same area will usually result in a better picture. Be prepared for surprises if you rely on just one pirep. The type of aircraft making the pirep is also critical. When jets or turboprops report moderate ice or worse, that’s a mandate for light aircraft to plan a different strategy immediately. Turbine-powered airplanes are equipped for flight into icing conditions and have much higher performance to punch through an icing layer quickly. A “light” ice report from turbine aircraft may mean moderate ice for you. How old is the pirep? Weather moves and changes, so a report more than 45 minutes old may be of limited use.
The Aeronautical Information Manual (AIM) defines how in-flight icing should be reported when filing a pirep:
- Trace: Ice becomes perceptible. Rate of accumulation is slightly greater than the rate of sublimation.
- Light: The rate of accumulation may create a problem if flight is prolonged in this environment (over one hour). Occasional use of deicing/anti-icing equipment removes/prevents accumulation. It does not present a problem if the deicing/anti-icing equipment is used.
- Moderate: The rate of accumulation is such that even short encounters become potentially hazardous and use of deicing/anti-icing equipment or flight diversion is necessary.
- Severe: The rate of accumulation is such that deicing/anti-icing equipment fails to reduce or control the hazard. An immediate flight diversion is necessary.
“Ice Flying”: The Tactics
(In-flight portions of this section are intended for aircraft that are certified for flight into known icing conditions. Non-certified aircraft must exit any icing conditions immediately.)
Carry extra fuel. In icing conditions, extra power is needed because of increased aerodynamic drag and/or because carburetor heat is used. Fuel consumption will increase.
Other than extra fuel, keep the aircraft as light as possible. The more weight to carry, the slower the climb and the more time spent in ice.
Remove all frost, snow, or ice from the wings. There is no point in starting the day with two strikes against you. Every winter there are “frostbitten” pilots who crash as a result of guessing how much frost their aircraft will carry. A perfectly clean wing is the only safe wing. Don’t count on blowing snow off when taking off. There could be some nasty sticky stuff underneath the snow. If you think it’s light enough to blow off, it should be very easy to brush off before starting. Do it!
The propeller(s) must be dry and clean. Check the controls to be sure there is freedom of movement in all directions.
Check the landing gear (especially retractables) and clean off all accumulated slush. wheel fairings on fixed-gear aircraft should be removed in winter operations because they are slush collectors. Be sure to check wheel wells for ice accumulation. This is always a good idea after taxiing through slush.
Be sure that deice and anti-ice equipment works. When was the last time you actually checked the pitot heat for proper functioning?
Taxi slowly on icy taxiways. The wind may become a limiting factor because the ability to steer and counteract weathervaning tendencies is poor. Tap the brakes lightly and briefly. Hard braking pressure will lock the wheels, resulting in a skid. If the runup area is slick, it may be impossible to run the engine up without sliding. It might be better to stop on the taxiway, leave room to slide, and watch where you’re going. If there is a dry patch of pavement, stop there to do the runup.
Make sure the wing tips and tail are clear of any snow piled up along the edge of the taxiways.
Know where the cloud bases and the tops are, and check for recent pireps. If you encounter icing conditions, have a plan either to return to the departure airport or climb above the ice. If you decide to return, be sure you can safely fly the approach in the existing weather conditions. In either case, advise ATC you will need clearance to proceed as soon as possible. If there is heavy traffic, there may be some delay. If you don’t factor this into the plan, you are not prepared.
You may want to cycle the landing gear after takeoff to help shed ice from the landing gear.
During climb, even though you are anxious to get out of icing, do not climb too steeply because ice can form on the underside of the wing behind the boot. Remember that as the ice accumulates on the underside of the wing, drag increases, sometimes dramatically. Do not lose control of the aircraft.
Make pireps as you go and ask for them en route. Talk to ATC and flight service about any weather developments or forecast changes. All the cautions about pireps mentioned earlier apply here.
Airspeed is a key to measuring ice accumulation. If normal cruise speed is 140 KIAS and you notice the airspeed has dropped to 130 KIAS, it’s time to exit immediately. If you can’t climb or descend, then a 180-degree turn is the only option, and that will result in a loss of at least another 10 KIAS until you’re out of the ice. A 20-knot drop in airspeed is plenty. Add power to increase airspeed, since stall speed margins shrink with speed loss. Speed discipline is essential in icing conditions. The lower the performance of the aircraft, the less airspeed loss can be tolerated. Remember, an aircraft not certified for flight into icing conditions should start working to get out of those conditions at the first sign of ice.
At the first sign of ice accumulation, decide what action you need to take and advise ATC. Do you know where warmer air or a cloud-free altitude is? If you need to modify your route to avoid ice, be firm with ATC about the need to change altitude or direction as soon as possible. Don’t wait until the situation deteriorates; start working with ATC early. If you need to declare an emergency to solve the problem, do it. This is a far better alternative than crashing.
If you’re on top of a cloud layer and can stay on top, ask ATC for a climb well before getting into the clouds. Icing is much worse in the tops of the clouds. If you’re in the clouds and the temperature is close to freezing, ask for a top report ahead. This tells you whether going up is a better option than descending. In a low-power aircraft, climbing through a 3,000- foot icing layer to get on top is chancy.
If flying around mountains, be extra cautious. The air being lifted up the mountain slopes by the wind (called orographic lifting) is known to produce moderate to severe icing conditions.
Expect severe icing potential when flying over or when downwind of the Great Lakes and other large bodies of water. The air is extremely moist, and if the temperatures are freezing or below, the clouds can be loaded with ice.
Do not use the autopilot when in icing conditions. It masks the aerodynamic effects of the ice and may bring the aircraft into a stall or cause control problems. The situation can degrade to the point that autopilot servo control power is exceeded, disconnecting the autopilot. The pilot is then faced with an immediate control deflection for which there was no warning or preparation.
Approach and Landing
Most icing accidents occur in the approach and landing phases of flight. If on top of ice-laden clouds, request ATC’s permission to stay on top as long as possible before having to descend. When carrying ice do not lower the flaps. The airflow change resulting from lowering the flaps may cause a tail with ice accretion to stall. Remember the stall speed is increased when carrying a load of ice, and the stall margin is reduced when you slow to land. If the aircraft is iced up, carry extra power and speed on final approach—at least 10 to 20 knots more speed than usual. Do not use full flaps when carrying this extra speed, or a tail stall may occur. Remember, speed discipline is essential in icing conditions. Most icing accidents occur when the aircraft is maneuvering to land. Be very cautious of turns. The stall potential is high. If you have a choice of airports, use the longest runway possible, even if it means renting a car to get home. A 3,000-foot strip is not the place to go when carrying ice, even though it might be twice the runway you normally use. Because of increased airspeed and a no-flap configuration, the landing distance will be much longer than normal. If there is ice aloft, frequently there may be ice on the runway as well, which greatly increases stopping distance.
If you are unfortunate enough to have an inadvertent icing encounter in an aircraft without windshield anti-ice, turn the defroster on high to possibly keep a portion of the windshield clear. Turn off the cabin heat if that will provide more heat to the windshield.
If the windshield is badly iced, open the side window and attempt to scrape away a small hole using an automotive windshield ice scraper, credit card, or other suitable object. You may damage the windshield, but the alternative could be much worse.
Do not lose control of the aircraft when removing ice from the windshield.
Immediate: A Word to Live By
Pilots are invariably better judges of their flight environment than controllers, but sometimes pilots have difficulty expressing their predicament to ATC. We want to exit icing conditions as soon as possible, but ATC may delay our request for any number of reasons. Now there is a way, short of declaring an emergency, for pilots to get expeditious handling. Requesting an immediate climb, descent, or turn lets the controller know that unless the request is handled quickly an emergency situation will likely develop.