1. By Harry Hayon and Steve Morley
Winter Flying
By Harry Hayon and Steve Morley

2. Contents Introduction Types of Icing Atmospheric Conditions Break
Steve’s Experiences
Flight Preparation
In-Flight Actions
Summary

3. Introduction

4. Structural Icing

5. Structural Icing
Rime Ice is rough and opaque, formed by supercooled drops rapidly freezing on impact. Often "horns" or protrusions are formed and project into the airflow.

6. Structural Icing
Clear ice is often clear and smooth. Supercooled water droplets, or freezing rain, strike a surface but do not freeze instantly. Forming mostly along an aerofoil's stagnation point, it generally conforms to the shape of the aerofoil.

7. Structural Icing
Mixed ice is a combination of clear and rime ice. It is the most common type of structural icing due to the different size of water droplets found in clouds.

8. Induction System Icing
There are two kinds of induction system icing: carburettor icing, which affects engines with carburettors only, and air intake blockage, which affect aircraft with, and without a carburettors.
Induction icing accidents top the charts as the number one cause of icing accidents, comprising a considerable 52%!
Video

9. Fuel Icing
Less common is fuel icing which is the result of water, held in suspension in the fuel, precipitating and freezing in the induction piping, especially in the elbows formed by bends.

10. Instrument Icing
Pitot heat should be used wherever appropriate in the winter. Be aware that radio signals may be disrupted in icing conditions.

11. Atmospheric Conditions
Icing and Cloud Types
All clouds and fog at subfreezing temperatures have icing potential. However, drop size, drop distribution, and aerodynamic effects of the aircraft influence ice formation. Ice may not form even though the potential exists.

12. Atmospheric Conditions
Icing and Cloud Types
Altostratus
Cumulonimbus
Heaviest icing usually will be found at or slightly above the freezing level where temperatures are never more than a few degrees below freezing. In layer type clouds, continuous icing conditions are rarely found to be more than 5,000 feet above the freezing level, and usually are two or three thousand feet thick.

13. Atmospheric Conditions
Fronts
Freezing rain with a warm front (top) and a cold front (bottom). Rainfalls through warm air aloft into subfreezing cold air near the ground. The rain becomes supercooled and freezes on impact.

14. Atmospheric Conditions
Terrain
Icing is more probable and more hazardous in mountainous regions than over other terrain. Mountain ranges cause rapid upward air motions on the windward side, and these vertical currents support large water drops.

15. Atmospheric Conditions
Ground Icing
Frost, ice pellets, frozen rain, or snow may accumulate on parked aircraft. Pilots should remove all frost and ice from aerofoils prior to take-off. Frost forms near the surface primarily in clear, stable air and with light winds - conditions which in all other respects make weather ideal for flying.

16. Atmospheric Conditions
Strategy – So how do I apply this knowledge?
Where are the fronts?
Where are the fronts moving?
Where are the cloud tops?
Where are the cloud bases?
What Alternate routes are available?
What are the escape routes?

17. Break

18. Steve’s Experiences

19. Flight Preparation
Check all equipment is present (pitot covers, static vent plugs, control surface locks etc)
Some engines may require a winter cooling restrictor
Engine oil may need to be changed
Some aircraft require the addition of Iso-Propyl alcohol in the fuel
Ensure the engine crankcase oil breather pipes are clear and free from deposits

20. Flight Preparation
Check the cabin heater/ demister is working properly before you really need it
Spot type carbon-monoxide detectors only have a limited life once unwrapped – always ensure it’s in date, it could save your life!
Drain the Pitot-Static system if applicable
Check that the pitot heater really is warming the pitot head – but don't burn your hand (use the back of it) or flatten the battery.

21. Flight Preparation
Ensure the battery is in good condition and well charged
Check control cables and adjust if necessary
Check all airframe and prop de-icing systems are operating properly
Check wheel fairings are clear of mud and debris
Check tyre pressures are sufficient

22. Flight Preparation Carry a cloth for demisting
Dress sensibly, the heater may fail or you may have to make a forced landing at some point
Ensure the aircraft is swept clear of all ice, frost and snow, even a small amount will degrade performance significantly!
The best way to remove snow from wings is using a broom or brush
Ensure control surface hinges, vents etc are not contaminated
Do not rely on the snow blowing off on takeoff!

23. In-Flight – Departure
Exercise caution when manoeuvring near areas where obstacles may be covered by snow
Check heater/ defrost early on
Taxy slowly
Allow gyro’s adequate time to spin up
Consider using “soft field” takeoff technique
Ensure no carburettor ice is present prior to takeoff!

24. In-Flight – Enroute After take-off cycle the gear
Monitor conditions with a FIS or VOLMET
Monitor engine RPM or MAP for indications of carburettor icing and apply full carb heat periodically
If ice is present whilst using carb heat an additional decrease in RPM/ MAP may occur, keep carb heat set on hot whilst the ice clears
If the aircraft is fitted with de-icing boots, its good to cycle them from time to time to avoid system valves from sticking

25. In-Flight – Enroute
Airframe icing is most frequently encountered in cumulous and cumulonimbus type clouds (CU/CB)
If you fly in the cloud tops this is typically where the moisture content is highest and ice could form quickly
If Ice does occur act quickly and get out of those conditions
The pencil-like OAT probe is often a good indicator of incoming ice
If icing does occur, keep the speed up, don’t fly too slowly as stall speed has increased
Be aware that the stall warning system may have iced up
Treat any snow stuck to the aircraft’s surfaces as ice
If you are in trouble notify ATC early on and squawk 7700 if necessary
Ice forming on an aircraft can cause weird noises and vibrations, don’t panic, Fly The Aircraft!

26. In-Flight – Landing
If when approaching the airfield the windscreen is obscured, either wait for ice/ snow to melt, or use DV window.
Even a thin coat of ice can require a 20% increase in approach speed
This will also increase the landing distance on what could be a slippery runway
If you suspect tailplane icing, a flapless landing may be necessary or as the POH instructs.
If ice has built up on the tailplane whilst being flown on autopilot it may have auto-trimmed significantly nose down and a large control force on the yoke may be required upon disconnect.
Remember ground temperatures may have fallen in late afternoon and any water on the runway may have frozen!

27. After Flight
Be careful when getting out of the aircraft, assume all surfaces will be slippery!
Use control locks and park into wind
Remember to put pitot covers on once cooled down!
If mud or slush is present clear out of fairings and bays
Notify air traffic if actual conditions were worse than forecasted, it’s important for other pilots to know

28. Summary
• Stay out of icing conditions for which the aircraft has NOT been cleared.
• Note freezing level in the aviation weather forecast. Don’t go unless the aircraft is equipped for the conditions.
• Have warm clothing available for pre-flight and in case of heater failure or forced landing.
• Mud, snow and slush will lengthen take-off and landing runs. Work out your distances.
• Remove all frost, ice and snow from the aircraft – there is no such thing as a little ice.
• Check carefully that all essential electrical services, especially pitot heat, are working properly.
• Check that the heater and demister are effective. Watch out for any signs of carbon monoxide poisoning.
• Be extra vigilant for carb ice.
• If ice does start to form, act promptly, get out of the conditions by descending (beware of high ground), climbing or diverting.
• If you encounter ice, tell ATC so that others can be warned.
• During the approach if you suspect tailplane ice, or suffer a severe pitch down, RETRACT THE FLAPS or as POH instructs.
• If you have to land with an iced up aeroplane, add at least 20% to the approach speed.
• Snow-covered, icy or muddy runways will make the landing run much longer and crosswinds harder to handle.

29. References
Anon, (2014). [online] Available at: [Accessed 15 Nov. 2014].
Anon, (2014). [online] Available at: [Accessed 15 Nov. 2014].
Anon, (2014). [online] Available at: [Accessed 15 Nov. 2014].
Anon, (2014). [online] Available at: [Accessed 15 Nov. 2014].
Anon, (2014). [online] Available at: [Accessed 15 Nov. 2014].
Anon, (2014). [online] Available at: [Accessed 15 Nov. 2014].
Aopa.org, (2014). Cold Weather Operations. [online] Available at: [Accessed 15 Nov. 2014].
Pilotoutlook.com, (2014). Aviation weather -Icing. [online] Available at: [Accessed 16 Nov. 2014].
Training.deicinginnovations.com, (2014). [online] Available at: [Accessed 15 Nov. 2014].
Wikipedia, (2014). Icing conditions. [online] Available at: [Accessed 15 Nov. 2014].

30. By Harry Hayon and Steve Morley
Safe Flying
By Harry Hayon and Steve Morley