Icing for General Aviation Pilots Date: 1 Jan 06

Important facts about icing Rev: Orig

An iced wing will always stall at a lower Angle of Attack (AOA) and higher Airspeeds Ask two questions when dealing with icing:

o Where is the ice?o Where is it safe?

Icing conditions exists when:o Visible moisture (Clouds or Precipitation)o Temperatures are in the freezing range (+2°C to -20°C)

Icing conditions do not exists when:o Outside of cloudso No freezing precipitationo Temperature outside of freezing range

Important factors to know over the entire route when icing conditions presento Ceilingso Cloud Topso Freezing Levelso PIREPSo Frontal Activityo As well as AIRMET and SIGMET

A pilot cannot fly into forecast icing, not just known icing Different kinds of aircraft accumulate ice differently Aircraft are certified for flight into known icing within a specific envelope Check De-icing or Anti-icing equipment on the ground when icing may be present during the flight Keep a watchful eye on the Outside Air Temperature (OAT) gauge When flying and need to change altitude or course due to icing use “IMMEDIATE” to help the

controller understand the situation Also tell them you can accept changes in heading to help the immediate change in altitude Try to get out of icing as soon as possible in aircraft without any icing equipment There are Five (5) outs to help you safely get around flying in icing

o Climb → Get to colder temperatures where icing may not be present Be aware that cloud tops can hold some of the most hazardous icing conditions

o Descent → Get below clouds where icing may occur or get into warmer temperatures Be aware that the lower you go can decrease your distance above the ground

o Continue → If in the process of exiting icing conditionso Divert → circum navigate the icing conditionso If all else fails DECLARE AN EMERGENCY

It will increase your options that ATC can help you or that you can do GET OUT OF FREEZING RAIN AND FREEZING DRIZZLE IMMEDIATELY

o No aircraft can handle a moderate amount of accumulation due to freezing precipitation If you are in icing and ATC cannot get you out of it quick enough DECLARE AND EMERGENCY Make PIREPS (Pilot Reports) to help ATC know and other pilots of the conditions at that time

o There is a small problem with icing reports, they are subjective due to the experience of the pilot and the type of aircraft

Don’t be afraid to ask ATC for PIREPS Report the absence of icing when forecasted There are Three (3) kinds of icing

o Rime → has a milky look (like that of a freezer that needs defrosting) Conforms to the airfoil

For reference only, does not replace any government approved publication. Page 1 of 3

Icing for General Aviation Pilots Date: 1 Jan 06

Important facts about icing Rev: Orig

Accumulates in a pointed shapeo Clear → transparent look

Rough accumulation Forms horns which dramatically increase drag

o Mixed → clear in the center with white on the sides Could have any of the above mentions qualities

There are Three (3) amounts of accumulationo Light → ¼ inch accumulation within 15 – 60 minutes

occasional use of icing equipmento Moderate → ¼ inch accumulation within 5 – 15 minutes

Frequent use of icing equipmento Severe → greater than ¼ inch accumulation within 5 – 15 minutes

Exit immediately, no aircraft is certified for flight in severe icing Give PIREPS Interpolate PIREPS

o If a B737 is climbing to altitude and incurs light icing a C182 may incur severe icing due to duration within the icing altitude

o Each aircraft will accumulate icing differently due to design and icing equipment At the first sign of icing turn on all icing protection

o Window Heato Prop Deiceo Fluid Surface De-icero Pneumatic Bootso Pitot Heat (if not already on)

Keep wings clean Ice bridging only affected early boots when times for inflation and deflation were increased Previous pilots were told to wait until at least a ¼ inch was on the wing, no longer required With modern boots there has never been a case when ice bridging has cause and accident Struts, OAT gauge probes, and other similar size items pick up ice before wings including tail

surfaces Test conducted by NASA on several modern airfoils demonstrated that, in some instances, exposure

to clear icing for 2 minutes could double the drag, reduce the maximum lift by 25-30% and reduce the critical angle of attack by 8 degrees (which would correspond to a substantially higher stall speed)

NASA saw a 30% increase in drag on the aircraft due to accumulations in areas without icing protection

When on top of the clouds and you see a rainbow that means that there is liquid water in the clouds If possible hand fly the aircraft through all possible icing conditions Hand fly all approaches in icing conditions Symptoms of a wing stall due to icing

o Airframe Buffeto Sluggish or Ineffective Roll Controlo Don’t rely on the stall warning horn it may have frozen over due to icing accumulations

Recovery from a wing stallo Reduce AOAo Increase Powero Same as clean wing stall

If ice is on the wind it is probably on the tail

For reference only, does not replace any government approved publication. Page 2 of 3

Icing for General Aviation Pilots Date: 1 Jan 06

Important facts about icing Rev: Orig

If increase thrust will induce a nose down pitch it could aggravate a tail stall Symptoms of a tail stall due to icing

o Lightening of the yoke especially in the forward directiono Difficulty trimming the pitcho Pitch excursions similar to pilot induced oscillationso Buffet in the yoke only not the airframe

Recovery from a tail stallo Pull back on yokeo Raise flapso Consider reducing power

Wing Stall verses Tail Stallo Wing stall

High wing AOA Slow airspeed

o Tail Stall High tail AOA Flaps down Higher airspeed

If a an unanticipated movement occurs UNDO WHAT YOU JUST DID If you know you are going to have to descent into icing conditions and the aircraft may not handle it

well stay on top as long as possible Keep your speed up! If snowing water is already frozen and ice crystals will bounce off of the aircraft Cycle boots (if installed) at the Final Approach Fix (FAF) to get the best performance out of the

aircraft Keep your speed up (stall speed can increase up to 30 knots with icing!) Ice that has little effect at cruise can have a major effect at slower airspeeds When shooting and instrument approach in icing conditions:

o Increase speedo Consider reduced flapso Minimize bank angles due to possible increase stall speedo Consider delaying gear extension until runway is made

For reference only, does not replace any government approved publication. Page 3 of 3