FROM THE CHIEF - AIRPLANE
Tis the season to be jolly and prepare for ice.....!
The basic rule for GA aircraft and our fleet is "do not operate in icing conditions and remove all ice on the flying surfaces and windshield before flight."
Any accumulation of ice can severely affect the aerodynamic properties of the flight surfaces and can quickly lead to an unstable aircraft.
Only aircraft certified for flight in known ice can launch in known icing conditions but remember, if you are lucky enough to have a GA aircraft certified for known icing, the "known" portion of the icing refers to light or moderate icing conditions only. Severe icing will quickly overcome the capabilities of your equipment.
Ice generally occurs in visible moisture between +5C and -20C but usually in the range of +2C and -10C. So listen up to the weather briefer and if there is visible moisture, temperatures in these ranges and especially if the briefer make any mention of icing conditions, then this is considered "known icing."
Remember, icing only occurs when the temperature is in the right range AND there is visible moisture. If either one of these items is missing, there will be very little likelihood of ice. So before even heading out to the airport, have a look outside. If the clouds are low, look at the temperature and using a lapse rate of about 2C per thousand, take the reported temperature and divide by 2 will give you the approximate freezing level. So a temperature of 10C will give us a freezing level of 5,000 ft. If the cloud level is say 7,000 ft, looks like a good flying day....! Just stay about 3,000 ft below the clouds and you will be OK.
What if you advertently stray into cold, wet conditions and you notice ice starting to accumulate? Providing you have the ground clearance, start an immediate descent and get out of the moisture. If a thin layer and over mountainous terrain, start an immediate climb and get in the clear "on top". The final resort is to make a 180 and return to clear conditions behind. BUT....remember, ice affects the aerodynamics of the aircraft and making a turn requires the flight surfaces to "do the right thing" Any accumulation of ice can affect this so when making the 180 turn, be very gentle and aware of the aircraft "feel." If a wing drops suddenly, or you feel a shudder, straighten out and start a controlled descent in a wing level attitude.
On arrival at an airport after exiting icing conditions, you may still have an accumulation of ice on the horizontal and vertical stabilizer. Deployment of flaps will change the load on the tail section and can lead to a premature stall, so plan to make your approach to the runway relatively flat and fast with no flaps. Better to land long, wheels first...!
Trust this helps and read up on the regulations that pertain to icing here: 91.527, in the AIM at 7-1-22 and this link to the FAA: http://www.faa.gov/news/fact_sheets/news_story.cfm?newsid=10398
Fly safe,
Peter Swift
Fixed-Wing Chief Instructor
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