Icing Flashcards
You’re about to fly a new airplane for the first time, how can you determine whether it’s certified to fly into icing conditions?
Section 2 (Limitations) of the POH. Sometimes this info is found in Section 3 (Emergency Procedures) as well.
Is our aircraft (C172) certified to fly into known icing conditions?
NO
What does the FAA consider to be known icing conditions?
The AIM defines known icing as “atmospheric conditions in which the formation of ice is observed or detected in flight”.
However, an FAA letter of interpretation clarifies known icing to be: when a “reasonable and prudent” pilot would determine that, along the proposed route and altitude, the weather information indicates that ice would form on the plane. http://download.aopa.org/epilot/2009/090126icing.pdf
At times enroute the temperature is expected to be around 5 degrees and it looks like you’ll be flying through some clouds. What’s something you would certainly need to check during your preflight that you typically wouldn’t if you were just preflighting for a local practice flight on a clear day?
Pitot heat.
During your preflight you notice that there’s a small amount of frost on top of the wing that hasn’t melted yet. You’re practically certain that by the time you’re finished with your run-up that it will have melted. Would you start the plane up and proceed with your flight?
No, terrible ADM, you’ll have taken off without confirming that the plane is free of ice.
You’ve just departed KIWA on runway 30L. After departure you followed your IFR clearance which was to turn left heading 120 and climb and maintain 5000. You enter the clouds at 3000ft MSL and immediately start picking up structural icing. Where would you expect this ice to form first?
The first structures to accumulate ice are the surfaces with thin leading edges: antennas, propeller blades, horizontal stabilizers, rudder, and landing gear struts. Usually the pencil-thin outside air temperature gauge is the first place where ice forms on an airplane.
What are you going to do when you get structural icing?
Declare an emergency, turn on all of your anti-icing equip (pitot heat, which should’ve been turned on well prior to entering the clouds in order to give it time to heat up), descend below the clouds, rejoin the VFR traffic pattern and land.
Let’s say that after declaring an emergency, tower tells you to continue your climb, that they need the airspace clear so that Allegiant can takeoff. What are you going to do?
You’ve declared an emergency. Descend anyway.
Up at cruising altitude your OAT reads 4 degrees C. You see some stratiform clouds up ahead in about 5 miles, it looks like you’ll be in them in a few minutes. What are you going to turn on?
Turn on the pitot heat, give it plenty of time to heat up.
Is pitot heat intended to be anti or de-icing What’s the difference
Anti - The former is intended to prevent ice from forming, the latter removes ice that has already formed.
You’re enroute and it’s raining and the OAT reads -2 degrees C. What’s the concern here?
Freezing rain/supercooled water droplets.
What kind of ice would form when the rain hits the plane?
Clear or glaze ice.
What is the most dangerous type of airframe icing? Why?
Clear or glaze ice, because it’s
heavy, hard to see, changes shape of airfoil, disrupts lift characteristics, and spreads out
over parts of the wing that are un-equipped with anti/de-icing features.
Further along on your flight the temp rises to +2 degrees C and you re-enter the clouds. Is it still possible to pick up airframe icing even though the temp is above 0? How?
Yes, from aerodynamic cooling. Also, the exterior of the plane, due to wind chill, is generally colder than the ambient air temp.
On the arrival into your destination airport you’re in IMC with the temperature around freezing. You find yourself having to add more and more nose-up trim in order to relieve control pressure. You extend flaps and suddenly the nose drops. What just happened?
Tailplane stall.
