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Originally Posted by N121PP
Now that winter is upon us...it has always made me wonder how you can land in freezing rain and it not affect the airframe? I believe ITT you mentioned the wings are heated. Is that the only surface you have to worry about? What do you do different for a wintry mix landing as opposed to just plain snow?
The wings are definitely the critical component on the plane. If ice starts forming on the wings, it can alter the airflow over them and have a serious affect on their ability to generate lift. On the rest of the airframe, the only affect is to add weight and drag, which could potentially be serious in cases of extreme accumulation but is not generally an issue.
When flying or taxiing in icing conditions (defined as visible moisture, or visibility less than one mile, and outside air temperature less than 10° C), we operate with engine anti-ice on. This provides hot engine bleed air to the engine intakes to prevent ice accumulation there which can foul sensors and have an adverse affect on airflow to the engine (with a significant affect on engine performance). You might wonder why we use 10° C (50° F), since that is well above freezing. The reason is that there is a drop in temperature in that intake air due to pressure changes. It's the same reason that general aviation pilots, flying in small piston engine planes, apply carburetor heat during approaches on hot humid days. Air entering the carburetor can drop 40-50°.
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What are the procedures for the timing of lowering the flaps upon leaving the gate? Most of the time they are always lowered before we leave the gate area. Every once in a while, it won't be done until we are well in route to the runway. I know from this thread that you wouldn't lower them if you are getting de-iced.
Our usual procedure is to lower the flaps to the takeoff position prior to leaving the gate area. Over the past few years, this has become a high visibility item in our procedures due to some instances of crews aborting takeoffs due to incorrect flap settings (the airplane generates a warning when power is applied for takeoff if the plane isn't properly configured).
If de-icing is planned, we leave the flaps up until we are ready for de-icing and then we select the takeoff setting prior to the application of glycol. I think at one time we left them up during de-icing and then set them prior to takeoff, but procedures are modified sometimes over the years according to the latest thinking on safest practices. I don't try to remember this stuff. When faced with winter weather and the potential for de-icing, I pull the manual out of the flight bag and turn to "Supplemental Procedures: Cold Weather Operations." This gives very detailed guidance on all this stuff, including special checklists for the de-icing process and guidance on any special takeoff requirements for the current weather.
I just don't encounter this stuff often enough to trust my memory on the fine points. In fact, I consider it a successful winter if I can avoid de-ice operations. I'm currently on Day #1 of a four day trip and it looks like I may have to deal with some of this on Sunday (I have three flights that day: ATL-JAX, JAX-ATL, ATL-SFO).
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Do you like the heads-up display in bad weather?
I have not yet flown a plane equipped with a HUD, though I've flown with many pilots who have and they all really liked it.