View Full Version : Cold Weather Procedures B737NG

10th Oct 2003, 05:02
This question relates to the Supplementary Procedures (SP) for Cold Weather, defined as any visible moisture below 10 degrees C, for the B737NG (and presumably similar for other types as well). The SPs are obviously written for full on ice and snow as well as for a rainy day with a temperature of say 8 degrees. The trouble is, there is no distinction between these two extremes and I am wondering what SPs other operators do when it is raining and 8 degrees, and at what stage they revert to the full SPs for Cold Weather.

Example 1: In the SPs, for the After Engine Start there is a requirement to do a flight control check and to run the flaps fully down and fully up, before taxiing. It seems to me that this is done before taxiing to prevent running the flaps and doing the controls while taxiing over slush/snow - fair enough. However, the requirement to do it at all seems unnecessary with rain at say eight degrees C. Under what circumstances/conditions do other operators do the flight control check and flap movement check after start?

Example 2: In the SPs, for the After Landing the stab trim is set to 0 to 2 units to prevent water freezing over the stab limit switch. At first I thought this may only be applicable below 0 degrees C, but then consider the scenario where the aircraft skin is cold soaked after a long flight (we have aux tanks that allow 12 hour flights - BBJ) and landing in the rain. What do other operators do?

Example 3: In the SPs, there is a flight control check (but no flap check) in the Cockpit Preparation (i.e., before engine start). This is only done if the aircraft is exposed to freezing rain, snow, or any other condition that may lead to flight control binding. If you do this, does this replace the flight control check in example 1, or do other operators do two flight control checks, both before and after engine start?

20th Oct 2003, 18:56
Well, with winter coming on I was hoping for a reply by now ...

One further example:

Example 4: The engine run-up to 70% is supposed to be done every 30 minutes. When is the first one done, 30 minutes after engine start, or immediately?

21st Oct 2003, 05:33
HI!!! Im not a B737 pilot, but I think I can help you with the engine run-up procedure.
Periodic run-up must be performed when running the engine at low power (i.e. while taxying), because even though ENGINE A/I is on, the engine is not protected against ice build up on the spinner, fan blades and low compressor inlet stator.
When increasing N1 to 70%, ice is shed before it accumulates to the amount where it can damage the engine if it sheds when the engine is spooled -up for take off.
Thus, if your engine procedure call for 30 min periodic run-up (it seems very very long), this must be performed 30 min after engine start if you are not already airbone (doubtfull)