B737 winter ops questions
 

Flying with the worlds favourite Irish airline recently in light snow. Just been deiced, engines started and off we taxi. What caught my attention was just before we set off the flaps were set to full, before being retracted.
We entered the runway, backtracked and lined up and it wasn't until we came to a stop that flaps were set for take off. Got me a bit concerned..
Secondly we did what seemed like a high power take off and it was held on the brakes at full thrust for a good ten seconds.

What are the reasons behind these obervations? Thanks

Sounds like standard 737 winter ops procedures.

Flaps Up - Full - Up; checking that theres no jams in the mechanism due to ice that may have built up and that they're working ok through the full extension and retraction cycle.

Flaps up for taxi out is to ensure no contamination (e.g. snow thrown up by the wheels) gets jammed in the mechanism and to preserve the holdover time of the deicing fluid (tends to run off the flaps faster when they're in takeoff position). For this reason its desired to only set flaps for takeoff once takeoff is imminent.

Holding on the brakes while spooling up the engines; Boeing recommends a static run up, of 70% N1, for up to 30 seconds to ensure that any ice that may have built up on the fan blades during taxi is shed before commencing the takeoff roll.

So all in all, your crew did an excellent job, and I'd only suggest concern if they hadn't done any of what you describe. :ok:

Except for communicate with the people who get concerned about these things what they were doing and why. A simple PA to advise what is going on either during the boarding PA or just prior to line up is all it takes.

You want a pa for basically you!!?? 99.9% of pax's wouldn't know any different!

Seriously,

Go on, tell me you typed that without a smile on your face.

Along the lines of what I expected thanks for the detailed and informative replies.

Nope, in all seriousness what is the issue with making a PA prior to doing an engine run up? I wouldn't bother explaining about flap selections, but I will always try to make a PA to the passengers explaining why I am increasing the trust against the brakes before letting go and launching down the runway.

It's not hard. Those that know me on here will know that I am strongly in favour of keeping the passengers informed of what's going on during their flight, and the number of complimentary comments I get when passengers disembark reassures me that it is appreciated.