View Full Version : B737 cold weather operations

27th Sep 2012, 14:14
Evening everyone.

Tried to contact several Alaska airlines pilots on FB to clarify the issue, but noone answered. North located airline experience is what we need to teach from.

Our SOP uses standart Boeing ops, as a result - lots of questions and doubts are up in the air :)

1) what is the reference temperature for 0-40 flaps movement in your SOP? We use 0°C, but many fellows find this value silly and so forth...
2) do you guys turn the probe heat on preflight when its for ex. -2 and dry&sunny?
3) how many ref temperatures do you use? We have 8 and consider its too much to memorize everything easily.

I will share more questions later on. Hope, right guys come here to help out. Cheers.

28th Sep 2012, 02:55
I suggest for litigation purposes you FOLLOW BOEING proceedure.

Any questions? Ask you fleet technical Pilot or get him to contact Boeing for clarification. :ok:

28th Sep 2012, 08:24
1) Since the check is done for freedom of movement in freezing conditions i would use 0° C as well, as does my company. And of course whenever deicing is needed, after deicing is finished, but usually the temperature is below 0° by then.

2) Per SOP we do, just before reading the preflight checklist. Newer Airplanes have an AUTO-Position instead of off, they start to heat up on their own whenever an engine is running.

3) Ref speeds are determined by the EFB performance program. Therefore we don't have a fixed number of speeds to memorize. If the runway is both contaminated and has degraded braking action we have to calculate both values and take the more limiting one.

28th Sep 2012, 16:43
Looking for ref speed or ref temp?

28th Sep 2012, 18:34
3) by saying refference temperature, i mean different temperature values, that we use as a trigger. We have +10, +5, +3, +0, -15, -18, -35, -40 and looks like it's too complicated. SOP is being frequently changed, so, we hope to improve something about it.

28th Sep 2012, 20:03
Denti, thanks for answer, could you please detalise 2nd question? What is it said about weather conditions (temperature and moisture) regarding probe heat?
Like, +9, sunny, dry. Are you supposed to turn em on before checklist? That's what we do now! :ugh:

28th Sep 2012, 21:00
Alaska doesn't do a check for full flap travel. AS SOP calls for delaying flap extension if taxiing through slush, etc., and it also calls for not fully retracting flaps after landing if encountering significant icing while on approach.

I'll add it to the list of differences between AS SOP and Boeing SOP.

28th Sep 2012, 22:37
As for the second question, no, at +9°C, sunny and dry we would not switch on the pitot tubes on the stand, only after engine start (e.g. normal procedure, not supplemental normal).

For reference temperatures, sorry for my misunderstanding there, we use +10 (max OAT for wing/engine anti ice), +3 (runup required at or below if anti ice is needed), 0 (below cold temperature correction is needed except for corrected approaches (all baro VNAV approaches) and -40 (cold soaked engine).

IC, according to "my" version of the supplemental normal procedures cold weather the flap deployment should be delayed until line up if taxying through slush etc is expected, if the wings are contaminated and have to be deiced keep the flaps up until deice is done. So when to do the full travel check depends on outside conditions and the need for deicing. For flap retraction after landing it tells us to max retract them to F15 if ice acummulation is possible due to prolonged operation in icing conditions with flaps extended, or when operating on a contaminated runway/taxiway.

29th Sep 2012, 13:26
Thanks for answering.

So, what are the requirements for earlier probes heating? Temperature only or moisture/water/slush also?
-5 and dry&sunny for example?

Guys, who else doesn't' check flaps freedom movement?

21st Jan 2013, 22:04
Hello everybody,
I would ilke to ask that if a runway covered less than 10% slush with 5 mm depth.The term contaminated is definde as 25 % of runway.Do we accept it contaminated or not?Because it is less than 25%?Which weight reduction table do we have to use?

sudden Winds
23rd Jan 2013, 02:15

The 0-40 flap cycle does not depend solely on temperature. It depends on how long the airplane sat there before engine start as well.
The probe heat can be turned on during the cockpit prep during cold weather ops, nothing will happen to them. You donīt turn them off when you are number 6 for takeoff on a 40°C day, no need to not turn them on during preflight cold wx.

Keep in mind that if you are going go thru a supplementary procedure and start deferring this, delaying that, not doing this, etc, you risk forgetting something important, while there is little to no benefit from the other exceptions or modifications to what the procedure says.

Donīt forget there is a difference between cold weather operation, and icing conditions. That is probably the one thing you need to keep in mind when deciding what items of a cold weather supp procedure you will consider unnecesary, such as the flap cycle, or early probe heat.

Hope it helps.

23rd Jan 2013, 03:53
Check flap travel after engine start? 0 to 40? In airline flying? Never.

23rd Jan 2013, 10:02
Flying all kinds of 737s from 1991 in all kinds of weather and never heard of anybody doing 40 flaps check, but allways willing to learn more...???:uhoh:

Too Few Stripes
23rd Jan 2013, 12:07
So you guys haven't been doing it then???

Boeing 737-800
SP 16 - adverse weather, before taxi procedure

Flaps ............................................................ ........................Check F/O

Move the flaps from Flaps up to Flaps 40 back to Flaps up (i.e., full travel) to ensure freedom of movement.

23rd Jan 2013, 12:13
How about you contact First Air and ask this question? today the warmest place they will be landing at is Minus 31 Deg C, they do it every day 365 days a year.

23rd Jan 2013, 12:23
Our Supplementary Normals for cold weather ops

Flap 0 to 40. Then delay extension if taxi route is to take you through the usual muck.

Probe heat on after normal preflight procedure.

23rd Jan 2013, 13:07
Move the flaps from Flaps up to Flaps 40 back to Flaps up (i.e., full travel) to ensure freedom of movement.
And what would happen on a wing full of ice?

23rd Jan 2013, 13:26
And what would happen on a wing full of ice? - it would not be done. One trusts, incidentally, RTO, that you would not be contemplating flying anyway? It is a check AFTER wing de-icing. In 2004 Astraeus was doing the check.

The retraction to >10 degrees after landing is VITAL if there is any possibility of any accumulation of frozen stuff anywhere in the flaps. Particular area is using reverse on a snow/ice contaminated runway when it is more than possible to 'pack' the LEDs with crud. Leaving them at F15 means they will not move.

23rd Jan 2013, 17:16
Moving away from flaps, but staying in the 'cold Wx ops' scene:
Opinions please: In freezing conditions on the ground, and especially if there is precipitation, I used to start one engine and then switch on EAI for it (keep it warm and cosy on a cold day) and then start the 2nd engine. I was in my 1st sim recurrent training in a newly joined airline when I was rapped over the knuckles in the sim by an F/O SFI and told" we don't do that here." Ah, "but FCTM says that EAI has to be on when icing conditions are anticipated or encountered. It is snowing." Water off a ducks back. Lo & behold the new FCOM SOP came out and it stated," EAI will be switched on after both engines are started."
Opinions & comments?

de facto
23rd Jan 2013, 17:25

When you do a supp procedural engine start,(ie cold w)will the procedure tell you to switch on the TAI after both engines start or one at a time?:8
I personally select TAI during the after engine start flow.I am pretty sure it is standard.

23rd Jan 2013, 19:06
we are not doing it, as here on bussiest airports it is not even permitted to set take off flaps before taxing, not to injure somebody from ground stuff moving arround aircraft during/after pushing back. Then having a precipitation of any kind during freezing conditions, we are allowing it to reach the flap areas, which would normally remain hidden. If doing it after deiceing completed, just having a clean concept achieved, by letting untreated areas exposed to precipitation, it will become iced and than we would have to go back for deiceing...this is why four european airlines I was flying for, had omitted this test, except in cold weather, below 0°C and no moisture, surfice accumulation or precipitation present, at remote airports on pilots discretion...which in fact meant seldom or never, with the accent on never ;)