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767-300ER
24th Jan 2018, 13:00
I was wondering if other 737 Max or NG operators have the requirement to cycle the flaps from UP to 40 and back UP after deicing the aircraft. I have watched 737 NGs going through deicing and never seen them cycle the flaps.

The following is from a 737 Max Airframe deicing checklist

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


So if you are deicing to remove frost from the upper surface on the wing, why is this necessary? It seems over the top and is quite time consuming when de-icing facilities are trying to get aircraft through the facility as quickly as possible.

Anyone have any explanations/answers? Is this procedure unique to the Max?

nicolai
24th Jan 2018, 13:09
I don't know if it's unique to the 737 Max. De-icing fluid (especially types II and IV) can accumulate in flap mechanisms and jam them.
For example see section 9 of EASA Safety Information Notice No. 2008-29 (https://www.skybrary.aero/bookshelf/books/944.pdf). So there is a reason to exercise the flaps.

Denti
24th Jan 2018, 13:57
Back when i was still flying NGs that was the procedure we had as well. So not new for the MAX.

wiedehopf
24th Jan 2018, 14:23
this might be a stupid question but why is it time-consuming for the deicing facility?

don't you just do it on the way to the runway?

767-300ER
24th Jan 2018, 15:21
Thanks for the EASA notice...however, the generic advice about fluid rehydration would apply to all aircraft types and not unique to the 737.

(ii) Re-hydrated fluid residues.
Repetitive application of thickened de-icing / anti-icing fluids may lead to the
subsequent formation / build up of a dried residue in aerodynamically quiet areas,
such as cavities and gaps. This residue may re-hydrate if exposed to high
humidity conditions, precipitation, washing, etc., and increase to many times its
original size / volume. This residue will freeze if exposed to conditions at or below
0° C. This may cause moving parts such as elevators, ailerons, and flap actuating
mechanisms to stiffen or jam in flight.


Other Boeing types (767,777,787) do not have this advice to cycle the flaps, and as far as I know, Airbus (319/320/321) do not require this step.

767-300ER
24th Jan 2018, 16:50
Yes you can accomplish the flap cycle on the way to the runway. Boeing doesn't address how to accomplish this flap cycle while taxiing on slush or snow covered taxiways. Boeing suggests delaying the final t/o flap selection on contaminated taxiways, so I would think that Boeing wouldn't recommend a cycle to Flap 40 on snow/slush/ice covered taxiways (which stands a much better chance of getting contaminants on the flaps than a normal t/o setting of Flaps 5).

Caution!
Flap selection should be delayed if extended taxi through slush or snow conditions is anticipated.

172_driver
24th Jan 2018, 17:24
We don’t cycle the flaps, however wait with flap extension until reaching the runway if snow is falling. That is to avoid precipitation on areas not treated as the flaps come out.

Scandinavian operator. We often do several de-ice procedures a day. Not heard of any problems with rehydrated fluids. We log it in the book, so perhaps maintenance has an inspection cycle for it?

fab777
24th Jan 2018, 17:33
B737 NG. SOP is: deicing, then cycle flaps, then select TO flaps or, if taxiways are contamined, select flaps UP, then taxi. We do it this way.

SR-22
24th Jan 2018, 22:05
At least in my outfit B737NG and B737MAX yes as per FCOM to cycle flaps to 40 and up again after de-icing. Scandinavian operator.

vapilot2004
25th Jan 2018, 00:09
De-icing operations, cold weather taxi on sloppy tarmac or in cold precip require flaps UP. Also for our group, cold weather flap cycling (0-40-0) is always done before taxi.

Slow throttle application is also SOP around slushy macadam and on or near the deice station, although if applied too slowly, I believe one ends up throwing more wash than if the levers are brought up smartly.

president
25th Jan 2018, 01:56
It’s a cold weather flap check that must be done, de-icing or not. It’s the supplementary procedure for cold weather operation.

You can delay it until de-icing is completed. But that’s not to say you don’t do it without de-icing.

Skyjob
25th Jan 2018, 15:11
As in cold weather operation there is a risk of movement being impaired due to the (re)freezing of contaminants, the freedom of movement check makes a lot of sense.

Considering the checklist is done regardless if the aircraft landed 30 minutes ago or 30 hours, it is very sensible to do this. Contaminants could have accumulated in many cavities, including the flap fairings, either due landing on a contaminated runway, taxiing in on a contaminated taxiway, or due (winter) precipitation/deposits being washed off by deicing fluids. Why not ensure these vital flight controls have the ability to move freely, same for ailerons, rudder and elevator.

sonicbum
25th Jan 2018, 16:13
Fully agree with the above and I also would like to add to make sure that during this check at least one pilot keeps his eyes on the trailing edge flap indicator for any sign of flaps getting stuck on their way to 40 and backwards and in case promptly move the flap lever to the indicated position or the closest setting.

172_driver
25th Jan 2018, 21:12
I am aware of the SP. Though, in the FCOM we use it says nothing about cycling the flaps. As far as I remember the SP was about cycling the flaps in freezing conditions, rather than post de-ice.

If we expect ice in the flap arrangements after landing we leave the flaps extended until inspected. If taxiing through slush or snow we may taxi out with flaps retracted. Also, if snow is falling we leave them retracted until holding point.

Not saying you should hurry or not check properly, but if we were to apply the same thorough procedure as in my previous airline we’d definitely be running behind schedule...

767-300ER
27th Jan 2018, 13:40
So what is unique about the 737 that requires this procedure?

Not done on 757, 767, 777, 787 or Airbus 318/319/320/321....As far as I know.

tdracer
28th Jan 2018, 07:47
There are some pretty fundamental differences between the wing/slats/flaps on the 737 relative to the other Boeing 7xx wings. No first hand knowledge here, but I'm guessing the "aerodynamic quiet" places can be more of an issue on the 737 wing.

EIFFS
28th Jan 2018, 18:18
Procedure is the same for NG & MAX per Boeing FCOM, yes it takes a few minutes between 5 - 0 is very slow, but you’ve already spent 6 minutes starting the engines on the max

vapilot2004
30th Jan 2018, 00:20
I've been told the flap PDU, torque tubes, and drive screws are more exposed to the elements on the 737 compared to its bigger brothers. The mechanisms are also much closer to the ground than any other Boeing aircraft flying today. There is, at minimum, about a meter in height difference here.

Skyjob
30th Jan 2018, 08:32
It may also have to do with the proximity of those areas to the ground when compared to other models, just guessing...

galdian
30th Jan 2018, 09:49
In previous company (NG"s) always surprised me an otherwise good to excellent Bad WX Ops pamphlet had this flap exercise after pushback because:

- having just de-iced and anti-iced the wings/slats and gaps etc will be as clean as they can get;
- exercising if precipitation/snowing means allowing ice into the flap gaps to be crunched after retraction and freeze further even more on taxi out.

My procedure was to not do the check after pushback and taxi out flaps up, just before take-off exercise to 40 degrees, back to 5 degree (only company setting) and if all OK take off; any problems taxi back for de-icing etc.

Discussed with a checkie type who only smiled and said "as long as it is done somewhere at PIC discretion is OK", management did not want to buy into any talk about (maybe IMHO) changing the location for the check - so some crews would be stuck with "the C/L says MUST be done after pushback" mentality which didn't appear the best/safest option.

Cheers.

sonicbum
31st Jan 2018, 10:36
In my opinion if Your company approved and published a certain procedure, most likely with a no objection from Boeing or actually following directly a Boeing procedure, than it must be followed unless a deviation is required in the interest of safety, but again in my opinion this should be limited to an unlikely and unique scenario and not become a parallel SOP. We all know the threats associated to "don't worry we'll do it this way, we'll be ok" type of procedures. Anyway I am not pointing any finger and I am pretty sure You had loads of good reason to deviate from Your SOPs, but as pilots we should push for changes all together if something does not look right rather than finding alternative paths.
Just my 2 cents.

de facto
9th Mar 2019, 18:41
Cold temperature definition for a scandi is what? Sub zero? then recycle flaps?
Cant find boeing definition of cold temp.( sub 3C? )

ManaAdaSystem
9th Mar 2019, 19:01
I have flown the NG since it came, and I have deiced more times than I care to remember.
Show me where Boeing says this is a procedure after deice. I have never seen this written anywhere and it has never been in our SOP. And I say Boeing procedure, not a procedure that is put in the FCOM at the operators request.
It goes a long way to explain why some operators use forever to get out of the deice area while there is a long line of aircraft waiting to get deiced.
The SP for cold weather operations USED to include this procedure (not associated with deice) along with turning the nosewheels full right/left.
It’s not there anymore.

Never had a flap/slat problem on the NG either.

Chesty Morgan
9th Mar 2019, 19:06
It's in my SP for cold weather.

FlyingStone
9th Mar 2019, 21:26
Show me where Boeing says this is a procedure after deice. I have never seen this written anywhere and it has never been in our SOP. And I say Boeing procedure, not a procedure that is put in the FCOM at the operators request.It goes a long way to explain why some operators use forever to get out of the deice area while there is a long line of aircraft waiting to get deiced.
The only thing that matters is what is written in the operator's FCOM/OM, as that one is approved by the authority. The Boeing procedures alone aren't.

Don't see the issue with taking time to do all the checks before starting taxi, better safe than sorry. Other than a minute or two delay, what's the harm for the aircraft behind? They have to be de-iced anyway, so it's not like it's eating into their holdover time.

ManaAdaSystem
9th Mar 2019, 22:02
The only thing that matters is what is written in the operator's FCOM/OM, as that one is approved by the authority. The Boeing procedures alone aren't.

Don't see the issue with taking time to do all the checks before starting taxi, better safe than sorry. Other than a minute or two delay, what's the harm for the aircraft behind? They have to be de-iced anyway, so it's not like it's eating into their holdover time.

Of course you have to follow your company’s SOP, but 2 minutes + 2 minutes + 2 minutes ++++.
Better safe than sorry? 20 years of deicing without this procedure and no problems should mean something.
This procedure (in connection with deiceing) has never been in our FCOM.

Deice in snowy weather, then select FL40 and expose all untreated areas to the snow? Retract. Doesn’t sound like a good idea to me.
You are not Ryanair, by any chance? Their aircraft are like obstacles in the deice flow.

ManaAdaSystem
9th Mar 2019, 22:08
It's in my SP for cold weather.

Boeing or company?
With or without deice?
The flap procedure was in our FCOM and was related to cold weather. If I’m not mistaken, we are talking temperatures below -30 C.
I have only done that once. Now my FCOM only calls for take off flaps.

Chesty Morgan
9th Mar 2019, 22:23
Boeing. Not related to de-icing just cold weather ops. Take your pick on the temperature...

It's the before taxi procedure so if you've taxied to a remote de-icing area you have already done the flap check. No need to repeat it.

ManaAdaSystem
9th Mar 2019, 22:39
Boeing. Not related to de-icing just cold weather ops. Take your pick on the temperature...

It's the before taxi procedure so if you've taxied to a remote de-icing area you have already done the flap check. No need to repeat it.

Strange. I believe you can opt for various Boeing SOP’s, (feel free to correct me if I’m wrong) but I think this should be standardized.

FlyingStone
10th Mar 2019, 08:46
Better safe than sorry? 20 years of deicing without this procedure and no problems should mean something.This procedure (in connection with deiceing) has never been in our FCOM.
Equally, other operators might have no problems for the past 20 years with procedures different to yours. Why change it if it works?

Personally, I don't agree with all the flaps cycling and all. But it's the only approved procedure by my employer, is not unsafe (although time consuming), is what is expected from us and they pay my paycheck at the end of the month, so...

I believe you can opt for various Boeing SOP’s, (feel free to correct me if I’m wrong) but I think this should be standardized.

Operator can choose their own SOPs, if they manage to get it approved by their authority. And if they are using a Boeing-tailored FCOM, there will be a statement there that Boeing takes no responsibility for the modifications.

ManaAdaSystem
10th Mar 2019, 09:46
Equally, other operators might have no problems for the past 20 years with procedures different to yours. Why change it if it works?

Personally, I don't agree with all the flaps cycling and all. But it's the only approved procedure by my employer, is not unsafe (although time consuming), is what is expected from us and they pay my paycheck at the end of the month, so...



Operator can choose their own SOPs, if they manage to get it approved by their authority. And if they are using a Boeing-tailored FCOM, there will be a statement there that Boeing takes no responsibility for the modifications.

If I can simplify procedures, reduce wear and tear, and save time, that is a win to me.
Can you ask your fleet captain where this procedure comes from?
If Boeing says you have to do this, I wonder why it’s not in our FCOM.

Sig229
13th Mar 2019, 04:17
At my US operator we do not cycle the flaps after deice, nor do we wait to select flaps until just before takeoff. Our procedure is to deice with flaps/slats set for takeoff, unless the aircraft arrived with contamination in which case the flaps would only be brought up to 15 after landing to reduce the risk of damage on retraction. We do cycle the elevators 3 times to ensure no fluid is trapped from the spraying, but I haven't seen anything in any of our manuals about cycling the flaps. This is for the 700/800/Max8.

Skyjob
13th Mar 2019, 16:17
I believe these procedure were developed by company, not Boeing, with NTO (No Technical Objection) from Boeing.
Several companies do it, several others do not, so it's unlikely to be a Boeing requirement.
Having operated in companies on both sides of the fence:
- yes, it is time consuming, in fact in certain conditions so much so that holdover time can get compromised if copying with procedure;
- no, it should not be omitted if possible as there is a method to the madness;

Either way, good airmanship should be used when deciding to follow procedure:
- yes, it would make sense to depart and not return to gate to get deiced again as holdover time is now compromised having meticulously followed procedure (ps does your company allow you to continue checklist or do you have to wait for cycling of flaps, as this can significantly increase the time required to complete the checklist in its entirety);
- no, it would not make sense to forego on this procedure if eg freezing rain has fallen on a sub-zero airframe;
- no, it would not make sense to complete this procedure if only light frost was observed prior to flight, no (visible) moisture was present during time on ground nor precipitation, and temperatures are increasing above freezing...

A better ruleset would be very welcome, as the current procedures established by some airlines are way too restrictive, though from safety types on here very likely applauded for thoroughness of company.

Jumo
14th Mar 2019, 06:50
LN-DYM in Kittilä 737 almost stalled when suddenly trimmed up for 12 sec.

Similarities to Flydubai in Rostov ?

In Kittilä the cause is reported the de-icing fluid ingress, but does it explain the trimming ? I have no background on flying ( only as passenger) but it seems strange that pilots did fly back home after such incident and reported only afterwards ? How was the ice then found to be the cause, days later ?

I can not post the link to aibn but google it with :
"Report on the serious aircraft incident during approach to Kittilä airport in Finland (EFKT) on 26. December 2012 with a Boeing 737-800, LN-DYM, operated by Norwegian Air Shuttle ASA"DescriptionDuring approach to Kittilä (EFKT) in Finland on 26 December 2012, LN-DYM, a Boeing 737-800 NG on Norwegian Air Shuttle's (NAS') air service NAX5630 from Helsinki airport (EFHK), came close to stalling. The outcome of a stall would most likely have been catastrophic, primarily because the elevator system at that time did not function normally. The elevator system worked only at a ratio of 1:250.

AIBN's investigation has uncovered that de-icing fluid had ingressed the tail section and frozen on three or four of the input cranks for the aircraft's two elevator Power Control Units (PCUs) and thus prevented them from functioning as intended."

Skyjob
14th Mar 2019, 21:07
LN-DYM in Kittilä 737 almost stalled when suddenly trimmed up for 12 sec.

Similarities to Flydubai in Rostov ?

In Kittilä the cause is reported the de-icing fluid ingress, but does it explain the trimming ? I have no background on flying ( only as passenger) but it seems strange that pilots did fly back home after such incident and reported only afterwards ? How was the ice then found to be the cause, days later ?

I can not post the link to aibn but google it with :
"Report on the serious aircraft incident during approach to Kittilä airport in Finland (EFKT) on 26. December 2012 with a Boeing 737-800, LN-DYM, operated by Norwegian Air Shuttle ASA"Description

During approach to Kittilä (EFKT) in Finland on 26 December 2012, LN-DYM, a Boeing 737-800 NG on Norwegian Air Shuttle's (NAS') air service NAX5630 from Helsinki airport (EFHK), came close to stalling. The outcome of a stall would most likely have been catastrophic, primarily because the elevator system at that time did not function normally. The elevator system worked only at a ratio of 1:250.

AIBN's investigation has uncovered that de-icing fluid had ingressed the tail section and frozen on three or four of the input cranks for the aircraft's two elevator Power Control Units (PCUs) and thus prevented them from functioning as intended."
The aircraft type has had its deicing procedures amended after it was found fluid could enter cavities in elevator sections which was found to be a factor.
It is not related at all to the Rostov incident, which happened because of pilot spacial orientation.

Report AIBN here (https://www.aibn.no/Luftfart/Avgitte-rapporter/2015-01-eng?pid=SHT-Report-ReportFile&attach=1)
Report IAC (preliminary) here (https://mak-iac.org/upload/iblock/19b/Interim%20Report%20A6-FDN%20(en).pdf)

PlanetEarth
30th Mar 2019, 17:06
I've flown in snow, sleet, freezing fog and any other type of contamination in the frozen north daily, but we have never used this flap cycling procedure.
Looking at our companies fcom, I can't find any section in sp requiring a cycle to 40.

karlson737
11th Dec 2021, 06:43
“Move the flaps from Flaps up to Flaps 40 back to Flaps up (i.e., full travel) to ensure freedom of movement” SP.16.6
So. They want we do full travel to Flaps 40 when :
“Icing conditions exist when OAT (on the ground) or TAT (in flight) is 10°C or below and any of the following exist:
• visible moisture (clouds, fog with visibility of one statute mile (1600m) or less, rain, snow, sleet, ice crystals, and so on) is present, or
• ice, snow, slush or standing water is present on the ramps, taxiways, or runways.” SP.16.2

IMHO. It is hard to understand why we have to cycle to 40 if OAT is 9°C, visibility of one statute mile (1600m) or less, especially if no rain, snow, sleet, ice crystals is present.

aviary1973
17th Dec 2021, 16:31
Boeing response: In cold temperature conditions, trapped water may freeze and/or lubricants may thicken. The requirements to cycle the flaps is intended to detect any blockage or contamination of the flap system which might be the result of internal frozen contamination. This check should be accomplished whenever the airplane has been exposed to snow, freezing rain or other conditions which could restrict flight control movement, and when the temperature is cold enough that the fluid cannot melt completely/

Matey
17th Dec 2021, 22:57
“Move the flaps from Flaps up to Flaps 40 back to Flaps up (i.e., full travel) to ensure freedom of movement” SP.16.6
So. They want we do full travel to Flaps 40 when :
“Icing conditions exist when OAT (on the ground) or TAT (in flight) is 10°C or below and any of the following exist:
• visible moisture (clouds, fog with visibility of one statute mile (1600m) or less, rain, snow, sleet, ice crystals, and so on) is present, OR
• ice, snow, slush or standing water is present on the ramps, taxiways, or runways.” SP.16.2

IMHO. It is hard to understand why we have to cycle to 40 if OAT is 9°C, visibility of one statute mile (1600m) or less, especially if no rain, snow, sleet, ice crystals is present.

The Boeing FCOM Supplementary Procedures / Adverse Weather / Cold Weather Operations section states the following: “Considerations associated with cold weather operation are primarily concerned with low temperatures AND with ice, snow, slush and standing water on the airplane, ramps, taxiways, and runways.” The OR quote above is for the more general definition of icing conditions. Thus the Boeing trigger for a full flap check is Icing conditions AND contaminated ramps taxiways etc. My former employer TUI UK narrowed this down in their Supplementary Procedure with a temperature requirement of <1 degree C before cycling the flaps. In both the Boeing and Company SPs this forms part of the Before Taxi Procedure.