B737 Holding in Icing Conditions with Flaps extended

[Taggert]

Hi all.

Can anyone elaborate on the B737 limitation of holding in icing conditions? Is it predominantly concerned with ice accumulation on the deployed flap surfaces(and ensuing decrease in lift and reduction of stall margins)and icing of the flap jack screws?

How would this be any different to having a flap problem on departure, and then diverting in icing conditions with the Flaps still extended?

Cheers,

Taggert

[flypaddy]

My understanding is that the rate of ice accretion is hugely increased on a wing with leading/trailing edge devices deployed when compared to a clean wing. The advice to avoid icing conditions when configured is true for all aircraft I have flown and is not specific to the 737.

I recall an old video of an experiment which was carried out (possibly by Boeing or NASA) following an accident caused by icing. A leading aircraft sprayed water over the wings of a 757 at altitude. They were shocked at how quickly ice built up when the slats/flaps were deployed and this led to the current guidance.

[Jwscud]

I stand to be corrected but I believe most of this came out of the Roselawn ATR accident (https://www.faa.gov/lessons_learned/transport_airplane/accidents/N401AM) where they suffered a LOC-I due to icing building up ahead of the ailerons.

The difference with a flap problem on departure is it is a system malfunction rather than planned operation. If you have a flap malfunction on departure the limitation applies - try to exit icing conditions as quickly as possible. The combination of a flap malfunction and extensive icing conditions you can’t exit would be challenging but awareness of the limitation should guide your decision making.

[safetypee]

Perhaps something to do with this ?

'Only the leading edge slats have WAI (ie not leading edge flaps). The NG series outboard slat has no wing anti-ice facility (see photo) believed to be due to excessive bleed requirements.'

Ice & Rain (http://www.b737.org.uk/iceandrain.htm)

[Trossie]

WHY would anyone want to hold with flaps extended?????

Icing conditions or not icing conditions?

Flaps are extra drag. If you are holding you don't want extra drag. Flaps are extra drag. FULL SYOP.

[Chesty Morgan]

WHY would anyone want to hold with flaps extended?????

Icing conditions or not icing conditions?

Flaps are extra drag. If you are holding you don't want extra drag. Flaps are extra drag. FULL SYOP.
There used to be a hold at Chambery which has a maximum holding speed below min clean speed for many types. That's one example.

[stilton]

There used to be a hold at Chambery which has a maximum holding speed below min clean speed for many types. That's one example.


There was a similar hold in the Northeast US, we would not accept holding there in icing conditions and I wouldn’t hold anywhere else unless in the clean configuration


Never flew the 737 but several other jet transports and it was the same with all of them

[nig&nog]

I’m interested in an answer to this question because from what I can see if you have a flap issue on takeoff or landing (B737) and go and hold to run the checklist you can’t if it’s in icing conditions. But on the other hand the same scenario most probably at the same speed under vectors in icing conditions is perfectly fine. The only thing I can think of is that in a hold you are generally turning every 2-3 mins depending on where you are (world wide) and that may lead to ice accumulation at a faster rate than radar vectors which generally would have less turns possibly.