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unb5
23rd Nov 2009, 23:27
Had a takeoff today from a shorter field- 2000m in heavy rain and strong crosswind gusts up to 31kts. The performance computer gave an optimum flap setting of flap 20 which I thought was excessive is there any question of useing a lesser flap setting is does one always choose optimum.

unb5
24th Nov 2009, 00:01
My question is whether or not one can select another flap setting other than what the computer spits out as optimum given the weather and conditions. Waiting in the sim not an option.

Pugilistic Animus
24th Nov 2009, 01:09
it depends on the max RTOW for the TO condtion as predicated on that flap setting---only if you know the limitations can you choose an alternate flap setting,..if that was the only setting available for that RWY---- I would not go fooling around with the TO performance in the RTOW:\

so is another allowable Flap setting scheduled or not?

stilton
24th Nov 2009, 03:45
I have been using Flaps 25 in for landing in strong / gusty crosswinds on the 757 for years.



Runway length has never been a factor and the increase in controllability is well worth it.



As soon as I saw this lower flap setting demonstrated in strong winds I was a convert, it makes for a far nicer handling Aircraft.

p51guy
24th Nov 2009, 04:46
Sometimes you just need to adjust your flap setting to the conditions you feel are important. You can always change flap settings if you have data to back it up. I have flown 757's with writeups of max power setting going to red line. I flew out of a critical airport, TGU, and didn't want to stress the engine so did a reduced power take off at a higher flap setting to use less power. They can try that max power down at sea level with a 10,000 ft runway. Hopefully you can also get data for other than company settings.

unb5
24th Nov 2009, 07:24
according the computer all flap settings where available for the takeoff but flaps 20 was given as the optimum. The runway was 27 and the length 2000 metres with a wind 220 degress 19 gusting 31 and qnh 1009. zero fuel weight 74.9 and fuel 13,600. Heavy rain but airfield had no standing water. The question is for control in gusty conditions what flap setting would be the best ?

ab33t
24th Nov 2009, 19:00
Well how long is a piece of string , as long as you are in control and the plane handles in the prescribed conditions you are good to go. As said above if things should go pear shaped ........

oceancrosser
24th Nov 2009, 19:58
7K+ hrs operating the 757 out of a windy gusty base albeit with ample runways, I prefer to use flaps 15 to reduce the t/o roll. Flaps 20 I only use when required by runway length.
I am not a fan of using flaps 25 for landing, although at high landing weights (high Vref) with the bug speed with approaching 160 kts (20kts increment for wind and gusts) and the potential for flap load relief if you use flaps 30, is the time to do it.

middlepath
24th Nov 2009, 19:59
For the condition you have mentioned flap 20 is better than lower flap, similarly in windshear and contaminated condition as you may well know.

unb5
25th Nov 2009, 17:04
Thanks Ocean crosser and P51 and not just because you agree ! our ops manual says nothing about the selection albeit respecting RTOW and runway length. My point with the instructor was all about choice as well , operating in given conditions etc. I realize too that a selection other than what might state as optimum is a risk but hey thats our job to analyze. Thats why they have captains with experience otherwise everyone would be in the left seat. Do you know of any Boeing recomendations or literature concerning crosswinds other than what we find in the FFPM and training manuals ?

Spooky 2
25th Nov 2009, 17:44
I believe that the tail strike distance is greater with the larger flap settings. Since strong crosswinds are frequently a factor in tail strikes I suppose one might consider the larger flap setting a conservative measure. I doubt however that it is factored into any OPT or BLT performance calculations. Been wrong before so don't take that statement to the bank!

oceancrosser
25th Nov 2009, 23:03
On the 757/767 there is less probability of a tail strike with flaps 15/20 than with flaps 5. Same goes for landing, less of a likelyhood with flaps 30 than flaps 25.

Spooky 2
26th Nov 2009, 15:07
What is it that is not true? Are saying that larger flap settings on the 757 do not give you greater tail clearance on rotation?:}

Spooky 2
27th Nov 2009, 00:05
Sorry I still dodn't understand you post but never the less I think we all agree that 20 flaps give more tail strike protection than say flaps 5 or 15. I have never seen a wing tip strike on a 757/767, but that does not that ther have been any.:ok: