Flap Settings?

[XCLTM3 112]

Hi all fellow NGXers,

 

can someone with rw experience/knowledge in relation to the 738W NG point me in the right direction pls?

 

How does one know what flap setting to use for both t/o and landing? Is there a "definitive" chart or guide?

 

I understand that there are several factors/parameters at play (ie wind, weight, etc).

 

I'd like to be in a position of better understanding and application in this particular area.

 

Much appreciated.

 

Rgds,

[safir365 0]

Hello,

 

It depends of field limitations :

 

-A lower flaps setting will make your take off run longer, but your climb angle will be higher

-A Higher flaps setting will make your take off run shorter, but with a smaller climb angle

 

So again it depends of the field (TORA, ASDA....) and of the obstacles in the climb path. I have a real world calculator used but TUI it gives something like this :

 

[Chock 17,769]

I've got more real world experience with the products from Toulouse than the ones from Seattle, but I'll have a go at answering until someone who drives the 800 for real can comment more usefully...

 

Some of it will be down to company policy, which will be dicated in the SOPs (and will therefore differ between airlines), some the pilot's discretion, some of it will be geographical, and some will be FMC calculations, since your TOW and LW are going to vary, as indeed will airport altitude and surrounding terrain. So...

 

You would typically use flaps 5 for a take off where there are no adverse temps, specific climb out terrain clearance issues or density altitude considerations. More flaps would be used on hot days, or at high altitude or when the runway is of a limited length, since that will get you off quicker at the expense of more power, a less efficient climb out, wear and tear and (probably, but not always) more fuel burned, which is why it is on occasion influenced by company policy, although contrary to what might seem likely, running the engines at higher power will not always mean more overall wear and tear, since you might climb faster and therefore would be able to reduce throttle to cruise speeds sooner, so the engine would spend less time at higher temps and rotation speeds. Opinions vary on this, which is probably why company policies also vary on it.

 

Landing flaps are typically going to be 30 or 40, although more flaps will mean more noise and more fuel burned on approach since there is a lot more drag for the engines to overcome in spite of the lower speeds one could fly. The flight attitude on descent also differs quite a bit between flaps 40 and 30, thus the flight deck angle is different too of course, and that can affect visually acquiring the runway in IFR conditions a little bit, which is why Boeing say that flaps 40 is a better choice for high category landings, whereas they normally say flaps 30 would be the choice, since forwards and upwards visibility is enhanced with flaps 40, although with the HGS I suppose that matters a bit less these days. Nevertheless, the slightly slower approach speed would give you a little bit more time to spot things as well.

 

You should be aware that the flap relief load is pretty close to the flaps 40 placard speed on all 737s (except the 600), so not all NGs are flown the same way, for example, the 600's flap placard speeds are on the conservative side in order to prolong the life of its wing since it is somewhat different from the wings on other NGs, having thinner sheet metal at the tips and more strengthening because of that slimmer metal intially causing flutter, so is more prone to stresses and was one of the reasons why winglets were not certified for it. Its lower-powered engines also have a bearing on this too of course. Where the 800 is concerned, it is common for that variant to have somewhat higher reference speeds than other NGs, so don't be surprised if they seem high when you do your calculations.

 

Flaps 30 is what Boeing recommends for most landings since there is probably less tweaking to do to stay on the right approach speeds; flaps 40 is more likely to be stable so long as there is no significant gusting, although it will require more thrust and is probably not a great idea when going through a wind gradient because of the amount of inertia to overcome with a big amount of drag on the wing. Flaps 40 will mean different flare is required because of the deck angle difference, however as noted, some of the choice is down to gust variances on approach as well as the potential for encountering a wind gradient.

 

Since flaps 40 requires different flare, there is an altered risk of a tail strike on landing if you are used to flaring it from the 30 degree flap setting, because the same amount of pull on the stick for the two different flap settings would potentially mean the &@($* end would be getting closer to the tarmac, and this is probably at least worth consideration for the 800. On both the Airbus A320 family and the 737 NG family, the longer models are why maximum flap settings on landing are not always the recommended choice; both the A321 and the 737-900 have considerably more overhang behind the main wheels, and that could catch someone out if they are used to flying a shorter variant, which is in fact why the 900 has a beefier and more sophisticated tailskid arrangement. The 800 does not have that beefier tailskid, although it is apparently getting it, so you should probably be wary of flaps 40 on landing, and simply drive it onto the deck if you use that rather than trying to kill its desire to fly with too much flare, as that would mean a considerable change in flight deck angle and that might be tricky to get right, especially in a sim where your peripheral vision is not of much use.

 

I'm sure someone with experience of flying the 800 will be along to give you a more knowlegeable opinion on all this stuff though, so don't take my comments as gospel.

 

Al

[scandinavian13 5,192]

I've got more real world experience with the products from Toulouse than the ones from Seattle, [...]

 

Clever. Speaking of, if you set Flap position 1 in said products from Toulouse, is that setting variable (adjusted by the computers), or is it set degrees? I've always wondered that.

[Chock 17,769]

It is variable, the weight either on or off the wheels gives the first flap detent position two different selection modes. As far as I recall without digging out a manual, on the ground it gives you what is referred to as Flap 1+F, in the air it gives you Flap 1. The Flap 1 setting in the air, is 18 degrees of slats and no TE flaps, the Flap 1+F setting on the ground gives you 18 degrees of slats and 10 degrees of TE flaps.

 

Al

[scandinavian13 5,192]

It is variable [...]

 

Thanks. I figured it was more like a variable dial-a-flap controlled by HAL in the background. I see how it works now.

[Barnstormer1 0]

Flaps settings? Whatever the FMC performance page is recommending!

[scandinavian13 5,192]

Flaps settings? Whatever the FMC performance page is recommending!

 

Since when did it start offering recommendations?

[AirbusCG 52]

Hello,

 

It depends of field limitations :

 

-A lower flaps setting will make your take off run longer, but your climb angle will be higher

-A Higher flaps setting will make your take off run shorter, but with a smaller climb angle

 

So again it depends of the field (TORA, ASDA....) and of the obstacles in the climb path. I have a real world calculator used but TUI it gives something like this :

 

Where do you have it from?

[safir365 0]

Where do you have it from?

 

Classified :P

[idoleo2001 3]

Hello,

 

It depends of field limitations :

 

-A lower flaps setting will make your take off run longer, but your climb angle will be higher

-A Higher flaps setting will make your take off run shorter, but with a smaller climb angle

 

So again it depends of the field (TORA, ASDA....) and of the obstacles in the climb path. I have a real world calculator used but TUI it gives something like this :

 

 

Is this application available for use for simulation purposes?

[safir365 0]

Is this application available for use for simulation purposes?

 

negative, it's a tool integrated in the laptop which is given to TUI crew

[idoleo2001 3]

negative, it's a tool integrated in the laptop which is given to TUI crew

 

Thanks!