View Full Version : Flaps 2 origin 737?

10th Oct 2010, 17:14

couldnt find something in the web:

When was the flaps 2 setting needed and which practical value does it have today and why doesnt boeing change that flapsetting? Cut it out? certification?



10th Oct 2010, 17:21
The only occasions I've used Flaps 2 was on a very long final (15nm) where Flaps 1 just kept the speed at 230 but Flaps 5 would slow it down to fast.

Agaricus bisporus
10th Oct 2010, 17:45
Understand it has a maintenance function only. What, I dunno.

Romeo E.T.
10th Oct 2010, 17:52
optimum take-off flap from "old" Durban intl rny 06 full length was a flap 2 setting on the B737-200...don't always presume the approach and landing phase of flight.

10th Oct 2010, 18:03
Romeo E.T.:

optimum take-off flap from "old" Durban intl rny 06 full length was a flap 2 setting on the B737-200...don't always presume the approach and landing phase of flight.

We used 5, 15, and 25 for takeoff, depending on runway length and elevation. Never 2, though; that must have been some huge ground speed at rotation.

10th Oct 2010, 23:43
Used Flaps 2 for takeoff on the 737-200 on a regular basis. For the long runways. Better climb limits. Flaps 5 for the shorter runways. Flaps 10 on gravel.

Mach E Avelli
11th Oct 2010, 04:55
Yep, flap 2 was very useful in the -200. Good trade between runway length and obstacle clearance. When Boeing built later versions they used a lot of existing components, so I guess the flap selection system was simply left there even though flap 5 generally became the better option with the higher thrust engines.

Capt Chambo
11th Oct 2010, 05:54
When was the flaps 2 setting needed....
Depending on our weight we used it on the 300/400/500 when ATC asked for 180Kts on the approach. We flew a fixed speed schedule in those days.

Never used it for take-off on either the classic or the -NG. And we never use it on the approach on the -NG.

why doesnt boeing change that flapsetting? Cut it out? certification?

I suspect that you have answered your own question :)

12th Oct 2010, 03:04
I've undeleted this thread. Please don't delete threads. If you have a REALLY important reason to do so, send me a PM and, if the reason is reasonable, I'll remove the thread.

Problem is that others have an interest in discussions and there is not much can happen that is more frustrating than having an interesting thread disappear on you ...

12th Oct 2010, 08:45
Never 2, though; that must have been some huge ground speed at rotation. - not so frightening, and certainly no worse than Improved ('going like a train') speeds - Flap 1 common for Classic take-offs where obstacles were the primary concern, but abandoned on the 737- 400 due to tailstrike risk. Used also on 200 and I assume 100. I was told it dated from 727 or even 707 (or even B17.......:D) from which the flap gate (and gear lever?) originates and rather than re-machine the whole thing Boeing left the gates as they are. If you use it, use the F1 manoueuvre speeds as I don't think any are published.

Callsign Kilo
12th Oct 2010, 09:02
Good for base leg into LGW in the NG when slowed to 180KIAS. Granted, we could use F5; however F2 doesn't get that much of an outing!!

12th Oct 2010, 09:35
Ck - never tried it - does the speed tape respond?

12th Oct 2010, 10:29
The early 737-200 had only 1, 5, 15, 25, 30 and 40 flap notches on the selector, so I don't think it came from the 727. It was referred to as having the basic wing.
Most of the Basic aircraft we had were fitted with dash 9 engines, and were a bit short on performance. It was often the case that F1 was very limiting on field performance, while F5 was very limiting on climb performance. On a shorter field, it would be a similar problem with F5 and F15.
I understood that the whole point of having F2 and F10, was to give a better choice in these conditions, i.e. F2 would be less limiting on field than F1,and less limiting on climb than F5, so that the available take-off weight would be higher.
The aircraft so fitted were referred to as having an advanced wing, and I recall that there were some other modifications, relating to the way the leading edge devices extended with different flap settings

12th Oct 2010, 10:33
If you use F2 on the NG the speedtape relables the F1 manouvering speed to F2 manouvering speed. Useful if you just want a tad more drag at the same speed.

12th Oct 2010, 10:51
I'm with Callsign K here, and not with Denti. On the -800 it allows us to slow to 180 if given by ATC, the F1 bug is often just above it, the bug does move down for F2.


Capt Chambo
12th Oct 2010, 12:25
...but abandoned on the 737- 400 due to tailstrike risk.

We occasionally use Flap 1 on the -900. Ridiculous Vr's and a only 13" tail clearance.

Not for the faint hearted :eek:

12th Oct 2010, 13:29
:eek: how many ***** has your lot experienced? I seem to recall the tail clearance on the 400 was a bit less at F1.

Back Seat Driver
12th Oct 2010, 22:14
On the 737-200, in some conditions, at near MTOW take-off speeds, Flaps 1 could exceed the brake energy limits (Vmbe). Flaps 2 take-off figures usually would accommodate the take-off. Faps 1 &(2) gave a better 2nd segment climb than F5/F15 on the -200. It is all revealed in the QRH Take-Off performance tables.

12th Oct 2010, 22:42
how many ***** has your lot experienced? I seem to recall the tail clearance on the 400 was a bit less at F1.

It has been a long time since I flew the classics, but I seem to recall 10" on the 737-400???

We had a tailstrike on a -400 shortly after delivery of the first, with only scraped paint to show for it though. A tailstrike on landing produced some damage a few months later.

The tail clearance figures in the FCTM were changed shortly thereafter IIRC.

13th Oct 2010, 05:15
We once had an old Boeing test machine that was a pre ADV B737-200. It had an ADV wing but everything else was an early model. We did use the the F2 selection for climb limited takeoff airports.

We use F1 at almost every airport on the B733.

13th Oct 2010, 05:28
No Flaps one gate on the B727.

The detents are at 2, 5, 15, 25, 30 and 40.

Many Airlines blocked off the 40 selection as 30 was more than adequate for most runways and the sink rate with flaps 40 could get away from you very quickly if you weren't careful.

Johnny Tightlips
13th Oct 2010, 06:45
I use F2 a quite a bit on the -800. If ATC have you level 15 miles out and ask for 180KTS it's a very useful setting. If I'm on the glide I just use F5 or F10 if needed.

14th Oct 2010, 14:24
Flap 2 in the 737-200 was used extensively at high altitude airports where Flap 1 was a problem with its higher V speeds. I think it was South America where Flap 2 was mainly used. Depending on runway lengths etc, the weights used for Flap 1 and 2 were normally max structual up to around 2000 ft airport altitude.

One advantage of Flap 2 if the choice was available, was a Human Factor aspect, in that the next flap (which was Flap 1) could be selected normally at V2 +15, which left the leading edge devices still extended.

This minimised the danger of someone inadvertently (carelessly?) when conducting a Flap 1 take off, retracting the flaps to up at V2 +15 instead of first accelerating to 190 knots (53 tonnes and below). On quite a few occasions I observed pilots calling for Flaps up at V2 +15 on a Flap 1 take off.

Old Smokey
14th Oct 2010, 15:36
I've no experience on the B737-200, only the B737-300. The low Flap settings available are not necessarily applicable to Takeoff considerations, but may have other useful functions.

On the B777 for example, Flaps 1 has no use for Takeoff (standing by for a blast for someone who uses it), Flaps 5 is the lowest used. Where it IS useful, particularly as the later and heavier B777s have high manoeuvering speeds, is for Holding, where the clean holding speed exceeds the limit for the pattern in use, and when a dispensation against the 250 Kt limit below 10000 ft cannot be obtained, Flaps 1 becomes a necessity (Definately NOT recommended in iceing conditions).


Old Smokey

14th Oct 2010, 16:25

Many Airlines blocked off the 40 selection as 30 was more than adequate for most runways and the sink rate with flaps 40 could get away from you very quickly if you weren't careful.

As demonstrated by a UAL 727-100 at Salt Lake City circa 1965 or thereabouts.

Shiny side down
12th Dec 2012, 14:01
Dragging up an old thread
I've been trying to find some information on this, and was happy to see that some other folk have used F2.

I once or twice called for it many moons ago when fuel was becoming an issue, and the big gulf between F1 and F5 speeds suggested that F5 was a bit excessive when keeping a much higher speed, such as 180kt during arrivals into places like London.

On one occasion, I was informed that if it isn't trained, it cannot be used.

On the NG, if you select F2, it bugs a speed of around 180kt. So the machine isnt surprised to see it, Which means Boeing must have something built in to use it. It has a position in the gauge, a detent in the quadrant, and a bug on the tape.
I know of at least one operator that has now determined it to be not available for use. No explanation given or available.

Is there any other detailed info or explanation of this otherwise superfluous flap position?

12th Dec 2012, 14:18
My 2nd favourite setting due to the aforementioned 180kt ability, my fav being Flap 10 (but not on the SFP aircraft where it is now useless) which is "best friend" on intermediate approaches when ATC just get it that little bit tight & getting those leading edges out does the trick nicely without resorting to gear/speedbrakes.

Shiny side down
12th Dec 2012, 14:34
Dammit, I was hoping that something would prove me wrong or ill-informed and that ops manuals authors were in possession of better info, rather than just a pen with which to dictate against that which they don't understand.

12th Dec 2012, 14:42
someone once whimsically said that it came from the B17 flap selector and Boeing had a few hundred left on the shelf.gate. Certainly after -200 I have never seen it 'approved' by thems-wot-knows'.

Shiny side down
12th Dec 2012, 15:29
There is sufficient information in the various Boeing manuals discussing the action of the leading edge devices when using flaps 1,2 & 5, but not one bit of data or advice saying not to use it, except in the company manuals with which Boeing has no direct input.

12th Dec 2012, 15:29
I've wondered this myself. My airline specifically prohibits flaps 2, with many a bulletin to reinforce it.

We also use flaps 1 for takeoff when needed in both the 800 and 900. Honestly, the tail clearance isn't as big an issue as the v1 and vR speeds. Rejecting a takeoff at speeds close to flaps 1 v1 would be an interesting exercise in braking. :eek:

12th Dec 2012, 15:58
Try it with an improved speed schedule at F1, V1s in higher 160s are quite interesting, especially if you have to chuck along at derate 2 plus 60 ATM, waiting over a minute until you can rotate.

12th Dec 2012, 18:35
on th NG F2 works great when ATC want 180kt as part of approach sequencing! F1 doesn't normally allow 180kt to be flown, F2 does have the speed tape bug move lower to allow 180kt and provides less drag/more efficiency than taking F5:ok:

13th Dec 2012, 03:54
The B737-100 used F2 for takeoff, it gave a similar performance as the B737-200 using F5. I used it on the B737-150 a lot (a B737 basic with the advanced wing). I was told it was gated because that was the go around flap setting for the B727 with one engine out and it was easier to set it correctly with the gate than without. For convenience they fitted the same flap mechanism in the B737 when it was first made, as they used the same fuselage jigs etc. It could have been the go around flap setting for the basic B737-100 as well and was left there even after the bigger engines and better performance of the later models because it was easier to to do that than re-engineer the flap mechanism?
It went out of favour when the airlines started using Boeing-generated takeoff charts, for which a great deal of money had to change hands. Having just one or two options for flap settings on takeoff would save a lot of money in chart costs and the bean counters would not know the difference in fuel consumption and cost. However a tail strike due to not setting the correct bugs (thinking you were using the regular F5 and the associated speeds) would offset many years of costs for the fuel savings due to a more optimum flap setting.