Flaps 2 on B737

[Qbix]

Any idea what are they for?
There have never been any T/O performace data for Flaps 2 so what are they for??

[plain-plane]

Almost every day I use flap 2 to give ATC the requested standard speed requested on base while using min flap:ok:… (CAT C = 180 KTS)
This obviously depends on which version and at what weights you are flying at…

This obviously does not answer your question on why it is there…I suspect that the reason is the same as with all other things on 737: :EBecause it has always been there on Boeings….:E

[gas-chamber]

On earlier, low-powered B737 such as the -200, flap 2 provides almost optimum takeoff performance on longer runways. Flap 1 is also available for takeoff, but requires a very long runway and high speed tires.
On the later models, it was not favored to use either of these settings due to the risk of a tail-scrape (due to the longer body length) so generally flap 5 is the minimum used by most operators, though I think the -500 was OK at flap 1 (short body).
So why is the flap 2 gate still there on later models? Probably because Boeing have a philosophy never to change a part number unless there is a clear cost saving in doing so.
And in the event of a flap malfunction on landing, I would rather have flap 2 than flap 1 if that was available.

[Tee Emm]

There have never been any T/O performace data for Flaps 2 so what are they for??

Quite wrong. In my former company, Boeing issued us with Flap 2 Runway Analysis charts. The safety factor being at V2 +15 we selected flap 1 whereas with a flap 1 take off an inadvertent selection at V2 + 15 would cause a problem due to the LED retracting at a dangerously low IAS.

[Back Seat Driver]

737-200AD (-17's) had the Flap 2 T/O figures provided in the QRH.
Flaps5 was the preferred T/O setting, though on a heavy T/O Flaps1 was preferable. But for a heavy T/O with a downwind component Flaps1 would exceed the Brake/Energy limits in a high speed rejection. The solution was Flaps2, virtually the same T/O performance with the Brake/Energy limits respected. My uneducated guess why the Flap2 position is still there in later models, is because a lot of the 737 certification data dates from the original models.

[Rainboe]

gas- we operate 700s and 300s. I fly the 700 almost completely, and I would say about 25% are Flap 1 and 75% Flap 5, with a once a year Flap 15 (Bournemouth Hurn I remember).

[BOAC]

The preference for Flap5 was for the longer bodies, as 'gas-chamber' says. I think most 400 operators have dropped Flap1 and I would guess the same for the 800/900? I cannot imagine that Flap2 would significantly improve tail clearance so, as said, the answer is 'because the B-17 had it':)

[Sniff]

As BOAC says flap 1 isn't good on the -400. Sets off the config warning... (believe its the only variant of the 737 to do so)

Flap 2 used to equal 180kt and flap 10 160 in the old classics, before the rudder probs. We went up ten knots then.

[Denti]

Config Warning is actually a selectable option. We used to have a -500 from Maersk which could only do flaps 5 and 15, but not 1 and would set off the config warning at 1. However on our -300s we can use flaps 1.

Back when we were still owned by BA and used the performance data provided by them flaps 5 was standard, nowadays we use an EFB with boeing performance data and nearly allways use flaps 1, most of the time improved climb too, and that needed more adaption than flaps 1 vs flaps 5.