B737 Flaps 25 on Approach

[ImbracableCrunk]

I recently returned to a flying job back in my own country after having flown contract work overseas.

The approach profile at my current airline uses Flaps 25 while on approach then to Flaps 30 and then Flaps 40, if desired.

At my overseas work, Flaps 25 was not used at all.

I've done Flaps 25 SFP departures, but does anyone use Flaps 25 during approaches? The FCTM doesn't say anything. The A/S indicator flaps speed guidance is predicated on F1-5-15-30-(40).

Any good reason to use Flaps 25 on approach?

[VH-ABC]

I personally use flap 25 on the way to a flap 40 landing... Seems to give a smoother transition from 15 to 40. I also use flap 2 when it suits the situation, ie giving ATC their requested speed at minimum thrust.

[ImbracableCrunk]

I use F10 often, but my SOPs don't specifically mention it. They do however mention the schedule F1-5-15-25-30-40. You can't skip any.

[Denti]

We used to have the same schedule, albeit on classics. However it got changed to 1-5-15-30-40 around 4 years back on both classics and NGs for us. We can non-standard use any of the other flap settings, but i have to say i haven't used 25 much if at all.

[BOAC]

IC - don't worry about it! The FCTM has manoeuvre speeds for F25 and it has been in the 'standard' approach sequence for much of my 737 life until the last few years when 15-30/40 started appearing. As long as both pilots know what is happening..........? I would not be surprised if buried somewhere in the Boeing vaults are take-off figures for F25.

When I started flying the jet, some of the 727 dinosaurs who had been 'forced over' to 'the slug' were (non-SOP) sequencing through F2 on the approach!

[STBYRUD]

In our manuals they suggest 1-5-15-30 and 1-5-15-40, but the gap 15-40 is usually way too big, we used to have flaps 25 in between, now its non-standard but still occasionally used 'non-standard' when needed. (-800)

[ImbracableCrunk]

I would not be surprised if buried somewhere in the Boeing vaults are take-off figures for F25.

Well, prepare to not be surprised: the Short Field Performance package on the -800 and maybe the new -900ER uses F25 for takeoff.

My point on F25 on approach is this: if you want it, use it. But don't mandate something that Boeing doesn't recommend/require.

[in my last airline]

I agree with a previous post, and that it is 'kinder' on the airframe to use F25 on your way to a F40 landing but more importantly, if you are hand-flying (oh my god, are you crazy!') it makes for a more manageable transition, I think.
The Boeing instructor pushed for F15 straight to land flap during our transition training but I think if they could have removed F2 and F25 altogether they would have but it would have been too much of a change from a Type point of view. One of my pet hates is when a guy calls, 'non standard flap 2.' it's not non standard, use it if you need it. Why use F5 when 2 will do. It's quieter than 5 too!

[captjns]

I use all the flap settings from 1 to 40. Power set at about 40% from flaps 0 right through final flap. Allows for minor trim adjustments, power increases, and smoother control inputs to overcome configuration changes.

[RAT 5]

All the comments about F15 - F40 being a lurch are correct. F25 smooths it out and is not necessary if landing F30. For irritations here's another. Guys landing F40 call F15-F30-F40. Why are they afraid of F25? Plus there is no bug for F30 if Vref40 in use, but there is a F25 bug. Why call a flap setting for which there is no bug? I know Vfly F40 is OK for F30 in transit, but it's the philosophy of calling a flap with no bug and not calling for a setting where there is a bug. KISS

[BOAC]

Originally Posted by in my last

'non standard flap 2.' it's not non standard,

- it is indeed 'non-standard' in as much as you have absolutely NO idea what min manoeuvre speed is, do you?

[FlightPathOBN]

Concur with BOAC and Denti...variants have used 25 for many years

and STBY, 15-30 and 15-40 is a big gap and significant performance differences, and position timing...

Personally, I dont like 40, as if you need a go-around, it takes too long to back out of, but that is from a pure performance view...

[ImbracableCrunk]

Can we agree that F25-F30 is probably not necessary?

I can see F25-F40 and F15-F30. But F15-F25-F30?

[captjns]

It's all a matter of preference and technique whilst operating the aircraft within it's limitations.

If I'm not approach climb limited, I prefer 40 as setting land speed records in the slug is not an ambition of mine. Easier on the wheels and brakes.

[b737NGyyc]

I would not be surprised if buried somewhere in the Boeing vaults are take-off figures for F25.

We routinely use F25 for take off out of Maui (PHOG) in a standard -800 with no short field performance package. We are understandably heavy, 165,000 lbs + as we are head back to the mainland and the runway is short, 6995 ft. It makes for a busy flap retraction schedule and requires accurate speed control until the flaps are well on their way up.

I also routinely use F2, F10 and F25 if required at various stages of the arrival and approach. I prefer F30 for landing in the -600 and -700 if F40 is not required by field length and F40 for landing in the -800 regardless of runway length as it gets the landing speed a bit lower and reduces the tendency to float.

[in my last airline]

Hello BOAC,
Not sure what you mean exactly wrgds to, not knowing your F2 manoeuvre margin. You still have a pictorial representation of your manoeuvre margin on the Speed Tape, what more do you need? I'm probably being thick here. Can you elaborate a little more pls.

CAPTIJNS, with respect, your 40% setting may work well but wastes precious fuel over a long career not to mention additional noise. It doesn't come under the heading, efficient.

Rgds. IMLA

[BOAC]

Well, a start would be something from Boeing/the FCOM? I'm not too sure also that some versions of the 737 display "a pictorial representation of your manoeuvre margin on the Speed Tape". Ever flown a -200 or interim -300?

'captnjs' was talking about F40, not 40%.

[in my last airline]

What I mean is you have the config limit speed and next flap extension limit speed at the top of the speed tape and stall warning and 0.3G manoeuvre margin at the bottom of the speed tape. When operating F2, provided you are at the manoeuvre speed, as shown by the 2 symbol on the tape, you are well away from both limiting speeds therefore by definition you are free to operate the airplane within the normal envelope.
I flew the classics -200, hardball-300 and EFIS classic for 7,000 hrs on a fixed flap speed schedule which admittedly doesnt have a published fixed speed for F2, which is what I now think you were writing about. I've been on the NG for a while now so loosing touch in the Jurassic and Classic.

Captijns was post 9 that said 40%....

Rgds

[BOAC]

Captijns was post 9 that said 40%....

- ok - I assumed post #14. What ecological/financial disaster do you see arising from 40% as opposed to approach idle?

Do you not feel that the omission by Boeing of a F2 schedule (in all 737's) says something? The 'setting' is there because of the flap quadrant. Folklore says it is the same as the 707/727(where I believe it was scheduled) and they did not bother to change it.

[Denti]

Actually, there are limits mentioned in the FCOM (737NG), max speed for flaps 2 is 250kts and the flap maneuver speed is Vref 40 + 40kts. On Speedtape equipped airplanes you get those indications displayed directly as well. Had that on all -300s and -500s i've flown and of course on the NG it is standard anyway.

By the way, do some airlines require a direct flaps 15 to 40 jump during extension? We have to use flaps 30 inbetween there which makes it somewhat easier, flaps 25 as non-standard operation may be used.