747-400 flap retraction speeds

[druglord]

Are the bugged speeds the minimum speed at that flap selection or are they the speed which you select that flap?

ie. accellerating through the speed bugged flap 5 do you take flap 5 at this speed or must you stay at flap 10 until accellerated through this speed?

and for approach are these the min manoevering speeds at flap 5 or is it the speed in which you select flap 5?

[SNS3Guppy]

On departure, the bugged airspeeds are minimum maneuvering airspeeds for a given flap setting. Typical is flaps up at V2+80, Flaps 1 at V2+60, flaps 5 at V2+40, and the takeoff is done at flaps 10 or flaps 20. Assuming a takeoff at flaps 10, the initial flap retraction to flaps 5 would take place at the bugged speed of V2+40. At that time, maneuvering is generally limited to 15 degrees of bank. At the relevant bugged speed plus 10 knots, then it's a standard bank. With flaps up at V2+80, same applies. Accelerating 10 knots above that allows for a standard bank.

The pilot flying will call for flaps up as the airspeed passes through the relevant bugged speed. Per above, as the airplane reaches V2+80, flaps up. And so on.

For approach, flaps may be selected at any time when the aircraft is below the maximum flap speed for a given setting. However, the aircraft may not be flown at a speed less than the bugged speed for that flap setting, if that level of flaps have not been selected. for example, if the policy is to land at Vref+5 as the bug setting, additional bugs are placed at 20 knot intervals above this. If Vref is 155, the bug setting at 160, then the bugs are set at intervals above that, spaced by 20 knots.

The initial flap setting can be any time below the max flap speed, but in this case one won't go below 240 knots without at least selecting flaps 1. Ordinarily this may be selected at a higher speed. When it's selected depends on what the airplane is doing, what ATC needs the airplane to do, etc. Flaps 5 is then selected at a point between max flap speed for flaps 5, and 220 knots in this case. Same for flaps 10, with the minimum speed being 200, and so on.

Different operators may have slightly different policies or SOPs on the subject, as may different pilots have slightly differing techniques.

--Let me add that I just noted you're asking about the -400. The comments above were regarding the classic. Sorry for any confusion, but it's as close as I can go.

[skiesfull]

To simplify Guppy's post (and this is for the -400), the Flap 5 bug is the minimum manouevre speed with Flaps 5 set. For departure, once the flap 5 bug is achieved, select flaps 5. For approach, once the flap 5 speed is achieved (some operators add 5 or 10 knots as a margin) then select flaps 10 and once set reduce to flap 10 bug. In other words, do not reduce below the bug speed for that flap setting. OK?

[druglord]

ah thank you so much for your help.

[Marty McFly]

During the flap retraction, is it possible to select the next flap setting up, as long as the aircraft has passed the previous flap settings' minimum speed and is accelerating? I'm asking regarding the -400.

So just to be clear:

Current configuration - Flap 5, Speed is 200kts and accelerating to min clean.

Can PF ask for Flap 1 now? As long as the parameters above are maintained. The logic being that; by the time the A/C has reached the minimum speed for that flap setting, the flaps will have retracted to requested setting in the same time.

Thanks

[main_dog]

I'm not sure if I've understood the question, but my operator only allows selection of the next lesser flap setting upon reaching the minimum speed for the new setting.

An example: at 310t, Vref30 will equal approximately 160kts. Thus flaps 5 minimum speed will be 200 (VREF + 40), flaps 1 will be 220 (REF + 60) and flaps up will be 240 kts (REF + 80). While "cleaning up", flaps 5 are set passing 200, flaps 1 at 220 and flaps up at 240 (although above 307-ish tons, full maneuvering speed will only be achieved at Ref +100) .

Note that this is different from the classic where the +20/+40/+60/+80 are referenced to V2... on the -400 they're referenced to the Vref flap 30 speed for the current weight.

[Marty McFly]

Thanks for that!

[B4MJ]

747 is different from other Boeing models in that flaps are not retracted until the new maneuvering speed is reached. So on a flaps 20 climb out, you would accelerate until airspeed increased to the flaps 10 mark. Then you would call "flaps 10" and continue accelerating. At the flaps 5 speed mark you would call "flaps 5" and so on until selecting "flaps up".

This seems unnatural to pilots coming from the two engine Boeings.