747 Flap Speed

[bva1920]

Last night I was doing my pref light and taxi to runway 09 at KMIA and as i was setting the flaps to 20 I notice for the first time that the time between up and 1 to be 10-15 secs. 1 to 5 45-50 secs. 5-20 less than 3 secs. I do have one question.

Why does it it take so long to go from flaps 1 to flaps 5. I watch as the flaps were extending trying to make sense of this still am baffled. Anyone have an idea as to why this is and if so point me in the right direction.

Thank you

[ChristoffNY]

20 degrees is quite a steep setting for take off dude, but I wouldn't say the time thing is a problem with your sim, have you youtubed any videos of 747 flaps extending?

ChrstoffNY

[Adam24]

I think thats to make the speed decrease smoother. Imagine what would happen if the flaps would extend in 5 sec. That would be to abrupt. Thats just my opinion.

[mrzippy]

I agree with Adam24. Quick extension is a bad thing! Try 5 degrees flaps for takeoff.

[mjrhealth]

Flaps in real life just take a long time to retract and extend.

[tommchowat]

20 degrees is actually a very normal takeoff setting for the 747. As for the speed they extend at, it's mainly because the sheer size of the wing and therefore the flaps would cause some very undesirable flight characteristics if the flaps extended quickly. The camber change of the wing is so large as the leading edge devices are also massive (Krueger flaps). All that lift and drag extending too quickly isn't a good thing.

[garryrussell]

Don't forget the the up to 1 might only be one degree down but the flap is moving back a fair bit.

The angle in degrees is only a part of the overall travel.

The larger angles are just that, the smaller have a lot of fore and aft travel.