Correct use of vertical speed

Hi guys so ive been noticing that every time after takeoff when i put my first degree of flaps up the vertical speed suddenly drops down em i doing something wrong btw im not the best person using flaps em i using them wrong? I usually put my first degree of flap up after i pass 190kts and then i just guess

Hello,

Could you provide us with some more details,

What aircraft are you using?
What weight are you taking off at?
What takeoff flaps are you using?

A350
I was doing an 8:00hr flight i put 11hr of fuel
Flaps 2

Was the autopilot on at the time?

I believe this is just the shifting airflow over the wings. How much is it dropping?

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yeah i use autopilot when i takeoff

imy vertical speed was at 1600 it drop to 900

And what is your trim setting? My initial observations are that either you are retracting flaps all at once (instead of one at a time) or that your speed is not suitable, but trim also does play a factor. Can you also provide the VS that is set in the autopilot?

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I’m pretty sure a brief drop in VS and/or pitch angle is perfectly natural, and to be expected, when you change the lift component of the wings. Retracting flaps temporarily reduces lift compared to when they were extended.

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Adding on to @anon38496261 above, the Autopilot doesn’t know you will retract and change the lift component of the wing, making the change in VS more noticeable. If you want to smoothen it out, I would hand fly in order to be able to pull up as the flaps retract to get a more constant VS throughout the process!

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Yeah, I hand fly all the time (usually until just before cruise and after 5,000 or so feet on landing)

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Hey! Flaps help to create both more drag and more lift, which is why you use them on the initial phase of the takeoff.

When you retract your flaps, you turn your wing from a higher-lift mode to a more “aerodynamic” mode, which gives you less lift, but greater speed and less drag.

So when you retract your flaps, a drop in your vertical speed is to be expected. On the contrary, when you extend your flaps (like when you’re descending), you should expect a slight gain in your vertical speed.

The autopilot is initially “surprised” by when you suddenly retract or extend your flaps. It takes a second or two to react accordingly.

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Tbh I would not recommend using the AP until you have cleaned up anyway. Once you pass 1000ft AAL you can drop the nose a few degrees and start accelerating, shouldn’t be long until you are at flaps up/0.

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But im not the best hand flyer🙃

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Practice makes perfect 😉

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When you retract flaps, the angle of attack increases so AP has to pull back to retain VS.

What you are seeing is a VS dip because AP cannot respond fast enough. This is perfectly fine. There needs to be a balance in IF in fast fast AP responds to VS change, since otherwise the AP can become very unstable.

BTW a standard climb profile: climb out at around 15 pitch, up to 1000 AGL, retract one notch of flaps (on 737s, skip 2 and go to 1), set N1 to around 85-90, and lower pitch to 10 degrees. Retract flaps when fast enough and set SPEED AP at 250 (or up to climb speed if you are above 10000 already)

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You could try to use trim or the VS to counter the force that pushes the plane nose down as it’s happening.

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But i had never seen the pitch what’s taht?

how do i know the degree of the pitch?

It’s the horizontal line on the HUD and/or primary flight display

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