Flaps / Spoilers and elevator compensation

[Roj]

When we deploy flaps, we need some down elevator compensation.
When we deploy spoilerons (both ailerons up), we also need some down elevator compensation.

What is the explanation of this paradox?

To complicate the question - what occurs in inverted flight? Presumably we would need up elevator compensation? :confused:

[CANTZ506]

When we deploy flaps, we need some down elevator compensation.....

To complicate the question - what occurs in inverted flight? Presumably we would need up elevator compensation? :confused:

Where did you read that? I know that you need up compensation for flaps.
Flaps increase the lift of a wing, but add also a torque, being aft the COG, moving the nose down; then you need the elevator up to compensate.

No problem about inverted fligth: both surface are inverted, so you don't need to reverse the elevator throw.

The matter is: why should use flaps in an inverted flight?

[Roj]

It was my assumption that down compensation was used with flaps to prevent the plane ballooning up. Correct me if i'm mistaken in this.



The matter is: why should use flaps in an inverted flight?

This aspect was hypothetical.

[CANTZ506]

Well Roj, that makes me confidently I've read a rigth assertion! :D
As I said, the deployed flaps give a kick to the plane, or balloning it, depending on the a/c speed and how fast you deploy them.
But they act also as elevator, with a more shorter lever arm being closer to COG, along the longitudinal axis.
Thus, they will push the nose a bit down.

As you rigth supposed, when you use ailerons as spoilers, you get the opposite effect: the torque exert by spoiler pull the nose up. Moreover, cause the lift dump, the resulting angle of attack of the wing(falling down) will be higher and you need to correct it, to prevent a stall, with the elevator down.

Hope I was clear and... right! :rolleyes:
Piero.

[Roj]

Thanks, that makes sense.