Speed Brakes

[Guest november678x]

Hello to all, why does the nose have to be raised when the speed brakes are up in level flight to maintain altitude? When I put them down I lower the nose back to its previous attitude to maintain altitude. Is this a real aerodynamic effect on the real aircraft? As a passenger I never notice nose up pitches when the speed brakes went up in level flight. Thank you :-wave

[teropa]

You have most likely seen speedbrakes extended in a level flight, but the aircraft has been descending, that is why the nose attitude hasn't changed all that much.If the aircraft is descending, you will get a higher descent rate with speedbrakes out, the nose attitude will stay almost the same, and of course it depends on the maneuvering pilots are after (steep/shallow descent).However, if you were to extend the speedbrakes in level flight, holding altitude, you would definitely see a pitch up in a real aircraft. The speedbrake affects the airflow on top of the wing, and the wing needs a higher angle of attack to maintain the lift to stay at the same altitude, because the distorded airflow cannot provide as much lift as it does with speedbarkes retracted.Tero

[Guest AAL223]

Yes, this is a real affect in flight. Deploying the speed brakes stops the streamlining of the wing and prevents smooth air flow across the top of the wing which results in a loss of lift. A slight nose up attitude is required to maintain altitude. To make it really simple, think about when the aircraft is turning. One aileron up and One aileron down. The aileron down is producing lift because it is increasing the camber of the wing just like flaps do. The aileron going up is similar to how the speed brakes cause a loss in lift. The aileron up deflects air upward pushing the wing down and reducing lift.

[Guest gw19]

Good stuff on spoilers(Speedbrakes) Spoilers are small, hinged plates on the top portion of wings. Spoilers can be used to slow an aircraft, or to make an aircraft descend, if they are deployed on both wings. Spoilers can also be used to generate a rolling motion for an aircraft, if they are deployed on only one wing. This slide shows what happens when the pilot only deflects the spoiler on the right wing. Spoilers Deployed on Both WingsWhen the pilot activates the spoilers, the plates flip up into the air stream. The flow over the wing is disturbed by the spoiler, the drag of the wing is increased, and the lift is decreased. Spoilers can be used to "dump" lift and make the airplane descend; or they can be used to slow the airplane down as it prepares to land. When the airplane lands on the runway, the pilot usually brings up the spoilers to kill the lift, keep the plane on the ground, and make the brakes work more efficiently. The friction force between the tires and the runway depends on the "normal" force, which is the weight minus the lift. The lower the lift, the better the brakes work. The additional drag of the spoilers also slows the plane downhttp://www.grc.nasa.gov/WWW/K-12/airplane/bga.html good basic aero knowledge http://www.grc.nasa.gov/WWW/K-12/airplane/...es/NASAlogo.gif George Walker