I am always confused between both of these two. I know both signals low speed or high AOA

  • $\begingroup$ Can't speak for the A320, but "low energy" usually refers to both low speed and power, like when you go to idle on landing. Once the power comes off when you are at Vref you are in a low energy state. AOA limits can be reached at a wide range of speeds and is not directly related to total energy state. $\endgroup$
    – John K
    Jul 17, 2019 at 3:06

1 Answer 1


Low energy warning ("SPEED SPEED SPEED") is a function of Flight Augmentation Computer (FAC). It monitors aircraft’s flight path and warns if speed is about to decay below the threshold where power is needed in order to maintain positive (ie. climbing) flight path with pitch control.

Alpha floor is provided by auto thrust (A/THR) - (commanded by FAC), which sets full thrust (TOGA) regardless of pilot input if angle of attack rises above pre-determined angle. The threshold depends on aircraft configuration.

  • $\begingroup$ I would add that the Low Energy Warning is a warning like its name is referring to (Aural "SPEED SPEED") and the Alpha Floor is a protection, so it will take command on the ATHR and apply TOGA power if triggered. $\endgroup$
    – Chris Lau
    Sep 19, 2019 at 7:22

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