Originally Posted by Vessbot
For a non Airbus guy, can you guys say what causes this warning to come on?
An aural low-energy “SPEED SPEED SPEED” alert, repeated every 5 s, warns the pilot that the aircraft’s energy level is going below a threshold under which he has to increase thrust, in order to regain a positive flight path angle through pitch control.
It is available in Configuration 2, 3, and FULL. The FAC computes the energy level with the following inputs:
‐ Aircraft configuration
‐ Horizontal deceleration rate
‐ Flight path angle.
The aural alert is inhibited when:
‐ TOGA is selected, or
‐ Below 100 ft RA, or
‐ Above 2 000 ft RA, or
‐ Alpha-floor, or the ground proximity warning system alert is triggered, or
‐ In alternate or direct law, or
‐ If both radio altimeters fail.
During deceleration, the low-energy aural alert is triggered before alpha floor (unless alpha floor is triggered by stick deflection). The amount of time between the two alerts depends on the deceleration rate.
So, the alert only applies below 2000' RA. Typically it turns up on the base or final turn, and usually as the pilot overbanks to capture the next leg. Basically, if you pull back on the stick and there's no "zoom climb" left (speed you can trade for pitch) the aircraft says "no es bueno, kemosabe". Keep pulling and it will give you TOGA thrust regardless (an autothrottle feature known as "Alpha Floor").
en it’s up to you - to push it down or to increase power.
Of course, to increase power is not intuitive in an airbus. Pull the throttles back to disconnect, and then push them forward.
Which is a lot to think of, if you're in that situation.
So the solution is to select (pull) 160kts on downwind, to ensure that you have enough energy on base and final, rather than allow the aircraft to drift the speed back to the minimum (as it will do on managed (automatic) speed).