This is the latest from the Airbus chief test pilot
The AoA decrease may be obtained
indirectly by increasing the speed,
but adding thrust in order to increase
the speed leads to an initial adverse
longitudinal effect, which trends to
increase further the AoA (fig. 4).
It is important to know that if such
a thrust increase was applied when
the aircraft is already stalled, the
longitudinal effect would bring the
aircraft further into the stall, to a
situation possibly unrecoverable.
Conversely, the first effect of reducing
the thrust is to reduce the
AoA
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In summary:
FIRST: The AoA MUST BE REDUCED.
If anything, release the
back pressure on stick or column
and apply a nose down pitch input
until out of stall (no longer have
stall indications). In certain cases,
an action in the same direction on
the longitudinal trim may be needed.
Don’t forget that thrust has an
adverse effect on AoA for aircraft
with engines below the wings.
SECOND: When the stall clues
have disappeared, increase the
speed if needed. Progressively
increase the thrust with care, due to
the thrust pitch effect.
In practice, in straight flight without
stick input, the first reaction
when the SW is triggered should be
Relative airflow
Relative airflow Thrust increase
Relative airflow
Thrust reduction
Figure 3
Pitch control
is a direct
AoA command
Figure 4
Adding thrust
leads to an
increase in AoA
Figure 5
Reducing thrust
leads to a
decrease in AoA
to gently push on the stick so as to
decrease the pitch attitude by about
two or three degrees in order to decrease
the AoA below the AoA SW.
During manoeuvres, the reduction
of the AoA is generally obtained
just by releasing the backpressure
on the stick; applying a progressive
forward stick inputs ensures a
quicker reduction of the AoA.
If the SW situation occurs with
high thrust, in addition to the stick
reaction, reducing the thrust may
be necessary.
10. Procedure
As an answer to the stall situation,
a working group gathering the FAA
and the main aircraft manufacturers,
including Airbus, ATR, Boeing,
Bombardier and Embraer, have established
a new generic procedure
titled “Stall Warning or Aerodynamic
Stall Recovery Procedure”
applicable to all aircraft types.
This generic procedure will be published
as an annex to the FAA AC 120.
This new procedure has been established
in the following spirit:
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