OPERATIONAL PHILOSOPHY

FLIGHT CONTROLS


ENGINE FAILURE

In flight, if an engine failure occurs,
and no input is applied on the sidestick,
lateral normal law controls the natural tendency
of the aircraft to roll and yaw.

If no input is applied on the sidestick,
the aircraft will reach an approximate 5 °
constant bank angle, a constant sideslip,
and a slowly-diverging heading rate.

The lateral behavior of aircraft is safe.

However, the PF is best suited to adapt the
lateral trimming technique, when necessary.

From a performance standpoint, the most effective
flying technique, in the event of an engine failure
at takeoff, is to fly a constant heading
with roll surfaces retracted.

This technique dictates the amount of rudder
that is required, and the resulting residual sideslip.

As a result, to indicate the amount of rudder that is
required to correctly fly with an engine-out
at takeoff, the measured sideslip index is shifted on the
PFD by the computed, residual-sideslip value.
This index appears in blue, instead of in yellow,
and is referred to as the beta target.

If the rudder pedal is pressed to center the beta target index,
the PF will fly with the residual slip, as required by
the engine-out condition.
Therefore, the aircraft will fly at a constant heading with
ailerons and spoilers close to neutral position.

BETA TARGET ON PFD

Operational Recommendation:

In the case of an engine failure at takeoff, the PF must:

• Smoothly adjust pitch to maintain a safe speed
(as per SRS guidance)

• Center the Beta target
(there is no hurry, because the aircraft is laterally safe)

• When appropriate, trim the aircraft laterally
using the rudder trim

• Apply small lateral sidestick inputs,
so that the aircraft flies the appropriate heading.

AVAILABLE PROTECTIONS

Normal Law provides five different protections :

• High angle-of-attack protection

• Load factor protection

• High pitch attitude protection

• Bank angle protection

• High speed protection.

OPERATIONAL PHILOSOPHY

FLIGHT CONTROLS

AlTERNATE LAW


In some double failure cases, the integrity and redundancy
of the computers and of the peripherals are not sufficient
to achieve normal law and associated protections.

System degradation is progressive, and will evolve according
to the availability of remaining peripherals or computers.

Alternate law characteristics (usually triggered in case of a dual failure):

‐ In pitch: same as in normal law with FLARE in DIRECT

‐ In roll: Roll DIRECT

‐ Most protections are lost, except Load factor protection.

At the flight envelope limit, the aircraft is not protected, i.e.:

‐ In high speed, natural aircraft static stability
is restored with an overspeed warning

‐ In low speed (at a speed threshold that is below VLS),
the automatic pitch trim stops and natural
longitudinal static stability is restored, with a stall warning at 1.03 VS1G.

In certain failure cases, such as the loss of VS1G
computation or the loss of two ADRs, the longitudinal static stability
cannot be restored at low speed. In the case of a loss of three ADRs,
it cannot be restored at high speed.

In alternate law, VMO setting is reduced to 320 kt,
and α FLOOR is inhibited. (On A318, MMO setting is also reduced to M 0.77.)

OPERATIONAL RECOMMENDATION:

The handling characteristics within the normal flight envelope,
are identical in pitch with normal law.

Outside the normal flight envelope, the PF must take
appropriate preventive actions to avoid losing control,
and/or avoid high speed excursions.
These actions are the same as those that would be
applied in any case where non protected aircraft
(e.g. in case of stall warning: add thrust, reduce
pitch, check speedbrakes retracted).