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on the severity of the
failures.
Degradation of the
flight control laws is
sometimes referred to
as reconfiguration. We
will study these
degraded laws in order
of increasing severity.
FLIGHT CONTROLS MENU
Reconfiguration Laws 3/29
Ground
mode
Ground
mode
In Alternate law:
Ground mode is as in Normal law.
Flight mode:
• Pitch control: load factor demand as in Normal law.
• Roll control: conventional, surface deflection is proportional to side stick deflection,
- Roll sensitivity is proportional to airspeed,
- Feels more sensitive.
• Yaw control: turn coordination is lost,
- Damping available with limited authority.
Landing mode: Direct law when landing gear is selected down (discussed later).
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Flight
mode
Flare
mode
Conventional
control in roll &
alternate in yaw
FLIGHT CONTROLS MENU Reconfiguration Laws 4/29
Degradation to alternate law is indicated by the
ECAM caution F/CTL ALTN LAW (PROT LOST).
You will see this caution in detail in the
abnormal operation module.
Under alternate law, most protections are lost.
Some are replaced by stabilities. We will continue
by studying the loss of protections.
FLIGHT CONTROLS MENU
Reconfiguration Laws 5/29
Pitch limits
Pitch protections lost
Pitch attitude protection is lost and the flight
control computers will not limit the nose up or nose
down pitch attitude..
On the PFD, the green dashes which mark the
protection limits in Normal law, are replaced by
amber crosses.
FLIGHT CONTROLS MENU Reconfiguration Laws 6/29
Bank angle protections lost
Bank angle protection is lost.
On the PFD, the green dashes are
replaced by amber crosses.
FLIGHT CONTROLS MENU
Reconfiguration Laws 7/29
The Maneuver protection is similar to
Normal law.
So we will go straight to the differences
between Normal and Alternate high angle of
attack protection.
MANEUVER PROTECTION
FLIGHT CONTROLS MENU Reconfiguration Laws 8/29
Low speed stability
LOW SPEED STABILITY
In Alternate law, the High angle of attack
protection is replaced by a Low speed stability.
V alpha prot and V alpha max are replaced
by a stall warning speed (Vsw), indicated by a
red and black barber pole.
AIR FLOW
FLIGHT CONTROLS MENU
Reconfiguration Laws 9/29
As speed approaches Vsw a gentle
progressive nose down pitch input is
introduced to lower the nose and prevent
further speed loss.
The pitch input can be over ridden by pilot
input on the side stick.
Vsw
LOW SPEED STABILITY
FLIGHT CONTROLS MENU
Reconfiguration Laws 10/29
At Vsw, an aural “STALL ! STALL !”
warning is triggered.
The aircraft will stall if the warning is
ignored.
Alpha floor protection is inoperative in
Alternate law.
LOW SPEED STABILITY
FLIGHT CONTROLS MENU
Reconfiguration Laws 11/29
In Alternate law, High speed stability
replaces High speed protection.
The green dashes are replaced by amber
dashes on the speed scale.
Above Vmo or Mmo, a nose-up input is
introduced to raise the nose and prevent
further speed increase.
This pitch tendency can be over ridden by
the pilots.
HIGH SPEED STABILITY
FLIGHT CONTROLS MENU
Reconfiguration Laws 12/29
As in Normal law, if VMO/MMO is exceeded
the over speed warning is triggered.
HIGH SPEED STABILITY
FLIGHT CONTROLS MENU
Reconfiguration Laws 13/29
AIR FLOW
Pitch limits
Note that according to the failures, an
Alternate law without reduced protections can
exist.
In this case, only the Maneuver protection is
provided. The High speed and Low speed
stabilities are also lost.
Stall and over speed warnings are still
operative.
FLIGHT CONTROLS MENU
Reconfiguration Laws 14/29
Direct law is the
lowest level of
computer flight
control. Pilot inputs
are now sent to the
control surfaces
unmodified.
Because of the
large number of
failures required to
degrade to Direct law,
it is unlikely to occur
during normal flight.
It is most likely to
be encountered when
the landing gear is
lowered after an inflight
degradation to
Alternate law.
FLIGHT CONTROLS MENU
Reconfiguration Laws 15/29
In Alternate law, when the landing gear is
extended, the control law will degrade to Direct
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