Thanks 19of77, I stand corrected...
Zat zelf al een beetje te twijfelen toen ik het poste; niet echt doordacht.
Zie nu idd dat het verhaal niet klopt, tegenstrijdige opmerkingen... Wat zakt die theorie snel weg als je een tijdje die kist niet vliegt!
De hele tekst:
ABNORMAL CONTROL LAWS - GENERAL
ALTERNATE LAW
Pitch alternate and roll direct is the first level of degraded control law, resulting from some double failures.
The autopilot may be available, depending on the cause and type of failure(s).
DIRECT LAW
The sidestick is directly coupled to the controls via the computers, but without any of the stabilization feedbacks. In effect, this law turns the aircraft into a conventional aircraft, but is compensated for configuration and CG. The pilot must use manual pitch trim, as is signaled on the PFD. The autopilot is not available.
MECHANICAL BACKUP
The pilot can use the pitch trim and rudder to control the aircraft for short periods of total loss of fly-by-wire.
ABNORMAL CONTROL LAWS - IN DETAIL
ALTERNATE LAW
Pitch
Alternate law in pitch is almost the same (for the pilot) as the normal control laws.
However, alternate law does not maintain any of the protections, except for the load factor limitation. As a result, the pilot must fly the aircraft more attentively to avoid inadvertently exceeding the normal limits.
Alternate law reduces VMO to 320 knots to restore a normal aircraft speed margin in case of upset. This is not necessary in the Mach range, because the margin there is, in any case, conventional.
An aural "STALL, STALL, STALL" warning sounds at low speeds. Upon hearing it, the pilot must return to the normal operating speed by taking conventional actions with the controls:
THRUST LEVERS . TOGA
At the same time :
PITCH ATTITUDE . REDUCE
BANK ANGLE . ROLL WINGS LEVEL
SPEEDBRAKES . CHECK RETRACTED
If a danger of ground contact exists, reduce pitch attitude no more than necessary to allow the airspeed to increase. After initial recovery, maintain speed close to VSW, until it is safe to accelerate.
If below 20000 feet, and if in clean, select FLAP 1.
Out of stall, when no threat of ground contact :
LANDING GEAR . UP
Recover to normal speeds, and select flaps are required.
In case of one engine inoperative, use power and rudder with care.
The aural stall warning may also sound at high altitude, where it warns that the aircraft is approaching the angle of attack for the onset of buffet. To recover, the pilot must relax the back pressure on the sidestick and reduce the bank angle, if necessary. When the stall warning stops, the pilot can increase the back pressure again, if necessary, to return to the planned trajectory.
At low speed the change in the speed scale is very noticeable. VLS remains, but V PROT and V MAX disappear, replaced by a single black and red strip the top of which is stall warning speed. Unlike VLS which is stable, VSW is g sensitive so as to give additional margin in turns.
As mentioned above, ALTERNATE reverts to DIRECT law for landing when the flight crew lowers the landing gear.
Roll
Roll control is direct. The rate of roll is generally higher than with normal law and at first the aircraft appears to be very sensitive.
Bank stability and protections are no longer active and the flight crew should take care to stay within normal limits.
DIRECT LAW
Normally direct law in pitch is transitory, due to undetected failures of, for example, a second IRS. Once the flight crew has isolated the failed system, it can reset the ELACs to acquire alternate law in pitch.
When the system goes into direct law, "USE MAN PITCH TRIM" appears on the PFDs. This message flashes for 5 seconds, then becomes steady.
The pilot should use small control inputs when the aircraft is in direct law at high speed, because the controls are powerful. Good trimming in pitch is required.
The pilot should avoid using large thrust changes or sudden speedbrake movements, particularly if the center of gravity is aft. If the speedbrakes are out and the aircraft has been retrimmed, the pilot should retract the speedbrakes gently, giving time to retrim so as to avoid a large nose-down trim change.
The flight crew must fly the aircraft carefully at all times. Control is precise, but there are no protections.
The aural stall warning for alternate law also serves direct law, and the technique for recovery is the same.
Any tendency to roll stick free can be corrected by conventional use of rudder. Residual rudder forces can be trimmed out by using rudder trim in the direction of the applied force.
After trimming, the sideslip index will be slightly displaced from center. With some failure conditions the asymmetric rolling tendency may be increased. It will always be possible to trim the aircraft to fly straight, hands off. There may then be an asymmetry in roll response, but the roll rate achieved is always adequate.
Landing in direct law is like landing a conventional aircraft. Trim changes to compensate for configuration changes are small, as is the trim change with speed change. Trim change with a large thrust change is quite large, so the pilot should make smooth thrust changes. The flare height for landing is the same (20 feet), and the pilot uses conventional techniques. (The controls remain light and powerful).
Pilots have landed this aircraft in direct law in moderate to heavy turbulence with gusting winds without undue difficulty.
Direct law works with or without the yaw damper. The aircraft is always convergent in dutch roll, so if an oscillation begins it will stop itself if not excited. To stop dutch roll the pilot should use lateral inputs, not rudder.
