Double Hydraulic Failure - Airbus A320 Series Instructor Support

Although this is an improbable double failure in operation, it is a dimensioning failure case for abnormal operation on
Airbus aircraft because of the following consequences:
- loss of APs,
- Flight Controls degraded law (alternate and direct law),
- landing in abnormal configuration,
- thorough use of ECAM, QRH and paper c/l and
- properly envisage different safety factors for approach and go around.
The loss of two hydraulic systems systematically causes the loss of the auto pilot system, thus the role of the PF on
stabilizing the a/c flight path will be more demanding.
Although ALTN law (with landing gear retracted) is available and quite comfortable, the handling of the a/c will be
affected by the loss of the following flight control parts or systems:
- pitch trim,
- elevators,
- ailerons,
- slats/flaps,
- brake system (normal, autobrake, alternate, antiskid),
- NWS and
- spoilers.
Major effects on a/c handling and procedures:
- Roll control is always affected by loss of spoilers. With one hydraulic system remaining, there is always one part of
the high lift devices lost (whether slats or flaps).
- Landing gear has to be extended by gravity (paper c/l) and NWS is systematically lost. In the event of loss of G +
B, the speed has to be increased to 200 kt during gravity extension to provide a good pitch control until stabilized.
The flight controls revert to direct law. To leave the runway after landing under these circumstances might become
a demanding exercise. Thus high speed turn off may preferably satisfy the demand rather than 90° turns.
- The landing will need most likely a high speed touch down as the abnormal configuration may require a greater
speed increment (i.e. VREF + 30 kt - depending on a/c version - refer to QRH chapter 2). Both normal and
alternate braking may be lost and the braking relies on yellow brake accumulator without antiskid.
- The approach after landing gear extension may require (ECAM procedure) a voluntary disconnection of the ATHR
(G + B) in order to obtain an easier a/c pitch control during approach and go around.
- In the event of loss of G + Y hydraulics, the pitch trim is lost. The procedure thus requires the landing gear
extension at VAPP at the earliest, since the integrator provides a trim with the elevator as long as the landing gear
is not extended. If this procedure is missed, the flare and the pitch control in case of go around may be difficult.
The PFD message MANUAL PITCH TRIM USE after landing gear extension should thus be disregarded.
- In the event of loss of G + Y there is high pitch during approach and go around expected (slats may be extended
only), causing a duck under during approach because of PFs eye position in relation to the runway and causing a
risk of tail strike upon touch down (A321). To properly brief the PNF to watch the pitch during approach and touch
down becomes thus essential.
- Hard pitch inputs on side stick during approach may trigger spurious stall warnings. The PF should thus manage a
well stabilized approach with the landing gear down early in order to avoid those distractions that may cause an
unnecessary go around.
DATE: JAN 2001

6 - DOUBLE HYDRAULIC FAILURE

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A320 INSTRUCTOR SUPPORT
ABNORMAL OPERATION
UDY0202