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ELEVATOR REDUNDANCY LOST
Applicable to: ALL
INTRODUCTION
Each ailerons and each elevators are hydraulically powered either by the Green or the Blue or the Yellow circuit and are controlled either by the PRIM or the SEC. This architecture, detailed in QRH / OPS DATA, provides a high level of redundancy.
However, a combination of three failures affecting flight control computers and/or servocontrol and/
or hydraulic might lead to the loss of several ailerons and one or both elevators simultaneously. Although the aircraft can be flown in such a configuration, the F/CTL ELEV REDUND LOST procedure (triggered in case of dual failures case) has been developed to anticipate this three failure cases and is designed to smooth the aircraft handling transient.
TECHNICAL BACKGROUND
FLIGHT CONTROL ARCHITECTURE AND FAILURES
For a clear understanding, we will study the following example: Loss of the green hydraulic system and PRIM 2, which triggers the F/CTL ELEV REDUND LOST procedure, followed by a SEC2 failure.
Normal situation (before any failure)
 
 
ABNORMAL OPERATIONS
FLIGHT CONTROLS
 
Green hydraulic loss (first failure)
 
Green hydraulic power is lost. Flight controls computers will switch, this allows the ailerons and elevators to be recovered.
PRIM 2 loss (Second failure)
 
The F/CTL ELEV REDUND LOST procedure is triggered at this stage (when two failures occur). The crew should note that, at this stage, both elevators and all ailerons are available.
 
ABNORMAL OPERATIONS
FLIGHT CONTROLS
 
SEC 2 loss (third failure)
 
At this stage, both elevators are lost and only left outboard aileron is available. FAILED AILERON BEHAVIOUR
When an aileron is failed (due to failure of its hydraulic supply and/or electrical control and/or servojack), it goes to its zero hinge moment corresponding to around 14 ° up. This produces a loss of lift which creates a pitch up moment. The elevators, when available, compensate this effect.
? For the cases where three consecutive failures affecting flight controls lead to the simultaneous loss of both elevators and some ailerons, a 12 ° upwards aileron preset is anticipated (before the third failure) and the resulting pitch up effect can be compensated by the elevators (which are available at this stage) and then trimmed by the THS. This 12 ° upwards aileron preset is a compromise between fuel consumption increase (around 16 %) and the pitch up effect at the time of the third failure. This aileron preset is displayed on ECAM FCTL page. If the third and dimensioning failure occurs, three ailerons and both elevators are lost. The failed ailerons go to their zero hinge moment (14 ° up). As the ailerons were previously preset upwards (12 ° up), the transient is smooth. Only a slight upward movement occur but is controllable through the THS. MAN PITCH TRIM ONLY is displayed on the top of PFD.
　
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本文鏈接地址：A330/A340 機組訓練手冊 FCTM Flight Crew Training Manual 2(37)