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DESCENT
A330/A340 FLEET NO-080 P 1/8
FCTM 17 JUN 09
PREFACE
Applicable to: ALL
The PF will set preferably the MCDU PROG or PERF page as required (PROG page provides
VDEV in NAV mode and BRG/DIST information, PERF DES page provides predictions down to any
inserted altitude in DES/OP DES modes) whereas the PNF will set the MCDU F-PLN page.
In mountainous areas, the selection of the TERR ON ND sw enhances pilot awareness and can be
used in any flight phase.
If use of radar is required, consider selecting the radar display on the PF side and TERR on PNF
side only.
COMPUTATION PRINCIPLES
Applicable to: ALL
TOD AND PROFILE COMPUTATION
The FMGS calculates the Top Of Descent point (TOD) backwards from a position 1 000 ft on
the final approach with speed at VAPP. It takes into account any descent speed and altitude
constraints and assumes managed speed is used. The first segment of the descent will always be
idle segment until the first altitude constraint is reached. Subsequent segments will be "geometric",
i.e. the descent will be flown at a specific angle, taking into account any subsequent constraints. If
the STAR includes a holding pattern, it is not considered for TOD or fuel computation. The TOD is
displayed on the ND track as a symbol:
Descent path
The idle segment assumes a given managed speed flown with idle thrust plus a small amount of
thrust. This gives some flexibility to keep the aircraft on the descent path if engine anti-ice is used
or if winds vary. This explains THR DES on the FMA.
The TOD computed by the FMS is reliable provided the flight plan is properly documented down to
the approach.
A330/A340 FLIGHT CREW TRAINING MANUAL
NORMAL OPERATIONS
DESCENT
A330/A340 FLEET NO-080 P 2/8
FCTM 17 JUN 09
MANAGED DESCENT SPEED PROFILE
The managed speed is equal to:
• The ECON speed (which may have been modified by the crew on the PERF DES page, before
entering DESCENT phase), or
• The speed constraint or limit when applicable.
GUIDANCE AND MONITORING
Applicable to: ALL
INTRODUCTION
To carry out the descent, the crew can use either the managed descent mode (DES) or the
selected descent modes (OP DES or V/S). Both descent modes can be flown either with selected
speed or managed speed.
The modes and monitoring means are actually linked.
The managed DES mode guides the aircraft along the FMS pre-computed descent profile, as
long as it flies along the lateral F-PLN: i.e. DES mode is available if NAV is engaged. As a general
rule when DES mode is used, the descent is monitored using VDEV called "yoyo" on PFD, or its
digital value on the PROG page, as well as the level arrow on the ND.
The selected OP DES or V/S modes are used when HDG is selected or when ALT CSTR
may be disregarded or for various tactical purposes. As a general rule when OP DES or V/S
modes are used, the descent is monitored using the Energy Circle, (displayed if HDG or TRK
modes and indicating the required distance to descend, decelerate and land from present position)
and the level arrow on the ND. When the aircraft is not far away from the lateral F-PLN (small
XTK), the yoyo on PFD is also a good indicator.
MANAGED DESCENT MODE
The managed descent profile from high altitude is approximately 2.5 °.
As an estimation of the distance to touchdown is required to enable descent profile monitoring, it
is important to ensure that the MCDU F-PLN plan page reflects the expected approach routing.
Any gross errors noted in the descent profile are usually a result of incorrect routing entered in the
MCDU or non-sequencing of F-PLN waypoints, giving a false distance to touchdown.
DESCENT INITIATION
To initiate a managed descent, the pilot will set the ATC cleared altitude on the FCU and push
the ALT selector. DES mode engages and is annunciated on the FMA. If an early descent
were required by ATC, DES mode would give 1 000 ft/min rate of descent, until regaining the
computed profile.
A330/A340 FLIGHT CREW TRAINING MANUAL
NORMAL OPERATIONS
DESCENT
A330/A340 FLEET NO-080 P 3/8
FCTM 17 JUN 09
To avoid overshooting the computed descent path, it is preferable to push the FCU ALT selector
a few miles prior to the calculated TOD. This method will ensure a controlled entry into the
descent and is particularly useful in situations of high cruise Mach number or strong tail winds.
If the descent is delayed, a "DECELERATE" message appears in white on the PFD and in
amber on the MCDU. Speed should be reduced towards green dot, and when cleared for
descent, the pilot will push for DES and push for managed speed. The speed reduction prior to
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A330/A340机组训练手册FLIGHT CREW TRAINING MANUAL(46)
