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as ‘If it must be considered with a gust in A321 airplane, the aircraft nose goes down as
making airspeed high excessively, then it happens to obstruct to safe landing. However, the
final approach speed should have been established in sufficient for the strong wind with a
gust. In order to cope with both matters, the airspeed with the limit of VLS + ΔV, maximum
value of 12 ~ 13kt, is established normally’. Further, according to the data issued by ANA, it
is described as the aircraft nose would go down to minus at over the speed of VREF + 17kt on
the almost same gross weight at the accident.
2.12.7 “SELECTED SPEED” mode and “MANAGED SPEED” mode
In AOM issued by ANA on A321 Airplane, two kinds of modes of “SELECTED SPEED”
and “MANAGED SPEED” were established related to the establishment of a final approach
speed. However, if making an approach by manual control for thrust lever, it is specified to
establish the final approach speed with “SELECTED SPEED” mode, and then “SELECTED
SPEED” mode had been also used at the time of the accident.
(1) “SELECTED SPEED” Mode
“SELECTED SPEED” mode established by ANA means that it is the control method for
thrust lever generally used as usual and the thrust lever is controlled to maintain CAS
constantly. In this “SELECTED SPEED” mode, the thrust lever is controlled for following
the standard with the appropriate thrust (Target thrust) which the approach speed might
be maintained regularly. If the head wind component increased during a flight, while
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CAS might be increase momentarily by the aircraft inertial force, CAS is stabilized to the
original speed after momentary irregular phenomenon recovered if not controlling to
reduce thrust. However, as a result that it is necessary to decrease rate of descent in
order to track on glide path because the ground speed reduces, it is required to slightly
increase the thrust a little more than the target speed. Further, as the time of the
accident, if having made the thrust reduce to maintain CAS at sudden increase of the
wind speed, in order to recover to the original CAS and to track again on glide path after
momentary irregular phenomenon recovered it is required to largely increase the thrust
more than the target speed to compensate for decreased rate of the ground speed.
Moreover, because CAS reduces as the head wind suddenly decreased, it is resulted that
the pilot increases the thrust, and then he controls to continue an approach as putting
back the target thrust with reducing the thrust after the airspeed got back to the preselected
value of CAS.
As rearranging the characteristic for “SELECTED SPEED” mode, it is as follows:
(i) In “SELECTED SPEED” mode, the pilot establishes the final approach speed as
making airspeed constant with considering to VAPP, average wind speed, gust
component, etc.
(ii) In the case the wind speed changes, as a result that CAS of the airspeed changes if
it is, it is the approach method to control as keeping the final approach speed
constant by increasing or decreasing thrust.
(iii) In the case the wind speed changes in precision approach, it is required to change
the rate of descent in order to continue to track on glide path because the ground
speed changes.
(iv) It is able to control the thrust by manual or by auto-thrust.
(2) “MANAGED SPEED” Mode
In “MANAGED SPEED” mode, the thrust is controlled to keep the ground speed
constant. In this mode, when the wind speed changes largely, it is resulted that target
CAS is changed automatically. This mode is established to relieve the effect from the
wind-shear. While CAS increases if the head wind component largely increased, the
engine thrust increases contrary to “SELECTED SPEED” mode to keep the ground speed
constant. Further, Even if CAS suddenly decreases by sudden decrease of the head wind
and by sudden increase of the following wind, it is specified to establish the final
approach speed up to the minimum speed of VAPP. Because of this, it is resulted that the
engine thrust is kept in the high condition and is maintained the kinetic energy of the
aircraft against the sudden decrease being peculiar at encountering the wind-shear, as it
happens after sudden increase of the head wind.
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Still more, although this mode is supposing to the auto-thrust, even if the thrust is
controlled by manual, it is possible to make an approach with “MANAGED SPEED” mode
by that the pilot controls the thrust lever as following the airspeed indicated on PFD.
As rearranging the characteristic for “MANAGED SPEED” mode, it is as follows:
　
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