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to preserve a speed margin in the final approach speed. However, in the condition to be
possible as the wind speed suddenly decreases as following with a gust, the final
approach speed should be established with ensuring a speed margin.
Because of this, in this accident it is estimated that the First Officer, as a PF,
established the final approach speed as 143kt, calculated as VLS + 11kt, intending to take
into account both gusts and the lowering of the nose. This is close to the his maximum
value attainable using the formula VLS + ΔV that is thought to have been used by some
All Nippon Airways’ A321 flight crews based on experience.
This computation method differs from the procedure specified in AOM and, as
described in (3) above, gives a low value for final approach speed under conditions of
strong winds with gusts. Since the conditions at the time of the accident were such that
the final approach speed of 147–152kt could enable to act more appropriately due to
speed margin advantages, as described earlier, it is considered that the value of 143kt
was slightly low.
Based on the simulator flight test results, if through consideration of a gust component
a greater final approach speed had been established than that at the time of the accident,
this additional speed alone would have secured a greater margin. Further, there would
have been less reduction of thrust to adjust speed than in the accident. It is considered
possible in this case that if the value of CAS that suddenly dropped when the head wind
suddenly decreased had been able to be maintained at greater than around 144kt until
the wind shear warning sounded, the aircraft could have recovered from the same violent
wind shear conditions.
Further more, the approach with flap 3 which is thought to be possible to expand the
corresponding range that would be made greater final approach speed for wind shear
conditions, prescribed in the FCOM on Airbus Industrie, is not specifying about in AOM
on ANA.
ANA stated the reason that ANA did not describe a “flap 3 approaches” on the AOM as
follows.
“Flaps not in landing configuration warning” on EGPWS was not reflected upon “flap 3
approaches”. Thus, “flap 3 approaches” required an over-ride procedure to inhibit
EGPWS warnings that are the one of the most important safety warnings.
3.1.7 Wind Shear Recovery Maneuvers and Engine Thrust
(1) The Thrust Reduction by the First Officer prior to the Wind Shear Warning
43
In the accident, it is estimated that the First Officer, as PF, started to reduce thrust at
around 13:02:50 immediately after the increase in CAS, and accordingly the thrust lever
angles (TLA) decreased to their minimum values from 13:02:52 to 13:02:55. Subsequently,
it is estimated that although TLA began to increase slightly at 13:02:56, fuel flow reached
its minimum value of around 1,700lb/hr at around 13:02:57. The wind shear warning was
issued at around 13:02:58 with fuel flow was still remaining minimum value.
The following are considered regarding the First Officer’s reduction of thrust
immediately after CAS increased at around 13:02:50
(i) The First Officer did not recognize the possibility that the aircraft had encountered
severe wind shear nor further wind speed reductions. The note “even if sudden
airspeed increasing … do not change …” described in sub sentence 2.12.8.2 (2) is only
for wind shear but not for gusts.
(ii) The First Officer was training for upgrade to Captain, and was trying to precisely
maintain the selected CAS target value in “SELECTED SPEED” mode.
(iii) When a change in wind occurs during the engine response lag time following
manipulation of the thrust levers, it is difficult to ascertain in a short period of time
whether a change in CAS is the result of the thrust lever operation or a change in
wind. In such circumstances, it is difficult to adjust engine thrust appropriately and
it is considered possible that a pilot may reduce thrust.
(iv) Because if an approach is made at a high CAS the aircraft assumes a nose-down
attitude, there is an effect on the “FLARE” mode, and the flare out requires greater
control inputs than normal, the First Officer feared that the approach and landing
would become more difficult and over shooting touch down point.
(2) Thrust Lever Operation and Engine Response Lag during the Recovery Maneuvers
Immediately after the wind shear warning sounded, the flight crew initiated recovery
maneuvers but although the thrust levers were moved to the maximum take off thrust
positions the aircraft had already descended to around 53ft AGL. Although at around
　
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