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makes it possible to determine the static air temperature (SAT), which in turn
makes it possible to calculate the true air speed and in turn other parameters
such as the wind speed.
If there is a drop in the measured total pressure (obstruction of the Pitot tube),
this will therefore impact the values of all those parameters.
For example, for an A330-200 flying at FL 350 at Mach 0.8 in standard
atmosphere with a 30 kt head wind and without any disturbance in the
measurement of the TAT or variation in the ground speed, a fall in the total
pressure causing a decrease in the Mach value to 0.3 would be accompanied
by the following variations:
Mach 0.8 0.3
Standard altitude (ft) 35,000 34,700(4)
CAS (kt) 272 97
SAT (°C) -54 -31
TAS (kt) 461 182
Wind speed (kt) -30 249
(4)Due to the
correction of the
static pressure
F-GZCP - 1st June 2009
49
1.7 Meteorological Conditions
1.7.3 Meteorological Analyses
The additional analyses on the meteorological situation in the accident zone,
based on the study of the observations made at 2 h 30 UTC by the Tropical
Rain Measuring Mission (TRMM) satellite, are included in appendix 3.
Though the TRMM lightning imager indicates an absence of lightning in the
accident zone at 2 h 30 UTC, the infrared image taken at the same time is
consistent with those of Meteosat 9: taken together, this information does
not make it possible to conclude that there was a sudden and exceptionally
intense development of the convective activity between 2 h 07 and 2 h 30 UTC.
Analysis of the observations by the TRMM TMI instrument, the only one
operating in the microwave area, indicates the presence of strong condensation
around 10,000 metres altitude, lower than the altitude of the cumulonimbus
tops. This strong condensation would correspond to convective towers active
at this altitude, which confirms the strong probability of notable turbulence
within the convective cluster that was crossed by planned flight path of
flight AF447.
F-GZCP - 1st June 2009
50
1.16 Tests and Research
1.16.3 Study of losses of or temporary anomalies in indicated speeds
occurring in cruise on Airbus A330 / A340
The BEA studied thirteen events(5) losses of or temporary anomalies in indicated
speeds occurring for which it had both crew reports, parameter recordings
the PFR. The following operators made this data available to the BEA :
Air France (4 cases);
TAM (2 cases);
Qatar Airways (4 cases);
Northwest (1 case);
Air Caraïbes Atlantique (2 cases).
Several other known events were not studied in detail as a result of the absence
of adequate information. The other events recorded that could not be studied
as a result of the absence of adequate information do not call into question
the validity of this analysis (see paragraph 1.18.6).
The BEA also interviewed some crews on these flights.
The study of these events made it possible to identify several notable facts
that are analyzed in this report. Note that these analyses are made within the
strict context of this study and can in no way be interpreted as an indication
on the orientations or the conclusions of the investigation.
Analysis was, in particular, limited by the absence of recordings of some
relevant parameters. For example, the three CAS and the three angle of attack
measurements are not all recorded (at least one, sometimes two are). The
aural stall warning and the position of the probe / window heat push button
are not always recorded.
This study made it possible to identify some significant points in terms of the
environment, the automated systems and flight path control.
As far as the environment is concerned, this study shows the following points:
The flight levels were between FL340 and FL390;
The air masses were highly unstable and were the seat of deep convection
phenomena;
The static temperature was below -40 °C(6) in twelve cases(7). In ten cases,
the temperature in standard atmosphere changed from 0 °C to 6 °C; in the
three other cases it was above STD+10 °C;
The crews reported not observing any significant radar echoes on the
chosen flight path(8) but to have identified active zones nearby or lower,
which is also noted in a study by Météo France on these events undertaken
at the request of the BEA;
Three crews reported having heard or observed what they identified as
rain or ice;
(5)These are
defi ned by
the temporary
loss of reliable
indications of
one or more
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