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Therefore, the maintenance personnel and several pilots of the operator were already
familiar with the problem, and at least in one of the cases they had used several resets
of the antiskid system to make disappear the pressure, although with the fundamental
change of «pressing the (pedals) brakes at the same time». The deflexion of the pedal
was recommended by Airbus after the incident as the way to release the residual pressure
if noticed in flight (see paragraph 1.18.1). Previously, the manufacturer was not
familiar with this problem, because, according to the information gathered, they had
never received reports of actual residual pressure in flight from Iberia or from any other
operator, and attributed any clue of pressure to spurious indications, and therefore
recommended to reset the BSCU under some circumstances.
Those 5 reports of abnormalities could have contributed to prevent the incident on 7-
9-02 if, from an operational point of view, the information on abnormalities had been
provided to the crews of A-340, it is possible that the pilots of the flight of the incident
would have been familiar with the situation and with the actions taken is similar cases.
Also, if from a maintenance point of view, they would have been more thoroughly
investigated by the personnel of the operator, contacting with the manufacturer as
needed, maybe the origin of the residual pressure would have been detected at that
point. The manufacturer stated that high brake temperatures (that appeared in the
first two squawks) were clear clues to indicate that the residual pressure was not
spurious. Additionally, the analysis of the TSM carried out by the manufacturer showed
that, with the available clues and indications, the task 32-40-00-810-927 should
have been applied, at least after the third squawk according to the TSM introduction
(see 1.6.5).
However, it remains doubtful that the application of this task in an isolated way by the
personnel of the operator would have detected the faulty component and led to the
replacement of the master cylinder. The task (see 1.6.5) requests a fault confirmation
by means of setting the parking brake to OFF and then looking for pressure in the triple
indicator. Since the residual pressure had an intermittent nature and was no longer
present after the landings in June, maybe their interpretation would have been that this
«fault confirmation» action had failed and therefore the rest of the TSM task would not
47
Technical report IN-062/2002
have been completed. Apparently they were not aware of the intermittent fault concept
mentioned in the introduction of the TSM.
Since the TSM has been designed to isolate/troubleshoot hard faults, it is considered
that the possibility of dispatching the aircraft until having 3 intermittent occurrences of
the same phenomenon should be further analysed by the manufacturer, and some additional
guidance should be provided in the TSM introduction. To avoid any confusion, it
should be highlighted in pertinent parts of the TSM that all available clues must be carefully
considered before dispatching again an aircraft after the first and second occurrences.
The operator also stated that they considered the instructions of the TFU should be
applied in first place, and those instructions were not consistent with those contained
in the Trouble Shooting Manual in this matter (i.e. the TFU did not refer to the proper
TSM procedure). Therefore, they applied that TFU alone on the first two days of
squawk.
On the third day (there was no high temperature reported that day) they also checked
transducers, status and condition of dual valve, master cylinder, and filter, and they performed
a system test and BSCU test. The transducer, dual valve, cylinder, and filter are
mentioned in the task -927 (see 1.6.5), although no task was specifically recorded on
the logbook and no component was replaced.
On the fourth day (with no high temperature reported) only the BSCU test and reset
were carried out, which would correspond to the TFU instructions.
The fifth and last day (with no high temperature reported), it seems a mixture of tasks
was performed, including checking of pressure in the left leg, cleaning of transmitters,
test of BSCU, and checking of wheels free to rotate. Then the squawks ceased.
The operator stated, late in the investigation process, that an operational test of the
brake system was carried out that day (11 June 2002), to be sure that the brake system
was free of any trouble. That test is the last action of TSM task -927.
The manufacturer stated that the appropriate manual to be applied is the TSM, regardless
of other ad-hoc maintenance information that may have been issued. The TFU was
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