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1.15. Survival
There were no accelerations of such a high magnitude as to produce impacts in the passenger
cabin. An emergency evacuation was not commanded, and the passengers left
the aircraft in a normal way using air stairs provided to the aircraft and were taken to
the airport with shuttle coaches.
1.16. Tests and research
1.16.1. Ground test to locate the problem
After the incident, the specialists of the manufacturer proposed to carry out a functional
check of the brake system of the aircraft following a test plan outlined in the «Technical
Disposition» of Airbus Ref. TD/B/2002/0341 (Issue 2), that basically consisted of
trying to reproduce the residual pressure in the alternate system through the use of the
pedals and the parking brake. If the residual pressure was not reproduced, then the flow
rate during the bleeding of the left and right low pressure lines (between the BDDV and
the master cylinders) should be measured to look for restriction points in the circuit. The
details of the contents of the Technical Disposition are included in Appendix B. This pro-
29
Technical report IN-062/2002
cedure was not a part of the previous maintenance documentation of the aircraft. It
was specifically prepared for the occasion after several weeks of work of the specialists
of the manufacturer.
The test was carried out and it was found that the failure produced during the incident
could not be reproduced, but the flow rate measurement showed that there was no
flow in the left low pressure circuit while the flow in the right circuit was 50 cl in 20 s.
This meant that there was no way for the return flow from chamber C1 to chamber C2
through the left master cylinder (see Figure 4), that is, that there was no “dead band”
and the pressure was trapped inside chamber C1 even when the pedal was not pressed
at all.
This could be due to one of the two following factors:
a) The master cylinder was defective, with a length longer than the 170 mm specified,
in such a way that is should be compressed when assembled in the aircraft, producing
the closure of the valve.
b) The rigging of the left pedal was defective, in such a way that the cylinder, even
having the correct length, had still to be compressed during assembly, again producing
the already mentioned closure of the valve.
The master cylinder P/N C 24592020 (Functional Item Number 5422GG), S/N H2121 was
replaced by other master cylinder off the shelf and the flow rate test was done again,
and this time a flow of 50 cl in 25 s was obtained. With this result, the specialists of
the manufacturer confirmed that the master cylinder was defective and was the component
producing the residual pressure. Pedal rigging pins were installed to confirm
correct rigging of the pedals.
The master cylinder was sent to its vendor-manufacturer, Messier-Bugatti, for a detailed
inspection and teardown.
1.16.2. Release to service of the aircraft
After the replacement of the master cylinder mentioned in the previous paragraph, the
specialists of the aircraft manufacturer issued the Trouble Shooting Report N°
3048/SEE32/TSR/1002 that confirmed that «the original master cylinder was faulty and
was the sole cause of the residual braking behaviour. Also, it is confirmed that the pedal
rigging is satisfactory». Although not specifically required by the manufacturer specialists,
the operator carried out a flight test and it was noticed that after some time most
of the pressure of the alternate brake system was lost, while the normal system functioned
correctly.
Technical report IN-062/2002
30
Then the BDDV P/N 5403GG S/N H2718 was replaced and the brake system carefully
purged. A new flight test showed that both brake systems functioned correctly and the
aircraft was returned to service.
The replaced dual valve was also sent to Messier-Bugatti for additional inspection.
1.16.3. Inspection of the master cylinder S/N H2121
The master cylinder disassembled from aircraft EC-IDF after the incident was subject to
several tests at the facilities of its manufacturer in Molsheim (France). The cylinder had
been sent in a sealed package and it was intended to retain as much hydraulic fluid inside
as possible.
The tests carried out were the following:
— Dimensional measurement: The length was 170.31 mm (the nominal value is between
170.050 and 170.100 mm). The «dead travel» was 0.58 mm (the nominal
value was between 0.4 y 0.5 mm). The total travel was 21.68 mm (the specified
value is 20.5 to 22.3 mm).
— Hydraulic fluid: the master cylinder was empty. It was not possible to recover hydraulic
fluid for its analysis.
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