曝光台 注意防骗
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arms. Signals from the resolver to the FADEC arrived in electronic
form. FADEC did not have any feedback coupling with the
mechanical portion of the engine control cable. After the accident
one actuating rod of the mechanical portion of the left engine control
cable, directly adjacent to the TCL, was found. Connections on it
were fastened and secure. Based on all available data and a
schematic analysis of the engine control system, the engineering
sub-commission came to the conclusion that any malfunction of the
mechanical portion of the control cable or failure (kinematic
destruction) of the airplane's engine control system was extremely
improbable;
• the thrust on both engines, recorded by the FDR as the airplane was
on its landing run along the runway, corresponded to the calculation
of the recorded position of the TCL/RTL and the actual conditions at
Irkutsk airport.
• the functioning of the limit switches responsible for the automatic
retraction of the spoilers and blocking of the reverser activation,
which actually serve as auxiliary and independent TCL position
sensors, occurred in the recorded positions of the TCL for the left
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INTERGOVERNMENTAL AVIATION COMMITTEE
99
engine corresponding to the marked (theoretical) positions (10 and
22 degrees TLA, accordingly);
• the recorded deceleration loads were insufficient for any selfmovement
of the TCL forward, even if the friction coupling
applying additional forces on the TCL failed completely;
• over the entire history of operation there was no case of failure or
malfunction that would have led to the mutual mechanical meshing
of the engine control cables. The penetration of foreign objects that
could create a "semirigid connection" working only in one direction
between the control cables of the two engines was practically
impossible because of the principles inherent in the TCL design. All
prior failures of the mechanical portion of the engine control cable
were related to jamming (impossibility to move) of the cable for
various reasons.
Thus, the movement of the left engine TCL, as recorded on the FDR,
where the thrust reverser had been deactivated, to increase forward thrust,
really occurred and was a consequence of the involuntary and uncontrolled
actions by the airplane captain during his efforts to control the thrust reverser
on the right engine on the run after landing.
Results of experiments conducted on А-310 airplane with P&W engines
(section 1.16.4) showed that, because of a weakening of the friction coupling's
pull, the forces needed to move the throttle control lever can be greatly reduced
during operation, up to ~400 g, which is practically 3 times less than the
minimum permissible amount indicated in the AMM (1.17 kg) and corresponds
to the control cable's own friction forces, without any additional forces coming
from the friction coupling.
Note: Existing technical maintenance documentation
(MPD) of the A-310 airplane did not provide for the
periodic inspection and adjustment of the forces. This
work is carried out at irregular intervals at the request
of flight crews whenever they feel uncomfortable in
controlling the throttles. There was no such record
found in the log book of the accident airplane.
Considering the fact that the age and number of flight hours of this airplane
exceeded those of airplane that took part in the experiment and, bearing in mind
the effect of the deceleration loads with an average amount of 0.17 g, which
additionally reduces the forces needed to move the TCL forward, one can
assume that the forces needed to move the TCL during the accident flight were
relatively small. The presence of shakes and vibrations that were typical of the
Final Report
INTERGOVERNMENTAL AVIATION COMMITTEE
100
runway at Irkutsk airport could have made the uncontrolled forward movement
of the TCL even more unnoticeable by the airplane captain.
While the reverse thrust program of the right engine was in progress and
maximum value of the reverse thrust level of 1.218 as per EPR was reached at
22:43:54, the average level of longitudinal deceleration was ~-0.17 unit, without
the crew pressing the brake pedals. This attests to the working condition of the
automatic brake system in LOW mode (ensuring deceleration with continuous
slowdown -1.7 m/s2).
Note: According to the results of a simulation, it was
established that the thrust of both engines as recorded
by the FDR during the airplane’s landing run on the
runway corresponds to that calculated for the
recorded position of the TCL/RTL and the actual
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