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impossible to determine the condition of the initial segment of the runway
because of the use at this stage of automatic brakes in LOW mode where an
airplane is slowed down at a given rate under any runway condition (“wet” or
“covered with water”).
Aside from the reconstruction of the accident flight, the following
scenarios were also simulated (elements whose effect was assessed in every
instance are highlighted in bold italics):
№ Scenario Engine 1 Engine 2 Deceler. Spoilers Condition of
runway
1. Condition of runway
"WET", remaining
parameters similar to
those on FDR
FDR FDR FDR FDR WET
2. No forward thrust of
left engine
idle FDR FDR FDR actual
3. Same as no. 2 but with
spoilers until full stop
idle FDR FDR until full
stop
actual
4. Both TCL on idle,
without thrust reverser,
spoilers until full stop
idle idle FDR until full
stop
actual
5. Same as no. 4 but with
automatic deceleration
in LOW mode until full
stop
idle idle in LOW
mode until
full stop
until full
stop
actual
6. With maximum thrust
reverser of right engine
until 80 knots then idle,
without forward thrust,
spoilers and
deceleration same as
those on FDR
idle Max
Rev &
Reverse
Idle
FDR FDR actual
7. All as per flight
manual
idle Max
Rev &
Reverse
Idle
in LOW
mode until
full stop
until full
stop
actual
8. As in the accident
flight until 22:44:18,
then left TCL on idle
and repeated
activation of thrust
reverser of right
engine
As per
FDR,
idle
from
22:44:18
As per
FDR,
Max
Rev
from
22:44:18
FDR As per FDR,
repeated
release from
22:44:18
actual
Final Report
INTERGOVERNMENTAL AVIATION COMMITTEE
56
Here are the brief results of the analysis of each of the above scenarios3:
1. If the coefficient of friction (deceleration) corresponded to the
"wet" condition of the runway, the airplane would have stopped
700 meters before the end of the runway even given the actual
forward thrust of the left engine, which was caused by the
significantly larger (about 3 times) magnitude of the friction
coefficient for the "wet" runway condition compared to a runway
"covered with water" at speeds of about 150-180 kph, at which the
airplane trim occurred on its accident flight landing run.
2. If the left engine had remained on idle mode, then, given the actual
condition of the runway, the recorded reverser mode of the right
engine, deviations of the spoilers and deceleration, the airplane
would have stopped 500 meters before the end of the runway. It
should be noted that this scenario is clearly hypothetical since,
given the position of the left TCL on idle mode, the spoilers would
have been in the extended position.
3. If the left engine had remained on idle mode and the spoilers had
been released before stopping, then given the actual condition of
the runway, the recorded reverse mode of the right engine and the
deceleration, the airplane would have stopped 900 meters before
the end of the runway.
4. This scenario is a complete repetition of the preceding one except
for the use of the reverser on the right engine (where the reverser
was not used), which allowed us to assess the effect of the thrust
reverser that was actually applied along the length of the landing
run. The airplane stops 800 meters before the end of the runway,
that is, the length of the landing run increases by 100 meters
because the reverser on the right engine was not utilized.
5. This scenario imitates normal landing using the automatic brake in
LOW mode and spoilers until full stop without using the thrust
reverser on the right engine. The airplane stops ~800 meters before
the end of the runway, that is, the actual landing run distance is
~1700 meters.
6. This scenario allows us to assess the effect of the thrust reverser on
the right engine when it is used in strict compliance with the flight
manual recommendations. The procedure for using the brake and
spoilers is similar to that in emergency flights. There is no forward
thrust of the left engine. The airplane stops ~700 meters before the
runway threshold that is, compared to scenario no. 2 the difference
is 200 meters.
3 Simulation and analysis were carried out only to determine actual landing run distances. The airplane's possible
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FINAL REPORT ON THE RESULTS OF THE INVESTIGATION OF THE ACCI(27)
