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Old 20th Apr 2010, 20:44
  #837 (permalink)  
Uphill
 
Join Date: Apr 2010
Location: Poland
Posts: 9
how it could be

these posts are from Sergey Amielin blog made by Tom tu154 pilot
"Considering horizontal visibility 400m if they had under the plain flat terrain
crew would start to see anything in front of them after being at height approx 40m above
terrain.At approach speed 70m/s which was correctly astimated with acuracy -2/+8 ms
plane flied in best case after 6 s at place which crew managed in best case see
6s earlier."
"on tu-154 taking into account time needed for turbine to reach starting power and
plain inertia at mass about 65 ton especially at ascendnig terrain 6s
is a bit to little time to go from normal height decresing to incresing and not touching
the ascending terrain"
"not considering wrong setup of MDA/MDH or wrong given/set QNH/QFE crew probably
decided to use RA in order to get at 40-50 m AGL about 1 km before threshold
only from this hight they had a chance to land at visibility 400m whicch above
forest before runway could be even worse. For some reasons they did not control
barometric altimeter and did not notice they got 10m under threshold of the runnway
(255 m above see level)"
"they had a chance to succceed if not the deep ravine seen on google earth.
Observing that they are constantly high (according to RA because of ravine)
they increased lowering speed, later they saw in the end terrain going up
in front of them, being at about 40-50 m above ground, initiated dramatic go-around,
but it was to late"
"it's possible they could support themself with FMS, using its simplest functions
(unfortunately not VNAV) and manually set threshold coordinates and landing course.
As well to estimate distance to threshold. Unfortunately a lot points it was
not set correctly or if at all."
"it's bad this airport was not measured with WGS084 (PZ-90). If it was
and was placed in AIP it would be also in database EGPWS and FMS. Corrrect use
of FMS especially its advanced functions could prevant tragedy.Our reconesance
would be usefull when airport was used many times, including bad weather.
Airport mesurement and obstacles as well"
"but MDH 120 m rather would not change. and what goes with it visibility condition
1000-2400 m would remain. Approach lower is a break of basic safety rules.
Does not matter with EGPWS or FMS or without them"
"i would like to be wrong but i am afraid that CVR recorded "turn off EGPWS,
to not scream airport not found in database" or "we ignore EGPWS - this aiport
is not in database". We will hear also "we approach according to RA so
that at 1 km before threshold/passing BLR we will be at 30/40/50 m. Otherwise
with this visibility we can not make it, and we can not not to try"
"Anybody knows if Outer NDB located 4 km from the threshold exists? I can't located in Google
Earth, while the Inner NDB can be located 1 km from the THR in Google Earth"
"as i wrote before, terrain in front of him he would be able to see
being at apprx. 40 m above ground (but when terrain is flat, when it goes up/down
it could be a little more or less). It would be good if Siergiej could make this
picture to the right about 500 m apposite approach direction. This would allow
to estimate the moment he noticed the terrain"
"Сергей, could you please be so kind and extend the picture about 500 m to the right, in the
direction opposite to the approach direction, so an analysis can be made when the crew was able
to see the terrain, considering 400 m visibility. They had to be approx. max. 40 m above ground
level, maybe lower, when they saw the terrain and trees in front of them."
"Сергей, are you aware of existance of Outer NDB, located usually 4 km from the runway
threshold? I can't find anything which looks like NDB facility anywhere on extended runway
centerline, except for Inner NDB, 1 km from the threshold. using Google Earth"
"Continuing, with terrain going up and visibility 400m crew could notice terrain if front of
them later at a bit lower height apprx. 30 m above ground. On the other hand with
terrain going down crew could see terrain if front of them at a bit higher height
appox 50 m above ground. Analizing earlier profile i conclude that crew noticed terrain
being approximately above ravine bottom, or rather 100 m after it. being at height
apprx. 260 m over see leverl (5 m over threshold level)"
"Peter, as i said earlier it is possible crew did not notice in previous flights
slightly hilly terrain on approach and deciding sickly to land even if it meant
break the rules and common sense, concentrated on reading radioaltimeter.
turning off in the end scanning barrometer altimeters. Knowing that
in these visibility conditions they will see ground at approx 10 seconds
before touchdown. Everything happens than very quickly."
"Becouse ravine bottom goes about 50 m below runway threshold, they increaced
lowering speed thinking they are to high. They saw terrain going up being
a few meters about threshold level. But lowering at 6-7 m/s, weighing ap. 60-70
ton Tu 154 configured to landing can not be forced to ascend in a second.
You loose next 15-20m and fly in this time ap 350-400 m before
transisioning to ascending - in first seconds free"
"it takes a few second before plain reaches his max accending speed
in landing configuration. At the same time it is only after reaching
positive ascending that the chasis is hiding and position of
flaps to starting position decreases eg from 40 to 20 degrees.
This takes anogther few several seconds. I think crew using radio altimeter
wanted to approach to aprox. 50-60 m above ground and only than
do eventually go-around. It was not reasonable."
"additionally they forgot about ravine which bottom was about 1300 m from threshold
If it was not there if terrain was flat as they assumed they would manage to land.
but it seems to me that with 400 m visibility and approach speed
apprx. 135 knots (70m/s) little probable. or they would do succesful go-around.
Landing with ILS cat I approached to 60 m abouve ground,
and with cat II even to 30 m legally. Tu 154 has autopilot with function
autoland but you need ILS for that. It was not there."
"i think if they did not see terrain using radioatimeter about 2 seconds
later they would start go around. They were not suiciders only they
had to high selfesteem. How do i know? Because i have a few landing like that
behind me. and it also seemed to me that published minimas are for loosers
and not "ases" like me. Only i had a little more luck and stayed alive to point when
i was able to kick these ideas out of my head"
"aha plane found itself at lowest point 10m aprox. 245 m abouve see level)
under threshold runway level and not several dozen meters."
"Сергей, спасибо. It means probably only 1 or 2 NDBs and approach monitoring radar. No PAR. The
question is only: 1 or 2 NDBs?"
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