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Pegasus Airlines Boeing 737-800 TC-CPF overrun runway at Trabzon. All pax okay

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Pegasus Airlines Boeing 737-800 TC-CPF overrun runway at Trabzon. All pax okay

Old 15th Jan 2018, 07:21
  #81 (permalink)  
 
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Originally Posted by Volume View Post
They obviously have to use full runway to do a 180į backtrack
No they don't.

While there is indeed a turning area at the end (enlarged recently), the video in post #70 clearly shows another Pegasus B738 performing a 180 on the runway itself (to save time?).
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Old 15th Jan 2018, 07:33
  #82 (permalink)  
 
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Agreed, there is no need to use the pad. Most operators in Turkey use the runway, saves time and stops half the pax from standing up after touchdown!
They were doing the backtrack turn (as post 70) and put the nosewheel on the grass, at that point they would have had no nosewheel steering to speak of. Then symmetric thrust just carried them straight on over the edge at taxi speed.
Unlikely, the turn would be to the right then left, which would put the aircraft the other way round. Also there is a about 10 metres plus of land between the runway edge and the escarpment at Trabzon, hence if the nose wheel went on the mud, they would just stop. Turkish TV records passengers saying aircraft was sliding and twisting before a loud crash and rapid nose down attitude.
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Old 15th Jan 2018, 07:48
  #83 (permalink)  
 
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Originally Posted by Airclues View Post
In the video in post 43 there seems to be a flash during the landing roll......
I agree. Appears to be an orange flash at the 19sec mark on that video.
Hard to say what, but an engine surge/stall is definitely a candidate.
Nasty dark wet night too, no doubt slippy runway.
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Old 15th Jan 2018, 08:21
  #84 (permalink)  
 
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First Officer is pf, weather is at minimums. They are expecting to see the runway at minimums. At minimums they see the runway and the first officer disangages the autopilot but at the same time he presses the toga buttons. Captain takes over and lowers the nose and retards both thrust levers to idle, they land at idle thrust and aircraft was dispatched with one reverser inop. The captain deploys the thrust reverser of the left engine and releases the right engine. Since he hadn't disconnect the auto throttle right engine goes to TOGA thrust. Aircraft starts to accelerate and skids off the runway from the left. Right engine saparates. All passengers evacuate the aircraft from the rear door. No smoke in the cabin no injuries.
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Old 15th Jan 2018, 08:34
  #85 (permalink)  
 
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Originally Posted by Kulverstukas View Post
.

Lots of runway behind the aircraft.
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Old 15th Jan 2018, 08:43
  #86 (permalink)  
 
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Originally Posted by Avenger View Post
Unlikely, the turn would be to the right then left, which would put the aircraft the other way round.
Have a look at the video at post #70, the initial turn is to the left and then back hard towards the right.
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Old 15th Jan 2018, 08:45
  #87 (permalink)  
 
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Originally Posted by Avenger View Post
A Unlikely, the turn would be to the right then left, which would put the aircraft the other way round.
No, have a look at the video in post #70, they perform a left swing followed by right backtrack, in almost exactly the same place as the accident.
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Old 15th Jan 2018, 08:54
  #88 (permalink)  
 
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I have seen bird strikes get caught up in the nose steering cables on 737ís before

Remember the KLM runway excursion in BCN due nose wheel steering malfunction.

I know bats are not strictly birds, but hey, they are nocturnal aviators.
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Old 15th Jan 2018, 08:58
  #89 (permalink)  
 
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The OEI G/A performance is markedly better than 5% grad, not an issue
Itís about 5% at MLW with 26k engine.
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Old 15th Jan 2018, 09:28
  #90 (permalink)  
 
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No, have a look at the video in post #70, they perform a left swing followed by right backtrack, in almost exactly the same place as the accident.
Just because this PGS does this, it doesn't mean its a procedure.Most aircraft making a normal touchdown can vacate at the second taxi way without backtrack. (plenty of you tube vids on this ) some make a move to parallel the centre line to the left before turning right, but its nothing like a sharp turn. We will know more tomorrow
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Old 15th Jan 2018, 09:46
  #91 (permalink)  
 
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Originally Posted by OnTheNumbers View Post
First Officer is pf, weather is at minimums. They are expecting to see the runway at minimums. At minimums they see the runway and the first officer disangages the autopilot but at the same time he presses the toga buttons. Captain takes over and lowers the nose and retards both thrust levers to idle, they land at idle thrust and aircraft was dispatched with one reverser inop. The captain deploys the thrust reverser of the left engine and releases the right engine. Since he hadn't disconnect the auto throttle right engine goes to TOGA thrust. Aircraft starts to accelerate and skids off the runway from the left. Right engine saparates. All passengers evacuate the aircraft from the rear door. No smoke in the cabin no injuries.
And your source is?
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Old 15th Jan 2018, 09:57
  #92 (permalink)  
 
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Someone in that company....
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Old 15th Jan 2018, 09:59
  #93 (permalink)  
 
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The word on the ground is an uncommanded thrust increase on engine 2 which took them off the runway
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Old 15th Jan 2018, 10:01
  #94 (permalink)  
 
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Also heard there are five recent occurences of the the same
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Old 15th Jan 2018, 10:04
  #95 (permalink)  
 
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Originally Posted by Avenger View Post
Just because this PGS does this, it doesn't mean its a procedure. Most aircraft making a normal touchdown can vacate at the second taxi way without backtrack. (plenty of you tube vids on this ) some make a move to parallel the centre line to the left before turning right, but its nothing like a sharp turn.
I suppose it depends on your definition of "sharp turn". It looks like a standard 30į RET for traffic landing on 29, which makes it a 150į turn if you're coming from the 11 end.

But either way that's irrelevant, the debate was whether the incident was a 180 that went wrong, and your assertion that

Originally Posted by Avenger View Post
Unlikely, the turn would be to the right then left, which would put the aircraft the other way round.
I'd suggest that, unless Pegasus is one of the few airlines that has paid Boeing the hefty premium to have the optional tiller on the RHS of the 737NG, a 180 will be in whichever direction the Captain decides to execute it.

Though if it was a runaway engine, it's all pretty academic.
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Old 15th Jan 2018, 10:16
  #96 (permalink)  
 
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The turning issue is a bit of a red herring TBH, as observed, the Captain will decide according to his/her wishes. I am curious to understand how a 737NG can still have TOGA auto throttle more than 2 secs after ground air switch senses touchdown or with a TRA split of more than 10 degrees? This theory would mean they landed with the A/T armed and then somehow pressed TOGA before 2 secs and then selected asymmetric reverse? seems like far too may swiss cheese holes! Regarding info from "someone on the ground" having been based in Trabzon for 6 months I would take that with a very large pinch of salt..
Of course being Turkey its possible the Captain lit a cigarette and dropped it, lent forward to catch it and opened the T/L, after the Correndon fire at AYT due smoking we wouldn't be surprised!

Dongle..Can you provide refs for the uncommanded asymmetric TL movements please
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Old 15th Jan 2018, 11:14
  #97 (permalink)  
 
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From an Indian news site:

The pilot, co-pilot and crew have now made statements to Trabzon prosecutors and both pilots passed breathalyzer tests, the Dogan news agency said.

"When we were going to make our usual manoeuvre towards the right from the seaside by reducing our speed, the right engine suddenly gained speed for a reason we do not know," the pilot was quoted as telling the prosecutors.

"Due to this speed, the plane got out of our control and suddenly swung to the left and got stuck into the mud in the cliff."

www.ndtv.com
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Old 15th Jan 2018, 11:16
  #98 (permalink)  
 
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Originally Posted by OnTheNumbers View Post
First Officer is pf, weather is at minimums. They are expecting to see the runway at minimums. At minimums they see the runway and the first officer disangages the autopilot but at the same time he presses the toga buttons. Captain takes over and lowers the nose and retards both thrust levers to idle, they land at idle thrust and aircraft was dispatched with one reverser inop. The captain deploys the thrust reverser of the left engine and releases the right engine. Since he hadn't disconnect the auto throttle right engine goes to TOGA thrust. Aircraft starts to accelerate and skids off the runway from the left. Right engine saparates. All passengers evacuate the aircraft from the rear door. No smoke in the cabin no injuries.
During landing phase, the aircraft systems receive an "on the ground" information from the Flt/Gnd switches, spoilers are deployed, left engine reverse thrust applied. If in this situation the A/T can command TO/GA thrust on a single engine, I would say that this a serious design flaw.

As far as I know, if the aircraft has been dispatched with the right reverse inop, the reverse mechanism will be locked by the technical staff and if the pilot activates the reverse thrust levers only the left engine would go to reverse mode. Would a pilot in such a situation pull only the left reverse lever or both (instinctively)? Or is there a defined procedure which prohibits the pilots to activate an inoperative reverse thrust lever during landing?

Why I am asking this?

Let's say that the captain as taken over the controls and landed the aircraft safely. If he would activate both reversers the autothrottle would not be able to advance the right thrust lever to TO/GA thrust position because the pilots right hand pulls the levers back. Only after cancelling the reverse thrust the captain can remove his right hand from the throttle. By this time the aircraft must have decelerated to 60 kts. Let's say the right engine goes to TO/GA mode at this point. It would take a couple of seconds for the full thrust to developed. During this time the pilots should have noticed this problem and retarded the thrust levers (in my opinion).
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Old 15th Jan 2018, 11:48
  #99 (permalink)  
 
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Aquaplaning marks arenít easy to see.

Originally Posted by LongJohn54 View Post
Post 23 Quote-
The skid mark that can still be seen on the runway (picture below) already has a large angle from the runway centerline.
-Quote


I cannot see any skid marks on the runway. Watching the video posted earlier you can see two people walking along the runway and that is what is being mistaken for skid marks.
This photo is taken from the beginning of the video.
I searched in google aquaplaning marks on runways and believe me from the pictures I saw isnít easy to see them unless a good closeup picture is taken; which make sense because aquaplaning is the fenomena when the tires detach from the runway for a x time. I think from this pictures is difficult to see them. Less wait for a closer picture of the runway.
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Old 15th Jan 2018, 12:01
  #100 (permalink)  
 
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Originally Posted by Avenger View Post
I am curious to understand how a 737NG can still have TOGA auto throttle more than 2 secs after ground air switch senses touchdown or with a TRA split of more than 10 degrees?
Even if they touched down long, they clearly managed to maintain the centreline for quite some time before making an unplanned trip to the beach. The theory doesn't hold water.

Perhaps the pilot taxied to the left of the runway in order to execute a right turn, with the intention of using thrust from the no.1 engine to assist the right turn, with steering from the nose wheel, which lost traction as he inadvertently pushed the no.2 thrust lever forward... But that's pure speculation.
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