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Saudi Airline B777-300

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Saudi Airline B777-300

Old 1st May 2013, 18:04
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Not knowing what's factual vs speculation

what's the possibility that the event happened on taxi out and that the plane was tugged back to a stand and disconected and nothing happened between a tug and the plane to cause the event?

Last edited by lomapaseo; 1st May 2013 at 18:04.
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Old 1st May 2013, 18:14
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Originally Posted by Lonewolf_50
... the pilot who tried to take off from an apron.
Read more carefully. He tried to take off from a runway near the airport...

Originally Posted by lomapaseo
what's the possibility that the event happened on taxi out ?
Would not discount it completely, but that would sound too simple. During my time in the fine land of the sand, I have learnt to expect the most absurd, illogical and unlikely explanation to be the real one...

Last edited by andrasz; 1st May 2013 at 18:20.
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Old 1st May 2013, 18:26
  #23 (permalink)  
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what's the possibility that the event happened on taxi out
- skid marks?
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Old 1st May 2013, 18:28
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andrasz
What is it about
If one were to take this newspaper statement at face value
that you don't understand?

Do you understand why I put the in there?

In case you were unsure, I was poking fun at the "art" of journalism there.

I did indeed read the whole article.

Cheers.
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Old 1st May 2013, 19:00
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That -115b puts out a massive amount of thrust. My guess from the picture, engine or engines running, tug driver is in a sharp turn snaps tow bar, aircraft rolls into tug, tug driver ****'s his pants, women and children scream.
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Old 1st May 2013, 19:28
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driver ****'s his pants,
Oh those skid marks
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Old 1st May 2013, 19:32
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Lonewolf_50,

...runway...near...airport...

I was just topping your , take it easy
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Old 1st May 2013, 19:42
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Aha, well played, I guess that went over me at about FL 250.
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Old 1st May 2013, 19:57
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MELDreamer’s input to the story says that the engine went to full power (post #13).

Many years ago, my airline had that once during engine start on a DC-10. Throttle cable had been moved and misrouted during maintenance, so that the inner cable was in a pulled state at the main engine control end, while the thrust lever on the flight deck was in the normal idle position. One of the rpm's, I think N1, was above 80% and rising before the fuel cut-off was effective, if my memory serves me right. Hair-raising experience, as the Flight Engineer told me when they came back into the office. I think I still remember which F/E.

Back to JED. With brakes off, and given a similar malfunction, a 777 loaded for this short trip might begin to advance against the tug and then break out of line to the side where the tug isn’t. Towbar shear pins snap; the a/c moves further forward. By the time the flight deck is aware that they not only have a runaway engine, but a runaway airplane as well, the tug is hit by the engine inlet. The skid marks on the ramp near the inlet may have to do with the uncommanded turn induced by differential thrust and/or the angle of the nose wheel that was steered by the towbar until shear pin break-off.

So maybe, if you accept the uncommanded accelerating engine, the rest does not appear to be excessively wild phantasy?

Last edited by Plumb Bob; 1st May 2013 at 20:10.
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Old 1st May 2013, 20:58
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A similar incident happened to a 777 years ago, in that particular case the thrust levers were not at idle they had been moved (after all checklists/flows were complete) to rectify and unrelated maintenance issue, crew failed to notice the position (human factors) Eng 2 started first, reached idle and rapidly accelerated to a high thrust, broke the tow bar and the A/C moved forward and yawed left instantly due to the asymmetric thrust thereby missing the tug with the nose gear, also the tug now accelerated towards the aircraft or engine. The crew were able to stop the aircraft before contacting the tug, had it been powered by GE90-115 maybe they would have hit the tug.

My guess is its a similar incident, and questions asked as to the reason for the thrust increase, thrust lever position or EEC fault?

Last edited by SMOC; 1st May 2013 at 21:16.
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Old 1st May 2013, 21:07
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Tug jump

And that was.... Hmmm ..an A6 aircraft I think... But not allowed to post operators are we ... Didnt get any nice pics on pprune but.
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Old 1st May 2013, 21:32
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Theory

Based on the photo in post 5.

There appear to be 3 sets of skid marks visible in the photo:
1: opposed cresents just in front of the engine;
2: large radius arc splitting to 2 tracks in the foreground;
3: (possibly) behind the inboard main gear wheels.

Marks #1 from tug which doesn't move much but is rotated ~90° right during the "manoeuvre".

Mark #2 traces the arc of the nose gear, radius = nose gear to tug centre of rotation, as the a/c rotates to its left. Track splits into two when the shear pin lets go and gear steers left.

Mark #3 caused when crew apply brake (parking brake?) and also indicates a/c rotation to its left.

So, the ballet started with the tug in position indicated by marks #1 and the a/c further back and with a heading maybe +30° to +90° compared to its final heading. Towbar probably close to a/c axis.

No.2 engine goes to high power. A/c brakes are off. Tug brakes are on. No.1 engine may not have started yet or is spooling up or at idle. Monster resulting torque is enough to skid the nose gear to the a/c's left. Shear pin goes when the nose gear steering angle limit is reached. Crew apply brakes. Tug driver ****s his pants. Tug contacts inlet and rattles around against it until No.2 is shut down.

Last edited by SyEng; 4th May 2013 at 22:52. Reason: spelling
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Old 1st May 2013, 23:53
  #33 (permalink)  

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Name and Blame Saudi style

Punishments? Throttle hand excisions? Local laws are known to be harsh and nonsensical )
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Old 2nd May 2013, 00:18
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My guess is its a similar incident, and questions asked as to the reason for the thrust increase, thrust lever position or EEC fault?
Nothing comes to mind with a FADEC runaway to me. Everything is so redundant.
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Old 2nd May 2013, 00:25
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Yea I was trying to be kind, I seriously doubt a engine fault.
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Old 2nd May 2013, 02:34
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To be clear, I don't know anything about the 777!

But I do know that, in the 737NG if the autothrottle is armed during pre-flight checks, one only has to touch either of the TOGA switches and both engine thrust levers will immediately advance to takeoff power.

Thats why we don't arm the autothrottle until approaching the departure runway!

If the 777 system is anything like the 737 then . . . . . .
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Old 2nd May 2013, 10:54
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I'd imagine the 777 is similar to the 744 you need flaps for the TOGA switches to be armed.
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Old 2nd May 2013, 12:32
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what's the possibility that the event happened on taxi out and that the plane was tugged back to a stand and disconected and nothing happened between a tug and the plane to cause the event?
Zero chance that it happened like that.

Read SMOC posting, the reason is known, the cause isn't.
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Old 3rd May 2013, 18:04
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Nothing a bit of speed tape couldn't sort!!
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Old 4th May 2013, 13:10
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A simple explanation might be an attempt to taxi with the tug still attached. Has happened a fair few times in the history of aviation and probably will in the future too. ATC clearance received, headset disconnected, bit of distraction, easy to do...

Even a big tug would be no match for two 115Bs.
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