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Interesting Air France A340 - Bogota Incident

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Interesting Air France A340 - Bogota Incident

Old 20th Jun 2017, 04:52
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The Cooler King
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Interesting Air France A340 - Bogota Incident

Incident: France A343 at Bogota on Mar 11th 2017, abnormally long takeoff run
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Old 20th Jun 2017, 05:01
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Shades of Emirates in Melbourne...
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Old 20th Jun 2017, 07:15
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The BEA reported that the aircraft needed an abnormally long takeoff run.
According to preliminary information the aircraft crossed the runway end at about 5 feet above ground instead of 35 feet AGL.


35' is the requirement after losing thrust on 1 engine, nest ce pas? Is the BEA suggesting they had an engine failure and continued to Paris. The CVR must have been interesting, but then again was it auto erased by Paris?
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Old 20th Jun 2017, 07:54
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The BFU (?) jumped in...., French plane in Colombia....

On Jun 19th 2017 Germany's BFU reported in their March Bulletin that the BFU joined the investigation on request by the BEA. During the takeoff run a retarded rotation occurred which caused the aircraft to remain below required safety heights.
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Old 20th Jun 2017, 07:55
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Hello RAT5

Indeed. Numerous questions being bounced around the office this morning when we read this.
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Old 20th Jun 2017, 10:09
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35' is for twin engine aircraft
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Old 20th Jun 2017, 10:31
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No, it is NOT. It is valid for 2, 3, 4 and 6-engined aircraft. All deemed to have 1 engine INOP.
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Old 20th Jun 2017, 10:33
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Originally Posted by wtsmg View Post
CBs in the vicinity.

+TS on earlier METARs that I bet was still hanging about embedded in the cells, slowly dissipating.

I wouldn't be surprised if this was the result of a tailwind component developing during the take off roll from those CBs.

Heavy aircraft. High pressure altitude. Convective wx. Terrain. Not nice!
Lol
Actually the explanation is much, much, much simplier than this
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Old 20th Jun 2017, 10:43
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Please tell us, we keep it secret, hush hush....
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Old 20th Jun 2017, 10:58
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Let's just say that if you want your aircraft to take off you're gonna have to put the nose up at some point.
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Old 20th Jun 2017, 11:03
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Sorry, no professional contribution but a simple question of an interested slf/ ppl-holder:
in case something goes wrong during t/o-roll, like enigens donīt produce calculated thrust, thrust calculation itself or powersetiing was wrong, how do pilots realise it before itīs too late?
Are there checks like:
certain speed has to be gained at halfway down the runway or v1 has to be reached at a certain point (down the runway)?
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Old 20th Jun 2017, 11:10
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There is a thing called gross vs net performance.
Gross performance is your performance on that particular day, with the particular temperature, engine performance, pilot skills, etc.. that can all vary
Net performance is considered to be the worst possible performance among a million flights.
It is a requirement that net performance meets the standard (not gross performance)
So basically you have a one in a million chance that your gross performance will not reach the standard (standard = 35ft at the departure end of runway)

How you would be supposed to notice you're not meeting this net performance requirement, I unfortunately don't know.
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Old 20th Jun 2017, 11:20
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it's "take-off thrust set" and then watch engine parameters for anomalies and trust your calculation.

engines not producing takeoff thrust should be shown by the EPR gauge
(https://en.wikipedia.org/wiki/Engine_pressure_ratio ; for modern airliners)

fan rpm is also a good indicator of thrust as you generally notice when a blade is missing

i suppose with modern computers you could introduce monitoring of horizontal acceleration but it seems like it's mostly worked until now
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Old 20th Jun 2017, 11:42
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Ok for thrust but what if residual braking pressure was being applied on some wheels ?
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Old 20th Jun 2017, 12:15
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Are there checks like: certain speed has to be gained at halfway down the runway or v1 has to be reached at a certain point (down the runway)?

There were some runways, perhaps military some years ago, that had 'distance to go' markers. You could monitor your speed passing certain markers and make a rough guesstimation of 'how's it going?' It has been discussed before for modern civil airliners, but it was deemed the RTOW analysis was good enough.

How you would be supposed to notice you're not meeting this net performance requirement, I unfortunately don't know.

One day in Mombasa, B757, very hot. We did all the calls and arrived at a conservative thrust/flap setting. As we trundled down the runway the end seemed to be coming closer very quickly. A manual nudge of the TL's to the stops seemed appropriate. We surged forward and rose skywards; as you do. While this was happening, we crested a gentle hop in the runway ands realised we'd been fooled by a mirage. When there's doubt there is not doubt. Stopping was not a safe option as everything else seemed to be working fine and we had no doubt about the calls: it was just our eyes were being deceived.

Let's just say that if you want your aircraft to take off you're gonna have to put the nose up at some point.

Is A340 one of these clever birds that weighs itself and calculates the trim? If the trim was a little nose heavy PF could have been applying up elevator very gently and been surprised that it wasn't working as expected; then a more muscular pull delayed the lift off point.
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Old 20th Jun 2017, 14:21
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So we are condemned to repeat the same mistakes again and again and again?

On October 14 2004:
http://www.pprune.org/rumours-news/1...+accident+2004

And November 3, 2004, on the wave of emotions caused by that accident:
http://www.pprune.org/1591360-post8.html

and I: http://www.pprune.org/2147179-post620.html

In this case - I don’t know ‘magenta line’ planes -: “Firewall the throttles” was not an option?
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Old 20th Jun 2017, 14:59
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Originally Posted by wtsmg View Post
Given you don't even have a license I'm most interested in your observations, oh wise one!
Well, well, do you believe you need an ATPL license to know that a takeoff requires to pull on the stick and to increase the pitch angle ?

There are professionals other than pilots on this forum.
I know that us youngsters are completely incompetent but this is very basic knowledge.

PM me if you want more details.
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Old 20th Jun 2017, 15:03
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So you are suggesting the stick wasn't pulled?
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Old 20th Jun 2017, 15:24
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Originally Posted by KayPam View Post
Ok for thrust but what if residual braking pressure was being applied on some wheels ?
Any residual brake pressure that would effect the takeoff roll would be very apparent during taxi. In addition you would have a rapidly rising brake temp on taxi out. Not that uncommon on the 330/340. There are also big margins built into all the TO calculations to cover for this type of issue.
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Old 20th Jun 2017, 15:25
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Thanx for all the interesting answers on my question (post #12).
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