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-   -   Interesting Air France A340 - Bogota Incident (https://www.pprune.org/rumours-news/596079-interesting-air-france-a340-bogota-incident.html)

Farrell 20th Jun 2017 04:52

Interesting Air France A340 - Bogota Incident
 
Incident: France A343 at Bogota on Mar 11th 2017, abnormally long takeoff run

KRviator 20th Jun 2017 05:01

Shades of Emirates in Melbourne...

RAT 5 20th Jun 2017 07:15

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?

gearlever 20th Jun 2017 07:54

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.

Farrell 20th Jun 2017 07:55

Hello RAT5

Indeed. Numerous questions being bounced around the office this morning when we read this.

ironbutt57 20th Jun 2017 10:09

35' is for twin engine aircraft

FOUR REDS 20th Jun 2017 10:31

No, it is NOT. It is valid for 2, 3, 4 and 6-engined aircraft. All deemed to have 1 engine INOP.

KayPam 20th Jun 2017 10:33


Originally Posted by wtsmg (Post 9807191)
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 :ugh:

gearlever 20th Jun 2017 10:43

Please tell us, we keep it secret, hush hush....

KayPam 20th Jun 2017 10:58

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.

sf25 20th Jun 2017 11:03

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)?

KayPam 20th Jun 2017 11:10

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.

wiedehopf 20th Jun 2017 11:20

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 :)

Basil 20th Jun 2017 11:41

sf25,
Re the types I flew until 12 years ago:
Strictly speaking, from a performance perspective, we SHOULD have a marked point on the runway which indicates the stop/go position in the event of an engine failure. ISTR that the British V-bombers used this system but am prepared to be corrected if that was not the case by ex V-force crew or Mad(Flt)Scientist.
Because of the wide variety of types, configurations and reduced thrust calculations in civil aviation the fixed point is not possible so we use a calculated speed, V1, at which, with all engines operating, we SHOULD have reached OUR fixed point on the day. Not perfect but seems to work.

In answer to your question, if we had a dragging brake or thrust was inadvertently too low then the 'fixed point' would be too far down the runway and the stop/go would be compromised.

KayPam 20th Jun 2017 11:42

Ok for thrust but what if residual braking pressure was being applied on some wheels ?

RAT 5 20th Jun 2017 12:15

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.

DOVES 20th Jun 2017 14:21

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?

KayPam 20th Jun 2017 14:59


Originally Posted by wtsmg (Post 9807547)
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.

gearlever 20th Jun 2017 15:03

So you are suggesting the stick wasn't pulled?

Sailvi767 20th Jun 2017 15:24


Originally Posted by KayPam (Post 9807500)
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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