Interesting Air France A340 - Bogota Incident
 

Shades of Emirates in Melbourne...

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?

The BFU (?) jumped in...., French plane in Colombia....

Hello RAT5

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

35' is for twin engine aircraft

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

Lol
Actually the explanation is much, much, much simplier than this :ugh:

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

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.

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 don´t produce calculated thrust, thrust calculation itself or powersetiing was wrong, how do pilots realise it before it´s 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)?

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.

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 :)

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.

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

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.

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?

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.

So you are suggesting the stick wasn't pulled?

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.

Thanx for all the interesting answers on my question (post #12).

Wiedehoph

yea, the fan RPM would go up if it was the loss of a fan blade :) (loss of fan flow)

I muss confess that I am a little puzzled that even the most recent offerings don't have some sort of take-off performance vs actual GPS position vs airport config monitoring system. Seems fairly doable with current technologies and could help with various scenario (most obvious being wrong runaway start position and wrong weight used for performance calculations).

Now I understand that each system will bring its own issues in the mix and the certification issues. But would still be worth IMHO.

Thanks

Clearly not a new idea (although I don't see the use of GPS being discussed, nor any compeling argument not to do it).

In terms of UI I can imagine a green / yellow / red gauge displaying the delta between actual performance & position vs expected.

There are reports that the audio has 'pitch, pitch' alerts at about 31 seconds into the takeoff.
How is that even possible during a takeoff?

Kaypam, was it similar to this?

35' for a dry runway, 15' for a wet cert ac on a wet runway.

In regards to obstacles, the OCA is the same, there is not a difference between all engine and EO clearance areas. The area assume a min perf gradient

In the event of an engine failure, continued adherence to departure procedures may not be possible as SIDs or DPs do not necessarily assure that engine-out obstacle clearance requirements are met.
The most common procedure to maximize takeoff weight when significant obstacles are present along the normal departure route is to use an EOSID in the event of an engine failure on takeoff. If the EOSID routing is different from a SID or DP, then the obstacles along this track are used to determine the maximum allowable takeoff weight for that runway. Note that often the path of the EOSID will not overfly the area where the aerodrome operator has provided an obstacle survey.


Net climb min requirements are the same, EO or not. Up to performance guys to make sure EO perf meets the min. OCA. This typically means weight limiting the ac to meet the SID path when OE, because the obstacles have been evaluated along this corridor.

Can be EO, above temp..whatever, the obstacle clearance area is the same for all.

As a note: Some airlines have purchased specific high temp and/or EO procedures that include obstacle analysis based on ac performance, rather than limiting loading based on the criteria min climb or temperatures

Is this type notoriously prone to tailstrike on T/O, so that you "always", deliberately, tend to rotate slower than the Airbus nominal rate?

NO! Same technique.

Lufthansa operates a similar type (A343) to BOG on a regular basis and changed their procedures to better operate out of that station. LH had a tailwind situation in November 2016 there: http://avherald.com/h?article=4a1568b4&opt=1

MTOW
 

If I remember well the maximum takeoff weight of an airliner, must be equal to or less than the maximum structural,
and such that its T.O. run is equal to or shorter than:
- Take-Off Distance;
- Take-Off Run;
- Accelerate-Stop Distance,
AND: WITH ALL ENGINES OPERATING, TAKE OFF DISTANCE PLUS 15%
Regards

This sort of points back to the frame itself, unless the same crew was involved in that event as well.

I'll avoid making "curvature of the earth required for takeoff" comments, because it would be really, really interesting to find out how and why this happened.

This, I guess, could also be a factor, inspite of what METARS reports.

Sudden gust, and all that.

Let the discussion run on!

Difficult to see this being a 'frame' issue.

There should be sufficient data recorded for AF/Airbus to determine what caused the problem(s).

I might be over simplifying things but isn't there a time/speed gradient for weight/power/available runway length settings - this would pick up brakes being on/power settings incorrect.
Admittedly this wouldn't pick up starting at the wrong intersection or incorrect weight being input.

That's anybody's guess. The quote from Avherald:

is somewhat ambiguous, to say the least.

It's not clear whether they are referring to the same airframe (F-GLZU) or merely the same type (A343) and/or whether the "similar occurrence" also happened at Bogota.

If also at BOG, it can't have been the same airframe on the date quoted.

Same airframe, also in BOG.

Thanks - then it must be the date reported by Avherald that's wrong, as F-GLZU was flying the North Atlantic on that day.

That aside, don't attach too much significance to the same tail number being involved on both occasions. It may well just be a coincidence, given that it has operated more than 20 CDG/BOG rotations so far this year.

Having all these gizmos is all very well, but there is no real substitute for a good rule of thumb and a knowledge of the real (actual - not what they tell you) weight of the aircraft. I have very clear recollections of all sorts of unknowns being shoved into the forward hold at BOG and only coming to light because of my insistence. Bring back STAN of the VC9! At least you would then know the real weight.
:ouch:

I've been in a major airline that "routinely" lied about cargo weights. Vancouver photographers knew that this airline would always rotate right at the far end of the runway, providing them with some nice photos. Aircraft would also never make performance altitudes, etc. I believe one crew insisted on all cargo being weighed upon arrival and it was found that there was a massive discrepancy in cargo weights. Lots of bluster from company but they knew what was going on and did nothing about it.

What are the necessary conditions to normally trigger such audio warning ?
Does such warning limit in a way the pitch control ?