Again you make the point, and so succinctly :)

When under pressure (and maybe feeling a little bit flushed, eh Positivegee?) it is so easy to type something that looks ok into a keyboard, only for it to come back and bite you later. And the more common the task the greater the difficulty in spotting the error.

Consider for example the effect of 'pattern interrupt' (google it) upon your pre-flight programming. You've got the preliminary via datalink, you're reading out the numbers and the other chap/ess is punching in the figures, you cross check but during those vital moments yet another person comes in with a query. Missing pax/bags/tug/odd question etc etc. It's actually the 'odd question' that might be your undoing - the rest you're used to fielding on a daily basis. Both your minds do a subtle 'eh?' and the interrupt is complete. Not saying that's what happened, just that it can.

Whatever the mistake, to err is human. You're right that on these forums (fora if you'd prefer the Latin) it doesn't matter very much. But it does help to illustrate the point.

Oh, I think if you use your preferred 'nautical miles per minute.. instead of knots' it will be over quicker than you think ;)

Dear Obie, in my entire career of 33 years as a flight engineer, one of my duties was to calculate and fill in the data cards for all phases of the flight. Cross checked before setting the bugs, we never had an incident or accident due to incorrect data input. Have you ever flown with a flight engineer? Maybe it's time they re-instated them.:ok:

Reinstate the F/E
 

HotDog. I'm on your team mate. I have made the same point on previous posts. Quite apart from the other contributions made by us, the distribution of pre-flight work load including the F/E extracting the performance data for independent checking by the non-handling pilot is very beneficial. The responsibility for the correct fuel uplift into the appropriate tanks resting with the F/E, who is/was going flying, was another benefit as was the thorough check on the walk-around pre-flight inspection and such niceties as initialising INS's and cockpit checks etc etc. They won't put us back mate, our in-flight rations and the return to a heavier, more comprehensive, MEL is too big a weight penalty. Besides that, the jargon used these days is too much like text messaging for us old buggers to familiarise ourselves with. Maybe we should just let comments like those from Obie "slip through to the 'keeper"

'Ex Cargo Clown'. That would certainly help, but I'm not sure I would leave it just up to the dispatchers to provide the performance calc's. Besides, our SOP requires independent computation/calculation.

But as another line of defence, sure, I'm all in favour.

Can never see it happening though!

Two near death experiences on takeoff, both 'human factors' related.
Their luck will run out.

Can anyone explain to me why it is not feasible for Airbus to build some sort of gross error check for take-off acceleration into the FMS?

The FMC already has all the required data: Temperature, air pressure, N1, entered or calculated wind component etc. Knowing all this surely it would be a simple matter for the FMC to calculate the expected acceleration for the entered TOW. This could be compared to the INS / ADIRU (or whatever its called on the bus) acceleration, and the pilots alerted to any gross discrepancy.

Or am I missing something?

Woof etc;
You answered the question yourself, with:
GIGO. If the weight(s) are out by a digit, ('2' instead of a '3' in a 375,000kg GTOW), the FMC will rationalize incorrect data as correct. It's already occurred as you know.

Some suggest that the aircraft have a weight/balance system installed using oleo deflection etc - such a system is available (from Airbus, I recall) and, we have read here, was "not reliable".

Also, airlines may not be too keen to have such a system which would be independant of their own load control departments and programs. Keep in mind that most airlines do not weigh baggage and they never weight passengers, just to avoid the inevitable harrassment/embarrassment lawsuits from passengers if nothing else.

So on any one takeoff, an installed aircraft w/b system would rarely agree with the "official" numbers as transmitted to the aircraft by the airline's load control department.

The question would be, how does one rationalize the discrepancies and which figures "trump" the other figures? In an accident investigation, which data is correct? Why?

Also, for those companies that choose to overload their aircraft, such a system would not be installed or, if mandated, would at least be heavily lobbied against. The business of aviation is about "max lift-min cost", first.

As has been pointed out earlier (Radio altimeter thread), how do you resolve differences between only two systems' data? Would a third data calculation provide a sufficiently robust voting system?

Final checklist item: "TOW... ---.-Kgs"
 

The phrase "TOW... ---.-Kgs" could be included as a final item in the "Before Takeoff check list." It would be a last chance gross error check with FMS input and computer flight plan weight. :ooh:

Glueball, what you mention is already part of the Airbus Standard Operation Procedure. It is part of what is called the MINI BRIEFING taking place sometime during the taxi out phase.
In the case of EK407, it did not change anything, for the simple reason, as already mentioned earlier, that FMS and paper flight plan (as provided by dispatch) weights were matching.
Please read here

In this particular case, with the crew being aware that they were at 360T, but the speeds being for a lesser weight, would a placard have helped?

Picture this;
Tower "Emirates 123 hold at holding position x for runway 34"
F/O " Holding short 34 Emirates 123"
F/O to Cpt " This is intersection x, the data was done for intersection x, gross weight 360T Vr checks"
Cpt to F/O " Well done son...before take-off checks please"

When the F/O confirms the intersection he looks at a $15 plaque attached to the a/c by his right knee.

Vr Table

Weight Flap 1 Flap2 Flap 3
360 161 153 148
350 159 150 144
340 157 148 142
330 etc etc etc
320 etc etc etc
etc

The figures would be for 15 degrees no slope but they would be a gross error check and thats all. It could be that as long as they made sense everyone is happy. ie if the Vr in the box is a couple knots faster the crew can put that down to the fact that it is 31 degrees outside.

I would be most receptive to posters telling me why this wouldn't work as I know there are people vastly more experienced than myself on these boards.
If this had been SOP in YMML would they have picked it up?
Regards, Framer
PS I have no idea of flap settings and speeds on this type of a/c so I made them up and just called them flap 1 2 and 3.

PJ2: That's the whole point: If the entered TOW is incorrect then the FMC would be expecting a different acceleration from the ACTUAL acceleration.

ie. For the given parameters (temp, pressure, N1 etc.) from which the thrust may be calculated, the predicted acceleration could be calculated for the entered mass. If the actual acceleration is significantly different then this would be an indication that the input mass is incorrect.

Of course additional factor affect the acceleration: Wind, runway contamination, variations between actual weights and std weights etc. But as a gross error check (in this case a 100 ton discrepancy) the difference between actual acceleration and predicted acceleration based on the weight entered into the FMS would have been significant.

Not quite so simple Framer - the speeds for a particular weight and flap setting may change depending on the segment performance requirements, temp, pressure, wet/dry etc.... It's an Airbus:ok:, not a Cessna...

The whole key is to making sure that the CORRECT DATA IS ENTERED INTO THE LAPTOP.. Cr@p in = cr@p out..

All these great ideas :rolleyes:................. be far simpler to have load cells fitted to the undercarriage, and feed that data in with an allowable tolerance. Then the crew could be alerted if they entered a big porky in by mistake!

J

Something along these lines Jaba.
http://i101.photobucket.com/albums/m...ham227/w-2.jpg
I mentioned onboard weight & balance systems in an earlier post, it seems the Airbus certified system is complex and consuming of maintenance hours so the latter (dollars) would seem why it hasn't gained favour. The 744F has it as a standard fit and I've asked a question on freight dogs if anyone can proffer their experience. Earlier in this thread one gentleman mentions the system they had on the Merchantman as being robust and reliable, surely its not beyond the ken of us all these years later to come up with something to do the job. The Honeywell system advertises +-1% accuracy and certified as a primary or advisory dispatch system on those aircraft for which it is certified (747 & MD-11 thus far). And no transposing of data from laptop to FMS which seems to be where this accident stems from.

CONF iture, Brian Abraham;

Not sure it's been asked - wouldn't the error in entered weights also create an incorrect trip fuel burn and final fuel figure? One would at least notice the larger extra fuel opposite LSK 6L.

Gents - the weights entered into the INIT B page of the FMS were correct. The problem was with the laptop and the speeds are then loaded into the PERF page..

You can upload screenshots of INIT pages all you like but it won't change the fact that the error was the original input into the laptop...

White Knight;

Thanks...I knew there was something I'd missed in this.

Which is why we compare the "green dot" speeds (minimum clean) calculated by the laptop and the FMC on the PERF Page. If they match, laptop and FMC have the same weights. To enter the right weight into the FMC, but 2XX tons instead of 3XX tons into the laptop is by far the most common error. This is recognized by comparing green dot speeds.

Cheers,
DL

Dam! ....Oh well, I had a gut feeling I was gunna end up lookin silly on that post but thought it was worth a shot :)

Would the Vr really change that much though? Like more than 5kts? I understand V1 changing due wet/dry rwy etc etc but I thought Vr would be only effected by slope and temp/pressure. Does the Vr change due to 2nd and 4th climb segment requirements?
Cheers

Didn't they take off on R/W16?...
Do you lot know what you are talking about, or not?
I strongly suspect, not!! :rolleyes::rolleyes::rolleyes: