AF 777 wrong weight inputs, off by 100 tonnes?
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Those comments are a bit silly; surely it's worth examining -and perhaps redesigning the tools given to pilots so that a very minor mistake isn't catastrophic? What about an electronic version of the old paper tables? The issue with the current accountancy-based programmes is they give no visibility of the effect of inputs or how close to the limit you are; empty sector or 1kg below MTOM it's either green numbers OK or Amber if over.
Last edited by ShotOne; 16th Jun 2015 at 16:11.
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surely it's worth examining -and perhaps resigning the tools given to pilots so that a very minor mistake isn't catastrophic?
Surely it's already done? There is a flight plan with the ETOW base on pax figures and cargo. Then comes the load sheet ands the FMC loading. There should be a gross error X-check. There are the tools.
Surely it's already done? There is a flight plan with the ETOW base on pax figures and cargo. Then comes the load sheet ands the FMC loading. There should be a gross error X-check. There are the tools.
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No it's not. The flight plan weight is an estimate/guess made at the point the plan is produced. It's never identical and can be quite significantly different to what you depart with. In any case as I pointed out earlier, weight is just one of many factors which could make nonsense of the performance calculation.
I doubt any of these incidents have happened when the figures were calculated independently by each crew member. i don't think hardware or software is the problem or that changing either will solve the problem. The problem lies with the Human and can easily be mitigated by the Human.
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It is just like any other facet of aviation: Any human might make an error at any time. Through hard lessons, we have developed procedures and crosschecks to minimize the probability that a single error will be catastrophic. However, we must follow those procedures and perform those crosschecks to continue the chain.
While the Dispatch Release may not have an accurate final weight, it is unlikely to have a 100 Tonne or 100,000 lb discrepancy. Safety margins will likely render 10-Tonne errors harmless, and procedures such as dialing in a preliminary V2 into the MCP based on the flight plan weight should alert to a large error.
While the Dispatch Release may not have an accurate final weight, it is unlikely to have a 100 Tonne or 100,000 lb discrepancy. Safety margins will likely render 10-Tonne errors harmless, and procedures such as dialing in a preliminary V2 into the MCP based on the flight plan weight should alert to a large error.
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Preliminary V2? So you're advocating another entirely separate performance calculation based on the estimated take off weight? That figure, remember is a guess made several hours before departure. Aside from making a period of high workload even higher, what would that achieve? And why do all these helpful suggestions relate only to weight but none of the other inputs critical to correct figures?
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Setting the preliminary V2 has been a procedure in my airline for 15+ years. You don't have to do a complete performance calculation to get it -- looking at the Vref chart for the proposed takeoff weight is sufficient, or enter the takeoff weight into the Approach page. Can be done in 10-15 seconds. With a TLR (preliminary performance report attached to the dispatch release), just read the V2 off the sheet for less time spent. So don't make rash assumptions about what I am advocating.
And yes, many of the other "inputs critical to correct figures" are made prior to knowledge of the final figures, to include PROPOSED runways, departure, route, altitudes, and arrival. There are procedures and crosschecks for all. You don't wait for your final oceanic clearance before putting the route into the FMS; and when you do get the clearance you crosscheck with your filed route. Same with PROPOSED altitudes and winds to generate a fuel burn schedule...
Finally, we require an entirely new dispatch release if the actual ZFW is more than 10 Tonnes above the original. As I indicated earlier, a 10-Tonne error (in a 747) is survivable due to safety margins if an error is carried forward.
And yes, many of the other "inputs critical to correct figures" are made prior to knowledge of the final figures, to include PROPOSED runways, departure, route, altitudes, and arrival. There are procedures and crosschecks for all. You don't wait for your final oceanic clearance before putting the route into the FMS; and when you do get the clearance you crosscheck with your filed route. Same with PROPOSED altitudes and winds to generate a fuel burn schedule...
Finally, we require an entirely new dispatch release if the actual ZFW is more than 10 Tonnes above the original. As I indicated earlier, a 10-Tonne error (in a 747) is survivable due to safety margins if an error is carried forward.
Last edited by Intruder; 17th Jun 2015 at 12:51.
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Whoa, you've rolled in a whole load of issues there, intruder and even though I agree with quite a lot of what you say it doesn't necessarily bear on the topic. It sounds like your airline has a robust set of procedures. Good. Also an entirely different set of tools to what AF (or I) had available. You referred to V ref chart?? In most airlines using laptop computer performance it is designed as a stand-alone device not used in conjunction with any chart. Presumably you have a set of charts covering all your destinations? With stand alone computer performance there is no "quick check" like you describe. Either complete a full calculation with a parameter in every box or don't do anything.
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Surely you have SOME kind of reference charts in your QRH and/or FCOM! If your computer fails airborne, are you unable to land?
I have done manual performance charts, standalone performance computers, and ACARS-downloaded performance in the 747 Classic and 744/748. In all cases there are/were backups available. Using a standalone computer is NOT an excuse for a failure to have a crosscheck process in place.
You mentioned earlier "an electronic version of the old paper tables". If you have an FMS, you have one. Enter your Flight Plan takeoff weight into the Approach Reference page, and it will give you a Vref for that weight. For the 744, Vref for Flaps25 is within a couple knots of V2 for Flaps10, and Vref for Flaps30 is within a couple knots of V2 for Flaps20. If the V2 from your computer comes up with a lower number, find out WHY! You can certainly come up with a similar crosscheck for your airplane.
You are supposed to be a professional pilot. While you follow standard procedures, you neither follow them blindly, nor become so procedure-bound that you do not understand what the procedures are supposed to accomplish and/or are unable to perform critical crosschecks.
I have done manual performance charts, standalone performance computers, and ACARS-downloaded performance in the 747 Classic and 744/748. In all cases there are/were backups available. Using a standalone computer is NOT an excuse for a failure to have a crosscheck process in place.
You mentioned earlier "an electronic version of the old paper tables". If you have an FMS, you have one. Enter your Flight Plan takeoff weight into the Approach Reference page, and it will give you a Vref for that weight. For the 744, Vref for Flaps25 is within a couple knots of V2 for Flaps10, and Vref for Flaps30 is within a couple knots of V2 for Flaps20. If the V2 from your computer comes up with a lower number, find out WHY! You can certainly come up with a similar crosscheck for your airplane.
You are supposed to be a professional pilot. While you follow standard procedures, you neither follow them blindly, nor become so procedure-bound that you do not understand what the procedures are supposed to accomplish and/or are unable to perform critical crosschecks.
You are supposed to be a professional pilot.
What it means for everyone who is interested in the actual topic is that the thread goes off rails as two people start bickering and develops a toxic feel.
As for entering in the flight plan take-off weight in the FMS as a cross check. My company would frown upon that. I'm not saying it's a bad idea, just saying that what seems like a good idea to some is not seen in the same way by others. At our Airline the effort is put into ensuring that the two calculations are done 100% independently in a sterile environment. When we started doing it a month after EK407 I was surprised at how often one of us would have a different assumed temperature and we would go back to the drawing board. As a pilot group we have become better at it over the years because nobody wants to be the guy with the wrong figures .
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As for entering in the flight plan take-off weight in the FMS as a cross check. My company would frown upon that.
In the Approach Reference page, the weight entry is temporary - it is erased as soon as you leave the page. Once the ZFW is entered into the Init Ref page, the Approach Ref page defaults to the current gross weight, but that can be temporarily changed to any value without affecting anything else in the FMS. The Vref values are directly calculated from that entry, though, and can then be entered into the FMS or simply referenced for purposes other than approach planning.
When we first got the 744, that method of crosscheck [of our paper performance charts] was also 'frowned upon', but as people started understanding the airplane (and we started moving away from paper performance charts 10 years later), it became an 'official' means of crosscheck.
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So in summary, your check of take-off speed and config relies on calculating an APPROACH speed for a different flap setting?? Is that a manufacturer approved process? It certainly isn't for any type I've operated. Allowing for your not especially polite manner, I'm pleased if this works for your type but even if some clever person were to work out similar rules-of-thumb for other types (in my case, A320/1/330) it would offer no protection against, for instance, even a fatally inappropriate flex.
Last edited by ShotOne; 19th Jun 2015 at 08:13.
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A couple of questions from SLF...
1) What's the rationale for using less than 100% power at take off? Other than cost, is there something else? Like you're more likely to have engine failure, or the performance characteristics make it more difficult to fly?
2) Given the plane knows the start and end destination in its avionics, couldn't it at least alert a weight that would seem way out of the norms when input?
3) Given the avionics know runway length, pre-set power, and V1 couldn't the avionics suggest an abort of takeoff if the performance characteristics seemed significantly out of bounds?
1) What's the rationale for using less than 100% power at take off? Other than cost, is there something else? Like you're more likely to have engine failure, or the performance characteristics make it more difficult to fly?
2) Given the plane knows the start and end destination in its avionics, couldn't it at least alert a weight that would seem way out of the norms when input?
3) Given the avionics know runway length, pre-set power, and V1 couldn't the avionics suggest an abort of takeoff if the performance characteristics seemed significantly out of bounds?
Checking Vref is a valid way of ensuring that the weight in your Performance Tool is the same weight that the FMC is using.
Not to my knowledge. It all comes down to cost. It actually burns more fuel to take off at less than full thrust, but the savings related to engine wear outweigh this. It is totally up to the pilots to decide when to use full thrust. An example might be when there is a gusty cross wind or windshear reported.
More often than not the weight in the FMC is correct, it is the weight in the laptop or IPad that is incorrect and not in any way integrated with the aircraft so no warning is possible.
FMC may not know the runway length, does not know pre-set power, and does not know V1. These are entered by the pilots after doing calculations on an iPad or a laptop or manually from a book.
1) What's the rationale for using less than 100% power at take off? Other than cost, is there something else?
2) Given the plane knows the start and end destination in its avionics, couldn't it at least alert a weight that would seem way out of the norms when input?
3) Given the avionics know runway length, pre-set power, and V1 couldn't the avionics suggest an abort of takeoff if the performance characteristics seemed significantly out of bounds?
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3) Given the avionics know runway length, pre-set power, and V1 couldn't the avionics suggest an abort of takeoff if the performance characteristics seemed significantly out of bounds?
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it would offer no protection against, for instance, even a fatally inappropriate flex.
Once again, you are supposed to be a professional pilot. Your knowledge of the airplane, its capabilities, and the environment should be a key factor in assessing whether any calculated thrust reduction is sane for the circumstances. Blind acceptance of automated tools is not good for your health.
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"The FMS is not a complete take-off performance computer" Agreed. And that's an understatement. And if Mr Boeings product liability department saw it touted as such they'd have kittens. That's not to say it can't offer a useful cross-check against SOME parameters; but it's not something which was in the toolbox of the subject AF crew, -or any type I operate and hardly justifies your spiky jibes.
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Its really quite simple:
S L O W D O W N !
We are paid by the hour, (well, most of us are).
Speed does not make you a good pilot.
Very little in this profession needs to be done in haste.
S L O W D O W N !
We are paid by the hour, (well, most of us are).
Speed does not make you a good pilot.
Very little in this profession needs to be done in haste.
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This one was Corsair...
Location: Paris, France
History of the flight:
On 10 December 2006, a Boeing 747-400 aircraft, registered F-HLOV, was being prepared for a scheduled passenger service from Paris-Orly airport, with 15 crew and 563 passengers onboard. On arrival at the aircraft, the crew found that the battery of one of the two BLT’s used to calculate the take-off performance parameters was flat; consequently, the second BLT (operating on battery power) was used.
During the pre-flight preparations, the first officer noted a fault message relating to the hydraulic circuit. Discussions with the ground mechanic determined that the issue was being dealt with.
When determining the take-off performance parameters for the flight, the captain provided the first officer with the ZFW from the weight and balance sheet, which he increased by 1.6 tonnes, and the TOW. The first officer then entered the ZFW into the FMS. The TOW was entered into the BLT and the take-off performance parameters calculated. The first officer handed the BLT to the captain to crosscheck the calculations. The BLT then went into standby and the captain handed it back to the first officer who unintentionally turned it off, thus erasing the entered data. At the same time, the captain was dealing with the hydraulic failure issue with the mechanic in the cockpit.
When the new data was being entered into the BLT, the captain inadvertently called out the ZFW instead of the TOW. A weight of 242,300 kg was entered into the BLT instead of 341,300 kg. The captain entered the resultant BLT data into the FMS, replacing the values automatically calculated by the FMS. The first officer then verified that the BLT and FMS values were identical.
The captain entered the assumed take-off temperature into the FMS and queried the reduced thrust value with the first officer. The first officer justified these figures by the fact that the QNH was high and the temperature was low.
The crew performed a rolling takeoff and did not detect that the aircraft’s acceleration was lower than normal. At the V1 speed, the crew noted that there was a reasonable amount of runway length still available and they began to doubt the V speeds. The captain (the pilot not flying) elected to delay the aircraft’s rotation.
When the first officer began the rotation, he immediately noticed that aircraft appeared heavy. The aircraft’s pitch was increased slowly, but the stick-shaker activated. The first officer responded by reducing the aircraft’s nose-up attitude and applying full take-off power. Ground personnel noticed smoke during the aircraft’s rotation.
After the takeoff, the crew suspected a problem with the calculated V speeds and increased the retraction speeds for control surfaces by 20 kts.
Contributing factors
The following factors were identified throughout the subsequent investigation:
•The ZFW was inadvertently read aloud and subsequently entered into the BLT instead of the TOW, resulting in V speeds that were too low
Take-off performance data
Data BLT calculation FMS calculation
TOW 242,300 kg 341,300 kg
V1 120 kts 147 kts
VR 127 kts 159 kts
V2 140 kts 169 kts
• The BLT was not connected to the aircraft’s power source and it went into standby mode.
• The captain was dealing with a hydraulic failure at the time the take-off performance calculations were being calculated.
• After the data had been entered into the FMS, there was no requirement for a comparison to be made with the TOW and the flight limitations.
• There was no requirement to compare the data entered into the BLT with the data entered into the FMS.
Location: Paris, France
History of the flight:
On 10 December 2006, a Boeing 747-400 aircraft, registered F-HLOV, was being prepared for a scheduled passenger service from Paris-Orly airport, with 15 crew and 563 passengers onboard. On arrival at the aircraft, the crew found that the battery of one of the two BLT’s used to calculate the take-off performance parameters was flat; consequently, the second BLT (operating on battery power) was used.
During the pre-flight preparations, the first officer noted a fault message relating to the hydraulic circuit. Discussions with the ground mechanic determined that the issue was being dealt with.
When determining the take-off performance parameters for the flight, the captain provided the first officer with the ZFW from the weight and balance sheet, which he increased by 1.6 tonnes, and the TOW. The first officer then entered the ZFW into the FMS. The TOW was entered into the BLT and the take-off performance parameters calculated. The first officer handed the BLT to the captain to crosscheck the calculations. The BLT then went into standby and the captain handed it back to the first officer who unintentionally turned it off, thus erasing the entered data. At the same time, the captain was dealing with the hydraulic failure issue with the mechanic in the cockpit.
When the new data was being entered into the BLT, the captain inadvertently called out the ZFW instead of the TOW. A weight of 242,300 kg was entered into the BLT instead of 341,300 kg. The captain entered the resultant BLT data into the FMS, replacing the values automatically calculated by the FMS. The first officer then verified that the BLT and FMS values were identical.
The captain entered the assumed take-off temperature into the FMS and queried the reduced thrust value with the first officer. The first officer justified these figures by the fact that the QNH was high and the temperature was low.
The crew performed a rolling takeoff and did not detect that the aircraft’s acceleration was lower than normal. At the V1 speed, the crew noted that there was a reasonable amount of runway length still available and they began to doubt the V speeds. The captain (the pilot not flying) elected to delay the aircraft’s rotation.
When the first officer began the rotation, he immediately noticed that aircraft appeared heavy. The aircraft’s pitch was increased slowly, but the stick-shaker activated. The first officer responded by reducing the aircraft’s nose-up attitude and applying full take-off power. Ground personnel noticed smoke during the aircraft’s rotation.
After the takeoff, the crew suspected a problem with the calculated V speeds and increased the retraction speeds for control surfaces by 20 kts.
Contributing factors
The following factors were identified throughout the subsequent investigation:
•The ZFW was inadvertently read aloud and subsequently entered into the BLT instead of the TOW, resulting in V speeds that were too low
Take-off performance data
Data BLT calculation FMS calculation
TOW 242,300 kg 341,300 kg
V1 120 kts 147 kts
VR 127 kts 159 kts
V2 140 kts 169 kts
• The BLT was not connected to the aircraft’s power source and it went into standby mode.
• The captain was dealing with a hydraulic failure at the time the take-off performance calculations were being calculated.
• After the data had been entered into the FMS, there was no requirement for a comparison to be made with the TOW and the flight limitations.
• There was no requirement to compare the data entered into the BLT with the data entered into the FMS.
Last edited by JammedStab; 21st Jun 2015 at 16:56.