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Struggling to work out the impact - no damage, and no injuries, and safe operation of the aircraft wasn't caused. Surprised this classifies as a serious incide

Struggling to work out the impact - no damage, and no injuries, and safe operation of the aircraft wasn't caused. Surprised this classifies as a serious incident.

tyingq 6y ago
Flawed weight and balance procedure, so a "nothing bad happened" situation, but "something bad could have happened". So serious in the sense that changes needed to be made to avoid a real issue in the future.
midasuni 6y ago
I’m surprised that estimated weight is used at all - surely the plane knows the actual takeoff weight, wouldn’t that be the number that’s checked before taxiing starts? Same with actual weight distribution
- jjk166 6y ago
  How would the plane know it's weight? You could measure the forces on the landing gear, but that would be subject to huge errors (inflation of the tires, stresses from the hydraulics, etc.), much higher than the 1% error required to notice this discrepancy. They do have checks in place, which is how they noticed the issue, but it still comes from keeping track of what goes on the plane. > As part of the prestart procedure, the flight crew reviewed the flight plan, which gave an expected takeoff weight (TOW) of 66,495 kg (Figure 1), and the load sheet, which gave a TOW of 64,889 kg (Figure 2). They noticed that there was a discrepancy, with the load sheet showing 1,606 kg less than the flight plan. They noted that the number of children shown on the load sheet was higher than expected, at 65, compared to the 29 which were expected on the flight plan. The commander recalled thinking that the number was high but plausible; he had experienced changing loads on the run-up to the temporary grounding as passengers cancelled and altered trips at short notice.
  - midasuni 6y ago
    I guessed the force on the landing gear would be able to be measured - Pressure in suspension perhaps.
- pwg 6y ago
  The ground crew needs a good enough weight estimate to determine the proper fuel to add to the tanks, and to plan out the cargo distribution in the cargo hold so they can overlap that work (loading fuel, loading cargo) with the actual passenger boarding of the plane to save wait time for both passengers and the airline.
pwg 6y ago
My understanding is that the amount of fuel loaded onboard the plane for takeoff by the ground crew is determined in part by this estimated weight figure. If the weight estimate is too low, then it would be possible for the ground crew to load too little fuel, leading to a situation at the destination of nearly or actually running out of fuel. So it may have been labeled "serious" due to the possibility of not loading enough fuel if the weight estimates are too low by too much.
sidlls 6y ago
This comment is so very HN.
tialaramex 6y ago
Serious incident is the grade below accident, because nothing bad actually happened, but in other circumstances it might have. For example if the aeroplane had been on a relatively short runway, and its passengers consisted entirely of overweight women who were miss-classified as much lighter children, perhaps it would have struggled to clear the runway at calculated power. Flight crews are not trained to attempt to overrule the computer by explicitly commanding maximum thrust because humans are bad at figuring out if they're accelerating as much as expected - and so in the absence of a check that the plane is performing as anticipated † they are going to have a bad time if the calculations are badly enough wrong. Why not just always use maximum thrust? Well if you're an aircraft carrier, or maybe even a military base you could definitely do that, but if you're a civilian airfield then the tremendous noise from jet engines at maximum performance is a constant problem and so you want jets to calculate a lower take off power that's still safe in order to reduce noise. † [in some newer Airbus configurations the plane can work out its real acceleration and which runway you're on and conclude whether it will not successfully take off before it runs out of runway and so caution the pilots to abort before V1 when it's still practical - it doesn't matter why it isn't accelerating what matters is that you won't fly if you don't go fast enough, they can spend as long as they like to troubleshoot when they have stopped]

Struggling to work out the impact - no damage, and no injuries, and safe operation of the aircraft wasn't caused. Surprised this classifies as a serious incident.

tyingq 6y ago

Flawed weight and balance procedure, so a "nothing bad happened" situation, but "something bad could have happened". So serious in the sense that changes needed to be made to avoid a real issue in the future.

midasuni 6y ago

I’m surprised that estimated weight is used at all - surely the plane knows the actual takeoff weight, wouldn’t that be the number that’s checked before taxiing starts? Same with actual weight distribution

jjk166 6y ago
How would the plane know it's weight? You could measure the forces on the landing gear, but that would be subject to huge errors (inflation of the tires, stresses from the hydraulics, etc.), much higher than the 1% error required to notice this discrepancy. They do have checks in place, which is how they noticed the issue, but it still comes from keeping track of what goes on the plane. > As part of the prestart procedure, the flight crew reviewed the flight plan, which gave an expected takeoff weight (TOW) of 66,495 kg (Figure 1), and the load sheet, which gave a TOW of 64,889 kg (Figure 2). They noticed that there was a discrepancy, with the load sheet showing 1,606 kg less than the flight plan. They noted that the number of children shown on the load sheet was higher than expected, at 65, compared to the 29 which were expected on the flight plan. The commander recalled thinking that the number was high but plausible; he had experienced changing loads on the run-up to the temporary grounding as passengers cancelled and altered trips at short notice.
- midasuni 6y ago
  I guessed the force on the landing gear would be able to be measured - Pressure in suspension perhaps.
pwg 6y ago
The ground crew needs a good enough weight estimate to determine the proper fuel to add to the tanks, and to plan out the cargo distribution in the cargo hold so they can overlap that work (loading fuel, loading cargo) with the actual passenger boarding of the plane to save wait time for both passengers and the airline.

pwg 6y ago

My understanding is that the amount of fuel loaded onboard the plane for takeoff by the ground crew is determined in part by this estimated weight figure. If the weight estimate is too low, then it would be possible for the ground crew to load too little fuel, leading to a situation at the destination of nearly or actually running out of fuel. So it may have been labeled "serious" due to the possibility of not loading enough fuel if the weight estimates are too low by too much.

sidlls 6y ago

This comment is so very HN.

tialaramex 6y ago

Serious incident is the grade below accident, because nothing bad actually happened, but in other circumstances it might have. For example if the aeroplane had been on a relatively short runway, and its passengers consisted entirely of overweight women who were miss-classified as much lighter children, perhaps it would have struggled to clear the runway at calculated power. Flight crews are not trained to attempt to overrule the computer by explicitly commanding maximum thrust because humans are bad at figuring out if they're accelerating as much as expected - and so in the absence of a check that the plane is performing as anticipated † they are going to have a bad time if the calculations are badly enough wrong. Why not just always use maximum thrust? Well if you're an aircraft carrier, or maybe even a military base you could definitely do that, but if you're a civilian airfield then the tremendous noise from jet engines at maximum performance is a constant problem and so you want jets to calculate a lower take off power that's still safe in order to reduce noise. † [in some newer Airbus configurations the plane can work out its real acceleration and which runway you're on and conclude whether it will not successfully take off before it runs out of runway and so caution the pilots to abort before V1 when it's still practical - it doesn't matter why it isn't accelerating what matters is that you won't fly if you don't go fast enough, they can spend as long as they like to troubleshoot when they have stopped]