The plane carries a ton of water (an actual ton: ~2,241 pounds). Presumably that factors into weight and balance.
Originally Posted by
T8191
Indeed … the load and trim calculations for take-off and the rest of the trip. I’m amazed the Captain made the decision to proceed, unless other factors were in play. How long would it take to fill the water tanks?
Originally Posted by
IAN-UK
I'd hope the pilots were aware their weight calculations were awry, and they were well over a tonne light before they left the gate.
I'd be interested to hear from pilots whether a tonne would make any significant difference to the weights/speed/trim calculations.
The self-loading cargo isn't weighed, nor is the cargo that they schlep on board themselves, and the airline uses educated guesswork for this part of the payload. The 787-9 may have about 230 occupants when full. An average 5 kg error per person would be well over a tonne, yet there seems to be no hysteria about this possibility, which is simply just a known unknown.
In addition, does the 787-9 have stuff to help with trim once airborne, like shifting fuel about?
If the aircraft did depart without this being noticed, then it's pretty poor. And once airborne, the crew have to go through the same decision-making process about whether to live with a non-critical problem or to inflict a 24-hour delay on all the passengers as if the system had just broken down (as in other cases). But if it isn't a safety-of-flight issue, let's not go overboard about that.
And if you really want a genuinely toe-curling example of (many) things that should have been checked, but weren't, before the aircraft got airborne, try the ATSB's website for the recent report on 9M-MTK at BNE. If you don't want to be scared, don't read it.