Currently on the tarmac waiting for my flights to tax out from the gate. The stewards have called out three times “while this flight is not full, please stay in the seat allocated on your boarding card to make sure we have the right weight distribution during takeoff”. Can really one or two passengers moving change the weight distribution on a 50 000 kg airplane (250M 🦅-units) enough to have an impact?
Or is this just BS? As a frequent traveler I hear this argument a lot..
In: Engineering
I don’t think it’s the worry of one moving but travelers will congregate and suddenly you have 20 moving, not one. That’s why they don’t tackle the one old dude that has to pee but they berate the second.
I mean, 10 people could easily be 1,000kg. Add the lever effect and 10 people moving from say the back to the front could have a reasonable effect on the handling. Maybe it would still be safe, but you don’t want to take any risks.
At takeoff, the plane is at maximum weight for the trip. The fuel tanks are full and they have to worry about front/back weight balance as well as side to side. Later, the plane has burned off a lot of fuel. (It burns about 7,000 pounds an hour.) so it is lighter and they can adjust balance by choosing which tanks to pull from.
They also want you to turn off your cell phone. The cell phone doesn’t affect the flight at all. They think it might. But it doesn’t. Ask around. Tons of people either ignore the warning and keep it on, or forget to turn it off. There are no accidents due to cell phones.
Because takeoff calculations are based on the center of gravity of the aircraft. There’s is an aft and forward limit that could be exceeded depending on how the plane is loaded which can cause problems for takeoff. This limit takes into account fuel, passenger weight, cargo and where it is loaded, baggage, and the takeoff configuration.
I know it’s not exactly ELI5, but it boils down to these calculations which are done after the pilots know the final weight distribution so if things change after the fact it can lead to unexpected takeoff behavior.
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