– Why and how does a plane dump fuel in emergency landing situations?

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I understand that they need to be a lighter weight to land. How does the process of dumping fuel while airborne work?

Edit: sorry my question was worded horribly. What happens with the fuel if it is dumped while airborne. If a plane is flying over a city and needs to dump fuel how does that work?

In: Engineering

Opening the tank and letting it relase in the air.. it’s also to cutdown on the fire risk.. if your crash landing your tanks should be basically empty..

As you say, planes have maximum landing weights. Heavier than that, the risk of damage to the undercarriage is too high, and they might not be able to stop in time.

As for how – they have dedicated valves that can be controlled from the cockpit, and nozzles that deposit the fuel safely away from the engines. There’s examples of it in the Wikipedia article on [Fuel dumping](https://en.wikipedia.org/wiki/Fuel_dumping)

Crashing into the ground with a large amount of flammable liquid on-board is fairly dangerous so disposing of it makes a force landing safer.

Air planes have a maximum landing weight that’s less than the take off weight. The assumption is that when you land you’ll have burnt off the fuel and be the appropriate weight.

Sometimes you’re not, like if you take off, realize there is an issue and need to turn around and land back at the same airport. You’ll open a port, usually on the wings and spray fuel into the air. It gets misted because of the speed.

As a sidenote to your question, it’s worth noting that if the plane is still airworthy, then generally, they’ll fly a holding pattern until the fuel load is reduced, rather than dumping.