Does airplanes dumped fuel when landing?

If you mean do they let the fuel fall out of the plane then no, because that could cause a giant mess or fire. LOL Yes, they do. In cases of Emergency and the aircraft has to land immediately after take-off, then the aircraft has to dump fuel in order for it to get its weight below the Maximum Landing Weight. This usually only applies to large passenger air liners. Large military aircraft can also dump fuel. If the aircraft lands at too heavy weight then the gear may break or it will not have enough braking energy to stop the aircraft and it will run off the end of the runway---unless the airport has plenty of runway length. An emergency that would require fuel dump would be if the engine quite. Remember the airplane that landed in the Hudson River in New York. It lost both engines due to a bird strike. If it had been a little higher in altitude, the crew would probably have started the emergency fuel dump procedure. Another reason to dump fuel is that if the aircraft has a serious problem with landing gear or failed structure and it is expected to crash on to the runway, then it is safer if the aircraft has very little fuel in it in order to reduce the threat of post-accident fires. Will it create a mess? The experts say it will not. Fuel dumped into the atmosphere at high altitudes will dissapate as vapor. It would be about the same as pouring a little amount of fuel onto a concrete parking lot and the heat evaporating it into the air.