An overweight landing with an engine inoperative or a system failure may be less desirable than landing below maximum landing weight.
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Obviously, landing at weights above the maximum design landing weight reduces the normal performance margins. In the preamble to Amendment 25-18 to FAR Part 25, relative to fuel jettison, the FAA stated, “There has been no adverse service experience with airplanes certificated under Part 25 involved in overweight landings.” Furthermore, service experience indicates that damage due to overweight landing is extremely rare. Landing overweight and fuel jettisoning are both considered safe procedures: There are no accidents on record attributed to either cause. Other models such as the DC-9, 717, 737, 757, and MD-80/90 do not require, or do not have, a fuel jettison system based on compliance with FAR Part 25.119 and 25.121(d). Some models, such as the 777 and some 767 airplanes have a fuel jettison system installed, but it is not required by FAR. To comply with FAR 24.1001, the 747 and MD-11, for example, require a fuel jettison system.
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Federal Aviation Regulation (FAR) 25.1519 - Requires the maximum landing weight to be an operating limitation.The primary Federal Aviation Administration (FAA) regulations involved in landing overweight and fuel jettison are: