Blue ice in the context of aviation is the frozen material formed by leaks in commercial aircraft lavatory waste tanks, a biowaste mixture of human waste and liquid disinfectant that freezes at high altitude. The name comes from the blue color of the disinfectant. Airlines are not allowed to dump their waste tanks in mid-flight, and pilots have no mechanism by which to do so; however, leaks can occur.
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There were at least 27 documented incidents of blue ice impacts in the United States between 1979 and 2003.[1] These incidents typically happen under airport landing paths as the mass warms sufficiently to detach from the plane during its descent. A rare incident of falling blue ice causing damage to the roof of a home was reported on October 20, 2006 in Chino, California.[2] A similar incident was reported in Leicester, UK, in 2007.[3]
In 1971, a chunk of ice from an aircraft tore a large hole in the roof of the Essex Street Chapel in Kensington, London, and was one trigger for the demolition of the building.[4] In November 2011 a chunk of ice, the size of an orange, broke through the roof of a private house in Ratingen-Hösel, Germany.
Blue ice can also be dangerous to the aircraft itself; the National Transportation Safety Board has recorded three very similar incidents where waste from lavatories caused damage to the leaking aircraft.[5][6][7] All involved Boeing 727s, and in all cases waste from a leaking lavatory hit the number 3 engine, mounted at the rear of the aircraft, causing a power loss[7] or the engine to fall off in flight.[5][6] The flights made safe emergency landings with the two remaining engines. Nobody was injured. Only one report specifically mentions ice,[6] while another mentions "soft body FOD",[7] indicating that in this case the "blue fluid" was not frozen.
Blue ice became known to many people from the last 2003 episode of the HBO series Six Feet Under, in which a foot-sized chunk drops on an innocent bystander. It was also mentioned in the US sitcom The Big Bang Theory season 2. This also happened in an episode of CSI: NY. The title of the 1992 film Blue Ice is a reference to the phenomenon.[8] The 2001 film Joe Dirt finds the title character (played by David Spade) proudly displaying a large chunk of 'blue ice' which he has mistaken for a meteorite, and the topic has also been covered on the TV show MANswers. Blue ice was also featured in an episode of the television show "Mythbusters".
In John Waters's film A Dirty Shame, David Hasselhoff, playing himself, goes to the bathroom in an airplane and his waste is flushed out of the airplane and hits one of the main characters in the head.