The Air Navigation (Aeroplane and Aeroplane Engine Emission of Unburned Hydrocarbons) Order 1988
The Order applies to subsonic and supersonic aeroplanes, wherever registered, which are propelled by turbojet or turbofan engines manufactured after 1st January 1989 and which in the case of subsonic aeroplanes are powered by such engines which have a rated output greater than 26.7 kN. It prohibits such aeroplanes from landing or taking-off in the United Kingdom unless their engines are of a type which has been certified as complying with the requirements for the emission of unburned hydrocarbons (article 4).