These black plumes are primarily soot from partially burned fuel, and are distinct from contrails. For older engine designs in particular, to keep the internal engine components cool during takeoff and climb, excess fuel is used during the takeoff phase of flight, leading to an overly rich fuel mixture. This rich fuel mixture does not burn as completely or efficiently, resulting in soot forming in the exhaust plume. This soot phenomenon is similar to that seen coming from large tractor trailer trucks. Engine manufacturers optimize the internal components of engines for the high airspeeds, low ambient temperatures and low air densities aircraft encounter during cruise flight. Older turbofan engines and turbojet aircraft are particularly susceptible to this kind of soot production. Classic examples of this type of engine behavior are the B-52 bomber and MD-80 airliner.

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拍攝者： Mccrainemercantile