Originally Posted by
Mike71
In turbojet/turbofan, weight decrease is significant over time. Small increases in IAS /IMN make a large increase in drag at high altitudes (it is a "quadratic effect" - a 10 KIAS change at 290 KIAS is considerably larger drag increase than a 10 KIAS increase at 170 KIAS). Therefore, jets typically get best fuel/range performance at a constant KIAS/IMN, and is easy to hold using autothrottle. The fussiness of setting jet engine thrust to get a precise airspeed often requires some initial, and continued throttle jockeying to hold target cruise speed..
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