Originally Posted by
Albief15
... watching the MD-11 skim along 50 feet high and 20 feet low crossing the country during IOE, I asked PB, my LCA, "why do it DO that...?" He explained that an attitude is really just a pressure wave...a wave of equal pressure. The jet was smart enough to not waste energy going up and down to chase a barometer setting but instead used GPS/IRU data to "dampen" the flight path to be more efficient as long as it stayed in tolerances. That was an example of some data that made go "humph. That's pretty cool..." Never got that in class...he was probably a Long Beach product like some of you guys alluded to...
The MD-11 did that before we had GPS.
Instead of chasing small airspeed changes with constant throttle movements, the MD-11 will maintain speed (tiny adjustments) with pitch (even though the FMA says THRUST). Once it reaches an altitude "tolerance", it will adjust the throttles, but if it can maintain the speed with constant thrust and a little up and down, it will.
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