Originally Posted by
DaviddesJ
In this case we were primarily taking about decreasing thrust, not increasing thrust. But there's not a huge difference.
What you *feel* is the acceleration of the plane (which is determined by thrust), not the velocity. So if the engines are generating a certain level of thrust, then you will *feel* that immediately if you're sitting in the plane.
In terms of acceleration and what is perceived by passenger or pilot you're missing several very important terms here. Namely drag, lift, and gravity. Longitudinal acceleration during a flight can routinely be zero even with the engines generating relatively high levels of thrust if the drag on the aircraft is high.
Acceleration of an aircraft IS related to velocity because drag is related to airspeed. Drag is related to the configuration of the wing (flaps and slats deployed vs. retracted, etc.), airspeed, and angle of attack of the wing moving through the air.
Lift generated by the wing of an aircraft is also related to configuration of the wing, airspeed, and angle of attack.
The force of gravity depends on the mass of the aircraft at that moment (which does change as the aircraft burns off fuel but that is insignificant for this incident).
So if the reports above are true, the aircraft may have changed its angle of attack dramatically several times during the "bounces". With these bounces the longitudinal acceleration of the aircraft may have varied considerably, both positively and negatively, even with constant or increasing thrust output from the engines.
Additionally, the passenger's perceptions of overall acceleration would have been dramatically distorted during the bounces and impacts with the ground. There would have been considerable changes in lift developed by the wing as the angle of attack changed combined with very large reaction forces from the landing gear (both longitudinal and vertical).
Finally it appears there was considerable yaw and pitch changes experienced by the aircraft along with some roll, and these motions combine to generate accelerations for some passengers on the aircraft more so than others depending on where the passenger is located within the aircraft.
Because of all of this, passenger's perceptions of accelerations are typically not good indicators of what is actually happening to an aircraft.