Originally posted by Evan
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Tell me one thing: In a "pitch controls speed" mode, why would the plane pitch up for the insignificant reason that you selected a higher altitude?
Answer: it wont. The pitch holds the speed, not the altitude. The only function to set an altitude in FLCH is to the system (FD and AT) to revert to ALT HOLD (FD) and SPEED HOLD (AT) once and if the selected altitude is achieved.
The reason why the plane climbed when he selected FLCH is because the plane was flying faster than the SPEED (not altitude) left in the MCP. The FD was commanding pitch up to slow down, and it would have done so even if the selected altitude was lower that the airplane's altitude.
The MCP reference speed was also too high, prompting the A/T to increase thrust (as it was in THR mode)
Where the selected speed was too high? The selected speed was below the actual speed all the time (until the plane became low and slow at the end).
In short, they were in a "pitch holds speed" mode.
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