Originally Posted by Lonewolf
If Hi and slow, then you'd probably want to lead with pitch, so you can trade alt for a/s and your correction may work. If low and fast, likewise not a bad idea to lead with pitch.
It just doesn't work like that if slow. If you are high and slow and lower the nose in one of these pax jets, you'll end up on slope and still slow. Unless you stuff the nose down a lot, the speed will not increase. They have so much drag that any slight changes in pitch (those needed to correct back to the GS or PAPI) won't generate any meaningful speed change. That must be done with the throttles.
Conversely though, if low and fast, "speed to height" works really well, once again because of all the drag.
I say again. Watch the AP in a big jet fly an ILS. If it gets low, it pulls the stick back. It doesn't apply power and wait for the secondary effect to occur (granted, some underslung types may give a nose-up pitch to help). Same with speed: if it gets fast, it pulls the power off: primary effect of controls. Obviously if it is already on slope it cannot/won't pull the nose up. Likewise if it is slow: it doesn't lower the nose, it jams on a bunch of power. That's what pilots should do too.
Power and pitch
do work together; the first one is used to correct the error (pitch for glidepath or power for speed)
and then the other adjusts as required to maintain it's parameter.
These guys looked, from the video, to be doing the right thing with the stick: pulling back in an attempt to get back up onto the PAPI (or at least make it to the runway. Unfortunately, the system wasn't providing the power to compensate for the inevitable loss of speed.