I was flying a 737-800 aircraft cross country. When I arrived at KJFK, I activated the APPR. All was good until the final part of final approach. The plane took a dive. Miraculously, I managed to recover the plane. What was the problem and how could I fix it?
It wouldn’t have mattered if you had done that or not. The reason Chris asked is because you may not have trimmed properly or calibrated properly before you did take control, which could have led to a nosedive.
If the APPR did the nose dive did you check you where not to high on the approach because if you where APPR can and will do anything from diving down 90 degrees or pitching up 90 degrees and making you stall, make sure you where not to high on the approach and if you were you shoud’ve gone around.
If this did not happen at the very moment you switched off APPR (whether intentionally or accidentally), then what most likely happened is that you stalled out.
Many pilots give control over to AP when they intersect the ILS but forget to set the AP speed. If this happened to you, it is possible that your plane slowly lost airspeed until it finally stalled out. This would force the plane to pitch up for a bit as it tries to maintain lift with less airspeed, then the plane would basically fall out of the sky.
It’s possible that it was something else, but this is common. The best thing you can do is view your replay of the last part of your flight to see if you can spot what went wrong.
Using trim is optional for slowing down on approach. I like to use flaps 1/1 + F and spoilers armed, and turn my brakes on during short final phase to kill speed at the last second, whatever speed flaps + spoilers haven’t killed. Followed by your standard landing flare of course.
It really depends from aircraft to aircraft, but the majority of aircraft would need trim.
The amount of trim you use also heavily depends on aircraft. For example, on the A380 in IF it needs a lot of back pressure on final approach to keep the nose up. If you’re not trimmed properly, and I can confirm this from experience, the autopilot will be busy pulling up on the nose, and as soon as you take control unless you pull back on your device immediately to keep the back pressure, the nose will drop down, even if you’re calibrated. Before you take control always make sure you can’t see the magenta line on the trim tab, as that indicates whether or not you’re applying any back pressure, as I explained here. After that, trim it so it’s comfortable for you.