Would your procedures allow you to disconnect the A/P at this phase of flight and try the other channel? When you have something like this happen its very helpful to be able to tell your maintenance people whether it was common to both sides, and what the A/P was like before and after (ie the return sector) the event.
Quote:
| Another thing that springs to mind is the abrupt motions on the control column when initially engaging the A/P in such aircraft. You sort of notice straight away that something's not quite right. |
Thats because something is indeed not quite right, it is possible to set up the A/P on all models of B737 so that the control column doesn't snatch on engagement. At one place I worked we did the LH B737s and their quality people on site would insist that they were set up this way, even the slightest movement of the control column on engagement would be cause for rejection.
We would spend hours carrying out fine adjustments on the position sensors to get the null point as precise as possible, it was time consuming but highly satisfying when it all came together. No other company I ever worked insisted on such attention to detail in this matter and its not uncommon to see huge deflections on some aeroplanes. Whenever I set up B737 autopilots since then I would always try to get it as close as possible, but none of these operators would ever tolerate a delay in getting the A/C out to allow the adjustments required to get it spot on, particularly when its something that the pilots rarely if ever comment on or possible even notice.