Originally Posted by
Cows getting bigger
737 driver, I have an itch and please take this comment with the best of intent.
When I was taught to fly, PPL through CPL etc, it was instilled in me to understand what every switch/knob did before I played with it (initial thanks to Norman Buddin, ex Hunter pilot and CFI). We were not in the business of altering things without understanding the impact.
So, please correct me if I am wrong, but earlier versions of the 737 had two distinct outcomes associated with the two stab trim switches whilst the Max basically has two switches in series? Somewhere along the line a change operating procedures seem to have pre-dated the wiring change. I’m trying to understand why pre-Max pilots didn’t know, or weren’t told about, the difference between the switches. Isn’t it better airmanship to understand why, what and how when managing aircraft systems, or are we witness to the pre-cursor of ‘Children of the Magenta’ in pilots who never questioned why they threw two switches and what each did?
If it hasn't already become evident, I am also a product of the old school philosophy of pilot training. That being said, there were plenty of times where even I thought we were being required to know far too much technical knowledge than was necessary.
Somewhere along the way, our training started to change. There was far less emphasis on understanding the systems and far more emphasis on following the written procedures. Our training has become highly scripted, and we almost always know the sim training scenarios in advance. I suspect that this change has largely been driven by costs, with modern airlines being reluctant to provide anything other than the minimum training required by the FAA. (You've probably heard the saying, "If the minimum wasn't good enough, it wouldn't be the minimum!")
Frankly, some pilots welcomed this change because it is less work and less threatening. There has always been lip service to the concept that, in some circumstance, the pilot may not have a well-defined checklist or procedure to follow and was expected to use their best judgement. Unfortunately, that sentiment has rarely been backed up with any kind of training. Unfortunately, I think we have seen enough accidents and incidents to in the last decade to show that there is a real, if unaccounted for, cost to this approach to training. Sadly, I still don't see any motivation to make the needed changes to the typical industry training regime. We apparently haven't produced a high enough body count to justify it.
As to your specific question, I have gathered from some of the other posters here that there was no change to their runaway stab trim procedure, that they always used both cutout switches. All I know is that at my airline, we used to be allowed to use them separately. This procedure was changed a few years back (can't remember exactly when, and I don't have any of the old manuals). At the time, I remember being told that this was a Boeing-preferred change driven by a larger trend of removing most types of troubleshooting activities from our non-normal procedures. In my current 737NG manual, there is no longer a reference to the functionality of the two cutout switches. I only know because my experience predates the change. Since current 737NG pilots aren't taught how these switches are wired, I guess there would be little point to telling them how the MAX switches are wired, and as I have previously stated, there is absolutely no difference in the aircraft from a procedural perspective.