Just read something about the 737 rudder system that made me rethink a training point

I was going through some old NTSB reports and saw the detail about United Flight 585. The investigation found the rudder actuator could move to its full travel in under a second with just a small input. I always thought those systems were slower to react. Has anyone else had to adjust their mental model on hydraulic control surfaces after digging into those older incidents?

3 comments

3 Comments

amy_sanchez3mo ago

The full rudder travel in under a second is a scary number. When you picture that in a low speed go-around, like the USAir 427 scenario, does it change how you'd teach recovery timing? I mean, if the rudder slams over before you can even say "power's set"...

elliotjenkins21d ago

The timing piece is what gets me. Even if you drill the recovery muscle memory perfectly, that rudder moving full travel in under a second means you're reacting to the aftermath, not the cause. At low airspeeds with full power kicking in, the yaw just gets locked in before you can even process it's happening. How do you split your scan in that moment - do you teach people to go straight for the control inputs and trust the engine gauges, or do you try to catch a glimpse of the rudder position first to confirm what blew up? Because staring at the rudder for a split second might cost you the aircraft.

elizabeth_bailey263mo ago

That United 585 report is a tough read. The key thing for me was realizing the rudder power control unit could reverse direction almost instantly. It made me go back and really picture the hydraulic pressure in those lines. Now when I run through system failures in my head, I give the rudder a much wider, faster swing in the scenario. It changes how you'd plan to catch a slide.