737 Flight Controls - Yaw

This video is the second of the 3-part series on Boeing 737 Flight Controls. This one covers yaw.
Contents:
0:00 Intro
0:31 Rudder
6:13 Rudder Control
16:29 Rudder Trim
35:02 RSEP
49:09 Rudder Power
52:34 Yaw Damper
1:07:55 Vertical Stabiliser

[@brendanaustin8757]

Nothing better than a notification from Chris Brady,you may well be the person who gets me back into aviation maintenance after watching these. Best description and presentation of systems out there by far.

[@ChrisBrady737]

That is high praise indeed, I am humbled by your words. Best of luck

[@eprn1n2]

The analog 737. Amazing engineering.

[@DL14204]

With the pandemic shutdown and return to work recalls this material is very much appreciated. Great stuff to help get back up to speed.

[@ChrisBrady737]

That is great to hear. Glad the videos are useful.

[@GabrielEngle]

Phenomenal! Such a great way to fill in the gaps and flesh out more detail that the FCOM often leaves out. Much appreciation for the time you put into this.

[@ChrisBrady737]

My pleasure, glad you enjoyed it.

[@aenobre]

I've been watching your videos for a while now, many thanks from Brazil. Please keep posting because it's really helping remembering and also learning a lot too. It was very cool seeing a photo of an airliner that I fly in the beginning of the video. Kind regards

[@ChrisBrady737]

Thank you for your kind comments, I certainly will keep posting as long as people want them. I remember flying the GOL aircraft well.

[@inspirationunboxed8273]

Excellent video and explanation with very insightful photos. Love your videos to the core Capt.

[@ChrisBrady737]

Thank you very much for your kind words. I’m so glad you enjoyed the videos. Please tell your colleagues and thanks for watching.

[@Buzzlightyear706]

Awesome, great content!

[@ChrisBrady737]

Thanks Buzz 👍

[@HDTokyoAviation]

Hi Chris, Your videos are incredibly useful and I am so grateful that you create them and publish them online free of charge, it has given me so much confidence in my technical knowledge beyond the scope of what's written in the manual and has helped me particularly during times where we have encountered technical problems on the ground and need to consult engineers about certain things! I was wondering if it would be possible to perhaps create a video one day discussing the 737 rudder story as written on your website with possibly some illustrations, diagrams and pictures of the components associated with the previous issue and the new fix? I am very interested in that particular topic however I am more of a visual learner rather than reading the information on your website. Thank you as always and I look forward to more great content in the future!!

[@ChrisBrady737]

Thank you very much for your kind comments about my videos. Yes the 737 Rudder Story is on my to-do list for future videos. Thanks for watching, tell your colleagues!

[@HDTokyoAviation]

@@ChrisBrady737 I very much look forward to it, thank you ever so much once again for creating this superb content and I most certainly will be spreading the word!

[@2Tool4School]

New upload, yes! Nothing better than waking up and sipping some coffee to these

[@ChrisBrady737]

Enjoy!

[@nayyarjaffery1051]

Excellent presentation from maintenance point of view as well. Thanks from Miami, Florida.

[@ChrisBrady737]

That is good to hear. I pitch these towards pilots but giving them extra info not available to us, often from the AMM or other maint documents so I guess there is a lot of interest from engineers as well.

[@MatthijsvanDuin]

3:20 Depleted uranium is actually slightly _less_ dense than tungsten, so density would not be a reason to prefer DU. My guess would be it probably had to do with cost and availability. The primary danger of DU is its toxicity if the weight is compromised (e.g. in a crash or fire), not radioactivity. Boeing did a study that monitored whole body exposure and peripheral exposure (using a finger ring dosimeter) of workers who installed, transported, or otherwise handled these weights and of the 297 exposure reports collected only 3 were above the detection limits and these were all still very low exposures with no associated health risks. The radiation from DU weights poses zero risk to crew and passengers, and is certainly irrelevant compared to the (cosmic) radiation exposure caused simply by flying at cruise altitude.

[@ChrisBrady737]

Thanks for the info, good to know.

[@walkingowl6810]

thank you for the videos. excellent for newbies to learn about how planes fly.

[@ChrisBrady737]

My pleasure, thank you for watching. Good luck with your studies

[@redpillinsights7747]

Thank You!

[@ChrisBrady737]

You are welcome

[@JTL737]

Been waiting for this and the pitch. Thank you Sir ;)

[@ChrisBrady737]

My pleasure. Pitch will be the next video but it will be at least a couple of weeks

[@-brent-1594]

i really learned a lot from your videos, best regards from china

[@ChrisBrady737]

Thank you Brent, I didn't realise that KZbin was available in China but great to hear that it is. More videos to follow, please tell your colleagues.

[@-brent-1594]

​@@ChrisBrady737 The truth is KZbin is still unavailable in china, but nothing's gonna stop a person who is eager to learn :) Also I bought the book that you wrote and translated by capt. chen. I really appreciate the work you've done. And I definitely will notify my colleagues. Wish you all the best!

[@T0MaTOS]

THANKS AGAIN CHRIS!

[@ChrisBrady737]

My pleasure

[@telescope64]

Thanks Chris for this brilliant video.Lots of things I never knew,plus lots of reminders and as always it's good for us engineers to get the pilots viewpoint. Probably a dumb question,but you described how in rudder manual reversion WTRIS will give a little rudder if the pilot operates the control wheel.I just wondered why the pilot wouldn't just use the rudder pedals (using standby system/pcu) to get the co- ordination from the rudder for the turn?Why is wtris needed? Thanks again!

[@ChrisBrady737]

Hi Paul, Good question, the answer is that pilots of swept wing jets, unlike glider or light aircraft pilots, don't (and shouldn't) use rudder to coordinate turns, it simply isn't necessary. The only times we use ruder trim are for asymmetric thrust (engine out) or if the aircraft isn't flying straight (mis-rigged or damaged). WTRIS is not needed (it wasnt there on the Classics) but is helpful to assist (not coordinate) turns in manual reversion.

[@telescope64]

Thanks for the answer,all clear now,great!P.

[@vikkimcdonough6153]

3:46 - TBH, the main issue with DU isn't its radioactivity (which is very mild) so much as it simply being poisonous.

[@ChrisBrady737]

I didn't realise that, thank you.

[@christiandrums]

Hi Chris, regarding the Yaw Damper, I've been looking a bit for info on what the turn coordination mentioned in the FCOM actually covers? I came to think if it's actually only during manual reversion that this is provided through the WTRIS or is it as well during normal ops? And do you have some more info this topic specifically? (i.e. what inputs does it get/when is it activated) Thanks for some absolute fantastic videos!

[@ChrisBrady737]

The Yaw Damper is used in normal flight. In a nutshell, it commands rudder movement in proportion to and opposite to the aircraft yaw. This keeps unwanted yaw motion to a minimum and makes the flight smoother.

[@umi3017]

Thanks for the upload! many great info! I have heard recently a 738 have same issue of knob confusion and get into like 45degree bank of upset, but not much detail yet... Regarding the rudder over stress, I have seen a great article about why the rapid reverse input of rudder would cause over stress above the designed limit: ifalpa.org/media/2029/12adobl02-use-of-rudder-on-boeing-aircraft.pdf

[@ChrisBrady737]

The FAA SAIB recommended that operators put the two knobs in a standardised position to help avoid such events. I am familiar with the IFALPA document, it is excellent.

[@fauvevertegaal3458]

Hi Chris, awesome presentation as always. i just have a question about the yaw damper. Why is the stby yaw damper inoperative with loss of system B even if the stby system is "powering" the stby rudder PCU and stby yaw damper?

[@ChrisBrady737]

I didnt think it was. The standby YD is powered by the standby hydraulic system and controlled by SMYD 2. This occurs during manual reversion when there is no Hyd A or B.

[@Jean_M632]

I have exactly the same question and I fail to understand : why cant we have the stby yaw damper in case of loss of syst B ? As I understand it, once the stby rudder SOV is open (manually or automatically), the stby rudder PCU AND stby yaw damper should now be powered. So why can’t we put the yaw damper switch back on, as we would do in case of manual reversion ? (Thank-you Chris for all those great videos)

[@guilhermechaves5957]

Graet video, Captain! I have onde quick question about the yaw damper. Do you know why flaps are limited to 30 without yaw damper? Thanks!!

[@ChrisBrady737]

Great question. I dont know the answer for sure but I suspect it is a handling issue. The restriction used to be (pre-2015) that you could not use flap 40 if the crosswind exceeded 30 Kts. The restriction is there for all series of 737.

[@kristoferstensvik6515]

Hi Chris, thank you for your videos. I’ve now watched all three pitch/roll/yaw videos in a row. What I don’t understand about the rudder is how it can “backdrive” the rudder pedals with the hydraulics off. Like, when you are parked in a crosswind, so to speak, and the rudder is deflected so are the pedals in a corresponding way. How can this transfer of movement happen when there is only a hydraulic connection between the pedals and the rudder surface?

[@ChrisBrady737]

It isn't only a hydraulic connection, the connection is also mechanical through the PCUs.

[@steffenleo5997]

Good Day Capt Brady, in this video 45:35 stated Rudder pressure limiter.Is this system similiar with elevator feel and centering system for elevator? I mean here for low speed easier or less force we need to move rudder pedal and at high speed require more force to move rudder pedal?

[@ChrisBrady737]

The RPR is not analogous to the Elev feel system. The RPR is to reduce the amount of rudder deflection in certain circumstances to allow a rudder hardover to be counteracted by aileron. I will cover the rudder story in full in a future video.

[@steffenleo5997]

@@ChrisBrady737 Thanks a lot Capt Brady... Wish you a nice weekend... 👍👍

[@aviator5038]

Hello Chris, i have a question why Autopilot is not having an interface with rudder ? in B737NG. Thank you.

[@ChrisBrady737]

There is an optional rudder channel for the autopilot since the NG. This enables CatIIIB autolands with rollout.

[@steffenleo5997]

Good Day Capt Brady, if we fly with autopilot on/engaged and we step on rudder pedal to apply some rudder.Will this action disengaged the autopilot automaticly?

[@ChrisBrady737]

This is such a hypothetical question, why would you ever do this? If the A/P is engaged let it fly the aircraft and apply rudder trim if necessary.

[@ChrisBrady737]

Anyway, no the autopilot won’t drop out until the autopilot aileron limit is reached. Watch the Fuel video I did for an example of this.

[@steffenleo5997]

Thanks a lot Capt Brady for your explanation... 👍👍

[@GNX157]

Not even done the video yet, but I gotta say, that first trim runaway story needs to be broken out and made again in a separate video. Hopefully the NTSB and the FAA got a report on this?

[@ChrisBrady737]

I certainly filed an MOR for that incident which went to the CAA as well as the company.

[@elmin2323]

Question can you move the rudder under manual revision? Why do the pedals move around when theres a wind out side and the hydraulics are off? They must be connected directly?

[@ChrisBrady737]

Yes you can. Because there is a mechanical connection through the PCUs even when they are unpowered.

[@elmin2323]

@@ChrisBrady737 exactly what I was thinking

[@DL14204]

If you lose Hyd Sys B Pressure(A sys normal). How is the Yaw Damper powered?

[@ChrisBrady737]

If you lose Hyd Sys B then you lose the Yaw Damper.

[@DL14204]

@@ChrisBrady737 okay thought so. Seemed odd that the “standby” YD is not available.

[@GlutenEruption]

FYI, the formula for kinetic energy isn't E=mc2 it's KE=1/2mv2 (1/2 mass x velocity^2). That results in a linear relationship between mass and KE (double the mass = double the KE), and an exponential relationship between velocity and KE (double the speed, quadruple the KE). Great breakdown though - more calm, intelligent, rational voices like yours are desperately needed in this sea of wild speculation and unhinged conspiracy theories.

[@ChrisBrady737]

Thanks as always for your feedback. It is a2-3 years since I recorded this video so I don't remember saying E=mc2, especially not if I was referring to kinetic energy. As a physics graduate I know this basic stuff. If I said it, I was wrong and can only put it down to my age!!