737 Hydraulics

This is part two of 737 hydraulics. In this video I go deep into the systems, showing you, and explaining the function of, the parts of the systems that the FCOMs leave out to give you a full understanding of the subject.
Contents:
0:00 Intro
4:11 Reservoirs pressurisation & fluid
26:38 Pumps
43:54 Pressure Modules, fuses and filters
53:32 Indications
59:12 Services
1:03:35 Redundancy
I recommend that you watch the companion video "737 Hydraulics - Wheel Well Tour" first.

[@enzino237]

These videos should be part of a type rating course. Great content.

[@ChrisBrady737]

Thanks Marco, I appreciate your support

[@user-ws6ku3nj6i]

Absolutely 👍

[@logandenelskycfi]

Just slid over to the left seat of the 737 having never flown it as an F/O and I cannot thank you enough for these videos, Chris. I also bought your book and find all of these resources tremendously valuable.

[@ChrisBrady737]

Hi Logan, great to hear that you have found the videos useful. Thanks for buying a copy of the book 🍺

[@kikskh3036]

Man the best channel for preparing the ground school b737

[@ChrisBrady737]

Thank you, you are very welcome

[@gramstalex]

Couldn't wish for a better instructor! Outstanding material presented with lots of technical insight that wouldn't be found in the FCOM.

[@ChrisBrady737]

Thank you Alexander, your kind comments are much appreciated.

[@311gus]

As a New 737 Fleet Training Instructor I can't stress enough how thankful I am fellow FTI's have directed me to these videos. As a supplement to my company Manuals and Materials this helps me in building foundational systems knowledge for me to teach our new students coming in getting introduced to the 737. Thanks Chris for these very well put videos. Continue the great work! Gus 737 FTI

[@ChrisBrady737]

Hi Gus, that is great to hear. Hopefully the students will be watching the videos as well. All the best to you, Chris

[@311gus]

​@The Boeing 737 Technical Channel thanks for the response Chris. I see dozens of students and new Fleet Training techs for our 737 fleet. I plan to definitely pass this channel on to students to broaden their understanding for their systems validations and once on the line. Question. As I broaden my teaching skills is there any videos on the 737 comm systems? Any direction would greatly help. Gus 737 FTI

[@ChrisBrady737]

Gus Chavez Jr Thanks Gus, I haven’t got around to doing a Comms video yet but it is on my “to do” list!

[@vinaymalik2986]

I am an engineer for Boeing. I found this video very informative as we don’t find videos for engineers. And in my Boeing course no one explained so clearly.

[@ChrisBrady737]

Thank you sir, that is very high praise indeed.

[@ct2289]

Best 737 content on the web, thanks for sharing your knowledge.

[@ChrisBrady737]

My pleasure, glad you found it useful.

[@rishabhchhabra777]

Such amazing content, crisp and super relevant. Makes life easy. Revising everything for my upgrade, looking forward to review the electrical next! (my least fav). Thanks a ton for your good work, sending you a virtual cold one! 🍻

[@ChrisBrady737]

Thank you for your kind comments. I hope to have a book out very soon to accompany this video series. It should help you for your upgrade.

[@rishabhchhabra777]

@@ChrisBrady737 looking forward to the book release.

[@AUav8r05]

Chris, thank you so much for the videos. I’m sliding from the right seat of the 75/76 to the left of the 73NG. I greatly appreciate the info to help fill in the blanks before training. Happy New Year! Cheers from the US.

[@ChrisBrady737]

You are very welcome. Enjoy the 737

[@telescope64]

Thanks Chris.This presentation gave me a clear insight into the hyd systems normal and alternate operation across the different models.The operational implications of the various failures was really useful to me as an engineer.Keep the modules coming!🤩

[@ChrisBrady737]

Thank you that is great to hear. I am glad these videos have appeal to both pilots and engineers.

[@stephendevlin1427]

Gday Chris. You have a great way of imparting knowledge without the "hypnotic effect" of the FCOM's. Great job.

[@ChrisBrady737]

Thanks Stephen, that was what I was trying for 👍

[@T0MaTOS]

THANKS FOR SHARING CHRIS! Your knowledge and insight of the 737 is invaluable to us!

[@ChrisBrady737]

My pleasure Jay, thanks for watching. Tell your colleagues!

[@T0MaTOS]

@@ChrisBrady737 I always do, tell them how amazingly in depth your systems reviews are...

[@ChrisBrady737]

@@T0MaTOS thanks Jay, much appreciated

[@jefferybauman9393]

CHRIS BRADY...THANK YOU SO VERY MUCH FOR THIS SERIES OF BOEING-737 SYSTEM VIDEOS I REALLY AM IMPRESSED BY THE HISTORY AND THOROUGHNESS OF EACH SYSTEM INFORMATION

[@ChrisBrady737]

You are very welcome

[@harisshahulhameed5966]

It's really useful video. Explained everything in a simple way and can easily understand. Thanks for the video.

[@ChrisBrady737]

My pleasure. Glad that you found it useful. Hopefully you will enjoy my other videos as well.

[@airbxnee]

Preparing for my TR next month and these have been amazing, thanks a lot for the work you put into them!

[@ChrisBrady737]

My pleasure. Please spread the word about my channel.

[@jackzakaria3276]

Very clear explanation, wll done Chris

[@ChrisBrady737]

You are welcome

[@cpuwolf]

Stonish myself stay here for more than 1hr as a software engineer. Thank you anyway. I learnt a lot

[@ChrisBrady737]

My pleasure, glad you found it useful

[@AlejandroGomez-zn8uq]

Thanks a lot. Its really good for recap while we are in furloughed. Again thank you very much for all this videos.

[@ChrisBrady737]

My pleasure, tell your colleagues 👍

[@sodakworld4864]

Brilliant explanation, thank you

[@ChrisBrady737]

Glad you found it useful

[@balazsegressy3788]

Great video/presentaion again!! I would like to share some additional info/tips: -The reservoir head pressure prevents not only fuming of the fluid but the caviation of the pumps. In case of no head pressure the pumps are ruined in 2 minutes because of cavitation. Happened in the hangar. Indication of the caviation: Very high pitching sound from the pump , switch it off immediately -Be cautious about the hydraulics level on the NG. The maximum indication is 106. If it is above this level the indication is still 106. If the reservoir overfilled and the pressurization check valve is damaged hydraulc fume enters the airconditioning system. So the normal level before flight is around 100% (unless your company procedures differs) -You can have high amount of fluid leak from the overflow drain mast in case of retracting the gear from B system when no.1 engine is out and the transfer valve is shifted. In this case during retraction the A system fluid returns into B reservoir which can easily overfill it. -Boeing manufactures the 737 with Hyjet IV / V hydraulic fuids. Skydrol and Hyjet are totaly intermixable -If you run the Electrical pump without minimum fuel for cooling you can do very limited movements. For example retracting or extending the flaps one cycle. If you do more the fuid will overheat. -The standby pump and the PTU are designed for emergency/non-normal operations only not for extending operation. It happened in the hangar that the guys were running the standby pump for 1 hour constantly and its gone. Had to be replaced. - In case of operating the flaps with the alternate electrical motor the flaps will move very very slow.

[@ChrisBrady737]

All good info and tips. Thank you very much for sharing your knowledge.

[@balazsegressy3788]

@@ChrisBrady737 Thats why we are here on your channel! To learn and share!

[@drissneqrouz]

شكرا جزيلا على هذا العمل العظيم، وأتمنى لكم التوفيق والمزيد من العمل حتى نستفيد منكم

[@ChrisBrady737]

You are very welcome.

[@mrsako7223]

Thank you Chris, you’re a great instructor. Well done!

[@ChrisBrady737]

My pleasure, glad you enjoyed the video.

[@ps9633]

omfg! This is great. Thank you a lot for these videos!

[@ChrisBrady737]

You are welcome. I am in the process of compiling a book of these videos. Hopefully you find that useful as well.

[@cezarmarius732]

Mr CDT only applause for all your videos.

[@ChrisBrady737]

Thank you, I appreciate your comments

[@PhilippeBorfiga]

Thank you very much ! So in deep, really perfect ! ... a lot of other movies to look at now :) Very Great work !

[@ChrisBrady737]

My pleasure, glad you like them.

[@steffenleo5997]

Thanks a lot for this very great and details explained Video Capt Brady... 2 thumbs UP for your Video... 👍👍🙏

[@ChrisBrady737]

Thanks Steffen, glad you like them. Tell your colleagues 👍

[@bigmakskartoshechkoy6210]

Great! So much new information to reflect! Thanks a lot!

[@ChrisBrady737]

My pleasure, thanks for watching.

[@patricksin4192]

On Max, the overtemp sensor on EMDP does not give "OVERHEAT" indication in the cockpit but shuts off the related EMDP. Only the overheat sensor in EMDP case drain hydraulic fluid gives "OVERHEAT" indication(approx 107C).

[@ChrisBrady737]

Thanks for the info.

[@muratyuce3756]

Thanks captain for your great explanations!

[@ChrisBrady737]

My pleasure, thank you for watching. Please tell your colleagues.

[@rishabhchhabra777]

Foaming can also be seen & understood in coke bottles or cans, sudden reduction of pressure & we see a fizz. A way to understand the foaming mechanism.

[@ChrisBrady737]

Correct

[@captthunderbolt164]

Excellent presentation.

[@ChrisBrady737]

Glad you liked it, thanks for watching.

[@Zettasfera]

Спасибо за подробные объяснения

[@ChrisBrady737]

You are welcome

[@terencenxumalo1159]

good work

[@ChrisBrady737]

Thank you

[@liderul11]

Very nice videos , thx for this Chris !!

[@ChrisBrady737]

My pleasure, thanks for watching

[@akashoa7929]

Excellent

[@ChrisBrady737]

Thanks 🙏

[@ElfoRomagnolo]

Brilliant presentation, thanks!

[@ChrisBrady737]

You are very welcome, thanks for watching

[@panagiotissoutsas7851]

Captain you are an Ace!!!! Can you do one video for flight management and navigation please in the future?

[@ChrisBrady737]

Thanks for the suggestion, I will look into that in the future

[@ramyelioa8187]

thank u very much

[@ChrisBrady737]

You are very welcome, thanks for your support.

[@hzgl]

That was another brilliant episode, thanks Chris! Do you happen to know whether a windmilling engine will generate beyond negligible amount of hydraulic pressure in its respective system? I'm curious whether manual reversion would become easier when you fly faster!

[@ChrisBrady737]

Thanks for your kind comments. Re your question for manual reversion to occur you would have to lose either all 4 pumps and therefore both engines and the APU or both hydraulic quantities. Anyway to answer the question will a windmilling engine give its EDP enough power to provide hydraulic pressure the answer is unfortunately not enough and of course you can only maintain high speed for a limited time. Also if there was engine damage you will have pulled the fire handle and shut-off the hydraulic output. Don't worry about making manual reversion flight easier, I have done a lot of it and it is very manageable!

[@hzgl]

@@ChrisBrady737 Thanks captain!

[@hommedefer5985]

thanks a lot sir

[@ChrisBrady737]

You are very welcome

[@hugoweber5317]

Hi Captain, amazin content as always. Please, could you tell what exactly "manual reversion" means? is it something that open some valves for high pressure under the wing to go into the balance pannels? does the flight controls switch need to to go "STBY RUD" otherwise manual reversion will not "start"? is it something that is always on and hydraulics only make things easier? any light on the subject is welcome! thank you for you time to read this!

[@ChrisBrady737]

Hi Hugo, Manual reversion is when you lose hydraulic systems A & B to the primary flight controls. The rudder will remain hydraulically powered from the standby hydraulic system. Loss of hydraulic power to the elevators and ailerons makes them very heavy but there are balance tabs to assist (see my Flight Controls videos for details). I have flown hundreds of hours of real manual reversion under controlled test conditions and the controls are heavy but it is easily flyable and just takes a little getting used to. If you watch my FC Pitch or Roll videos I explain tabs and manual reversion a bit more.

[@resolv204]

Hey great video. Question, if an engine fails in filght and is still windmilling do you still have some hydraulic pressure in the system driven because N2 is still rotating ?

[@ChrisBrady737]

You may still have a little hydraulic pressure from the EDP, it depends upon your IAS what N2 you will have. Don't forget you will still have the electric pump for that system so the hydraulic pressure for the system should be unaffected.

[@GAEPOPO]

I studied EDP damaged when EDP supply valve close & ENG rotate by windmilling... so how to prevent EDP from this situation??

[@ChrisBrady737]

I do not know, that is beyond my knowledge.

[@T0MaTOS]

THANK YOU, CHRIS!

[@ChrisBrady737]

My pleasure

[@Buzzlightyear706]

Hi, another fabulous video! Great explanation of a very confusing system, especially that in the FCOM there's very little info. Could you please clarify how should I understand that PTU standpipe? Both you and FCOM say that "(...) fluid remaining in the system B reservoir is sufficient for power transfer unit operation." So if you happened to lose all system B fluid right after take-off, would PTU allow normal LED retraction, like nothing ever happened? And then extension? That last sips of hydraulic fluid can do it? I undrestand all other scenarios involving PTU, it's just I can't wrap my head around that lowest standpipe and what's the purpose if we lose all the fluid. I checked both your video and Cockpit Companion looking for answer but still can't get that.

[@ChrisBrady737]

I think you are overthinking it. If the FCOM says "that the fluid remaining in the system B reservoir is sufficient for power transfer unit operation." then that is the case. The PTU should be able to function normally in the scenario you describe. The purpose of the standpipe is to enable the PTU to remain available if there is a B system leak in either the EDP, EMDP or any of their lines. Again, don't overthink it! :)

[@Buzzlightyear706]

@@ChrisBrady737 Sure, thank you very much for clarification!

[@marcelszabo9585]

You're a Legend for making these ! I also purchased your book after seeing how well done these are. One question, wouldn't PTU overheat illuminate the A side overheat since the motor is on the A system ? Thanks

[@ChrisBrady737]

Thanks Marcel, glad you are enjoying them. I don't believe that the PTU will do that but I could be wrong.

[@joker6946]

Noobie here! Why if we lose Sys A we are unable to raise the ldg gear? Isn't that the purpose of the LGTU? Thank you in advance

[@ChrisBrady737]

Hi, no that isnt the purpose of the LGTU, it is for the loss of engine #1. Recheck the LGTU slide near the end of this video.

[@dinamiena6186]

Captain I hope you are doing well ! I have a question! The LGTU is using HYD B psi to rise landing gear when No1 engine fails. We are talking for pressure and and not fluid exchange correct? That means if we have sys A loss the LGTU will not kick in because the rpm on n1 is normal! In case we have sys A loss because of leak and at the same time we lose n1 engine is the 20% fluid left on the standpipe is enough to rise the gear with LGTU? And is this the reason why the fluid remains at 20%? Thank you

[@ChrisBrady737]

Re "The LGTU is using HYD B psi to rise landing gear when No1 engine fails. We are talking for pressure and and not fluid exchange correct?" - Correct Re "That means if we have sys A loss the LGTU will not kick in because the rpm on n1 is normal!" - The LGTU will not work with a loss of A. Re "In case we have sys A loss because of leak and at the same time we lose n1 engine is the 20% fluid left on the standpipe is enough to rise the gear with LGTU? " - The LGTU will not work with fluid loss Re " And is this the reason why the fluid remains at 20%? " - No, see above. You have got several failure modes confused here. I suggest that you look again at the specific circumstances at which the LGTU operates.

[@dinamiena6186]

@@ChrisBrady737 thank you very much !

[@flyplane4962]

Great Chris! Question: are the hyd/fuel heat exchangers different for EDP/EMDP or is it actually the same? Thx

[@ChrisBrady737]

It is the same heat exchanger for both EDP and EMDP case drain fluid.

[@maloukification]

Great content THANK YOU

[@ChrisBrady737]

You are very welcome

[@DPtheOG]

Bonus points for the hydraulics having Ukraine colors.

[@ChrisBrady737]

True!

[@ManuelFernandez-mt4sd]

Hello Capt Brady, on the Hydraulic Quantities table, about the EDP and EMDP Standpipes for the B system on the classics, i didn't get why there is so much Quantity left (40% and 11%) in comparison to the Max which is 0% for both, could you elaborate on why the difference please?

[@ChrisBrady737]

I dont know why the design difference but I am sure the Max system will be an improvement on the Classics.

[@johannthiveyrat8077]

Hi Chris, Thank you for your channel. Very interesting. I have one question: do you know the minimum time requirement for landing gear retraction, in cas of an engine failure, to comply with performance specifications? (not able to find it in CS-25). Regards, Johann.

[@ChrisBrady737]

There is not directly a minimum time for retraction but there is an engine-out minimum take-off (and go-around) climb gradient requirement from 400ft. If the gear is not up by 400ft, it is unlikely that the gradient will be met. Without the EDP, the gear would not be up in time.

[@johannthiveyrat8077]

@@ChrisBrady737 Great, thank you!

[@balazsegressy3788]

Extract from AMM 32-32-00-710-801 Par D. including my own note: Move the control lever for the landing gear to UP and measure the time for the retraction. Measure the landing gear retraction time from the time the control lever is put in the UP position until all the landing gear red "disagree" lights go off. Make sure the landing gear is up and locked in 9.0 seconds or less. Move the control lever the DN position and measure the time for extension. NOTE: Measure the landing gear extension time from the time the control lever is put in the DN position until all the landing gear green lights come on. Make sure the landing gear is down and locked in 13.0 seconds or less. NOTE: Engine Driven Pump EDP and Electric Motor Driven Pump (EMDP) together pressurizing the A system in this case, or in the hangar we use ground cart. EMDP alone does not have the flow rate to measure extension / retraction times.

[@ChrisBrady737]

Great info, thanks for sharing

[@banty186]

Thanks sir great video 🙏

[@ChrisBrady737]

You are welcome

[@naguganesh5166]

In case of hydraulic system B failure yaw damper will be disengaged, in this scenario how aircraft turn is co ordinated without yaw damper ?? And also plz explain why aircraft crosswind capability has been greatly reduced during manual reversion even rudder travel range is same as during normal operation ??? Could u plz explain

[@ChrisBrady737]

It can't. Primary YD is from Hyd sys B. Standby YD is from the Standby Hyd sys. Flying with the YD U/S is not a big deal, you hardly notice it.

[@SHERYAN2022]

Thank you But this is for 737ng or classic? 🙏❤️

[@ChrisBrady737]

If you watch the video you will see that it covers all series

[@SHERYAN2022]

@@ChrisBrady737 Thank u M 🙏 As soon as possible🙏 U can tell us what the deference between ng & classic in general ???

[@mattiafornataro3228]

Can someone explain me clearly EDP depressurization solenoid valve, and EDP switch on/off position? Tks

[@ChrisBrady737]

The EDP and the electric motor-driven pump (EMDP) each have a switch on the hydraulic panel. The switches have two positions, ON and OFF. The ENG 1 HYD PUMP switch controls the EDP for system A. The ENG 2 HYD PUMP switch controls the EDP for system B. Each pump has a depressurization solenoid valve. The valve blocks pump output pressure to the main hydraulic power system when the ENG 1 or ENG 2 HYD PUMP switch is in the OFF position.

[@DL14204]

Great video as always! Question, just to confirm. The LGTU is only helpful in a Engine Out Situation (No1) and serves as no help if Hyd Sys A is lost and manual extension is utilized?

[@ChrisBrady737]

Correct

[@DL14204]

@@ChrisBrady737 And by "Hyd Sys A lost" I meant that the fluid in Sys A is gone(burst). That is more accurate confirm?

[@ChrisBrady737]

@@DL14204 correct again

[@miguelr1784]

A question that I could not get the answer yet. In case of loss of Hydraulic System, which Low Pressure will illuminate first?? For the EDP, the EMDP or both at the same time?

[@ChrisBrady737]

For loss of a hydraulic system you probably mean loss of fluid, in which case it depends where the leak was for which pump you will lose first. If in the wheel well then probably elec pump, if at the engine then probably engine pump. Every leak will be different

[@miguelr1784]

@@ChrisBrady737 hello, yes I mean in case of a leak on common lines the fluid quantity will decrease to 0 or 20% depending on the system. My question was about which pump will fail first.

[@ChrisBrady737]

@@miguelr1784 Again, It all depends exactly where the leak is and what hydraulic systems you are using at the time. It is impossible to give a general answer. In any case, the procedure will be the same.

[@miguelr1784]

@@ChrisBrady737 thank you. And thanks for your high quality content, I'm enjoying them a lot. Keep them coming please 😊

[@Driver170]

Hi, will the PTU retract the LEDs

[@ChrisBrady737]

Yes

[@Driver170]

@@ChrisBrady737 So why does the QRH loss of SYS B not mention this?

[@ChrisBrady737]

I am not responsible for how Boeing writes its manuals and therefore cannot comment on why things are written in a particular way... I think you are confusing the function of the PTU with the alternate flap extension system (standby hyd). The PTU is to make the LEDs operate at the normal rate in the event of reduced or lost sys B. If you use the alternate system to extend the LEDs then they cannot be retracted.

[@T0MaTOS]

Hey Chris? Got a question for you regarding the LGTU. If you take off and while the landing gear is retracting, you lose system A hydraulics, will the landing gear still retract or will it extend? Engine No. 1 is operating normally. But is the N2 < 56% rpm one of the criteria for the LGTU to operate? Thanks in advance, Chris!

[@ChrisBrady737]

It will retract more slowly as the engine runs down until N2

[@T0MaTOS]

THANKS for the answer, Chris!

[@T0MaTOS]

Oh Chris? There is no failure of the No. engine. Just a loss of hydraulic system A.

[@banty186]

Sir if nose wheel stearing line burst during landing or after landing (due to fod), then how does stearing system work??

[@ChrisBrady737]

Try selecting Alternate nose wheel steering

[@banty186]

@@ChrisBrady737 even select alternate stearing switch also hydraulic pressure goes same stearing line. I hope you understand my question?? Thanks

[@extremehdsimulation5752]

Thx Captain! Question: in case of dual engine shutdown and unable to restart engines, apu not operative (in an in-flight zero fuel scenario), will windimilling engines provide some hydraulic pressure or it will always be only manual reversion ?

[@ChrisBrady737]

Even at high IAS, the EDPs will not be turning enough to give enough hydraulic pressure for flight controls. Assume manual reversion. Also remember if damage then the fire handles will have been pulled so no EDP output anyway.

[@extremehdsimulation5752]

@@ChrisBrady737 Thanks a lot

[@ChrisBrady737]

No problem, please spread the word about my channel

[@sasmsamy962]

@@ChrisBrady737 Chris, same question (both engines failed) with the APU gen's on line. How much of the hydraulic load will the electric pumps be able to handle? Flaps extension rate ?

[@johannthiveyrat8077]

By any chance, do you plan to record an airtest video?

[@ChrisBrady737]

I hadn’t planned to do one but I guess I could if you think there would be enough interest

[@ethiopianchristianchannel6304]

Can anyone tell me why system B reservoir is bigger than system A

[@ChrisBrady737]

It is because of the different service it supplies.

[@ethiopianchristianchannel6304]

@@ChrisBrady737 Thanks captain

[@user-bb9mi3tn1o]

+

[@ChrisBrady737]

👍