How the Boeing 737 hydraulic system works. (And what happens when it doesn't)

The hydraulic system on the Boeing 737-800 is a fascinating system. In todays video I will give you an overview of what this system does, why it exists and what happens if something goes wrong with it. I will explain the details of both Hydraulic system A and System B as well as the Standby system and I will also tell you about the terrifying COMPLETE loss of hydraulics and what the pilots will do then.
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A huge shoutout to Adrian who have been helping me out with this video. Check out his channel below and give him some love!

[samanmahdiabadi]

As an AME who is working on 737, I appreciate the way you explain it to people ! keep up the good work Peter !

[cageordie]

Back in the late 50s Boeing's engineers were pretty ingenious. Most of them had a lot of experience dealing with WWII aircraft, so they made pretty rugged systems.

[Hopeless_and_Forlorn]

Great explanation as usual, even though aileron power control units are located in main wheel well and nowhere near the ailerons. The 737-100 and early -200 series airplanes had near-disastrous hydraulic problems through the early 1970s. 'A' system was powered by engine pumps only, 'B' by electrics. Main problem was vibration of EDP pressure output lines between the engine disconnect and hydraulic power module in wheel well. Even though the lines were stainless steel, nylon cushions in the clamps securing the lines ate right through them and caused high pressure leaks that rapidly emptied 'A' reservoir. Resulted in loss of A system for flight controls but not B, total loss of landing gear and flap operating pressure. Gear could be deployed manually and flaps extended, slowly, by electric motor and standby hydraulics, but nose wheel steering was inoperative. Many emergency landings and runway retrievals resulted. Original, alternate thrust reverser system was based on accumulators rather than standby system and was likewise troublesome. By the time Boeing developed and we installed fixes for all those problems, we mechanics were thoroughly sick of being soaked in hydraulic fluid at work.

[ketoninja]

OMG that poodle on the left really hamming it up around @20:45 it's like s/he knows they are on camera! So adorable!

[CatchSomeRaysWithAlisonMitch]

I have such a high commitment to become a pilot, i will definitely be getting a note book and a pen on this vid. Thanks captain 😃

[KlemensD]

My finger when mentour pilot uploads a new video:

I am speed

[MrAviationFan]

I would like to slightly correct you. Cables go through the whole aircraft, and in B737NG you actually move the cables, which than activate actuators(most of them in the wheel well, some are in the tail). I guess people think it is either hydraulics or cables on B737NG, when it is actually both in normal situation. I know that you know that as a pilot and instructor, but it might not be clear to other viewers(some of them who do not have technical background). Other than that, perfect explanation of quite complicated system. When talking to mechanics, they told me that spoiler mixer is the thing they hate on the NG due to complexity. Also, removing some actuators(for example aileron PCU) and installing them is a nightmare(due to cable rigging), unlike on A320 where it takes 20 minutes in base maintenance.

[kato]

Why would anyone down vote your awesome and super informative videos here? Your videos make me remember why I am never afraid when I fly! Thank you Mentour Pilot for always providing great content!

[alnett]

I've driven a heavy truck before with no power steering, once before I remember trying to park in a tight spot and I felt my arms were going to fall off from the pain of struggling with steering wheel. I can't even imagine how would feel to steer a plane using muscle Force.

[rajagopalvenkat]

Been watching this channel for well over a year. Only today, I noticed the red and green throw pillows - positioned as port and starboard. Subtle, but neat!

[joeldobler]

Even if im a testcell operator for the CFM56-7B i learned a lot during this video.. thank you alot peter

[tiqo]

I always wondered about this! I take the 737 a lot, but i never knew it still had cables in case hydraulic didn't work! Nice!

[ukasz-xlss]

One thing Peter, 18:17 actually the leading edge devices will be in fully extended positions once you select switch in ‚down’ position (regardless of trailing edge flaps positions). Thank you so much for another, fantastic technicial movie! Greetings

[PilotBlogDenys]

Love your tech videos. Very good for those who are going through B737 type rating course 🤘.

[jcoghill]

Most people might think that the parking brake is cable operated and completely mechanical but they would be wrong. They all use hydraulic pressure which will decrease over time and one break system is notoriously short. It's the B-737 Mark 5 brake system. To be safe you bring chocks with you to park any airplane. For long term parking you need 4 of them, but a large pair will do for nothing longer than an hour and you chock the mains, never the nose gear. First the pilot sets the parking brake. If the plane isn't moving for awhile the pilot is supposed to pull brake system breaker on the P3 panel. This totally de-energizes the circuit on the parking break preventing a slight power draw on the parking brake control valve that can cause the parking brake to lose pressure and release the breaks. That's why you always chock an airplane before you walk away. All later aircraft got rid of this problem.

[mateuszmista]

Hi! I am new on this channel. I just want to say thank you, you have a lot of great content here, all explained in an easy way. So a lot of watching ahead for me:) I hope you are doing well!

[dougchinn]

Great explanation of the hydraulic system. Love hearing about the technical aspects of flying. Considering the thickness of the manual, and accompanying checklists, I would feel confident knowing that the pilots have it memorized, and can execute it automatically without going through the checklist. The buttons, switch, which should be on, which should be off, AND when, is mind blowing. I'm reminded, that even though people know how to drive, it doesn't mean they know how a car operates. Thanks for the great job that you're doing. Stay safe.

[Suhhhhhhhhhhhhduuuuuuude]

Got my first airline job here in the states with a legacy carrier, and going through 737 initial right now, your entire series about the systems of the 737 are great! thanks for making these, helped me understand the systems much better than just reading them out of the manuals. Thanks Pete!

[Hondalover]

Wonderful presentation of a technical system. Next technical video featuring mechanisms during rotation. Thanks Mentour.

[hugodrenth]

I love the new animations of the switches in the cockpit. Great video as always :)