Electrical System - B747-400 | B747-8

This Tutorial Briefing Covers The Electrical System Description of AC Power Distribution, DC Power Distribution, and The Standby Power System. The Overhead Panel Controls and Indicators Are Described As Well As The Electrical Synoptic.

[@user-is3jy6fn4h]

Big thanks to you, man.Subscribed.🎉.Looking forward new videos.

[@subsonicflighttraining]

Thank you!

[@RmDIrSudoSu]

God I'm glad that I've found your channel, it is a gold mine for what I'm currently working on. Thanks you.

[@subsonicflighttraining]

My pleasure...

[@lijo1812]

I’m a retired maintenance personnel. Your video refresh my memory.

[@subsonicflighttraining]

You probably knew the system a lot better than I do then. There was a time when I would dig in the maintenance manuals to find out more than what Mr Boeing wants to tell pilots…

[@4ndroidG]

Thanks again for another great video!

[@subsonicflighttraining]

You are welcome...

[@Cedarjetboy]

Fantastic Channel and very informative demonstrations to complement the reading!

[@subsonicflighttraining]

Thank you, glad you find some value in my tutorials...

[@mishmish1968]

Thanks a lot for another very wealthy video , every day i look for the notification bell , waiting for the next magnificent video. 👍💗

[@subsonicflighttraining]

Thanks mishmish, your welcome...

[@brenthendricks8182]

Once the chocks are in place you would not leave HYD 4 in AUX (Or 1 and 4 on some -400's or the -8), and usually cargo unloading or other ground handling would not take place until hydraulics have been switched off and the beacon light turned off. This is to prevent injury or damange to the aircraft from accidental or uncommanded flight control movement..

[@subsonicflighttraining]

Once the signal is given for chocks in or a call that chocks are in, #4 demand pump is turned from AUX to OFF in both the 400 and -8 by the FO. The Captain may or may not, at their discretion, release the parking brake. #1 is turned OFF in both jets as part of the shutdown procedure. It is only put to AUX, if you have it, during the before start procedure, not during shutdown. Prior to engine shutdown, the FO brings #4 to AUX, and #1, 2, and 3 to OFF. The beacon is turned OFF as part of the shutdown flow after the engines are shut down...

[@LillyDaisy]

nice work 👍 u will get more views

[@subsonicflighttraining]

Thanks E Portal, appreciate you got some value from this video.

[@harryb7591]

Love all the videos! Would you be able to do a video for the air systems ?

[@subsonicflighttraining]

Yes I can, I will put it on the list...

[@harryb7591]

@@subsonicflighttraining thank you !!

[@rcflyer6241]

Thanks for a great Electrical System Video. I did have a question : According to the AC Power | T/R | DC Bus Schematic in the video, it looks like the APU Standby Bus is powered by the Captain's Flight Instrument Transfer Bus (through AC Bus 3) but not directly by AC Bus 3. Can you confirm this? 15:45 in the video Edit: I was looking at the schematic wrong I see now that the APU stand by bus is powered by the Captains transfer bus.

[@tristantriton8115]

Any idea why the adding an additional ac power source AFTER the IRS are aligns causes synchronized problems as well as prohibits autoland unless you recycle the IRS all over again? It’s really annoying TBH. I’m guessing the synchronized problem is due to the ssb opening when you have two unlike power sources but to mess up the IRS system is crazy to me. This does not happen on the 777 tho.

[@subsonicflighttraining]

I do not remember that being an issue, is that a current thing? I have no clue why it would do that…

[@RmDIrSudoSu]

Hi excellent video as I already said, but I've a question that I don't find the answer to. What bus powered the Main4 and Main1 pumps, the Main2 and Main 3 and Center are powered by the utility bus, the Stab pumps by the Ground service bus with the main 2 aft, but I don't find anywhere what bus power the Main 4 and Main 1. Do you have any informations on that? Thank you very much for this excellent video that is extrmely detailed.

[@subsonicflighttraining]

You are right, it is hard to find. The only place you find anything about Main 1 and Main 4 Fuel Pumps Power Source is in the Fuel Section where it says each main tank contains 2 AC Powered Fuel Pumps. They are on their respective busses, so Main 1 Fuel Pumps are powered by AC 1 and Main 4 Fuel Pumps are powered by AC 4. You are welcome for the video!

[@RmDIrSudoSu]

@@subsonicflighttraining Thank you so much, I read that part of the FCOM but as they don't describe it with the numbers they didn't end up in my searches.

[@macieksoft]

Can CMC maintenance pages be accessed without full AC power using only batteries and standby power? When ground crew turns off APU (when they no longer need ground service bus), how do they know when APU shuts down (when the cooldown cycle finishes, APU turns off and door closes) so they can turn off battery switch?

[@subsonicflighttraining]

No, the CMC pages need AC Power to be accessed usually by the Center CDU by maintenance. When the APU is turned off, the fire detection is provided by the APU Battery Bus, which is powered as long as you keep the Battery Switch ON. The way you know the APU has fully shut down is by time, you allow and time for 2 minutes when you turn the APU off to account for the cool down time, plus door closing, etc.

[@michaellochner9145]

hello again, looking through these videos again and I had a scenario question. If you're on a CATIII approach and you are below 1,500', so all but AC 4 is isolated, what happens if AC BUS 4 fails in that mode? I know that that AC BUS 4 is designated as the bus which can help power other busses in case of a fault, but at that point, what happens to the system? The AC BUS 4 is also used to power the Sync BUS so, is it just not powered?? I cannot imagine that as being the case so what powers the SYNC BUS? The other buses? or are just left stuck fully isolated until you exit that mode? Sorry if you mentioned it in the video and I just missed it but this was a question I have been thinking about since my last CATIII Autoland... Thank you as always!!

[@subsonicflighttraining]

If you are in LAND 3 and AC Bus 4 fails, AC and DC Buses 1, 2, and 3 would remain isolated from the sync bus to maintain 3 independent power sources for Autoland. The Sync bus would not be powered. If there is another failure of 1, 2, or 3, the electrical system would be unable to maintain a configuration for full autoland bus isolation for LAND 3. The Sync Bus would be re-powered and LAND 3 would change to LAND 2 if below 1500 RA and above 200 RA. If you are below 200 RA, then LAND 3 would remain shown and the jet would Autoland just fine. Of course if you get LAND 2 on a CAT IIIB approach, then your ops specs for CAT III Operations would determine your further actions from that point...

[@michaellochner9145]

@@subsonicflighttraining fantastic, even me and the instructors were discussing this since there's very little literature on that exact scenario. Thanks for the info as always!

[@drisschafnaj7090]

What program you work on it (flight simulator for example)

[@subsonicflighttraining]

The jet is PMDG 747-400 and 747-8, the platform is Lockheed Prepar 3D (P3D v4) Professional Edition.