Boeing 747 cockpit irreversible actions 

Also I dont know if the 747 has a fuel dump valve, but if it does dumping fuel is probably irreversible too.

My Dad worked at the plant that made the inertial navigation system for the 747 (also for the Apollo missions). He brought home a pilot's guide for it, and once I had read it, I was confident that I could navigate a 747 to any place that I had coordinates for. Someone else would have had to take off and land it, though. 😁 It pleases me to see that they are still in use, even though we now have GPS.

Been meaning to learn this function so i can finally take my family on a holiday in my 747.

Would you consider discharging fire bottles another irreversible action or no?

It's always nice to see avionics being talked about on youtube. For those interested I have some more in depth information regarding the IRS / INS systems of that era. For the B747s , they were initially fitted with mechanical gyros (1970s/1980s). Hence the align mode. This generally took around 15 minutes to align on the ground. During initial start up the current Lat and Long of the aircraft would be inserted into the nav system so that the computer had a known starting point. Aircraft had to remain perfectly still while this alignment was taking place. Even passenger loading would often cause an error code to come come up stating excess movement of the aircraft was detected. Once the alignment had finished the switch could then be placed to Nav mode, which would mean that the onboard IRS computer was now active. Now the aircraft can move freely and the computer can calculate distance covered by the outputs of the IRS accelerometers (usually 3 fitted - 1 per axis of the aircraft). The pilot can then load waypoints and the autopilot can then use this information to fly the aircraft to that position. So in Nav mode the computer calculates where the plane is on the ground and feed that info to the auto pilot. the system also feed attitude info from the synchros in the gimbals, and these are fed to the attitude indicators. Now if the pilot selects ATT mode in flight, this then shuts down the computer within the IRS and hence no positional information is no longer available. But the mechanical gyros keep running within the gimbal thus still out putting aircraft attitude info to the attitude indicators. Once in attitude mode the only way to go back to the Nav mode is to land the plane and keep the aircraft stationary for a 15 minute period. Now with more modern 1990s IRS systems fitted with laser gyroscopes and fed with GPS info, if ATT mode was selected, and the pilot wished to go back to NAV mode the aircraft would have to fly straight and level for a period of time whilst the nav computer recalculated situational info fed to it by the GPS.

I can see why you're a teacher. You have a pleasant voice and you explain things really clearly.

When you said "you could in flight I suppose" for the masks, why was my first thought to pitch down as hard as possible to throw them all back up into the bays

Captain Obet is the pilot every co-pilot whish for!

My dad used to work for Cathay Pacific as a captain on the A340. His dream was to fly the B747. Alas, because of the uncontrollable variables that come with life, he hasn't been able to do so, yet. Probably never will. The beast is a relic and not financially viable for any airline company at this point. I still hope that he'll one day get to fulfill his dream.

Thanks captain for sharing this!! I found the generator disconnect is irreversible while playing FSX/PMDG, it was so confusing to me back then. This video finally confirmed by doubt, after 15 yrs haha

I hope the O2 mask compartment design has improved since I retired. Working against gravity and trying to get three or four masks properly folded and secured in place and then latching the door closed was a miserable but critical task to perform--over and over and over again. As far as the NAV and ATT modes of the IRS, I was once a passenger on a Northwest Airlines B37-300 leaving Salt Lake City en route to Jackson Hole Airport at night. About the time the airplane settled into cruise flight, the captain came on the PA and advised that we would be returning to SLC because "two of the compass systems don't work." My first thought was, Oh no, you did not do that. Sure enough, we landed back at SLC and a mechanic came onboard at the gate. I could see him manipulating switches on the overhead panel, and about ten minutes later he signed off the logbook and we departed for a second time. The crew had run their checklists and taken off with the IRUs in ATT mode.

Thank you, Captain. As a desktop pilot, now I (like others here) know why that crazy DRIVE DISC refuses to turn on when I fidget around with it while in flight :) Also, full disclosure --> ah!!!! that was "disconnect, not disc as in disc drive... :D

"Controlled flight into ground" is likely to be irreversible as well.

As a Boeing mechanic of twenty years, there is one important thing he didn't address on the IRUs. If you don't align the IRUs before you turn them to off position an annoying alarm will sound for five minutes when the power is shut off. That's also why typically when pilots land the plane unless it's part of the checklist they leave them on NAV and let maintenance align them before turning aircraft power off. The IRS system can only be aligned before flight. Which is what makes the other switch positions irreversible while in flight.

Thank you for sharing the 747s.. I do miss flying on the 747-400s from Asia for many years...

Nice brief lessons Captain! That was cool to learn! Keep teaching us some more functions in that instrument panel. Thanks

Thanks for sharing the in depth knowledge behind why you would end up in a situation where these would be necessary and not just saying “these aren’t reversible.” You’ve earned yourself another sub, I look forward to seeing more of your content!

It's also worth keeping in mind that certain systems (RAT, O2 masks) are automatically deployed if the aircraft registers the conditions that require their use (i.e. decompression, loss of electrics/hydraulics, etc), so for a pilot to have to manually activate them, something must be quite wrong.

Awesome video very interesting. One question, when you disconnect the gen drives I’m not sure if I understood correctly, can you not reconnect them on the ground as well? What would one have to do to reconnect them?

Hello from the Philippines Captain Obet! Love your videos! I hope to become a pilot someday and these big aircraft like the 747 are absolutely dream planes! It would be really cool if you could make a video about Kai Tak airport since I was not yet born when this airport was active and I am so interested about it! Thank you so much! Safe skies!!

That was the best aviation video I’ve EVER SEEN! I didn’t even know all this! Thankyou so much for this video! Can you make other Irreversible videos like this?

Thats actually super cool. Its a mechanical engineers solution to "Are you sure?". Which is something commonly seen in software.

Pilots are so cool, when I was flying Strat Air to Afghanistan the German Navigator basically gave me a class and the FA's were so polite.

Fascinating, thank you very much! A friend of mine is doing his 747-8 training. I'm afraid all my trainers retired with bad nerves after my PPL lessons :-)

What a wonderful video!! Thank you Captain! I am building my sim with all real components from the tear down 744 G-BNLS in ZGGG, very close to HK. And I did enjoy to study to control every single switch. I just finished interfacing the IRS panel last month. And I know why they the lock on the these three switches. Thank you again!!

Great video! I hope to see more! Thanks for sharing!

Thanks so much for showing these! I'm going to see how they react on the aerowinx 744 sim now!

This is awesome dude thanks so much for uploading. Love seeing all these fun little things about these jets. Now I gotta learn to fly them haha

Thanks for writing it all in the description too!

Finally! Thank you, wasnt sure how to fix that during my flight, so I just pulled to the side of the flight corridor, put my hazards on and parachuted down.

Very cool. I have always been fascinated by the complexity of all jet aircraft.

Great video. Informal content with a nice outro. Liked it very much

Thank you captain. So much knowledge from you.

This seems super intriguing. I subbed!

Your content is awesome 👌 👏 keep it coming!

I actually did the "GEN DRIVE DISC" once in a real flight, and the QRH clearly stated "action is irreversible", me and my copilot had to be very sure we are disconnecting the correct one, but it's actually a very rare occurrence in my 7+ years flying the 744s. And I did not know the 747-8s have the RAT, is it consider a standard equipment in 747-8s?

This captain gives me a new insight on how boeing planes work. I bet this is the same with 737. I'm a flight simmer who's trying to learn to fly. This guy explains thoroughly. I love it.

thanks for the wisdom captain, would love to have a go in that simulator =D

Very interesting! Thank you for showing this to us!

Thanks a lot for another highly interesting snippet! Later! 👍

Very interesting video. Thank you!

Very informative. Thank you Sir.

The RU-vid algorithm works in dark and mysterious ways to have this recommended in my feed. I have nothing to do with piloting, but it was still fun to watch though.

Love that some of those switches takes conscious effort to lift or unguard before pressing the button.

Fantastic video. Happy Landings, my good sir.

Thanks, very insightful 👍

dude played with the same 3 knobs for 3 solid minutes, and i sat there watching every bit 🤦‍♂😂

This was really great, interesting to see and all make sense.

I was about to ask about the RAT.. thanks for the vid..

Thanks, I’ll keep this info in mind the next time I fly with spirit airlines

Really interesting, thank you!

Well done Captain!

No idea what any of this does, but at least I know it's irreversible. Awesome video! :)

Nice.Thank you sir.

Ah yes, the 747. The plane that can carry 1/4 of a discord moderator

Thank you :)

Thank you for teaching me how to use a 747. I'll try it on my next travel.

Thank you, Captain.

It would seem to me that any switch that is irreversible should have an extra visual device such as a yellow circle or some other signal around it.

Very interesting video! thank you for sharing :)

This is cool! A real look at the lesser known buttons and switches that will blow up your plane.

nice to have these straight up tutorials on how to hijack planes

Thanks, never heard of this before.

Great video!

Fascinating..!

Loved the bungee metaphor! ROFL

passengers in the back: "the fuck is going on up there?"

I enjoy this mans accent and way of speaking !

good to know, thanks for the information

That's cool! I was actually wondering what happens if one would accidentally switch the IRS knobs in-flight. Basically, you can't. Thanks for answering a query I had in the back of my head!

Thanks cap!

Subscribed!

Your voice is very soothing.

Good to know, next time on my Vacation, ill tell this to the pilots

Does the RAT extend automatically in an electrical emergency, or is that just an Airbus thing? I’m also guessing the IRS is irreversible because the system needs to be on the ground to align and calibrate itself, which obviously cannot be performed in flight.

Additionally, make sure the engine power is set equal or higher than idle power before press IDG DISC switch, specially the action need to be made on ground. Or the IDG will permanently be damaged, even destroy the gearbox.

Farting in the cockpit is irreversible also, but usually the co-pilot will get the blame, even if it was the captain.😂 I watch the channel "74gear" the owner of that channel is Kelsey, he is a 747 pilot for Atlas airlines and he always tells weird or funny stories that happens and he said usually when there is 3 of them in the cockpit and someone farts the lowest ranking crew member always gets the blame.😂

Very well explained. I just prefer the Boeing logic. I think, "Oh, yeah, that makes sense. Very good physically UI design.

I have no affiliation with 747s or aviation in general, I dont know why I'm here but God damn is this mesmerising

That's it, thank you 😀

Now I know which switches to tell the little kid to push when the captain lets him see what the cockpit looks like!

"Hello folks this is your pilot speaking. We are going to need to make a quick stop in this farmers field... I went into ATT mode..." 🤣🤣🤣

Awesome video! How much does one of those full simulator rigs cost your company?

So nice looking switches. Could press them all day

Here I am, not even a pilot, watching this because I thought, “I may need to know this one day.”

Thanks, youtube algorithm. Very cool

interesting, but an explanation on what the different this are and what they do would be nice

Cool

I just have one question left, how do you go from NAV to ATT?

What’s the STORM light for, and what does it look like in flight when it’s activated?

What about the “Ditch Switch” that closes the pressurization ram doors for a water landing?

Am I right in saying ATT mode would only ever be used if the system was faulty in some way? Excellent video!

I would say fire suppression is another irreversible one. For both APU and the engines. Once you pull that handle, that engine is off until you're back on the ground.

I believe putting the INS to Att during IMC conditions is what caused Adam Air 574 to crash, a B737-400 classic aircraft, which is why Boeing implemented that in it's newer aircraft

Good designs

Nice. I have the same model but I don’t have the user manual. I’ve always wondered what those switches and knobs were for

is there a manual release for the ram air turbine, or is the switch and mechamism mechanical/gravity powered?

will remember this for next time im flying a boeing 747

This will help a lot in the same way that knowing how to get out of quicksand will.

I know 0 about any cockpit controls, but an irreversible NAV to ATT switch seems like a bad idea. Whats the reason for it?