@@vladimirassalukas6726 for sure, not only would the bottles need replacing, the SQUIBs would as well. I imagine those explosive bolts to be very difficult to replace.
Many airplanes have two stages on the fire handle. The first one will disconnect all fuel, hydraulics, oil, and bleed air, etc. The second one is the fire bottle. In some airplanes, at least the one I fly (ERJ145) pulling a fire handle and isolating the engine is reversible. The valves closed by pulling the fire handle can be re-opened by simply putting the handle back where it was. Rotating it left or right will discharge a fire bottle into the engine. Once you discharge a fire bottle though, that’s it. You done did it. Can’t un-do it. I can’t think of a reason why I’d pull a fire handle and decide to put it back though. The two of us would triple check that we’re about to pull the correct one in a real emergency. We train it all the time in the simulators.
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.
New INS systems, at least in military aircraft, are coupled to GPS for constantly updating alignment. In the military, or at least the Air Force, they call it EGI. You can even shut down the INS completely midflight and realign it entirely using GPS signals and standby instruments.
I used to repair, test and calibrate the Delco Inertial Navigation Systems for a major airline many years ago. I can even still remember all of the part numbers ! (7883450-041) etc. The latest 747 has IRS systems (rather than INS). The difference is an INS can navigate from waypoint to waypoint, and provides the current a/c position and attitude information to the flight instruments - whereas an IRS system, whilst also providing the current a/c position, can not navigate as such and has to be coupled to an FMS system.
@@SuperSarah1954 Gotta wonder why they made the switch. "This one does this, this, and this. The shiny new one does this and this." My view is, "If it ain't broke.." Those Carousel IVs got the planes to their destinations quite reliably. No wonder air travel is so expensive. They're fixing things that "ain't broke".
@@SuperSarah1954 correct but the IRS receives constant updates from GPS too. Thank you for your info insightful- and you remember the part numbers-wow!
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.
@Elias HeronBons The whole concept of an INS is that they operate without any external inputs. The 70s and 80s systems would run for hours and still remain very accurate. Wrt your earth rotation question, this is calculated at turn on when the operator inputs their start position (lat/long). From this the onboard computer has preprogrammed procession rates for latitude. At initial turn on the onboard accelerometers provide a rough level before the gyroscopes run up. Once up to speed precession rates are applied with respect to a calibration that is done in the workshop, as each gyro has different characteristics. These INU calibrations usually took a few days to complete in the workshop (that was my job for 30 years). From memory accuracy of a mechanical system was about a 10 mile error after a 2 hour flight. For laser based gyroscopic systems this came down to around 2 miles. Reliability of a mechanical gyro system was 1000 hours, and a laser system 5000 hours, and the new fibre optic gyro system around 15000 hours. Standard maintenance fee to repair an INS was US$10000 for each system. usually 3 fitted to commercial airliners.
All correct- I operated the INS systems on the B707 which were Litton 72 systems with mechanical gyros. We often got ‘excessive movement’ while loading passengers sometimes although the systems got better. At flight dispatch part of the package was that we would be given NAV/LOG sheets which had the latitude and longitude of all the waypoints on the filed flight plan route. During pre-flight, one of us pilots had to insert up to 9 waypoints. As you approached the 8th waypoint in flight, you would insert the next. I used to fly the 10 hour flight from Harare to London and also to Frankfurt. Through the flight we were updating waypoints because there were lots on the sector. That was the Litton 72’s. Then I flew the B747-100 and 200 classics which had the Litton 92 systems. These could load up to 99 waypoints and were this much better and most regional routes and some long haul were covered. The INS systems also didn’t have GPS updating so would develop some positional errors in flight so we would update the position by flying directly overhead a VOR usually and update to that position 😀
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?
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
You may get some help from the unstrapped passengers - who would be "floating" against the ceiling and so able to follow some simple commands to re-stow the masks. You might want to keep an eye on the altimeter though.
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.
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.
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
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!
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.
I did address it in a sense if you read my narrative and also some of my replies- but what you say is correct. The subject matter was that the actions I was showing were irreversible as the Boeing checklist says- not why we let the mechanics turn them off or the alarm system it has etc. I can do a separate video on that aspect
I think I can add to that if my memory serves me right (over 30 years ago now). If the MSU (Mode Select Unit) is at STBY or ALIGN, then the INS will shut down if the electrical power is removed from the a/c. If the MSU is selected to 'NAV', then on loss of electrical power the INS will be powered up from a separate INS battery unit - and a horn located in the Nose Gear Wheel Well will sound.The way the system was set up is that if electrical power was lost briefly during a flight, the the INS will remained powered - and if during maintenance the power was disconnected with the INS still switched on, then that warning horn would operate the maintenance crew (to save depleting the INS battery).
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!!
@@pilot_obetsurely welcome!!🎉🎉 And I just updated my sim with a real part of the IRS panel. It is exactly the logic you said, from NAV to ATT is locked and a pull is needed. But it is very old panel, from NAV to Align or OFF is no locked any more. I believe the switches itself is broken. Haha Please come to my sim. Would like to meet you soon , my man. Haha.
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.
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?
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!!
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 :-)
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?
@@rael5469 no idea why. but the faa has been a bit uncooperative recently so maybe they just wanted to be ahead of the curve of any new regulation they could spring on them. like whats going on with the max10 now.
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.
On the plane i used to work on, the physical guards for anything like this had a strand of weak safety wire securing it in a very specific way that it added a bit of effort to even flip up the physical guards for things like this. Both tactile and visual feedback (didn't have an INS so that one didn't apply)
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.
@@alexspeedpro2254 I don’t think most would consider Boeing safer anymore. Most people would now consider Airbus safer after the myriad safety problems with the 787 and 737 max
As a matter of fact, the RAT does extend automatically in the event of failure of 3 or more engines. The RAT on the B747-8 is there to provide emergency hydraulic power to system 3 for flight controls. There is no electrical output unlike other types of aircraft 😊
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.
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!
The UA-cam 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.
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.
WHen would you ever need to do an in flight alignment? It makes sense for fighter aircraft if they need to deploy with short notice. But for a commercial airline?
Very interesting video, Captain Obet! I'm wondering, if you were to fly a route with GPS inhibited- that is, relying purely on the IRS, how much would you expect the IRS position to drift? Lets say a route from VHHH to EGLL, what would your ANP be when reaching the London area? I'm trying to imagine what it was like for Pilots relying purely on IRS navigation in the 1990s, if it would've been possible to make a RNAV approach accurately after such a long route. Maybe the ILS is down due to a power cut 😄
Novo: As an old patrol plane navigator using the Litton 211 inertials in the 80's, I would not attempt any instrument approach using only inertial position. They just aren't that accurate.
@@novo6462 hi- thanks for question. On the Litton 72 systems that I operated for years on the B707, they were not bad. After a 10 hour flight, you would be maybe 1 or 2 miles out - but that could be enough to hit a hill if you attempted an RNAV approach so I wouldn’t do it. We used to perform position updates in flight regularly on long haul by flying as accurately as possible over a VOR. As the aircraft overflew directly overhead( in the cone of confusion), we would ‘Update position’ to the coordinates of that VOR 😀
Great video! What about the two fire extinguishers systems for every one of the engines? To my knowledge, once they are activated, the engines cannot be restarted again.
Correct- I was focusing mainly on the non obvious items. It’s like saying if the wing falls off- that’s is irreversible too but for the sake of brevity I didn’t mention the obvious things. But correct- the fire extinguishers are one shot into the engine that’s it.
@@pilot_obet OK 🛫 ✈ *enters racetrack, sips 🥂 and eagerly awaits next video* I guess opening the escape hatch and exiting to the ground on the inertial reel escape rope might also qualify as irreversible... 😉
@@pilot_obet I didn't think I'd said that I'd climb into one... Just that escaping via the escape rope would be 'irreversible'...
2 роки тому
Presumably gravity gear extension is irreversible as well? As I understand it, you're disconnecting the gear from the hydraulics, so you have nothing to pull it back up?
No, that’s not true. If you apply hydraulic power you can cycle the gear handle and raise the gear again. But that would never be used in real life. Once the alternate extend has been used, you’re landing the airplane.
So, do you only disconnect the generator drive if you know the engine cannot be saved/restarted? i.e a severe engine fire or fuel exhaustion? Because don’t you need the generator to keep the engine running? Thanks in advance
I am not a 747 pilot. But in most transports (I believe including in the 747), in a fire or a severe engine damage situation you are required to activate the engine fire handles. When this handle operated, it automatically disconnects everything that is run by the engine including the electrical generators, hydraulic pumps. And most importantly, it shuts off the low pressure fuel valve.
@@ImperrfectStranger The LP fuel valve is another name for spar fuel valve. LP fuel valve is the name used by Airbus. It is closes the connection between the fuel tank and the engine.
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.😂
Interesting. I would have guessed that if you managed to get the gear up you would be able to pull it again, but you probably aren't getting the gear up because you pull that when the hydraulics don't work.
Not completely true... The only reason the checklist would have you alternate extend would be due to loss of hydraulics. However, if hydraulics are available; the gear can be retracted again. The alternate extend just releases the uplocks to let the gear fall by gravity, nothing more.
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.
@@pilot_obet For real? That's crazy! I thought it swamped the engine. Do you have to restart it before the core stops moving or can you do a restart from zero?
@@jumperIndustries Pulling the switch only trips the electrical connections and closes valves for fuel, oil and bleed air, so it isolates the engine before the extinguisher can be activated. Pushing the handle back in before activating the squibs reverses that isolation and you can restart the engine. But once you introduce the extinguisher, most engines are done.
![1987 Classic B747-200F wonderful Cockpit Landing into Frankfurt! [AIRCLIPS]](http://i.ytimg.com/vi/n2KI21W2-30/mqdefault.jpg)
Also I dont know if the 747 has a fuel dump valve, but if it does dumping fuel is probably irreversible too.
We do- I’ve done a video about it two weeks ago- check it out
Nah just roll inverted and pull back until level again to catch the fuel you just dumped
@@ElBantosClips this guy aviates
@@ccllvn That's a really original play on the "this guy f*cks" phrase, lol
@@ccllvn yee
Would you consider discharging fire bottles another irreversible action or no?
I would indeed but that is expected for a fire/ emergency compared to normal operations
That would be the last irreversible action in his/her career in aviation, if done “mistakenly” 😆
@@vladimirassalukas6726 for sure, not only would the bottles need replacing, the SQUIBs would as well. I imagine those explosive bolts to be very difficult to replace.
Many airplanes have two stages on the fire handle. The first one will disconnect all fuel, hydraulics, oil, and bleed air, etc. The second one is the fire bottle.
In some airplanes, at least the one I fly (ERJ145) pulling a fire handle and isolating the engine is reversible. The valves closed by pulling the fire handle can be re-opened by simply putting the handle back where it was. Rotating it left or right will discharge a fire bottle into the engine.
Once you discharge a fire bottle though, that’s it. You done did it. Can’t un-do it.
I can’t think of a reason why I’d pull a fire handle and decide to put it back though. The two of us would triple check that we’re about to pull the correct one in a real emergency. We train it all the time in the simulators.
@@byronhenry6518 I thought you can still restart the engines on a maddog after discharging the fire bottles?
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.
New INS systems, at least in military aircraft, are coupled to GPS for constantly updating alignment. In the military, or at least the Air Force, they call it EGI. You can even shut down the INS completely midflight and realign it entirely using GPS signals and standby instruments.
The IRS on board the B747 is constantly updated by GPS coupling
I used to repair, test and calibrate the Delco Inertial Navigation Systems for a major airline many years ago. I can even still remember all of the part numbers ! (7883450-041) etc. The latest 747 has IRS systems (rather than INS). The difference is an INS can navigate from waypoint to waypoint, and provides the current a/c position and attitude information to the flight instruments - whereas an IRS system, whilst also providing the current a/c position, can not navigate as such and has to be coupled to an FMS system.
@@SuperSarah1954 Gotta wonder why they made the switch. "This one does this, this, and this. The shiny new one does this and this."
My view is, "If it ain't broke.." Those Carousel IVs got the planes to their destinations quite reliably. No wonder air travel is so expensive. They're fixing things that "ain't broke".
@@SuperSarah1954 correct but the IRS receives constant updates from GPS too. Thank you for your info insightful- and you remember the part numbers-wow!
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.
Very cool, Sir. Thanks for all that info.
@Elias HeronBons Thats the actual magic of the IRU/IRS no external signals are required:)
@Elias HeronBons The whole concept of an INS is that they operate without any external inputs. The 70s and 80s systems would run for hours and still remain very accurate. Wrt your earth rotation question, this is calculated at turn on when the operator inputs their start position (lat/long). From this the onboard computer has preprogrammed procession rates for latitude. At initial turn on the onboard accelerometers provide a rough level before the gyroscopes run up. Once up to speed precession rates are applied with respect to a calibration that is done in the workshop, as each gyro has different characteristics. These INU calibrations usually took a few days to complete in the workshop (that was my job for 30 years). From memory accuracy of a mechanical system was about a 10 mile error after a 2 hour flight. For laser based gyroscopic systems this came down to around 2 miles. Reliability of a mechanical gyro system was 1000 hours, and a laser system 5000 hours, and the new fibre optic gyro system around 15000 hours. Standard maintenance fee to repair an INS was US$10000 for each system. usually 3 fitted to commercial airliners.
All correct- I operated the INS systems on the B707 which were Litton 72 systems with mechanical gyros. We often got ‘excessive movement’ while loading passengers sometimes although the systems got better. At flight dispatch part of the package was that we would be given NAV/LOG sheets which had the latitude and longitude of all the waypoints on the filed flight plan route. During pre-flight, one of us pilots had to insert up to 9 waypoints. As you approached the 8th waypoint in flight, you would insert the next. I used to fly the 10 hour flight from Harare to London and also to Frankfurt. Through the flight we were updating waypoints because there were lots on the sector. That was the Litton 72’s. Then I flew the B747-100 and 200 classics which had the Litton 92 systems. These could load up to 99 waypoints and were this much better and most regional routes and some long haul were covered. The INS systems also didn’t have GPS updating so would develop some positional errors in flight so we would update the position by flying directly overhead a VOR usually and update to that position 😀
Why shutdown the computer tho
Been meaning to learn this function so i can finally take my family on a holiday in my 747.
I can see why you're a teacher. You have a pleasant voice and you explain things really clearly.
Thank you
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?
Yes you can reconnect them on ground but not from the flight deck. It is done by maintenance at the engine itself
@@pilot_obet oh I see! Thank you very much Obet :)
@@pilot_obet So it's a physical disconnect of the shaft that rotates them? Or just electrical?
@@nezu_cc Pretty sure it physically disconnects it from the drive not electrically but I am no pilot so I am not sure.
@@nezu_cc Yes, the shafts are separated physically, they have to be manually re-connected on the ground.
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
Why does this make sense in my mind
You may get some help from the unstrapped passengers - who would be "floating" against the ceiling and so able to follow some simple commands to re-stow the masks. You might want to keep an eye on the altimeter though.
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
Captain Obet is the pilot every co-pilot whish for!
Totally agree 👍
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.
Ha- a bit embarrassing 😳
Thanks for that story😊
Oof
"I hope the O2 mask compartment design has improved since I retired."
I hate to be the one to tell you this, but
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.
But hey, he did fly the 340, a dream most people couldn’t hope to achieve 🤷♂️
@@ON-O you're not wrong!
Thank you for sharing the 747s.. I do miss flying on the 747-400s from Asia for many years...
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
Yes, that's what he said multiple times.
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!
Cheers
Nice brief lessons Captain! That was cool to learn! Keep teaching us some more functions in that instrument panel. Thanks
Thanks for writing it all in the description too!
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.
I did address it in a sense if you read my narrative and also some of my replies- but what you say is correct. The subject matter was that the actions I was showing were irreversible as the Boeing checklist says- not why we let the mechanics turn them off or the alarm system it has etc. I can do a separate video on that aspect
Thanks for the good response from you- appreciated and sharing your good knowledge
I think I can add to that if my memory serves me right (over 30 years ago now). If the MSU (Mode Select Unit) is at STBY or ALIGN, then the INS will shut down if the electrical power is removed from the a/c. If the MSU is selected to 'NAV', then on loss of electrical power the INS will be powered up from a separate INS battery unit - and a horn located in the Nose Gear Wheel Well will sound.The way the system was set up is that if electrical power was lost briefly during a flight, the the INS will remained powered - and if during maintenance the power was disconnected with the INS still switched on, then that warning horn would operate the maintenance crew (to save depleting the INS battery).
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!!
Now I know why there are locks on these three switches.
Cheers- I’d love to come and see your built B747 one day
Cool. Isn't there also the fire extinguishers controls for engines that's an irreversible switch ?
@@pilot_obetsurely welcome!!🎉🎉
And I just updated my sim with a real part of the IRS panel. It is exactly the logic you said, from NAV to ATT is locked and a pull is needed. But it is very old panel, from NAV to Align or OFF is no locked any more. I believe the switches itself is broken. Haha
Please come to my sim. Would like to meet you soon , my man. Haha.
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.
the design is that if the pilot feels She or He wants to pre-empt the system they can.
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?
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!!
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 :-)
Ha ha- that made me laugh. Go on and pursue your ambition!😃
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.
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?
its the other way around is what I've heard the 747-8 does have one no matter what. but the -400 and earlier dont.
@@nick4506 Why would they need a RAT with four engines? Seems like overkill.
@@rael5469 no idea why. but the faa has been a bit uncooperative recently so maybe they just wanted to be ahead of the curve of any new regulation they could spring on them. like whats going on with the max10 now.
@@nick4506 Thanks Nick. Interesting question though.
@@rael5469 i would guess in case of fuel exhaustion, the RAT would come in handy
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.
"Controlled flight into ground" is likely to be irreversible as well.
Have you tested that tho? Everything in aviation requires rigorous testing beforehand so once you've gone and proven it I'll believe it ,-,
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.
It is all on the checklist with cautions
On the plane i used to work on, the physical guards for anything like this had a strand of weak safety wire securing it in a very specific way that it added a bit of effort to even flip up the physical guards for things like this. Both tactile and visual feedback (didn't have an INS so that one didn't apply)
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.
It's an airbus thing, boeing will never pursue actions without the pilot's permission, main reason they are considered safer.
@@alexspeedpro2254 Except when it pushes the nose of the plane down without any warning. That is acceptable for Boeing.
@@alexspeedpro2254 I don’t think most would consider Boeing safer anymore. Most people would now consider Airbus safer after the myriad safety problems with the 787 and 737 max
As a matter of fact, the RAT does extend automatically in the event of failure of 3 or more engines. The RAT on the B747-8 is there to provide emergency hydraulic power to system 3 for flight controls. There is no electrical output unlike other types of aircraft 😊
@@alexspeedpro2254 see my reply
Great video. Informal content with a nice outro. Liked it very much
Thank you for teaching me how to use a 747. I'll try it on my next travel.
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.
Cheers
passengers in the back: "the fuck is going on up there?"
nice to have these straight up tutorials on how to hijack planes
Very cool. I have always been fascinated by the complexity of all jet aircraft.
Thanks so much for showing these! I'm going to see how they react on the aerowinx 744 sim now!
Love that some of those switches takes conscious effort to lift or unguard before pressing the button.
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!
Ditto
I enjoy this mans accent and way of speaking !
Your voice is very soothing.
This seems super intriguing. I subbed!
What about the “Ditch Switch” that closes the pressurization ram doors for a water landing?
I’ll talk about it soon in a video
The UA-cam 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.
Awesome video! How much does one of those full simulator rigs cost your company?
Your content is awesome 👌 👏 keep it coming!
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, I’ll keep this info in mind the next time I fly with spirit airlines
I was about to ask about the RAT.. thanks for the vid..
I just have one question left, how do you go from NAV to ATT?
Fantastic video. Happy Landings, my good sir.
interesting, but an explanation on what the different this are and what they do would be nice
Thank you, Captain.
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.
I'd love to see the mechanism behind the lock-out of the first switch.
Ah yes, the 747. The plane that can carry 1/4 of a discord moderator
Loved the bungee metaphor! ROFL
Good to know, next time on my Vacation, ill tell this to the pilots
I have no affiliation with 747s or aviation in general, I dont know why I'm here but God damn is this mesmerising
WHen would you ever need to do an in flight alignment? It makes sense for fighter aircraft if they need to deploy with short notice. But for a commercial airline?
About the RAT, what happones if it's down and the wheels don't work?
Also great video!
Edit: fixed punctuation.
The wheels can go down with gravity. If for some insane miracle they don't, trust me the least of your problems is the RAT.
Then you would likely damage it on landing as it hangs down on right wing area
Hi captain!
Could you please post some videos landing into Mumbai pls?
Very interesting video, Captain Obet! I'm wondering, if you were to fly a route with GPS inhibited- that is, relying purely on the IRS, how much would you expect the IRS position to drift?
Lets say a route from VHHH to EGLL, what would your ANP be when reaching the London area?
I'm trying to imagine what it was like for Pilots relying purely on IRS navigation in the 1990s, if it would've been possible to make a RNAV approach accurately after such a long route. Maybe the ILS is down due to a power cut 😄
Novo: As an old patrol plane navigator using the Litton 211 inertials in the 80's, I would not attempt any instrument approach using only inertial position. They just aren't that accurate.
@@KB4QAA Thanks very much :D I appreciate getting a response from an experienced airman like yourself 👍 I've got a PPL with about 160 hours.
@@novo6462 Happy flying, even if from an armchair, now! :)
@@novo6462 hi- thanks for question. On the Litton 72 systems that I operated for years on the B707, they were not bad. After a 10 hour flight, you would be maybe 1 or 2 miles out - but that could be enough to hit a hill if you attempted an RNAV approach so I wouldn’t do it. We used to perform position updates in flight regularly on long haul by flying as accurately as possible over a VOR. As the aircraft overflew directly overhead( in the cone of confusion), we would ‘Update position’ to the coordinates of that VOR 😀
pre-GPS, weren't INS for navigating across oceans with reasonable confidence of hitting a VOR or NDB on the other side?
Subscribed!
Thanks
would you consider fuel jettisons irriversible actions in the sense that once you pushed them, you have lost the fuel that has been jettisoned out?
Really interesting, thank you!
Thanks a lot for another highly interesting snippet! Later! 👍
Thanks, very insightful 👍
Great video! What about the two fire extinguishers systems for every one of the engines? To my knowledge, once they are activated, the engines cannot be restarted again.
Correct- I was focusing mainly on the non obvious items. It’s like saying if the wing falls off- that’s is irreversible too but for the sake of brevity I didn’t mention the obvious things. But correct- the fire extinguishers are one shot into the engine that’s it.
Very informative. Thank you Sir.
I thought emergency gear extension is also irreversible? Is is on the 73s, so I'm assuming its also irreversible on the 74s...?
Read my notes that came with the video…
@@pilot_obet OK 🛫 ✈ *enters racetrack, sips 🥂 and eagerly awaits next video*
I guess opening the escape hatch and exiting to the ground on the inertial reel escape rope might also qualify as irreversible... 😉
@@roscozone8092 why would you want to climb into a burning aircraft if you got out in an emergency?
@@pilot_obet I didn't think I'd said that I'd climb into one... Just that escaping via the escape rope would be 'irreversible'...
Presumably gravity gear extension is irreversible as well? As I understand it, you're disconnecting the gear from the hydraulics, so you have nothing to pull it back up?
No, that’s not true. If you apply hydraulic power you can cycle the gear handle and raise the gear again. But that would never be used in real life. Once the alternate extend has been used, you’re landing the airplane.
Thanks, never heard of this before.
What’s the STORM light for, and what does it look like in flight when it’s activated?
So, do you only disconnect the generator drive if you know the engine cannot be saved/restarted? i.e a severe engine fire or fuel exhaustion? Because don’t you need the generator to keep the engine running? Thanks in advance
If the engine has severe damage- it may be an idea to disconnect the generator because it’s spinning and can cause overheating or more damage etc
I am not a 747 pilot. But in most transports (I believe including in the 747), in a fire or a severe engine damage situation you are required to activate the engine fire handles. When this handle operated, it automatically disconnects everything that is run by the engine including the electrical generators, hydraulic pumps. And most importantly, it shuts off the low pressure fuel valve.
@@ImperrfectStranger The LP fuel valve is another name for spar fuel valve. LP fuel valve is the name used by Airbus. It is closes the connection between the fuel tank and the engine.
I’ll do a video on severe engine damage in the simulator and all will be clear😊
@@pilot_obet Ok, thanks!
This is cool! A real look at the lesser known buttons and switches that will blow up your plane.
So its basically to prevent you from accidentally turning it too far when going to nav.
Correct
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
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.😂
just open the window, it's fine
@@RoamingAdhocrat Shouldn't be an issue
@@creative0001 just remembered the 747 does not have opening flight deck windows :(
@@RoamingAdhocrat If it's bad enough I suppose we can just punch it 🤷♂
Nice.Thank you sir.
Very well explained. I just prefer the Boeing logic. I think, "Oh, yeah, that makes sense. Very good physically UI design.
Great video! I hope to see more! Thanks for sharing!
I know 0 about any cockpit controls, but an irreversible NAV to ATT switch seems like a bad idea. Whats the reason for it?
Very interesting! Thank you for showing this to us!
"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..." 🤣🤣🤣
What about engine start or off? Is there a single switch that would control that scenario?
Don't forget the manual extension thing for the landing gear because if you pull it, you can't do it again
Coming in a separate video
@@pilot_obet Ok
Interesting. I would have guessed that if you managed to get the gear up you would be able to pull it again, but you probably aren't getting the gear up because you pull that when the hydraulics don't work.
Not completely true... The only reason the checklist would have you alternate extend would be due to loss of hydraulics. However, if hydraulics are available; the gear can be retracted again. The alternate extend just releases the uplocks to let the gear fall by gravity, nothing more.
@@MercFE8235 correct- but for the operation under the rules, it is an irreversible action as in we are not permitted to do that
thanks for the wisdom captain, would love to have a go in that simulator =D
Why are align and att irreversible, why does the switch lock it from switching again?
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.
You can pull a fire switch and push it back and the engine can start!
@@pilot_obet For real? That's crazy! I thought it swamped the engine. Do you have to restart it before the core stops moving or can you do a restart from zero?
@@jumperIndustries Pulling the switch only trips the electrical connections and closes valves for fuel, oil and bleed air, so it isolates the engine before the extinguisher can be activated. Pushing the handle back in before activating the squibs reverses that isolation and you can restart the engine. But once you introduce the extinguisher, most engines are done.
Is the self-destruct switch a reversible action?
is there a manual release for the ram air turbine, or is the switch and mechamism mechanical/gravity powered?
Yes there is on overhead panel
Fascinating..!
Would dropping the landing gear during over speed be irreversible? Asking for a friend.
I would assume that engine extinguish is also an irreversible action right?
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!
good to know, thanks for the information
Here I am, not even a pilot, watching this because I thought, “I may need to know this one day.”
This is a very good video. I wonder what happens in the intertial reference unit that make it irrersible once one selects ATT mode.
Have a read of the replies and the answers are all there😀