Can Aircraft NAVIGATE by LASERS?!

this video is brought to you together with brilliant use the link in the description below for your special deal a boeing 737-800 is cruising over a dark and cloudy europe the pilots inside of the cockpit are looking down on their navigation display confident that it shows them exactly where they are to within a few meters thanks to the global positioning system the gps suddenly and without warning the gps system stops working what kind of backup navigational systems do we have and how do they work today we'll be talking about the less known but equally awesome inertial reference system irs so stay tuned [Music] hi everybody and very welcome to mentor as always i hope you're doing absolutely fantastic and welcome to a slightly more technical video guys today we're going to be focusing on how an aircraft can navigate all right how it knows where it is at any given moment even though you're flying over cloud over mountains or even oversea so in most modern aircraft like the 737 800 that i am flying we are heavily reliant on the gps the global positioning system but of course the gps position is not the only way that we have to navigate and if the gps would for some reason stop working we normally have two gps receivers in any given aircraft so even if one gives up we still have the other one but if both of them would stop working the aircraft would take one step back on to the second best navigation system that we have which is the inertial reference system the irs now the irs system is far from only a navigational system it actually gives data and information to a lot of different systems onboard the aircraft but we'll get to that in a second now in order for you to understand how pilots navigate an aircraft we need to go back to the very basics okay there are five different types of navigational systems that we use the first system is actually not a system it's basically us the pilot it's called pilotage and that is when we the pilot use maps and cues outside of the aircraft like lakes towns mountains rivers and so on and we navigate just like you would do when you're out navigating the streets using our eyes now obviously that way of navigating is not very effective if we get over our cloud layer for example or we're out of the sea so while this was the initial way that pilots were navigating when aviation started up it is something that we don't really use in commercial navigation we fly on instruments instead now that brings us to the next level of navigation which is something called dead reckoning so that reckoning was the first way that pilots were using their instrumentations in order to navigate the way that that reckoning works is that you basically have a starting position you have a heading a track and your speed and the clock so if you know your starting position and then you start timing and you keep a constant speed on a constant track for a certain number of minutes well then if you've done your pre-planning correctly you know that okay in order for me to go from this position to this church up here it should take me five minutes with this speed once i reach that position i'm going to turn right 30 degrees and i'm going to go on the new track for say 15 minutes that should bring me to this lake and then i will turn left to go on a noddly heading for 20 minutes at this speed and it should bring me to my destination so that's dead reckoning all right you're not using any kind of instrumentation to help you but you're using your speed the time your track so your magnetic compass now if you do this right it is actually remarkably accurate okay but if you're going to do this over a long distance for each leg there's going to be some slight errors when it comes to your speed maybe your track keeping is not perfect maybe you're a bit late with starting your timing so the error of your navigation is going to increase as the time builds on now the third way of navigating is celestial navigation right star navigation and this was initially used for long-haul aircraft that was flying over oceans so on the early boeing 747s for example you can still find this star navigation window where the navigational officer would be up there using his sextant and a certain star and the angle it was over the horizon the time of day they could actually go into these tables and find out only based on a couple of different stores and couple of different angles almost exactly what their latitude and longitude was now this is a very good way of navigating but it's not very precise it's not something you would want to use for example to do an approach okay it takes a bit of time but if you're sitting on a long-haul flight over an ocean you have plenty of time and if you do this on regular intervals it means that you will have a fairly high certainty of where you are as you're crossing the ocean the fourth way of navigating is something that we call radio navigation and now we're getting into the way that modern airliners are navigating so within radio navigation you actually have gps navigation as well because the satellites are utilizing radio signals to send and receive messages from an aircraft and depending on how long it takes for a radio signal to go and come back you can get a very accurate reading of the distance and if you have five six different satellites at very predetermined positions and they know exactly how far it is to reach you well then you can triangulate your position really really well so that's why the gps system is so accurate but that requires that you have enough satellites above the horizon in order to pinpoint your positions and that might not always be the case if you're flying in remote parts of the world in mountainous terrain for example you might not actually have that okay now in radio navigation we also have things like um ground-based radio navigation aids basically radio beacons and those beacons are still being used today even though they are disappearing more and more they will send out radio signals to the aircraft and the aircraft instruments will interpret those signals either as a bearing as in a an arrow a pointer that's pointing towards the the beacon or in the case of a vor it can actually give you a specific bearing so that you can fly in on a specific bearing and fly out from the navigational aid on a different bearing and this is very very useful when you're doing on route navigation and if you see the way that airways are built over europe you can still see that they tend to go in between these vr navaids because it's a way it's a backup it's a way to continue to fly and know where you are in case you would lose all other navigation and ils systems instrument landing systems so the systems that we use to guide the aircraft down to land at the runway they're also part of radio navigation so radio navigation is something that we use every day okay and it is both a backup and a primary way of navigating now this brings us to the fifth system which is inertial navigation inertial navigation that encompasses systems like the inertial navigation system the ins which is what it was called before and the more modern variant of it which is called inertial reference system irs which is what we're going to be talking about today now the name inertial reference system kind of indicates the way that the system works it works by measuring the inertia of the aircraft it's um it's a completely in-house system which means that the inertial reference system or the inertial navigation system was housed inside of the aircraft and did not need any external input in order to work in the early versions the ins system consisted of three different gyroscopes that were mounted perpendicular to each other in order to measure movement around all three different axes both pitch roll and yaw and an easy way to kind of explain how this system works is that it needs its initial position right it you need to input your initial position where you are and once that initial position has been fixed in the system it kind of measures where it is depending on where you are not right it knows that when you start to move when an acceleration and a movement is felt in one direction it can measure the amount of acceleration hence the amount of speed and also the time that it takes before the next acceleration comes and that way it will know all the time how it's moving in relation to its original position to make this a little bit easier to understand picture that you have a paper you know one of those checkered papers well providing that you know where to start on that paper if i then give you instructions to go for example three boxes up five boxes to the right six boxes down and another three boxes to the right and the two boxes down again well since you can just follow these boxes you will know where you end up and the inertial reference system works exactly like that but in all three dimensions so in the very early versions of this inertial navigation system that came about in 1960s and 70s they use conventional gyros but these conventional gyros both have a tendency to break down on regular intervals and there are also some internal friction inside of the gyros and whenever you have that it means that they're prone to start making errors over time so as the systems developed and evolved the the engineers started looking into ways of perfecting the system and making it less prone to errors and they started looking into something called laser ring gyros now laser ring gyros is really really fascinating um the way that those gyros works is that you have a a ring which is normally not actually a ring it's either a triangle or a rectangle of mirrors and then you have two lasers that are shot in opposite directions and then you have a receiver that measures the time it takes for the light to travel around the ring now if this ring stands completely still the time it takes for both of these lasers to reach the receptor is the same however if this ring moves during the time it takes for the laser to leave its source and go to the receptor well then depending on how it moves one of these lasers are going to move in a slightly longer distance than the other now obviously that difference is really really tiny but it's enough for the receiver to notice a slight difference in face between these lasers which create a kind of interference pattern that can be traced okay and this interference pattern it will differ depending on the amount of movements so this laser gyros is extremely exact in showing difference in movement and the benefit of these laser gyros is that there are no moving parts in them okay so if you put these laser gyros into an irs system which is what we're using right now um they will be extremely accurate the only kind of drift or error that you'll get out of a laser gyro is because of tiny imperfections in the mirrors or in the coating of the mirrors okay but it's very very small and they're very very good if you're using ring laser gyros you also need accelerometers so in order to make up an iru and inertial reference units of which we have two in the 737 you need three laser gyros and three accelerometers and once again they need to be set up in a way where they're perpendicular to each other so that they can show movement in all three planes if you're a flight simmer out there and you have been working on setting up the boeing 737 for departure you've noticed that as you go over the aft overhead panel in the cockpit and you switch the irs unit to align you will get timing there all right generally it takes between 6 and 10 minutes for the irs's to align and during that time as you continue with your pre-flight you are going to have to put your initial position into the fmc cdu and when you do that that will feed your position into the irs units and like we were talking about before the irs needs to know your original position in order to start figuring out everything else that it's doing during that time if you have a look at your primary flight display in your navigation display you will see that they're just full of flags and the reason for that is because the irs's are so much more than a navigational system it's also feeding your pitch roll your magnetic heading true heading wind drift angle crown speed true air speed vertical speed and a few other systems so the irs system is one of the more critical systems that we have on board so why does it take so long for it than to align well here is where it becomes really really fascinating because these laser gyros and accelerometers they are incredible okay they can sense even the smallest movement and acceleration this by the way is why we have to align them before passengers start boarding the aircraft because the fact of passengers moving around in the cabin can actually cause accelerations you know the aircraft movements of the aircraft enough to disturb the alignment process so we tend to align the irs is the first thing we do way before we board passengers and it can be a real problem if it's windy outside because it is windy outside if this has actually happened to me the wind might move the aircraft enough for the irs not to be able to align so the irs's they're sitting there and you power them up and when you do they will remember the last position they were in in most cases that's exactly the same position as you are in because an aircraft that comes in at night and parks and powers off is probably going to be there in the morning but it's not always true sometimes the aircraft has been moved to a different parking locations or even you know to a hangar overnight so you have to put in the accurate new position but as you are powering up the irs's now the irs's will start to feel all of the accelerations that is working on it as you're standing still on the ground you might ask yourself what do you mean acceleration when you're standing completely still well the first thing it will feel is gravity okay that's an acceleration and when it feels gravity it means that it can start to align itself in pitch and roll all right it knows that okay the gravity is straight down it will always point towards the core of the earth so i must be in this kind of level okay that might make sense if you think about it the next acceleration it will feel is the rotation of the earth so it will feel that oh i am moving forward with a speed of about 15 degrees per hour normally and depending on the speed it is feeling so that acceleration and the speed it notices it will also start figuring out where it is on the earth because the speed would be different if you are down by the equator where the speed is greater or if you're close to the pole where the speed is much much slower so now knowing the acceleration down towards the center of the earth and knowing the speed is going forward it can calculate all right i am probably at this latitude this is quicker when the speed is higher so the closer you are to the equator the quicker it will align but also it needs to know where it is longitude bias because it can only figure out right the speed should put me on this latitude i don't really know where i am longitude wise so that's why we have to put in the current position and now since it knows its latitude and longitude and pitch it will also start feeling okay so if i'm at this latitude i should have this speed however i am feeling a slight difference in angle here right the speed is not straight forward a little bit to an angle right so that must mean that the true north is that way so it's starting to calculate the direction of true north as well and all of these different components both the pitch its latitude longitude and true north they are depending on each other okay so they become more and more accurate the longer the irs's get to align themselves and this is why it takes six to ten minutes when you start it up in order for the irs's to have kind of figured out all of these different angles and all of these different accelerations and movement and make sense of them so once the irs's are done calculating all of this well then if you look down on your primary flight display it will just light up all of the flags will disappear you'll get all of the data needed and you can start operating using the irs's so as i kind of alluded to before the irs system is not working by itself in fact in a modern aircraft the all of the other inputs that the aircraft is providing like for example the dynamic pressure from the pitot tubes the static pressure the temperature even the gps position this is all fed into a unit called the air data inertial reference unit and then the computer is kind of interpreting all of this data and giving the absolute most accurate information back to the pilots through the primary flight display and the navigation display so this is a fantastic system does it have any weaknesses then yeah of course it does this is where it becomes a little bit complicated and also a little bit disappointing if you're a flat earther because a lot of the problems that the irs have is due to the fact that the earth is a spheroid right that it's almost round because the way that gyruses work is once a gyro is set it's actually not pointing in relation to the earth it's pointing to a point in space straight ahead okay so when we take off we start flying the aircraft obviously as we're covering distance we are following the surface of the earth that's what we don't want to fly out in space we want to fly over the surface of the earth now in relation to an irs this means that there will be an angular difference as we are traveling over the globe we will actually be according to the irs pitching down a little bit now this is a tiny little drift but as an aircraft is maybe covering a large portion of the earth it will become bigger and bigger as the aircraft starts flying so the irs's are set up to compensate for this because it also knows its position it's fairly easy to compensate for this particular drift but there are other drifts as well remember how we talked about the fact that the um that the earth was rotating and that the irs could feel that rotational speed well as the aircraft gets airborne the earth will still be rotating under it and this will cause errors as well when it comes to for example the speed so once again this is something that needs to be compensated for and if you are traveling in a north southerly direction the earth will rotate below you as well and the way that you fly even though it looks like a straight line over the earth's surface since the earth is constantly rotating it means that the aircraft is also kind of constantly turning a very tiny little bit but still it needs to do so because if you're going from a to b on a rotating sphere you are going to have to constantly kind of follow that rotation with the aircraft and of course a laser gyro once again is pointing on one particular point in space and if you are moving away from that point of space it will feel that as a slight turn and this also needs to be compensated for so there are all of these little drifts that needs to be taken into account in order for the irs system to work properly but since we are people of science we know about all of these things and modern irs systems are incredibly accurate and we know this because when we're out flying you can actually switch over on the efis control panel to look at your nav settings and in there you will see the aircraft symbol okay the aircraft symbol on the navigation display will be a little triangle and the position of the aircraft is at the top of that triangle and you can then see where the gps's thinks that you are and also where the irs's think that you are and you'll be amazed how close those are to each other like on this video for example you see that one of the irs's that's the little star symbol is slightly up ahead and to the left of the aircraft but the other irs is bang on together with the gps symbols that are also bang on now during normal day-to-day operation the irs's are actually using inputs from the gps signals to kind of counteract some of the errors that we were talking about earlier so this means that if the gps's would shut down completely for one reason or another then as the aircraft keeps flying initially the irs's would be very very exact but then over time these errors will start creeping in and the accuracy of the navigation might not be as exact and because of that the irs's are not to be used for example for or nav approaches or for really exact gps arrival routes but what would happen in case we were out flying and for whatever reason there would be a power interruption to the irs's so they would lose alignment well that wouldn't be great because as we were talking about before the irs's are actually the basis for our attitude information for example and loads of other really important instrumentation as well and because of that you can actually do a partial realignment of the irs's so even though you will lose your position so you wouldn't be able to use them for navigational purposes anymore you can actually put them into attitude and align the attitude and then get your primary flight you know instrumentation back again if that wouldn't be possible then we always have the standby horizon that can be used which is independent of the irs's as you can see guys as we started off this video with asking what would happen in case the gps would stop working and you were out flying somewhere of europe the answer to that is that we would just kind of go back on to the next system the next redundant system we have which are the irs's and we would be easily continuing to fly towards our destination now if the irs would then fail on us then we would have a problem right a lot of our instrumentation would disappear but we'd have the standby horizon and we would be able to continue to navigate using um conventional navigation as in these ground-based radio beacons and we can use them to navigate and after that we can use air traffic control to give us radar vectors to find our way down towards a working instrument landing system and get the aircraft safely down on the ground so there are loads and loads of layers of backups to help us get down safely doing research for an episode like this really gives me appreciation for the people who built these amazing fantastical navigational systems and it really makes you appreciate the importance of for example physics knowledge to understand the world that's going on around you and for mathematics because without really good knowledge in mathematics there's no way that they could have calibrated the systems down to these incredible levels and that's why i am so happy to have brilliant as a sponsor of this episode now brilliant is an absolutely fantastic online learning platform with hundreds of courses of things for example about fundamentals of mathematics physics but also these brain puzzles where you you have to kind of apply your knowledge and when you come across something that you don't really understand they will have a really good explanation for how to understand it so that you can build on that and solve more and more complex problems i have been working on brilliant together with my son lucas who's 11 years old and he really loves these brain puzzles and he gets so happy every time that he manages to solve something if this sounds interesting to you i would love for you to go down into the video description of this video and click on the brilliant link it will give you a whopping 20 of the annual fee of brilliant but it's completely free to open it up and check it out i hope that you've enjoyed this video which is a little bit more technical i would love to hear from you guys what you want me to do more of do you want me to do more reaction videos maybe more technical videos or maybe more videos about incidents and accidents let me know in the comment section here in the video or go into my discord server right there's a link in the video description below where you can just go in completely free to go both my discord server and to the mentor aviation app as well both of these forms are available you can just tag me and i'll try to answer it have an absolutely fantastic day wherever you are and i'll see you next time bye [Music] foreign you

Channel: Mentour Pilot

Views: 126,546

Keywords: IRS, Inertial reference system, Navigation system, Aircraft naviagation, how do aircraft, how do aircraft fly, how do pilots know where to go, how do pilots see at night, how do pilots navigate in the air, how do pilots navigate through clouds, mentour pilot 737 max, Mentour pilot, Boeing 737, Boeing 737MAX, How to become a pilot, Aircraft system knowledge, Dead reckoning, VOR, ADF, Laser gyro, Laser ring gyro, Boeing 747, Star navigation, Concorde, Fear of flying

Id: J89uROO8Gsc

Length: 27min 27sec (1647 seconds)

Published: Sat Jul 31 2021