Can Aircraft NAVIGATE by LASERS?!

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How did commercial aircraft find their way around the globe before the GPS was introduced? What would happen to a modern aircraft if the GPS would just suddenly stop working?
In todays episode I will bring you through the different navigational systems that aircraft use and I will go into great detail about a system that I bet you have never heard about if you are not in the industry - the Inertial Reference System (IRS)
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Below you will find the links to videos and sources used in this episode. Enjoy checking them out!
INU: @ vectornav.com
www.vectornav.com/images/defa...
INS2: @ Sanjay Acharya
en.wikipedia.org/wiki/Inertia...
Ring Laser Gyro: @ Nockson
commons.wikimedia.org/wiki/Fi...
Mirrors: @ materionbalzersoptics.com
www.materionbalzersoptics.com...
Three Gyros: @ materionbalzersoptics.com
www.materionbalzersoptics.com...
ADIRU: @ National Air and Space Museum
www.si.edu/object/inertial-re...
Gyroscope: @ Lucas Vieira
upload.wikimedia.org/wikipedi...
Sextant Viewing: @UNKNOWN
aviation.stackexchange.com/qu...

[@MentourPilot]

Did you know your BRAIN can TRICK you into thinking that an aircraft is HOVERING? Check out this video who explains it 👉🏻 kzbin.info/www/bejne/aaDWhKqcbMmai6s

[@wolves.]

how can you lie to people? this is disgusting.

[@rafakordaczek3275]

You clearly tricked me into an assumpion, that planes receive or emit laser beams outside of the aircraft. Nonetheless, I would give that one a pass, because the video is great.

[@scraggledy]

I just posted a comment related to this, but this reminded me so much of how my dad describes the weird sensation of being on a submarine deep in the ocean, especially near the equator. Fascinating.

[@deeperlayer]

just a small mistake the GPS on the aircraft only receives signal and by utilizing time calculation and some relatively correction in the computers the position is determined

[@valerieann8007]

Thank you for these great technical explanations! Do you have an email address to share possible ideas or inventions related to something you've discussed? 🌠 I know there are lots of satellites the military is no longer using that are free for worthy groups to use and there are probably lots of extra satellite space on Teslas Earth-Link satellites as well. I think it would be great for top navigation and communication developers to have a side project to develop an extra back-up system that his somehow safer or protected or backed up for every type of communication and navigation In case anything should happen to the existing systems in place, and we should invite the most capable engineers in related fields to brainstorm and develop one or more such a back up systems. I'm sure you're probably aware of certain exceptional engineers that might love such an endeavor that you could share this idea with or encourage. Obviously, it should be pursued. I encountered some software geniuses that are interested in developing such a communication network, and think it should be free to access. Possibly utilized by off-grid tech groups like Michael Tellinger's 'One Small Town' concept & similar. Check his latest and previous videos on it, if you get a chance. Anyway, thanks for your great videos! :)

[@ta6505]

The genius of Mentour Pilot is that he explains all the questions (and more) that I have while I'm listening to him -- during the episode, before I ask the questions.

[@MentourPilot]

Awesome! That’s what I’m trying to do

[@garrysekelli6776]

I just hope he doesn't get shut down by KZbin because his name is men tour. Instead of ungendered peoples tour.

[@erkkiboy]

So true!

[@amfwelsh]

@@garrysekelli6776 🙄🙄🙄🙄🙄

[@B2BWide]

@@MentourPilot And you really do manage this! I had at least 3 questions not to ask because you answered in almost in the moment I formed them!

[@hgradyspruce1975]

My father was a navigator in the USAF from the 40's through the 60's and I still have his sextant, his compass / protractor sets and his compasses. I remember as a kid we could go out on a clear night and he could identify the stars and constellations by name.

[@tedwalford7615]

Same, my dad. Interesting story, they trained him to navigate Europe, where they had to memorize the northern sky and European landmarks; then they assigned him to over-ocean flights in the southern hemisphere. But he got everyone home, so he must have figured it out. -- Appreciations to your dad!

[@sebxiou-lifestyle4465]

Hi Mr Parker. There is a documentary on YT about HMS Queen Elizabeth - one of our new aircraft carriers. It was on its initial sea-trials and a visit to New York harbour. The Captain was Jerry Kyd (now Admiral Kyd, RN Fleet Commander). He insisted on showing his young officers how to celestial-navigate, using sextant. He argued that, in future conflicts, the enemy might block / change GPS systems (there is evidence of the Iranians, Russians and Chinese doing this already) so non-electronic navigation is an important skill. Kudos to your father.

[@swfswf50]

Impressive

[@stracepipe]

My Dad flew Avro Lincolns in the 1950s and the navigator would stand up, look out of a glass window in the top of the fusilage and navigate using a sextant.

[@cleopatraoatcake7364]

What a blessing to have had a dad like that!

[@dickb2128]

Many many years ago, in fact November 1959, I was on a DC-7 headed to an Air Force assignment to Japan. Halfway across the Pacific ocean (I'm guessing it was about half way) one of the pilots came into the cabin with a sextant, stood on a short foot stool and put the sextant up to what appeared to be a window in the top of the fuselage. When asked what he was doing he replied that he was shooting a star to find out where we are. Petter, this was a very interesting video. At my advanced age (80) I didn't fully understand some of it was it was fascinating nonetheless. Thank you.

[@anniioakley9765]

I love this so much. Thank you for your service sky man! ✨

[@MentourPilot]

OBS: Small correction, the GPS is only a receiver. If you like these more technical episodes, please consider sharing them on social media, it really helps the channel! 🙏🙏 //Petter

[@elkeospert9188]

" Small correction, the GPS is only a receiver of signals except for synching of the atomic clock." Also a small correction - even for the syncronisation with the the clock in the GPS satellites (which are indeed atomic clocks) nothing has to be send from the GPS receiver on ground or in an aircraft to any GPS satellite The receiver needs to resolve four unknown variables which are latitude, longitude, height and time. To do so he needs to receive the signal from (at least) four different GPS-satellits, What me wonders a little bit: Of course GPS could be not available for some technical reasons (even when this happens extrem rarely) but GPS is not the only satellite based navigation system. Russia has its own system called GLONASS and China another one called BeiDou and the newest system is GALILEO provided by the European Union, Modern Smartphones can use all of these 4 systems to determine their position and the probability that all of them fail at the same time should be much lower than a loss of all engines...

[@elkeospert9188]

@@dbmandrake Using differential GPS where you have a fixed receiver on a well known position which can therefore calculates the relative error to the position he receives from GPS it is possible to get to a precision in the centimeter range (as long as you are close enough to such an reference receiver and have access to the correction data he calculates) That would be even more accurate than an ILS but as far as i know it is not used in commercial air traffic. What me also wonders why aircrafts do not have 4 GPS receiver - at the front, at the end and at the end of each wing. As the error from the real position is nearly the same for these 4 GPS receivers it would allow to determine all the angles of the aircraft very precise - and therefore also an aritifical horizon.

[@bartrademakers2486]

Apart from this GPS thing, a brilliant explanation within this short time frame!

[@elkeospert9188]

@@dbmandrake Ok - but a GPS receiver is nothing really expensive. In a smartphone i guess it cost less than 10 USD. Of course a GPS receiver for usage in an aircraft will cost much more due to all the addition certifications but that are one time costs - if you have your GPS receiver certified it makes not big difference if you install 2 or 4 or 8 of them.

[@bemk]

@@elkeospert9188 Technically you only need 3 points to determine the angle of a plane, and those 3 would also enable you to determine direction. That said, there are several instances known where somebody unknowingly managed to jam GPS signals. This is mostly seen near the ground (during RNAV approaches). From what I've heard it's mostly faulty electrical appliances. So whatever you do, you're going to need gyros anyway as a backup. Then there is also the problem that GPS and other satellite systems are both slow to begin with (50 bits per second, with the time signal being sent every 1.5 seconds), and prone to noise from for example atmospheric disturbances. This noise can be filtered out, but that again makes it even slower. So using this signal to run your attitude indicator would mean the data you're looking at runs several seconds behind. Fine to help calibrate the on-board gyros and other instruments, but not good enough to fly on by itself. The use of local positioning beacons can help calibrate the GPS signal to very high accuracy. This is used in systems like WAAS, SBAS, EGNOS, etc. All of those examples are systems that are local to a continent or country. The sum of all these systems has global coverage. This can greatly help in flying RNAV approaches, but again, due to the position sample rate, not as accurate as a fully equipped instrument landing system, hence the higher minimums. * I'm not a pilot. Just a software engineer who has worked with a few GPS receivers in the past.

[@sebastianbielmeier7098]

As a long-time Simulator Pilot, I did of course understand how to use the IRS and what it does. BUT, although I've read a ton of documentation and articles, I've NEVER really understood how it actually works. Until now! Thank you so much for this explanation! ❤👌

[@MentourPilot]

Great stuff!

[@TIO540S1]

I’ve had two incidents of losing GPS navigation, both times due to military jamming of the system, a known issue. Fortunately, I was in cruise at altitude and not on a GPS approach. I reverted to VOR navigation but was then limited to VOR to VOR routing as there is no area navigation system that doesn’t rely on GPS in my airplane (true for almost all GA aircraft). I wish I’d had INS capabilities and I’ve always been amazed by that technology. Edited to add: this was a phenomenally good explanation. I thought I understood inertial navigation and the technology for it pretty well, but I learned a lot from this presentation, thanks! Ps: this video will not make the flat earthers happy.

[@MentourPilot]

Yeah, good old conventional navigation

[@sasjadevries]

@@MrLockwire Well, actually American drones and navy ships have been hacked by other countries by spoofing a fake GPS signal. _(that was the encrypted military version of GPS, that one that they call impossible to spoof, that got spoofed)_ The drone thought that it was flying back and landing at an American airbase, when in fact it was landing on enemies' territory. Normal GPS can even be spoofed by individuals; you just need a software divined radio, an antenna, and some knowledge of what you're doing.

[@TIO540S1]

@@MrLockwire Well, of course, if I were the arguing, nationalistic kind I’d say Europe doesn’t have to worry so much because they rely on the Yanks to defend them. But fortunately, I’m not the arguing, nationalistic kind.

[@Frostyfication]

I'm sad to see VOR and NDB beacons being phased out in favour of GPS. As you said, GPS can be and is jammed and spoofed on purpose, which makes it risky to rely on it alone.

[@hairyairey]

@@Frostyfication Agreed, there was even a BBC article recently about how shipping could be affected by an outage with GPS (can't find it at the moment). Will Captains need to take a sextant with them just in case?

[@Kimdino1]

It strikes me that the Inertial Reference System is actually Dead Reckoning implemented electro-mechanically. But then greatly refined and automated.

[@hernanposnansky4830]

correct

[@cykkm]

@@hernanposnansky4830 Exactly! The explanation given in the video was not exactly correct. You still have to integrate the measured quantities.

[@kephalopod3054]

Now, electro-photonically.

[@josephherron7671]

Maybe the coolest video you've done so far. This was absolutely fascinating.

[@aryandon8185]

Ik

[@GuidoWarnecke]

Mm

[@GuidoWarnecke]

O

[@slabriprock5329]

Yes it is! I often think about the state of technology when I wad born in 1957 vs today, and it would really blow anyone's mind to be transported from then to now, no matter how tech savvy they were. The people that were working to create the first laser three years later would be dumbfounded at the uses for their invention we would take for granted. Ditto semiconductors and so many more. Sit down and try to jot down a list of devices incorporated into or replaced by your smart phone, and the technologies behind them. Just that one device would take a 1957 engineer or scientist quite a while to digest.

[@Dustin_Curley]

💯

[@Lucky32Luke]

As a land surveying civil engineer hats off to your very detailed and valuable explanation of positioning. Being also a teacher of engineering I would not be able to explain better than you did how complex and accurate but also how beautifully our navigation systems have been figured out. Flat Earthers must be having a headache now. :D

[@romeowhiskey1146]

Ah the days in CIVIL Engineering when using a DUMPY LEVEL to figure out ELEVATION at 2 different points on CAMPUS. IRS for dummies.

[@GoCoyote]

I believe that flat Earthers are afraid of complexity and prefer a simpler explanation without all the math. But they will still use the Nav aids in their phones and cars.

[@Lucky32Luke]

@@romeowhiskey1146 :D Been there and still using dumpy to establish level datums accurately. IRS is way more sophisticated and on a plane (or any moving vehicle) using a dumpy would be a very bad idea. The IRS system reminds me of the gyro theodolite in tunnelling and mining using the same principles.

[@victorfinberg8595]

@@GoCoyote I guess you've never interacted with flat earthers. From my observations (quite substantial), I can tell you that flat earthers aren't interested in explanations, and most specifically not your explanations, because they believe that you are a liar or brainwashed by NASA. Flat earthers take 100% of their "understanding" of the universe from a handful of websites. Unfortunately for them, 100% of what is found on those websites that they invest all their faith in is false.

[@victorfinberg8595]

Actually, flat earthers don't get headaches, because they don't ever exercise their brains. 100% of their knowledge is obtained by copy and paste operations from a very small number of websites, which happen to be filled with pure garbage. Almost all flat earthers that you will encounter are indistinguishable from bots.

[@harro747]

Hi Petter. I was an Air Force navigator for 8 years, an Air Force pilot for 16 years and then an airline pilot for 20 years. I have an in depth knowledge of all navigation systems having lived through the introduction of INS and GPS, but your explanation of IRS is the best I have ever seen. Bravo!

[@aguasadonas8346]

Respect sir

[@yottaforce]

What you describe is a cavity laser gyro. Another type is the fiber optic gyro. With that type you make a coil of fibers. That is a very efficient way of make a gyre. One of the nice features of that type is you can increase the sensitivity only by adding more windings to the coil. BTW: The interference effect is named the Sagnac after the French Physisist Georges Sagnac. He set up this experiment to disprove Einstein. It didn't work, but instead he invented a very useful instrument, so not bad after all. NB: I work in a company making fiber optic gyros for maritime navigation.

[@tomriley5790]

It doesn't disprove einstein - relativity states that the speed of light is constant for any observer in an inertial reference frame, the interference in laser gyroscopes only occurs if the gyroscope is rotating - which is not an inertial reference frame. If anything it supports relativity.

[@listerdave1240]

@@tomriley5790 I think that is exactly the point Morten is making. Sagnac >>tried

[@yottaforce]

@@tomriley5790 What Lister Dave said :-)

[@trueriver1950]

@@tomriley5790 correct. The experiment hoped to disprove Einstein by showing interference depending on the orientation (a lot like Michaelson and Morley were looking for). Turning the apparatus through 90deg should have caused an interference effect that lasted when the apparatus was again stationary in its new position. Thus it would have detected the motion of the Earth through the hypothetical aether. In fact the interference effect appeared while the apparatus was actually rotating and disappeared again as soon as the rotation stopped. It therefore supported Einstein rather than rebutting him. It is to the credit of the experinenter that, despite getting the opposite of his desired result, he did did publish anyway and in particular noted that he had created a device that detects non-inertial movement. The humility admit you are wrong is essential in research; the ability to turn a bad guess into a valuable outcome needs genius as well as that humility.

[@tomriley5790]

@@trueriver1950 interesting - years ago at school I actually built an interferometer, with a HENE laser, not as fancy as this out of old dentist's mirrors (cheaperst mirror I could find that front silvered and a half silvered mirror - it was more like atkinson-morley's than a laser gyroscope but it was surprisingly sensitive to any sort of movement or flexing - it would give an interference pattern if a lorry drove past outside or if you leaned on the table:-)! Still waiting for them to build the spacebased ones that they said they were going to all those years ago!

[@WarpRulez]

Flatearther: "Airplanes don't need to adjust for the curvature of the Earth when flying long distances." Actual pilot: "Actually they do. The inertial reference system is constantly adjusting for the curvature."

[@MentourPilot]

Word! 😉

[@ianmacfarlane1241]

15° per hour drift. Thanks Bob....

[@SmokeShadow49311]

@@ianmacfarlane1241As soon as he said 'Laser ring gryo' all I could think about was Bob and the devastation that was 'the 15° per hour drift'. - Thanks Bob 😉

[@tedsommer]

@@SmokeShadow49311 guess you guys didn't realize he was referencing the 15° drift from the aether, not the earth. For the earth's motions have never been detected. Same with measurable curvature. Hence why pilots fly under the assumption the earth is level and motionless, because it is. Ever notice that flights traveling west are faster than the same flight going east. If the earth is allegedly going east to west, then flights going east would never reach their destination.

[@tedsommer]

@@ianmacfarlane1241 then where's Bob's Nobel prize for discovering earth's rotation? You do know the rotation speed varied several degrees at higher altitudes, which would again debunk your precious heliononsensical model.

[@JohnnieWalkerGreen]

(2:10) Pilotage (2:57) Dead Reckoning (4:25) Celestial Navigation (5:30) Radio Navigation (7:47) Inertial Navigation (12:40) Inertial Refence Unit (IRU) (15:35) Setup (24:08) Redundancy

[@hairyairey]

"Ded Reckoning" (As I was told elsewhere - for deduced)

[@warmfreeze]

As an Avionics tech, i will tell you that you did an AMAZING job explain IRS.

[@scose]

18:41 the algorithm that fuses the different sensor inputs is most likely a nonlinear variant of the Kalman filter. It uses models of the aircraft dynamics and sensors, including their noise and errors, to produce a state estimate that compensates for each sensor's weaknesses and is more accurate than any one sensor on its own. Interesting topic if you like math!

[@MichaelSmith-fg8xh]

I was thinking along that line too. If I was trying to autoland I’d be looking at that but it seems like they’re deliberately not reducing everything to a single state so they can spot problems in the individual systems (eg. INS 1&2 are having a disagreement… you need to recalibrate)

[@scose]

@@MichaelSmith-fg8xh good point, detecting sensor failures adds another whole layer of complexity.

[@PilotFlo]

"A 15 degrees per hour drift..." - Thanks Bob

[@TheNixie1972]

6 Flat Earthers already disliked the video...

[@BornOnce]

You beat me to it! ,

[@sasjadevries]

Shhht! Don't tell the police, otherwise you will get fined for drifting on public roads.

[@citizenblue]

I thought SciManDan left this comment at first!

[@dawktah2]

You beat me to it too!

[@newoldbrain]

"The IRS System is one of the most critical systems" As any USA tax payer is painfully aware. Great video, as always.

[@aryandon8185]

Ok

[@togafly.]

Lmao

[@Katniss218]

I was looking for this comment

[@pmo764]

In fact the IRS system is what enabled/s the GPS system to begin with

[@scraggledy]

Rim shot! 😁🥁

[@steveb1739]

I remember the INS systems on the old Boeings had to be switched on some 13 minutes before the aircraft was moved in order for it to align with true north.

[@MatthijsvanDuin]

5:45 GPS navigation does not involve sending anything to satellites, it's not like DME. Each GPS satellite is a flying atomic clock (kept tightly synchronized to UTC) and continuously broadcasts the current time, and a GPS receiver determines its position from the timing-differences of the signals received from 4 or more satellites.

[@HyperSpaceProphet]

Exactly correct.

[@dogwalker666]

Agreed

[@cykkm]

A couple of technical details, hope you'll find them fascinating, as you've got it nearly right! First of all, to triangulate, precise timing is not enough; you also need to know the angular position of and the distance to the satellite, or, more precisely, time delay of signal between you and the satellite. GPS uses what's called the "pseudorange to the satellite: a distance as if the signal had traveled from it at the speed of light. Earth ionosphere delays the signal the most; unionized atmosphere delay is smaller, and using the constant 1.000300 or so below ionosphere for estimating the slowdown is enough. But the delay means the true range is no good for triangulation; you need a (slightly larger) pseudorange computed knowing the ionospheric conditions in the line of sight to the satellite. First, the time. GPS uses its own time reference, *not* in sync with the UTC. While at first GPS time was same as the UTC up to an offset (GPS time 0 was set at Jan 6, 1980, 00:00:00), GPS does not apply leap second corrections, and is currently ahead of UTC by 18s counting from the same time zero. All the so far 18 timepoints where a discrepancy of 1s was introduced are part of GPS almanac (wait for it). GPS time is also one of the most screaming examples demonstrating the difference between precision and accuracy. The accuracy of it is 1.5s (!!), the GPS tick length, while the precision is in the nanosecond range (up to 50ns given the ionospheric uncertainty). Also, due to the way time is transmitted, every other tick is received, lowering the accuracy to 3s. The next larger GPS time unit is a week, which starts on every Sunday at 00:00. GPS time is a pair (# of week in an epoch, # of 1.5s tick since Sunday midnight). An epoch ("cycle" in GPS lingo) rolls over every ~20 years. Today is cycle 2, week 135, day 1 (Sunday) in GPS time units. Next, the position. GPS transmits navigation data at a stunning rate of 50 bits per second(!). The data is sent in 5 "subframes", over and over, and each of them is exactly 6s long. Every subframe starts at precisely a GPS tick, and this is the main time signal source. Of course, it's more precise than the one bit time, 1/50 of a second. because it's derived from the carrier signal phase. The header contains technical info, including the satellite identification. The data portion of the 3 subframes each carry different information. Subframe 1 contains the time at the start of the frame and clock correction set by the operating facility. The satellite's clock cannot be adjusted only in steps of ±1.5s, remember? You get a nanosecond-precision delta to the tick count. The subframes 2 and 3 contain the ephemeris, i.e. the orbital parameters of the satellite, so you can compute where the sat exactly is at any given time, like at the start of each subframe. This has nearly enough data to get the fix, but you need to know the ionospheric delay of signal to get a better precision than 200m or so. And ionosphere is changing all the time, so the operator uploads changes to the ionospheric model to the satellites about once a day. This is what the subframes 4 and 5 are (partially) for. Every frame sends a next page of the almanac, which contains ephemerides (orbits) of all satellites and their radio transmission and CDMA coding parameters (let's not get too deep into that) to make a fix faster if you store the whole almanac in the receiver, and, most importantly, the current ionospheric model, so you can derive pseudorange for triangulation via a more precise time it has taken for the signal to travel by accounting for the ionospheric delay. The almanac is large and divided into 25 (IIRC) pages. The full frame consists of these 5 subframes, and is thus 30s long. A satellite thus sends 2 frames a minute, or 2880 frames a day (24×60×2), ánd the first frame of the day starts at 00:00 GPS time with the first page of the almanac. The full 25-page almanac need 25 frames to fully transmit, and thus cycles every 25×0.5min=12.5 minutes, with the next frame after the last page sending the first, and so on, over and over again. Older receivers took an ungodly time to "cold start"; newer ones use better algorithms and more computing power to search for the correct frequency and modulation parameters quicker, and cold-start faster. (I'm wondering if it was a good design decision to not stagger the almanac pages. If, for example, the first page sent in the day were {some hash number derived from the satellite SVID} mod 25, the whole almanac could be downloaded faster. As is, all satellites transmit the same almanac page at any given time.) Of course, you lose some bits, despite correcting codes, but the ephemeris is good for two hours and is normally updated hourly; the clock is easy to keep with a very high precision for a short time, so missing a few subframes is affordable, and does not mean the fix is lost. The whole almanac is good for a day or two for ionospheric delay data, 2 weeks for the constellation's ephemerides, because orbits are not perturbed this much, and much longer for radio/coding parameters. The almanac ephemerides are not good for ranging tho, you need to receive both current subframes 1, 2 and 3 for a correct fix. Also, it's fascinating that you need to account for both Special and General Relativity effects in GPS timing. Time in the Earth's gravity well on the surface ticks slower than up above, where gravity is less, so GR makes GPS clock on the satellite ticking faster for ground observers. But the fast-flying (~4 km/s) satellite also exhibits the SR time dilation, so we observe the clock as ticking slower than the clock's proper rate. The effects do not cancel out: GR apparent speed-up is larger, about 45 microseconds/day, while the SR slowdown is only 7 us/day; the net effect is a required correction of 38us/day.

[@keiyakins]

If memory serves, there were enough doubters that the first GPS satellites actually had the capability to turn off the correction for general and special relativity. Of course, they were left on and I think later revisions dropped it.

[@patrickbuick5459]

@@cykkm Does all of this account for doppler effect for high velocity receivers?

[@TheBillzilla]

FWIW almost all the 747 classic's I used to fly ran only on INS. I've flown with the old Delco Mk4 Carrousel, Delco PMS, Litton 72 & 92, Marconi FMS, and Honeywell FMS. I remember one trip I did from Fiji to Los Angeles, we were nearly 30 miles off-track after about ten hours, before we could pick up the VOR's from Santa Catalina, etc, to update our position. Hey, it was funny at the time. :)

[@sadeghzamiri2251]

I really missed your technical videos. Very nice. Good job 👍🏻

[@MentourPilot]

They will still come from time to time!

[@BryanDorr]

I enjoyed this episode on navigation. I'm fascinated with the 1930s US airmail routes using beacon lights and large concrete arrows pointing the route.

[@Gruftkriecher]

A nearly perfect video. I´ll rate it 9/10. Deducting that one point for explaining laser gyroscopes WITHOUT making fun of Bob Knodel (...a 15° per hour drift).

[@dogwalker666]

Agreed.

[@wb6anp]

Early navigation systems was also early IFR (I Follow Roads)

[@marcdennis6374]

I thought it was I Fly Railroads.

[@topethermohenes7658]

Could also be I follow the river 😂

[@trueriver1950]

@@topethermohenes7658 thanks for the mention... 😉

[@cr10001]

@@marcdennis6374 Been on a commercial flight once that followed a railway, c.1970. It was an Aerostar that had full IFR but the airfield (Kaikohe) had no navaids. Pilot let down through a hole in the clouds & we followed the Kaikohe branch line under the cloud base for about 10 miles till it wound round the hill that the airfield was on.

[@user-lp2op9uu1w]

Small correction, no signal is sent back to the GPS satellites from the GPS receiver!

[@Platypi007]

Which is one of the great things about it. I can carry a GPS receiver in my pocket, integrated into my phone, because it only needs to receive. If it needed to send a signal back to the satellites then it would need a pretty substantial antenna.

[@thesylance]

Yep, the satellites only give their Pings. They don't so anything else. The Computer inside the GPS Device is what is calculating the Position based on the exact time it recieves the pings of the sats. Otherwise the Satellites would be overburdend as heck by now.

[@thesylance]

@Don Adamson some planes from the US Airforce maybe. But not the usual "Consumer Type" Aircraft I guess.

[@marcdennis6374]

Years ago I worked for Sperry Gyroscope and my first job was aligning electromechanical gyros. Friction was the big enemy and the rotor was sealed in a helium atmosphere. Even with a helium atmosphere they ran extremely hot. Great presentation.

[@scraggledy]

So much great info! My dad was a Quartermaster in the US Submarine Force before the days of GPS. They mostly used inertial navigation and some use if radar, but occaisionally had use the sextant and charts when not submerged. Plenty of time to get accurate coordinates while at sea at a much slower speed than a jet! We sailed when I was young, and he tried teaching me some celestial navigation. Damn, it's a lot! I don't have that kind of patience!

[@ferminolaiz9848]

I just love the "And this is where it becomes really really fascinating" with the smile, it really shows how much a person loves what he does!!

I love how much this sounds like a direct answer to typical flat earth arguments without actually being one ("Pilots don't correct for the curvature of the earth/coriolis effect" in particular). I've been loving your investigation videos, but I'm happy that you're back with some more technical topics!

[@davidt.ashley4754]

Clearly, he and the IRS/INS manufacturers are part of the conspiracy. In fact, this is probably all handled by the same office within the government that faked the Apollo missions. (I'm joking, of course. There is just too much evidence that the earth is round.)

[@stevenemert837]

I got to 10:47 and heard a voice in my head saying, "... a 15 degree per hour drift." Thanks, Bob! Edit: Oh! I got to 16:30 and there it is!

[@BogdanSass]

@@stevenemert837 I literally started laughing out loud when reading your comment.... :)))))

[@josugambee3701]

As an amateur radio operator, I can assure you the earth is round. So many aspects of signal propagation are affected by earth's curvature. In fact, if you're listening to someone across the globe, you can occasionally hear an echo a fraction of a second later, due to the signal arriving via the short path, then via the long path (around the planet in the opposite direction). I don't think flat-earthers actually think the earth is flat; there's too much evidence against that. I think they just want to bicker. Then again, stupidity can be a formidable force.

[@CriticalInception]

@@davidt.ashley4754 there's actually a pilot who became a flat earther cuz he realized there was no measurable curvature and one day he had an issue w/ his IRS system so he tried to call the company to fix it. He found out one company makes all of the parts and they said just fly without it. It worked just fine flying over a flat earth, no adjustment for curvature. He's in one of the Mark Sargent subject matter expert series of interviews where professionals came out as flat earthers. Commercial Pilots, Army Master Gunners, Navy Missile Instructors, Civil Engineers, Vacuum Experts, Merchant Marines, Fighter Pilots, Electrical Engineers, Architects, PhD Spectroscopy scientists, Master's degree Lawyers, and Mechanical Engineers. Most of them come out when they're retired because the ones who say something while employed always seem to lose their job or get threatened, namely Brian Mullin, the mechanical engineer. And a KLM pilot was grounded and fired for interviewing Mark Sargent, talking about flat earth. It's a thing pilots talk about in the lounges but anyone who goes public gets fired.

[@ral008]

The airplane knows where it is at all times. It knows this because it knows where it isn't. By subtracting where it is from where it isn't, or where it isn't from where it is (whichever is greater), it obtains a difference, or deviation. The guidance subsystem uses deviations to generate corrective commands to drive the airplane from a position where it is to a position where it isn't, and arriving at a position where it wasn't, it now is. Consequently, the position where it is, is now the position that it wasn't, and it follows that the position that it was, is now the position that it isn't. In the event that the position that it is in is not the position that it wasn't, the system has acquired a variation, the variation being the difference between where the airplane is, and where it wasn't. If variation is considered to be a significant factor, it too may be corrected by the GPS. However, the airplane must also know where it was.

[@wesleyjohnson3786]

I was looking for this comment specifically

[@dantreadwell7421]

Perfect! That's it exactly.

[@roxout5743]

perfectly placed copypasta

[@benji0027]

I was also looking for this specific comment

[@toddavis8151]

I believe that there was an accident at a small airline where the pilots rushed their start up procedures and the IRS wasn’t aligned and they flew into a mountain

[@tedwalford7615]

Yep; watched that too recently.

[@NiHaoMike64]

The infamous "stendec" crash was because the pilots did not account for a significant headwind.

[@BernardKiprop]

Yep and they only needed 28 seconds more for the alignment to be complement by the time they took off

[@mrxmry3264]

@@NiHaoMike64 if you're talking about that crash in South America, they didn't have IRS because there was no IRS back then.

[@sorgfaeltig]

@@mrxmry3264 That accident with an ATR-42 in South America (Peru) was not so long ago that there was no IRS at that time. That ATR-42 aircraft had an AHRS (Attitude/Heading Reference System) this is not an IRS but it also has the need to have an alignment time on the ground in a very similar way as IRS. The rate-gyros measure the earth rotation and the accelerometers measure the attitude of the parked aircraft. This needs several minutes of automatic comuter.conrolled alignment. Yes, the aircraft crashed because it flew into a mountain. It flew into a mountain because the pilots were not able to do basic navigation because there was no crrect heading indication. They knew that the AHRS was not aligned. The had the red flags on the artificial horizon and the heading indication. But the captain decided to take-off and to fly visually.

[@leventsasmazel6292]

One of the best explanation of Navigation systems. As an electronical engineer I enjoyed every minute of this video.

[@issacortiz647]

This channel has made me love aviation and made me extremely interested in learning to fly. Thanks for your fantastic videos and sharing your expertise with all of us!

[@MentourPilot]

Glad to hear!!

[@JERios-wv8lx]

SAME HERE!!!

[@sixstringedthing]

@Arielle JS A Victor @ VAS Aviation, Juan @ blancolirio, Paul @ AVweb, TheFlightChannel... [list continues]

[@oxigenarian9763]

It is always amazing to me how much technology is built into an aircraft today. The array of devices, the IT systems that coordinate them and the unbelievable reliability they have is almost incomprehensible. It is engineering at the very highest level... I cannot say thanks enough to you for bringing all of these things together in your channel - I am learning so much!

[@greymark420]

How amazing seeing that Star Navigation Window, incredible how technology has changed. The engineers that design these technologies really are a amazing group of people, something we take for granted unfortunately. A really fascinating video.

[@njcurmudgeon]

I'm not a pilot, but I really enjoy these videos. Even if I don't always understand everything, it gives me a real appreciation for how things work and what air crews do everyday. Plus I like it when puppies are in the background...

[@Gallery90]

GPS satellites transmit only. They do not receive signals from the users. The calculations are done in the receiver. You should probably fix that.

[@MentourPilot]

Absolutely correct. My mistake

[@a4d9]

The same with VOR and ILS: the equipment in the airplane only receives. In all GNSS (Global Navigation Satellite System: GPS, GLONASS, Galileo, etc) the satellites sends a signal with the exact time the signal was sent (the position of the satellites are also sent) . The receiver (knowing where the satellites are) calculates the distance to each satellite.

[@wc3csrr]

@@MentourPilot Yet if that part may be wrong, it's better to understand with the "ping-pong" method and fixed senders for anyone not deep inside how triangulation. Maybe you can add a part on how triangulation works (I think you had it in one of the SAR videos) and add how this is "altered" to be used with any GNSS (transmitting own position -and- highly accurate time based by an atomic clock with very low drift).

[@adb012]

@@a4d9 ... Well, actually, and I may be splitting hairs here... the receiver doesn't initially now exactly where the satellites are. The satellite send signals composed basically of 2 components: time and position. So when the receiver receives this signal it knows where the satellite WAS when it sent it, but not where it is now. This can be a tiny effect, but it is not tiny at all. If the receiver knew the exact time, then it can compare the time the signal was sent with the time the signal was received and calculate the time it took the message to arrive (i.e. the transit time). Then you multiply by the speed of light and get the distance to the position the satellite was. That defines a sphere. Get the same for a second satellite and you have another sphere that would intersect with the first one in a circle. Get a 3rd sphere and it will intersect the circle in 2 points, one of which can usually be discarded (for example it is kilometers underground or in outer space). So you keep the last point and voila, that's your position. However, the standard quartz clock in the GPS receiver is not accurate enough, not even close. At the speed of light, one second off would mean that the distance to the satellite is off by 300,000 km. So what's next? Use a 4th satellite. Using 4 satellites you have 4 independent unknowns to be solved: any 3 of the distances to 3 of the satellites and the actual time. (the distance to the 4th satellite is not independent and can be directly calculated form the other 4 unknowns). What you finally get is a 4D coordinate: Latitude, longitude, altitude, and TIME. Time not provided by the cheap quartz clock in the GPS reliever, but from the atomic clocks in the satellites. The time displayed in the GPS receiver is the best clock you can have, short of having your own atomic clock. And if you think that the above was complicated, believe me, it was the simple version of how GPS works. We have not talked about ephemerides, revolution hyperboloids, time dilation due to gravity, time dilation due to movement, and WAAS.

[@enigmawyoming5201]

@@adb012 not to mention the fact that selective availability (SA) can be turned on with a flip of a switch, which can put an intentional error in the “time of transmission” component. Thus rendering GPS useless unless the receiver has the capability to read the transponding carrier wave and correct for the error. In other words, we are all being blessed by having GPS absent of such SA … which the US military has control over.

[@dfeuer]

I was a bit disappointed that you didn't point out that IRS is a refinement of the classic dead reckoning technique. It's really the same idea, only far, far more precise.

[@MasGinstiC]

Hei Petter, I never tend to leave messages on any YT videos or any social mediathings. But I want to give you a big thanks for all the content that you've been putting out there throughout the years and without knowing it helping me more than anything and anyone else to deal with personal sh*t. I only discovered your channel at the start of this year and it's actually the only 'entertainment' that can give my own thoughts some rest by completely pulling me into the video and that can make me calm down and finally relax a bit. I've been struggling mentally for a while now and also physically I'm struggling with pain and aching.. I can't seem to get any rest or chill-out moments anymore, except for when I'm watching your videos. I know , It may sound weird and/or lame but it's the truth. PS: I really never was that interested in Aviation due to other interests always being there , but Aviation seems to be a hidden interest which I only discovered through your channel. Really I CAN'T THANK YOU ENOUGH!!

[@sharoncassell9358]

Aviation is like a hidden art. If you were not around it as a youngster you don't tend to think about it. Nobody talks about it. If tour parents took you when you were small the exposure puts it in your subconscience. Then you may think about aviation. We used to draw airplanes make paper ones put together models then fly. This channel is making folks more aware of what goes into navigation and aviation itself.

[@tonytango6676]

I was reading a Pacific Western Airlines in-flight magazine in the 1980s. They had a combi 727 in their fleet which they used for freight and passengers particularly in the Canadian Arctic. It had a dome in the cockpit roof so they could do sextant work against the stars.

[@dustinmurdock276]

Incidents and accidents are my favorite however I also really enjoy the technical videos. Thanks for the content, always learn a lot.

[@MentourPilot]

Thank you! There will be more of both

[@MatthijsvanDuin]

5:06 It can be remarkably accurate. The SR-71 had an astro-inertial navigation system that used automated star-tracking to eliminate error-accumulation in the inertial system, which according to the Smithsonian National Air and Space Museum provided accuracy within 90 meters. I'd imagine modern variants can be even more accurate.

[@karlhenderson1908]

Ha ha, loved the animation of the small golden/yellow plane! 😂

[@gonetoearth2588]

Fantastic video!! As I pilot I have always found the old INS navigation systems fascinating. It's awesome how you take a complicated topic and you summarize it so all can understand; pilot or non-pilot. That's an art....keep up the great videos!

[@chromabotia]

One of your best vlogs ever! I am a engineer so I like the technical episodes.

[@MentourPilot]

Awesome! I’m a bit embarrassed of the GPS mistake though, have yo do something about that 🧐

[@Hondalover3000]

@@MentourPilot Mentour, you can add a note to the video at the point where you made the mistake about the GPS.

[@CubicSpline7713]

Well done. I worked on these systems, and you explained it elegantly.

[@stevenverhaegen8729]

Great explanation. In the 80s/90s I used to listen to NDB signals on LW. During the night propagation conditions change and LW signals can be heard over long distances. Coul hear Russian/North Scandinavian beacons back in Brussels. (not to be used for actual navigation of course. 😉)

[@AndyBilham]

This explanation is the best that I have read/listened to/watched, and I now have a much greater understanding of the way that the various navigation systems work and interact with each other. Clear, lucid explanations without swerving the technical issues. A fantastic video, please let's have more like these!

[@ericsheridan9208]

"A 15 degree per hour drift" Thanks Bob @SciManDan

[@mozsab]

The Venn diagram crossover of mentour and scimandan is bigger than I thought

[@dogwalker666]

@@mozsab indeed

[@baganatube]

I thought the title quite clickbaity, I was wrong, once again. This is fascinating! I naïvely assumed the time it took for alignment were taken to spin up the heavy fly wheels. :D

[@Markle2k]

The reason for the precise paint lines at gates and the numbers on the wall are to give pilots the information to input into their navigation systems. It is not just to make it easier for gate agents to maneuver the airways.

[@hairyairey]

@@Markle2k Are you sure? Because all I saw was the ICAO code being entered.

[@jmscott31]

The man is a walking aviation encyclopedia. Amazing! I Love your in depth explanations. You can fly me anywhere! :) Hahahah. I don't think one could feel more safe flying with such a pilot. We need more of you in the air!!!!!!!

[@christianchristiansen99]

What a fascinating topic. The fact that engineers were able to develop a precision navigation system without reliance on outside inputs, is truly amazing. Also, I thoroughly enjoyed the detailed technical descriptions, and not least the historical aspects. These types of systems are not just invented overnight, but rather evolve over time to achieve ever increasing accuracy and reliability.

[@WayneM1961]

The whole thing just blew my mind. You can drive a car, turn the steering wheel and your car will change it's direction. You can do this without ever understanding how and why it does it. Another great and fascinating Video Captain, explained only as you know how to

[@maxgyvero]

Not to be confused with Internal Revenue Service. Seriously though. The only consideration missing is IRS approaching a black hole with constant acceleration.

[@bobd2659]

Pretty certain if you're approaching a black hole, you've got more to worry about than EITHER IRS... Unless you're near CERN and something has SERIOUSLY gone wrong!

[@chriskoziarz3821]

IRSes as we have 'em on board on 737NG, would be useless in such (hypothetical only) situation: the laws of physics are different around such objects

[@HaraldMacGerhard]

At the end of the day, the gravitation may be so large that simply the light will not reach the sensors in the ring gyro or the light will be bent so much that it misses the sensor …. By that time I think the airplane will already be ”spagettified” 🤣

[@falxonPSN]

@@chriskoziarz3821 the laws of physics are the same. You just can't use some of the assumptions that you would on earth, like knowing gravity or angular rotation.

[@thetowndrunk988]

I wish the IRS could find a black hole

[@martineyles]

Great to see how all the redundant systems can help you navigate, and how they work. Would be good to see a companion video about a situation where GPS fails and how you deal with it practically - explaining the checklist for the incident, or showing it in a simulator.

[@chuck8835]

I am not a pilot but have been involved with 88 types of aircraft. This presentation is truly excellent.

[@gordslater]

20:46 this N-S or S-N drift earth rotation effect known to snipers, artillerymen and similar strange people as the Coriolis Effect. (it has absolutely nothing to do with your bath plughole btw)

[@mrxmry3264]

Correct, a bathtub is far too small to be affected by the coriolis effect. BTW, the coriolis effect is known to anyone with an education, which of course excludes flat earthers. But how many people have heard of the eötvös effect?

[@w1swh1]

Fabulous! I didn't appreciate how accurate inertial systems are until now. Yes knowledge of physics and mathematics are essential. Good job!

[@Frans_van-den-Berg]

The first pure inertial navigation flight which was considered the genesis of the Apollo moon landing was flown with a B-29 aboard the Spatial Inertial Reference Equipment of Charles Stark "Doc" Draper. This improved the reputation of his laboratory and awarded the lab to build the Apollo Guidance Computer by a wire telegram (as an alternative for WhatsApp, I guess 😀).

[@DaedalusYoung]

16:25 - "A 15 degree per hour drift" - "Thanks, Bob"

[@scottp131]

I had a pretty good idea about how they'd work by the name, but when you got into how incredible modern IRS' function, I was blown away. That is way too cool! Thanks for another amazing upload!

[@RealHiipixel]

This explanation of the laser part of the IRS was so fascinating and helpful 👍

[@FlywithMagnar]

Another great video! Here is a fascinating fact: For navigation, the SR-71 Blackbird used a NAS-14V2 astro-inertial guidance system (ANS). The inertial system used mechanical gyros, and position errors were corrected with celestial observations made by an unit nicknamed “R2-D2"tracked stars both day and night. The accuracy at Mach 3 was 300 meters, or 0.3 second.

[@robbarton7972]

There is some mechanics in a Ring Laser gyro as they are dithered to keep the Gyro unlocked and keep the output Sagnac frequency well away from zero. Lockin is caused by tiny mirror imperfections causing a small amount of laser light to feed back into the other beam. The 2 beams are accurately combined together to produce the Sagnac frequency. Active ring lasers gyro,s produce a frequency difference, passive gyros (fiber) give a phase difference.

[@MentourPilot]

Yes, I read up on those but found it to be a bit above what was needed to explain the basic function of the RLG.

[@dantreadwell7421]

Yea, but at least you don't ever have worry about gimbal lock.

[@cykkm]

​@@dantreadwell7421 Unless you're doing aerobatics, you do not need to worry about it in a 3-axis gimbaled rotating gyro either. That's a spacecraft problem. You can rotate the full 360° only about one (yaw) axis. To get into a gimbal lock you need to either roll 90⁰ or pitch 90⁰ at exactly the right heading (mod 180⁰, one of the two). Or pitch and roll 90⁰ regardless of the heading. At this point, the gimbal lock is probably not the worst of your problems... Also, you can read orientation from 3 separate, non-gimbaled gyros with mutually perpendicular axes and one DOF suspension, perpendicular to the inertial axis of each. It requires a certain amount of computation, as their angles no longer directly correspond to plane's axes, and a rotation of the plane about one axis causes the two of them, exactly those that are non-coaxial with the rotation, to move, but it's amazing what they did with analog computers even back in the 1940s. I do not really know which type of mechanical gyro aviation inertial nav uses (or used), one gimbaled or 3 independent.

[@dantreadwell7421]

@@cykkm fair point

[@DavidSmith-vr1nb]

@@cykkm I think I saw somewhere in a flat earth debunk, commercial aviation uses 3 independent ones.

[@MadeInNewYork73]

Fabulous! Thank you Petter for the history, earth science, and mathematics primer! Amazed they used the North Star in 1969 to navigate the ocean!

[@F-Man]

They also used the stars to navigate to the *moon!* Just as Petter describes them doing on transoceanic flights, the Apollo astronauts also used a periscope and sextant to sight stars and the earth’s and the moon’s horizon to extrapolate their distance from the earth and the moon, as well as their orientation.

[@paulbrouyere1735]

Great video on navigation. As a kid I read a book Vol de nuit (Night flight) of Alexandre de Saint Exupery. Fascinating how he described mountain landings after studying the flight patterns of seagulls. Also how he navigated on the stars crossing the pacific. He went missing as a fighter pilot over the Mediterranean Sea during WW2.

[@peterhansen5652]

I totally agree, no mathematics ever is developed unless for a reason, some old Greek started with Pythagoras, just to find the distance in a right-angled triangle. Really fascinating. Good video Peter!

[@hernanposnansky4830]

and measuring an exact right angle with sides 3, 4, 5 units in lenght

[@peterhansen5652]

@@hernanposnansky4830 That’s classic, opposite way to use Phytagoras 👍

[@TitusObbayi]

Very fascinating. I wonder if we could get a video explaining how a Bdazilian passenger jet (I think it was Varig 254) ended up going hundreds of miles in the opposite direction of its intended destination and crashing after running out of fuel without the pilots or ATC noticing what would seem to be an egregious navigation error? Good explanations

[@treyn8070]

I love videos like this with a real pilot explaining this stuff in great detail. Some people can know aviation but have never actually flown but you are a real pilot who has actually sat in and flown these huge things for years so you know little tricks of the trade that others would never have any idea about and you explain everything in a way that even somebody with absolutely no aviation skills and didn't even do good in school such as myself can understand and follow. Great video as always. 👏👏👏👏👏👍

[@raysstuffz]

This one was really really good. I love this detailed technical content, a big thank you Peter.

[@Themadoutbacker]

ON US Navy ships we use "Dead reckoning" as one of the backups to GPS. Speed÷heading over time manually plotting Latitude and longitude.

[@seanlannigan5109]

There are few times where I will commit more than 10 minutes to a KZbin video, but I see a Mentor Pilot notification and I drop what I'm doing 🤣 This was a spectacularly detailed video! Working in GIS, it was really cool to see how these systems compensate for all the same "issues" that I face in my field of work. Like curvature, rotation, gravity etc. Thanks for yet again, another amazing video!!

[@rishabhmehta2477]

I always took IRS’s for granted. Now I feel it is the most mind boggling piece of technology in aviation. Awesome video.

[@chriholt]

Petter, that was, for me, the absolutely most fascinating, interesting video you have ever done! Thank you so much!

[@theovandaele3220]

Love these in-depth vids. I live under the arrival route of an airport, and noticed that almost all planes line up above our village and cross a certain street at the exact same point (give or take 100 meters), even though they are still 20+ km out, no matter where they come from. I had no idea it worked with laser gyroscopes - but it makes so much sense.

[@rtkville]

A very informative and interesting video but as a retired military pilot I was up to date with current technology. But I retired 27 years ago and very little flying sense then, so you can see how this update was so amazing to me. Thank you very much for the update on nav aid tech.

[@bill8784]

Great show.

[@MentourPilot]

Thank you!

[@DanielJohnNicholson]

@@seanthompson258 Go away. 🙂

[@user-rq4np3vd1m]

@@seanthompson258 lol

[@thetowndrunk988]

@@seanthompson258 WTF does that have to do with an aviation video?

[@Glutnix]

It makes me think of the inertial guidance systems in the Apollo space program, and how gimbal lock would threaten the whole system

[@gordonrichardson2972]

Gyroscopic systems were much less convenient than laser IRS.

[@mikefrerichs8860]

One little nit that I haven't seen anyone else mention yet: At 16:40 the earth is rotating backwards. It's not important to your explanation, and I always enjoy your videos.

[@jimgraham6722]

Thanks for the brief on modern nav systems. When I did military flying in the 1970s INS was the wonder box. In those days they had a 4 degree of freedom platform and high performance spinning gyros. The alignment procedure as I recall did three main things, get the system up to operating temperature, calculate the local horizontal and true north. It did this by working out the local earthrate, sensing the Earth's rotation given the local latitude. The whole process took about 15 minutes. Those early INS were generally accurate to within 2 nm per hour.

[@bobsykes]

Absolutely fascinating! I love that the easier navigation systems were all used originally on ships and are still taught to pilots.

[@GraemePayne1967Marine]

I find it interesting that a few years ago the US Navy started teaching celestial navigation again. I guess they realized that space-based systems can be jammed, spoofed or destroyed.

[@thearmouredpenguin7148]

@@GraemePayne1967Marine "And all I ask is a tall ship and a star to steer her by,"

[@mgoksoy]

Hi dear Captain, as I watch your videos, I understand that becoming a pilot, a good pilot is no easy thing. Though I was in the airline business for 30 years, in the commercial side, I was always wondering how flying an airplane looks like. Thanks to you, I am learning everything necessary to fly an airplane. That satisfies me. Many thanks.

[@sharoncassell9358]

Do the satellites replace the ground beacons why they're disappearing?

[@billbeyatte]

Great treatment of the subject. I was navigator on a Navy P-3B Orion in the 1970s and used primarily Loran-C for over ocean nav. Our INS had significant drift and doing celestial was a nightmare.

[@marseille3252]

16:20 I love the personification of the IRS's when they're aligning, it's so cute in a way

[@erictaylor5462]

They even used celestial navigation on the Apollo missions.

[@paanikki]

Celestial navigation (navigating using stars, sun, planets, the moon or other celestial bodies) is actually the ONLY way to get an actual position fix in spacecraft traveling beyond LEO (low earth orbit). Though "celestial" does not mean using a traditional sextant, but an automatic, computer-controlled system to identify celestial bodies and measure angles between them. After all, Inertial navigation is just a modern, very accurate method of dead reckoning, so the cumulative error needs to be corrected every once in a while by having series of position fixes. Some time in the future, it might be possible to have a small number of navigation satellites orbiting the moon or another planet, if there was to be permanenr/long duration human activity that needs such navigation.

[@birdsarecool7490]

I love these videos alongside the investigation videos. Everything is understandable and I love the integration of a flight sim to show off procedures. I would bet a petty dollar that the IRS is definitely in the minimum equipment list

[@SueBobChicVid]

Love this detailed content about the systems. I learned so much in this video. Great stuff.

[@seanmcerlean]

Best explanation ever Petter,even beats ATPL ground theory seeing it visually.

[@Martin-mf1dn]

This is excellent. Your channel ignited my interest in aviation earlier this year, but I’m a tech nerd at heart, and this video was a great crossover between the two areas.

[@richc47us]

Wow! that was fantastic! I also have huge respect for those guys that were able to figure out how to build the IRS system and then the software to integrate it all into the navigational system. For something in the future, for us pilot wannabes, could you please go over how to read a sectional chart? I look at one of those and am totally overwhelmed!

[@dw8057]

I know nothing about flying (except for the worst part being impact) but I find this information interesting. Thank you to every pilot for keeping our crafts in the air. I never take my rides for granted.

[@jerseyshoredroneservices225]

That was really great. Thanks for doing all that research and then explaining it to us!

[@randyjude8346]

WOW... Wonderful experience for me. Also THANK YOU for the " advertising" at the end ( I actually watched rather than skip thru ).. more of these " deep technical" vids explained in laymen's terms are worth my time!... Thank you!

[@prommerjakub]

I mean.. anything and everything from you is amazing! I love the accident videos, but I'm seriously impressed by this technical stuff you explained to us today. I'd love more of it! Keep it up, you are the best!

[@MentourPilot]

Thank you! Feel free to help me spread it by sharing to social media.

[@aryandon8185]

@@MentourPilot ok

[@davidp2888]

You take a topic I know nothing about (aviation) and you share your knowledge and expertise in such a way that it draws me in. You have a gift for teaching. I really enjoy the technical videos like this one as well as the narrative ones where you describe what happened on a particular flight.

[@jean-francoisdorval5231]

Super video Petter! Thanks for the technical information. I want more of these tech infos.

[@saadn.3348]

Great episode! Thank you 🙏🏻... that’s why I LOVE aviation. Such a fascinating equipment.

[@rentzepopoulos]

Just to note that you don't actually send anything towards the GPS satellites; you only receive their signal and use time information included in their messages to triangulate your position. Other than that, in my opinion, this video was absolutely fantastic! :) Greetings from Greece.

[@MentourPilot]

Correct! I noticed that error as well as I was watching. I was thinking of how the clocks are coordinated with the satélites

[@castletown999]

@@MentourPilot Its my understanding that each satellite has an atomic clock. These are so incredibly stable that once synced up at launch they remain in sync forever. I don't know for sure but I imagine there must be some way of adjusting he sync from the ground from time to time. Anybody know?

[@Deltarious]

What made INS/IRS' 'click' for me was actually having to align and then see and correct the drift for one as a RIO in the game DCS in the back of an F-14. Getting to see how the system tries to 'guess' where you are in real time and how it slowly deviates is amazing, particularly over long flights where it is also taking the earth's curvature into account