Flying Basics: Inertial Navigation(INS) Degradation In DCS WORLD
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- čas přidán 6. 09. 2024
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I seem to remember there was a way to reset the INS on the Mirage by pressing a button as you flew over a known spot to recalibrate it?
czcams.com/video/pS27t5Dy68E/video.html
@@grimreapers thanks cap! Although from the first comment in that video it may not work as shown with the update anymore :-)!
The fact that modern airliners will have 3 INS units yet still need to use radio navigation (VOR) for calibration purposes should tell you something. INS was never intended for pin point navigation (or targeting) like what GPS more or less gives use today. It was intended to compensate for all the things that can mess up navigation, stuff like wind and imprecise instruments. It would tell you generally where you where better than if you didn't have it. And remember that in a war situation you're not going to have all the radio navigation and maybe even no GPS to tell you where your at, nor some friendly ATC telling you what the air pressure is which is needed for precise navigation. So INS can get you to a general location, but you'll need something else for precise targeting (or landing)
F-104G INS was pretty accurate, less than 3-4 nm deviation after a sortie provided it was a smooth cruise. Precision suffered quite a bit when doing high g ACMs. According to a pilot it would tell you "you are somewhere in Norther Europe".
One German navy F-104 pilot returned from a sortie over the Baltic see and used the radar to determine his location. He thought he had picked up a Danish island but was wondering why there was so more and more land to the south of that island showing up on the radar screen. It turned out he was heading towards the island of Rügen. GDR territory at that time. He quickly headed north to avoid interception by GDR and Russian fighters.
Fun fact, flying in circles at constant rates allows for the ins to not develop as much of an error as just flying in one direction. Even better. If you fly from one waypoint to the other and back again your ins will correct some of it drift error on the return. (This is for the mirage at least)
I don't know anything about INS drift but since it depends on accelerations it makes sense, integrating the accelerations on theoretically perfect circular trajectories gives a zero mean acceleration
thx
I was once in a glider (passenger only). Circling might be good for the INS but it was definitively not good for me.
@@bmanna495 INS systems will drift even if they aren't moving.
Becomes a right nuisance when you're trying to track something that only moves slowly.
Watching a lot of the videos on this channel has really got me interested a lot more in military aviation, thank you for this great demonstration of something i had no idea was even a thing before watching.
:)
Pleasure
The INS system works perfectly for a FLAT and STATIONERY and NONE ROTATING PLANE... before anyone gets triggered, there is a device on them made by Honeywell that factors in both the curved earth (the further from start you travel, the more round the bend you go) - but it also factors in the rotational earth (stood still on the equator, you are still moving 1,000mph that someone nearer the poles wouldn't be).
This device also must cancel out the earth's rotation around the sun, appx 66,000mp/h. Some might think this doesn't matter, the speed is constant, but it matters, the earth is rotating 12 degrees every hour and these speeds quickly product mind boggling errors if you ignore them in a complex motion sensor.
There is very little information available on these devices, but suffice to say, if you had the best laser gyro money could buy, and flew from England to Australia, the gyroscope would tip upside down (because people in Australia walk upside down :-)
But here's the kicker, if flying to Australia very fast took you just 12 hours, the 180' earth rotation would have you the right way up again, the people in UK are the ones upside down...
So imagine what would happen to the accuracy of the INS unit to provide even very rough positioning/speed/directional information, if this Honeywell device were to say break, or go missing? The INS would be completely useful within, hell you couldn't even be able to align it, because you need to be totally still.
If anyone bothered reading this and could follow my 7am logic, see if you can find one of these devices, and it might suprise you.
re-match for star destroyer
Interestingly, modern ins equipped tanks also have this kind of problem. everytime a gunner starts up the tank, he corrects the drift of the turret caused by ins degradation.
Thank you for making the video cap! This was very enlightening.
The mirage drift rate is very low at the beginning of the flight. You will get much higher drift rate after 42min of flight (Schuler Oscillations). If you want to test this without waiting 42min, there is a new slider for this in the ME
On the Viggen, with the Data Selector set to AKT POS, on UT, the last 2 digits that display on the readout are the TERNAV status and Position Error. If you're using the ground radar, particularly over ground it can scan well, the numbers "max out" at 5 0. My understanding is that the 0 represents the ground radar eliminating any error in the INS by updating as you fly over terrain. My understanding on this isn't 100%, that's kind of the basics of the Viggen ternav.
About 2, 3 nms per hr is expected drift in INS. Airliners today have 3 coupled INS/IRS updated by GNSS network & even TACAN /VORs on ground. The on board computer will select the most accurate inputs to keep updating the position every second or so.
CAT IIIC landings ( zero vis & zero ceiling) are enabled by pseudolite beacons near the runway.
Ring Laser gyro and Fiber Optic Gyro ( RLG , FOG) were more recent developments which are compact, lightweight, with hardly any moving parts.
Transatlantic flights need to have such equipment on board to fly OTS (ORGANISED TRACK SYSTEM) with stringent certification of the crew, the a/c, and of course the runway and ATC.
The flights are one-way. Morning: say London to New York & reverse pattern in the evening/ night.
I think I read up on this topic at some point, and if I recall correctly, the drift "per mile" as you put it in the video has to do with the curvature of the earth. So in effect, as you fly away from the calibration point, you will get so and so much drift, depending on where you calibrated, and in which direction you fly. That seems to be the major cause of drift, but of course there are other things as well that causes drift. Anyway, the point I was trying to make is, it's probably not going to be very accurate to fly in circles to rack up those air miles, as you will not have moved much from where you calibrated, so the major cause of drift is probably? ,, not going to be relevant. (I think you get it, even if I'm not very articulate. ) But it's also possible that high-g maneuvers has an even more major degrade effect, so I don't know.
thx
That’s only partially correct. The drift rate is linked to earth curvature. But if earth was flat drift would be much worse and non linear (it would become much faster over time). Knowing curvature allows correlating orientation and position with a feedback loop. This contains drift to something linear and causes the so called « Schuler Oscillations »
Been reading about it on Razbam discord, the drift might actually cancel itself in certain cases, so it's not necessarily the INS of the Mirage
thx
sorry but the ins system(navwass) that we used on the jaguar gr1 was very accurate you dont mention that the way the system works is via gyros and magnetic detector units which updated the system all the time also pilots would update the system enroute to a target all the time via waypoints to ensure that gyro drift didnt have an effect on the system .
Thanks
Wait, did the, improve the INS for the Mirage with the last update? Because a few weeks ago mine drifted like 3-4miles per half hour or so, which is why I eventually turned it off in the special options.
Cap! I have a request (sorry not sorry)... can you refuel from a tanker so much so that it will nolonger give any more fuel, like do they run out or is it infinite?
@THE VIRTUAL FIGHTER PROGRAM good to know!
Oh yeh absolutely happens almost every time we have a tanker in a mission!
@@grimreapers hmm, never had it happen to me, bit I guess it might just be that mission
bro i just buoght the tomcat and i already know what this is, you pull 1 5g turn and the whole thing is canted/off/fucked its horrible especially quick turns at high speeds
Third lol