INS aligment
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Some info on laser gyros
You mean THIS? :wfish:
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Impostor! A real gyro doesn’t use tortillas
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How does me saying that the flight control system doesn’t use any INS/GPS data somehow translate into the FLCS system doesn’t use accelerometers?
The part where I assumed that the only gyros on the aircraft were in the INU.
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For a normal ramp start we have twenty minutes. There is really no reason not to do a full alignment. If you have to scramble, the INS seems pretty reliable with the aforementioned ninety seconds. Air alignments are effective too if you can find time in your flight to fly straight and level for a couple of minutes. The INS is an invaluable tool which is internal so that it is protected for your benefit as an aircrew member so you can always find your way no matter what.
Raven
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I think the OP was about another way to enter the 3D world.
Ramp
90 second Ramp
Taxiway
TakeoffI do a 90 second ramp on solo flight.
If you do a 90sec ramp on a mission, the package stpt times will be off and you’ll be early for push. I’m not sure the AI will do a 90sec ramp. I’ve never tried it with AI. -
For a normal ramp start we have twenty minutes. There is really no reason not to do a full alignment. If you have to scramble, the INS seems pretty reliable with the aforementioned ninety seconds.
100% … Not doing INS alignment is “passive cheat” once again.
IRL … you HAVE to perform a full alignment each time you fly. In case of GPS failure, INS remains you only way to get a position (except using pilotage chart or radionav) and INS is no optional.
Stored heading alignment are only made in specific cases (Live/Hot Scramble) and internal drift is bigger than with a nominal alignment.
Air alignments are effective too if you can find time in your flight to fly straight and level for a couple of minutes.
In flight align is for emergency only and do not give you a position. It is only to re-align (approximately) gyros in attitude (ADI/HUD) in case of temporary total loss of power … you loose INS positioning.
the package stpt times will be off and you’ll be early for push.
Plan holding pattens as it should be.
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If anyone is interested in R/L workings of aligning an aircraft’s positioning system, it has to do with something called compass rose. If you ever fly into an airport with a maintenance hanger that does alignment look for a circle that has an indicator facing magnetic north. There is scheduled maintenance where you have to take the aircraft to compass rose and align it with the heading and AVI calibrates all the nav equipment. When someone does an INS load before takeoff they are initializing the system to place the aircraft at the correct location in relation to the calibration at compass rose.
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If anyone is interested in R/L workings of aligning an aircraft’s positioning system, it has to do with something called compass rose. If you ever fly into an airport with a maintenance hanger that does alignment look for a circle that has an indicator facing magnetic north. There is scheduled maintenance where you have to take the aircraft to compass rose and align it with the heading and AVI calibrates all the nav equipment. When someone does an INS load before takeoff they are initializing the system to place the aircraft at the correct location in relation to the calibration at compass rose.
Sorry guy but the only thing that would ever require a compass rose on the F-16 would be the whiskey compass and I never saw that check done once in the 19 years I was working F-16s. The INS system through the normal alignment / entering of current coordinates and sensing the earth’s rotation gives your true heading. No compass roses required here.
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Stubbies is right. INS has absolutely nothing to do with a compass nor with magnetic field of the earth.
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A compass rose is for calibrating the standby compass, and for doing TACAN maintenance. If you have a station you can receive from that location.
Not all INS systems are ring laser equipped - in the older mechanical ones they may in fact get some input from a magnetic anomaly detector, which aids the alignment and nav solution by estimating local mag var. Those are becoming increasingly rare, though.
One of the more annoying problems with GPS aided INUs is that due to the GPS aiding during alignment the inertial unit can actually break or degrade and that can go undetected until someone operates them in an un-aided mode…by which time it’s generally a bit too late. So they need to be spot checked without using GPS at least occasionally.
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Good to know. I know this from AV-8BII+. Also a lot of people don’t even know compass rose is done. We had guys who had worked in our squadron for years and they never knew we took it to compass rose. They may have been using the MK3/MC-2000 making going to compass rose not needed. I guess the newer A/C have a system that does not need to do compass swinging. I know what INS is. I am curious as to what they use to position the A/C correctly in order to calibrate the INS. If the A/C doesn’t know where it is when it starts, it won’t know where it is during flight. Does the F-16 use GPS? INS keeps track of where the A/C has moved by gyroscopes and accelerometers, but if something doesn’t tell the INS it’s correct location before it starts moving then it won’t know where it is. It will have an arbitrary reference frame. It seems I have been misunderstood. I never claimed that the magnetic influence of the Earth was used in flight with INS. What is true is that in order to use INS accurately it has to be calibrated to a specific position on Earth. We used compass rose. What does the F-16 use?
It’s not a compass. It’s called compass rose.
Hey Stubbie, what shop were you in?
There are obviously some people here that are confused. We use a place called compass rose because it is a place on the surface of the Earth that has been marked as a very accurate and specific position using the latest surveying technology available. For us, that was GPS and satellites. There is no compass involved. It is simply called compass rose because on the ground is a big painting of a compass. We align the A/C so it is in the right spot and then AVI runs the INS system and calibrates it to that spot. What they are doing is loading the INS with the position of the A/C so it can be calibrated. Whiskey compass? LOL! That’s funny.
I would be happy to here someone explain to me how the F-16’s calibrate their INS.
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This warrants some research I think! Stevie, do you know which models took magnetic anomaly input? I had thought they exclusively worked off of the earths rotation similar to how Stubbies described it.
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I think that the old CAINS (ASN-130?..or previous) that was in earlier USN inventory operated this way…I think these were common to Harriers and Hornets back in the day. At least, I recall them from my own Harrier days. That one was replaced by the CAINS II, which I believe was an RLG upgrade, but even it still used MAD input for nav.
…then think about aligning one at sea…where you’re not stationary. Not by a long shot.
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Makes sense. I had thought you were saying old F-16 ones worked that way, which confused me.
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Not all INS systems are ring laser equipped - in the older mechanical ones they may in fact get some input from a magnetic anomaly detector, which aids the alignment and nav solution by estimating local mag var. Those are becoming increasingly rare, though. .
I guess you know that, Gyro laser nav units are called IRS (Inertial Reference System) or “Strap Down”. But even older INS (Inertial Navigation System) do not require mag inputs. They all works in true heading. But yes, they need the var info (instrument or sofware database in FMC/S) to elaborate the mag heading to send to the compass. But the inertial system itself do never require the var to be able to give your true heading, attitude, speed and and position. Unless it is something VERY old (prehistoric) between an INS and something else which I do not know (?).
EDIT
I think that the old CAINS (ASN-130?..or previous) that was in earlier USN inventory operated this way…I think these were common to Harriers and Hornets back in the day. At least, I recall them from my own Harrier days. That one was replaced by the CAINS II, which I believe was an RLG upgrade, but even it still used MAD input for nav.
^ this is precisely what I do not know
Thank you Stevie!
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Does the F-16 use GPS? INS keeps track of where the A/C has moved by gyroscopes and accelerometers, but if something doesn’t tell the INS it’s correct location before it starts moving then it won’t know where it is. It will have an arbitrary reference frame.
Newer F-16s have an EGI, which is a combination GPS/INS. As I understand it, normally the specific location old F-16s are parked is given to the jet for alignment. would love to hear more on how that is done from someone in the know!
The new ones have GPS and can work it out for themselves given a minute to do it.
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In two words: EGI are permanently (builded-in) hybridised IRS.
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Good videos covering older and newer INS systems. When I first started working on the F-16 the setuo was close to the first video which came to be known as the SINS or Standard INS to differentiate it from the RLG later on.
They didn’t get much into the limitations of SINS which come about from imperfections in the gyros, gyroscopic precession, etc. or in ways they used to limited drift (gyro rotational speed and mass) but not surprising since RLG is better as far as drift and MTBF is concerned.
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Newer F-16s have an EGI, which is a combination GPS/INS. As I understand it, normally the specific location old F-16s are parked is given to the jet for alignment. would love to hear more on how that is done from someone in the know!
The new ones have GPS and can work it out for themselves given a minute to do it.
Even though the EGI is a combined unit it is still RLG and GPS just integrated. On RLG you had to enter the coordinates within the first two minutes of alignment. If this was done after that two minute period the INS would automatically start the alignment over again.
I never worked on a EGI equipped F-16 (was already on the CV-22 by that point) so I cannot say for certain if that holds true for EGI.
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All INUs require a magnetic input for alignment - because in order to resolve earth rotational velocities into their components they need to know which way the body is pointed/oriented as the earth rotates; this can be done either by sensing mag var or by having the pilot hammer in the mag var at alignment manually (used to have to do this in the Day Attack Harrier early on). And trust me - this can really screw things up if you don’t get it correct.
Thinking is that one can get this from GPS these days…unless you can’t. Which is another way aided systems can mask faults in a combined GPS/INS (like the EGI).