Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
How Do Modern Airliners Navigate?  
User currently offlineAirCalSNA From United States of America, joined Mar 2010, 364 posts, RR: 0
Posted (3 years 8 months 4 weeks 1 day 4 hours ago) and read 8694 times:

I've been reading about flight navigation online, but haven't found an article says if there is a standard way that airliners navigate within the US. For example, do most airliners use GPS to navigate, or do they use VOR? At what point do these navigation aids kick in, so to speak--from listening to ATC it sounds like most planes first fly runway heading, are then given various heading instructions, and then told to proceed on course. Can someone provide a brief synopsis of take-off to landing navigation for the layperson? Thanks!

52 replies: All unread, showing first 25:
 
User currently offlineMir From United States of America, joined Jan 2004, 21855 posts, RR: 55
Reply 1, posted (3 years 8 months 4 weeks 1 day 4 hours ago) and read 8712 times:

Most modern airliners use a Flight Management System (FMS) to navigate. The FMS isn't really a navigation system on its own - it gets input from various other navigation sources (such as VOR, DME, IRS if installed, GPS if installed), calculates a position, and then calculates which way to go in order to fly the route. Take away all those sources, and the FMS is useless. The capability exists to navigate solely using VORs, but there's no real reason to unless the FMS starts acting up - the only time you'll be navigating by something other than the FMS in normal operations is when you're flying an ILS or LOC approach.

Quoting AirCalSNA (Thread starter):
At what point do these navigation aids kick in, so to speak--from listening to ATC it sounds like most planes first fly runway heading, are then given various heading instructions, and then told to proceed on course. Can someone provide a brief synopsis of take-off to landing navigation for the layperson?

It depends. Some airports have charted departures that will involve using the FMS to navigate right after takeoff. Other airports will vector their departures toward their route of flight, and in this case the pilots will just fly the headings while the FMS sits in the background waiting to take over when ATC gets the aircraft on its route.

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offlinebio15 From Colombia, joined Mar 2001, 1089 posts, RR: 7
Reply 2, posted (3 years 8 months 4 weeks 23 hours ago) and read 8596 times:

Quoting AirCalSNA (Thread starter):
For example, do most airliners use GPS to navigate, or do they use VOR?

Mir's reply should give you a good idea of how it works.

It's important to note that it's not a matter of "VOR or GPS" usage. If you have them available, both inputs should work together, whether you're flying a big airliner or a small piston-engine plane. The important thing is that you can accurately determine your position, regardless of the means you possess on the flight deck to do so.

All the airspaces in the world are changing and will move towards airspaces that rely less on ground based stations, as GNSS grows to be a more reliable and robust worldwide system.

----------

Quoting AirCalSNA (Thread starter):
Can someone provide a brief synopsis of take-off to landing navigation for the layperson?

- Usually you depart following a navigation procedure which is created - in most cases - by the local aviation regulation authorities. You may find many different departure procedures published for a single airport, and you use the one that suits you better depending on the route you're flying and the runway you're using. These procedures may use altitude turns, headings, radar vector (ATC instructions) segments, VORs and distance/radials, waypoints, or a combination of all. Waypoints are imaginary points in space created to design more efficient air routes that don't necessarily depend on ground stations, and GPS is precise enough to help you fly accurately between waypoints --> Depending on your aircraft navigation certified capabilities, you may or may not be able to navigate between waypoints. If you can't, you can always go back to the good old VOR navigation.

- In general terms, en-route you may navigate inside VOR airways or inside Waypoint airways (RNAV airways). Again, waypoints are carefully positioned to create straighter and therefore more efficient routes, so if you're certified to fly them, waypoint airways are the better choice.

- For approach you have the same methods available as for departure.

- For landing you may use several navigation means. These are just some of the commonly used, the most precise on top:
  • -ILS systems which give you precise vertical and lateral guidance towards the runway (ground based)
  • -Localizers (LOC) which is an ILS without the vertical guidance (ground based)
  • -GPS based approaches (satellite based)
  • -VORs (ground based)


Depending on the airport you may have various approaches available for each runway, and ATC can assign you the approach that best suits the current conditions. You may also request a different approach to that runway for whatever reason, and ATC generally has no problem accommodating that for you.


Alfredo


User currently offlineMir From United States of America, joined Jan 2004, 21855 posts, RR: 55
Reply 3, posted (3 years 8 months 4 weeks 23 hours ago) and read 8577 times:

Quoting bio15 (Reply 2):
It's important to note that it's not a matter of "VOR or GPS" usage. If you have them available, both inputs should work together, whether you're flying a big airliner or a small piston-engine plane.

In my experience, in small piston aircraft, you're generally only using one or the other - the two don't work together the same way they would in an airliner.

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offlinebio15 From Colombia, joined Mar 2001, 1089 posts, RR: 7
Reply 4, posted (3 years 8 months 4 weeks 22 hours ago) and read 8551 times:

Quoting Mir (Reply 3):
In my experience, in small piston aircraft, you're generally only using one or the other - the two don't work together the same way they would in an airliner.


--

If you have them available both inputs should work together.

Things clearly work different in smaller GA airplanes.


Alfredo


User currently offlineMir From United States of America, joined Jan 2004, 21855 posts, RR: 55
Reply 5, posted (3 years 8 months 4 weeks 22 hours ago) and read 8543 times:

Quoting bio15 (Reply 4):
If you have them available both inputs should work together.

That's my point - they don't. I can drive a CDI off of VOR or GPS, but not both at the same time, even if both are available (and that includes the G1000). One can (and I often do) use one CDI on GPS for navigation and another CDI off of a VOR for crosschecking, but that's still a case where only GPS is actually running the navigation.

That's in contrast to a situation where an FMS is running the navigation and being fed by both VOR and GPS simultaneously. I don't know of any light aircraft avionics system that can do that.

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offlineEmbraer195 From UK - England, joined Mar 2011, 9 posts, RR: 0
Reply 6, posted (3 years 8 months 4 weeks 21 hours ago) and read 8526 times:

Quoting Mir (Reply 5):
That's in contrast to a situation where an FMS is running the navigation and being fed by both VOR and GPS simultaneously

And so if the inputs from the two sources are significantly different, what happens? Is the FMS programmed to give each source a certain 'weighting' over the other to determine the position that it deems to be correct and to show on the ND?


User currently offlineMir From United States of America, joined Jan 2004, 21855 posts, RR: 55
Reply 7, posted (3 years 8 months 4 weeks 20 hours ago) and read 8493 times:

Quoting Embraer195 (Reply 6):
And so if the inputs from the two sources are significantly different, what happens? Is the FMS programmed to give each source a certain 'weighting' over the other to determine the position that it deems to be correct and to show on the ND?

That's a function of the FMS software, and will vary from unit to unit. In the unit I'm familiar with, there is a hierarchy of what the FMS looks at, with GPS first. If there's no GPS, then it goes to DMEs, and finally to AHRS and ADC data (basically a poor man's IRS). It will alert the pilot to these happenings, of course, and the pilot can take action to disable inputs that are clearly defective, or update the FMS position with known good data. Even if the FMS craps out entirely, the pilot can still revert to old-fashioned VOR-to-VOR navigation if need be.

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offlinedxing From , joined Dec 1969, posts, RR:
Reply 8, posted (3 years 8 months 4 weeks 19 hours ago) and read 8471 times:

Quoting AirCalSNA (Thread starter):
At what point do these navigation aids kick in, so to speak--from listening to ATC it sounds like most planes first fly runway heading, are then given various heading instructions, and then told to proceed on course. Can someone provide a brief synopsis of take-off to landing navigation for the layperson? Thanks!

Most major airports in the U.S. (and the world for that matter) use what are called SIDS which are standard instrument departure routes and listed in the Jepp manuals. Some are RNAV some are not. On a normal day once the wheels are up and the plane is into the second climb phase on goes the autopilot and the box flies the route unless the departure controller instructs otherwise. On bad weather days near the field an airliner can expect tactical reroutes which will lead them to either a reroute or to a common point at which they are hopefully past the weather and handed off to fly as filed. The box goes on and flies the route. At the other end it is pretty much exactly the reverse. Major airports have what are called STARS or standard arrival routes also published in Jepps. The crew is cleared from point to point and expected to make speed and altitude points along the way. Once down close its more vectoring than flying the box although if it is a slow day the box can be flown right up to final.

[Edited 2011-03-25 21:02:20]

[Edited 2011-03-25 21:02:52]

User currently offlinebio15 From Colombia, joined Mar 2001, 1089 posts, RR: 7
Reply 9, posted (3 years 8 months 4 weeks 17 hours ago) and read 8435 times:

Quoting Mir (Reply 5):
That's my point - they don't. I can drive a CDI off of VOR or GPS, but not both at the same time, even if both are available (and that includes the G1000). One can (and I often do) use one CDI on GPS for navigation and another CDI off of a VOR for crosschecking, but that's still a case where only GPS is actually running the navigation.


-
Again: If you have them available both inputs should work together.

Navigation is NOT defined as "what you couple with the autopilot", but as the process of determining your position and controlling the movement of the aircraft. If your autopilot is coupled with the GPS and you have VOR information displayed at the same time, then you're navigating with both: Only one is controlling movement of the airplane via the autopilot (on small GA airplanes), but the other part of monitoring and determining your position doesn't cease to exist. When you use both inputs to crosscheck, then both inputs are working together to give you position information.

If you have them available GPS and VOR are not exclusive, even if your airplane's autopilot can only fly coupled to one of them at a time, and that's my point. I don't plan on discussing GA Avionics vs. Airliner Avionics, that was not my point at all.


Alfredo


User currently offlineMir From United States of America, joined Jan 2004, 21855 posts, RR: 55
Reply 10, posted (3 years 8 months 4 weeks 16 hours ago) and read 8414 times:

Quoting bio15 (Reply 9):
If you have them available GPS and VOR are not exclusive, even if your airplane's autopilot can only fly coupled to one of them at a time, and that's my point. I don't plan on discussing GA Avionics vs. Airliner Avionics, that was not my point at all.

It's okay, we both mean the same thing - we're just using different ways of saying it.

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offlineEmbraer195 From UK - England, joined Mar 2011, 9 posts, RR: 0
Reply 11, posted (3 years 8 months 4 weeks 10 hours ago) and read 8349 times:

Quoting Mir (Reply 7):

Thanks Mir. Plenty of redundancy built into the system then, as per usual with aircraft design.


User currently offlineAirCalSNA From United States of America, joined Mar 2010, 364 posts, RR: 0
Reply 12, posted (3 years 8 months 4 weeks 2 hours ago) and read 8209 times:

Thanks for the very interesting information.

So I gather from the above discussion that the RNAV and other routes that airliners generally follow do not consist of a strict point-to-point flying from one VOR to another, for example. Rather, it sounds like the FMS uses the various data and then plots a course between and among the various reference points, such as VOR transmitters. Is that right?

[Edited 2011-03-26 14:17:21]

User currently offlinedxing From , joined Dec 1969, posts, RR:
Reply 13, posted (3 years 8 months 4 weeks 2 hours ago) and read 8192 times:

Quoting AirCalSNA (Reply 12):
Is that right?

Sort of but with INS it's more internal navigation augmented by outside references like GPS and VOR's. The pilots are not tuning into a new VOR signal every couple of hundred miles.

[Edited 2011-03-26 14:34:31]

User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 14, posted (3 years 8 months 3 weeks 6 days 19 hours ago) and read 8114 times:

Quoting AirCalSNA (Reply 12):
So I gather from the above discussion that the RNAV and other routes that airliners generally follow do not consist of a strict point-to-point flying from one VOR to another, for example. Rather, it sounds like the FMS uses the various data and then plots a course between and among the various reference points, such as VOR transmitters. Is that right?

Sort of. There are really two separate functions here...how does the airplane know where it is, and how does it define the route. A modern airliner knows where it is by filtering (combining) all the various position references (GPS, inertial, radio navaids) into a single "the position".

Once you know where you are, the FMS compares that to where you want to be (the flight plan) and directs the flight crew (flight director) or autopilot appropriately.

The flight plan route is defined by points in space...these can be VORs (many airways use VORs as endpoints), waypoints (defined by lat/long but referred to by names), lat/long positions, various abeam and intercept functions, or points defined relative navaids (e.g. 25 miles from the xxx VOR on the 125 radial), etc. A modern FMS can take input in all these forms and plays connect the dots to build the flight plan.

In autoflight, some airliners will also "lead the turn" to avoid overshooting the flight plan path. I.e. they start to turn before actually reaching the waypoint, so you may not actually overfly the waypoint.

Quoting dxing (Reply 13):
Sort of but with INS it's more internal navigation augmented by outside references like GPS and VOR's. The pilots are not tuning into a new VOR signal every couple of hundred miles.

No, but a modern navigation radio will constantly autotune and may be switching VORs (invisible to the flight crew) even more often than every couple of hundred miles.

Tom.


User currently offlineConfuscius From United States of America, joined Aug 2001, 3875 posts, RR: 1
Reply 15, posted (3 years 8 months 3 weeks 6 days 18 hours ago) and read 8104 times:

Quoting AirCalSNA (Reply 12):
So I gather from the above discussion that the RNAV and other routes that airliners generally follow do not consist of a strict point-to-point flying from one VOR to another,

Isn't the FAA just doing an overlay of current approaches to major airports which is counter to the RNAV RNP concept?



Ain't I a stinker?
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 16, posted (3 years 8 months 3 weeks 6 days 18 hours ago) and read 8101 times:

Quoting Confuscius (Reply 15):
Isn't the FAA just doing an overlay of current approaches to major airports which is counter to the RNAV RNP concept?

Do you mean LAAS and WAAS approaches? They're not counter to the RNAV/RNP concept, they're just an alternative technology to achieving the same goal as ILS.

Tom.


User currently offlineConfuscius From United States of America, joined Aug 2001, 3875 posts, RR: 1
Reply 17, posted (3 years 8 months 3 weeks 6 days 18 hours ago) and read 8095 times:

Quoting tdscanuck (Reply 16):
Do you mean LAAS and WAAS approaches?

I'm not sure. Here's the article...

http://www.aviationweek.com/aw/gener...hannel=awst&id=news/aw081009p3.xml



Ain't I a stinker?
User currently offlineMSJYOP28Apilot From United States of America, joined Jul 2009, 246 posts, RR: 1
Reply 18, posted (3 years 8 months 3 weeks 6 days 16 hours ago) and read 8080 times:

At my airline, I dont normally file flights on RNAV SIDs and STARS. This makes it a whole lot easier when we have an FMS inop mel, which is a fairly common mel item. High VORs have a range of 130 miles. Low VORs have a range of 40 miles and terminal VORs have a range of 25 miles. Most of the non RNAV SID and STARS use waypoints that are on the published plates for that airport and our also often waypoints on jet routes. For arrival and departure routes, they are built to route you to transition VORs along published jet routes. Some airports have departures and arrival routes that do radar vectoring to transition VORs.

Overall, the only real difference between RNAV routes and non RNAV is that the RNAV routes cannot be used without an FMS. There really isnt a huge difference.

With that said, Q routes do offer an advantage over J routes but in normal operation domestically I rarely ever file flights on Q routes. We only have a few routes where GPS and RNAV are required.

GPS approaches are still in their growing stage in aviation. At my airline, we cannot use GPS or RNAV approaches for planning alternates. If an alternate airport is not in VFR conditions, it better have a working ILS, LOC, VOR or NDB approach otherwise we cant use it as an alternate. It might have a GPS approach but we cannot derive our alternate minimums based on it.

One of the things I dread is a long flight with an FMS inop. I have to check the whole route to make sure we are always in adequate coverage for VORs. When some VORs are OTS, it makes things kind of interesting. The FMS will pick up on VOR locations even when the VOR is OTS. But with no FMS, you need the radio frequency to pick up the radials. Surpisingly, major transitions VORs out of places such as ATL like Vulcan Vortac are OTS rather frequently.

The one thing that wont change for a while is ATC. When vectoring, ATC uses radar and compass headings for many of their instructions enroute. I am not sure how ATC could vector and do holding patterns using only GPS and waypoints. So much of holding and vectoring is not planned in advance so it is nearly impossible to have vector points everywhere for flow control purposes.

Legally, my airline can operate into areas of forecast convective activity without RVSM, autopilot and FMS. In the pre-planning, it makes it very tricky routing around the highest echo tops and tstorms because you need the VOR coverage and sometimes the re-routes can be pretty far out. In the CRJ we only have one FMS so if we dont have one then we dont have a second one as a backup like we do in the CR9.

I really wish that the weather radars we had were better. It would make navigation in summer weather much more easier. They are limited in range and accuracy. Plus, none of the weather products can see cumulus phase CBs. If the CB doesnt have moisture falling to the ground, none of our radars can see it but these CBs are a real hazard to flying even if they arent yet producing visible moisture.


User currently offlinedxing From , joined Dec 1969, posts, RR:
Reply 19, posted (3 years 8 months 3 weeks 6 days 7 hours ago) and read 8020 times:

Quoting MSJYOP28Apilot (Reply 18):
Overall, the only real difference between RNAV routes and non RNAV is that the RNAV routes cannot be used without an FMS. There really isnt a huge difference.

I'd disagree based on the individual origin and destination. There can be quite a difference in milage alone.

Quoting MSJYOP28Apilot (Reply 18):
With that said, Q routes do offer an advantage over J routes but in normal operation domestically I rarely ever file flights on Q routes. We only have a few routes where GPS and RNAV are required.

Shame, I plan on the Q routes all the time and it can save 10-20 minutes depending on destination and winds. That said, there are still days when running the coastline is the better alternative.

Quoting MSJYOP28Apilot (Reply 18):
GPS approaches are still in their growing stage in aviation. At my airline, we cannot use GPS or RNAV approaches for planning alternates

Given the minimums for a fair amount of GPS approaches, it might as well be VFR. However it is nice to be able to fly the RNAV/RNP approach if the localizer fails. That happened a few weeks ago at DCA and if it wasn't for the fact we can fly the RNAV/RNP we wouldn't have gotten in.


User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 20, posted (3 years 8 months 3 weeks 5 days 6 hours ago) and read 7795 times:

Quoting MSJYOP28Apilot (Reply 18):
The one thing that wont change for a while is ATC. When vectoring, ATC uses radar and compass headings for many of their instructions enroute. I am not sure how ATC could vector and do holding patterns using only GPS and waypoints.

Why would they need to? I don't think anyone is proposing doing away with heading hold and altitude hold autoflight/flight director modes, and that's all you need to follow vectors.

Tom.


User currently offlineMir From United States of America, joined Jan 2004, 21855 posts, RR: 55
Reply 21, posted (3 years 8 months 3 weeks 5 days 4 hours ago) and read 7753 times:

Quoting tdscanuck (Reply 16):
Quoting Confuscius (Reply 15):
Isn't the FAA just doing an overlay of current approaches to major airports which is counter to the RNAV RNP concept?

Do you mean LAAS and WAAS approaches?

What he means is the practice of developing new RNAV procedures that are pretty much the same as current procedures, particularly in the area of SIDs and STARs. For example: take a look at these two STARs into ATL:

http://tiles.skyvector.com/sky/files/tpp/1103/pdf/00026SINCA.PDF

http://tiles.skyvector.com/sky/files/tpp/1103/pdf/00026CANUK.PDF

You'll notice that the two are EXACTLY the same until you get close to the airport, at which point you're probably getting radar vectors from ATC anyway. So there's not a whole lot of advantage of the RNAV procedure - I guess having one charted turn allows ATC to give one less vector, but it's still not the capacity brought on by additional routes that RNP has the potential for.

Ironically, the RNAV SIDs out of ATL are very diverse, and are more in line with the RNP concept. It's the FAA - who really knows why they do what they do?

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offlineMagcheck From United States of America, joined Aug 2010, 33 posts, RR: 0
Reply 22, posted (3 years 8 months 3 weeks 5 days 2 hours ago) and read 7702 times:

Quoting tdscanuck (Reply 16):
they're just an alternative technology to achieving the same goal as ILS.

Same goal ("principle") as ILS, but not the same degree of accuracy, correct? Even with LAAS, it's still not possible to get Cat III or even CAT II precision (minima), is it?


User currently offlineMir From United States of America, joined Jan 2004, 21855 posts, RR: 55
Reply 23, posted (3 years 8 months 3 weeks 5 days ago) and read 7681 times:

Quoting Magcheck (Reply 22):
Even with LAAS, it's still not possible to get Cat III or even CAT II precision (minima), is it?

It should be with LAAS - at least CatII. But LAAS kind of got pushed to the back burner because of cost issues for now, so WAAS (which in theory allows CatI minimums, but I've always seen them just a bit higher than that) is what we've got. Still a significant improvement from regular GPS, though.

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offlineflybaurlax From United States of America, joined Oct 2008, 638 posts, RR: 0
Reply 24, posted (3 years 8 months 3 weeks 4 days 23 hours ago) and read 7657 times:

Quoting Mir (Reply 21):
You'll notice that the two are EXACTLY the same until you get close to the airport, at which point you're probably getting radar vectors from ATC anyway. So there's not a whole lot of advantage of the RNAV procedure - I guess having one charted turn allows ATC to give one less vector, but it's still not the capacity brought on by additional routes that RNP has the potential for.

Most RNP procedures in and out of bigger terminal areas are the same as RNAV and other procedures, but it's in the smaller, less traveled airports where RNP really saves you. If you look at Alaska, there are tons of RNP procedures that save miles, thus save fuel. They can do direct descent and direct to closer waypoints, than ILS or NDB approaches. Instead of the dive and drive, they can basically cut to idle 100 nm out and only use power a few miles away as they configure for landing.

Here's a brief list of airports in Alaska that AS utilizes RNP procedures: ADK, OME, OTZ, SCC, JNU, and a few others. They definitely save fuel.



Boilerup! Go Purdue!
25 Post contains links B727LVR : Speaking of WAAS... I read an AEA article on it and was rather impressed, as an avionics tech, by what it will allow. The article: http://www.aea.net
26 tdscanuck : LAAS can get CatIII equivalent precision, and without interference from stuff in the ILS critical area...I don't think LAAS approaches are certified
27 dxing : Both, technical as in they have to get the equipment sited and running and cost is holding it back, regulatory in that the airlines will still have t
28 tdscanuck : By "technical" I meant there's no reason you can't get CatIII accuracy out of a LAAS...but you're absolutely right that it doesn't do any good until
29 Quokka : So the FMS determines current position (location) relative to destination and calculates a flight path. If on route another aircraft is encountered, d
30 Fly2HMO : Sort of. It knows it's position relative to any point on the earth. And you as a pilot have to tell the FMS how you want to get to your destination,
31 Flighty : I guess this thread is really asking the question, what happens when/if GPS has a virus and goes down? How big of a safety problem is that, with thous
32 Fly2HMO : That's a Hollywood scenario. A slightly more realistic scenario is a massive solar flare wiping out the satellites. Currently? Shouldn't be too big o
33 Flighty : Cool thanks for your reply. Yes it sounded like LORAN had a theoretical need. I think China has the capacity to disable sats if they really want to.
34 Post contains images Confuscius : There's a compass in front of the overhead panel. [Edited 2011-03-30 14:20:01]
35 tristarsteve : All this talk about GPS going down being the end of navigation, it wasn't so long ago that we didn't have it. I've been working here in ARN since 1987
36 Post contains images bio15 : It's good to have some hand-flying fun every once in a while Gets you tired real quick though! Alfredo
37 Post contains images B727LVR : As stated above, the only back-ups currently are INS/IRS, VOR, ADF, and your Standby Compas but if you need to use this there are more than likely so
38 Post contains images Fly2HMO : The problem is in the near future we won't have much to fall back on. Dead reckoning may be fine crossing an ocean or some other barren place, but go
39 tdscanuck : Nope. TCAS will warn you of impending conflicts and provide guidance to the flight crew as to which way to go (if the other aircraft also has TCAS),
40 tristarsteve : On a newish airliner the INS is really an IRS. a Sensor not a nav system. Back on the B747-200 the INS actually navigated the aircrat, but nowadays t
41 Pihero : The raw data do exist, are available if needed as a means of *inertial based* dead-reckoning. The navigation system of a modern airliner is a lot mor
42 travelavnut : So this would be automatic "triangulation" with 2 DME beacons? And data from this will compensate the IRS drift?
43 Fly2HMO : Again, when Nextgen comes online this will not be the case. If anything a couple of VORs will remain in essential areas. The decommissioning of NDBs
44 Pihero : Yes No ; It will become the basis for the FMS position. The system will never compensate for IRS drift : 1/- The IRSs are left on their own. What the
45 travelavnut : As always thank you Pihero! Trianugation between 2 points also results in IIRC 2 possible locations, how is this handled/solved?
46 Pihero : by eliminating the intersection that's the most unlikely - either through the mix IRS position or the use of a third DME, very often available in con
47 tristarsteve : And remember that DME/DME does not mean two DME beacons, it means two DME boxes. The DME constantly retunes looking for new DME, so could be using man
48 Pihero : Five stations in all on the FMs I'm using the most On each ADIRU or on the mix IRS position ?
49 tdscanuck : That's not universally true...some IRS's can do an in-flight realignment, which zeros out their bias. Tom.
50 Post contains images travelavnut : Thanks! Cool thanks! I assume the ADIRU's use ring laser gyroscopes nowadays?
51 Pihero : Can you tell us more ? I thought that after the FMGC avent, that solution had been abandoned. The last time I did an in-flight re-alignment was on a
52 tdscanuck : Some of the newest IRS's will use GPS data to realign themselves in flight if there is a power interruption to the IRS. It takes several minutes beca
Top Of Page
Forum Index

Reply To This Topic How Do Modern Airliners Navigate?
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
How Do Airliners Calculate Magnetic Heading posted Mon May 17 2010 02:26:33 by KiwiFlyer1
How Do Airliners Compensate For Turning Engines? posted Sun Jun 1 2008 14:46:59 by UAL747
737-200: How Do They Navigate? posted Mon Feb 6 2006 22:50:21 by Mozart
How Do Airliners Get Oxygen At 30k Ft? posted Wed Nov 9 2005 21:16:51 by Quickmover
John Wayne Airport...How Do Airliners Operate? posted Wed Oct 2 2002 03:30:27 by Cmchardyfl
How Do Planes Navigate Over Water? posted Mon Sep 10 2001 01:25:07 by Crank
How Do Modern Airliners Navigate? posted Fri Mar 25 2011 12:09:49 by AirCalSNA
How Do Single Pilots Go To The Toilet? posted Sun Feb 27 2011 02:27:41 by Dainan
How Do Airlines Prepare For A New Airplane? posted Thu Feb 3 2011 15:14:32 by c5load
How Do Ramjets Make Electricity? posted Sat Jan 29 2011 22:45:22 by DocLightning

Sponsor Message:
Printer friendly format