How do trans-atlantic flights navigate?

[Stroppalot]

Presumably there are no beacons within range (?) Is it solely by INS and/or GPS?

Also, are trans-atlantic flights in radio contact the whole time, or are there points when they are out of range?

[vipero]

nope!
pilots know where they go because they line-up the planes to the direction they need before taking off.
e.g. for a westbound flight they take-off toward the big "W" they have on the compass (the other directions are: "N" "E" "S" but I'm still wondering what they stands for) and so on...

about the radio contact: I heard (but it's an uncontrolled rumor) that they use HF, not always anyway: only when the selcal sounds.


Ciao
Paolo

[This message has been edited by vipero (edited 15 March 2001).]

[This message has been edited by vipero (edited 15 March 2001).]

[EDDNR]

The Atlantic involves an interesting combination of technologies. For one part tiny lasers inside precision optical prisms detect the slightest movement of the aircraft since departure and in conjunction with the latest spacecraft orbiting the earth sending position and time signals to a sensitive reciever in the aircraft, our position is verified.

On the other hand, we wind up some squawky box originally designed in the 1930's and shout at the top of our voices to maximise the AM modulation, bouncing our short wave transmissions off the unreliable ionosphere layers and hope that a bloke in a hut 2,000 miles away in Gander can hear us over the top of 20 other aircraft doing the same thing.

Rod

[Jumbo Jockey]

Personally I find that if I keep the aeroplane between the red light out on the end of the left wing (how appropriate, don't you think, that the red light should be on the left wing...) and the green light out there on the end of the right wing, somehow I seem to end up in the right place almost every time.

[HEATHROW DIRECTOR]

As a USAF guy told ATC "We got a navigator up here. We just sharpen his pencil occasionally and he does OK by us".

[airforcenone]

Eastbound, tune in Atlantic 252 on the ADF.

[rolling circle]

A cleverly worded question - trans-atlantic flights navigate by virtue of the FMS, INS and GPS, the pilots of trans-atlantic flight just sit there and watch it happen.

[expedite_climb]

Ummmmmmmmm this way a bit, that way a bit.

To me, to you, to me

Maybe ?

[SFly]

Time out for all of you! If the kid wants to know, then let's tell him (or her).

Trans-atlantic navigation is, like the circle one said, is an interesting combination of FMS, INS, GPS. Most a/c are not equipped with GPS, but it doesn't really make a difference. The INS are just as good. There are 3 and the FMS interprets the varied information and gives a reading that goes along with a high-tech navigation system (on INS).

GPS is self-explanitory.
FMS controls all kinds of things really, it's a lot to explain (if you want the details, just ask).

ETOPS regulations are very important in twins, and the navigation is altered as such. Non-ETOPS usually follow similar routes, with a bit of differences. VORs, NDBs, DMEs and such are useless at such long distances, so advanced navigation systems are required. Air traffic is at a minimal, with radio operators acting as halfways between air traffic stations on mainlands such as Canada and Ireland, and are just there to aid in aircraft separation . . . not very necessary with TCAS systems installed.

Anything else?
Guess not.
SFly

[twistedenginestarter]

Now this doesn't go any further - OK?

It is commonly held that planes use their INS. Think about it though. These are extremely expensive/delicate and you are allowed to take off with just two. Would you take that risk?

Now...why do you think they put those route maps in the flight magazines? You Mr Passenger will notice you don't have any joysticks, pedals or constant attention of hostesses. That my friend is because you ain't flying the plane.

Now I know you're thinking how do they get those red lines going across the Atlantic everyday. I must confess whilst I've always assumed it's the Red Arrows who do it, I've never actually seen them in flagrante delecto.

How they compensate for wind wasn't in the ATPL syllabus so I'm not sure. More of a problem for me is how they get up to 60000 feet to do the Concorde ones.

So if one day you become an airline pilot forget all that FMC nonsense. Far too complicated. Just a gimmick.

All you need to do is keep to the right hand side of the red line.

[10W]

Sfly

I agree we should inform on the questions asked, but let's get it right ;)

There is no Transatlantic ATC station in Ireland, it's the radio station which is there. The ATC Centre is at Prestwick, Scotland.

Also the ATC guys and girls are not there to aid in separation, they are there to provide it. I'd love to see everyone have a free for all one day with only TCAS to save the day, especially as the Eastbound comes steaming through the Westbound core flow :)

Would you like to be the guinea pig ??

For those who don't like HF radio, it can be a thing of the past, get onto your beancounters. You can have datalink clearance delivery on both sides of the Atlantic plus automated waypoint reporting. All you need is something like ACARS.



------------------
10 West
UK ATC'er
[email protected]

[SFly]

Sorry bout that, bud . . . it's in Scotland, OK? Blimey, touchy touchy! Anyway, I'm talking to Shannon Oceanic for a good 200 miles after hitting ocean westbound, notice I said
"such as Ireland and Canada".

I didn't mean that transatlantic flight is a fun rollercoaster ride where people go willy nilly with just TCAS systems to help them as you put it, let's not exaggerate. I merely meant that (and you must agree), TCAS helps exponentially than 15 years ago when there was no such thing, and it backs up the separation ATC has already given.
There's no need to make threats . . . maybe you wanna take this outside! :mad:
SFly

[CrashDive]

Uhm, settle down now, settle down......

[HEATHROW DIRECTOR]

This Mr Stroppy is quite a character - asks utterly ridiculous questions and then sits back and watches the carnage!!

[SFly]

He's a bit sick, isn't he? :)

[10W]

Outside eh ?? Not really my style. Can't quite see the threat either, maybe the winking emoticon I used got lost in the translation :rolleyes: So let's agree that we're both adding to the answer in our own little ways.

<font face="Verdana, Arial, Helvetica" size="2">If the kid wants to know, then let's tell him (or her).</font>

Totally agree. And between us we are. I'm sure the answers you give are appreciated.

<font face="Verdana, Arial, Helvetica" size="2">and are just there to aid in aircraft separation . . . not very necessary with TCAS systems installed.</font>

I read that as implying no need for ATC. Which is a perfectly acceptable viewpoint. Not one I share, nor IFALPA. But it has its supporters and is a valid challenge to any system.

<font face="Verdana, Arial, Helvetica" size="2">Anyway, I'm talking to Shannon Oceanic for a good 200 miles after hitting ocean westbound,</font>

Ah,so it's you !! The callsign is SHANWICK :)

<font face="Verdana, Arial, Helvetica" size="2">notice I said "such as Ireland and Canada".</font>

I did notice, just correcting the fact that Ireland is not an example. I'm a born again pedant I'm afraid so you'll have to bear with me :)

<font face="Verdana, Arial, Helvetica" size="2">TCAS helps exponentially than 15 years ago when there was no such thing, and it backs up the separation ATC has already given.</font>

Well, I agree it has been a good thing but remember that TCAS is not a separation assurance tool (a common misconception) and so plays no part in providing it. It is of course a vital safety net and provides an excellent task in collision prevention. That's what it has been designed for. And once everyone eventually gets V7, it will be even better.

Regards

------------------
10 West
UK ATC'er
[email protected]

[This message has been edited by 10W (edited 16 March 2001).]

[SFly]

<font face="Verdana, Arial, Helvetica" size="2">I wish you wouldn't pick my words apart with "Quotes" such as this.</font>
Just for that I shall do the same.
<font face="Verdana, Arial, Helvetica" size="2">I read that as implying no need for ATC . . . and is a valid challenge to any system</font> You make it seem as though Inot what I meant![/b], I have said, as you double-quoted, that I meant that TCAS is a useful helper, rather than a useful replacement.

<font face="Verdana, Arial, Helvetica" size="2">Ah,so it's you !! The callsign is SHANWICK! </font>
I'm afraid I don't quite understand . . . I know who I am, I presume you must. Let me reiterate, though this shouldn't be necessary due to your ATC status. SHANNON FIR/UIR, which covers RO Ireland, and . . . "200 miles after hitting ocean westbound", (which is useful when travelling to Ireland or Manchester area, is [i]Irish controlled, as is SHANNON OCEANIC TA, south of SHANNON FIR/UIR, which is passed to and from the London/Birmingham area. SHANWICK OCEANIC is the large square area before Gander from 45 - 60 North, and 10 - 30 West that is controlled from Prestwick in Scotland. That shouldn't have been a necessary explaination, but obviously it was.

The whole "threat" thing is derived from the "guinea pig" remark. Wise words, clever.

I think that about covers it. :rolleyes:
Regards,
SFly

[F/O Junior]

10W, you work there now for how many, 10-20 years, and still don't get it ? ;)

SuperFly, there might be the chance that you pushed the wrong button here ....

[Stroppalot]

SFly, 10W.

Har! Gotcha going!

Thanks... ;-)

[twistedenginestarter]

I find it quite incredible that I make a preposterous suggestion and no one spots the deliberate mistake. This is supposed to be a professional channel!!!!

Red lines in the sky? Who's kidding who???!!! Pay attention! It can't work because you'd need big headlamps at night and pilots coming the other way would keep flashing you as, unlike the roads, you are all on different levels ...well hopefully.

Obviously the truth is you basically navigate like you do down the M1 in fog. You follow the lights of the bloke in front. If you are doing 600 mph there's no way you could otherwise see what was happening in front of you quickly enough.

Have you never wondered why the brightest navigation light on a plane (the white one) is at the rear????

[foxmoth]

Well I always flash my lights at the guy going the other way!

[SFly]

Stroptallot, I think you got all your questions answered just through our argument!
Glad to oblige!
SFly ;) ;)

[Deadleg]

All this person wanted was a serious answer to a serious question. Quite how it has ended up in a bun fight between ATC & a pilot is beyond me, but as professional aircrew I'm a little embarassed by your behaviour. Grow up!!!

[10W]

Deadleg

Fair enough. I suppose we all rose to the various baits being laid.

Sfly

Sorry for misunderstanding the TCAS comments. The position you state later is not how I initially interpreted your original posting. But then that's the benefit of dialogue. Opinions can change.

On the airspace thing, I still think your post is open to question. Do you mean 200 miles after hitting the Oceanic Boundary, or 200 miles after getting your feet metaphorically wet ?? As we're talking aviation, I would take it to mean the Oceanic Boundary. The only way you'd go 200 miles through Oceanic Airspace where ATC is provided by Shannon is if you were exiting the SOTA via 15W. Which of course is entirely feasible via lands End and GAPLI.

In any case, my point was that you believe there is a station called Shannon Oceanic. There isn't. It's ALWAYS Shannon Control, as it's an ATC service provided by a domestic agency. The only area of Oceanic airspace where Shannon provide a service, is the area of the SOTA of which you are obviously well aware. However, the Controlling Authority for that airspace remains SHANWICK Oceanic. The provision of ATS is DELEGATED to Shannon under an international Letter of Agreement. Legal semantics I know but under ICAO we have to do it that way.

F/O Junior

Yeah I get it ;) Unfortunately much of the correct legal detail and trivia is not in the charts, and quite rightly so. I suppose I should try to remember that this is where the pilot gets the innacurate information from sometimes :) The problem is that in my area I have to work with all the minute levels of detail and international protocol or else the politicians get all upset ;)

------------------
10 West
UK ATC'er
[email protected]

[EDDNR]

There is a simple answer to IRS: The aircraft 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 the greater), it obtains a difference, or deviation.

The Inertial Reference System uses deviations to generate error signal commands which instruct the aircraft to move from a position where it is to a position where it isn't, arriving at a position where it wasn't, or now is. Consequently, the position where it is, is now the position where it wasn't; thus, it follows logically that the position where it was is the position where it isn't.

In the event that the position where the aircraft now is, is not the position where it wasn't, the Inertial Reference System has acquired a variation. Variations are caused by external factors, the discussions of which are beyond the scope of this report.

A variation is the difference between where the aircraft is and where the aircraft wasn't. If the variation is considered to be a factor of significant magnitude, a correction may be applied by the use of the autopilot system. However, use of this correction requires that the aircraft now knows where it was because the variation has modified some of the information which the aircraft has, so it is sure where it isn't.

Nevertheless, the aircraft is sure where it isn't (within reason) and it knows where it was. It now subtracts where it should be from where it isn't, where it ought to be from where it wasn't (or vice versa) and integrates the difference with the product of where it shouldn't be and where it was; thus obtaining the difference between its deviation and its variation, which is a variable constant called "error".

Rod

[twistedenginestarter]

Getting across the Atlantic is the easy bit. You only have to report every now and again and you can follow others because there is always loads of people around. If you can't see them, listen to how loud they are on the RT and point to maximize the sound level.

Over land is more difficult because people put hundreds of radio aids or reporting points along your route for absolutely no fathomable reason apart from they're getting a load of back-handers from the suppliers.

Concorde copes with this by two mechanisms. Number one is all these waypoints are on a sort of American Express Card you put in a slot and then go back to calculating the losses on your Tech ISAs http://www.pprune.org/ubb/NonCGI/frown.gif http://www.pprune.org/ubb/NonCGI/frown.gif. The American Express card is BLACK of course. :)

The second mechanism is that the INS cross checks itself with DMEs which progressively remove position error as the plane goes by.

These DMEs are also on the American Express Card so you have time to calculate the losses on our non-Tech ISAs. http://www.pprune.org/ubb/NonCGI/frown.gif http://www.pprune.org/ubb/NonCGI/frown.gif

[twistedenginestarter]

I didn't cover where GPS figures.

GPS is a truly wonderful thing. No doubt about it. It does however have two significant shortcomings.

Firstly it does not have a specific level of accuracy. You have to check before your flight whether a satisfactory constellation of satellites will be available at your intended zone of navigation. Thus there is the risk your 747 has to sit at the gate waiting for the earth to rotate etc. A negligible probability for en-route navigation but your INS is usable in trickier conditions - why lose that?

The second reason, which applies to Concorde, is why buy another area navigation system when you've already got one that works just fine?

It'll be interesting to see whether the Airbus A380 has an INS option.