Mid Atlantic Radar?
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Mid Atlantic Radar?
Whilst coming back from the Carribean the other day a curious thing happened. Flying a random route under CPDLC control with New York we encountered weather en route and made a small track deviation to the left. We were in the middle of a long leg and about six hundred miles from the nearest coast. After a couple of minutes we received a CPDLC message from New York stating 'track deviation left approved' and 'rejoin track before such and such a time'. We had not informed them of our deviation and it's the only time I've seen this message unprompted. We were way out of land based radar range and ADS had not made a report between waypoints. I'm at a loss to explain how NY knew we were off track. Is there some sort of satellite radar system or can they plug into military radar on ships. Can anyone provide an answer?
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Best guess is CPDLC is transmitting your position automatically at regular intervals - pseudo radar if you like. If you go a wandering, they will see you 
The end of the casual deviation as we know it perhaps !
The end of the casual deviation as we know it perhaps !
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If you had been radar coupled a really small track deviation would have been difficult to detect on the range involved, and I don't believe that was the case. I read a report a while ago on how they manage the traffic across the pond, and they don't (didn't?) use a plan based display, but more a linear display based on fpcp.
Perhaps the 14 flights ahead of you had all diverted left & they were anticipating your request? I would do so in my radar sector.
Perhaps the 14 flights ahead had asked for diversion right and this was desperately inconvenient so they nudge you left instead? I have done so in my radar sector
When you refer to waypoints do you mean position reports by CPDLC? They are nice for the estimates they contain for procedural time standards, but ADS/C does indeed transmit regular position reports, generating a ADS Route Conformance Warning - ARCW warning on our screens when the FMC is different to the flight plan. The reporting period is independent of track waypoints or CPDLC reports and is ATC selectable, based on our requirements.
I know we (Oz) won't get a system alert you are off track until a report arrives, but we can overide the contract and ask for a "one-shot". Are you certain New York didn't, detecting your diversion? We get alerts when flights yaw a bit to give both sides a view of Ayre's Rock (Uluru).
You say that as if it were a bad thing...
Perhaps the 14 flights ahead of you had all diverted left & they were anticipating your request? I would do so in my radar sector.
Perhaps the 14 flights ahead had asked for diversion right and this was desperately inconvenient so they nudge you left instead? I have done so in my radar sector
When you refer to waypoints do you mean position reports by CPDLC? They are nice for the estimates they contain for procedural time standards, but ADS/C does indeed transmit regular position reports, generating a ADS Route Conformance Warning - ARCW warning on our screens when the FMC is different to the flight plan. The reporting period is independent of track waypoints or CPDLC reports and is ATC selectable, based on our requirements.
I know we (Oz) won't get a system alert you are off track until a report arrives, but we can overide the contract and ask for a "one-shot". Are you certain New York didn't, detecting your diversion? We get alerts when flights yaw a bit to give both sides a view of Ayre's Rock (Uluru).
The end of the casual deviation as we know it perhaps !
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The reason that New York centre will know that you are off course in a non radar environment is that the ADS contract set up at logon has armed the system to send an ADS report if the aircraft deviates more than 5nm. The controller will get a warning message at the console and with the new system having a synthetic display the aircrafts actual position will also be shown.
So remember if you are logged on, someone is always watching!
So remember if you are logged on, someone is always watching!
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I am afraid Oceans13 is correct. The systems will keep getting smarter and more active in reporting as the RNP values decrease. Just wait for the daisy chaining of ADS-B data, it will be more acurate than radar and update real time.
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Oceans13 is correct.
I work in the North Atlantic Area of New York Center. One of the contracts that we set up with ADS equipped aircraft is a 5 mile Lateral Deviation Event. If you deviate more than 5 miles off of your route of flight, your FMS will rat you out. The ADS report that we get is very accurate and, as Oceans13 mentioned, we can see exactly where you are and where you should be. Upon receipt of a Lateral Deviation Event report, most controllers will simply up link a weather deviation clearance with a time/position to rejoin by. There are a few of my co-workers who will first ask you if you are deviating but what's the point? We already know that you are.
Our response time to CPDLC requests is very low. Usually less then 2 minutes for a climb, even less for a deviation request. Your best bet is to ask before you deviate.
BTW, one of the other contract rates that we set up is a 20 minute periodic report. That means we get a position report every 20 minutes regardless of route. This is nice for the you guys because you can basically fly point to point and not have to fly specific routes. So if you wanted to go direct from 40W to point on the other side of our FIR, it shouldn't be a problem provided that there is no traffic for you at the time of your request.
Hope this helps.
I work in the North Atlantic Area of New York Center. One of the contracts that we set up with ADS equipped aircraft is a 5 mile Lateral Deviation Event. If you deviate more than 5 miles off of your route of flight, your FMS will rat you out. The ADS report that we get is very accurate and, as Oceans13 mentioned, we can see exactly where you are and where you should be. Upon receipt of a Lateral Deviation Event report, most controllers will simply up link a weather deviation clearance with a time/position to rejoin by. There are a few of my co-workers who will first ask you if you are deviating but what's the point? We already know that you are.
Our response time to CPDLC requests is very low. Usually less then 2 minutes for a climb, even less for a deviation request. Your best bet is to ask before you deviate.
BTW, one of the other contract rates that we set up is a 20 minute periodic report. That means we get a position report every 20 minutes regardless of route. This is nice for the you guys because you can basically fly point to point and not have to fly specific routes. So if you wanted to go direct from 40W to point on the other side of our FIR, it shouldn't be a problem provided that there is no traffic for you at the time of your request.
Hope this helps.
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5 miles lateral alert with ADS? Gefore SLOPS came into play, I've had ATC come up and approve my 1 mile right of track out in the middle of the GAFA, (for those not familiar with the term, the "Great Australian F*** All", as in a long way from anywhere), just to let me know they know I'm not toolin' down the very middle of the airway.
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" Just wait for the daisy chaining of ADS-B data, it will be more acurate than radar and update real time."
The data from ads-c/b is only as accurate as your FMS. That doesn't necessarily make it more accurate than radar.
Furthermore not everyone is comfortable relying on the airframe to announce it's position, sometimes your better establishing this for yourself. Admittedly though, mid-Atlantic you don't have many options!
The data from ads-c/b is only as accurate as your FMS. That doesn't necessarily make it more accurate than radar.
Furthermore not everyone is comfortable relying on the airframe to announce it's position, sometimes your better establishing this for yourself. Admittedly though, mid-Atlantic you don't have many options!
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Humorous anecdote from one of our ex F/O's who recently joined The Intact Airline.
CPDLC failed and the other 2 (he was on line check) got quickly flustered about what to do next.
F/O duly said, well, we get a clearance like this, do position reports like that and listen on here to get weather.
Top marks all round apparently
Mind you, said chap had plenty of experience on the radio on last years Hajj
CPDLC failed and the other 2 (he was on line check) got quickly flustered about what to do next.
F/O duly said, well, we get a clearance like this, do position reports like that and listen on here to get weather.
Top marks all round apparently
Mind you, said chap had plenty of experience on the radio on last years Hajj
