View Full Version : CPDLC - Can you see them ?
6th Feb 2006, 16:54
So, if ACARS, CPDLC, whatever this week's wonder thing that we won't ever get is called sends out information on a regular basis, are we at a stage where Shanwick/Gander/Santa Maria/New York can 'see you' on a pseudo radar screen ?
I remember when we started ETOPS on the 757 through Bangor - Oh, those were the parties - that there was an experimental radar at bangor that claimed huge range - what happened to that ?
6th Feb 2006, 17:17
I don't know if it is directly derived from CPDLC data, but there is a great display on the Flow Management desk at LACC. It shows the North Atlantic, and is populated with lots of arrows in different colours. These are symbols for each aircraft crossing the Atlantic, and you can interrogate the symbols for FPL and altitude data. When the core Oceanic flow is happening, it is the best grphical display of the track structure in practice.
6th Feb 2006, 20:52
In addition to the good post from eyeinthesky, we can see you about 150 miles west of Shannon by winding out the range on our conventional radar at Swanwick. The advance picture can be a useful guide on the need to carry out short-term tactical re-routes, or whether to open up another sector.....although we will already have a good idea of the track loadings several hours before that [from flow control].
7th Feb 2006, 03:44
In the US we are deploying ATOPS which gives a radar like view of aircraft with some automated conflict probes.. It is however NOT radar.
As to the long range radar you speak of, it was run by the Air Force and called Pave Paws. Due to cost, it was run part time for many years by the Air National Guard. I have lost track on if it is still in use or not due to cost issues and the demise of the USSR and the percieved threat being gone.
7th Feb 2006, 08:23
Thanks for the quick replies, particularly about the long range radar. Problem is you will now have to send the boys round to silence me no doubt :eek:
The new kit due to be in place at Shanwick later this year, (Gander sometime after that), will eventually be hooked up to an ADSB feed and will provide a pseudo radar picture enabling the controllers to 'see' your actual position on the basis of data received directly from the aircraft, as opposed to an approximate position calculated and displayed by the flight data processing ATC computer.
ADS at the moment provides controllers with waypoint position reporting as significant route points are crossed during the oceanic en-route phase. (Or when a change is made by the crew to the FMS). Position information can also be sent by the FMC, depending upon the set up of the aircraft itself. CPDLC position reports, as with ADS and FMC, only contain the LAT/LONG and ATA/ETA for the position. Some ATC centres are not set up to use CPDLC position reports and only use CPDLC to request changes in FL or Mach.
ADS and FMC position reports will tell controllers when you reach a particular route point stored in the FMS. ADS will also generate a report at an intermediate point should you alter the route held in the FMS. CPDLC will send a position report for your actual position at the exact time you send it. ADSB will send a series of reports at specific time intervals giving a constant update of your position every 30 seconds/2 minutes/5 minutes or whatever the downlink period is set to.
ADSB will enable Oceanic and other areas, for example parts of Australia and the Arctic region amongst others to employ separations similar to those of radar sectors without the need for ground based radar systems.
However, the accuaracy of the ATC systems such as the new one for Shanwick are such that controllers can pretty well 'see you' as things stand, without ADSB.
Hope this helps.
8th Feb 2006, 08:51
That means no more 'speeding' betwen waypoints then :E
8th Feb 2006, 10:32
You guys are soooo behind the times.
In Oz we've got CPDLC and ADS. Had it for quite some years. On our ASD (air situation display) circles are SSR tracks, + signs are primary paints, squares are flight plan tracks, triangles are ADS tracks, and soon we'll have ADS-B tracks all over Oz down to F300.
Our ASDs can have all or any combiation of these tracks at any time. Mostly outside radar coverage, we'll be using either flight plan tracks or ADS tracks. this would be over our oceanic and trans-continental airspace sectors.
I believe NY oceanic sectors use a similar system as does NZ.
Oz also has a long range radar (Jindalee), which is not a secret. What we use it for, is however. It is a military installation not civilian and not used by ATC.
9th Feb 2006, 00:05
Are You using the ADS-tracks for seperation? What is the required seperation in NM's?
I still think the ADS is very inaccurate, (For actual seperation) depending on how often you get a position report from the aircraft. Do You know what the price for one position update is? I've been told it was expensive... :\
9th Feb 2006, 11:41
Are You using the ADS-tracks for seperation? Yes.
What is the required seperation in NM's? I'm going to have to look that up, as the sectors I work on are radar sectors and we don't use ADS. I do know that by "one shotting" the ADS track (that's getting a current position) you can determine, using ADS, if the aircraft is outside a lateral separation point. I did use this when I last worked on a procedural sector with large amounts of oceanic and trans-continental airspace.
ADS is reportedly more accurate than radar as it gives the actual aircraft position as reported by the aircraft's GPS/RNAV positioning system. Radar has of course slant range and other inaccuracies.
As to the expense of ADS, I'm just a controller. Ask the bean counters at the airlines that question.
As for a simplified ADSB technical overview visit http://www.flyadsb.com/techoverview/techoverview.htm (i think its an faa site). Basicly ADSB transmissions happen around once a second and there doesnt seem to be any extra cost attached.
I know over here in germany we are required to equip all commercial airplanes with Mode-S transponders in the "Advanced Surveillance" mode which transmits a lot of data, for example position (sic!), track, heading, altitude, rates, selected altitude (you can then see what we preselect and correct us), callsign etc. With that part of Mode-S you can basicly get airplane derived position as well and use that instead of radar calculated which is similar to how ADSB works.
11th Feb 2006, 18:47
It's easy to upgrade when you don't have much to upgrade :}
12th Feb 2006, 03:19
would you need ADS or CPDLC at Fort Worth? Sounds like you just need to upgrade the current radar you've got and get into a electronic strip system like eurocat 2000.
13th Feb 2006, 20:03
Actually we have electronic flight info and have had for awhile. We have plenty of radar info too, but it would be nice to have upgraded primary, as the secondary is already upgraded. But the FAA's plans are for us to go to ADS-B within 10 years. But it is just a plan, and hasn't been approved yet. I see a large fight looming with it.
13th Feb 2006, 21:57
Are You using the ADS-tracks for seperation? What is the required seperation in NM's?
In the Oz procedural sectors we use can ADS for separation. Same direction we need 50 nm, opposite direction we need 50 nm. There are other conditions - for example, both aircraft RNP 4/10 and in RNP 4/10 airspace, not too much closing, minimum reporting rates (conracts) may need to be set up between our Flight Data Processor and the ADS/FMS,etc.
We can also "one shot" an aircraft out of lateral conflict with another by a single position report from said aircraft's ADS. If the symbol highlights on the safe side of the conflict area then wammo! Seperated!
I think (but not sure) in Oceanic areas the distances can be reduced to 30 nm. Would need to check.
Hope it helps, Beefy...
14th Feb 2006, 09:22
Are your electronic strips integrated with your air situation display so when you manipulate the labels it changes the info in the strips and vice versa? Or are you still using paper flight progress strips?
Only approach in Oz uses primary (mainly to stop VCAs), everywhere else has secondary and soon ADS-B. If you're at an approach unit you still need that primary turning and burning.
16th Feb 2006, 10:07
Question for Dirty Pierre or other Oz:
On our ASD (air situation display) circles are SSR tracks, + signs are primary paints, squares are flight plan tracks, triangles are ADS tracks, and soon we'll have ADS-B tracks all over Oz down to F300.How are your circles, squares, triangles and +signs displayed ? Are they all overlapping as the case may be, or is there a hierarchy of data-sources which suppresses the signs considered to be of lower quality. If the latter, what is the rule, which data source has higher quality ? Reading the next quote I would presume ADS ?
ADS is reportedly more accurate than radar as it gives the actual aircraft position as reported by the aircraft's GPS/RNAV positioning system. Radar has of course slant range and other inaccuracies.But why then would you need 50NM separation when the data source for the position is ADS, as I understand from the message of Captain Beef.
17th Feb 2006, 00:00
is there a hierarchy of data-sources Yes.
An SSR return is a circle. Primary return is +. If you have both, then the + is inside the corresponding SSR return. Other than this you will only see one symbol. Hence there is a hierarchy. SSR/PSR, ADS-B, ADS, Flight Plan track.
But why then would you need 50NM separation when the data source for the position is ADSYou need the 50nm separation because of the delay in receiving the information from the aircraft. It can take up to a few minutes to get the request (one shot) to the aircraft and for the aircraft to send a response. The controller could be sitting in Melbourne or Brisbane, and the aircraft up to 10hrs flight time away across the other side of the airspace. Remember Oz controlls a lot of oceanic airspace where the ADS comms are by satelite.
The controllers air situation display then provides a computer extrapolated position for where the aircraft should be based on the aircraft's response.The ASD provides an updated position every few minutes (which is also computer extrapolated) without the aircraft actually sending it's position information.
The aircraft automatically sends it's position info over every position report, and also at 30 minute intervals (ADS contracts for position reporting depend on where the aircraft is eg. off track, oceanic, under radar, etc). So the position of the aircraft displayed to the controller is accurate to a degree The separation standard has added significant buffers for safety. Remember, outside VHF coverage these aircraft are also communicating by HF or CPDLC which takes time to process by controller and/or pilot.
ADS-B is intended for use with mainly aircraft in VHF coverage.
Hope this helps.
17th Feb 2006, 09:41
Many thanks Pierre, now the pieces of the puzzle have come together.
18th Feb 2006, 02:51
Whoops! I should have made myself more clear!
Indeed, 50 nm separation standards are used when aircraft have ADS-C (contract), as opposed to ADS-B (broadcast). When the rollout of ADS-B is complete - we should have the ability to use a lateral separation of just 5 NM between two ADS-B equipped aircraft.
This is possible, because unlike ADS-C, where postition reports are made either every 30 minutes (or another time interval set by the controller, or over a waypoint, an ADS-B unit transmits it's position every 1/2(?) a second.
There, hope I haven't made it more confusing again :\ .
21st Feb 2006, 04:02
Sorry this took so long, I have been rather busy of late...
Yes our URET display which has a conflict probe on the assistant side also does all of our aircraft flight info and such. It allows us to change speeds and put in headings as well as make changes to the flight plan, and the speeds and headings will show up on the radar as will any altitude changes. They are all tied together. We can also do free style text to put in the fourth line of the data block that will pass from sector to sector as well as center to center. It will however not pass to approach controls. We have to do that the old fashion way <G>. As to paper strips, we have them available in the event that we go non radar, but we only are supposed to use them for non radar and for departures and arrivals at airports that we serve, however the truth be told, we don't use it for that either. We are pretty much stripless. I wish that I could attach pictures.
25th Feb 2006, 02:25
It's all sounds pretty cool Scott. Better than that stuff they used on "Pushing Tin".