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rjsampson
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Oceanic Clearances: Then and Now

Mon Jan 10, 2022 4:46 am

Curious about Oceanic Clearances. Based on what little I know, it consists of a departing waypoint, and an arrival point on the other side of the ocean. I'm aware that there are multiple tracks that vary in numbers, according to winds, etc. Best I can tell, there are waypoints en route (GPS no doubt. right?)

Is there any contact with controllers of any sort with all the new technology, besides ACARS?

So before GPS, how did this work? I'm guessing navigation was largely INS/IRS, with rudimentary FMCs. Did the same waypoints exist in that way? How about BEFORE INS/IRS (I think commercially they were first available on the first 747s). How would that have worked on aircraft like 707s, etc?
 
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Starlionblue
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Re: Oceanic Clearances: Then and Now

Mon Jan 10, 2022 6:13 am

Satcom does work for voice. But most comms is done via CPDLC (not ACARS). Controller–pilot Data Link Communications. ACARS is used for communications with your own company, not ATC, as well as for weather like D-ATIS.

Before GPS, it was INS, which would drift. Once an aircraft arrived within range of radio beacons on the other side, there'd typically be a hefty course correction to correct the drift, triggered automatically by the rather primitive FM which all of a sudden needed to get back on track.

Before INS, the old Sun Gun was used. AFAIK was also used to correct for INS drift in the earlier days.

The waypoints en route are typically not so much waypoints as lat/long coordinates.

I can't remember when but I believe once GPS became widespread lateral separation between tracks was decreased. In fact aircraft now navigate so precisely that you're allowed to offset one or two miles if you need to get out of the wake from an aircraft above and overhead.
 
bigb
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Re: Oceanic Clearances: Then and Now

Mon Jan 10, 2022 6:29 am

Usually oceanic clearance would be received via CPDLC and would need to confirm the track assignment with track message comes in the flight plan. The clearance time would give use a time of entry and Mach speed to fly. Sometimes they will off set aircraft to the right of track when the traffic was heavy crossing the Atlantic.

When established communication with Gander or Shanwick, we will contact them HF and do a SEL CAL check. Then CPDLC communication will be confirmed. ATC communication primary is CPDLC with HF as a backup. ATC and we have the ability to use SATCOM was well which I had to use over the polar route because we couldn’t reach Gander anymore and we were too far from Magadan.
 
GalaxyFlyer
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Re: Oceanic Clearances: Then and Now

Mon Jan 10, 2022 2:37 pm

Before GPS, in the ‘80s, it was mostly INS after that was in widespread use in the early ‘70s with the introduction of the 747. Most systems had a means of DME (TACAN) updating prior to the entry point and after landfall. Clearances were given by Gander or Shanwick Delivery by voice. It would begin about 200 nautical from Gander, getting in the queue for a clearance. I’d try to listen to those entering the NAT system at the same entry and write down their level to anticipate where we’d be on the crossing. There’d be a scatter of contrails or flashing lights of the planes on your track—INS drift made SLOP offsets unnecessary. We didn’t even think of them. All HF position reports done every 10 degrees, it’d sometimes take 10 minutes or more if everyone was trying make a report.

The mid to late ‘90s saw CPDLC clearances and reporting, GPS navigation accuracy and changed things. We got in the military GPS and RVSM in 1998, but still used HF reports, the silence was golden, there were crossings where we were the only ones on HF. One of my last trips, approaching Santa Maria in a Global. I think they had some confusion on our comms, as it was a short term leased Global, they come on HF. FO says can you handle that? Yup, just like the old days, write it all down, read it back.
 
GalaxyFlyer
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Re: Oceanic Clearances: Then and Now

Mon Jan 10, 2022 2:50 pm

The tracks are lettered, …,X, Y, Z eastbound; A,B,C… westbound.

Before INS, it was all Doppler, Celestial with a navigator doing the work. The old guys had some great stories of showing up in the south of England aiming for Scotland. I was in a fighter drag of F-100s going to Torrejon. I was just out of UPT, in the back seat of an F model. Pilot was an old KC-97 navigator and early F-4 pilot. He is using the ADF and a Consolan chart. Bill tells me we’re probably 80-100 miles north of the flight plan. Finally, he asked the tanker what their position looks like. “Right on track”. STG VOR comes up about 30 degrees to the right. OOPS, navigator bought the beer at the club that night.

CONSOLAN was sort of LORAN system, so navs used Cel, Doppler, LORAN combined depending on route and atmospheric conditions. The early C-5 had an IMU, a platform without a computer, so the only output was L/L, ground speed and drift angle.
 
RetiredWeasel
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Re: Oceanic Clearances: Then and Now

Mon Jan 10, 2022 3:28 pm

Early to mid 90's flew 727's out of Guam to various Asian destinations using Omega for navigation. Not quite as accurate as INS, but sufficient for the shorter legs outside of VOR/DME (maybe 3 hours?). Retired from NW in 2007 just before the merger flying 747's both classic and 400. None of these jets had GPS for navigation... Used INS and HF position reports over both oceans. The only CPDLC birds were the newer A-330s..
 
thepinkmachine
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Re: Oceanic Clearances: Then and Now

Mon Jan 10, 2022 7:28 pm

Oceanic clearances are still available on VHF. Shanwick (UK) still has a dedicated Oceanic Clearance Delivery frequency. Gander had one until recently, nowadays they issue clearances on domestic ATC frequency to whomever has no datalink. Most clearances come via ACARS.

I used to do HF reports as late as 2018 - our A330’s didn’t have SATCOM and HF datalink capability - so it was almost like good old days…

The gross-est Navigation Error I heard from my older colleagues: An IL-62 made a landfall over Portugal instead of Irleland, due to the navigator screwing up Omega (or Decca) readings…
 
FlapOperator
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Re: Oceanic Clearances: Then and Now

Mon Jan 10, 2022 8:04 pm

RetiredWeasel wrote:
Early to mid 90's flew 727's out of Guam to various Asian destinations using Omega for navigation. Not quite as accurate as INS, but sufficient for the shorter legs outside of VOR/DME (maybe 3 hours?). Retired from NW in 2007 just before the merger flying 747's both classic and 400. None of these jets had GPS for navigation... Used INS and HF position reports over both oceans. The only CPDLC birds were the newer A-330s..


I spoke with a retired TWA 74/1011 guy who talked about INS in terms of tens of miles.

I've routinely ferried aircraft with...less than capable FMSs where drift is measured in tenths.
 
FlapOperator
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Re: Oceanic Clearances: Then and Now

Mon Jan 10, 2022 8:06 pm

thepinkmachine wrote:
Oceanic clearances are still available on VHF. Shanwick (UK) still has a dedicated Oceanic Clearance Delivery frequency. Gander had one until recently, nowadays they issue clearances on domestic ATC frequency to whomever has no datalink. Most clearances come via ACARS.

I used to do HF reports as late as 2018 - our A330’s didn’t have SATCOM and HF datalink capability - so it was almost like good old days…

The gross-est Navigation Error I heard from my older colleagues: An IL-62 made a landfall over Portugal instead of Irleland, due to the navigator screwing up Omega (or Decca) readings…


I guess back in the day, the NAT controllers were happy when you showed in their sector. I guess the days before Eurocontrol/Shanwick/CPDLC/FANS etc. were exciting!
 
GalaxyFlyer
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Re: Oceanic Clearances: Then and Now

Mon Jan 10, 2022 8:29 pm

Anyone remember the old sets with 9 waypoints, so you were always adding waypoints, cross-checking entries. A great source of error. I used to shoot with a guy who sailed in the USCG Ocean Station ships. He said winters were “interesting”; lots of seasickness, cold meals, knocking off ice. They ship had a box to remain in and the box was divided into 4 sub-boxes. When a passing plane asked for a radar fix, it would be prefaced with the ship’s estimate of where it was in the box, upper left, lower left, upper right, lower right. When INS came along, the ocean stations would take a radar fix, ask the crew where the airliner was and then figure out where they really where. Ocean stations went away in the early ‘70s.

https://en.wikipedia.org/wiki/Weather_ship
 
GalaxyFlyer
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Re: Oceanic Clearances: Then and Now

Mon Jan 10, 2022 8:35 pm

RetiredWeasel wrote:
Early to mid 90's flew 727's out of Guam to various Asian destinations using Omega for navigation. Not quite as accurate as INS, but sufficient for the shorter legs outside of VOR/DME (maybe 3 hours?). Retired from NW in 2007 just before the merger flying 747's both classic and 400. None of these jets had GPS for navigation... Used INS and HF position reports over both oceans. The only CPDLC birds were the newer A-330s..


EA B727 crash in Bolivia wasn’t very thoroughly investigated, but the working theory was the crew didn’t disconnect the VLF/Omega on descent and didn’t change to VOR navigation. Our descent checklist’s first step was “LRN-Disconnected”; at the time all our LRN was VLF/Omega.
 
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LyleLanley
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Re: Oceanic Clearances: Then and Now

Mon Jan 10, 2022 8:45 pm

GalaxyFlyer wrote:
Anyone remember the old sets with 9 waypoints, so you were always adding waypoints, cross-checking entries. A great source of error


Always fun! Especially after passing waypoint 9 and you realize "I'll update the INS just after this AR..." wasn't the smartest strategy, as the aircraft makes an unexpected turn back towards waypoint 1. :idea:
 
RetiredWeasel
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Re: Oceanic Clearances: Then and Now

Mon Jan 10, 2022 9:28 pm

LyleLanley wrote:
GalaxyFlyer wrote:
Anyone remember the old sets with 9 waypoints, so you were always adding waypoints, cross-checking entries. A great source of error


Always fun! Especially after passing waypoint 9 and you realize "I'll update the INS just after this AR..." wasn't the smartest strategy, as the aircraft makes an unexpected turn back towards waypoint 1. :idea:


Believe those were the Delco Carousel's, at least at our airline. All the widebodies were upgraded to Litton-92's around the 1993 or 94 time frame.
 
GalaxyFlyer
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Re: Oceanic Clearances: Then and Now

Mon Jan 10, 2022 9:49 pm

RetiredWeasel wrote:
LyleLanley wrote:
GalaxyFlyer wrote:
Anyone remember the old sets with 9 waypoints, so you were always adding waypoints, cross-checking entries. A great source of error


Always fun! Especially after passing waypoint 9 and you realize "I'll update the INS just after this AR..." wasn't the smartest strategy, as the aircraft makes an unexpected turn back towards waypoint 1. :idea:


Believe those were the Delco Carousel's, at least at our airline. All the widebodies were upgraded to Litton-92's around the 1993 or 94 time frame.


Yes, we had Carousel INS, whirling steel. The USAF actually used those when they installed thd Collins FMS-800 in the 90s.

Speaking of waypoint #9, rumor had it a US airline once loaded the 9 waypoints, coasted out and didn’t load the the #1. At 20W, plane neatly and without the crew noticing, headed back to the old #0, which happened to be somewhere in Germany. Anyway, Shannon Radar picked up the old transponder code and asked the OAC what’s up with this guy. Big Oops there. Later, a guy named T. Allen McArtor investigated their operations, memorably quoted, “they volunteered for it”.
 
FlapOperator
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Re: Oceanic Clearances: Then and Now

Mon Jan 10, 2022 10:56 pm

GalaxyFlyer wrote:

Yes, we had Carousel INS, whirling steel. The USAF actually used those when they installed thd Collins FMS-800 in the 90s.

Speaking of waypoint #9, rumor had it a US airline once loaded the 9 waypoints, coasted out and didn’t load the the #1. At 20W, plane neatly and without the crew noticing, headed back to the old #0, which happened to be somewhere in Germany. Anyway, Shannon Radar picked up the old transponder code and asked the OAC what’s up with this guy. Big Oops there. Later, a guy named T. Allen McArtor investigated their operations, memorably quoted, “they volunteered for it”.


One good working theory for KAL007 overflying Soviet airspace was that KAL's SOP was have waypoint 9 be the destination, and 1 be the origin, and just keep rotating points 2-8. Anyway, if you draw a line from their loss of radar contact, its a straight line to GMP. That it matters when a PVO Strany guy is rudder hard over to jam a heater into you.

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