Early this morning as I checked on Flightradar to see if AC835 from GVA to YUL had taken off, which it just had done, I noticed Tunis Air flight 202 to YUL was cruising not far to the northwest of Geneva. Several hours later, just before reaching YUL, AC835 is ahead of TU202 by four minuted. Using the "multiselect" option on flightradar, both flights followed the same air track except over Newfoundland where one slightly more to the west.

My question is how cruising speed is determined for each aircraft to cross the Atlantic thus producing such difference between a just airborne flight and another already at cruise level as described above ?

Thanks.

The North Atlantic and for that matter most oceanic routes, use what is known as Mach Number Technique. Suggest you Google that term amd see what you can learn.

Where they at the same level? I doubt it if they exited the track four minutes apart, but it could be factor. If at different levels, they could be at different Mach numbers.

GF

GalaxyFlyer wrote:

Where they at the same level? I doubt it if they exited the track four minutes apart, but it could be factor. If at different levels, they could be at different Mach numbers.

GF

Or they could have been at the same IMN with a different wind vector. If so, that one would have a different ground speed.

I believe with FANS 1A, and soon 2B, the RLatSM tracks will be down to 5 minutes longitudinal separation. This will include both ADS B in and out, ADS C, RNP 4 qualified aircraft. Far cry from the days of a sextant and Loran A:)

BravoOne wrote:

The North Atlantic and for that matter most oceanic routes, use what is known as Mach Number Technique. Suggest you Google that term amd see what you can learn.

Ok, I'll check that.

On flightradar I've found the following:

At 12:40UTC

TU202 (A332) FL360 / 426kts ahead of AC835 (A333) FL340 444kts over Wales & Irish Sea

At 15:30UTC

Same order and respectively at FL380 /460kts & FL370 / 440kts south of Greenland

At 17:15UTC just over Newfoundland shore

AC835 FL380 / 384kts a couple of miles ahead and about 35nm to the left of TU202 FL380 387kts.

SpaceshipDC10 wrote:

BravoOne wrote:

The North Atlantic and for that matter most oceanic routes, use what is known as Mach Number Technique. Suggest you Google that term amd see what you can learn.

Ok, I'll check that.

On flightradar I've found the following:

At 12:40UTC

TU202 (A332) FL360 / 426kts ahead of AC835 (A333) FL340 444kts over Wales & Irish Sea

At 15:30UTC

Same order and respectively at FL380 /460kts & FL370 / 440kts south of Greenland

At 17:15UTC just over Newfoundland shore

AC835 FL380 / 384kts a couple of miles ahead and about 35nm to the left of TU202 FL380 387kts.

Sorry but my imagination is not good enough to build that picture. Also suggest you Google "TrackWise) as it an excellent review of how the NAT works. It's a little out of date as it does not cover the RLatSM subject, but you will get the idea. The Youtube video is about an 1+20 long so make some time so you can absorb the information. Talking to the folks at Shanwick and they say a new video is just around the corner.

BravoOne wrote:

I believe with FANS 1A, and soon 2B, the RLatSM tracks will be down to 5 minutes longitudinal separation. This will include both ADS B in and out, ADS C, RNP 4 qualified aircraft. Far cry from the days of a sextant and Loran A:)

Something like that. It's hard to keep track of all the acronyms these days... dang MELs.

I gotta say, the other day it was great fun watching all the other aircraft on our away across the ocean. Above and below; fast and slow.

Different levels, different ground speeds explains it. AC was faster, likely due to either cleared MN or wind factor, likely a combination of both.

GF

Adispatcher wrote:

BravoOne wrote:

I believe with FANS 1A, and soon 2B, the RLatSM tracks will be down to 5 minutes longitudinal separation. This will include both ADS B in and out, ADS C, RNP 4 qualified aircraft. Far cry from the days of a sextant and Loran A:)

Something like that. It's hard to keep track of all the acronyms these days... dang MELs.

I gotta say, the other day it was great fun watching all the other aircraft on our away across the ocean. Above and below; fast and slow.

Very true. Unless you work to keep abreast of this "stuff" it gets lost in the weeds quickly. The North Atlantic Data Link mandates is well worth looking at as there are a lot lights in the end of that tunnel so to speak.

BravoOne wrote:

Adispatcher wrote:

BravoOne wrote:

I believe with FANS 1A, and soon 2B, the RLatSM tracks will be down to 5 minutes longitudinal separation. This will include both ADS B in and out, ADS C, RNP 4 qualified aircraft. Far cry from the days of a sextant and Loran A:)

Something like that. It's hard to keep track of all the acronyms these days... dang MELs.

I gotta say, the other day it was great fun watching all the other aircraft on our away across the ocean. Above and below; fast and slow.

Very true. Unless you work to keep abreast of this "stuff" it gets lost in the weeds quickly. The North Atlantic Data Link mandates is well worth looking at as there are a lot lights in the end of that tunnel so to speak.

I hope so. All of out trans-atlantic birds are fully compliant, but shit breaks. I would hate to cancel a trans-atlantic flight because the new rules say we need a set of binoculars to be legal.

I only ask for a better route validation tool in return.

Out of curiosity what is the minimum fuel on board for arrival on your 757's. 6000# CAVU and no ATC delays?

BravoOne wrote:

Out of curiosity what is the minimum fuel on board for arrival on your 757's. 6000# CAVU and no ATC delays?

Trans-Atlantic?

Adispatcher wrote:

BravoOne wrote:

Out of curiosity what is the minimum fuel on board for arrival on your 757's. 6000# CAVU and no ATC delays?

Trans-Atlantic?

Yes, westbound out of EGLL.

BravoOne wrote:

Adispatcher wrote:

BravoOne wrote:

Out of curiosity what is the minimum fuel on board for arrival on your 757's. 6000# CAVU and no ATC delays?

Trans-Atlantic?

Yes, westbound out of EGLL.

Probably 8.5 - 10 thousand pounds. Slightly more if arriving in the NY area.

Thanks...you guys are generous:)

Anytime.