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Air France Descend Procedure


martinConcordeX

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martinConcordeX

there is 325, 350 and 380 knots for descent as the speed references for Air France so pick up the one you want.

I see, but why didn't BA use 380? As far as I know, this would have allowed to stay supersonic a little longer.

Regards,

Martin

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Fraser Gale

I've tried all three but tend to go back to 350 as per BA. I'm not sure if this is why they did it but for me, especially when flying back to London, I fly down through M1.00 as per the descent then use Mach hold at M0.95 to cruise in towards London. This usually equates to an IAS of 300kts or so (can't remember off hand but it's lower than 350kts) so when descending towards FL300 I let the Mach number decrease while the IAS increases and at 350kts I go back to holding that speed till I have to slow down for the approach.

I guess it's easier to always aim for one number instead of two different ones... Just me guessing though!

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Jean L. Leborne

...I see, but why didn't BA use 380? As far as I know, this would have allowed to stay supersonic a little longer.

Why ? Good question, I would say it's a matter of Company policy.
As a french ConcordeX virtual CdB "Commandant de Bord" I'm always using KIAS 380 for D&D. Stay supersonic as long as possible is the key word. When flying to JKF my D&D starts a few miles inbound KENDA instead of 60 NM in normal delta ISA conditions.
When you remember the r/w Concorde was sometimes (not that frequent) given priority landing clearance due to low fuel-load remaining, you realize D&D at KIAS 380 was clever idea...
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Pierre Chassang

Well knowing this topic Here is the reasons why.

Air France had three descent speeds:

If TOD was delayed or if a risk of bang carpet onto a protected zone, the procedure was the follow.

- 5 NM / 15 seconds delay: 325 kt was used.

- 10 NM / 30 seconds delay : 350 kt was used.

- 20 NM / 1minute delay : 380 kt was used.

- 60 NM / 3 minutes delay : emmergency speed (MMO) was used.

- At FL 418 the bird was leveled off without addinf thrust until it reach M1.0 (VLA 300 kt)

Then the descent was resumed at subsonic speed.

The procedure was not used to save fuel but only for ATC or anti noise purpose.

Cheers

Pierre

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Jean L. Leborne

The procedure was not used to save fuel but only for ATC or anti noise purpose.

To save fuel ? Pierre, with all respects did I say that ?
Would you please read again what I wrote : " When you remember the r/w Concorde was sometimes (not that frequent) given priority landing clearance due to low fuel-load remaining, you realize D&D at KIAS 380 was a clever idea..."
In other words, It could have been a way to save fuel...
Anyway, thanks Pierre for clarifying with your Concorde expertise.
Do you remember how extremely difficult it was to convince NY Port Authorities about Concorde landing JFK ? Long story to tell...
But both UK and France did it, and Concorde was in "commercial service" for 27 years long, as the unique SST.
A long an very hard battle that makes Concorde THE aircraft she is for ever :rolleyes::rolleyes::rolleyes:
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Fraser Gale

I have heard from friends of mine that AF Concorde's managed to boom the edges of the English Channel on more than one occasion, so perhaps those were the times they used the wrong procedure...

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Jean L. Leborne

Air France had three descent speeds:

If TOD was delayed or if a risk of bang carpet onto a protected zone, the procedure was the follow.

Why TOD would be delayed ? ATC ? Failure ? Crew in charge ? Don't see any valuable reason to delay TOD. Strange enough !
And BTW, I'm still searching for a sonic boom protected zone over the Atlantic in the KENDA area...
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Pierre Chassang

Hello Captains,

Concorde was not only flying CDG/LHR to KFK, somtimes her got back and flown other destinations...

The procedure was at Captain's / ATC discretion.

Cheers

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Andrew Wilson

I have heard from friends of mine that AF Concorde's managed to boom the edges of the English Channel on more than one occasion, so perhaps those were the times they used the wrong procedure...

You could hear Air France dropping the sonic boom on southern England every Sunday afternoon at 4pm in the winter months. It wasn't loud - but enough for people to notice it. Of course, most people had no idea what it was.

I'm curious as to why it only occurred on a Sunday - was this the scheduled JFK-CDG, or a returning flight from somewhere else that only ran on Sundays?

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Fraser Gale

I'm curious as to why it only occurred on a Sunday - was this the scheduled JFK-CDG, or a returning flight from somewhere else that only ran on Sundays?

Maybe this was the day the management captains chose to fly and they tend to have less hours practice...

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Fraser Gale

Another suggested reason for BA sticking to 350kt procedure:

They used fixed descent points that were adjusted by the crew for the wind and temperature of the day. Shanwick and London control were aware of this and I would think made sure that clearance was more often than not provided when required.

Perhaps rather than changing the descent point AF changed the speed to adjust for conditions of the day? I'm not convinced this would be as accurate however.

Plus, even flying Concorde X you tend to get a feel for the descent using 350kts to the point I'm usually within 1 mile of the point I was aiming for - I can't do this with the other two speeds because I don't have the same "feel" for them. This is the main reason I stick to the one procedure - might have been BA's reason too!

All just my opinion,

Frazz

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Ray Proudfoot

You could hear Air France dropping the sonic boom on southern England every Sunday afternoon at 4pm in the winter months. It wasn't loud - but enough for people to notice it. Of course, most people had no idea what it was.

I'm curious as to why it only occurred on a Sunday - was this the scheduled JFK-CDG, or a returning flight from somewhere else that only ran on Sundays?

The aviation equivalent of Weekend drivers!!! :)
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Jean L. Leborne

I'm curious as to why it only occurred on a Sunday - was this the scheduled JFK-CDG, or a returning flight from somewhere else that only ran on Sundays?

Maybe our former president FM taking good time with his daughter unknown for a large majority of french "citoyens" except parisian intelligentsia, or someone else... who knows ? FM has been travelling a lot with AFConcorde and PNT "réquisitionnés pour la circonstance" ;););)

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Jean L. Leborne

They used fixed descent points that were adjusted by the crew for the wind and temperature of the day

wind ? don't think so

delta ISA ? YES

The procedure was at Captain's / ATC discretion.

et voilà CQFD !

Saving fuel could have been one of the reasons to choose KIAS 380 for D&D inbound to JFK. And saving fuel is always a very good idea, a fortiori flying a plane with the so-called VIP payload on board...

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Fraser Gale

Wind did affect the descent as you were also slowing down into different winds. The slower you fly the more effect a head or tail wind has and therefore it would affect the descent point.

Plus wind components were used for the cruise phase during flight planning although they had a lesser effect than that for subsonic aircraft.

Head wind means you won't get there as quickly so you can slow down later, tail wind means you will get there quicker so you must descend earlier.

Frazz

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martinConcordeX

Another suggested reason for BA sticking to 350kt procedure:

They used fixed descent points that were adjusted by the crew for the wind and temperature of the day. Shanwick and London control were aware of this and I would think made sure that clearance was more often than not provided when required.

Perhaps rather than changing the descent point AF changed the speed to adjust for conditions of the day? I'm not convinced this would be as accurate however.

Plus, even flying Concorde X you tend to get a feel for the descent using 350kts to the point I'm usually within 1 mile of the point I was aiming for - I can't do this with the other two speeds because I don't have the same "feel" for them. This is the main reason I stick to the one procedure - might have been BA's reason too!

All just my opinion,

Frazz

Sorry for the confusion, but I thought both AF and BA had fixed waypoints where they had to be at or below Mach 1. It's still unclear to me why they would different speeds?!

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Fraser Gale

It was probably in the manual even if they didn't use it, although I can't confirm as I don't have a copy.

The rough guide for descent (up to ISA +5 and with wind component) table for 350kts was printed in the normal checklist if I remember correctly.

Not sure but I think descent tables were part of the cruise control manual rather than performance, but I am probably wrong.

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Fraser Gale

Sorry for the confusion, but I thought both AF and BA had fixed waypoints where they had to be at or below Mach 1. It's still unclear to me why they would different speeds?!

Unless a Concorde crew member reads this and answers you, I'm not convinced we'll ever know!

Frazz

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Ray Proudfoot

Unless a Concorde crew member reads this and answers you, I'm not convinced we'll ever know!

Frazz

I'm visiting the Concorde Brooklands simulator in April. Two ex-Concorde pilots will be our hosts for the day. If you want me to ask a question please post it here and I'll do my best to get an answer for you.

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Fraser Gale

I'm visiting the Concorde Brooklands simulator in April. Two ex-Concorde pilots will be our hosts for the day. If you want me to ask a question please post it here and I'll do my best to get an answer for you.

Enjoy Ray! I have been twice and they treat you brilliantly.

Last time I had Terry Henderson and Steve Bohil-Smith, although it was Terry that took me flying. He was lovely and we had some great fun and realising I am a true Concorde nut case, he spent over an hour with me after the session had finished discussing the good old days.

I've also met Ian Smith and Ian F. Smith. Ian F. smith is a fellow Scotsman so I think they gave me him the first time in case we needed a translator...haha.

I should say that I save up for a while and pay to have an hour on the sim as travelling down from Scotland isn't worth 15 or 30 mins and they gear what they do to your abilities etc. In fact with Terry the last time he basically said "what do you want to do, we can do anything you like" but that was the luxury of having an hour.

Anyway this is a bit off topic but for anyone else ready, get yourself to Brooklands and fly the real thing, you'll learn a lot and have a great time and I would say you should do it soon as like the rest of us the most experienced and knowledgeable people aren't getting any younger!

Frazz

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Jean L. Leborne

It's still unclear to me why they would different speeds?!

It is clear, Concerning AF Pierre gave you the answer (pond xing to JFK) :

"The procedure was at Captain's / ATC discretion."

BA is BA and AF is AF, both with different D&D proc. even flying with the same recognized brio the same SST Concorde.

BA was starting D&D at approx 60NM inbnd KENDA at constant KIAS350, AF was doing the same maneuver but flying supersonic a little bit longer before starting D&D at constant KIAS 380.They were both under ATC radio contact while doing such a maneuver.

"C'était ainsi, rien de plus à ajouter. Nul besoin de se torturer l'esprit au sujet du pourquoi du comment ?"

PS :

Why do they drive on the left side in UK ?+ some other ex-Commonwealth countries ?

Why do we drive on the right side in France ? + some other ex-Colonies countries ?

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You could hear Air France dropping the sonic boom on southern England every Sunday afternoon at 4pm in the winter months. It wasn't loud - but enough for people to notice it. Of course, most people had no idea what it was.

I'm curious as to why it only occurred on a Sunday - was this the scheduled JFK-CDG, or a returning flight from somewhere else that only ran on Sundays?

Andrew,

that is a long time ago and i cant remember the exact time but i when was in Pangbourne sp? Berkshire and there was a boom everyday and the inhabitants with a lot of people working for BAW or Heathrow airport there said it was concorde ...

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Ray Proudfoot

Andrew,

that is a long time ago and i cant remember the exact time but i when was in Pangbourne sp? Berkshire and there was a boom everyday and the inhabitants with a lot of people working for BAW or Heathrow airport there said it was concorde ...

Pangbourne is 24 miles west of Heathrow and under Concorde's flight path. There is absolutely no possibility it could reach Mach 1 in that distance. They have a very active imagination! :rolleyes:

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