racingmars

Initial cruise altitude 16,000 feet?

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Hi folks,

I'm getting odd behavior (at least I think it's odd) when planning a flight in the 747-400 from CYVR to RCTP. It's happening in PFPX (using the default 747 profiles as well as the FlyPrecisely profiles) and SimBrief, which is what's making me curious...I don't think it can be attributed to a bug in a particular flight planning tool.

In any case, when I plan my flight out of Vancouver, both flight planning tools give me an initial altitude of 16,000 feet. Then after a very short while, they plan a climb up to what I'd expect the initial cruise to be, to FL300 or FL320. I can use FL300 as my initial altitude when setting up the FMC and the 747 climbs to it just fine, of course. I just don't recall ever seeing a similar low cruise for a very brief time when planning flights.

The route I'm using is pulled from a recent China Airlines Flight 31:

YVR.V317.TREEL..QQ..NUDGE..51N140W.52N150W.51N160W.51N170W..ADK.R451.OGDEN.R580.ONEMU..NANNO..ALICE.Y111.MQE.Y124.GTC.Y45.KMC.Y382.WAKIT.Y282.POPPY.Y34.SUKMO.Y50.IGMON.A1.DRAKE.DR1B

ZFW is 225,000kg and the release fuel load ends up being between 135-145kkg depending on the tool/profile I use, but in all cases the initial cruise is 16,000 feet. PFPX gives me a climb to FL320 at TREEL, and SimBrief gives me a climb to FL300 at QQ. Both of which are mere minutes after reaching the initial 16,000 cruise. The subsequent step climbs from both tools are then 2,000 feet at a time spaced out over several hours between each climb, as I'd expect.

So my question is, does anyone know what the explanation for the initial 16,000 feet segment is? Is there some operational consideration that the tools are taking into account that I'm not aware of? Airspace restrictions that the tools are somehow taking into account?

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Hi,

Have you checked the max flight altitude of the first airway V317? I don't have charts at hand reach to check myself but it could be one reason for the initial altitude to be that low.

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It starts you on a victor airway. I don't believe these are necessarily always flown this way on real life, but by definition that's a low altitude airway with altitudes <FL180. Your climb is right after leaving that airway. PFPX is just being a perfect stickler for rules. 

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Ah, yep, the victor airway was the piece of the puzzle I was missing! Going direct YVR to TREEL instead of via V317 gives me the initial cruise I expect. Thanks guys!

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You don't have to remove the airway in PFPX. It's possible to solve this issue by changing "Cruise Altitude/FL" in PFPX from OPEN to OPEN OPT. 

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I would simply disregard what PFPX is telling you and set up the FMS they way you want. On climbout from YVR, departure would assign you 16,000 as that is the top of Terminals airspace. You would never stop there though as you would be handed off to an enroute sector or QQ MTCA and given higher.

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Hi,

28 minutes ago, voske said:

You don't have to remove the airway in PFPX. It's possible to solve this issue by changing "Cruise Altitude/FL" in PFPX from OPEN to OPEN OPT. 

If you first leg is limited to 18000ft or less, 16000ft in this case, you should be prepared to and expect the possibility to have to level off at that altitude until the end of the airway and therefore should keep it in your flight plan for fuel calculation. The lower you are the most fuel you consume.

It may not be of a great difference but for the sake of accuracy, I would not get rid of it in PFPX. 

It would be better to plan for another route instead without that limitation.

If ever for some reason the ATC doesn't allow you to climb higher, then you may end the flight with less fuel than expected. Off course it depends on the length of the leg.

 

 

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Not as bad as some out of Heathrow that keep you at 6000ft (!) for quite some way out to keep you under the arrivals path.

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1 hour ago, Budbud said:

If ever for some reason the ATC doesn't allow you to climb higher, then you may end the flight with less fuel than expected.

Realistically Romain, this is highly unlikely and falls into the contingency category for fuel management.  ATC is always eager to get you as high as possible if for no other reason than to hand you off to someone else.  They get points for traffic count, not for how long they own the traffic.

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3 hours ago, 77west said:

Not as bad as some out of Heathrow that keep you at 6000ft (!) for quite some way out to keep you under the arrivals path.

All the Heathrow SIDs stop at 6000ft but you will never fly it: ATC will always vector you off the SID once you are above 4000ft (for noise monitoring) and give a higher level. 

The recent truncation of the SAM and DVR SIDs was for fuel saving reasons: airlines had to flight plan for remaining at 6000ft all the way to SAM/DVR, even though it never actually happens. So by truncating the SID to GASGU/GOGSI/DET you don't have to plan to remain at 6000ft for as long, thus saving a few hundred kilos of fuel a pop.

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4 hours ago, skelsey said:

All the Heathrow SIDs stop at 6000ft but you will never fly it: ATC will always vector you off the SID once you are above 4000ft (for noise monitoring) and give a higher level. 

The recent truncation of the SAM and DVR SIDs was for fuel saving reasons: airlines had to flight plan for remaining at 6000ft all the way to SAM/DVR, even though it never actually happens. So by truncating the SID to GASGU/GOGSI/DET you don't have to plan to remain at 6000ft for as long, thus saving a few hundred kilos of fuel a pop.

Thats good to know; unfortunately my last few trips on Avsim out of EGLL this was not the case (not vectored off the SID) but that was a while back IIRC. I figured in the real world they probably didn't keep a flight a 6K all that long much like the ?OP's 16K example.

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1 hour ago, 77west said:

Thats good to know; unfortunately my last few trips on Avsim out of EGLL this was not the case (not vectored off the SID) but that was a while back IIRC. I figured in the real world they probably didn't keep a flight a 6K all that long much like the ?OP's 16K example.

I assume you meant VATSIM. I think part of the problem is that people don't fully understand how the procedures work. This isn't any different from the rule of flying 250 knots below 10,000 feet, where people expect you to do it, when in reality, if you're really heavy on departure, you can fly minimum clean speed if it's above 250 knots.

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On 7/1/2017 at 1:57 PM, racingmars said:

YVR.V317.TREEL..QQ

This is a canned routing used coming out of CYVR.  What will normally happen is the aircraft will be assigned a SID by CLR with an initial altitude of 70 with radar vectors to a point along the initial routing.  I would expect dispatch to flight plan to my initial cruise altitude.  

Low altitude airways can be assigned by ATC into the Flight Levels by using the term "cleared via the radials of V317" as a example.  

blaustern  

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14 hours ago, Captain Kevin said:

I assume you meant VATSIM. I think part of the problem is that people don't fully understand how the procedures work. This isn't any different from the rule of flying 250 knots below 10,000 feet, where people expect you to do it, when in reality, if you're really heavy on departure, you can fly minimum clean speed if it's above 250 knots.

Yes, I meant Vatsim. And yes, I agree on what you say, a lot of controllers don't seem to know that rule, although some sneaky pilots try to pull it off in a 737. Really only the 747 and 777-300ER should need to. Perhaps the A340 as well?

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26 minutes ago, 77west said:

Yes, I meant Vatsim. And yes, I agree on what you say, a lot of controllers don't seem to know that rule, although some sneaky pilots try to pull it off in a 737. Really only the 747 and 777-300ER should need to. Perhaps the A340 as well?

Watching a video on YouTube of the Lufthansa MD-11 that went around the world in 66 hours, looks like the MD-11 would have the same issue. I would imagine a lot of heavy jets would need to do it.

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Just now, Captain Kevin said:

Watching a video on YouTube of the Lufthansa MD-11 that went around the world in 66 hours, looks like the MD-11 would have the same issue. I would imagine a lot of heavy jets would need to do it.

Yes I forgot about ye olde MD11. I don't think we would see an A300, A330, B767, B787 or even A380 need to go above 250 clean though; seems to be more of an issue on the really highly loaded wings. I may be wrong.

All off topic of course! :biggrin:

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It's been a long time, but I am almost certain that min clean on the B767 at/near MTOW was in the region of 260 kt +.

Incidentally, it's probably also worth noting that the 'rule' is only actually law in the USA: in the rest of the world it is at best an ATC restriction and as such can be (and regularly is) lifted by a controller.

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52 minutes ago, skelsey said:

It's been a long time, but I am almost certain that min clean on the B767 at/near MTOW was in the region of 260 kt +.

Incidentally, it's probably also worth noting that the 'rule' is only actually law in the USA: in the rest of the world it is at best an ATC restriction and as such can be (and regularly is) lifted by a controller.

https://www.ivao.aero/training/documentation/books/APC_Aircraft_perf.pdf

Page 5. Poor 767 is not even listed. I expect it would fall into the "heavy liner" block. I wonder what Concorde was?

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54 minutes ago, 77west said:

https://www.ivao.aero/training/documentation/books/APC_Aircraft_perf.pdf

Page 5. Poor 767 is not even listed. I expect it would fall into the "heavy liner" block. I wonder what Concorde was?

Those look more like clean speeds for approach rather than departure. Departure clean speeds are going to be much higher with the planes being heavier.

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On 7/2/2017 at 6:19 PM, 77west said:

 I wonder what Concorde was?

I was under the impression that when a Concorde was departing, they were allowed to accelerate up to around 300 knots with all speed restriction waived. 

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3 hours ago, Milton Waddams said:

I was under the impression that when a Concorde was departing, they were allowed to accelerate up to around 300 knots with all speed restriction waived. 

That's not limited to the Concorde.  Officially, the 250kts/10,000' restriction applies to all aircraft.  But it is virtually standard that ATC will wave this for heavy aircraft, clearing them to their minimum clean speed.  Otherwise, more than a few heavy 747, 777, etc would have to fly with the flaps out up to 10,000' with a big hit in noise and performance/fuel consumption). 

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10 minutes ago, ESzczesniak said:

That's not limited to the Concorde.  Officially, the 250kts/10,000' restriction applies to all aircraft.  But it is virtually standard that ATC will wave this for heavy aircraft, clearing them to their minimum clean speed.  Otherwise, more than a few heavy 747, 777, etc would have to fly with the flaps out up to 10,000' with a big hit in noise and performance/fuel consumption). 

Concorde was given special privileges though due to the characteristics of that aircraft. Most heavies, as stated above, will fly at clean speed with acceleration past 10,000, bar any limiting factors. Concorde had the privilege of accelerating to basically whatever speed was determined to be required by the pilots. Most heavies have to fly to 10,000 at clean speed and not past.

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