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Since updating to the latest update for the 400 I have noticed that setting my descent altitude on the MCP well before hitting T/D the aircraft doesn't start descent via the VNAV profile. I haven't changed the way I set up my flight planning and everything is correct. To initiate the descent I have to manually start descent via the VS dial, wait until the aircraft is about 500 feet below the T/D altitude and then hit VNAV, that is the only way I can get VNAV to activate and control the descent. The speed is decreasing and going below set speed but with no change in altitude. Has anyone else noticed this or is it just an issue on my side? 

VNAV works as it should during climb out and cruise, its just the initiation of the descent phase where it seems to be having difficulty. 

Just to note - I have only experienced this on the 400 as I haven't flown the -8 yet with the latest update. 

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What does the FMA say before and after the TOD point?

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1 hour ago, shamrockflyer said:

Has anyone else noticed this or is it just an issue on my side? 

Three flights in. No issue.

I'm with Dan - need more info.

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I flew in VNAV to GS intercept with the last build before release.... many VNAV descents before that... FMAs are your friend...

C

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Ok - after doing another test flight to see if the issue would arise and it didn't. Aircraft descends as per usual and there are no issues to report in regards to TOD. I know this doesn't fully answer any of your questions, but if I get a chance to reproduce the issue in the coming days then I will report back here with details. I may possibly be able to do a flight tomorrow, I will report back when I can. 

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Had you put a lower altitude into the MCP for the Autopilot to start descending to before TOD? 

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1 hour ago, Tony747-400 said:

Had you put a lower altitude into the MCP for the Autopilot to start descending to before TOD? 

Yes I had as always. The same issue happened with two flights I had done in the past two days. I am now performing a flight of equal flight time to my previous flight and will report back with what the FMA says before and after TOD, hopefully the issue will repeat itself and I can get some information together. 

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Posted (edited)

Depending on your cost index it can be that the airplane will first reduce speed approaching the ToD before actually decending. I had this happen into Vienna once and was surprised by that behaviour too. However as the airplane remained in VNAV PATH and the path indication on the ND was centered even after passing TOD and without decending I waited for the plane slowing from 320kias or so to 240kias... then it took the nose down.. 

maybe a 747 pilot can acknowledge this... 

Edited by Ephedrin

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4 hours ago, Ephedrin said:

Depending on your cost index it can be that the airplane will first reduce speed approaching the ToD before actually decending. I had this happen into Vienna once and was surprised by that behaviour too. However as the airplane remained in VNAV PATH and the path indication on the ND was centered even after passing TOD and without decending I waited for the plane slowing from 320kias or so to 240kias... then it took the nose down.. 

 

I think this was what I thought was an issue, as it turns out it seems to just be normal behaviour of the aircraft. Descent into Sydney in the 400 went smoothly without a "hitch". I guess this thread was mainly created because of lack of patience in terms of waiting to see what the aircraft would do in the situation that occurred. 

This thread may be marked as solved, as stated above it was just a user "error" rather than software. 

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On 1/8/2019 at 5:24 PM, Ephedrin said:

Depending on your cost index it can be that the airplane will first reduce speed approaching the ToD before actually decending. I had this happen into Vienna once and was surprised by that behaviour too. However as the airplane remained in VNAV PATH and the path indication on the ND was centered even after passing TOD and without decending I waited for the plane slowing from 320kias or so to 240kias... then it took the nose down.. 

maybe a 747 pilot can acknowledge this... 

Not a real 747-driver, but i can confirm this behaviour on my side...

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On 1/8/2019 at 4:24 PM, Ephedrin said:

cost index

Talking of CIs, Marc, is there a place I can source to get CIs for different 747 operators?

I usually use a vague to-of-the-head 41, and has worked for me on all my Atlas Cargo flights, but am not that certain if this figure is right or is it just pot luck?

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2 hours ago, vc10man said:

Talking of CIs, Marc, is there a place I can source to get CIs for different 747 operators?

I usually use a vague to-of-the-head 41, and has worked for me on all my Atlas Cargo flights, but am not that certain if this figure is right or is it just pot luck?

I've tried to find some real CIs but only found pages with completely outdated information. Normally I use Simbrief to give me a good value and sometimes I choose it myself. for example if I do a trans oceanic flight I go for a high CI as it speeds me up rather quickly to save time before fuel as I can save fuel later by choosing a good and favourable flight level. However when I do regional flights with the 737 or A320 I mainly prefer CIs from 5 to 30, depending on terrain, population (noice) and such things. But for 747 operation I typically would use around 50-80 for "shorter" flights and up to 300 for intercontinental, depending on the wind. But I am really no expert for airline economics 😄

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Thanks for great reply, Marc. I definitely will use your figures.

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2 hours ago, Ephedrin said:

I've tried to find some real CIs but only found pages with completely outdated information

Yeah.

CIs are variable. That's kind of the point of them, despite the common idea that each operator has this set value. Some do, sure, but having a fixed CI is about as effective as saying "we fly at FL320...always."

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1 minute ago, scandinavian13 said:

Yeah.

CIs are variable. That's kind of the point of them, despite the common idea that each operator has this set value. Some do, sure, but having a fixed CI is about as effective as saying "we fly at FL320...always."

fixed (low) fuel prices would be great too...

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1 minute ago, Ephedrin said:

fixed (low) fuel prices would be great too...

Fuel is already exempt of taxes. If there were taxes added then the fuel would be more pricey.

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23 hours ago, scandinavian13 said:

Yeah.

CIs are variable. That's kind of the point of them, despite the common idea that each operator has this set value. Some do, sure, but having a fixed CI is about as effective as saying "we fly at FL320...always."

As my most favourite aircraft is the 747-400F in Atlas Air colours, all said and done amongst others, Kyle, you being in the 'live' game, so to speak, is there a website that one could source for different operators CIs

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2 hours ago, vc10man said:

As my most favourite aircraft is the 747-400F in Atlas Air colours, all said and done amongst others, Kyle, you being in the 'live' game, so to speak, is there a website that one could source for different operators CIs

5Y CI’s vary depending on the flight.  

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4 hours ago, vc10man said:

As my most favourite aircraft is the 747-400F in Atlas Air colours, all said and done amongst others, Kyle, you being in the 'live' game, so to speak, is there a website that one could source for different operators CIs

That's the point I was making: those websites are worthless.

What you're asking for is akin to asking "what flight level does Atlas use?"

The answer, as you know, is "depends on the flight, the time of day, the weather, the wind, the loadout," and so on.

 

CI is an extension of this concept: it is an adjustment based on input variables (the time of day, cost of fuel, need to be there faster rather than slower, etc). So, if you find a website with those values, the data will be good for the one flight that that person saw with that value, at that time, with that weather, for that aircraft type (for that engine type, if applicable), and so on.

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As a rule of thumb, if the flight is on time, I would say 035-075 is typically what is used. If the flight is late and time is critical it’ll usually be planned at 600. But again, those are very general. 

Edited by Jetlinker

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57 minutes ago, scandinavian13 said:

That's the point I was making: those websites are worthless.

What you're asking for is akin to asking "what flight level does Atlas use?"

The answer, as you know, is "depends on the flight, the time of day, the weather, the wind, the loadout," and so on.

 

CI is an extension of this concept: it is an adjustment based on input variables (the time of day, cost of fuel, need to be there faster rather than slower, etc). So, if you find a website with those values, the data will be good for the one flight that that person saw with that value, at that time, with that weather, for that aircraft type (for that engine type, if applicable), and so on.

Thanks, Kyle, fully explained. Now I get it. A parameter that varies dependent on other varying factors.

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3 hours ago, scandinavian13 said:

That's the point I was making: those websites are worthless.

What you're asking for is akin to asking "what flight level does Atlas use?"

The answer, as you know, is "depends on the flight, the time of day, the weather, the wind, the loadout," and so on.

 

CI is an extension of this concept: it is an adjustment based on input variables (the time of day, cost of fuel, need to be there faster rather than slower, etc). So, if you find a website with those values, the data will be good for the one flight that that person saw with that value, at that time, with that weather, for that aircraft type (for that engine type, if applicable), and so on.

Kyle,

Am not arguing with you at all on this point but as a member of BA Virtual the guys that run it are very keen on details and CI of 20 for the A319-320 seems to be the figure to use all/most of the time.

BA Virtual is run to mirror BA ops as close as possible.

Perhaps airlines over here might be a bit different like the fuel topic. Ryanair use a CI of 6. Perhaps a Europe thing?

Edited by Nyxx

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1 minute ago, Nyxx said:

Am not arguing with you at all on this point but as a member of BA Virtual the guys that run it are very keen on details and CI of 20 for the A319-320 seems to be the figure to use all/most of the time.

Perhaps airlines over here might be a bit different like the fuel topic. Ryanair use a CI of 6. Perhaps a Europe thing?

Likely a short segment thing. I'm betting their FLs are pretty routine, too. DC to NY, for example, will be between 17000 and FL210, just based on traffic.

You will always find some variation on a rule, but again: CI is meant to be variable. This idea that "X operator uses Y" misses the mark. Even if they use a set CI in a certain fleet (I'd argue either because they're lazy, or they've run the math and have determined the segments are so short that it really doesn't justify the work), it'll vary by plane.

...and this being the 744 part of the forum, I highly doubt any operators had a hard and fast rule on CIs. The segments are way too long to not take advantage of it.

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Just looked it up Kyle,

Just for info and to add to the chat.

747-400 for BA are 53 and 0 can be used for USA east coast.

With the 319/320/321 yes you also get a FL for a given flight.

FL/CI/Real world flight number times etc. Even a know route on a lot of flights. If you get things wrong your not credited with the flight. It’s all very strict but that what you sign up for. The test exam  to join is not easy in the first place fail and you have to wait a month to try again. 🙂 

Edited by Nyxx

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41 minutes ago, Nyxx said:

FL/CI/Real world flight number times etc. Even a know route on a lot of flights. If you get things wrong your not credited with the flight. It’s all very strict but that what you sign up for. The test exam  to join is not easy in the first place fail and you have to wait a month to try again. 🙂 

...and this is why I'm not a member of a single VA out there. This kind of stuff propagates because of VAs, and their assertions of what is, and isn't true, based on some random dispatch they, or their kid picked up off of a flight, or a friend, or something...or Bob, who used to work at BA, and is remarkably vague about what the position actually was.

This isn't always the case, but I'm curious as to the source...

The comment about the 747-400s, though, supports my point: it's variable, and dependent on the situation.

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