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concordeba

Step Climbs as per FPL

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I wasn't sure if the real thing does step climbs in the flight plan.  So as per this 

 

 

 

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How would you set it up so that at the waypoint you want to step climb, you can place this plus the cruise speed in that waypoint?  It always comes up with Invalid when you try to manually input this. The aircraft step climbs when it thinks it should.  I take it the subtle difference is the real world flight as above would have ACARS data fed weather information and flight data more advanced than what we input into FS. 

 

I normally put that above plan through PFPX and save the flight plan to load as CO route.  

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It's covered in the FCOM but maybe not in a direct answer to your question.  Input, for example, .84/350S to override FMS speeds and step climbs and set speed to 0.84M and step to FL350.  Don't forget the 'S' which overrides step calculations.  Return to ECON speed by entering 'E' instead of a speed.

 

Since oceanic routes and tracks are normally fixed speed I use the 0.84/ entering and E/ leaving the ocean route/track.

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How would you set it up so that at the waypoint you want to step climb, you can place this plus the cruise speed in that waypoint?  It always comes up with Invalid when you try to manually input this. The aircraft step climbs when it thinks it should.  I take it the subtle difference is the real world flight as above would have ACARS data fed weather information and flight data more advanced than what we input into FS. 

 

Dan gave you the generics, but I have to point out that there's a difference between filed and flown.

 

Operators provide flight plans like that to give the flow management and trajectory automation an idea of what they plan on doing. In other words, the flight plan is run through various systems to determine compliance, which parts of the plan go to which facility, and if the flight will conflict with any other flights in theory (this is also how we determine/assign slots during traffic constrained situations). If the operator didn't include the planned steps and speeds, the system would assume that it would be flying at the initial cruise request the entire time and would project the 4D (x, y, altitude, time) flight trajectory incorrectly. With it in there, however, the "system" knows what the flight is most likely going to do. Additionally, the flight planning systems, in order to not make things confusing for the processing/controllers, simply choose the closest waypoint to the planned step climb and list it there.

 

In actuality, however, the flight would climb on the FMC calculated steps. A flight crew need not climb early, or delay a climb simply to pass over a fix for the step climb itself. Being cleared on your route with the step points in it is NOT implicit clearance to begin a climb at that waypoint without requesting the climb from ATC. This is even more of a reason to just climb on the ECON profile (if you have to request it anyway, you might as well request the climb when it's economical to do so). Add the fact that certain fixes are intersections for airways, which means potentially crossing traffic to delay a climb even longer, and you start to see why constraining yourself to climbing at fixes just doesn't make much sense.

 

Unless you set the step size to 0 in the FMC, then it will already be calculating that you're going to step. Manually overriding this by unnecessarily forcing steps at fixes means you're going to just make yourself that much less efficient, and it requires more work to do it.

 

 

 

That being said, like Dan said, the NAT segments are usually single altitude, constant speed segments. This is particularly the case when it's busy. Granted, climbs are occasionally approved, but it's best to plan on their not being approved to ensure you are carrying enough fuel.

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It's covered in the FCOM but maybe not in a direct answer to your question.  Input, for example, .84/350S to override FMS speeds and step climbs and set speed to 0.84M and step to FL350.  Don't forget the 'S' which overrides step calculations.  Return to ECON speed by entering 'E' instead of a speed.

 

Since oceanic routes and tracks are normally fixed speed I use the 0.84/ entering and E/ leaving the ocean route/track.

That works a treat. But I've noted it's quite hard to then set manual altitudes along the STAR or after a STAR. I don't think the system can manage it, either that or I am doing it wrong. It is a shame we cannot link in winds to the FMC and get a more accurate fuel reading for the flight.  I am not really sure how it all works on the flight sim side of things, but I know our operator gets direct wind data through ACARS to the aircraft via satcom.

 

Dan gave you the generics, but I have to point out that there's a difference between filed and flown.

 

Operators provide flight plans like that to give the flow management and trajectory automation an idea of what they plan on doing. In other words, the flight plan is run through various systems to determine compliance, which parts of the plan go to which facility, and if the flight will conflict with any other flights in theory (this is also how we determine/assign slots during traffic constrained situations). If the operator didn't include the planned steps and speeds, the system would assume that it would be flying at the initial cruise request the entire time and would project the 4D (x, y, altitude, time) flight trajectory incorrectly. With it in there, however, the "system" knows what the flight is most likely going to do. Additionally, the flight planning systems, in order to not make things confusing for the processing/controllers, simply choose the closest waypoint to the planned step climb and list it there.

 

In actuality, however, the flight would climb on the FMC calculated steps. A flight crew need not climb early, or delay a climb simply to pass over a fix for the step climb itself. Being cleared on your route with the step points in it is NOT implicit clearance to begin a climb at that waypoint without requesting the climb from ATC. This is even more of a reason to just climb on the ECON profile (if you have to request it anyway, you might as well request the climb when it's economical to do so). Add the fact that certain fixes are intersections for airways, which means potentially crossing traffic to delay a climb even longer, and you start to see why constraining yourself to climbing at fixes just doesn't make much sense.

 

Unless you set the step size to 0 in the FMC, then it will already be calculating that you're going to step. Manually overriding this by unnecessarily forcing steps at fixes means you're going to just make yourself that much less efficient, and it requires more work to do it.

 

 

 

That being said, like Dan said, the NAT segments are usually single altitude, constant speed segments. This is particularly the case when it's busy. Granted, climbs are occasionally approved, but it's best to plan on their not being approved to ensure you are carrying enough fuel.

 

That is correct, however IF the operator has SATCOM link and the flight plan is genuinely linked quite well with what the will do on the flight.  Most carriers that are after optimal fuel savings on landings will try and stick to the flight plan as per filed.  But you are indeed correct when you say that it's not a clearance as such.  In fact most times, the captain will override the flight plan if the forecast has changed and there's a more optimal flight level to be had.

 

Furthermore I guess that a lot of the time ATC can change things based on the 3D picture they have and what and where they need the aircraft.   

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Most carriers that are after optimal fuel savings on landings will try and stick to the flight plan as per filed.  But you are indeed correct when you say that it's not a clearance as such.

 

You contradict yourself here...

 

As you mentioned, most carriers are after fuel savings, but you also say that operators will try to stick to the flight plan as filed. These statements contradict. Next time you plan out a flight, look at where the planner is providing the step climb information. It will always choose a fix. Now, think back to any time you've flown a route without manually entering the step climbs. That is to say, think of any flight that the automation has calculated the ECON path on its own. How many times have those steps been right on top of fixes? Very rarely, and if they did, it was quite the coincidence. On your flight plan, there are four that happen right at fixes.

 

Again, remember that the planner will choose fixes so that it can easily calculate the legs, without adding a ton of pseudo-waypoints that could confuse ATC systems (and the crew). These points are chosen to give ATC an idea of what will happen, and not exactly what will happen (again, remembering that the ECON profile is actually what is being calculated without the manual step points).

 

Now, if you're going on the NATs and expect that to be a constant speed/altitude crossing (when it's busy, you rarely get a chance to climb due to the separation requirements on the NATs), then sure, force the altitudes there, but leave it at ECON elsewhere.

 

 

 


In fact most times, the captain will override the flight plan if the forecast has changed and there's a more optimal flight level to be had.

 

The crew will request an amended clearance to a more optimal flight level. I know that's a bit pedantic, but the whole "captain" misconception drives me nuts. It only contributes to the public freak out session to be had any time the first officer does something. I can't even tell you how many times I've heard "can you believe the First Officer was the one flying the plane?!?!?"

 

 

 


however IF the operator has SATCOM link and the flight plan is genuinely linked quite well with what the will do on the flight.

 

Not sure what SATCOM has to do with anything here. Sure, you can request and amend things a bit more easily using SATCOM (specifically CPDLC), but I don't see what it has to do with your climb question. That's a request/receive function. If you're already requesting an altitude change, why not save time/effort and request the climb on the ECON path instead of doing extra work to burn extra fuel?

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The crew will request an amended clearance to a more optimal flight level. I know that's a bit pedantic, but the whole "captain" misconception drives me nuts. It only contributes to the public freak out session to be had any time the first officer does something. I can't even tell you how many times I've heard "can you believe the First Officer was the one flying the plane?!?!?"

 

Thx for that Kyle :-)

 

Things get worse once you go to Germany/Austria!

 

In Germany/Austria the wordt Pilot means Captain!!

So an aircraft is flown by one pilot (=Captain) and then there is a guy sitting next to him.

 

The General public thinks that after years and years of sitting next to the allmighthy pilot, never touching the controls except during cruise flight when the pilot goes to the loo, at some point the FO will then be able to safely land the aircraft under all conditions, all of a sudden, magically, lol.

 

Very annoying indeed!

 

Anyway, to get to the Flightplan thing....

There are two parts to the flight plan.

The ATC filed flight plan which you guys discussed above, and the OFP.

The Operational Fligh Plan is a couple of A4 pages you work with during flight.

You note ETA and ATA for each waypoint and do your hourly fuel checks on there, etc.

The OFP also holds the EXACT dispatch calculated step climbs.

Not at fixes but inbetween fixes as well sometimes!

The idea is to stick to the OFP as much a practical but this is based on dispatch data ofcourse. So the OFP is a guideline.

Often your take off weight will be one or two tons different from what dispatch assumed......that is the end of your OFP forecast climbs right there.

 

Also if you request new enroute winds (available in real life every 6 hours) and if they are totally different as what Dispatch worked with, then again you would climb according to FMC predictions.

 

But if dispatch data matches real life winds pretty good, then it makes sence to stick to the OFP climbs because the OFP is calculated with far better (read higher resolution) weather data and better performance calculations than what the (primitive) FMC can do.

 

Besides NAT tracks, the other reason to put fixed step climbs into the FMC is when you know there are ATC restrictions ahead.

Afghanistan is a good example. Dispatch files a FL for the Afghanistan overflight, and if you are on schedule you will get exactly that level. Even if the FMC would want to fly higher or lower over there, you should put the filed level and speed in the legs page to get accurate fuel and time estimates for your destination. Because ATC usually will not allow a step climb there.

 

By the way something new is that step climbs are now also possible on NAT tracks.

They are requested by ACARS and often denied but sometimes given(also via ACARS).

 

I actually vary things quite a few times on the legs page during flight.

I will put in the filed FL at waypoints and see what I end up with at destination.

Then I play with my CI a little to see if I can do something there....depending on whether I am ahead of schedule or delayed.

Then I will take it all out again and see what the FMC comes up with.

And so I compare.

During a NAT flight I put the NAT FL and mach number in fixed as Dan described.

Sometimes I then have to change to a step climb of 1000ft rather than RVSM if I want my FMC to predict my next step climb correctly according to the direction of flight.

Or I put in the FL I think I will get once I reach the other side with step zero for example....it all depends on the flight.

And once I get across the Atlantic I might erase all my fixed FL again and see what the FMC comes up with now.....etc etc.....it is a constant fine tuning and playing around.....what else to do on those long flights?!

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