ECON CRZ, page 2/3

[youngie63 4]

Thanks guys, pretty much confirmed what l thought. That said, if a captain decides to stick with the flight planned SC's, shouldn't he be able to manually program the FMC accordingly in the VNAV page E.g. at time 'xxxxz' climb to 'FLzzz' or at 'Wpt' climb to 'FLzzz'. Just curious as the PMDG FMC will allow some changes but not those specified in the examples.

 

[Captain Kevin 586]

6 hours ago, youngie63 said:

Thanks guys, pretty much confirmed what l thought. That said, if a captain decides to stick with the flight planned SC's, shouldn't he be able to manually program the FMC accordingly in the VNAV page E.g. at time 'xxxxz' climb to 'FLzzz' or at 'Wpt' climb to 'FLzzz'. Just curious as the PMDG FMC will allow some changes but not those specified in the examples.

No, because you can't just change altitudes without getting approval from the air traffic controller. Yes, it might be in the flight plan, but what's planned and what actually happens are two completely different things. Once you get the approval to change altitudes, then you can punch in the cruise altitude on the cruise altitude line.

[Budbud 227]

 

8 hours ago, youngie63 said:

That said, if a captain decides to stick with the flight planned SC's, shouldn't he be able to manually program the FMC accordingly in the VNAV page E.g. at time 'xxxxz' climb to 'FLzzz' or at 'Wpt' climb to 'FLzzz'.

Hi,

You can enter manual stepclimb in the leg page by entering the three figures of the flightlevel followed by S (ex: 350S) but you'd better leave the steps calculated by the FMC. The step climbs of the flight plan are based on fuel consumptions and winds predictions. Shoud your fuel consumptions and winds be a bit different in the real flight and your theoretical step climbs from the flight plans won't be optimum while the FMC will update the calculations throughout the flight.

Keep it mind that the step climbs in the flight plan are just "advisory" with regards to the waypoints they are attached to. You don't have to execute them as per the flight plan, except for change of levels required due to changes of airways or airspaces.

Also as said by Kevin, no change of level is allowed without clearance from the ATC no matter what (except of course in case of TCAS alert).

[scandinavian13 5,192]

9 hours ago, youngie63 said:

Thanks guys, pretty much confirmed what l thought. That said, if a captain decides to stick with the flight planned SC's, shouldn't he be able to manually program the FMC accordingly in the VNAV page E.g. at time 'xxxxz' climb to 'FLzzz' or at 'Wpt' climb to 'FLzzz'. Just curious as the PMDG FMC will allow some changes but not those specified in the examples.

Trust the plane over the dispatch paperwork. That paperwork is a plan. It is not actuality. That plan could have been made hours before the flight, with weights that weren't adjusted (note the adjustment lines on all dispatch paperwork). The FMC will have the best performance data, so go with its step function, unless there is a specific reason to do otherwise (fixed cruise segment due to a NAT crossing, for example).

Don't overcomplicate the issue, either. Putting the altitudes in there is only relevant to getting a better idea of performance (specifically fuel burn), and again, only necessary if you know you will be forced into that altitude for some reason or another (NAT crossing, max altitude on an airway, and so on). The function is NOT to be used as a way of getting the plane to automatically climb (that isn't a function of the real jet anyway).

Short version: if you do not have some sort of altitude restriction, set the step size to whatever you need it to be and leave it alone. Don't overcomplicate it, as many simmers are apt to do when handed an FMC.

[icaruss 18]

My experience with dispatch is that they are pretty darn precise.  At least my airline releases are within an hour and the weights are given after pax are loaded and bags are scanned inside the aicraft.  If they are deviations, are usually for winds or reroutes.  There are manual dispatch weight adjustments, but they are given prior to takeoff and updated in the FMS.  Like anything, trust but verify, however dispatch is pretty darn good.

[scandinavian13 5,192]

11 hours ago, icaruss said:

My experience with dispatch is that they are pretty darn precise.  At least my airline releases are within an hour and the weights are given after pax are loaded and bags are scanned inside the aicraft.  If they are deviations, are usually for winds or reroutes.  There are manual dispatch weight adjustments, but they are given prior to takeoff and updated in the FMS.  Like anything, trust but verify, however dispatch is pretty darn good.

Agreed, but that's not the point. Don't force the plane into following the dispatch SCs simply to have it follow the dispatch exactly, unless, of course, there is a specific reason (those I mentioned earlier).

[skelsey 765]

Thoughts from me:

Generally I agree with Kyle. However, I know of at least one airline whose guidance to pilots was/is to stick to the OFP levels as they were planned for the optimum levels based on forecast winds (and, potentially, ATC restrictions etc) and therefore they considered them likely to be more accurate/efficient than the FMC overall. There is also an issue that at one point the CFMU types were getting cheesed off with pilots climbing as high as possible despite being flightplanned at lower levels and thus screwing up their flow management (because if you split a sector vertically based on a certain number of aircraft planned at a lower level and they all climb up in to the higher sector it ends up overloaded). In practice, regardless of the guidance I think most pilots just climb as high as they can as soon as they can (i.e. follow the FMC).

However, with Boeing Winds these days I think the quality of the FMC wind data is much better now and thus I think it provides better results. Thus -- yes, ATC permitting I would go with the FMC.

As mentioned above, what you should do if you know you are not going to be able to climb/will be required to climb at a certain point is enter that in to the FMC as this will improve your time/fuel predictions.

[scandinavian13 5,192]

1 minute ago, skelsey said:

Generally I agree with Kyle. However, I know of at least one airline whose guidance to pilots was/is to stick to the OFP levels as they were planned for the optimum levels based on forecast winds (and, potentially, ATC restrictions etc) and therefore they considered them likely to be more accurate/efficient than the FMC overall. There is also an issue that at one point the CFMU types were getting cheesed off with pilots climbing as high as possible despite being flightplanned at lower levels and thus screwing up their flow management (because if you split a sector vertically based on a certain number of aircraft planned at a lower level and they all climb up in to the higher sector it ends up overloaded). In practice, regardless of the guidance I think most pilots just climb as high as they can as soon as they can (i.e. follow the FMC).

All of these would classify as:

"unless, of course, there is a specific reason (those I mentioned earlier)."

...so, I'm confused as to why we're continuing down this path.

 

 

If there is a reason that you are going to do X. Do X. It is also advisable to let the aircraft know that you are doing X.

If you're looking at a default PFPX plan, though, and it simply shows it expects you'll probably be at X altitude by Y point, and throws in an advisory altitude/speed in the OFP, and you have no idea why it did that - go with the flow, and don't overcomplicate things.

There are people up front because we have yet to substitute computers for brains. Use your brain. "Will this help me, and is this necessary?" Look at some of the odd stuff PFPX will toss into a plan. Some people do 42 backflips, 10 pushups, and finish by bobbing for apples, just to get the FMC to match that plan (that makes little to no sense). There's no need. "Does this make sense? Is it telling me to be at X altitude for a specific reason other than the assumption of the normal FMC step profile? Yes? Okay, mod the data. No? Okay, leave it alone."

It's really, actually, incredibly simple. The problem is that real world dispatch is usually manually setting those params, or they're using more powerful planning tools for optimization. PFPX is limited to the user, and most people don't even know you can set segment restrictions (like across the NATs), but people trust the program as if it were a human doing it. Wrong.

[skelsey 765]

Sure. As I say, I'm not disagreeing with you -- if the wind data is accurate (as it is now IRL, more so than in the past, with AOC Boeing Winds uplinks) then the FMC is an excellent tactical tool. Just throwing in some additional background as to why sometimes it might be appropriate to follow the OFP (or indeed why "XXX pilot says we're supposed to follow the OFP...") or why it might not be, or indeed why it might not be appropriate to follow either if you look at the wind forecast/hear from another aircraft that there's a whacking great headwind or turbulence at FLxxx.

PFPX and Simbrief can (and do) optimise levels based on the wind forecast etc (though the PFPX optimisation in particular I find rather odd).

31 minutes ago, scandinavian13 said:

There are people up front because we have yet to substitute computers for brains. Use your brain.

Absolutely. However, to make the best decisions it's necessary to understand how the system(s) (both on the planning side and the aircraft side) work and how they are arriving at their numbers.

[icaruss 18]

PFPX vs a real world dispatch software operated by a certified dispatch are two completely different scenarios.

Anyways, bottom line is a release gives you a good plan to follow, unless it warrants a deviation by the pilot, due to different conditions from those planned.  Commonsense really by the pilot is the rule of thumb.  

[MattS 45]

On November 27, 2017 at 7:44 AM, scandinavian13 said:

The function is NOT to be used as a way of getting the plane to automatically climb (that isn't a function of the real jet anyway

Kyle,

just curious....striving for realism, which function are you referring to that isn't available in the real aircraft? The ability to enter step climbs into the legs page to predict fuel consumption, or the auto step climb function? I think you're talking about auto step climbs, correct? The legs page function is real, also correct? Thanks

[Budbud 227]

Hi,

Yes on the auto step climb function doesn't exist on the real aircraft. The step climbs both manual entry and automatic calculations are real features of the FMC.

Basically, when you look at the CDU, the menus PMDG setup and FS actions don't exist in the real aircraft, so all the functions you can find here (hence including the auto cruise features).

All the rest that is not in these two menus are real.

[Ephedrin 418]

Take into consideration that simbrief uses real weather from the moment you calculate your flight. If you do this today but do a summer flight using AS historical weather there will be discrepancies between simbrief and FMC. Also simbrief has I think 2 or 3 versions of the 744, PMDG has delivered euhm...7? 8? Versions. There are differences like engines, dry op weight, etc that can be entered into simbrief but... honestly... who is doing it? If it gives us an initial cruise alt of FL330 and our dear FMC would prefer 2000ft higher, hey, lets climb :D that‘s why there are still pilots up there... we are flexible. 

 

Edit: oh... I‘ve completely missed on the mobile phone that there is a second page... so.. actually... a little late answering on simbrief 

Edited November 29, 2017 by Ephedrin
Snoooooze

[MattS 45]

35 minutes ago, Budbud said:

All the rest that is not in these two menus are real.

Wait......so auto time compression isn't real?!?!  lol

Thanks Romain. I was sure that auto step climbs don't exist in the real aircraft, but I wasn't sure if Kyle was talking about the legs page step climb function. It's always good to know what is real and what is fantasy. 

[Budbud 227]

5 minutes ago, MattS said:

Wait......so auto time compression isn't real?!?!  lol

Hehe! Would be useful sometimes irl.