MattS

777 Step Climbs

Recommended Posts

Let me start off by saying that I know this is not the QOTSII, or any other Boeing aircraft. Also, I have searched the FCOM and other options for the answer to my question, but have been unsuccessful. Also, please note that I have hundreds of hours in the NGX and QOTSII, so suggestions of "fly the tutorial" are not much help. Unfortunately, you often have to preface questions in these forums because.....well, most of you know.......

In the QOTSII, the initial altitude could be entered into the FMC (say 320), and then step climbs could be entered later in the legs page (say 340 then 360). I found that the 747 would then climb no higher than my final step climb entry of 36000. No problem.

But in the 777 (which I am new to), I find that the same procedure results in a similar outcome....except IF the FMC calculates that a higher climb is recommended after 360, the FMC assigns (lets say 380) further along into the flight plan. The aircraft will then climb to 3800 since I have auto step climb feature turned on. I cannot seem to enter 360 into those waypoints later on in the flight plan after my commanded step climb to 360. The only way I have figured out to bypass this is to set the step size to 0, enter the step climbs I desire, and then revert back to 2000 or RSVM.

My questions are: Does the 777 have a different procedure than the 747 for entering step climbs and cruise altitudes? Could it be that the 747 doesn't calculate a further step climb because it is unable to reach a higher altitude? Is what I am seeing completely normal for the 777 and other Boeings?

Thanks in advance for your input.

  • Upvote 1

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

1 hour ago, MattS said:

Also, please note that I have hundreds of hours in the NGX and QOTSII, so suggestions of "fly the tutorial" are not much help.

Every plane is different. To ignore a tutorial because you have hundreds of hours in something is to assert that your experience in one plane gives you the knowledge necessary to do so. This is clearly not the case, however.

I have hundreds of hours in lots of things. That doesn't mean I'm going to try and ride those hours as some badge of merit to sidestep the efforts of learning new things. Of course it's help. The basics may be the same, and the flows may be similar, but the planes are different. Take the time to sit down and put the effort in.

  • Upvote 1

Share this post


Link to post
Share on other sites

Hi,

I'm not sure I understand the purpose of what you want to do. Why do you want to limit your flight level to FL360 if the aircraft can fly higher? 

  • Upvote 1

Share this post


Link to post
Share on other sites
10 minutes ago, scandinavian13 said:

Take the time to sit down and put the effort in.

Kyle, thank you for taking the time to respond. I should have mentioned that I have taken the time to fly the tutorial, as I have with all of your aircraft, but I saw nothing in there to explain this. Please know that I am in no way saying this is a bug or a fault. I am just trying to understand the systems as much as I can.

6 minutes ago, Budbud said:

Why do you want to limit your flight level to FL360 if the aircraft can fly higher? 

I am trying to follow my PFPX flight plan, but what about airways that have a FL restriction for instance? How about a NAT with an assigned FL? I am just throwing them out as an example. I know we can hold altitudes through FLC while on the NAT, but I am trying to figure out why the FMC will climb the A/C above the selected step climb when returned to VNAV (an FMC calculated more efficient cruise altitude). I am sure there are lots of instances where an aircraft flies a lower FL than the FMC says it is most efficient at. Like I said, I just want to know the systems as much as possible.

  • Upvote 1

Share this post


Link to post
Share on other sites

Your issue lies in the fact that you use auto step climb which is a feature that doesn't exist in the real aircraft. The real aircraft is obviously not designed for such thing. 

The step climb calculated by the FMC are advisory and in no case the aircraft would climb without a pilot intervention. So in the real life the pilots just control the climb to the desired altitude and are not confronted to a feature that infringe the flight plan/airspaces rules.

So basically, either you fly without auto step climb or you enter manual step climbs to the desired altitude but there is no way to tell the aircraft not to exceed a certain altitude with the auto climb system on.

Share this post


Link to post
Share on other sites

Ok, I totally understand what you are saying. I did turn off auto step climbs and the FMC is still calculating higher climbs than my manually entered steps in the FMC LEGS page. this is normal, correct? Like I said, I never saw this in the 744 (which is a totally different a/c I know). 

So basically you are saying to use auto steps and let it climb as high as it wants, or turn it off and step at the PIC discretion/ATC instruction, ignoring the FMC recommended altitudes. 

Thanks!

22 minutes ago, Budbud said:

but there is no way to tell the aircraft not to exceed a certain altitude with the auto climb system on.

This answers my basic question. I guess my other question is: is this the same as the 744?. It always seems to not climb higher that I tell it to.

Share this post


Link to post
Share on other sites

The FMC will always calculate the step climbs based on the step size and the aircraft weight up to the highest level possible for the duration of the flight no matter what manual step you enter in that's correct. And this is true for both the T7 and the 744. However, enter a manual step climbs in some case may prevent further climbs if this step climb is delayed compared to the FMC prediction.

I did a flight a flight EHAM-HKJK yesterday with the 744 in P3D v4 and ended up at FL410 before the TOD.

 

Share this post


Link to post
Share on other sites

The FMC will always calculate the step climbs based on the step size and the aircraft weight up to the highest level possible for the duration of the flight no matter what manual step you enter in that's correct. And this is true for both the T7 and the 744. However, enter a manual step climbs in some case may prevent further climbs if this step climb is delayed compared to the FMC prediction.

I did a flight a flight EHAM-HKJK yesterday with the 744 in P3D v4 and ended up at FL410 before the TOD.

59 minutes ago, MattS said:

So basically you are saying to use auto steps and let it climb as high as it wants, or turn it off and step at the PIC discretion/ATC instruction, ignoring the FMC recommended altitudes.

If you have time, I would rather suggest flying without the auto step climb and manage the climb yourself as it is more realistic. However that supposes you can stay around you PC for the whole duration of the flight...

It depends also whether you fly online. I exclusively fly on IVAO. So if I set the auto step climb to on, I would have a couple of ATCs unhappy seing an aircraft suddenly changing level without reporting to anyone!

 

Share this post


Link to post
Share on other sites
8 hours ago, MattS said:

Let me start off by saying that I know this is not the QOTSII, or any other Boeing aircraft. Also, I have searched the FCOM and other options for the answer to my question, but have been unsuccessful. Also, please note that I have hundreds of hours in the NGX and QOTSII, so suggestions of "fly the tutorial" are not much help. Unfortunately, you often have to preface questions in these forums because.....well, most of you know.......

In the QOTSII, the initial altitude could be entered into the FMC (say 320), and then step climbs could be entered later in the legs page (say 340 then 360). I found that the 747 would then climb no higher than my final step climb entry of 36000. No problem.

But in the 777 (which I am new to), I find that the same procedure results in a similar outcome....except IF the FMC calculates that a higher climb is recommended after 360, the FMC assigns (lets say 380) further along into the flight plan. The aircraft will then climb to 3800 since I have auto step climb feature turned on. I cannot seem to enter 360 into those waypoints later on in the flight plan after my commanded step climb to 360. The only way I have figured out to bypass this is to set the step size to 0, enter the step climbs I desire, and then revert back to 2000 or RSVM.

My questions are: Does the 777 have a different procedure than the 747 for entering step climbs and cruise altitudes? Could it be that the 747 doesn't calculate a further step climb because it is unable to reach a higher altitude? Is what I am seeing completely normal for the 777 and other Boeings?

Thanks in advance for your input.

Not sure if this is what you are trying to ask, however based on my understanding to your question this is what I come up with:

 

The normal procedure on the 777 is that we don't put any step climb in the LEGS page. Basically pilots will try to follow the FMC RCMD flight level with the standard step size of RVSM or 1000ft ( for oceanic routes crossing the Pacific Ocean only, as I never need to fly across the Atlantic therefore I totally unfamiliar with NATS procedures ). 

 

Or if atc restricts you crusing level to the one below the VNAV cruise page RCMD level, just put zero into the step size so that your FMC fuel prediction at destination will be correct. 

 

Normally if you put a step size into the LEGS page let's say 340S, if you are crusing below 340, the VNAV cruise page will only show information about your 340 step.

However once you have done a climb to your 340 step before or at that waypoint ideally, and once the airplane has flown passed that waypoint with the step flight level previously put in, the FMC will show the next available step climb level based on the step size in the VNAV cruise page (i.e RVSM etc) if available and the RCMD flight level is calculated based on actual and forecast wind and temperature, weight, cost index, step size.

For instances, if you entered 340S, once you are cruising at 340 and passed that waypoint with the 340S altitude constraint, the VNAV cruise page should give you the next step climb of 360 if available provided the step size is either 2000 / RVSM. 

 

If you prefer to set 340 to be you final level, like what you had mentioned before, simply put a step size of zero in VNAV cruise page and put all your step climb in to the legs page.

 

That way you will be sure that VNAV will not calculate a step climb above your final manually input step climb level. And the fuel prediction will be more or less correct if this is what you plan to fly the airplane. 

 

I will have a look into it when I go flying over the coming weekend about this, because normally before we cross that waypoint, either we had already climbed or we are told by ATC we will be stuck at a lower level for a considerably longer period of time, therefore we would delete the step level previously put into the legs page and instead put zero into the STEP SIZE on the VNAV cruise page. 

 

 

Share this post


Link to post
Share on other sites

I primarely use the manual step climb entry for the NATS where the change of flight levels are not often granted on the tracks. So once reached the definitive altitude for the whole track, I usually keep the step size to RVSM and if the FMC calculates a step climb along the track, I "delay" it to the last waypoint of the track with a manual entry.

If I recall well, the subsequent step climbs where displayed on the leg page in the sim even with a manual step climbs entry in the way but I will double-check on my next flight with the T7, and I just checked that it is the case with the 744.

Share this post


Link to post
Share on other sites

Thanks guys! That's all really good information. There are many similarities between the Boeings, but each one is certainly different in their own way. No wonder why a pilot can only hold one type rating at a time. I think I'll switch to manual step climbs....I like the realism idea.

Share this post


Link to post
Share on other sites
4 minutes ago, MattS said:

No wonder why a pilot can only hold one type rating at a time.

Not correct.

In practice a pilot will stick to one aircraft (or perhaps a couple, if they hold a common type cert) in normal airline ops. This is not a regulatory requirement. Rather, it's one of safety and familiarity.

I've been driving a rental car all week. It's automatic. My personal car is manual. I can tell you that I have, on a number of occasions, stomped down with my left foot out of habit when going to start the rental. This is why they keep you to one. That level of habit and familiarity adds some safety to the whole operation.

UAL just dropped the 744. If their 744 drivers are all flying other planes and they suddenly need a 744 driver for some reason, it's not like they're going to have to get someone to swap out their type ratings. They might throw the person in a sim session if it's been a while, but they'll just pull someone off the other line and put them on that plane for the need.

Share this post


Link to post
Share on other sites
11 minutes ago, MattS said:

I think I'll switch to manual step climbs....I like the realism idea.

Also, for what it's worth, I think you're confusing things a bit, though I only really skimmed the posts here.

You mention manually entered steps a couple times. If you're doing that because you see that in your PFPX (or other planner) flight plan, it's because the planner is letting you know that it used that altitude for the prediction. It isn't necessarily telling you that you should use that. In some cases, yes, you will, absolutely (if you cross the NAT during peak times, you're usually stuck at the altitude that you file/request, so it's wise to plan to keep that altitude the whole time), but in many cases, it's just there as an advisory that the planner assumed that you'll climb somewhere around there. As someone else mentioned here, you simply stick to the FMC profile, unless you're told otherwise. No need to manually force the altitudes in there.

Additionally, keep in mind that the 744 was built before RVSM was a thing, and I'm not sure if there were any FMC software updates that added this in, so the default is ICAO (basically, pre-RVSM 2000 increments until FL290, where it then becomes 4000). The 777 uses RVSM, so its step sizes are on a different schedule (2000 until FL410, where it becomes 4000 increments). In the 744 the best way to approximate this is to override ICAO with 2000, since you'll never really get up to 410 in normal ops anyway.

I'm guessing the aircraft have - in certain circumstances - been calculating different OPT altitude profiles than your planner, but you've been forcing it to follow the planner by stuffing altitudes onto the legs page. All the while, you've simply been flying off profile by assuming that the planner knows better than the aircraft.

Share this post


Link to post
Share on other sites
2 minutes ago, scandinavian13 said:

You mention manually entered steps a couple times. If you're doing that because you see that in your PFPX (or other planner) flight plan, it's because the planner is letting you know that it used that altitude for the prediction. It isn't necessarily telling you that you should use that.

I'm guessing the aircraft have - in certain circumstances - been calculating different OPT altitude profiles than your planner, but you've been forcing it to follow the planner by stuffing altitudes onto the legs page. All the while, you've simply been flying off profile by assuming that the planner knows better than the aircraft.

I think you nailed it Kyle. Definitely where I am going wrong. And also the part about the ICAO and RSVM differences between the 744 and 77W.

Always a great help and your input is truly valued. Thank you!

Share this post


Link to post
Share on other sites
4 minutes ago, MattS said:

I think you nailed it Kyle. Definitely where I am going wrong. And also the part about the ICAO and RSVM differences between the 744 and 77W.

Always a great help and your input is truly valued. Thank you!

Welcome!

Share this post


Link to post
Share on other sites

People need to understand that Flight plan tools like PFPX and SimBrief do calculations based on a static wind/weather data and payload estimates. It's the reason pilots go over weight and balance and enter/downlink whatever you wanna call it "final numbers" into their FMC... There are a number of other things that occur in real world between the time a flight plan is accepted and actual takeoff but

The flightplan is your base, the "best case" scenario, wind and weather is ever changing and this makes the flightplan become a reference tool. Your aircraft will use different fuel with these changes, thus changing your weight, giving you different climb and cruise profiles. Even before takeoff, if temperature goes from 28C to 31C, past o below estimations done in the FP, your performance changes drastically...Step climbs are important because they can change so many variables of the flight...and again, its up to the PIC to decide whats best, performance, comfort and safety wise based off of the dynamic conditions and airspace restrictions.

Oh and 777 and 747 have very different systems on board, don't use data from the 777 for the 747 and vice-versa.

  • Upvote 1

Share this post


Link to post
Share on other sites
4 minutes ago, CaptainGabe said:

People need to understand that Flight plan tools like PFPX and SimBrief do calculations based on a static wind/weather data and payload estimates. It's the reason pilots go over weight and balance and enter/downlink whatever you wanna call it "final numbers" into their FMC... There are a number of other things that occur in real world between the time a flight plan is accepted and actual takeoff but

The flightplan is your base, the "best case" scenario, wind and weather is ever changing and this makes the flightplan become a reference tool. Your aircraft will use different fuel with these changes, thus changing your weight, giving you different climb and cruise profiles. Even before takeoff, if temperature goes from 28C to 31C, past o below estimations done in the FP, your performance changes drastically...Step climbs are important because they can change so many variables of the flight...and again, its up to the PIC to decide whats best, performance, comfort and safety wise based off of the dynamic conditions and airspace restrictions.

Oh and 777 and 747 have very different systems on board, don't use data from the 777 for the 747 and vice-versa.

Well stated.

Definitely a reminder that flying isn't about just passively entering data in and going along for the ride. The dispatch is a framework, but the flight itself is down to you.

Share this post


Link to post
Share on other sites

Thanks for the advice Gabe. It's always good to hear from people with real world experience, and since the topic is mostly about flight planning your input is valued. My expertise lies in another aspect of aviation, outside of the cockpit, so I welcome any help that will make me a better sim pilot.

  • Upvote 1

Share this post


Link to post
Share on other sites
9 hours ago, scandinavian13 said:

Not correct.

In practice a pilot will stick to one aircraft (or perhaps a couple, if they hold a common type cert) in normal airline ops. This is not a regulatory requirement. Rather, it's one of safety and familiarity.

I've been driving a rental car all week. It's automatic. My personal car is manual. I can tell you that I have, on a number of occasions, stomped down with my left foot out of habit when going to start the rental. This is why they keep you to one. That level of habit and familiarity adds some safety to the whole operation.

UAL just dropped the 744. If their 744 drivers are all flying other planes and they suddenly need a 744 driver for some reason, it's not like they're going to have to get someone to swap out their type ratings. They might throw the person in a sim session if it's been a while, but they'll just pull someone off the other line and put them on that plane for the need.

Wow don't I feel dumb. Here I was all this time thinking you could only hold one type rating, based on some little nugget I read on the internet (maybe even AVSIM forums) at some point in time. I always thought that if it's on the internet then it must be true. I guess I'm wrong about that too....lol.

That's why I like coming to this forum. Aside from the bull word not allowed that flies around here from time to time, the PMDG forums really are a good place to find accurate information. You just have to listen to the right people.

Share this post


Link to post
Share on other sites
On 9/27/2017 at 11:42 AM, CaptainGabe said:

People need to understand that Flight plan tools like PFPX and SimBrief do calculations based on a static wind/weather data and payload estimates. It's the reason pilots go over weight and balance and enter/downlink whatever you wanna call it "final numbers" into their FMC... There are a number of other things that occur in real world between the time a flight plan is accepted and actual takeoff but

The flightplan is your base, the "best case" scenario, wind and weather is ever changing and this makes the flightplan become a reference tool. Your aircraft will use different fuel with these changes, thus changing your weight, giving you different climb and cruise profiles. Even before takeoff, if temperature goes from 28C to 31C, past o below estimations done in the FP, your performance changes drastically...Step climbs are important because they can change so many variables of the flight...and again, its up to the PIC to decide whats best, performance, comfort and safety wise based off of the dynamic conditions and airspace restrictions.

Oh and 777 and 747 have very different systems on board, don't use data from the 777 for the 747 and vice-versa.

Gabe, while I have your attention may I ask a question?  In my search for realism, I often struggle with what a typical loadout would be in the 77W. From your real world experience, what do you often see in regards to cargo load, passengers, and baggage? Do airlines often or routinely max out the aircraft?  I would also like to hear the different variables that are involved. Thanks in advance. 

Share this post


Link to post
Share on other sites

You can get a good idea of how heavy they are by looking at their initial cruise altitudes.  Right now CX885 B77W KLAX-VHHH has just reached FL300 according to FlightAware.  Given that it is a 11 hr trip you can play with PFPX and see what kind of ZFW limit initial altitudes to FL300.

Share this post


Link to post
Share on other sites
29 minutes ago, MattS said:

Gabe, while I have your attention may I ask a question?  In my search for realism, I often struggle with what a typical loadout would be in the 77W. From your real world experience, what do you often see in regards to cargo load, passengers, and baggage? Do airlines often or routinely max out the aircraft?  I would also like to hear the different variables that are involved. Thanks in advance. 

Ultimately, it all comes down to the different airlines, seating configurations, and routes they fly. As you can imagine, each airline has their own seating configurations, and some airlines have multiple seating configurations even for one type. Then you have the routes they fly, which can dictate how much cargo goes out depending on what cargo is out there. So that being the case, it might not necessarily be easy to get a concrete answer to that question.

Share this post


Link to post
Share on other sites
1 hour ago, downscc said:

You can get a good idea of how heavy they are by looking at their initial cruise altitudes.  Right now CX885 B77W KLAX-VHHH has just reached FL300 according to FlightAware.  Given that it is a 11 hr trip you can play with PFPX and see what kind of ZFW limit initial altitudes to FL300.

For me, the lightest I could get the aircraft was a ZFW around 478,400 to get an initial FL of 300. Max ZFW for the flight is 492,427. 

I used current weather, CI85, PFPX generated flight plan, 15 min hold time, and auto-redispatch. 

Any changes or setting you would suggest? 

Great idea Dan. 

Share this post


Link to post
Share on other sites

LAX-HKG has never been an 11hour flight, this is more like LAX-Tokyo flying time. 

The quickest I have ever seen was at the late 13hours somewhere like 13:40. In the middle of winter the record so far is 15:45-16:00.

And yes, quite often the flight is longer than a typical JFK - HKG flight which goes over the pole 90% of the time. 

CX885 departed recently had a flying time of 14:04, ZFW of around ~207tons and fuel load of ~122tons. Which is considered to be quite "light" for this trip. And they could have used 24L for take off to reduce taxi time. 

it is quite common for any of the HKG bound flight out of LA to take off with 340-350 tons.  

 

In addition, the initial cruise altitude out of LAX to HKG should not be regarded as solely dependent on weight, because the flight planning software will deliberately choose a lower crusing level to avoid the strongest part of the headwind in a jet stream. Therefore quite often they stay low until the last 3-4 hours of the flight then zoom back up to FL360 / FL380 as final level. 

 

 

  • Upvote 1

Share this post


Link to post
Share on other sites
On 9/29/2017 at 3:27 PM, MattS said:

From your real world experience, what do you often see in regards to cargo load, passengers, and baggage?

I'll use the flight I work as an example NRT-IAH 77W

As the Dispatcher, I receive the estimate payload for the flight from the load controller.
Remember, payload is the weight that is added to the OEW, the basic weight of the aircraft with the required fluids, and materials for the flight but MINUS the fuel for the trip. Priority of the Payload in order left to right: Fuel + Passenger/Pax bags + cargo.= Estimate payload. It changes and varies daily based on season and how well the airlines handle business. 
Use this for calculations [Pax + Bags (PAX x 1.5) + cargo = Payload]
Remember! Fuel is more important than cargo!

On 9/29/2017 at 3:27 PM, MattS said:

Do airlines often or routinely max out the aircraft? 

Some airlines fly certain routes with many passengers AND payload or, much cargo and less pax, or a balance of both. I can tell you that our 77W estimates takes 20 tons and up of cargo in addition to 200-260 PAX, limited by config daily. So for us, we TRY and utilize our 77W as much as we can. But as stated in the beginning, cargo is least priority, so, in the next question, I'll answer what I do with these estimates.

However, there is another airline that operates the same aircraft, has 300 PAX yet takes sometimes no more than 10 tons of cargo. So, on the sim, change it up sometimes ;)

If you ever wondered why airlines have so many seating configurations, there is your answer...what is in demand for them.
 

On 9/29/2017 at 3:27 PM, MattS said:

 I would like to hear the different variables that are involved. 

Once the dispatcher has the estimate payload, he does his magic and calculates the best route...BUT this is where the important part comes in. Takeoff and landing performance calculations are made before hand to make sure that the estimate payload does not exceed flight parameters.

Many times, Takeoff performance is what restricts payload…and it does vary from station to station and airline to airline. All of this is calculated just with weather! The next problem is airfield limitations. IAH has 12,000ft runway…great right?! Wrong! We get pretty warm here, summer-35-37C…this heat makes performance suffer and even though, on a cool day we could depart at MTOW 760,000 lbs, with a 12,000ft runway, we are sometimes restricted down to 744.8 etc. In comparison to NRT which as a 14,000ft in cooler climate, they can almost always depart at MTOW. (Kind of wish we had a longer runway for our warm runway to compensate for the heat) 
Size matters!


Excellent questions, this is something Dispatchers don't really talk about and the explanations can be much more detailed.

Please excuse any typos...did this in a rush.
#MakePACOTSgreatagain

  • Upvote 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now