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Gregg_Seipp

Questions on Tutorial 1.5

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I'd planned on doing a flight today I ended up getting caught up trying to figure some things out in tutorial 1.5 and ended up doing a lot of reading instead, in part, to build up knowledge and, also, to fill in gaps of what I wasn't catching on the tutorial.  I'm a little bleary eyed so, if I missed something, I hope you'll be kind. 

  • So, is the Ground Operations page a way to get the fuel loaded in a more realistic way (instead of using the Fuel page which instantaneously loads it?)  I assume GSX has nothing to do with it...I can request fuel through GSX but it's just driving nice looking trucks over and then pulling them away, yes?  Is uplift fuel the difference between trip fuel and what I already have on board?
  • The takeoff selected in the sim was TO-1.  I thought those kinds of derates were not recommended?  I turned them off in TopCat...using assumed temp instead.
  • Where did the 33% CG come from?  I thought it was something like 27% from the Payload page...or did I miss something?

So much to read.

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I'd planned on doing a flight today I ended up getting caught up trying to figure some things out in tutorial 1.5 and ended up doing a lot of reading instead, in part, to build up knowledge and, also, to fill in gaps of what I wasn't catching on the tutorial. I'm a little bleary eyed so, if I missed something, I hope you'll be kind.

  • So, is the Ground Operations page a way to get the fuel loaded in a more realistic way (instead of using the Fuel page which instantaneously loads it?) I assume GSX has nothing to do with it...I can request fuel through GSX but it's just driving nice looking trucks over and then pulling them away, yes? Is uplift fuel the difference between trip fuel and what I already have on board?
  • The takeoff selected in the sim was TO-1. I thought those kinds of derates were not recommended? I turned them off in TopCat...using assumed temp instead.
  • Where did the 33% CG come from? I thought it was something like 27% from the Payload page...or did I miss something?
So much to read.

Not, gsx has nothing to do with pmdg ground ops fueling.

 

Yes, your uplift math is correct.

 

I don't know where you heard that TO-1 and TO-2 derates aren't recommended. Maybe a certain airline has rules against it (Emirates didn't even purchase this option) but they are used every day around the world.

 

Just use the cg from the takeoff page in the FMC. Pmdg had their own calculations going on inside the 777 software.

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  1. So, is the Ground Operations page a way to get the fuel loaded in a more realistic way (instead of using the Fuel page which instantaneously loads it?)  I assume GSX has nothing to do with it...I can request fuel through GSX but it's just driving nice looking trucks over and then pulling them away, yes?  Is uplift fuel the difference between trip fuel and what I already have on board?
  2. The takeoff selected in the sim was TO-1.  I thought those kinds of derates were not recommended?  I turned them off in TopCat...using assumed temp instead.
  3. Where did the 33% CG come from?  I thought it was something like 27% from the Payload page...or did I miss something?

 

  1. Correct. This loads fuel over time. GSX has nothing to do with this, and is only visual. Uplift, as would be indicated by the name, is the amount of fuel coming up out of the truck/pump and into your aircraft. If you follow the instructions, then simply enter the numbers that are used in the tutorial.
  2. Why would they be an option if they weren't recommended? Many airlines have their own takes on things, will purchase different options, and have different SOPs based on how they think the world should run. Either way, you did not need to run the numbers in TOPCAT on your own as the tutorial included the runway data for you.
  3. Instead of a direct answer, I'll ask a question: Why did you accomplish the step at the bottom of page 31? (Hint: See the first sentence of the last bullet point on the page. How might this affect CG?)

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Why would they be an option if they weren't recommended? Many airlines have their own takes on things, will purchase different options, and have different SOPs based on how they think the world should run. Either way, you did not need to run the numbers in TOPCAT on your own as the tutorial included the runway data for you.

 

Hmmm...okay, I was reading a thread here on the forums about 2 weeks ago and there was some discussion.  Something about wear and tear on the engine.  Anyway, if it's used it's used and I'll turn the option back on  In terms of TOPCAT...I figured there was a reason it was showing me TOPCAT and, since I have it, thought it would be good to follow along.  I haven't used it much...pretty cryptic, but I better get used to it or get another way of getting the numbers.  Seems silly not to use it if I have it.

 

 

 


Instead of a direct answer, I'll ask a question: Why did you accomplish the step at the bottom of page 31? (Hint: See the first sentence of the last bullet point on the page. How might this affect CG?)

 

Heck, honestly, I was guessing that it was a way to fake the FMS into using a fuel figure that was going to be true in the future.  When I was clicking REQUEST, I thought, "Request what?  From whom?"  That's when I got the Intro out and started reading.  Um...so, are you saying that the CG was shown and automatically calculated by the FMS and I should just, more or less, ignore it? 

 

I'm going to break out the FCTM some this weekend and do some studying.

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Gregg in the FCTM sec. 3.15 there is info on reduced thrust and derates.

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Hmmm...okay, I was reading a thread here on the forums about 2 weeks ago and there was some discussion.  Something about wear and tear on the engine.  Anyway, if it's used it's used and I'll turn the option back on  In terms of TOPCAT...I figured there was a reason it was showing me TOPCAT and, since I have it, thought it would be good to follow along.  I haven't used it much...pretty cryptic, but I better get used to it or get another way of getting the numbers.  Seems silly not to use it if I have it.

 

Derates and assumed temps will increase the life of the engine because they're not being run up to max thrust each takeoff. They're just different methods. The difference - and where the safety issue creeps in - is that one of them does not allow you to force max thrust with a second click of the TOGA button.

 

In this case, the flight was fully dispatched. All of the numbers work the way they do because of how the whole thing was put together. It would make sense to use TOPCAT on any other flight, but not really for this one. You may want to try it out in parallel to see how it all works, but it's best to default to the numbers and values that have been included to ensure everything goes to plan. A good example of why is that a difference in how you set up TOPCAT would have gotten you different values.

 

 

 


Heck, honestly, I was guessing that it was a way to fake the FMS into using a fuel figure that was going to be true in the future.  When I was clicking REQUEST, I thought, "Request what?  From whom?"  That's when I got the Intro out and started reading.  Um...so, are you saying that the CG was shown and automatically calculated by the FMS and I should just, more or less, ignore it? 

 

The procedure at the bottom of page 31 is to get the FMC to understand what the actual fuel will be when fueling is complete. If you had left that spot alone, then you'd get warning messages about the fuel until pretty late in the fueling process, which would be distracting and annoying. Instead of having it run the numbers with the fuel in the tanks currently, why not simply tell it how much fuel it will have for the flight? It's not tricking it into anything. It's telling it what is to come. It's no more of a trick than putting the route in the RTE page: this is what the flight will look like when we are ready to fly it.

 

Pressing <REQUEST theoretically requests the performance data from dispatch, but in this simulation there is no dispatch center, so it pulls the data from the aircraft itself along with a few calculations.

 

The CG on the PAYLOAD page was correct for when we set the payload. At the time, it was 27ish for that combination of people and fuel. As fuel is added, this will move (that's why the page refers to it as the TOCG and not simply CG). Since we are adding fuel, this value is changing. This is further confirmed when the tutorial prompts you to enter the CG value:

 

"Do not use the CG double click shortcut while the plane is being fueled. The CG will shift as fuel is added, which will throw off the TRIM value."

 

So we aren't ignoring the 27% value as much as noting that the value will change as fuel is been added. In reality the CG value will come from an EFB or from dispatch using actual cargo and passenger counts for that day's flight. In our case here, we're adding 33% because that's the value we've been given by dispatch/EFB (neither of which is present in the sim, so that function is provided by the tutorial's writing). If you'd like to test it out, skip using the GROUND OPS function, enter the fuel directly on the FUEL page and use the double click trick (or go back to the PAYLOAD page). You should find that the value comes out to be pretty close to 33%.

 

In different terms, we aren't ignoring that 27% any more than we would ignore the amount of fuel onboard prior to fueling. It's not that we're ignoring it; it's that we know it will be different when the fueling is done.

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Derates and assumed temps will increase the life of the engine because they're not being run up to max thrust each takeoff. They're just different methods. The difference - and where the safety issue creeps in - is that one of them does not allow you to force max thrust with a second click of the TOGA button.

 

I'm not going to quote your entire post but I get it.  I went back and found the post and read the details to get more clarity on the subject.  Interesting about the TOGA thing you mention. 

 

Okay, so the request goes to 'dispatch'...explains the wait and then Reject/Accept thing. 

 

Also okay that we *could* have gotten the same 33% if we'd have directly loaded the fuel and it would also come from dispatch.  Since there is no EFB/dispatch, if we're using Ground Services, to wait until the fuel load is complete to get the CG value? 

 

Like I mentioned, I'm going to go through the docs for a while and see if I can get it all cleared up in my head.


 

 


Gregg in the FCTM sec. 3.15 there is info on reduced thrust and derates.

 

Okay.  I'll scroll down and read through it. 

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Since there is no EFB/dispatch, if we're using Ground Services, to wait until the fuel load is complete to get the CG value? 

 

If you're using the double click shortcut, yes. As far as I'm aware, though, there's no external tool currently out there that will give you an accurate CG value for the 777, so that's just about the only option. There's no real need to run the takeoff perf data through that early, though. I was just trying to quick turn the aircraft to show ground ops without making you sit there forever waiting for the departure time.

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If you're using the double click shortcut, yes. As far as I'm aware, though, there's no external tool currently out there that will give you an accurate CG value for the 777, so that's just about the only option. There's no real need to run the takeoff perf data through that early, though. I was just trying to quick turn the aircraft to show ground ops without making you sit there forever waiting for the departure time.

 

Ok.  Now I know what to do.  Thanks for the help.  Back to reading.

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