747 V3 Fuel consumption problem

[Cory Collier 2]

Just now, scandinavian13 said:

Sounds like a planning/understanding issue.

1. Nobody cruises at FL345 - ever.
2. Decreasing VS is normal for a heavy load.
3. 24% according to what? FSX or something else?

Tell that to the FMC lol it said max alt was 345., 24% according to FSX. even the FMC at that point was saying I had insufficient fuel.

I always fly with Coords, frame rate, etc showin'

[scandinavian13 5,192]

2 minutes ago, Cory Collier said:

Tell that to the FMC lol it said max alt was 345

The plane also tells you a number of other things that are max. That doesn't mean you need to be doing them.

MAX ALT is exactly that. The max you are able to fly. You should be down at OPT, ideally, and fly the altitude profile (2000' increments, essentially).

3 minutes ago, Cory Collier said:

24% according to FSX

We custom code our fuel. Ignore FSX's fuel interface entirely. This is explained in the Intro Manual, which you should read...along with the tutorial, honestly.

4 minutes ago, Cory Collier said:

even the FMC at that point was saying I had insufficient fuel

What were your fuel numbers?

[Cory Collier 2]

I don't remember, honestly what My numbers were lol I took off with full tanks.

As for the manual...I had it...but um...the dog kinda ate it? (kidding. I'll read it at some point today).

I gotta admit, y'all did a b**chin' job on The Queen. To say y'all did her justice, is an understatement :)

 

I should also confess...been trying to get the folks over at Groom Lake Simulations to do some repaints (free) for The Queen. They MOSTLY do military repaints but hey, I'm trying lol :) If you care to give Me ammo, It'd be much appreciated lol

[scandinavian13 5,192]

2 minutes ago, Cory Collier said:

I don't remember, honestly what My numbers were lol I took off with full tanks.

Flying MAX ALT with full tanks isn't going to get you great range. If you weren't trading payload for fuel, then you were likely way too heavy on DEP and at cruise. That long of a flight isn't just "100% fuel and go." There's more work to it than that.

6 minutes ago, Cory Collier said:

As for the manual...I had it...but um...the dog kinda ate it? (kidding. I'll read it at some point today).

Don't need to read all of the original Boeing stuff - just the Intro. Tutorial would definitely help, along with learning how to use a program like PFPX (or SimBrief, which is fully online and free).

7 minutes ago, Cory Collier said:

To say y'all did her justice, is an understatement :)

Glad to hear it.

[Samany69 41]

I just can't agree more with kyle . He is right . I use ASP4 as weather engine . and I have gathered data from my own flights, writing down the info's and after 20-30 long hauls now i calculate my own fuel considering that i don't get the route from any website but i use Original Jeppesen paper charts to write a proper route meanwhile using real data and also the data provided on TAF and Sigmet and WAFS charts to prefer the best possible route.  On a normal 6-7 hours of flight or even a 16-17 hours of flight , my calculations normally won't go more than 5% off the amount that FMC calculates and also 90-95% as close as the amount the plane actually used and has it remained when i arrive. So i think it might be some sort of sim related bug. My uncle is rated at 74 and he flies it now , even he did confirm that the PMDG 747 can't be more realistic regarding this matter since it was superb and like the real plane. so PMDG is fine at my point of view.

Sorry for bad English.

Regards.

[Cory Collier 2]

On 3/6/2018 at 11:02 AM, scandinavian13 said:

We custom code our fuel. Ignore FSX's fuel interface entirely. This is explained in the Intro Manual, which you should read...along with the tutorial, honestly.

IF this is the case then why is it that FSX and the FMC are in 99.99% agreement, 100% of the time? (FSX rounds up)..... I'm confused.

Doesn't mater if it's My 747, a friend's, or someone else's 747, 737 , or even 777. They're always 99.99% in agreement...which common since tells Me they should be.

Even when I setup fuel levels via the FMC (which is how I normally do it)....they're still in agreement....

https://prnt.sc/iw4p5w

[scandinavian13 5,192]

2 hours ago, Cory Collier said:

F this is the case then why is it that FSX and the FMC are in 99.99% agreement, 100% of the time? (FSX rounds up)..... I'm confused.

Don't know. Honestly don't care. FSX's fuel interface and reported values are entirely irrelevant - values or otherwise. Go with what the FMC reports. Any other value really doesn't matter. If it matches, then great. If not, ignore it.

I'm not sure why this was brought up. Are you attempting to prove me wrong just to draw my points into question, or is there some deeper issue that you're trying to get at? 

[Cory Collier 2]

What I'm saying is FMC and FSX are always in agreement on the amount of fuel left, so your statement is invalid. 

Feel free to have a go at it yourself :) fire up 747 and set the tanks to 25% in FMC....you'll see that FSX says you got 25%.

http://prntscr.com/iw7x3f

http://prntscr.com/iw7xhl

This STILL doesn't explain the random high fuel consumption issue.

As we speak, I'm doing KDFW - YSSY, got about 2720nm left to go and as you can see have 35% fuel left (which is enough). From take-off to FL3000 I climbed at 1500fpm, and from there dropped it to 500 then 400 then eventually to 300 (it was either that or stall out).

KDFW - YSSY and back is My usual route for this bird, and i've done it several times prior to that issue happening....

[scandinavian13 5,192]

38 minutes ago, Cory Collier said:

What I'm saying is FMC and FSX are always in agreement on the amount of fuel left, so your statement is invalid. 

Feel free to have a go at it yourself :) fire up 747 and set the tanks to 25% in FMC....you'll see that FSX says you got 25%.

http://prntscr.com/iw7x3f

http://prntscr.com/iw7xhl

No. My statement is not invalid. I told you that we custom code our fuel model (fact), and that you should ignore the fuel interface (not really a true or false thing as much as an instruction). I did not say that they would never match. That isn't invalid.

You're welcome to try to prove me wrong on various things, but the end result is that you're going to be wasting time proving I'm wrong about something I have way more experience and knowledge on, when we could be trying to troubleshoot your issue. As it stands, it seems like a simple issue: you simply aren't planning/flying properly.

38 minutes ago, Cory Collier said:

This STILL doesn't explain the random high fuel consumption issue.

We already established that you did not follow the proper profile. You were flying the MAX ALT profile. That isn't how the aircraft is set up to fly. That isn't how any fuel planner (or the FMC, for that matter) sets up its predictions.

So far, you have provided zero evidence that supports your claim. I asked for your numbers earlier. None were provided. Instead, I got some worthless attempt to prove me wrong on something inconsequential.

The fuel model is custom coded. I know this to be a fact. You're welcome to disagree and try to point to random % values matching, but it isn't going to fix the issue you're having.

39 minutes ago, Cory Collier said:

As we speak, I'm doing KDFW - YSSY, got about 2720nm left to go and as you can see have 35% fuel left (which is enough). From take-off to FL3000 I climbed at 1500fpm, and from there dropped it to 500 then 400 then eventually to 300 (it was either that or stall out).

As you climb, V/S will decrease. Have you flown the tutorial? Sounds like you might not have a firm understanding of proper aircraft procedures.

[Cory Collier 2]

hmmm it seems you're not listening....

In My ORIGINAL post, I stated, "I wasn't having this problem, until yesterday when ONCOR shut off the power to do some maintenance."

Before that I could do KDFW - YSSY and back (full tanks on take-off both ways) and STILL land with fuel in the tanks.

I don't know what numbers you're wanting... you didn't exactly specify. "What were your fuel numbers?" doesn't tell Me what you need..

[VHOJT 172]

The fact no-one else has any issues with PMDG 747 fuel is probably telling it is something on your end.

I have extremely accurate flights once I figured out a rule to use for the fuel bias in PFPX.

You should be climbing in VNAV, not V/S.  VNAV is the optimum and most fuel-efficient way to climb to cruise altitude.

What is your ZFW?  What is your fuel load at takeoff?  What altitudes are you flying at?  How did you climb - climbing in V/S is inefficient and potentially dangerous - no real world operator would do this as if your attention lapses you could easily end up in a stall?  Are winds entered in the FMC?  Did you use CLB, CLB-1 or CLB-2?  Are you flying an optimum profile?  What is your route - the routes change frequently based on the winds (well, basically they change daily, and seasonally)?  What is your cost index?  What flap retraction scheme did you use?  Did your SID/ATC hold you at low level for a while?  Were the winds close to what was predicted in the plan?  Was the aircraft in trim for climb?

I could go on all day...but all of these things affect your fuel consumption and change for each and every flight.  Just because you did SYD-DFW one day with x payload, doesn't mean you can do that the next day.  I've been simming a lot of MEL-DXBs, and the max payload I can take varies considerably each flight due to winds/temps etc. 

 I honestly think your problem is a planning or flying problem.  Kyle is definitely listening so it's probably best not to aggravate him when he's trying to help.

Check out some flight planning tutorials, or ask questions.  There are plenty of knowledgeable people on this forum and over at PFPX, and probably SimBrief but I haven't looked in depth over there.

Good luck!

Edited March 25, 2018 by VHOJT

[downscc 1,327]

11 minutes ago, VHOJT said:

I have extremely accurate flights once I figured out a rule to use for the fuel bias in PFPX

Same here.  Even then, the bias is just one data point sample so I use it judiciously. For example, the actual fuel flow measurement is compared to what the PFPX data suggests it should be; however this is done at specific weight, flight level and SAT.  I try to be at a representative data point to ensure I'm not taking a sample at the edges of the PFPX data envelope.  My typical bias values for B744 GE is about 1.5%.  This is getting pretty close.

[scandinavian13 5,192]

4 hours ago, Cory Collier said:

I don't know what numbers you're wanting... you didn't exactly specify. "What were your fuel numbers?" doesn't tell Me what you need..

All of them.

Any possible number you can hit me with, honestly. The more data, the better. So far, all you're saying is "this isn't right - it's obviously wrong."

How are you determining this? "I'm running out of fuel!"

The plane on your hard drive is going to behave like the real one. I need numbers that prove you are planning the flight to the same realistic standard. "I departed with full tanks" and your commentary on flying the MAX ALT profile prove otherwise. Prove me wrong.

I'm literally here trying to help you. Help me help you instead of claiming that I'm not listening. Excuse me for a getting a little side tracked when you came back into this thread 19 days later in an attempt to call me a liar about something.

[Cory Collier 2]

THIS is what doesn't make sense...

I do this route PRETTY much the same way every time.....then suddenly My power is shut off (granted I wasn't alone..lol) and the plane starts to have issues. That's what's throwing Me off, ya know?

Common sense dictates it SHOULDN'T do that......so I'm completely baffled. 

I usually take off uh 16L or 16R out of Sydney, full tanks (payload set to empty), climb to 38000 (I have that set as My cruise alt in my FSX and FMC flight plan - both of which are done by simbrief and IF I don't go straight to that...ATC is just gonna gripe at Me). I climb at around 245 kts while under FL100, per the norm and then accelerate to around 270 or so, while climbing at 1800FPM until I hit about FL2500 or so then I slow My climb to 1500 and then around 3000 I drop to about 500 eventually dropping it to 200 fpm until I'm at cruise alt. (yeah I could probably cruise for a while at 350 until I burn off some fuel then climb to 380). 

I've done this....God knows how many times, no issues until that one day. As I type this I'm on approach (15nm out) to Sydney

[Cory Collier 2]

GRANTED this is for FS9....but hey it still works lol. I do better with stuff like this as it's in writing and I can just leave it up, rather than vids...

http://smithplanet.com/fs2004/pmdg/

 

found this when looking for a startup guide. by now, I just leave it up, and only glance at it from time to time when I THINK I'm forgetting something....

Edited March 26, 2018 by Cory Collier