Currently on board the default PMDG Qantas VH-OJM aircraft getting ready for a transpacific flight to Sydney. 

I cannot input a fuel value that will result in the ground weight exceeding 391.4 metric tons. Is this because I'll be exceeding the MTOW? According to the FCOM operating limits MTOW is higher than 391.4 tons for a passenger 747-400 although that's for a PW. 

 

ZFW is 228.8 so I can't put in anything higher than 162.6 tons of fuel.

I haven't checked with other engine variants if the max weight on the perf page for manual fuel input is also 391.4 metric tons.

-Angelo Busato

 

Welcome to the reality of commercial aircraft operations. Balancing load for fuel is normal. You'll never get a full load full distance. In your scenario, you'd be pressed to take minimum fuel for sector, to do a re-clearance plan, and look at alternates. Transpacific to Sydney means you'd effectively need a closer destination with Sydney as alternate, and try to save fuel enroute until you had enough to reach Sydney with enough for another alternate as per original plan.

Only if you can't do that would the Dispatcher reluctantly remove freight, to allow you more fuel. This is usually more preferable to an enroute tech stop for fuel. Cost a lot less. After freight would come bags, then passengers. With all the compensation problems and suchlike.

 

Enjoy!

Just a quick check - is the fuel density simulation causing this - check the introduction manual.  If it is, you can always input a higher fuel density figure to allow you to load the weight of fuel you want.

And just so as you know, if you are doing an Australian airline flight, they don't plan an alternate airport at all unless it is necessary (i.e. ceiling/vis below airport alternate criteria, crosswind etc, some other adverse condition).  Assuming no adverse conditions, planning to arrive in the terminal area with around 13 tonnes of fuel for Sydney would be normal (30 minutes reserve, 30 minutes contingency/variable reserve, and 20-30 minutes ATC holding fuel, and any fuel needed for the approach/landing).  Australian airlines often cap the 10% variable reserve at around 30 minutes max, using a decision point to decide the last point they could divert to a suitable alternate enroute (sort of like a redispatch, but the variable reserve is capped)...  I have written a few notes on Australian flight planning with my flight plan formats on the PFPX forum.

Edited September 1, 20187 yr by VHOJT

3 hours ago, VHOJT said:

Australian airlines often cap the 10% variable reserve at around 30 minutes max, using a decision point to decide the last point they could divert to a suitable alternate enroute (sort of like a redispatch, but the variable reserve is capped)...

Fascinating...  I marvel at the Sydney - Johannesburg flight and have performed in a couple of times in simulation.  What would be the decision points on that?  Basically, there is nothing between Perth and Durban.

I believe McMurdo Station in the Antarctica has an ice runway capable of supporting 747-400's, but I don't know if that's put into the calcs. 

 

 

14 hours ago, VHOJT said:

Just a quick check - is the fuel density simulation causing this - check the introduction manual.  If it is, you can always input a higher fuel density figure to allow you to load the weight of fuel you want.

And just so as you know, if you are doing an Australian airline flight, they don't plan an alternate airport at all unless it is necessary (i.e. ceiling/vis below airport alternate criteria, crosswind etc, some other adverse condition).  Assuming no adverse conditions, planning to arrive in the terminal area with around 13 tonnes of fuel for Sydney would be normal (30 minutes reserve, 30 minutes contingency/variable reserve, and 20-30 minutes ATC holding fuel, and any fuel needed for the approach/landing).  Australian airlines often cap the 10% variable reserve at around 30 minutes max, using a decision point to decide the last point they could divert to a suitable alternate enroute (sort of like a redispatch, but the variable reserve is capped)...  I have written a few notes on Australian flight planning with my flight plan formats on the PFPX forum.

I have changed the fuel density but the cap stays at 391.4, the FCOM says MTOW is 394.6. I'm missing out on four tons here and the only to input it is to refuel it using ground ops but of course once I'm fueled up I can't get fuel out to fine tune my load out. 

I landed with 16 tons, had YSCB as an alternate,15 minute contingency, FAR for 30 minutes and no extra fuel. Estimated remaining fuel was 12.9tons but landed with 16. Bit sad about it as I could have loaded more. 

-Angelo Busato

Edited September 2, 20187 yr by killairbus

12 hours ago, downscc said:

Fascinating...  I marvel at the Sydney - Johannesburg flight and have performed in a couple of times in simulation.  What would be the decision points on that?  Basically, there is nothing between Perth and Durban.

Dan,

A PNR (Point of No Return) and/or Critical Point would normally be calculated for situations like this and one of the reasons why a four engined aircraft like the 744 is preferable from a flight safety perspective; if only because (unlike its twin jet cousins) it doesn't have to land at the nearest suitable airfield after suffering a single engine failure.  The mere thought of having to fly even half way along this route on one engine sends shivers down my spine!

Dan,

As far as decompression/engine failure scenarious:
Eastbound you sould do say: FMEE (Reunion) or FIMP (Mauritius) paired with YPPH (Perth), then YPPH with YPAD (Adelaide) or YMML (Melbourne) , then YSSY (Sydney) - that covers your decompression/engine out scenarious without any extra fuel generally.

As faras  westbound - basically the same in reverse, but you'd use FMEE/FIMP with FALE (Durban) if possible to minimise any extra fuel required for decompression, and then FALE-FAOR (Johannesburg).

As far as a decision point with regard to the contingency fuel, it is basically a redispatch, but using a fixed amount of variable reserve fuel.  I think it even shows on the ATC flight plan as RIF (redispatch).  Eastbound would be something like YSCB (Canberra), westbound FALE.  Bascially it is the last point along the route where you can divert to the enroute alternate.  A figure of minimum fuel to proceeed past this point to your destination is also given - which will basically be flight fuel from decision point to destination + 10%, fixed reserve and any holding required.  So essentially it is a redispatch with a minor variation (capped contingency fuel).  Australian airlines plan basically all medium/long-haul flights in this fashion, and will only carry a destination alternate if necessary.  Wherever this to be an advantage using this method vs 10% of total flight fuel for the variable reserve, you could assume they would be using it.

There are various other methods airlines can use, such as a proper redispatch, if they want to reduce contingency fuel further, rather than boot off payload.

It is fairly common knowledge around the web that QF 744s have extra oxygen bottles that allow for depressurised flight at 14,000ft for a considerable number of hours, and even higher for shorter periods. This would help with minimising decompression fuel vs having to go down to the usual 10,000ft for hours.

If you're interested, I have writtten a guide to planning flights in an Australian-fashion with the formats on the PFPX forum.

Cheers,
Rudy

 

Edited September 2, 20187 yr by VHOJT

Still very confused as to what the issue is/was...

I still suspect density

Edited September 3, 20187 yr by VHOJT

8 hours ago, scandinavian13 said:

Still very confused as to what the issue is/was...

On the perf page, if you manually insert a fuel value that will result in the ground weight of the aircraft exceeding 391.4 tons, the FMC will not accept that value. 

I want to know why because if the FMC is sensitive to keeping the plane within MTOW, it should allow to insert a value up until 394.6 tons as that is the MTOW in the FCOM manual for a standard passenger -400.

So it seems the FMC could be telling me that I am exceeding my MTOW when in fact I still have little over 3 tons to spare. 

-Angelo Busato

Edited September 3, 20187 yr by killairbus

Very strange.  Does this happen with the RR as well?  I just loaded 165.4 tonnes with a ZFW 232.5 (ramp weight 397.9) and all was okay.

19 minutes ago, VHOJT said:

Very strange.  Does this happen with the RR as well?  I just loaded 165.4 tonnes with a ZFW 232.5 (ramp weight 397.9) and all was okay.

Yes I'm in the RR.

Did you input the 165.4 manually? Because it will go past 391.4 if you fuel the plane via ground ops no problem, but it doesn't allow me to insert it manually on the perf page. 

-Angelo Busato

Edited September 3, 20187 yr by killairbus

I had the plane fuelled alreday so just confirmed the amount already in the INIT REF page.

I always set my fuel load to 10% via FS Actions, after loading the default cold and dark panel. Then I imputed the value in Init Perf, only to get "Invalid entry." 

-Angelo Busato

Edited September 3, 20187 yr by killairbus