Limited fuel range

[por930 51]

I have just reloaded my 747X and starting to get back into flights. One thing I noticed when I tried my usual longish distance flight RJAA-YSSY, I keep getting the FMC message, "Insufficient Fuel". I always use the PMDG load/fuel manager and have just embarked upon using Topcat, which recommends much less fuel. On this flight, I had an no cargo/Pax and full fuel tanks, no weather turned on, cruise set at 370, so my range should be approx 7000NM. Stepping though the FMC, I seem to run out of fuel some 3553NM. I have attached the load manager screen.I used to be able to fly YSSY-SAEZ, with limited pax and cargo of course(due to no LR version)

 

So, I have missed some obvious point that eludes me!!

[Richard McDonald Woods 168]

A problem that many have with this message!

 

'Insufficient fuel' is only caused by the remaining fuel becoming lower than the FMC PERF INIT RESERVES value that you have specified.

 

HTH

[Captain Kevin 586]

If you read through the manual and use the fuel planner which is found under the cruise performance section, give that a try and see what happens.

A problem that many have with this message!

 

'Insufficient fuel' is only caused by the remaining fuel becoming lower than the FMC PERF INIT RESERVES value that you have specified.

Sure, that is true, but then again, he also said he ran out of fuel after about 3553 nautical miles. Narita to Sydney according to the Great Circle Mapper is 4211 nautical miles, so he ran out roughly 700 miles short.

[por930 51]

Hi Richard and Kevin,thanks for your quick replies.

In real life,I quite often do this trip QF21/22 YSSY-RJAA-YSSY, so very familiar with flight route and fixes. And yes Kevin, distance is by my calcs, 4254nm. I have flown my PMDG big girl on this route several times, with no fuel issues. For some reason, now I have reloaded my new computer with FSX and PMDG etc, the big girl is different.

I was looking at the manuals - cruise performance sections again today as well as confirming fuel with Topcat, I should have plenty of fuel.

Richard, I usually set my reserve fuel at 10,000.This flight,to see where my fuel would run out, I left it at the default of 4,000. The manual says," The value entered for fuel reserves is used by the FMS to determine an insufficient fuel condition, and will also be used to calculate performance predictions for the flight." My empty a/c should have been able to almost do a return trip on the same fuel load

 

RJAA - YSSY QFA22 flight is:

CUPID Y820 ADKAK G223 DAGDA A337 NOGAK 2500N 14600E 2100N 14648E 2000N 14700E 1500N 14800E 1000N 14900E 0500N 14900E 0000N 15000E 0500S 15100E 1000S 15200E 1200S 15224E 1500S 15300E 2000S 15400E SETER A598 BN H62 CORKY H12 SY

 

Umm, anyway,I will have another go later this week by verifying Topcats recommended quantities and do it manually, then try again. I do not need the ER version for this trip.

[Rations 102]

Are you changing the fuel panel when prompted and performing step climbs, if applicable?

 

According to the PMDG manual, reserves should equal minimum landing fuel + alternate fuel + 0.5 × contingency fuel, which makes sense.

[por930 51]

Hi Owen,

I never made the flight due to the FMC prediction I was going to be way short on fuel, so, never got to step climb issues.

[Ralgh 43]

I say top it of and go and see if you make it and how much fuel you have left. In the 747 I just put my reserves at 0 in the FMC because of that message. It's been a while so I can't remember if you can put enroute winds into the FMC in the 747.

[scandinavian13 5,192]

Umm, anyway,I will have another go later this week by verifying Topcats recommended quantities and do it manually, then try again.

 

There's your problem.

There's a whole section in the FCOM about fuel planning. It's very simple, and if you're at least at a basic level with Excel you can put the calcs in there and save it as a template for later use.

 

Use the manual's method of fuel calcs, or use a planner that does. TOPCAT's is not a fuel planner, it's a fuel estimator so that you can at least get a rudimentary idea of what the fuel might be for weight calcs, not for flight fuel requirements.

[yos233 1]

I have built a calculator using the flight planning data straight from the PMDG manuals. Link to Google Docs

 

It has some additional features like automatic distance calculations and airport weather to make the planning process a bit easier.

[Rations 102]

I have built a calculator using the flight planning data straight from the PMDG manuals. Link to Google Docs

I have also written one in Excel that I just uploaded to the AVSIM Library. It is much less advanced than yours, but gets the job done and follows the PMDG manual suggestions (the only serious "flaw" right now is that it only uses data for cruising altitudes from FL350 to FL400—I didn't incorporate these extremes, as I only fly short-haul flights).

 

However, using direct distances may compromise accuracy in yours. Also, errors may occur with alternate distances. For example, I use VMMC as an alternate for VHHH, but the direct distance is only 20 NM. In real life, a route from VHHH to VMMC may be 75 NM depending on the runway.

 

I like your signature, by the way.

[Captain Kevin 586]

I have built a calculator using the flight planning data straight from the PMDG manuals. Link to Google Docs

 

It has some additional features like automatic distance calculations and airport weather to make the planning process a bit easier.

I had a look at it and am having problems with getting the alternate fuel and subsequently landing weight to display. It just says #REF and putting the mouse over the cell says the cell range wasn't found.

[yos233 1]

I had a look at it and am having problems with getting the alternate fuel and subsequently landing weight to display. It just says #REF and putting the mouse over the cell says the cell range wasn't found.

 

Yeah, sorry about that. It's hard for me to say that it is a Google problem (plus it makes me look lazy), but it is. Sometimes it works and sometimes it doesn't, just out of normal use. I have my flight data stored in another workbook, and it is just not reading the sheet correctly.

 

I'll do something about it.

 

EDIT: Problem fixed. I moved my data from the separate workbook to a different sheet in the Fuel Planner workbook. It shouldn't give #REF errors anymore.

Edited November 29, 2012 by yos233

[speedyTC 195]

TOPCAT's is not a fuel planner, it's a fuel estimator so that you can at least get a rudimentary idea of what the fuel might be for weight calcs, not for flight fuel requirements.

I have found the TOPCAT estimates to be fairly accurate (at least for the FS9 PMDG 747). Can't say anything about the FSX version since I don't have that but I find it hard to accept that the TC calculation is to blame, leaving the OP 700-odd miles short. That is a whopper of an error.

 

Before trying esoteric and convoluted solutions and fuel calcs I'd suggest this was either a glitch or a TOPCAT setup error or not allowing the FMC/IRS systems of the aircraft to fully stabilise before punching in the numbers or maybe even a format entering error in the LEGS pages. Did the OP check the actual mileage the FMC reported after entering the entire route?

However, like I said earlier, I do not know the quirks of the FSX version of the 744. Tokyo to Sydney should be a stroll in the park for the aircraft.

[por930 51]

OK, I think I found the issue. I will confirm later tonight, but a few of the fixes put into the FMC plan were not checked well enough by me . When the FMC gives you a choice, I looked at the Routefinder details and coords and used them to confirm choice. I find for some reason some of the fixes indicated in the FMC a distance of 8000+ NM a very long fix.......I will check later and report back...I thought it so strange my big girl was so thirsty

[Richard McDonald Woods 168]

It is very important to check your route entered into the MCDU using the STEP function before engine start. This will ensure that you have entered waypoints that are near to the great circle. Otherwise you can get routes that are very much longer than you planned.

 

I have found that the TOPCAT B744X FSX fuel estimates are very nearly always sufficient for my frequent long haul journeys, although quite rarely I have had to resort to 'in-flight refuelling' using the PMDG Fuel option.