PMDG 737 -900 puzzle

[snakeboy]

Maybe you pmdg 737 owners can help with this one. Every time I do a trip I manage to get the fuel just right, but 20 mins or so after
takeoff I get pinged by the fmc with the message "insufficient fuel" at destination. Then slowly the destination fuel starts to increase so
that when I come into to land fuel quantity is as it should be. Is this normal or a bug?. It's just a little bit worrying getting this 20mins into
the trip. First time I got this I was messing with altitudes, speed and the like 'cause I thought I would run out of fuel, but it's not an accurate
fuel forecast.

[vollmey]

I've gotten that once flying an Alaska Airlines flight from KMCO-KSEA in the 900. I had inputed the winds and even with full tanks the FMC
figured out as I was climbing that I was going to be short. But, remember the higher you get the more effcient a jet engine gets so
everything comes back to normal.

So I would say it's not a bug just the FMC doing it's job. I usually take off with 80% fuel except on those long cross country trips
westbound.

I still can't figure out how Alaska's 900's fly across the country westbound into a 100knt headwind or so in the middle of winter. With a full load it's awfully tight, at least in my PMDG 900.

Hope that helps a bit.



Post Edited ( 10-25-05 04:29 )

[SWAFO]

As Dave mentioned, this indication is not a bug, it's just the FMC doing it's job. Keep in mind that the FMC is a computer, and does have
limitations, and small bugs. It's nothing to really worry about (especially imediately after takeoff), and doesn't really become an issue
unless you get this notification later in the flight. Good fuel planning, and fuel management would produce an economical flying
environment in which this notification would only be advisory information.

[NLRalph]

Snakeboy,

Are you using FSNAVIGATOR? I have the same problem from EHAM (Amsterdam Schiphol) to LTAI (Antalya, Turkey) but only when i am
flying with FSNAVIGATOR

[snakeboy]

Thanks for all your replies.

NLRalph wrote:
Snakeboy,

Are you using FSNAVIGATOR? I have the same problem from EHAM (Amsterdam Schiphol) to LTAI (Antalya, Turkey) but only when i am
flying with FSNAVIGATOR

I just use FSNavigator to work out my fuel which after a lot of tweaking is always spot on.

[pegase]

I manage to get the fuel just right, but 20 mins or so after takeoff I get pinged by the fmc with the message "insufficient fuel" at
destination.

20 minutes is almost the climb time and when the fuel per hour consumption is at it's highest. So, if the FMC simply make the proportional evaluation
for the remaining time, This could explain ?

If you look on the FsP report just after climbing, you will aslo be alarmed by the fuel flow because it assumes that for all the flight the fuel flow
will be the same.
Yesterday I flew from CYUL to KJFK, a very short flight 288 nm 1h15mn block time. I took just what was necessary to flight + Go around + 1 hour. and
loaded full cargo capacity (money... money...)

Just at the end of the climb, I checked the FsP report which showed me that I had some tenth of minutes flying left and MINUS some tenth with one
hour reserve. But ended the flighrt with some 14 000 lbs in the tanks.

In FS navigator, for each plane you can enter 3 fuel flow values
For climb
For cruise
For descent.

With these values, it calculate a quite acurate total fuel consumption for any flight. I don't know anything about FMCs but may be ther is a way to
enter such data in it ?

[AeroJim]

to buy the 800/900 737 do i need NG first, i was wondering because i am looking to purchase and the 800/900 is 10 bucks cheaper then
the NG yet the NG is an older version.

[snakeboy]

Hmm interesting. Seeing how the FMC knows what the cruising height, distance of flight/legs and fuel you have on board and all the
other information you give it, and if you let vnav take over, you'd think it would be smart enough to take climb fuel rate into account.