Insufficient fuel warning 747-8

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Are you using Developer Mode or made changes in it?

Regular mode, no changes

Which aircraft are you using that experiences this issue?


Brief description of the issue:

I get a warning on the CDU "insufficient fuel ", even when I know there is more than enough. I even set the fuel with 100k lbs extra in anticipation of a “holding pattern” (I wasn’t sure when I would get home), and I still got the warning.

Provide Screenshot(s)/video(s) of the issue encountered:


Detailed steps to reproduce the issue encountered:

Load the fuel indicated on the simbrief or more. You are likely to get this message

PC specs and peripheral set up:

Ryzen 5800x, Radeon 7900xt. Thrustmaster 1600m stick, Honeycomb Bravo quad, CH pedals.

Are you using DX11 or DX12?


Are you using DLSS?


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Do you have the same issue if you follow the OP’s steps to reproduce it?

Provide extra information to complete the original description of the issue:

Are you using DX11 or DX12?

Are you using DLSS?

If relevant, provide additional screenshots/video:

Your reserves are too high (129 klbs). That means that you will reach the destination below the set reserves amount.

I don’t think so. I get that warning when I follow the Simbrief recommendations as well. Then magically, I land within the projected use parameters.

Can you share the simbrief flight plan? It seems odd that the reserves is 129,000 lbs. if you put max reserves (90 min) is ~ 27,000 lbs for the 747-8

My post clearly said I had added an extra 100k, over and above the flight plan. I was just doing this extreme to prove a point.

and your cost index is like…really high.

Where were you flying to/from and i will attempt to recreate


Not sure about your route, any discons or open end on the route? You run through the route and confirm no waypoints off your planned route?

As I stated in my original post, I purposedly added 100K extra. I don’t just test normal, I test abnormal as well. So of course the CI is going to be high, because I am carrying extra weight. And as I stated, I planned for an extended hold (up to several hours). What you see is when I was still in the original screenshot was before even taxiing at TTPP. I have also gotten “Insufficient Fuel” warnings when taking exactly what the Simbrief has offered with everything on auto and no modifications. They can be cancelled out, but why do they appear in the first place, especially when the plane is overly fueled?

I think you have a miss conception of some of the definitions:

  1. Cost Index is not dependent on how much fuel you are carrying. Low cost index = fuel efficient flight (i.e optimum cruise speed, optimum FL); High cost index = fast flying (i.e. high cruise speed). This is based normally in airline policies.

  2. The final reserves that you put in your FMS should be the 30 min fuel stated in the flight plan (in your case 8,842 lbs not 129,000 lbs). I still dont understand where your 129,000 lbs is coming from.

The FMS makes a calculation based on how much fuel you will arrive at your destination (including arrival airport+contingency+alternate+taxi) and crosscheck with the the reserves you put in the FMS. If that calculation shows that its lets say 120,000 lbs for example then it will give you the warning you are showing (not necessarily meaning that you will not make it to your destination)

At least thats what I understand. I might be wrong.

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Going off of your Simbrief flightplan, even with the huge 100’000lbs extra fuel, your FINRES + ALTN is only 22088, therefore you need to set roughly 22.1 in your PERT INIT Reserves box in the CDU. You’ve set 129.0. Because in your current state the aircraft is calculating you’re going to land with below 129’000lbs of fuel onboard, it therefore is throwing the Insufficient Fuel memo. This is not a bug and is correct for the real world aircraft.



Maybe this will help when setting up the CDU. This is how I prepare my flights using FlightAware, Simbrief, TopCat, the Zibo Mod 737NG Electronic Flight Bag and the 737NG Flight Management Computer.

I misspeak a couple of times, but I think anyone can follow along.

See marked solution.