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BKAA
Topic Author
Posts: 4
Joined: Mon Dec 05, 2005 12:13 am

### Accuracy Of Computer Flight Plan

When a flight plan is found inaccurate in terms of fuel and time, but there is no obvious reason lead to that, is there any good method to find out what's causing the problem?

The only data available is sector information like fuel used, flight time and some written fuel figures on a few waypoints out of many.

Thank you.

wilco737
Posts: 7275
Joined: Sun Jun 20, 2004 12:21 am

### RE: Accuracy Of Computer Flight Plan

 Quoting BKAA (Thread starter):is there any good method to find out what's causing the problem?

A lot of information are on this flight plan which we received from dispatch. Wind, temperature, planned flight level, weight, cost index, trim.
You can check if the wind is the same as planned, you can check if the CG was different than calculated. All this could lead to higher fuel consumption. If it is excessive, then you have to check for a possible fuel leak. Usually the reason can be found on stronger headwinds, more forward CG (higher fuel consumption).
You have about 5% (or 20 minutes) of contingency fuel which you can use for that. But of course if you have a clear indication of a fuel leak, you should better land.

wilco737

BKAA
Topic Author
Posts: 4
Joined: Mon Dec 05, 2005 12:13 am

### RE: Accuracy Of Computer Flight Plan

The problem of using less fuel seems to happen on a particular sector across the fleet. The wind and CG are close to the planned.

wilco737
Posts: 7275
Joined: Sun Jun 20, 2004 12:21 am

### RE: Accuracy Of Computer Flight Plan

 Quoting BKAA (Reply 2):The problem of using less fuel seems to happen on a particular sector across the fleet. The wind and CG are close to the planned.

Then maybe some problems in the calculating system. We had this as well. Some factor was added and on an 7 hour flight we used about 1 ton more than planned. But that was a problem with the calculation not with the aircraft. Was corrected at once.

wilco737

CX Flyboy
Posts: 6188
Joined: Sun Dec 26, 1999 6:10 pm

### RE: Accuracy Of Computer Flight Plan

 Quoting BKAA (Reply 2):The problem of using less fuel

Doesn't sound like much of a problem to me!!!

411A
Posts: 1788
Joined: Mon Nov 12, 2001 10:34 am

### RE: Accuracy Of Computer Flight Plan

Our CFP' s are accurate to +- 2%, for nearly every flight.
Type, L1011.
IE: you get what you pay for...

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