Hello,

Since a couple of days ProSim may import SimBrief PERF into our CDU’s. That’s nice except that I don’t understand some discrepancies (2).

**1/ Using KG as units**

My B738 is defined this way:

I have 103 PAX (10 B + 93 Y as “systems” can’t make a difference between B and Y all PAX are 70 kg with 25 kg baggage). I have 400 kg cargo on board.

That is a total payload of 103 * (70 + 25) + 400 = 10 185 kg.

My ZFW should be 41863 kg + 10179 kg = 52 048 kg (?)

SimBrief says 51 846 kg that is 202 kg **lighter** (not so big… but I imagine you’re using a computer ). Where am I wrong? The difference could result of a computation conducted in LBS with “bad” rounding?

So let’s try with LBS.

**2/ Using LBS as unit**s

My B738 is defined this way:

I have 103 PAX (10 B + 93 Y as “systems” can’t make a difference between B and Y all PAX are 154 lb with 55 lb baggage). I have 882 lb cargo on board.

That is a total payload of 103 * (154 + 55) + 882 = 22,409 lb.

My ZFW should be 92,292 lb + 22,409 lb = 114,701 lb (?)

SimBrief says 114,821 lb that is 120 lb heavier (That seems “better” even not truly perfect).

**As there can’t be conversion or truncation here… I must conclude that I am making some error. Could you tell what it is?**

**3/ A question**…

In this case:

In your opinion what quantity should be considered as “Reserve Fuel”?

(7,998 lb?)

Thank you very much,

Didier