What fuel flow units should be used in constructing the

corrected_n2_from_ff_table for a jet engine in engines.cfg? The description in

the SDK documentation does not specify the units. In the available examples I

can find (CJ4 and Longitude), the fuel flow numbers in this table are very

small (less than 1.0). For corrected values in general, the SDK references

*Gas Turbine Parameter Corrections* by Volopini. I do not have a copy of his

book, but in a conference paper by the same name, that author uses pounds per

second (lbs/s) as a standard unit for fuel flow. I built a

corrected_n2_from_ff_table from real-world engine data using lbs/s, but the

plane’s idle N2 value in the sim was too high (76.7 instead of an expected

value of 48.6). I tested other power settings, and after some trial and error,

I found that multiplying my lbs/s numbers by 2.47 produced N2 numbers that

were close to accurate. I don’t know of any units that would have such a

conversion factor. Does the sim expect normalized values, where fuel flow is

expressed as a fraction of fuel_flow_max?

This table is a misnomer. An error going back to the old FS9/FSX days. It will

not set fuel flow, instead it tunes spool up rate based on RPM. I find that

the table is normalized, and a good starting point is a value of 1.0 for 100%

CN2.

As far as I understand, the table will definitely set fuel flow if

use_corrected_N2_from_FF_table=1. Sylvain’s answer here also indicates that:

<https://devsupport.flightsimulator.com/questions/966/jet-engine-model-

equation-fuel-flow-and-fuel-consu.html?childToView=2293#answer-2293> After

looking at multiple answers here and reading the SDK description again, I

discovered the solution: The corrected fuel flow is normalized by the static

thrust of the engine. The table expects fuel flow numbers that are calculated

as follows: corrected fuel flow (in pounds per hour) divided by static thrust

(a constant defined in engines.cfg). The SDK description mentions static

thrust once, but in every other place, it only mentions corrected fuel flow. I

assumed that static thrust was a typo, or a leftover thing from an older

version. If possible, I would recommend changing this description to make it

more clear. I will refer to this parameter as (corFF/staticThrust) below. In

most cases, this number will be less than 1. Also, it’s worth pointing out

that the example in the SDK has the incorrect order. Each item in the table

begins with a (corFF/staticThrust) value. The documentation should look like

this: (corFF/staticThrust):corrected_n2,(corFF/staticThrust):corrected_n2