I decided to venture back into the Su9 beta again to check it out and I thought I’d take a look at the 4 engine fail people have been getting on Concorde when using reheat.
After playing with weather temperature settings and monitoring the point when the engines fail in developer mode engine debug screen, it seems like the trigger point for the failure is when approx 170,000lbs/hr fuel flow rate total for all four engines is exceeded. If I adjust the ambient temperature up so that the flow is just below this value, I can sit on the runway with all 4 engines on reheat until the cows come home.
I played with many fuel flow related parameters in the engines.cfg file and, to cut a long story short, the only change that could keep the fuel flow under this max cap at any normal operating temperature was to change AfterBurnThrustSpecificFuelConsumption from 1.39 to 1.1. This puts a cap on max fuel flow at 167200 lbs/hr and allows reliable reheat and engine operation all the way up to 60000 ft, with the obvious side effect that fuel flow with reheat on is about 20% less than it should be. And yes, I did try changing the fuel_flow_max parameter, but it did not stop the engines failing as they have been in SU9.
I know this is a bit of hack work, but I was just wanted to get this aircraft operational in SU9 and give DCD a heads up of what triggers the issue and where to start looking if SU9 comes out with this issue baked in.