Originally Posted by
David Gladwin
Alisdair, , my take during coffee time!
If it happens ONLY in the air then the difference is ram pressure in the intake ( P1 in RR terminology) in flight.
Perhaps that ram rise is resulting in too much air for the fuel being supplied when idle is selected and low fuel delivery is demanded causing too “lean” mixture and flameout.
As you know, fullsize engines have AFRCUs to manage this, we don,t.
My only suggestion is to arrange a slow function, via your transmitter, on throttle for the last quarter or so of the rpm range, a bit like the flight idle setup on the JT 8 on the 737 when in landing config.
Anyway , good luck with finding the problem !
PS of course you could arrange a spill door to open to dump excess air in the intake at low rpm, works on Concorde !
Coffee finished !
Thanks for the input David.
I take you point about full size practice, but they are squeezing the boundaries of what is possible to eek out another half percent of efficiency.
Model jets are more like the old Nene or Derwent.
But, it is LACK of ram air that seems to be the problem. I don't think my intake configuration is much different to most other model jets. It is neither full-on ram air intake nor convoluted suck-it from where you can. It should act like any other model turbine.