CF104

Hi, The J79 acceleration is completely controlled by the Main Fuel Control on the engine. It has an internal scheduling and governing system that can't be influenced by aircraft mounted controls. As it stands the HB engine acceleration modelling is too fast. I've attached the engine burst acceleration chart for the -15 (C/D) which shows a 4.5 second accel time from idle to Mil. I can't find the -17/-19 chart but I'll keep looking. In the meantime, here is another YouTube video of a TF-104G (J79-GE-11 which is essentially the same as a -15) and you can see the burst check does take a good 4.5 to 5 seconds from idle to Mil. As soon as I can find some -17/-19 information, I'll post it here. Cheers, John

I'm not sure of the actual technical manual figures for pitch trim times but using the stick hat I can go from full nose down trim to full nose up trim in 10 seconds. That seems a bit too fast and could be a part of our problems. Cheers, John

MT user with the same issue. I've also had to assign the pitch trim to a rotary encoder on my throttle base which allows for much finer control of the trim inputs. It's a bit of a pain on the approach since the encoder isn't on my throttle levers themselves. Lets hope that HB can make a fix for this as it does detract from the flight experience of the F-4E. Cheers, John

Hi, One thing to consider is that the F-4C has the J79-GE-15 which has a different nozzle and lower operating temperatures than the J79-GE-17 in the F-4E. The F-4E J79-GE-17(without low smoke) has the following parameters: Idle EGT after start is 220°-420°C Idle nozzle position is approximately 7/8. Idle to 80% is mechanically scheduled linear to just below 1/2. 80%to Mil is either mechanically or temperature scheduled to below 1/4. In afterburner the nozzle is temperature scheduled to control the max EGT below 678°C @ 15°C OAT. This is accomplished by varying the nozzle area (anywhere between 5/8 at min and full open at max A/B) as required to maintain this temperature. See the following youtube video. It's a -19 on the test stand with the same nozzle, control system and temps as the -17. Cheers, John