CF104

I don't think there's a debate going on in regards to the flight behavior of the F-4E. For me at least, it's the speed of the trimming itself. I have no problem making small trim adjustments as required. As long as the adjustments don't give me 1000-2000 fpm excursions. With my hardware, WinWing Orion2/F-16EX joystick, I can't "flick" the hat quick enough to get the "tiny inputs" you're talking about. And this is what I think the discussion here is about. If I could get it down to trimming with "tiny inputs" via my hardware I'd be happy to trim the jet all day long. As an aside, I have an original B8 grip in my collection and the trim hat on it has very aggressive centering. I doubt you could do a "tiny input" of less than 100ms on the B8 hat. My hardware has much lighter centering and I'd more than likely halve the time per click. Unless a real B8 grip was used to program the current trim timing I'd say there's some valid comments/concerns from users here. Cheers, John

Maintenance are the ones who ensure that these numbers are met. The guaranteed part is a goal to be achieved with minimal gains on improvement once it's met. Rarely will they be exceeded by any significant margin. I've been in aviation maintenance for the last 42 years and working on turbine powered aircraft for the last 34. In my experience one may occasionally see a up to a 1 second improvement on the acceleration numbers but usually they're bang on the numbers for a good condition engine. Even if they come close to the -11 engine as shown in the YouTube TF-104G video or the -15 burst chart it'll be way more realistic than the instant response it currently has. Cheers, John

Hi All, Here is the J79-GE-17 test cell idle to mil guaranteed acceleration time chart. It shows that the fastest accel time is 5 seconds at 50°F(10°C) which is at the bottom of the bell curve. cooler or warmer temps will cause longer acceleration times. Cheers, John

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