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Old 06-28-2020, 08:19 AM   #1
bilbosmeggins
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Default Pitch trim......

Hi all. Just wondered if the F5 was supposed to be inherently pitchy, or whether it’s just ineptitude on my behalf.

Ordinarily, in a plane that is fairly well trimmed, in a hands-off moment, it will eventually either begin to descend slightly, at which point it gathers speed, and therefore lift, and will gently porpoise itself towards straight and level. Or, at the other end of the scale, if it starts to pitch up first, it will lose airspeed, and generate less lift, and eventually pitch down and regain speed and lift, and again begin the gentle porpoising until it finds it’s happy place.

In the F5, if I go hands off, even for a short while as I set up TACAN, or play with the fuel system, or weapons or whatever, then all hell breaks loose. As soon as I lift my head up, the plane is either pointing at the sky, about to stall, or it’s in a death dive. I always try and trim it as best as I can, but seem to be forever chasing it, or permanently adding some stick input.

I don’t mind any of the above. If it’s meant to be this quirky, then so be it. I actually quite like that it has character. Also wondered if the auto flaps help to exacerbate the situation or not? Anyone else find it to have a wandering nose, or am I alone?
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Old 06-28-2020, 10:46 PM   #2
Bob1943
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I have never flown the real F-5, but I do have many hours in the real T-38, while going through USAF pilot training. The T-38 was very easy to trim up for hands free flying, without the oscillations that you describe. Due to the close similarities between the T-38 and F-5, I would assume that the F-5 would trim in a similar manner.

However, I also have the DCS F-5 module and also notice that is a little finicky to get trimmed hands free for any length of time. I fly with the TM Warthog stick and find that I have to use very quick/short clicks on the trim button to find that magic spot where you can go hands free for any length of time without altitude deviations. Although I do not experience any extreme pitch deviations after letting go of the stick, i.e., within 45 to 60 seconds, I might see the plane drift into a 100-ft per minute climb or dive, which will usually start getting worse without manual corrections. I have the same problem in getting the roll rate trimmed out.

However, in the real airplane, you will be lucky to maintain a completely stable altitude for more than a few minutes without touching the trim button, i.e., trimming is pretty much an ongoing operation in aircraft of that era.

Might also just be that the simulator hardware/software that we use just does not have the same trimming fidelity as the systems in the real aircraft.
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Old 06-29-2020, 02:04 PM   #3
bilbosmeggins
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Quote:
Originally Posted by Bob1943 View Post
I have never flown the real F-5, but I do have many hours in the real T-38, while going through USAF pilot training. The T-38 was very easy to trim up for hands free flying, without the oscillations that you describe. Due to the close similarities between the T-38 and F-5, I would assume that the F-5 would trim in a similar manner.

However, I also have the DCS F-5 module and also notice that is a little finicky to get trimmed hands free for any length of time. I fly with the TM Warthog stick and find that I have to use very quick/short clicks on the trim button to find that magic spot where you can go hands free for any length of time without altitude deviations. Although I do not experience any extreme pitch deviations after letting go of the stick, i.e., within 45 to 60 seconds, I might see the plane drift into a 100-ft per minute climb or dive, which will usually start getting worse without manual corrections. I have the same problem in getting the roll rate trimmed out.

However, in the real airplane, you will be lucky to maintain a completely stable altitude for more than a few minutes without touching the trim button, i.e., trimming is pretty much an ongoing operation in aircraft of that era.

Might also just be that the simulator hardware/software that we use just does not have the same trimming fidelity as the systems in the real aircraft.

You are probably right. I do hope to purchase a proper trim box at some point. One with a rotary, rather than me clicking the hat switch. Should have a lot more fine control then.
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Old 06-30-2020, 01:33 AM   #4
Chuck_Henry
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I think the trim rate in the DCS F-5 is a bit too fast, or each click creates too much change in the hands-off stick position.

I've sank quite a few hours into the Milviz T-38C (which was created for the USAF Pilot Training Next VR sims and validated by actual Instructor Pilots), and the trim is much easier to get stable, much like how Bob1943 describes the real jet.

I wonder if there are any core files that can be tweaked to get something more realistic.
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Old 06-30-2020, 08:12 AM   #5
bilbosmeggins
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File tweaking is a bit of a black art to me. Would much prefer the stock model to be fixed, but I know that’s probably wishful thinking. I’ve just bought the F-86, which is quite a handful, but the trim is so much easier. You’d think it would be a bit of a nightmare, but it’s right where I would have imagined the F-5 should be.
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