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Level turns: Nose always wants to climb


Nealius

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I got the F-5 last weekend and I've been doing some touch-and-go's with it, but I have a really hard time with level turns. I will bank and add rudder to keep the ball centered, but the nose will always shoot up, causing me to bunt my stick forward. The degree to which the nose yaws upward seems directly proportional to my bank angle. At 30° bank or less, I only have to bunt the stick forward a small amount to arrest the nose. At 60° of bank, like when breaking for an overhead landing pattern, I have to shove the stick forward enough that it decreases my turn rate.

 

Am I doing something wrong here? The ball is centered, so I wouldn't think I would need more rudder.....

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Rudder axis not reversed, otherwise my ability to taxi/takeoff would be severely messed up.

 

I'll work on a getting a video with my controls indications on. Screenshot for now:

 

BtFqd5H.png

 

60° bank, very little aft stick, very little left rudder, ball is centered. Note my VVI is about 700fpm. I've had upwards of 1000fpm in similar turns.


Edited by Nealius
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I find the F-5 has extreme big throttle to pitch lag, it starts to accel or decelerate and after sometime it starts to change the pitch attitude, which leads to lots of trim/throttle overcorrection which can be what you observe as well.

Try to trim for landing AoA and control by throttle and you will see. I don't know how realistic it is, might be or might be not, but I don't like how it behaves to throttle inputs.

[sIGPIC][/sIGPIC]

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I find the F-5 has extreme big throttle to pitch lag, it starts to accel or decelerate and after sometime it starts to change the pitch attitude, which leads to lots of trim/throttle overcorrection which can be what you observe as well.

Try to trim for landing AoA and control by throttle and you will see. I don't know how realistic it is, might be or might be not, but I don't like how it behaves to throttle inputs.

I think that's called spool up time and it's quite usual in somewhat early jets though it happens to all of them.

 

 

S!

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I think that's called spool up time and it's quite usual in somewhat early jets though it happens to all of them.

 

 

S!

 

Yeah it could be, I don't really know, I just find my self using a lot of stick force on approach and landings as it is really hard to keep it trimmed and the nose goes all over the place all the time :)

[sIGPIC][/sIGPIC]

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Here is what I do for a visual reference - turn sight to Man and while flying level depress it until the pipper sits on the horizon with the jet is trimmed out. If you're at 300 knots it should be around 18 mils down. Then keep the pipper on the horizon and do a gentle turn. This is great for flying long distances at a constant speed without gaining or losing altitude - it keeps your eyes where they belong rather than staring at your crotch and altimeter. This doesn't work for a break turn because you're slowing down and pitching up so everything is changing constantly. I have eyes away from the instruments during a break turn because I'm near an airport and other traffic. For that I use the AOA Index...

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Yeah it could be, I don't really know, I just find my self using a lot of stick force on approach and landings as it is really hard to keep it trimmed and the nose goes all over the place all the time :)

I'm flying this aircraft lately and I don't find that much of a problem in turns as you say. Check if dumpers are engaged, even if you did in the start up they tend to disengage in flight sometimes.

 

 

S!

"I went into the British Army believing that if you want peace you must prepare for war. I believe now that if you prepare for war, you get war."

-- Major-General Frederick B. Maurice

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  • 3 weeks later...

Change of airspeed, change of trim required. She needs trimming all the time.

 

I suggest you just fly straight and level and just practise changing speed, then trimming for level flight. It will soon become second nature.

 

Never trim in a turn as the forces are different, and you could end up with too much nose-up trim and an aircraft that's hard to control.

 

If you're in combat, trim for max corner airspeed or a bit faster. In turns, the nose will become heavy and you'll need more back-stick, but you should not run out of elevator authority. It will make it easier to fly and you won't need to worry about the trim while fighting. Also, it will tell you your aircraft energy state without looking based on stick position alone.

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If you're in combat, trim for max corner airspeed or a bit faster. In turns, the nose will become heavy and you'll need more back-stick, but you should not run out of elevator authority.

 

Quick question to make sure I am understanding the control system of the F5 correctly (sorry OP, not trying to derail, I'll make a new post if this isn't a one-answer deal). I thought with an all-flying hydraulically actuated horizontal and an electric trim system that just adjusts the spring feel system to the stick, the full 17 degrees of up elevator should always be available, so elevator authority should have nothing to do with trim position. (IE, stick force would be higher, but the mechanical stop of the stick should be reachable even with more nose down trim than required for the current flight state). Am I missing something here? Thanks.

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Quick question to make sure I am understanding the control system of the F5 correctly (sorry OP, not trying to derail, I'll make a new post if this isn't a one-answer deal). I thought with an all-flying hydraulically actuated horizontal and an electric trim system that just adjusts the spring feel system to the stick, the full 17 degrees of up elevator should always be available, so elevator authority should have nothing to do with trim position. (IE, stick force would be higher, but the mechanical stop of the stick should be reachable even with more nose down trim than required for the current flight state). Am I missing something here? Thanks.

 

Your understanding is correct. DCS is accurate; many other sims are not. It's a trim-force system. However, we have spring-return-to-center sticks, so if we let go, they bounce to center, which may not be where the trimmer would actually trim the stick to. As a hack, when we trim the sim, we trim the stick back to neutral *for our hardware*.

 

I'm thinking of making a trimmer system that works like reality. Any takers?


Edited by Tiger-II

Motorola 68000 | 1 Mb | Debug port

"When performing a forced landing, fly the aircraft as far into the crash as possible." - Bob Hoover.

The JF-17 is not better than the F-16; it's different. It's how you fly that counts.

"An average aircraft with a skilled pilot, will out-perform the superior aircraft with an average pilot."

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That is called balloning, in aviation, I beleive. Becouse the lift vector is effected by bank angle. Compensate with gradual rudder deflection into the turn, to have a nice coordinated turn. Remember that F-5E has AUTO flaps, and flight control and stabilization system adjust flaps as aircraft AOA changes during banking, which effects lift vector.


Edited by DmitriKozlowsky
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  • 2 weeks later...
If you are holding constant G just vary the bank angle to control your altitude. Don't complicate things by kicking the rudders, messing with trim in the turn or any other such silliness.

 

On TRIM I agree. Unless pilot wants to orbit hold his aircraft with constant bank angle.

On not using rudder to compensate for YAW deviation, respectfully, I differ. Ballooning of nose during banking turns, is compensated by slight rudder deflection into the turn.

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On TRIM I agree. Unless pilot wants to orbit hold his aircraft with constant bank angle.

On not using rudder to compensate for YAW deviation, respectfully, I differ. Ballooning of nose during banking turns, is compensated by slight rudder deflection into the turn.

 

It is a fairly simple math problem.

 

Maintaining level flight in ANY aircraft while turning requires X G load for Y bank angle.

 

The OP mentions 60 degrees of bank which requires 2 G's to maintain level flight. Any more G and the aircraft will climb and any less it will descend. In a steep turn, the corrections are made to the bank angle and the amount of back stick. Its easiest to hold constant back pressure to maintain constant G and vary the bank angle to control altitude.

 

In a jet, especially a swept wing jet, kicking the rudders is not going to have a good result.

 

Its a pretty tough task, especially in a simulation to precisely nail exactly 2 G and 60 degrees of bank but one that you learn to do with practice. It isn't about freezing the controls in one position. Like all of flying, it is about constant correction until the corrections are so small and accurate it looks like you aren't correcting at all.

 

Of course, that kind of flying is only possible in a real airplane because you feel the change long before you see it. However, simulations can hone your skills to a very high level because in certain ways they are harder precisely because you can't feel the forces you do in the real thing.

 

Trying to correct with rudder is definitely not how you would do it in a real airplane. You would quickly feel why. Rudder introduces all kinds of unwanted behaviors that seriously complicate the maneuver.

 

I suspect the OP is just pulling too hard for his bank angle. At 300 knots it doesn't take much back pressure to generate 2 G. Since you can't feel it, it is super easy to generate 4 G in the pattern with the F5. Personally I find it far easier and much more fun to fly the break in the overhead at 4G but I always do the airshow overhead pattern a low pass to the break and a 800 foot pattern altitude.

 

 

 

 

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