correct as is F-5 no rudder input needed to maintain coordinated turns

[SMH]

F-5 no rudder input needed to maintain coordinated turns. It didn't used to be this way but now, even when turning as hard as you can, the ball stays perfectly centered without requiring any rudder input. That can't be right, can it? Sabre and MiG-15 also seem to have this issue now. 

[Nealius]

F-5 has always needed almost no rudder for coordination as long as your yaw dampers are on. I asked CW Lemoine about this as he flies T-38s in real life and his response was "stepping on the ball isn't a thing in fast jets."

 

However

 

If you are in a high-AoA fight at slow speeds you will need rudder to stay coordinated, or to turn at all. In a flat scissors you will be rolling with your feet in the F-5 just as you would in the Tomcat. 

Edited May 6, 2021 by Nealius

[bbrz]

Just take a look at the short wingspan, compared to the fuselage length. Not much surface sticking out to the sides to induce adverse yaw.

 

On most jets you generally don't need rudder at a low AoA to keep the turn coordinated. 

 

 

Edited May 6, 2021 by bbrz

[TLTeo]

What others have said. Jets requiring rudder input are the exception (the Tomcat and F-100 are the only two I can think of off the top of my head), not the norm, and even then it's only really necessary at high AoA.

[SMH]

I disagree. Yeah it's less than in some aircraft but without a FCS controlling the rudder you're going to have some adverse yaw. We have none, no matter how hard you bank. 

Also, I know for a fact we used to have it in the F-5 and MiG-15. (Probably Sabre too.) But something changed in the FMs of all three. Not sure when that happened. Don't remember it in any change logs. All 3 feel less realistic to me now. 

[Snappy]

2 hours ago, SMH said:

I disagree. Yeah it's less than in some aircraft but without a FCS controlling the rudder you're going to have some adverse yaw. We have none, no matter how hard you bank. 

Also, I know for a fact we used to have it in the F-5 and MiG-15. (Probably Sabre too.) But something changed in the FMs of all three. Not sure when that happened. Don't remember it in any change logs. All 3 feel less realistic to me now. 

 

I can‘t speak for previous iterations of the FM , whether it was different or not.However even aircraft without sophisticated FCS can have simple or more complex yaw dampers and the F-5 does have yaw dampers far as I‘m aware.These can and do remove the need to add manual  rudder for flying coordinated turns within a reasonable envelope .So the current FM is not necessarily the unrealistic one.

 

Did you check a real F-5e flight manual by chance? It should say whether or not manual rudder is required for coordinated turns.Theres one in download section of DCS homepage, check that.

 

regards,

 

 Snappy 

 

 

Edited May 26, 2021 by Snappy

[SMH]

49 minutes ago, Snappy said:

 

I can‘t speak for previous iterations of the FM , whether it was different or not.However even aircraft without sophisticated FCS can have simple or more complex yaw dampers and the F-5 does have yaw dampers far as I‘m aware.These can and do remove the need to add manual  rudder for flying coordinated turns within a reasonable envelope .So the current FM is not necessarily the unrealistic one.

 

Did you check a real F-5e flight manual by chance? It should say whether or not manual rudder is required for coordinated turns.Theres one in download section of DCS homepage, check that.

 

regards,

 

 Snappy 

 

 

 

The yaw damper, like the pitch damper, is there to reduce oscillation. They don't bias the rudder's central position to counteract side-slip like an FCS does.

Why do you suppose there's a ball just below the gunsight? Why would you need one in a plane that never side-slips?
 

[TLTeo]

13 minutes ago, SMH said:

Why do you suppose there's a ball just below the gunsight? Why would you need one in a plane that never side-slips?

Obviously. That is why the Mirage, Hornet and Viper have one right /s

[Snappy]

On 5/26/2021 at 9:56 PM, SMH said:

The yaw damper, like the pitch damper, is there to reduce oscillation. They don't bias the rudder's central position to counteract side-slip like an FCS does.

Why do you suppose there's a ball just below the gunsight? Why would you need one in a plane that never side-slips?
 

You have some misconceptions I think. I flew an aircraft with a yaw damper&without FBW  and it required zero additional manual rudder for coordinated turns. Also even large transport category aircraft like the 747 still have a ball. It's just visualized differently on the PFD.  But if you must google a bit  and  take a look at the lower part of the ADI cockpit instrument of the older  747-200 or even Concorde .

What do you see there? Do you honestly think these were still flown with manual rudder during normal turns?

 

"Why would you need one in a plane that never side-slips?"  for system malfunctions/limitations ,asymmetrical thrust situations,  incorrect  , unnoticed manual input  etc..

 

 

Regards,

Snappy

 

Edited May 29, 2021 by Snappy

[GGTharos]

The -1 for the F-5EFN doesn't say anything about coordinated turns.   Most mentions of rudder have to do with high AoA handling and out-of-control flight recovery.

I think the only person who could resolve this an SME who has flown the aircraft.

[GGTharos]

It's possible that the appendixes here contain the answer to the question, I just don't have time to look at them:

 

https://www.yumpu.com/en/document/read/43228040/flying-qualities-of-piloted-aircraft-cafe-foundation

[SMH]

10 hours ago, Snappy said:

"Why would you need one in a plane that never side-slips?"  for system malfunctions/limitations ,asymmetrical thrust situations,  uncorrect , unnoticed manual input  etc..

 

 

Regards,

Snappy

 

 

Speaking of asymmetrical thrust, you inspired me to test something.

I idled the right engine, left on full military. As you would expect, ball deflected to the left (about half way through the line), good. Then I banked into a right turn, and the ball centers during the turn, no matter how hard. Okay, you say, that's because the nose-leftward yaw from the right turn is balancing out the nose-rightward yaw from the right engine. (That doesn't explain why the turn is also coordinated when the engines have equal power though but it gets worse...) Now, let's try turning to the left. That should make the leftward yaw even more prominent, right? Maybe send the ball all the way left past the line instead of roughly centered on it?

Nope! When you bank into the left turn the balls moves more towards the center -- almost all the way! 

This seems to reinforce my suspicion that there's a magical centering force in the yaw axis that's somehow related to banking. Almost like auto-rudder is on (but it's definitely not! At least not according to the interface? Might the value in the FM not be seeing that though? That would explain everything I'm seeing in these 3 planes lately.)

Edited May 27, 2021 by SMH

[Snappy]

10 hours ago, GGTharos said:

The -1 for the F-5EFN doesn't say anything about coordinated turns.   Most mentions of rudder have to do with high AoA handling and out-of-control flight recovery.

I think the only person who could resolve this an SME who has flown the aircraft.

Yea you're right, I just checked. Indirectly it does though, under flight characteristics sections-> control effectiveness-> Roll/YAW  . (Its section 6-2 in the manual from 78)  It says quote: 

 

...."Above approximately 20 Units AOA,  roll control with aileron is less effective and rudder is required to coordinate the maneuvres" .

You can possibly deduce the inverse from that statement, below 20 units of AOA no rudder is required to coordinate otherwise they would've written it differently . Which is pretty much what everyone told SMH, i.e. : 

 

Semi-modern jets typically do not require rudder input for coordinated turns until you enter the higher AOA part of their envelope. This is a super generalized blanket statement I know and there are exceptions to this, but you get my general drift. I personally would not expect to have to  add manual rudder for a normal coordinated turn at reasonable AOAs.

Regards,

Snappy

Edit : This also correlates to Belsimteks own F-5 manual statement on this :
"Above 20 units AOA rolling effectiveness of ailerons rapidly degrades due to wing stall as well as to adverse sideslip generated by aileron deflection. The latter can be reduced by proper blend of rudder with ailerons for roll control of the aircraft at AOA greater than 20 units."

 

 

 

Edited May 27, 2021 by Snappy

[Snappy]

26 minutes ago, SMH said:

Speaking of asymmetrical thrust, you inspired me to test something.

I idled the right engine, left on full military. As you would expect, ball deflected to the left (about half way through the line), good. Then I banked into a right turn, and the ball centers during the turn, no matter how hard. Okay, you say, that's because the nose-leftward yaw from the right turn is balancing out the nose-rightward yaw from the right engine. (That doesn't explain why the turn is also coordinated when the engines have equal power though but it gets worse...) Now, let's try turning to the left. That should make the leftward yaw even more prominent, right? Maybe send the ball all the way left past the line instead of roughly centered on it?

Nope! When you bank into the left turn the balls moves more towards the center -- almost all the way! 

This seems to reinforce my suspicion that there's a magical centering force in the yaw axis that's somehow related to banking. Almost like auto-rudder is on (but it's definitely not! At least not according to the interface? Might the value in the FM not be seeing that though? That would explain everything I'm seeing in these 3 planes lately.)

 

Have you switched the STAB AUG YAW on or off for your test?

Edited May 27, 2021 by Snappy

[GGTharos]

Personally, I cannot deduce that.   This refers to loss of stability above 20 units AoA, but it says nothing about what happens before this.  It's not like this AoA is a magical boundary for aileron roll inducing yaw.  This yaw may not cause instability but it could make flight quite inefficient under some circumstances and you'd definitely want a habit of stepping on the ball.  The point at which the side slip starts to lead to instability is really not an argument for not coordinating below this point IMHO.

[Snappy]

29 minutes ago, GGTharos said:

Personally, I cannot deduce that.   This refers to loss of stability above 20 units AoA, but it says nothing about what happens before this.  It's not like this AoA is a magical boundary for aileron roll inducing yaw.  This yaw may not cause instability but it could make flight quite inefficient under some circumstances and you'd definitely want a habit of stepping on the ball.  The point at which the side slip starts to lead to instability is really not an argument for not coordinating below this point IMHO.

Of course it's not a magical /digital 0-1 boundary. I didn't say that,  I just quoted the manual.  It basically says without using additional manual rudder above this approximate value maneuvres become uncoordinated. Probably this handling characteristic becomes clearly pronounced above that value.

Below that point you should also coordinate I agree , but I personally think the stab aug yaw system will do that for you , but  this is only based on my experience with this type of system. However of course I have no hours in the F-5. I can't say how well or not it works there.

So sure, everyone can have their own opinion or  interpretation. 

 

Regards

Snappy

 

Edited May 27, 2021 by Snappy

[GGTharos]

Thanks for the info.  I'm just arguing the piece of text, but yes you're right, all the other input seems to indicate that rudder isn't needed generally.

[SMH]

Flight manuals don't teach you how to fly, guys. Show me a plane's flight manual that does tell you to step on the ball.

I had Yaw damper on. Again, it's just a damper, it doesn't center your yaw for you. Will try it again with it off but expect the same results as my original tests with both engines full military had the same results regardless of yaw damper setting.

Oh and by the way, just tested the MiG-21, which seems way better now than I remember it, and it does exhibit adverse yaw! Not a lot, but noticeable and correctable with the rudder, as one would expect.

Edited May 27, 2021 by SMH

[Snappy]

I give up. You are clearly superior in your knowledge of procedures, aircraft systems, flight characteristics and manuals.

[SMH]

There's no need to be rude guys. I'm testing, sharing my results and explaining my reasoning. As well as citing examples of other modules of a similar technology which do exactly what I'd expect them to. Again, these modules didn't used to be this way. This feels like some new change that wasn't announced, so I wonder if it's a bug. Like if auto-rudder is stuck on for those planes or something simple like that. 

 

[SMH]

Oh and I remember now! A while back auto-rudder was added to the options and defaulted to ON, which caused all kinds of problems until they took it out completely. But what if those 3 planes (and possibly others) still have whatever variable that setting use to control activated?

[SMH]

As expected, same results for the asymmetrical thrust test with the Yaw Damper off. 

[bbrz]

4 hours ago, SMH said:

Flight manuals don't teach you how to fly, guys. Show me a plane's flight manual that does tell you to step on the ball.

If you agree that the T-38 is very similar to the F-5, you are wrong about adverse yaw and what's written in manuals.

 

Quote from the T-38A pilot's briefing notes:

 

TURNS

Aileron deflection produces yaw in the direction of roll (favorable yaw).

Rudder is not required to produce coordinated turns.

Edited May 27, 2021 by bbrz

[SMH]

5 hours ago, bbrz said:

If you agree that the T-38 is very similar to the F-5, you are wrong about adverse yaw and what's written in manuals.

 

Quote from the T-38A pilot's briefing notes:

 

TURNS

Aileron deflection produces yaw in the direction of roll (favorable yaw).

Rudder is not required to produce coordinated turns.

 

Source? (Like, source of your source? I'd also love to know what mechanism supposedly causes that.)

And how does that explain the F-86 and MiG-15 doing the same thing now?

 

[bbrz]

27 minutes ago, SMH said:

Source? (Like, source of your source? I'd also love to know what mechanism supposedly causes that.)
 

I've bought most of my manuals via different sources on the internet e.g. flight-manuals-online.  What 'mechanism'?

I have the impression that you are trying to apply C172 aerodynamics to high performance jet aircraft.

In case you doubt that this is an actual quote:

 

 

 

 

 

 

Edited May 27, 2021 by bbrz