can not reproduce All ED jets roll when pulling the stick

[dcn]

All ED jets can't loop in vertical plane perfectly when the only input is pulling the stick,they will roll,while third party jets can(I tested AV-8B,AJS-37,C-101,F-14B,JF-17,MiG-21bis).To eliminate rolling I tested them with keyboard 'down' to provide a constant amount of stick pull,and there is no wind,no turbulence and I found it's not due to fuel.Is it bug?

 

F-86F.trk MiG-15bis.trk F-5E.trk FA-18C.trk F-16C.trk F-15C.trk A-10C II.trk L-39C.trk AV-8B.trk

Edited January 19 by dcn

[Insonia]

"rolling" while pulling. or Is it yawing? and the rolling just side effect by slip stream and vstablizer torque?

 

Angular torque IRL can be caused by on-aerodynamic forces like engine gyroscopic force coupling, GCs and aerodynamic factors like unequal disturbances and anomalies from increased AOA. It is unreasonable to expect zero direction changes while drastically changing pitch attitude and making no pilot corrections.

However, what ED did with their math, we have no clue. It did not look like pure non-aerodynamic or aerodynamic. It did not have a dominant one-sided yaw or roll tendency during high AOA level flight. gyroscopic.. Some of them simply yaw/roll into the wrong direction...

[dcn]

2024/1/20 PM4点48分，Insonia说：

"rolling" while pulling. or Is it yawing? and the rolling just side effect by slip stream and vstablizer torque?

I think it's roll.

2024/1/20 PM4点48分，Insonia说：

Angular torque IRL can be caused by on-aerodynamic forces like engine gyroscopic force coupling, GCs and aerodynamic factors like unequal disturbances and anomalies from increased AOA. It is unreasonable to expect zero direction changes while drastically changing pitch attitude and making no pilot corrections.

I don't know whether what you said is right,if so,why third party jets won't roll when pulling the stick.

@BIGNEWY@NineLine

[Insonia]

ED allows the 3rd-party use what they called the EFM (external model) letting dev have the freedom to design their own mathematics.

ED themselves use what they call PFM (professional flight model). probably all share the same mathematical foundations.

im not saying they were correct in this game. 

 

I'm just saying IRL it just basic physics. it will have an effect on aircraft flight characteristics, only matter how much. 

Coupling Dynamics in Aircraft: A Historical Perspective PDF Download | FlipHTML5

Spoiler

the early jets were the ones take the hit the most. like F-100, have strong yaw and roll tendency when pull out due to it's massive spinning inertia. and the swept wing only exacerbates the phenomenon when slipstream and uneven airflow separation are introduced. the aircraft design learn to damping and reducing those force in this hard way. many life lost due to this.

 

 

Edited January 22 by Insonia

[BIGNEWY]

On 1/19/2024 at 2:59 PM, dcn said:

All ED jets can't loop in vertical plane perfectly when the only input is pulling the stick,they will roll,while third party jets can(I tested AV-8B,AJS-37,C-101,F-14B,JF-17,MiG-21bis).To eliminate rolling I tested them with keyboard 'down' to provide a constant amount of stick pull,and there is no wind,no turbulence and I found it's not due to fuel.Is it bug?

 

F-86F.trk 356.76 kB · 4 downloads MiG-15bis.trk 281.22 kB · 4 downloads F-5E.trk 208.5 kB · 4 downloads FA-18C.trk 252.71 kB · 4 downloads F-16C.trk 286.59 kB · 4 downloads F-15C.trk 209.98 kB · 4 downloads A-10C II.trk 236.3 kB · 4 downloads L-39C.trk 223.39 kB · 4 downloads AV-8B.trk 193.02 kB · 5 downloads

 

Hi, 

all seems normal and correct here, it maybe worth checking your device calibration 

test done in viper, no roll in loop

 

loop.trk

[Insonia]

11 hours ago, BIGNEWY said:

Hi, 

all seems normal and correct here, it maybe worth checking your device calibration 

test done in viper, no roll in loop

 

loop.trk 95.28 kB · 1 download

CHEATING

Quote

To eliminate rolling. tested them with keyboard 'down' to provide a constant amount of stick pull.

You have the right roll input.

despite this minor right roll input. Your F-16 also rocks to the left. just like people have already tested. always to the left, always.

 

←↑

So what is this coupling effect? Is this has something to do with engine gyroscopic precession?

Edited January 22 by Insonia

[dcn]

21小时前，Insonia说：

ED allows the 3rd-party use what they called the EFM (external model) letting dev have the freedom to design their own mathematics.

ED themselves use what they call PFM (professional flight model). probably all share the same mathematical foundations.

If only one third party's jet don't roll when pulling the stick,maybe he didn't do it right,but it happens to all third parties.

20小时前，BIGNEWY说：

all seems normal and correct here, it maybe worth checking your device calibration 

test done in viper, no roll in loop

No,you roll.You can see bank angle clearly in F2 view status bar.

21小时前，BIGNEWY说：

it maybe worth checking your device calibration 

I said I tested them by keyboard,so it's not due to my device.

[dcn]

I found F-86F rolls when pulling the stick when bombing with LABS,then I found that all ED jets roll when pulling the stick while third party jets don't roll when pulling the stick,so I posted this topic.

2024/1/22 PM2点20分，Insonia说：

Is this has something to do with engine gyroscopic precession?

Never heard jet aircraft has gyrocopic precesstion before.

 

 

Edited February 1 by dcn

[Insonia]

I already cited this in my previous posts.The book about The coupling effect in aircraft.I mentioned at the beginning that some yaw to the wrong direction if it was the gyro effect alone.  We still just don't know what's happening within the game. And probably they don't want to answer...

Many coupling forces could be reduced and damped significantly in a well designed aircraft, lower spin mass , better aerodynamic stabilizer and control system. It's no longer a safety hazard. No longer impact the performance. But this is basic physics. it still there. It is measurable.

Unrelated documents probably have no intention to cover this topic. 

I found  few articles about earlier F-100 development you may want to look. We will have  F-100 in the future, and I'm looking into it.

 

Gyroscopic effect interacts with other coupling effect and lacks aerodynamic stability at low speed. can trap pilot into a hazard known as "saber dance"

https://aviation.stackexchange.com/questions/31614/do-gyroscopic-forces-from-rotating-engines-significantly-affect-yaw-or-pitch

 

Edited February 1 by Insonia

[dcn]

2小时前，dcn说：

Never heard jet aircraft has gyrocopic precesstion before.

I mean never heard jet aircraft has gyrocopic precesstion caused by jet engine before.

1小时前，Insonia说：

https://aviation.stackexchange.com/questions/31614/do-gyroscopic-forces-from-rotating-engines-significantly-affect-yaw-or-pitch

I have read this 10 days ago but I still doubt it.

1小时前，Insonia说：

We still just don't know what's happening within the game. And probably they don't want to answer...

Yup,I think so.

1小时前，Insonia说：

Gyroscopic effect interacts with other coupling effect and lacks aerodynamic stability at low speed. can trap pilot into a hazard known as "saber dance"

The sabre dance has nothing to do with inertia coupling.

From Wikipedia:'Another control problem suffered by the type stemmed from the handling characteristics of the swept wing at high angles of attack; as the aircraft approached stall speeds, loss of lift on the tips of the wings caused a violent pitch-up. This particular phenomenon (which could easily be fatal at low altitude with insufficient time to recover) became known as the "Sabre dance".'

1小时前，Insonia说：

Unrelated documents probably have no intention to cover this topic. 

The first picture is from Airplane Flying Handbook FAA-H-8083-3C.

[Insonia]

Inertia coupling goes along the inertia axis with smaller radius, thus making it spin super violently.  F-100s inertia couple problem mostly happens at high speed and high attitude. Not takeoff and landing. its has nothing to do with it. Starting a rapid roll movement along with the "inertia axes" and "aerodynamic axes". the roll produces a rapid change in AOA. When the roll velocity surpasses the critical level. Aerodynamic forces can no longer hold it. It tends to roll along other axis.

Another is torque-induced gyroscopic precession, only occurs when the aircraft pitches (lateral axis) or yaws (vertical axis) not roll, motion against the inertia axes. which causes the nose to slightly pitch diagonally. 

the swept wing is more sensitive to the angle of attack and angle of slip.  Adverse yaw might be the dominant force tilting the aircraft in that accident. However, oscillating the nose will oscillate the Δβ can only deteriorate the situation.

Btw , if you oscillate the nose up and DOWN in DCS ED modules. it rocks the nose diagonally, which raises my suspicion. But who knows, maybe their jet PFM API also share the same math with their warbirds..

Edited February 1 by Insonia

[dcn]

5小时前，Insonia说：

Another is torque-induced gyroscopic precession, only occurs when the aircraft pitches (lateral axis) or yaws (vertical axis) not roll, motion against the inertia axes. which causes the nose to slightly pitch diagonally. 

the swept wing is more sensitive to the angle of attack and angle of slip.  Adverse yaw might be the dominant force tilting the aircraft in that accident. However, oscillating the nose will oscillate the Δβ can only deteriorate the situation.

I doubt it.I don't believe jet aircraft has gyrocopic precesstion caused by jet engine.

5小时前，Insonia说：

Btw , if you oscillate the nose up and DOWN in DCS ED modules. it rocks the nose diagonally, which raises my suspicion. But who knows, maybe their jet PFM API also share the same math with their warbirds..

I looked into all ED jets a few days ago and found the direction the aircraft rolls seems to be related to the direction of engine rotation.For example,the J47 engine of F-86F rotates counterclockwise when look from front and F-86F rolls right when pulling the stick.The VK-1 engine of MiG-15bis rolls clockwise when look from front and MiG-15bis rolls left when pulling the stick.So jet aircraft really has gyroscopic precession caused by jet engine?

Edited February 1 by dcn

[Hiob]

2 minutes ago, dcn said:

So jet aircraft really has gyroscopic precession caused by gyrocopic precesstion?

Why should they be exempted from it? It's physics - not a choice. The rotating mass isn't THAT big, but it rotates fast. Question is, if it is modelled and therefore the root cause for you're observation. That I don't know od course.

[dcn]

LOL you replied too quickly and I didn’t have time to change it.

21分钟前，dcn说：

So jet aircraft really has gyroscopic precession caused by gyrocopic precesstion?

So jet aircraft really has gyroscopic precession caused by jet engine?

16分钟前，Hiob说：

Why should they be exempted from it? It's physics - not a choice. The rotating mass isn't THAT big, but it rotates fast. Question is, if it is modelled and therefore the root cause for you're observation. That I don't know od course.

Yeah I heard someone say there is but its impact seems to be small,I doubt it would cause roll when pulling the stick.

Edited February 1 by dcn

[Hiob]

19 minutes ago, dcn said:

LOL you replied too quickly and I didn’t have time to change it.

So jet aircraft really has gyroscopic precession caused by jet engine?

Yeah I heard someone say there is but its impact seems to be small,I doubt it would cause roll when pulling the stick.

 

It is not a matter of "if" but a matter of how big the effect is. Compared to the rotor of a helicopter, the rotating mass is of course very concentrated and probably a lot smaller. It is probably negligible for practical purposes (meaning that a pilot would compensate without even thinking about it - like he wouldn't for crosswind e.g.). But what you did, pulling exactly straight back (by use of artificial input possibilities) may show the small effects - IF they are modelled - which I don't know.

[dcn]

16小时前，Hiob说：

It is not a matter of "if" but a matter of how big the effect is. Compared to the rotor of a helicopter, the rotating mass is of course very concentrated and probably a lot smaller. It is probably negligible for practical purposes (meaning that a pilot would compensate without even thinking about it - like he wouldn't for crosswind e.g.). 

If jet aircraft really has gyroscopic precession caused by jet engine,I think there should be torque reaction too,but it seems to be imperceptible.That is to say, this cannot be manifested at all.

16小时前，Hiob说：

But what you did, pulling exactly straight back (by use of artificial input possibilities) may show the small effects - IF they are modelled - which I don't know.

I tested AI F-86F and found it still rolls when pulling the stick.And I found F-86F rolls when pulling +G even without any input.

F-86 AI.trk F-86 no input.trk

[Art-J]

This reminds me of my uni thesis supervisor, who recalled memoirs of one of Polish aircraft designers observing test pilot performing perfect loops with his MiG-15 or 17 (or more likely their licensed Lim derivatives) and asking the pilot afterwards about how did the aircraft not break the vertical plane of the maneuver because of precession of the engine. To which the pilot replied that it did want to do it, be he was counteracting accordingly with correct control inputs all the time.

Granted, it's just a memo, but the fact is every spinning thing subjected to Newtonian physics is affected by precession, it's only the question of how strong the effect is and how/if it's balanced by external factors.