Altitude hold

[Nooch]

So in the commands window, in the SAU subsection, there is a command called "Altitude Hold". Problem is there is no altitude hold in the Mig 21, appart from the Recovery mode. I've searched the manual but can't find anything on the subject.

To see if this "altitude hold" mode works, I've assigned it to a key on my keyboard and engaged it and it doesn't seem to do much...

No big deal but I just find it very weird that it's there. Any thoughts on this?

Edited May 6, 2015 by Nooch

[j.sabo12]

I'm not sure if there are two separate systems, but the recovery mode, once it recovers from an unusual attitude holds the altitude at which it was when the system was activated.

 

I would also be interested in a more thorough answer though.

[Buzzles]

You're on about the command that's bound to "J" by default?

 

[Removed due to derp]

 

It's attitude, not altitude.

Edited May 6, 2015 by Buzzles

[Blech]

Hi,

 

I guess he means SAU - Hold Attitude (current bank/pitch)

Default key "J"

 

Button LV53 STABILIZATION - SAU mode -> ON !!!

Manual page 64

 

Then you can use SAU - Hold Attitude e.g. for flying a circle or long climbings

 

Hold the stick in the desired position

"J" works on/off

If on - you can move the stick around without any reaction

 

But there is no button/switch (?) or click noise for this function - strange

[Nooch]

Yep I meant "SAU - Hold Attitude". And indeed it's not altitude sorry :poster_oops:

 

 

Hi,

 

I guess he means SAU - Hold Attitude (current bank/pitch)

Default key "J"

 

Button LV53 STABILIZATION - SAU mode -> ON !!!

Manual page 64

 

Then you can use SAU - Hold Attitude e.g. for flying a circle or long climbings

 

Hold the stick in the desired position

"J" works on/off

If on - you can move the stick around without any reaction

 

But there is no button/switch (?) or click noise for this function - strange

 

Thank you for your explanation I now understand how to make this thing work (button light LV53 STABILIZATION - SAU mode must be ON first) :)

Like you, I'm quite surprised there is no corresponding button anywhere in the cockpit...

 

EDIT: I think I got it. Basically pressing J is like taking your hands off of the stick. Because in the manual they say that in order for the SAU to hold attitude and stabilize the aircraft you must have LV53 switch on AND relieve the stick of pressure.

Edited May 6, 2015 by Nooch

[Blech]

Like you, I'm quite surprised there is no corresponding button anywhere in the cockpit...

 

EDIT: I think I got it. Basically pressing J is like taking your hands off of the stick. Because in the manual they say that in order for the SAU to hold attitude and stabilize the aircraft you must have LV53 switch on AND relieve the stick of pressure.

 

:thumbup: Got it too now

[WildBillKelsoe]

so its like Ka-50 trim to attitude? what are the parameters limits in terms of pitch and bank?

[IonicRipper]

Yep I meant "SAU - Hold Attitude". And indeed it's not altitude sorry :poster_oops:

 

I often misread those two as well :lol:

[virgo47]

Does it mean that SAU - Hold Attitude (J by default) is some kind of assist/cheat or combo, and not an actual switch/button in the cockpit?

How exactly does it differ from SAU - Stabilize which is a light-button (LV53 in the manual, if I get it right)?

[Rudel_chw]

38 minutes ago, virgo47 said:

Does it mean that SAU - Hold Attitude (J by default) is some kind of assist/cheat or combo, and not an actual switch/button in the cockpit?

 

It means the J key tells the Simulator that your hands are no longer holding the flight stick.

 

38 minutes ago, virgo47 said:

How exactly does it differ from SAU - Stabilize which is a light-button (LV53 in the manual, if I get it right)?

 

The Stabilize mode is just a way to smooth your flight stick commands to the control surfaces. If you are on this mode, and then put your aircraft in any arbitrary ATTitude, when you release the stick (actually press J, since the Sim has no way to detect if you are applying pressure on the stick or not), the SAU will keep the current ATTitude (as long as your airspeed allows)

 

 

[virgo47]

18 minutes ago, Rudel_chw said:

It means the J key tells the Simulator that your hands are no longer holding the flight stick...

I still don't quite get it... So J works only in stabilization mode, and it somehow keeps the attitude, just like it would if I engaged the stabilization mode without the hand on the stick?

Does it mean I can do the same with pitch trim (the only one available) and then pressing the stabilization mode when the bank angle is what I want without having my hand on my stick at that time? (MiG-21 tends to unroll/unbank, so J helps me to keep the bank, in addition to the trimmed pitch... is that it?)

And just to clarify, J is a simulator trick/assist then, not a real function of MiG-21, right?

[Rudel_chw]

2 minutes ago, virgo47 said:

I still don't quite get it... So J works only in stabilization mode

 

Yes, J only has effect when Stabilization mode is active.

 

2 minutes ago, virgo47 said:

 and it somehow keeps the attitude,

 

yes

 

2 minutes ago, virgo47 said:

just like it would if I engaged the stabilization mode without the hand on the stick?

 

it's not the same, engaging just the Stabilization does not provide ATT hold.  Why don't you simply test this yourself on a short flight?

 

2 minutes ago, virgo47 said:

And just to clarify, J is a simulator trick/assist then, not a real function of MiG-21, right?

 

On the real MiG-21 the function is "release pressure on the stick" ... the simulator mimics it with the J keystroke.

[virgo47]

18 minutes ago, Rudel_chw said:

it's not the same, engaging just the Stabilization does not provide ATT hold.  Why don't you simply test this yourself on a short flight?

I tried it and it seemed that way, I just wanted to be sure. I'm probably mentally stuck on something here and I can't find the description in manual (at least not with the text search). On page 64 it says:

Quote

The Autopilot stabilization button-light (LV53) activates the “STABILIZATION” SAU mode, which dampens aircraft vibrations and stabilizes current aircraft position if stick is relieved of forces (using trimmer) and not held. This is done by filtering stick inputs. Additionally, the SAU will try to stabilize your heading and pitch (if your bank is small, lesser than ~10o) or your bank and pitch (if your current bank is > ~10o).

Yet, if I trim the plane and bank it over 10 deg (e.g. 30 deg) and then just engage STABILIZE without holding my stick it does not stabilize the bank. That's what is confusing to me. To get what the manual says, I have to STABILIZE and then simulate not holding the stick with J although I didn't hold the stick at all in the first place.

EDIT: I can speculate that the difference in roll axis is that J simulates the stick deflected and relieved of the pressure. It's difficult to imagine with a home setup with spingy joystick I guess. I can see J doing something subtle with the stick in the cockpit, so it's not the same as just leaving the stick in the middle position - which is "no pressure" for me, but perhaps not the same as "no pressure" in the real life cockpit?

Edited January 15 by virgo47

[corn322]

Some of the SAU modes have never worked correctly, or maybe only worked in the past. Like the stabilize mode you are trying to use.

21 hours ago, virgo47 said:

Yet, if I trim the plane and bank it over 10 deg (e.g. 30 deg) and then just engage STABILIZE without holding my stick it does not stabilize the bank.

It should also keep you straight when you have uneven load, like after firing missile from one side of the plane only.

[Rudel_chw]

4 minutes ago, corn322 said:

Some of the SAU modes have never worked correctly, or maybe only worked in the past.

one’s gotta love statements like this, generalities with zero proof .. only serves to have new users avoid the module, when in fact it can be a very entertaining and worthwhile experience, such a pity 

[corn322]

According to the manual, all I have to do is push this button number 53. The stabilization mode will be on, and it will try to stabilize my pitch and bank.

Here in this track of my air start Mig-21, I level out the aircraft, press the button, and the aircraft is not stabilized.

sau test.trk

[Rudel_chw]

7 minutes ago, corn322 said:

I level out the aircraft, press the button, and the aircraft is not stabilized.

 

 

The manual says "The Autopilot stabilization button-light (LV53) activates the “STABILIZATION” SAU mode, which
dampens aircraft vibrations ..."

 

so, the pressing this button alone only gives you a dampened flight stick, this is not the same as the "hold attitude" of other aircraft's AP.

 

the manual goes on to add "and stabilizes current aircraft position if stick is relieved of forces (using
trimmer) and not held."  ... you can relieve the flight stick by pressing J once the LV53 is active ... at this point you will have the Attitude Stabilized (just the attitude, the aircraft may lose altitude if the bank or pitch-up  is too much.

[corn322]

5 minutes ago, Rudel_chw said:

you can relieve the flight stick by pressing J

Wait so this whole time I've had to press a button to let go to the stick? Where in the manual does it specify this? *looks around* It doesn't?

Yes, it works after using the magic button. Thanks for the info.

[virgo47]

8 hours ago, corn322 said:

Wait so this whole time I've had to press a button to let go to the stick? Where in the manual does it specify this? *looks around* It doesn't?

Yes, it works after using the magic button. Thanks for the info.

Where the real manual meets the simulation, many DCS manuals fall a bit short and forget to mention things. I also think this should have been clearly stated somehow, otherwise it is confusing, it requires experiments, and even after those one still can ask "is this really how it should work?"

In overall, the MiG-21bis is quite good actually, but I also couldn't find anything related to this simulation feature.

[portman]

Am 17.1.2025 um 08:56 schrieb virgo47:

... and even after those one still can ask "is this really how it should work?"

It's a bit complicated indeed.

According to the GDR air force docs I have, it worked like this: You have to trim the aircraft before you activate stabilization mode. In our former air force, the pilots activated the stabilization mode on the runway before takeoff. In the air, with stabilization mode engaged, you could let go off the stick, and the AP-155 would stabilize the current attitude. If there was a bank >6° the bank would be stabilized, if the bank was <6° the aircraft would return to 0° bank and then stabilize it. Bank angles from 80° to 100° did not get stabilized. The heading got stabilized within +/- 3° if the pitch was not bigger than +/- 40° (while climbing or descending) and within +/- 1° in horizontal flight.

There were several micro switches under the stick collar which recognized stick inputs by the pilot. So if you put pressure on the stick again (> 1.5 kg), you could kind of "overwrite" the attitude hold and the aircraft did react accordingly.

In DCS, your joystick will jump back to the zero position if you relieve the pressure on it, telling DCS "I'm moving the stick back to zero!" Therefore, you have to press "J" to tell DCS "I'm just letting go off the stick, without further inputs". The "J" replaces the micro switches in the real aircraft.

Then you can move your joystick around without anything happening, which is basically wrong, because in the real MiG you could overwrite the attitude hold by applying pressure on the stick again...

As I said, it requires a bit of "thinking around the corner", as we say in Germany 

I think, if everyone had a force feedback joystick, this "feature" could be simulated appropriately.

[Rudel_chw]

3 minutes ago, portman said:

According to the GDR air force docs I have, it worked like this:

 

Hi, thanks a lot for clearing that up 

[virgo47]

1 hour ago, portman said:

In the air, with stabilization mode engaged, you could let go off the stick, and the AP-155 would stabilize the current attitude.

Thanks for the info, this now makes more sense. I'm still a bit unsure about this sentence though, sorry for bothering you with one more question.

So in a real plane - with stabilization mode enabled, even with some side pressure on the stick - if I suddenly let it go, it would stabilize? (In various ways depending on other roll/pitch params, of course.) The reason I ask is, I expect there was some backpressure from the stick itself depending on what the plane was doing at the moment.

It is kinda unique and unlike various stabilization modes in newer planes, it's a really interesting system.

[portman]

vor 14 Stunden schrieb virgo47:

So in a real plane - with stabilization mode enabled, even with some side pressure on the stick - if I suddenly let it go, it would stabilize? (In various ways depending on other roll/pitch params, of course.) The reason I ask is, I expect there was some backpressure from the stick itself depending on what the plane was doing at the moment.

It is kinda unique and unlike various stabilization modes in newer planes, it's a really interesting system.

Interpreting the old docs - I think so. I have never flown a real MiG, but I will ask somebody who has!

I also have to correct one point I mentioned: The force required to actuate the micro switches and thus to overwrite the attitude hold mode was 1,7 - 1,9 kp in the longitudinal axis and 1,0 - 1,2 kp in the lateral axis. This also worked in the recovery mode, i.e. you have to let go off the stick after pressing the button for the recovery mode to work.