How to fix HSI heading error?

[JetJake76]

Hello,

First, I guess it may not be a bug, just something I didn't find a solution for in the manual.

I have prepared a simple mission to practice attacking vehicles with ATGMs. First, I took off from Tonopah on Nevada map. Attack on targets involved many sharp 90-deg turns and when I finally returned to the base, I noticed a huge difference between HSI heading and standby compass (the one over the gunsight). HSI indicated about 330 while the standby compass indicated 270 which was correct. The heading on the Petrovich interface was also about 270. The marker on the moving map followed north-west heading, I guess it used value from HSI. 

All navigation devices were operating, and configured on startup and there was no wind in this mission. Is there a way to realign the HSI in-flight?

[tae.]

You must press and hold the SYNCH button to the left of the collective, while the "GYRO" switch is in the "MAG" position:



However I found that I kept having to do it during flight every 10-20 minutes or so - not sure if this is intended yet or a bug. I think the switch needs to be set back to the middle GYRO position after alignment but I didn't fly this patch enough to test yet.

Anyone with more knowledge that can give some input would be appreciated.

 

Edited May 2, 2022 by tae.

[AeriaGloria]

1 hour ago, tae. said:

You must press and hold the SYNCH button to the left of the collective, while the "GYRO" switch is in the "MAG" position:



However I found that I kept having to do it during flight every 10-20 minutes or so - not sure if this is intended yet or a bug. I think the switch needs to be set back to the middle GYRO position after alignment but I didn't fly this patch enough to test yet.

Anyone with more knowledge that can give some input would be appreciated.

 

 

That’s what I did. Pressed match in MAG mode. Switched to sync. The gyro drift reduces a lot in that mode. At the end of the flight I might switch to MAG, and press Match. And HSI would only correct a few degrees Whereas if I did the same thing at the end of a flight with Greben in only Mag mode the whole time after pressing Match on takeoff, pressing match again at the end of the flight could correct the HSI tens of degrees 

[randomTOTEN]

Seems like there's some sort of delay after Petrovich reports setting MAGVAR before the gyros will sync.

[AeriaGloria]

9 minutes ago, randomTOTEN said:

Seems like there's some sort of delay after Petrovich reports setting MAGVAR before the gyros will sync.

When does it report that? I haven’t seen this. I must’ve missed it becuase I tried a 30 km trip in Syria the other day and it was perfect 

[Tarres]

According to the Greben-2 operation (KA-32 pilot´s manual), the operational mode is the "Gyro Mode", and the "Mag mode" is used for setting up the system with the KM-2 declination.

Any mission created for the 24P with the helo set in hot condition shows the Greben-1 sets in Gyro mode.

But I´m not sure. The 24P manual hasn´t been updated since release.

 

[Tarres]

@AeriaGloria I´m doing some tests with the route mode and the (route) heading selector. The readings in the Caucasus map between the heading introduced with the heading selector and the HSI seem to have a discrepancy that is the MagVar. 

If you enter a desired course of 352º, the HSI after the turn has a reading of 0º.

What do you think? Maybe related with the Greben?

I think that the Greben is WiP.

[AeriaGloria]

1 hour ago, Tarres said:

@AeriaGloria I´m doing some tests with the route mode and the (route) heading selector. The readings in the Caucasus map between the heading introduced with the heading selector and the HSI seem to have a discrepancy that is the MagVar. 

If you enter a desired course of 352º, the HSI after the turn has a reading of 0º.

What do you think? Maybe related with the Greben?

I think that the Greben is WiP.

That just sounds weird. Before or after last patch HSI and route mode should always agree, they are using same directional gyro. 

Are you sure the route mode was done turning you? It has very low authority, it will not turn you past 15 degrees of bank, and only has 18% control authority to start with. It is very easy if not perfectly trimmed to be off heading. If your autopilot panel or Rcontrol + enter menu shows roll channel of autopilot still deflecting left while at 0 degree heading with route mode selected at 352 ( and route mode is on), that’s what’s happening. The route mode is trying to turn you, but it doesn’t have the authority in your current trim state.

 

Also, make sure route mode is on as it’s easy to turn off in the turn as it can only be used while doppler works at +/-7 degrees pitch and +/-30 degrees roll. It easy when it turns you, to pitch down les then  7 degrees. And if you exceed about 260 kmh, you usually need more then -7 degrees pitch to maintain level flight and can no longer use route. 

Also depends on the winds In the mission, the route mode is special in that it corrects for wind using doppler drift. If route mode wasn’t commanding any turn at 0 degrees, it’s possible there was 8 degrees of left drift, and it was stil making your ground track/heading go along 352

I apologize if this is all old news to you 

[Tarres]

Thanks.

It´s what I was thinking. I´ll make some more tests.