Jump to content

Course in Route mode.


Tarres

Recommended Posts

First and foremost, maybe it´s WiP.

Second, maybe it´s user problem.

With a desired course dialed and the Route mode set to on, there is a discrepancy between the course dialed and the course that the HSi shows.

Attanched trk with an example using the free flight mission over the Caucasus, so the HSI is correctly set with the MAGVAR and the operation mode is set to GYRO in the Greben-1 that is the operational mode. So, in theory no differences between the HSI and the external view bar information.

Maybe the HDG mode in the Greben-1 is involved in the Route mode operation?

Thanks.

MIke.

P.S. Any chance to have an updated manual? It seems that the 24P is following the path of the Mi-8 manual.

 

Route mode HDG off.trk

Link to comment
Share on other sites

  • ED Team

Hi, 

thanks for the report and chat in discord. 

The team have let me know there is still some w.i.p and final checks to be made here. 

The mode works with the DISS-15 and the discrepancy in heading maybe due to slip correction being taken into account. 

thanks

 

smallCATPILOT.PNG.04bbece1b27ff1b2c193b174ec410fc0.PNG

Forum rules - DCS Crashing? Try this first - Cleanup and Repair - Discord BIGNEWY#8703 - Youtube - Patch Status

Windows 11, NVIDIA MSI RTX 3090, Intel® i9-10900K 3.70GHz, 5.30GHz Turbo, Corsair Hydro Series H150i Pro, 64GB DDR @3200, ASUS ROG Strix Z490-F Gaming, HP Reverb G2

Link to comment
Share on other sites

8 hours ago, Tarres said:

Thanks. No problem.

I supposed that was WiP.

 

1. GYRO mode in the Greben currently has some drift. And this is correct, about 2-3 degrees per hour IIRC, and drifts a bit faster in DCS. In reality this is becuase GYRO is used as a back up mode at latitudes above 80 degrees, where magnetic variation may change so much throughout the flight that it’s more helpful to disconnect the gyro compass from the magnetic flux detector and just use its gyro scoooc stabilization. Solution, use MAG mode. Currently in DCS there is no drift in MAG mode. IIRC in real life it is about 1 degree per hour, but it is constantly performing a slow along at about 3-4 degrees per minute using the magnetic flux detector to find magnetic direction and reduce error in the compass over time. Thus MAG mode is the primary operating mode of the Greben when under 80 degrees of latitude. 
 

I understand that in DCS, for air start (I haven’t checked hot start) that ED has made is so that default mode is GYRO, when it should be MAG. This doing an air start and not touching anything you will see more drift then if you had done a cold start and left it in MAG mode. 

9 hours ago, BIGNEWY said:

Hi, 

thanks for the report and chat in discord. 

The team have let me know there is still some w.i.p and final checks to be made here. 

The mode works with the DISS-15 and the discrepancy in heading maybe due to slip correction being taken into account. 

thanks

 

  BN, on that note I would say that if this is caused by drift in GYRO mode perhaps the “fix” might just be changing default switch position in air/hot start from GYRO mode to MAG mode. I have a hunch that the reason the GYRO mode is default in air/hot start is becuase in Mi-8, it’s gyro compass unit that is counterpart you the Greben uses GYRO as it’s main operating mode, and uses MAG mode for alignment during start up. Which would mean it would be at MAG for cold start but GYRO for air/hot start. The team can reference any Mi-24 start up procedure in a real manual and they always say to make sure the Greben is left in MAG mode. 
 

2. as BN said. The route mode corrects for lateral drift caused by wind. You can see this by looking at the drift meter on the dashboard that also shows doppler ground speed. If it shows 4 degrees of peft drift for example, your heading will be 4 degrees to the right of the assigned heading when the route mode is working perfectly. if there is a difference between drift degrees and HSU difference from route Heading selector, something else is going on

 

3. Can’t view your track right now and I’m sure it would be hard to tell with it anyways, and not sure how well you know the route mode, but it has some pretty hefty limits. It will roll you only 15 degrees to try and get you on the desired course. And the autopilot itself only has 18% authority. Becuase of these things, it is very easily to be slightly out of trim and have the roll channel not have the authority to get you along the specified course in route mode. The way to check this is by looking at the roll channel servo displacement window by your left knee, or by looking at its representation in the R control + enter menu on the top right that shows the AP servo displacement windows for all channels. The roll channel is the second window from the left, if it shows ANY MOVEMENT AT ALL from center, it senses that you are on the wrong course and is trying to turn you down on course. So if you see some movement in the roll channel from center but the Mi-24 itself isn’t turning, you may have to “help” it with either manual left/right cyclic, with the trim hat, or by trimming again. 
 

So currently in DCS, if Route mode button light is on, if Greben is in MAG mode, drift gauge shows degrees of drift that is equal to Heading difference from route mode selected Heading, and roll channel is perfectly nuetral, you will be exactly along the desired course. 
 

I apologize if you already know most of this, but the route mode only effects the roll channel and completely takes it over, which isn’t well understood without a full manual at the moment. As an aside, even when leaving route mode by exceeding doppler angle limits of 30 degrees bank or 7 degrees pitch or 3,000m AGL, you the last commander input often gets stuck and added to regular autopilot commands, and you will need to press the OFF button for the Hover/Route modes to get the AP back to the way it should be when not using those Hover/Route functions. 

Black Shark Den Squadron Member: We are open to new recruits, click here to check us out or apply to join! https://blacksharkden.com

E3FFFC01-584A-411C-8AFB-B02A23157EB6.jpeg

Link to comment
Share on other sites

36 minutes ago, Tarres said:

Yes, it´s a constant 10º deviation.

On a side note, in the Greben (1 and 2) the normal operation position is the Gyro position, confirmed with KA-32 firefighter's pilots.

 

  Maybe for them, but I’ve read numerous Mi-24 manuals for variants D/V/P, and Mi-35M which has same system. And in those it is said to be MAG mode according to all take off procedures and all mentions of the Greben system including technical documents. Only mention of using it in a mode other then MAG is in Mi-35M start up procedure. Mi-35M manual itself is much more detailed then any of the other Mi-24 manuals. But it says “ the mode DG should be used at flights in high northern or southern latitudes or over magnetic anomaly zones.”  Or in other words, areas where the magnetic correction in MAG mode may cause greater errors then disconnecting the magnetic correction and relying only on gyro correction. I’m pretty sure I’ve heard that fires can cause magnetic anomalies, and if they are say operating in Canada at high latitudes, it would make sense why firefighters might prefer GYRO/DG mode, as it’s perfectly useable with only about a 2 degree error per hour. 
 

  Just repeating what I’ve read in every Mi-24 operation/technical manual I have. And in DCS you can test yourself that MAG mode will have no error/drift over time but GYRO mode will be a steady 4-5 degrees per hour, which may be too much itself but I am not very concerned.  
 

   A constant 10 degree deviation is odd unless you were staying along a soecific course with enough wind in the right direction to cause 10 degrees of lateral drift for the route mode to correct. 

Black Shark Den Squadron Member: We are open to new recruits, click here to check us out or apply to join! https://blacksharkden.com

E3FFFC01-584A-411C-8AFB-B02A23157EB6.jpeg

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...