Question AutoFCS

[PriestLizard]

Hi there.

I have some questions related with AutoFCS. Hopefully you guys can help me out.

The issue is the following: I have installed the ISS Addon (International Space Station V.3) by following the installation instructions step-by-step. I used a clean Orbiter folder for this installation (the only pre-installed add-on was Orbiter Sound 3.5).

Now while everything works fine, the AutoFCS Addon wont work correctly. After starting the Addon, KSC Runway 33 is already set - so I wait untill automatic deorbit burn. After the burn, I press "SEL" on the post-burn part of AutoFCS (which puts the Orbiter into the correct orientation for EI).

The result is always the same: I end up somewhere in south america or the pacific. FYI: I used a slight time acceleration of 3.0x. (Haven't tested it with 1x yet). I did read somewhere though, that AutoFCS should work untill a warp of 10.0x.
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I have tried to solve this problem by following the steps described in the OrbiterWiki article about AutoFCS - but it made things just worse: The shuttle rushed downwards with -500m/s VS and it ultimately crashed down in the pacific ocean.

Once I did actually land at Cape Canaveral, but beside the runway. This seems to be the well-known issue about the KSC Hi-Res addon. But when I checked the locations in the CFG file, everything seems right.

Is there someone out there who is actually an expert with AutoFCS? My main questions are:

1. What is the difference between AutoFCS and AutoFCS2? How do I know which version I have and how do I know, if I have the updated version from the shuttle fleet author?

2. AutoFCS is supposed to de-orbit when the predictive orbit passes over the selected landing site. However, this does not seem to happen if I press "SEL" in the pre-burn part of FCS too early. Then AutoFCS deorbit immediatly.

3. Is there a website or something about AutoFCS? Actually I cant find a download anyway - its only included in the shuttle fleet addon.

Thanks in advance for your help. See you later.

 

[Donamy]

I would try selecting the the burn just before passing India.

 

[PriestLizard]

So the user is still in charge to do the de-orbit burn? And by "selecting" - you are probably talking about the SEL button in the pre-burn part?

However, how does this influence the actual landing location of the shuttle? Yesterday I tried it again... my orbit passed right over Edwards AFB so I chose EDW in the AutoFCS menu. Then everything went quite OK - however, the shuttle was not landing on the runway but rather "somewhere" on the texture tile.

Is this a limitation of the Add-On?

 

[David413]

Hi there.

I have some questions related with AutoFCS. Hopefully you guys can help me out.

The issue is the following: I have installed the ISS Addon (International Space Station V.3) by following the installation instructions step-by-step. I used a clean Orbiter folder for this installation (the only pre-installed add-on was Orbiter Sound 3.5).

Now while everything works fine, the AutoFCS Addon wont work correctly. After starting the Addon, KSC Runway 33 is already set - so I wait untill automatic deorbit burn. After the burn, I press "SEL" on the post-burn part of AutoFCS (which puts the Orbiter into the correct orientation for EI).

Okay, let's start here. Attached to my reply is a zip file that includes a testing scenario for the AutoFCS. Open the scenario in Orbiter, then select the AutoFCS, and using the UPPER sel switch, select so that the program will perform the deorbit burn at the proper time.

The result is always the same: I end up somewhere in south america or the pacific. FYI: I used a slight time acceleration of 3.0x. (Haven't tested it with 1x yet). I did read somewhere though, that AutoFCS should work untill a warp of 10.0x.

I'm not sure how you get a time acceleration of 3.0x, but I use 10x until entry interface, then downmode to 1.0x and allow the entry to fly in real-time. The AutoFCS is very computational intensive, and if your computer is trying to do too much, it's performance will suffer.

Once I did actually land at Cape Canaveral, but beside the runway. This seems to be the well-known issue about the KSC Hi-Res addon. But when I checked the locations in the CFG file, everything seems right.

They're not. Include in the zip file is an updated Earth.cfg file which will help. You may still land slightly off centerline, but you should land on the runway. BTW, in real life there is no autolanding of the shuttle, the commander takes over before flying the HAC. I always do this too, and I land the shuttle by hand.

Is there someone out there who is actually an expert with AutoFCS? My main questions are:

1. What is the difference between AutoFCS and AutoFCS2? How do I know which version I have and how do I know, if I have the updated version from the shuttle fleet author?

As the shuttle fleet author, I can tell you that I had nothing to do with the AutoFCS, it was created by Mikey451 (Mike Norman). The AutoFCS2 was an updated attempt to work better in Orbiter 2006, but I include the version that works best with the shuttle fleet. I recommend using the version I included with the fleet.

2. AutoFCS is supposed to de-orbit when the predictive orbit passes over the selected landing site. However, this does not seem to happen if I press "SEL" in the pre-burn part of FCS too early. Then AutoFCS deorbit immediatly.

It's best to wait until you're over Asia to activate the AutoFCS to avoid this problem.

I have tested the include scenario file and I had no problem with either the deorbit, entry or landing. I have also included an updated LandingSite table for the GPCMFD that works with the hi-Res KSC add-on. Just unzip this package into your Orbiter directory with folders preserved and then try the AutoFCS testing scenario. You can start the AutoFCS right after starting the scenario and select the deorbit burn (upper) selection button. Time accel at 10x until after the burn when you reach around 80 km altitude, but no later than the first roll of the shuttle.

Good luck, let me know if this helps...

Dave

 

[PriestLizard]

Thanks David for your detailed reply. I used your .ZIP file and tried your scenario - everything worked fine. I just want to make things clear - so I know I understand the procedure:

1. AutoFCS will _not_ perform the correct de-orbit burn by itself. The user has to align planes accordingly (or wait untill the orbit passes approx. over the landing site). Then by pressing the SEL button in the upper part (pre-burn), AutoFCS will control the shuttle attitude and perform the burn at the selected distance from the landing site (by default 8.06Mm).

2. After the burn, while the shuttle is coasting to the EI, the user has to press SEL in the lower part of AutoFCS (post-burn). AutoFCS will then control the attitude of the shuttle for EI (by default AOA 40°, bank 0°).

3. Following this procedure, AutoFCS will land the shuttle approx. on the runway. If I want to follow real-world landing, how/when do I disable AutoFCS?

Thanks again for your help.
see you!

 

[David413]

1. AutoFCS will _not_ perform the correct de-orbit burn by itself. The user has to align planes accordingly (or wait untill the orbit passes approx. over the landing site). Then by pressing the SEL button in the upper part (pre-burn), AutoFCS will control the shuttle attitude and perform the burn at the selected distance from the landing site (by default 8.06Mm).

I'm not exactly sure what you mean here; but, yes, you need to wait until the orbit is aligned with the landing site and you are about a half the world away from the landing site to engage the autofcs.

2. After the burn, while the shuttle is coasting to the EI, the user has to press SEL in the lower part of AutoFCS (post-burn). AutoFCS will then control the attitude of the shuttle for EI (by default AOA 40°, bank 0°).

Incorrect; if you have already activated the autofcs and it performed the deorbit burn, there is no need to select the lower sel switch, it should fly the entire entry and landing.

3. Following this procedure, AutoFCS will land the shuttle approx. on the runway. If I want to follow real-world landing, how/when do I disable AutoFCS?

You should disable the autofcs (using the "u" key) just prior to HAC intercept. Use the GPCMFD, OPS 4 Spec 50 screen to fly the HAC and land. That's pretty close to the real world.

To anyone else downloading and installing the attached zip file: The changes associated with this file are for the specific installation that is described here, namely the required installation for the ISS V3.0 ONLY! If you have a different installation, you should not use this file, I only provided it for the specific question asked here about this particular installation!

 

[PriestLizard]

Ok thx for pointing things out.

However, I'm pretty sure that one has to push the lower SEL button as well. If I don't push it, the shuttle continues to pitch up >> 40° even when at EI. But maybe I should have waited some more untill AutoFCS pitches down again to 40°.

See you~

 

[David413]

Ok thx for pointing things out.

However, I'm pretty sure that one has to push the lower SEL button as well. If I don't push it, the shuttle continues to pitch up >> 40° even when at EI. But maybe I should have waited some more untill AutoFCS pitches down again to 40°.

See you~

Having flown hundreds of entries, I can tell you that I have never had to push the lower select. The system will control the AOA as necessary following EI. Try it...

Dave

 

[Donamy]

Having flown hundreds of entries, I can tell you that I have never had to push the lower select. The system will control the AOA as necessary following EI. Try it...

Dave

My experience also !!