EAC and coordinated turns

[kontiuka]

I read in the manual that the SAS helps keep coordinated turns, ie. no slipping or skidding. However, when I have SAS off, my turns already seem coordinated. Even more so than when SAS is on. Anyone notice this?

 

EDIT: Title should read SAS, not EAC.

Edited January 18, 2014 by kontiuka

[Nealius]

I thought the ARI dealt with coordinated turns?

[kontiuka]

what is ARI?

[Nealius]

I'm too lazy to look through the real manual and Google is being a butthole by searching for "air" instead of "ARI", but best I can remember the ARI is some automatic device linked to the rudder.

[Yurgon]

I read in the manual that the EAC helps keep coordinated turns, ie. no slipping or skidding. However, when I have EAC off, my turns already seem coordinated. Even more so than when EAC is on. Anyone notice this?

 

I never noticed this. But I only fly without EAC when it's shot to pieces, and then I have other things to worry about than coordinated turns. :D

 

The only mention of turn coordination I could find in the Flight Control System chapter of the manual refers to SAS (Stability Augmentation System) rather than EAC.

 

I'm too lazy to look through the real manual and Google is being a butthole by searching for "air" instead of "ARI", but best I can remember the ARI is some automatic device linked to the rudder.

 

In the first half of the manual, I found stuff like "various", "variety", "primary" and "bearing". "Ari" is also a German shortcut for "Artillerie" ("Artillery"). I don't think any of these have to do with coordinated turns... :D

 

I think the manual answers OPs question best (point of interest marked red).

 

Flight Control Systems (FCS)

 

The primary elements of the A-10C Flight Control Systems (FCS) of the A-10 include the Stability Augmentation System (SAS), the Manual Reversion Flight Control System (MRFCS), and the Enhanced Attitude Control System (EAC). In combination and according to the situation, the FCS determines how the pilot’s control inputs are transferred to the aircraft.

 

Stability Augmentation System (SAS)

 

The SAS improves the handling qualities of the A-10 and allows better and finer control. This results in better target tracking and reduces the amount of trimming needed.

 

SAS consists of control inputs in two channels: the pitch axis and the yaw axis. Note that SAS does not affect roll. As you might imagine, the pitch channel acts on elevator control input and the yaw channel acts on rudder input.

 

Pitch SAS

The SAS pitch channels allows the Integrated Flight and Fire Control Computer (IFFCC) to provide pitch control functions up to +5/-2 elevator trailing edge. The most noticeable effect of this is pipper tracking on a target through the HUD in the pitch axis.

 

Yaw SAS

The SAS yaw channels have three main functions:

• ± 7-degrees of yaw rate dampening
  
• ± 7-degrees of rudder authority for turn coordination
  
• ± 10-degrees of rudder authority for yaw trim
  

 

The SAS continuously compares the output of the two channels, and if there is an excessive difference, the system will automatically deactivate both channels of the axis.

 

SAS can also be disconnected with the SAS disconnect button.

 

For SAS operation, hydraulic power must be provided.

 

[snip: Manual Reversion Flight Control System (MRFCS)]

 

Enhanced Attitude Control System (EAC)

 

The EAC system was one part of the LASTE update to the A-10A that provides an autopilot capability. EAC uses sensor data from the Embedded GPS INS (EGI) navigation system, the Central Air Data Computer (CADC) and the SAS, and then provides input into elevator and yaw as part of the SAS.

 

The EAC system provides two major FCS functions:

 

Precision Attitude Control (PAC). In PAC 1, pressing the trigger in Gun master mode will trim the aircraft through SAS to keep the gun pipper on the target point.

 

Low Altitude Autopilot (LAAP). This includes the autopilot modes of Altitude/Bank Hold, Altitude/Heading Hold, and Path Hold modes.

 

Combined, the FCS of the A-10C provides a good, stable weapons platform to accurately employ weapons from. However, unlike an F-16 for example, its FCS is not a fly-by-wire system and the pilot is much more in charge of what the aircraft is doing rather than being a voting member. As such, the A-10 is very much a seat-of-your-pants aircraft to fly and can be extremely responsive in the right hands.

[kontiuka]

Oh, maybe I meant SAS. Anyways, I disabled yaw and pitch SAS as well and my turns were still perfectly coordinated. I don't have easy flight mode set or anything like that.

[Nealius]

Ok, found some references for the ARI. -1 page 6-1:

 

"...a full-time ARI provides turn coordination as long as the yaw SAS is engaged"

 

And page 6-4:

 

"An ARI incorporated into SAS system reduces adverse yaw effect during roll maneuvers."

 

And finally found the definition: Aileron Rudder Interconnect.

 

What's interesting is that this is only in the A-10A -1. I can't find any mention of the ARI in the A-10C -1.

[kontiuka]

The thing is that my SAS is turned off. That's what confounds me.:)

[camsr]

I never noticed this. But I only fly without EAC when it's shot to pieces, and then I have other things to worry about than coordinated turns. :D

 

That's like the most important part of flying a plane though...

Drag your tail too much and you'll fall right out the sky.

Although the A10 is fairly noob-friendly in this regard, I find it's rudder control to be cumbersome, and it doesn't help I use a keyboard either.

[Doughboy]

From what I remember (IRL) skidding in turns (uncoordinated) is more pronounced at slower speeds. So if you're smashing around at 270IAS you may not notice the ball being out of line. However, if you are turning at 150IAS and put it into a turn the ball may slide a little further out. Having turns coordinated is also going to be more of an issue at these low speeds as getting it too far out can result in a spin.

[kontiuka]

From what I remember (IRL) skidding in turns (uncoordinated) is more pronounced at slower speeds. So if you're smashing around at 270IAS you may not notice the ball being out of line. However, if you are turning at 150IAS and put it into a turn the ball may slide a little further out. Having turns coordinated is also going to be more of an issue at these low speeds as getting it too far out can result in a spin.

Even at a slow speed like you mentioned, the plane stays coordinated even with SAS off.

[PFunk1606688187]

Although the A10 is fairly noob-friendly in this regard, I find it's rudder control to be cumbersome, and it doesn't help I use a keyboard either.

 

I can't think of a more cumbersome way to actuate a linear control surface than through a key stroke.

 

Frankly I find the process of compensating for slip easy, but I have rudder pedals and time in cockpit to teach me muscle memory that lets me step on the ball without even referencing the ADI and its alway right on.

 

Keystrokes however... bleh, I dunno how you people manage. :smilewink:

 

Even at a slow speed like you mentioned, the plane stays coordinated even with SAS off.

 

I believe this has been discussed and the conclusion was that its a bug in the FM, that you actually get slightly better turn coordination with SAS off, and that SAS doesn't actually do its job as well as it would in real life. I can't remember it exactly, but a search might turn it up.

 

Its one of those miscellaneous details that likely doesn't get a close look and gets forgotten on the bug list because it doesn't really hurt the simulation in the end. I know that it was or is the same case with the Anti-Skid system, where its actually more productive to just turn it off and slam full brakes because even while skidding you'll stop faster than the Anti-Skid logic would let you with no consequences.

 

I personally don't care if its better or not, I just step on the ball because thats just a habit from flying IL-2 planes.

 

It would be nice if that bug were fixed, but I don't know if it'll ever get done. That damned triangle in the glide slope indicator is still there.

[kontiuka]

Ya, P*Funk, that's what I was ultimately getting at, that it seems like a bug, without overtly saying it. I mean I'm just learning the plane so I was just trying to see if I was missing something.

[camsr]

I can't think of a more cumbersome way to actuate a linear control surface than through a key stroke.

 

Frankly I find the process of compensating for slip easy, but I have rudder pedals and time in cockpit to teach me muscle memory that lets me step on the ball without even referencing the ADI and its alway right on.

 

Keystrokes however... bleh, I dunno how you people manage. :smilewink:

 

It goes like this...

 

To enter the turn coordinated, tap rudder button a bit, tap roll about 50/50 on/off at a rate of .4 seconds, keep tapping both while in the turn.

 

The impossible part is exiting the bank coordinated with the rudder, which requires more finesse than tapping is gonna provide :thumbup:

[Rainmaker]

Not sure if the acronyms are the same...

 

But in the F-15 world

 

ARI = Aileron/Rudder Interconnect

 

Short answer, provides rudder inputs with lateral stick deflection to offset the unwanted flight movements when the ailerons are used. Not exactly sure how it all works in the A-10, nor the F-15 really, just understand the basics.

[aaron886]

Google "kinematic coupling." That should explain the purpose, although for an aircraft like the F-15 it is far more critical than for the A-10.

[PFunk1606688187]

It goes like this...

 

To enter the turn coordinated, tap rudder button a bit, tap roll about 50/50 on/off at a rate of .4 seconds, keep tapping both while in the turn.

 

The impossible part is exiting the bank coordinated with the rudder, which requires more finesse than tapping is gonna provide :thumbup:

 

 

Sounds like if Street Fighter were a sim....

[camsr]

Well I have found that reducing the throttle on the inside engine acts somewhat to make up for it. Dual throttle is actually quite easy on the keyboard if you use my keybinds :)