Accu-Sim C-1 Autopilot presented by mattgn

The new Accu-sim C-1 autopilot is actually very simple to use, although it looks complicated at first. Once you start messing around with it, you'll realise how easy it is to use.

There are 2 parts to the C-1 Autopilot (ap): the ap panel itself, with twiddly knobs and flashy light things, and the Pilots Directional Indicator (PDI) located just to the right of the Flux Gate (compass) on the pilots dash.

Familiarisation of the C-1

Left hand side toggle switches: the top switch which is "gated" to the Stab switch is the master switch. If you flick that over to the right, it powers up the unit but does not take control of any of the control surfaces. Below that is the Aileron switch, and until you flick that over to the "On" (right) position, the AP will not control ailerons, same with the rudder and elevator switches. All 3 need to be moved over to the right in order to pass those control surfaces over to the ap. The bottom switch couples the PDI to the ap, which I'll explain very shortly.

The lights along the top are indicator lights which, when on, tell you that the ap is moving those control surfaces in order to achieve what you're telling it to do. The on off switch to the right of the lights turns the indicators on and off.

Top 3 rotating knobs labelled "To Lower R.Wing, If PDI Right, and To Raise Nose" are the controls to use to neutralise the control surfaces in a particular position. For example, you will use the "To Raise Nose" a lot, because that's the control that controls your elevators.
Example : With the ap on and all toggle switches to the right, we want to initiate and hold a 1000fpm climb. We rotate the "To raise nose" knob to the right, and the nose goes up, we continue to rotate that knob until the A/C settles at our desired vertical speed (VS). When the ap has the elevator in the correct position that you have set it with the "To raise nose" knob, the indicator light will extinguish, telling you that the ap is happy as a pig in poop about where it's at with the world.
If you wanted to maintain a constant 10 deg bank to the left, you could move the "To lower R. wing" knob to the left, and keep going until you were happy that the ap was holding your deg of bank for you. The "If PDI Right" does the same thing with your rudder.

2nd row of rotating knobs are for Sensitivity, which as any good lady will tell you is what all women want.
These affect how control inputs are made by your ap in order to carry out your orders. For example, it's a bit turbulent, the planes bucking this way and that. If you have the sensitivity set too high, the ap will go bananas trying to do it's thing, because it's making all these tiny little corrections to elevators, ailerons etc. It's a Catch 22 of course, because higher sens' values will provide more precision, but lower values will result in sluggish behaviour. Find the balance before you shake your baby to bits.

3rd Row of rotating knobs "Ratio".
These boys decide how much throw your ap puts into the control surfaces when adjusting for a deviation, as in turbulence etc. Too much will cause excessive control surface movement, too little and the ap will be there all day trying to get your wings level.

4th Row "Turn Compensation".
This is where you trim the ap for turns, it's that simple. When you order a turn, you can adjust these knobs so that your turn is at the AOB that you want, that the rudder is co-ordinated, and that you maintain altitude throughout the turn.
For example: We order a left turn, the AOB is too shallow, the turn and slip bubble is way out of centre, and the A/C leaps into a 500fpm climb. We increase the "Increase Bank" knob until we're happy with the AOB, we increase or decrease the "To Decrease Skid" knob until the Turn and Slip bubble is centered throughout the turn, (found to work in conjunction with the rudder setting in the 'Ratio' settings) and we reduce the "Up Elev." until we're set in our turn with our VSI at zero.

How To TURN !!   3 ways to do this.

First, and easiest, is to have all toggle switches On (right) and click "Centre" on the "HOLD PDI (OFF)" text at the bottom right. The A/C will bank initially, then level it's wings. Then click "right" or "left" in the same text area. The PDI needle will swing in whichever direction you've ordered a turn and the A/C will follow it. Then when your desired heading is about to be reached, click "Centre". That's it. 

Second, set the "HOLD HEADING (OFF)" figure until your desired heading figure shows up, then click "HOLD HEADING (OFF)" and it will switch on, and turn to your heading that you set.

Third, use the "Turn Control" in the very top left of the panel.  You can initiate turns with the "Hold PDI" (on), as the "Turn Control" overides the PDI Command.

And that's about it.
All of the above is what I have found playing with the unit, and from what I have learned from the manuals.
If I haven't made some things clear, please don't heitate to ask me about it when you see me on TS. 

C1-AP Update - May 6, 2010

I've now tuned my C-1 AP for Rate 1 Turns, and have had good success with timings for 180 deg turns anywhere between 57 and 63 seconds, and a full 360 deg turn anywhere between 1:57 and 2:03, depending on the weather of course, so pretty close.

Now the C-1 applies rudder very slowly, no matter what the C-1 AP settings are at, e.g. Sensitivity, Ratio etc. So what you will find is that the start of the turn is very sloppy, i.e. lots of sideslip, then expect too much rudder before the turn settles into a nicely coordinated Rate 1 after about 15 to 20 seconds.
I have attempted to erase the initial sideslip with increased ratio, however all that does is gives too much rudder during the "settled" phase of the turn, once the AP has moved the control surfaces to where you've ordered them to be.

So the initial sideslip and un-coordinated flight at the start of the turns is something that we'll have to live with, unless I can find someone to shed light on increasing the actual speed the AP moves the rudder controls (when you order a turn, just take note of how slowly the rudder pedals move in relation to the other controls) and to quote from the pilots notes for the Fortress "The controls are quick in response and effective: the ailerons are reasonably light, the elevator slightly heavy, and the rudder extremely heavy." Perhaps that is why the AP takes a decade to move the thing...!


IMPORTANT: The settings you tune your C-1 AP to for a rate 1 turn at 150mph, will NOT provide the same coordination and turn rate at higher airspeeds, so you'll have to adjust the settings, i.e. lower settings for high cruise speeds etc.

I have added my C-1 AP settings here, so you can plug the numbers into your C-1 and see what you think. These settings are for a trimmed A/C at 150mph and will maintain current altitude (depending on weather like I said).

From top row to bottom row reading left to right:

Aileron Centering Knob: 0%
Rudder Centering Knob: 0%
Elevator Centering Knob: 25%

Aileron Sensitivity Knob: 40%
Rudder Sensitivity Knob: 64%
Elevator Sensitivity Knob: 40%

Aileron Ratio Knob: 45%
Rudder Ratio Knob: 27%
Elevator Ratio Knob: 15%

Aileron Turn Compensation Knob: 35%
Rudder Turn Compensation Knob: 9%
Elevator Turn Compensation Knob: -50% (minus 50%)

It's by far an exact science, as when you start to play with one setting, it affects something else. So trial and error is the way forward folks.
I am going to try the AP whilst in formation and see just how dangerous the initial sloppiness of the turns is in relation to maintaining position.

Smoke me a kipper, I'll be back for breakfast.

This article was kindly

 presented by mattgn.

Positive developmental comments are welcome in Teamspeak or the Forum

Check back to this article often as it will continue to be updated as we learn

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