Artificail Horizon Question,

Ali Cat

Ali Cat

Charter Member
I'm getting the knobs of an artificail Horizon to work and I don't know how the real thing works. Here's sequence of what I have now.

At startup (takeoff) ...

View attachment 34499

After adjusting the bias knob (fine tune?) up ...

View attachment 34500

And finally after hitting the cage knob ...

View attachment 34501

If the bias knob is left untouched hitting the cage knob causes the horizon bar to center on the horizontal center as it should. The question is with a bias should the bar when caged include the bias and thus center off center (up in the case above)? Or should the bias be ignored when caged and go to the horizontal center?

Or perhaps this whole approach is wrong. I could make the wings bar move up and down and leave the horizon bar alone. This is how the stock hellcat gauge works.

Which way is best?


AC
 
The top pic appears to be the correct one. It shows a pronounced nose high attitude, which would be correct for a tail dragger like the Hellcat with all three wheels on the ground.
 
Oglivie,

Sorry, I tried to make the question clear but it looks like I didn't do such a good job.

The top pic is definitely correct but what should it look like after a bias is dialed in (bottom center knob) and the cage knob is hit (bottom right knob)? On the second pic I have just dialed in positive bias (up). Next, the last pic is after hitting the cage knob. As I have it coded now with the bias always used, caging causes the horizon bar to move well above the horizontal center.

If I moved, intead, the wings bar it's a no brainer. It would have to work just like the Hellcat gauge. The reason I first chose the current approach is that the wings bar does not have an extended base. This tells me that in the original gauge (Fs9) the wings bar does not move. I can extend the wings bar base fairly easily but I was trying to stay loyal to the Fs9 original.

And that leads me to the current dilema. With a non-zero bias when the cage knob is hit should the horizontal bar be locked off center (as 3rd pic) or should the bias in this case be ignored and this bar goes to the horizontal center (center of the gauge)?

It's a hard question to ask clearly - hope this helps.


AC
 
No Problem,

... and thanks for trying. We'll "just let'er set" and see if I get an answer. If not, I can always just move the wings bar and it will look just fine.

Thanks for the link too - can't believe I've missed that one. I may have a number of questions for that forum.


AC
 
Hi Ali Cat I am only a virtual flyer so I stand to be corrected by a real airman who really knows, in case there are none in the basement, I'd interpret the answer as...
The navigation instruments have to be fine tuned to allow for variations in the aircraft. Such as loading and trim.
The pilot has to be able to assure him/her self that the instrument is as accurate as he can.
One would fly straight and level using the other instruments, (vertical speed indicator and direction indicator) to confirm the fine adjustments for the attitude indicator,
so
one knob adjusts the pitch reading, so that you can make the plane fly level as the center of gravity shifts, Say due to using up fuel or delivering your payload. The other adjusts the roll reading, so the plane keeps the same heading when the gauge shows the wings are level.

I imagine the adjustments are quite fine,

I also imagine that the sort of subtle variations that might require the adjustments to be made do not occur in simulated flight unless you program them in.

Does that help?
 
Nope my good fellow, that's not it. Since I'm headed towards a 1000 words I'll try a picture. Just for clarity here's the Hellcat ...

View attachment 34519

And here's the question with the new gauge ...

View attachment 34520

Note my assumptions/guesses:

1. Bottom right knob is the cage as the bmp file is named "Adi_cage_knob".

2. Bottom center knob is the bias (pitch trim) since that's what it is on the Hellcat. The bmp file is named "Adi_knob" so no help there.

3. The wings bar does not move because it does not have an extra long base (the vertical part below the wings).

If any of these assumptions are wrong (especially the last) then I'm just barking up the wrong tree.

I was not planning on getting these knobs working at all, but then it hit me that this gauge might see some reuse. I'd like to get it right. Again, I could just make the wings bar move up and down but it seems this was not the authors intention.


AC

Edit: Oops - that would be a diving turn.
 
I’ve resolved my question above. It is now very apparent that my assumption #3 is wrong and that this new gauge works just as the stock Hellcat one. A description of how I made such a mistake is below but first a bit of good news as more will probably be interested in that. The attitude indicator is now finished and both knobs work well. Also, I got the cage knob to spin rather jump from the on and off positions – kinda cool.
　
The Mistake:
　
I first laid out the elements of the gage on its background some months ago. Back then I did the final tweaking of the element positions basically by trial and error. This involved making x & y changes, compiling and testing in CFS2. This approach is slow as to test a new change of only a pixel or 2, the whole process has to be repeated. I’ve since found a way to layout all the elements from within GIMP to get the coordinates directly that go into the code. This method is faster but it is also more precise. To cut the point earlier today I used this method to check the attitude gage and notice something right off. Where I had the wings bar set would cause several pixels to be blocked out by that element’s mask (bmp that determines how the perimeter of the element is clipped ie not shown). Using the old method, basically eyeballing the panel within CFS2 these missing few pixels were hard to see and I didn’t catch it. More simply, the wings bar is extended, though only by a few pixels, and that makes the logic that lead to my assumption #3 wrong.
　

Sorry for the bother,
AC
 
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