Aspen E5 Interface to S-Tec 50 Need KCS-55 Resistor Values

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Bryan Herter

Filing Flight Plan
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Bryan Herter
Help, Just can't find them anywhere. Installed an Aspen E5 and have it interfaced to the S-TEC 50 but need to configure the Roll board for the KCS-55 to be compatible with the Aspen ACU. It had a GPSS 901 and was configured for it, I have the Drawing 0508 that tells me that for the ST-901 remove R6, change R26, R15 and R5 to 43.2K, and for the KCS/55A to just remove R6 (jumper is supposed to be set to pins 2 and 3 for both the 901 and the KCS55A). Unfortunately it doesn't tell me what value resistors were in it originally for R26, R15 and R5 and those values are apparently the values that need to be in place for the KCS/55A configuration along with the R6 removal and jumper 2 and 3. As it is with the 901 configuration it just rolls right. I can't find the document with the resistor matrix that it needs to be for the KCS/55A. Does anyone have access to the original resistor values, or know the definite values needed for the KCS/55A configuration?
Thanks,
Bryan
 
Hi Bryan, the Aspen ACU supports the Stec 50 without anything special. You can just wire the ACU directly to the System 50, select the ACU HSI type to 0 (King 525) and use Normal ACU datum (not reversed). The pin assignments for Stec systems is on page 116-226 of the E5 installation manual. If you are leaving the King 525 in the panel you'll want to cap and stow the heading / course wiring there and not try to parallel it with the ACU - that would cause problems.
 
Hi, thanks. Here's the problem, it didn't have a King HSI, it had an Standard DG, but even worse is that it had previously been modified for the STEC GPSS which had three resistor changes in it. I don't know the original values to put back in so that it is the King HSI configuration which will then work with my ACU/Aspen which is wired up per the E5 install manual.
 
Ah, I see, that's quite a predicament. If a DG, it would have had a heading output but not course output. To make the DG's heading output look like a King 525A heading or figure out the resistor values, all I can think to do is hook up a good oscilloscope or multimeter, and try different values to set the scaling to mimic the King's heading. A variable resistor on the bench could help experiment with different values. From page 91-226, the heading signal from the King uses a 15V reference and scaled as:
500mVdc per degree up to a maximum angle of 30⁰, or 15Vdc. The output remains at +15Vdc from 31⁰ to 180⁰. At 181⁰ it switches to -15Vdc. Likewise for negative angles (HDG bug left of the lubber line) the gradient is -500mVdc per degree up to -30⁰. The output remains at -15Vdc from-31⁰ to -179⁰. At 180⁰ it switches to +15Vdc.
Click to expand...
 
Might call Bob Weber, WebAir consulting. Knows analogue a/p's inside and out.
 
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