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Errant RPM Indications with HXr

PostPosted: Fri Sep 28, 2018 5:08 am
by glk0346
Need help resolving an errant RPM indication on my HXr EFIS. System was working fine until today.

Fired up my aircraft and immediately noticed what appeared to be an incorrect RPM reading. First I couldn't get the rpm to 1700 for a mag check let alone to full static power at 2200 rpm. Engine was running smoothly. Pulled out my hand-held indicator and the engine was indeed developing full static rpm - 2250 rpm. Hmm. Reduced power to 1700 as indicated by my hand-held indicator; HXr reading 1490 with the mag switch in the BOTH position.

Switching to LEFT mag as one does in conducting the mag check and noticed the usual 50 RPM drop but the EFIS was still indicating incorrectly - 1450.

When I switched to the RIGHT mag, the indication dropped to ZERO, but would occasionally got to 1700, then back to ZERO. Ordinarily this would be an indication of a lose connection, somewhere. It kept doing this.

Shut down the aircraft and after a period of cooling, checked the right and left mag P stub connections along with the inline resistor connections. All were correct and tight. I also pulled the 25 pin D stub EIS connector and inspected the Rt and Left mag inputs. Nothing out of the ordinary. I'm stumped to put it mildly. The Rt mag appears to be putting out a consistent, although incorrect, reading with no fluctuations.

It appears that the Rt mag may be faulty but not being an A&P and not attuned to mag operations, I'm at a loss.


Re: Errant RPM Indications with HXr

PostPosted: Sat Sep 29, 2018 1:28 am
by glk0346
Errant RPM readings with HXr update.

Well...after a few hours of troubleshooting I've determined that it is not the Mags but the Eng Info Sys (EIS) that appears to be the culprit.

While running through some checks to ascertain which mag is doing what I was hit with a screen where every single engine parameter suddenly went to MAX. Imagine looking at the CHT and EGT bar graph readings when they all suddenly pegged out at the top of the chart. What a surprise to go from 285 CHT to 1700 instantly. I turned off my battery and essential bus for a few minutes. Reengaged and rebooted only to have it do the same thing after about 5 minutes.

This is not a wiring problem but clearly a SW issue with my EIS.

Re: Errant RPM Indications with HXr

PostPosted: Sat Sep 29, 2018 3:48 am
by Bobturner
Not clear what the issue is. You could send the box to GRT and ask them to check it out. If it was mine, I’d disconnect the egt/cht plug and see if it behaves properly. If no, I’d disconnect all the inputs except power and ground. If the box stops acting strange, add inputs one at a time until you find the trouble. If the box is wierd with no inputs, it probably needs to go back.

Re: Errant RPM Indications with HXr

PostPosted: Sat Sep 29, 2018 2:31 pm
by glk0346
The issue is I am not getting a consistent and accurate RPM reading no matter which mag I went to, regardless of the fact that the system was working perfectly fine until now. Secondly, All the wiring and connections check out fine. After doing some thorough troubleshooting, with the aid of my IA, we determined that something is amiss with the EIS Module. This conclusion was based on what happened after doing the troubleshooting when while running up the engine all the engine and systems indicators max out. Everything went to RED. After shutting the engine down, allowing for cooling off, we checked everything again with the same results. Started the engine and the RPM indications were again fluctuating and not accurate. After about five minutes of this, all the engine and systems indications suddenly maxed out when they in fact are all normal.

Conclusion: The EIS module is not functioning properly

I'm going to send it in to GRT for a full check out.