Engine Readings - Good and Not So

[EricB]

So there have been some limited discussions of problems or issues people have seen but I'd like to see what people are NORMALLY seeing.  What readings do you see in normal flight, during taxi and/or runup, etc.  Indicate what you think is normal and any issues you may have had so we can all learn.

I've attached a screenshot from today's flight showing what I think are very normal cruise indications.  I will say my Generator light flickers a lot at anything below 2000 rpm and elsewhere on the forum I saw some suggestions about that.

When I got this plane, many of the readings fluctuated radically but we've worked it down to only the generator light being weird. 

[Towner]

This is mine from earlier this month. Don’t remember the altitude or outside temperature though. I’ve never had any issues with flickering or warning lights. EGTs have always been a little farther off than I like.

[shiny.ice]

Here are some random points from an almost 4 hour cross country. Obviously the 912iS is different, but you can see the overall picture:

 

[shiny.ice]

And here it is, zoomed in to the runup and takeoff.

Obviously it's a lot easier with the iS and the Skyview, even if FD won't update their Dynon firmware, sigh.

[shiny.ice]

Last one, here's what it looks like when you take the iS into the 98-100% throttle, which goes out of eco mode. It goes open-loop on the ECU and dumps extra fuel in, which is like being "rich of peak", the EGT drops.

Note on the throttle/flow graph, black is flow, blue is throttle.

 

[Warmi]

Your volts seem pretty low for this rpm.

My regulator just went bad last week after over 600 hours of service . I was seeing intermittent low volts warmings here and there for the last few weeks and then it just died ( ironically during my annual at my mechanics shop - probably the best place for this to happen )

Here is a graph of my volts vs rpm on my flight to his place ( it is steady about 13.7 volts for the whole cruise but it was dipping during run-up and then during landing on idle)

 

 

 

The second one is when my mechanic was running the engine on the ground - it briefly went to 13.5 or so volts and then went downhill and never recovered regardless of the rpm.

[Tom Baker]

22 hours ago, EricB said:

So there have been some limited discussions of problems or issues people have seen but I'd like to see what people are NORMALLY seeing.  What readings do you see in normal flight, during taxi and/or runup, etc.  Indicate what you think is normal and any issues you may have had so we can all learn.

I've attached a screenshot from today's flight showing what I think are very normal cruise indications.  I will say my Generator light flickers a lot at anything below 2000 rpm and elsewhere on the forum I saw some suggestions about that.

When I got this plane, many of the readings fluctuated radically but we've worked it down to only the generator light being weird. 

I have seen more than once when the blinking generator light was a predecessor to a voltage regulator failure.  

[airhound]

Happy Thanks Giving all. 
 

Tried other Flier posts without response . Forgive me for throwing in a topic here. 
Problem: I’ve been told by IC techs and others that the whine (intensity is directly related to power changes) in my phones is an RFI related/Ground loop thingy. 

Every grounding point has been cleaned and tightened, head phone jacks have isolators in place. No change. 

Haven’t looked to see if mfg shielding is touching anything near connecting points in the mike jack or the wiring condition of the optional limo jacks.

Anyone out there eliminated this demon please share.

Eternally Thankful,

Doug

 

[EricB]

First - RFI and ground loop are very different things.  Ignore anyone who doesn't know the difference.  All alternators put out RF interference; its the nature of the beast.  But, that RF should not be transferred to the DC circuits that power our radios and audio gear.  You failed to mention just what the issue was.

If the RF is coming down the DC line, it might be that the capacitor that's supposed to "smooth out" the voltage post being coverted to DC is not doing its job.  In that case it is either the capacitor itself, or insufficient grounding of the minus side of the cap.  If the RF is being "picked up" by other wiring then shielding or grounding of those leads is the issue.  

There is a ground buss on the firewall of the CTLS where several items are grounded.  You should check that all those connections are tight, not corroded, and done with sufficiently large wire that the wire itself does not offer a resistance to ground.  Anything that seems to be "grounded" with a very light gauge wire should have that wire replaced.  Also note that ground wires should be "home run" to the ground buss and not daisy chained through another "possible" ground point.  

If the shielding is "touching something" that would not cause an issue as the shield wire had better be grounded or it isn't really a shield wire.  

I have no idea what a "limo jack" is.  That's not a standard engineering term.  

 

[EricB]

Just for completeness, a "ground loop" happens when a circuit is grounded at more than one point but those 2 points do no agree on what is ground.  That is, a voltage exists between the assumed ground points.  In most audio circuits this results in a hum since we supply 60 Hz AC to our gear in the USA.  

[Anticept]

Limo jacks refer to the bose 6 pin jack.

[shiny.ice]

22 hours ago, Anticept said:

Limo jacks refer to the bose 6 pin jack.

Limo, aka LEMO, jack, named after the manufacturer: https://www.lemo.com/int_en/solutions/originals/b-indoor-keyed.html

 

[Anticept]

Here's the part numbers specifically: https://aviation.stackexchange.com/a/50447

There are premade sockets and harnesses available from aircraft spruce for these bose connectors as well, you have to search for them.

[airhound]

Thank you Eric and Anticept. How would one run down a Ground loop hum in a iS? 

[Anticept]

First and foremost: keeping voltage drop to a minimum on wiring. That's the Achilles heel it seems of these flight designs. Carrying grounding power through steel bolts in the firewall, not using a quality terminal block for grounds, daisy chaining wire terminations instead of using a bus bar, spade terminal grounds...

Check for voltage drop, clean those up first.

Ground loops are mainly a concern when audio systems are involved that don't have great filtering, and when you mix it with a not so great grounding system, the fluctuations ripple through the system and start becoming audible.

[EricB]

So if you go through each point I made and keep in mind what Anticept notes (about grounds and daisy chaining), that's your first step.  Second step would be to have decent voltmeter.  Measure resistance between the "ground" points on radios, the Dynon shelves, and other items with the "main" ground buss on the firewall.  Almost any value other than zero should cause you to upgrade/clean/tighten the ground connections on the offending item.  Measure AC voltage on the 12 V DC being supplied to the avionics master.  There shouldn't be any.  If there is - the filter capacitor isn't doing its job or isn't grounded properly.  However, this last point is RF interference not a ground loop.

 

 

[Anticept]

It doesn't help either that flight design chose two wire with a shield for the jacks, and use the shield as the ground...

There's a few other wires i had found over the years that should have been shield wire and it's just plain...