DFC90 Update #2

Just prior to dropping the plane off for annual, I flew it to Gardner Avionics to get the DFC90 swapped out.  This is the third unit to be installed and I was hoping that this one would work as advertised.  Due to crappy weather, I could only fly it home and didn’t get to put it though any real testing.  It seemed to be tracking well and flew with no issues.  I stopped for fuel at Enterprise and as I held short of the runway to depart, the PFD completely blanked out!  After a couple of minutes it came back on, so I carefully flew it home and put the plane away for the night.  The next day I flew it to its annual and all seem to be working.  During annual, the mechanics said it failed three times on them as well.  During this annual, I also had the mechanics completely re-rig the aircraft to make sure that it was set up properly since this might also have an effect on the autopilot.  All of this PFD failures has me thinking that the PFD has been the issue all along and not the DFC90s.

On April 2^nd, I went to pick up the plane from annual.  I did my preflight and all was well.  About five minutes after start-up while doing my checks, the PFD failed again.  Since the weather was severe clear (VFR), I carefully flew it home and called Avidyne.  The following week they sent my old PFD back (now upgraded) and the avionics shop at Dothan swapped it out.  Fingers Crossed!

Saturday April 14^thit was a beautiful day with no wind, so I took the plane up and ran it though all the autopilot testing.  Overbank, stalls, envelope protection, ILS approaches coupled, and just with flight director, all went wonderfully.  Things seemed to be working great! 

Today (April 20^th) I finally got to get the plane up and put it through some more testing to make sure the DFC90 is working.  I flew my father over to 06A (Tuskegee Field).  It was a nice day, but a little windy and a little bumpy.   The autopilot failed repeatedly blowing through heading bug settings, “servo limit” warnings constantly, unable to hold a coarse and no trim annunciation.  I did the Cirrus trim test and the plane still turned to the right like a P51 and to the left like a B747.  CRAP! 

This really puzzled us and since I just had the plane re-rigged, two different PFDs and three DFC90 boxes, I figured it would only be one of two things.  It was either my trim tabs were not adjusted correctly and were overwhelming the servos (unlikely), or a servo(s) was bad and causing the problem.  When we were about to go, I bent the right aileron trim tab down quite a bit to see if that made any difference.  Since the day I bought it, it had always been severely bent up and numerous mechanics had made mention that it seemed excessive.  Here is what I bent it to:

After touring the museum at Tuskegee Field we departed to fly home and found that the autopilot had gotten even worse.  Now regardless of what we did, the “servo limit” came on instantly every time I engaged the autopilot and now I had zero trim control to the left.  The plane would peel off to the right like a P51, but wouldn’t even bank left when I held the trim hat over to the left. 

Well the only change was the trim tab, so we landed at Dothan and I bent it back to its original high angle setting:

After a quick test flight the autopilot tracked almost perfectly and not once did I get the “servo limit” warning and it tracked every heading change perfectly.  What is baffling us both now is that we both felt that bending the tab upwards would have had the opposite effect on the aircraft, but for some reason, it fixed the issue.  Apparently having the tab bend down somehow overpowered the trim servo and wouldn’t allow it to work properly. 

After only one flight, it seems to work great now, but I’ll have to test it some more next week.  It might even need a little more bending upward, but so far it seems to be working.  Fingers crossed!!

2012 Annual

So this year I had to take my aircraft to a new mechanic to get the annual inspection completed.  Unfortunately this guy doesn’t allow owner assisted annuals, but he and his crew are very familiar with Cirrus and he seems to be pretty smart about the aircraft and prices are good.   He’s not the most expensive, but he isn’t the cheapest either.  Flat rate annual for a normally aspirated SR22 w/TKS is $1800 for just the inspection.  Any squawks are on top of that. 

 I knew that he was he was going to be very thorough, which is a good thing, but we started off on a bit of a rough start.  I dropped the plane off on Friday and on Monday he calls and states that the plane would not be done by Friday because I have a cracked cylinder.  My first question was, “did you do a dye penetration test to determine if it was really cracked?”  The response I received was a typical one, “I have been working on planes for years and this is definitely a crack.”  My compression in that cylinder was a 20/80, so there was definitely something wrong, but it’s a bit unnerving that the mechanics didn’t trouble shoot and assumed the worst!  For those not familiar with this type of issue, Continental IO-550s (especially Cirrus) sometimes show what looks like a crack, but in reality they are nothing more than a “dent” or imperfection in the casting that fills with fuel and dirt and looks like a crack.  If a mechanic would clean it up and use magnafux on it, they would see that it ISN’T A CRACK!  From my understanding, many a cylinder have been replaced over the years because of mechanics inability to troubleshoot and just jump to conclusions.  I guess some people have super deep pockets and just don’t care, or more than likely they use these types of expenses as a tax write off.  Regardless, I don’t/can’t work that way!  I learned about this once again from COPA, which in this case saved me $2500-$3000! 

Here is a picture of my cylinder with the "crack" circled in red:

Here are four more pictures of other “cracks” that turned out to NOT be cracks – see any similarities?

So after some discussion on the COPA forum board, I respond to my mechanic in a very nice manner.  I told him that I wanted him to clean up the cylinder with scotch bright and then dye penetrate test the crack.  IF it turns out that it isn’t a crack, then I told him to start the plane up and warm it up real good and check the compressions again.  This time, stake the valve and see if that helps.  I also looked at my EMAX data that showed my exhaust valve (EGT) working normally for about 15 minutes on every flight and then cooling off significantly.  My last oil sample also showed a spike in nickel.  Nickel us used in the valve guides, so I was pretty sure I had a valve issue to start with.  I explained all of this to him and sent him back to work.  Sure enough, an hour later I get a call.  “It’s NOT a crack.”  He did the rest and the best he could get was a 25/80, but he did determine that the exhaust valve was leaking.  YEAH!!!  The bad news though is that the cylinder still has to come off to fix the valve, but that should be significantly cheaper than a new cylinder.

Here is a picture of the cylinder head and you can see the exhaust valve guides are gone and there is a ton of carbon build up.  They will have to lap in the valve and replace the valve guides to fix this.

Other than the cylinder, the aircraft had only minor issues and now is back in service.  After picking it up I determined two mechanical issues that will need to be looked at again.  The first is the intermittent tachometers.  These have come and gone now for six months.  It is obviously something loose, since whenever I hit turbulence they come on or go off.  They were supposed to fix this at annual and they said they did, but what they did, didn’t work.  The second issue is the nose wheel has a wicked shimmy upon touchdown.  The mechanic said that the nose wheel was over tightened to 75lbs, when it should be 25lbs.  This was done by a Cirrus Service Center because it was shaking all over.  The mechanic says that they put it back to 25 and now it is WAY TOO LOOSE!  To fix it, they are saying I have to buy four large washers and a Teflon washer –cost around $50.  For fricken washers!  I will need to look into this some more since this seems a bit extreme for washers. 

The last issue I have that came out of my annual is that the mechanics managed to bend my rear baffling wall behind the engine and now you can see the crease.  How this happened I have no clue, since it would take a lot to bend this wall of aluminum, but somehow they did.  Of course they deny it, but there is no way in hell that it was there prior.  It might not look like all that big of a deal, but I don't like my aircraft looking like it's not taken care of.  I'm guessing I will just have to live with it, but maybe they will surprise me and do the right thing and repair it. 

Overall the plane runs great now, so it’s time to get back at fixing the autopilot!