Instrument Failure

Brig: I don’t have the Century HSI, and I have had no problems with the Sandel (although I haven’t yet mastered all of it’s operating modes).

One thing I want to do when I talk with Hillsboro Aviation is see about replacing the Davtron with a Goodrich 2 1/4" electric AI. They are not cheap ($7,000 approx.) but they are definitely the one additional instrument that would be good to have. The Piper Meridian uses this unit installed with a separate battery of it’s own with an “off-on-test” switch. I think the protocol would be to have the unit on when in IMC. Also some instrument covers at hand would be very helpful.

I have had absolutely no problems with my SR22 after it left Duluth. I hope all of the failures occurred at Duluth before we left. These included an altitude encoder, autopilot pitch servo and avionics master relay. Since then, there has been no problem. Our Cirrus instructor pilot Russ had the screwdriver with him that is referred to in this thread and made the necessary adjustments before we left, and there has been no tracking problem since.

I know there have been a lot of problems with the Century 1000. There was some uncertainty as to whether the installation handling may have contributed to the failure rate since they are very delicate mechanical devices.

I haven’t seen anything specific on the AI failure rate. Has anyone had an AI failure? I don’t recall seeing a specific mention of this.

George,
Would you tell me what was done to resolve the nose wheel shimmy.
Thank you
Bob s/n 109

George -

Actually, the easiest time to make the centering adjustment on the AP is during a long cross country.

Put the AP in GPSS mode and let it stabilize. Then use the screwdriver (VERY VERY VERY small screw driver) to adjust the autopilot centering potentiometer in the middle of the AP. Turn it no more than 1 or 2 DEGREES at a time and then let the AP settle down again.

With a little patience and a long cross country flight, you can get it to center absolutely exactly.

Bob

I hope those of you with avionics problems get them worked out quickly. However, not all the planes are experiencing these issues.

George,

The single biggest issue has been the Century HSI. The Sandel you have in the SR22 has been much more reliable according to the CD Support folks.

Does anyone know if Sandel (or anyone else for that matter) makes a mechanical HSI which could be substituted for the Century. I’m sure Cirrus has explored this issue but interested in any input from the forum members.

Poster: zbsinc
Subject: Re: Instrument Failure

George,
Would you tell me what was done to resolve the nose wheel shimmy.
Thank you
Bob s/n 109


We had the entire compression stack rebuilt on several occasions. On the latest try, the shop communicated closely with Cirrus and finally did it right. Apparently, Top Gun had been installing some washers backwards, which led to crushing and loss of effectiveness. We now have about 20-25 trouble free hours; definitely a record since we got the airplane in late September.

Since the latest fix we have only had the POH-desribed one or two oscillation transient shimmy when landing in a crosswind. And even this can be aborted by more back pressure when you feel it starting. The old out-of-balance clothes washer on spin cycle oscillation from nosewheel touchdown until full stop is gone. My partners and I are very thankful!

George
N747SJ

In reply to:


Then use the screwdriver (VERY VERY VERY small screw driver) to adjust the autopilot centering potentiometer in the middle of the AP.


George,

When Bob says “very”, he means it. Unfortunately, your average jeweller’s screwdriver won’t work, not because the end is too big, but because the shaft isn’t long enough. I made my own out of a cake tester (my wife is still wondering where it went). It takes only a couple of minutes to file the end with a hand file, seconds if you have a grindstone.

The attached pic shows the ‘screwdriver’ next to the front panel of an STEC 55 - it has to go all the way from front to back, which is why it needs to be so long. The ruler gives you a better idea of scale.

Mike.

Bob,
do you nedd the 55 to adjust this way…hoe bout the 30…mine tracks to the left?
Thanks,
Don

Thanks Mike.

Can you remind me which of the two available adjustment holes should be used? Is it the one on the left or the one on the right? I know this was covered about six months ago or so, but I have misplaced the recommendation.

Thanks also to Bob for reminding me to adjust the right of center tendency during a X country rather than on the ILS (the plane does track well to the right en route as well). Sounds a whole lot easier :>)

George
N747SJ

In reply to:


Can you remind me which of the two available adjustment holes should be used? Is it the one on the left or the one on the right? I know this was covered about six months ago or so, but I have misplaced the recommendation.


George,
I found this http://www.s-tec.com/newsletters/approach1098/secrets1098.html>Interesting on [STEC’s site. I think it answers the question.

  • Mike.
    Roll Centering
    Since all S-TEC autopilots are rate based, the interface with the rate gyro must be set properly. This is known as Roll Centering.
    The roll centering adjustment for S-TEC Autopilot Systems 40/50/60 is a 4-turn potentiometer located behind the upper left-hand faceplate screw of the panel mounted programmer unit. On the System 65, the access hole is located between the programmer’s ALT and YD buttons. On a System 55, the access hole is between the REV and ALT buttons. On Systems Twenty and Thirty, access is located through the bottom right-hand mounting screw of the turn coordinator. Access requires a small jewelers screwdriver.
    ](http://www.s-tec.com)

In reply to:


Does anyone know if Sandel (or anyone else for that matter) makes a mechanical HSI which could be substituted for the Century. I’m sure Cirrus has explored this issue but interested in any input from the forum members.


Brig,

The only other mechanical HSI that I’m familiar with is the Bendix/King model but I don’t see it currently listed on their web site, so I wonder if they discontinued it?

Steve

You must be talking of the Goodrich AIM 520 2" I believe.

Please keep us informed about the results you get at your shop, 337 work and cost.

Also, any things you would miss without the Davtron (M803 ?)

As I understand it, vacuum and AI failure are the most significant factors in deadly IMC incidents.

Jaap

During my Wings Aloft instrument course last week, the AI became increasingly unreliable and was replaced under warranty – the day before my check ride. I picked up some bad habits trying to compensate for the lagging tendencies of the AI – little correction produced not much change, bigger correction produced too much change, and the hunt was on!!

No failure flag on the AI, just a tendency to get lazy and lean over with no inputs or to lag attitude changes. Couple of times, it took a very long time to come erect. Wings Aloft mechanic made the judgement call to replace it.

Any idea what happens at Cirrus to analyze returned instruments under warranty replacement?

Cheers
Rick

haven’t seen anything specific on the AI failure rate. Has anyone had an AI failure? I don’t recall seeing a specific mention of this.

Yup, about 150 hours ago. Taking the SR20 home after my Wings Aloft initial training in Seattle. Was sure I had screwed it up somehow but turned out to be a bad AI. Beautiful VMC day over the Cascades. Best time to have the AI go bad for sure.

Having a backup AI instead of the Davitron is an excellent (but expensive) idea. As for the Century, it is hard to believe that CD is still delivering new planes with this POS installed. Waiting on my fourth to come from Duluth and just over 250 hours on the SR20. Each failure has been different which is is testament to how poor the HSI is.

The first squawk started in cold weather where you’d turn the HDG bug and the Mag Card would turn. Eventually the Mag Card turned freely everytime you changed the heading bug. Real bummer when trying to depart on vectored heading. The second Century just stopped moving all together about 25 miles out of an airport I’d never been to before Mag card stuck on 030 degrees. Entered the pattern based on the compass setting and oops! Tower not happy.

The current one, soon to be replaced, is my favorite failure. At PDX (Portland) parallel ILS’s and heavy overcast to 1,200 AGL. Very tight vector to final, setup to intercept the glide slope and the number two GS starts to come in and then goes by. The number one stays fully deflected up and no GS flag. One indicator says you’re way too high and the other says you’re way too low with commercial traffic behind you and parallel to you in Class C. Yet another ‘oh shit’ courtesy of the Century.

The glide slope part of the current HSI no longer responds during the startup test of the Garmins. Even when the new one (factory rebuild, yippee) arrives it will be very difficult to trust any of the functions. I love my SR20 and hate to bitch but Cirrus needs to stop selling this faulty instrument. Might suggest a little COPAtude on this one.

Actually, the most deadly thing about IMC accidents is not instrument or vacuum failure; it’s pilot failure. The majority of accidents in IMC occur when a pilot flies a perfectly good airplane into the ground.

Jaap: There definitely needs to be an alternate source of outside air temperature information. One option for this is the new Mode S transponder that Garmin is coming out with soon, although that may be a an expensive way of doing that. There would have to be plenty of other benefits from the Mode S transponder.

I already have count up and count down timers on the existing (or new) transponder. There is an analog voltmeter on the right side of the panel. There is also GMT shown on the Avedyne display.

As to whether this is possible on a 337 remains an open question, since the Davtron M803 is part of the type certificate for the Cirrus. More will be revealed.

Hi Rick: Good thing you didn’t have to do the check ride with a funky AI. Long times to come erect are definitely not good (flying or otherwise)!

I don’t know that Cirrus keeps any stats on instruments returned on warranty replacement. I was trying to get some notion of the failure rate of the electric AI that Cirrus is using. You might check with the manufacture, although they would probably not be very forthcoming on the numbers.

This is one of the reasons I got the sandel. There are lots of other things I like on the sandel. But the bad ai post I read set before up my options. So far sandel flawless and i like haveing the approch rite in my scan.

In reply to:


Might suggest a little COPAtude on this one.


Brig,

Brought this issue up with Cirrus today. They made the following comments:

  • There are far more Century 1000’s than vacuum models in the field.

  • There are 200+ airplanes flying with Century HSIs with no problem; but about a dozen airplanes have suffered extraordinarily high failure rates - up to 8 in the “worst offender”.

  • There is no discernable pattern of greater reliability or failure rates between vacuum and electric models.

  • There is a suspicion that the problem may indeed be airplane related; therefore, they have brought back the abovementioned “worst offender” for testing. It’s in Duluth at the moment.

  • The HSI is a sophisticated electro-mechanical device, much more delicate than anyone would like it to be.

  • These factors contributed to their decision to offer the Sandel EHSI.

  • They did not “point any fingers” at the manufacturer, Century.

FWIW…

Mike.

Agree Don. My partner and I had decided on putting a Sandel in the airplane aftermarket because of:

  1. The high incidence of failures of the existing HSI before we purchased our SR20
  2. The excellent reviews of the Sandel in the major publications.
  3. Our tire kicking of the Sandel at trade shows.

When Cirrus made it possible to upgrade to a Sandel in our model SR20, we jumped at the chance. Other than the software glitch on start up where it sometimes doesn’t see the Garmins, I consider it one of the best choices of equipment I’ve ever made. In fact, I was so excited about getting the Garmins and the Arnav UNTIL I started flying the Sandel. Why? I don’t really look at the Garmins much with the Sandel except for the radio! I’m a Sandel believer.

Derek

Mike, my experience with the Century electric HSI conflicts with Cirrus’ perspective. I’ve had the following problems:

  1. Glidslope stuck in the one line down position
  2. Glideslope working okay, but flag down
  3. Heading bug off by 10 degrees
  4. Heading bug and yellow arrow collided, bending arrow
  5. Bad interface with autopilot
  6. Replacement unit bad; never installed
  7. 7’s a charm; 7 months problem free!

While I suppose it could be the plane, and I respect Cirrus’s diligence on this, it seems like bad QC by Century.

Andy