Partial panel SR20

Guest Discussion
1

N204AK and I was at 8000 feet at 7PM enjoying a smooth cirrus evening on autopilot. During the preceeding hours, the nav needle had progressively increased its “crab” in a clockwise direction. Crosswind, lazy gyro, Garmin with a learning disability… all these things crossed my mind, but none of them took away from the beauty of the airplane.
In an instant, the plane banked sharply to the right and the nav flags popped up on the Century 1000 HSI. Rule #1 is fly the plane, and now I know that the aileron motors are indeed easy to overpower, just like my good buddy Matt Sullivan from Wings Aloft promised.
I pulled the fuses for the autopilot motors, and the need to fight the motors stopped. Now I could hand fly the plane without exerting significant wrist flexion/extension. It was trouble shooting time. I reset the fuses and the bank to the right came back immediately. I re-caged the gyro/HSI, but the bank returned. I unslaved and reslaved the gyro, but to no avail. I found that with the gyro unslaved, the autopilot didn’t bank adversely, and the Heading Bug DID act like an old fasioned wing leveler. And so I flew home with a wing leveler, autopilot motor fuses ON, and gyro unslaved. Glideslope #2 was used with Garmin #2 and the Garmin 430 Nav position 4 screen was used to simulate a gyro (and it does quite well. The lag is waaaay less that the compass).
I called Mike Busch at CD who jumped on the problem like a big dog. He set me up with Sterling Avionics in Concord, CA. I took the plane down after work where it was determined that the internal gyro within the Century 1000 had quit spinning. Cirrus sent him another one the next day and the problem is fixed.
Lesson: Remember the Nav-4 GPS compass screen.
: Electric gyros fail, too.

  : For Century 1000 gyro failures, unslave the unit and fly the heading bug as a wing leverer.

  : The initial symptoms seemed to indicate possible failure in several systems. The Wings Aloft guide and course in invaluable.

And by the way, N204AK flew to Medford, Oregon yesterday, leaving a 400 foot ceiling at Concord and leveling off at 10,000 feet. TAS 150, 11 gph, and the flight came off without a hitch. This is a beautiful airplane.aa

2

One thing about your story confuses me. When the plane first banked steeply to one side, did you disconnect the AP? Were you not able to? Why pull the fuses?

3

N204AK and I was at 8000 feet at 7PM enjoying a smooth cirrus evening on autopilot. During the preceeding hours, the nav needle had progressively increased its “crab” in a clockwise direction. Crosswind, lazy gyro, Garmin with a learning disability… all these things crossed my mind, but none of them took away from the beauty of the airplane.
In an instant, the plane banked sharply to the right and the nav flags popped up on the Century 1000 HSI. Rule #1 is fly the plane, and now I know that the aileron motors are indeed easy to overpower, just like my good buddy Matt Sullivan from Wings Aloft promised.
I pulled the fuses for the autopilot motors, and the need to fight the motors stopped. Now I could hand fly the plane without exerting significant wrist flexion/extension. It was trouble shooting time. I reset the fuses and the bank to the right came back immediately. I re-caged the gyro/HSI, but the bank returned. I unslaved and reslaved the gyro, but to no avail. I found that with the gyro unslaved, the autopilot didn’t bank adversely, and the Heading Bug DID act like an old fasioned wing leveler. And so I flew home with a wing leveler, autopilot motor fuses ON, and gyro unslaved. Glideslope #2 was used with Garmin #2 and the Garmin 430 Nav position 4 screen was used to simulate a gyro (and it does quite well. The lag is waaaay less that the compass).
I called Mike Busch at CD who jumped on the problem like a big dog. He set me up with Sterling Avionics in Concord, CA. I took the plane down after work where it was determined that the internal gyro within the Century 1000 had quit spinning. Cirrus sent him another one the next day and the problem is fixed.
Lesson: Remember the Nav-4 GPS compass screen.
: Electric gyros fail, too.

: For Century 1000 gyro failures, unslave the unit and fly the heading bug as a wing leverer.

: The initial symptoms seemed to indicate possible failure in several systems. The Wings Aloft guide and course in invaluable.
And by the way, N204AK flew to Medford, Oregon yesterday, leaving a 400 foot ceiling at Concord and leveling off at 10,000 feet. TAS 150, 11 gph, and the flight came off without a hitch. This is a beautiful airplane.aa
Just my observation of this post but it seems that there have been an unusual number of Century system failures in the early Cirrus deliveries. I know personally of one locally in my area and several reported on this forum.

My concern, as someone who has not made up his mind about the “B” VS “C” package, is the

following: If the HSI fails, the “B” package folks have no VOR/Localizer function AT ALL! It would be all GPS alone on the number 2 Garmin 420. I always thought the HSI was a valuable tool to have on board but it seems like a weak link in this system. It has no backup and both DG and Vor functions are simultaneously lost. NOT GOOD!

Secondly, if Andrew had an HSI problem, since the autopilot works off the turn and bank indicator, why not just revert to Heading mode alone?

Brian

4

Given Andrew’s situation, I’m wondering whether the STEC GPSS option would provide another nice backup. As I understand it, GPSS provides a direct connection between the GPS unit and the autopilot, effectively cutting the HSI/CDI out of the loop. If Andrew had been flying using GPSS, I doubt the failure of the Century HSI would have had any effect on course tracking. Does that sound right?

Bill Rust, SR20 #576

Sunnyvale, CA

5

My concern, as someone who has not made up his mind about the “B” VS “C” package, is the

following: If the HSI fails, the “B” package folks have no VOR/Localizer function AT ALL! It would be all GPS alone on the number 2 Garmin 420. I always thought the HSI was a valuable tool to have on board but it seems like a weak link in this system. It has no backup and both DG and Vor functions are simultaneously lost. NOT GOOD!

Actually not true–you have a couple of options. First, if the gyro has gone, assuming that the card isn’t spinning, you can unslave the gyro, manually turn the card so that the course needle points up, and fly the needle the old-fashioned way. Or you could use the CDI on the Garmin display (makes for an ugly scan, but well worth practicing.) The Garmin won’t give you a glideslope indication, but presumably the HSI glideslope indicator is also still functioning.

Secondly, if Andrew had an HSI problem, since the autopilot works off the turn and bank indicator, why not just revert to Heading mode alone?

Brian

Sounds like that’s what he did. From the sound of it, the autopilot was commanding a standard rate turn, and assuming that he had altitude hold turned on the plane would have simply flown in circles until it ran out of gas. Hitting the a/p disconnect button would have been the best first move, but as I noted in my other post, when things get weird it can really get your brain locked up. It’s very easy to second-guess this stuff sitting in front of the computer.

Practicing for failure scenarios in avionics is very important, and there are a lot more interesting scenarios (and interesting options) with all this new stuff.

6

If the HSI fails, the “B” package folks have no VOR/Localizer function AT ALL! It would be all GPS alone on the number 2 Garmin 420. I always thought the HSI was a valuable tool to have on board but it seems like a weak link in this system. >Brian

I agree with you, except I wouldn’t place all of the blame on the HSI, because a DG, #1 Garmin, or its indicator could fail too. It is really a problem with not having two Garmin 430’s. If you have two 430’s, you have great redundancy. Plus, you’ll have two indicators for redundancy – the HSI and the VOR/Loc indicator for the second Garmin 430. Those on the fence should spend a few bucks more for the “C” package if they intend to fly IFR down to ILS minimums.

7

My concern, as someone who has not made up his mind about the “B” VS “C” package, is the

following: If the HSI fails, the “B” package folks have no VOR/Localizer function AT ALL! It would be all GPS alone on the number 2 Garmin 420. I always thought the HSI was a valuable tool to have on board but it seems like a weak link in this system. It has no backup and both DG and Vor functions are simultaneously lost. NOT GOOD!

Actually not true–you have a couple of options. First, if the gyro has gone, assuming that the card isn’t spinning, you can unslave the gyro, manually turn the card so that the course needle points up, and fly the needle the old-fashioned way. Or you could use the CDI on the Garmin display (makes for an ugly scan, but well worth practicing.) The Garmin won’t give you a glideslope indication, but presumably the HSI glideslope indicator is also still functioning.

Secondly, if Andrew had an HSI problem, since the autopilot works off the turn and bank indicator, why not just revert to Heading mode alone?

Brian

Sounds like that’s what he did. From the sound of it, the autopilot was commanding a standard rate turn, and assuming that he had altitude hold turned on the plane would have simply flown in circles until it ran out of gas. Hitting the a/p disconnect button would have been the best first move, but as I noted in my other post, when things get weird it can really get your brain locked up. It’s very easy to second-guess this stuff sitting in front of the computer.

Practicing for failure scenarios in avionics is very important, and there are a lot more interesting scenarios (and interesting options) with all this new stuff.

Pardon my oversight, but the first move made was indeed to return the plane to straight and level flight, then disconnect the autopilot. It was night time over the NMex mountains, and I suffered only mild soiling of my BVDs while pulling my trusty flashlight out. Yes I have great overhead lighting in the SR20, but no lighting where the fuses live, next to my right knee. Although I eventually DID return to altitude hold mode with wing-leveler capability, it took over an hour of worry to attain that level of trust in reinstituting systems one at a time, at night, over mountains, in an aircraft that is new to me. When this happens to me, or to you, the next time, I will simply unslave the gyro. That will leave me with altitude hold and a wing leveler. As for glide slope, it was disabled at the same time the CDI flag went. One would have to us glideslope #2 to shoot the ILS. aa

8

If the HSI fails, the “B” package folks have no VOR/Localizer function AT ALL! It would be all GPS alone on the number 2 Garmin 420. I always thought the HSI was a valuable tool to have on board but it seems like a weak link in this system. >Brian

Couldn’t you replace the GI 102 with a GI 106 at I assume fairly minimal cost?

The 420 is an IFR GPS, could it run the GSI on the 106? I realize it’s not cert for it, but, in a pinch, it would be nice. By not being cert for precision approach, does that mean it doesn’t contain the data for a precision approach?

I agree with you, except I wouldn’t place all of the blame on the HSI, because a DG, #1 Garmin, or its indicator could fail too. It is really a problem with not having two Garmin 430’s. If you have two 430’s, you have great redundancy. Plus, you’ll have two indicators for redundancy – the HSI and the VOR/Loc indicator for the second Garmin 430. Those on the fence should spend a few bucks more for the “C” package if they intend to fly IFR down to ILS minimums.

Somebody said in a thread a while back, when they were comparing the different packages, that two 430’s was more information than could be understood. I disagree. I believe the point of having two 430’s is not to have active and to use two GPS’s at once, but, to have a backup in case one fails, just as you mentioned.

If I were to purchase a B, I think I would replace the GI 102 with a GI 106, but that depends on my next few questions, as I’m a little confused how it all is hooked up together.

I’m sorry if this has all been covered in detail before. I’ll also preface it with, I don’t have GPS in my current plane, and am only just starting on my IFR, so I’m kind of a newbie to this stuff.

In my Cherokee, 1 radio controls 1 NAV CDI, the other radio controls another. Both CDI’s have a GSI.

In the SR20,
The A model contains 1 430 GPS/Nav/Com, 1 250XL GPS/Com, and a GI 106 CDI.

The B model contains 1 430 GPS/Nav/Com, 1 420 GPS/Com, an HSI, and a GI 102 CDI.

The C model contains 2 430 GPS/Nav/Com, an HSI and a GI 106 CDI.

Now, as I understand it, in the A, the CDI is controlled by the 430. I lose the 430, Not only no IFR GPS, but no NAV function either.

Question 1: Can the 250XL run the ARNAV? (despite everyone’s complaints, I imagine it would still help in terms of SA in the soup)

Question 2: In the B, does the single 430 control both the HSI and the CDI? So if you lose the 430, you have no Glide Slope/ILS/NAV whatsoever?

Question 3: In the B, if I replace the GI 102 with a GI 106, what controls it? Just the 430? As asked above, can the 420 be set up to run the GSI on the CDI if it were a GI 106?

Question 4: Why would a CDI NOT contain a GSI?

Question 5: In the C, does 1 430 control the HSI

and the other control the GI 106 CDI? Can you control which 430 controls which HSI/CDI? (I believe the answer is yes, but the paperwork is not too clear on this)

Question 6: Is this all moot and you don’t need a NAV per se, as the CDI/HSI’s can indicate to a selected waypoint on either GPS of any model? (Am I just being a (young) old fart for not trusting GPS and wanting backup NAV functions?).

Question 7: How interlinked are the functions in the 430. Recently, our KX155 lost it’s NAV functions, but the radio still worked fine. So we still had two radios, and one IFR NAV. Are the functions of the 430 similarly fail safe, or, does the whole thing go down if any part of it goes down?

I was planning on going for an A model, but, the more I think about it, I’ve almost never flown an aircraft without two CDI’s/NAV radios in it, and I’m starting to think I’ll feel kind of naked up there with only a single CDI/NAV. Only problem is, the A is about all I can afford. Choice made I guess.

Even if the answer to 6 is yes, I’ll still feel naked in an A with only a single indicator. Oh well.

Thanks, all,

This is an awesome board

Tom

9

If the HSI fails, the “B” package folks have no VOR/Localizer function AT ALL! It would be all GPS alone on the number 2 Garmin 420. I always thought the HSI was a valuable tool to have on board but it seems like a weak link in this system. >Brian

I agree with you, except I wouldn’t place all of the blame on the HSI, because a DG, #1 Garmin, or its indicator could fail too. It is really a problem with not having two Garmin 430’s. If you have two 430’s, you have great redundancy. Plus, you’ll have two indicators for redundancy – the HSI and the VOR/Loc indicator for the second

Garmin 430. Those on the fence should spend a
few bucks more for the “C” package if they intend to fly IFR down to ILS minimums.

Yes for the 430 redundency but on one antenna, I think. I noticed a picture of a new Piper the other day and noticed 2 com antennas and 2 GPS antennas for the Garmin 430s on the top of the aircraft. Piper evidently feels antenna redundency is also a good idea. Comments?

10

Tom, before answering all questions, I think the single answer that will do for all of them is just to say that the glideslope function of either an HSI or CDI is used only for an ILS approach. So in the B model, you do have IFR redundancy because of the two IFR GPSes. What you do not have is redundant ILS capability. The Garmin 420 has no glideslope receiver, so there is no point in its CDI having a glideslope indicator. That CDI is used solely for GPS navigation.

Having two IFR certified GPS units is enough redundancy for me, since I don’t fly a lot of ILS approaches. I can fly any other kind of approach using a single IFR GPS - GPS approaches, VOR, NDB, LOC - including those that require DME. It’s not legal (at least here in Australia) to fly, say, an NDB approach using a GPS, but in an emergency I would have no hesitation in doing so - practice in visual conditions first is a good idea.

This stuff has been kicked around a lot here before, and while I would hesitate to say there is a consensus, my conclusion is that if you fly ILS approaches frequently, you should get the C package, if not the B package is perfectly fine. A is fine for VFR and occasional IFR.

Question 2: In the B, does the single 430 control both the HSI and the CDI?

No, the 430 controls the HSI, and the 420 the CDI.

Question 3: In the B, if I replace the GI 102 with a GI 106, what controls it

The 420. You will still have no GS information on the second head.

Question 4: Why would a CDI NOT contain a GSI?

Because it’s being driven either by a NAV receiver with no glideslope, or a GPS.

Question 5: In the C, does 1 430 control the HSI

and the other control the GI 106 CDI?

Yes.

Can you control which 430 controls which HSI/CDI?

No.

Question 6: Is this all moot and you don’t need a NAV per se, as the CDI/HSI’s can indicate to a selected waypoint on either GPS of any model?

Absolutely. And the GPS does a better job anyway.

(Am I just being a (young) old fart for not trusting GPS and wanting backup NAV functions?).

Yes, unless you need to fly an ILS.

Question 7: How interlinked are the functions in the 430. Recently, our KX155 lost it’s NAV functions, but the radio still worked fine. So we still had two radios, and one IFR NAV. Are the functions of the 430 similarly fail safe, or, does the whole thing go down if any part of it goes down?

That’s difficult. I believe the COM radio is a separate module inside the 430, with a separate power supply, but since it still depends on the display (to set the frequency) there is some common hardware between the GPS and the COM.

11

No matter how you slice it, two is better than one.

12

Yes for the 430 redundency but on one antenna, I think. I noticed a picture of a new Piper the other day and noticed 2 com antennas and 2 GPS antennas for the Garmin 430s on the top of the aircraft. Piper evidently feels antenna redundency is also a good idea. Comments?

David,

I’m pretty sure we have separate antennas/antennae. I know that they are separate for the GPSs - I saw them being installed at the factory.

For the radios, the COM1 antenna is on the top of the fuselage, and the COM2 antenna is on the bottom.

  • Mike.
13

Yes for the 430 redundency but on one antenna, I think.

Negatory!

The GPS #1 antenna is on top of the fuselage (it’s embedded into the fiberglass) the GPS #2 antenna is under the windscreen (if you pull out the Arnav you can see the GPS antenna behind it).

14

Given Andrew’s situation, I’m wondering whether the STEC GPSS option would provide another nice backup. As I understand it, GPSS provides a direct connection between the GPS unit and the autopilot, effectively cutting the HSI/CDI out of the loop. If Andrew had been flying using GPSS, I doubt the failure of the Century HSI would have had any effect on course tracking. Does that sound right?

Bill Rust, SR20 #576

Sunnyvale, CA

Bill: It is my understanding that the GPSS would require the autopilot, which requires the Century gyro. If this understanding is correct, the plane would not steer itself, although the Garmin would still remain functional (as it does anyway on the current GPS)… i.e. not any different. Just remember to unslave the gyro on the century and you can still use the autopilot “heading” mode and turn the heading bug the same way I always did on my 1960’s vintage Comanche 250. aa

15

Given Andrew’s situation, I’m wondering whether the STEC GPSS option would provide another nice backup. As I understand it, GPSS provides a direct connection between the GPS unit and the autopilot, effectively cutting the HSI/CDI out of the loop. If Andrew had been flying using GPSS, I doubt the failure of the Century HSI would have had any effect on course tracking. Does that sound right?

Bill Rust, SR20 #576

Sunnyvale, CA

Bill: It is my understanding that the GPSS would require the autopilot, which requires the Century gyro. If this understanding is correct, the plane would not steer itself, although the Garmin would still remain functional (as it does anyway on the current GPS)… i.e. not any different. Just remember to unslave the gyro on the century and you can still use the autopilot “heading” mode and turn the heading bug the same way I always did on my 1960’s vintage Comanche 250. aa

Andrew:

I do NOT think that is correct. One of the beauties of the Stec autopilot system is that it gets its gyro information from the turn coordinator, NOT the HSI. So a wing leveler mode when the vacuum system or HSI goes out should work perfectly fine and keep you “straight and level”.

Brian

16

I do NOT think that is correct. One of the beauties of the Stec autopilot system is that it gets its gyro information from the turn coordinator, NOT the HSI. So a wing leveler mode when the vacuum system or HSI goes out should work perfectly fine and keep you “straight and level”.

Brian

In heading mode the a/p picks off the position of the heading bug relative to the top of the DG/HSI, and in NAV mode it picks off the position of the HSI course pointer relative to the top of the HSI. None of this will work if the DG/HSI is spinning, and the S-Tec 55 does not have a wing leveler mode.

What is interesting is whether the a/p uses only track information from the GPS when in GPSS mode and ignores the course pickoff completely. I would guess that this is the case, but a definitive answer from S-Tec or Cirrus would be useful in planning failure strategies.

17

I do NOT think that is correct. One of the beauties of the Stec autopilot system is that it gets its gyro information from the turn coordinator, NOT the HSI. So a wing leveler mode when the vacuum system or HSI goes out should work perfectly fine and keep you “straight and level”.

Brian

In heading mode the a/p picks off the position of the heading bug relative to the top of the DG/HSI, and in NAV mode it picks off the position of the HSI course pointer relative to the top of the HSI. None of this will work if the DG/HSI is spinning, and the S-Tec 55 does not have a wing leveler mode.

What is interesting is whether the a/p uses only track information from the GPS when in GPSS mode and ignores the course pickoff completely. I would guess that this is the case, but a definitive answer from S-Tec or Cirrus would be useful in planning failure strategies.

I e-mailed this question to S-TEC. As soon as I get a response I’ll let you all know.

Bill

18

Not sure what you mean by course pickoff, but when in GPSS mode, the a/p will fly the course programmed into the GPS. In this mode, the signal that drives the autopilot comes directly from the GPS, bypassing the HSI completely. This is with an STEC-30 autopilot.

What is interesting is whether the a/p uses only track information from the GPS when in GPSS mode and ignores the course pickoff completely. I would guess that this is the case, but a definitive answer from S-Tec or Cirrus would be useful in planning failure strategies.