AI for Cessna 800B IFCS Autopilot?

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  • #83723

    I have the 800B IFCS autopilot connected to the 4″ AI and HSI in my 421. Everything works reasonable well except for the HSI that has a persistent slaving problem.

    I’m considering an Aspen (put one in my old 210 and loved it), but I’m wondering what to do with the AI.

    Unless I’m mistaken, the Aspen cannot yet provide an attitude reference to the 800B so I’ll need a new AI.

    I can’t move the 4″ AI to a new location since it doesn’t fit, and also I believe it’s expensive to overhaul.

    So…. What are my options for a vacuum driven AI which will drive the 800B autopilot, and what are the costs?

    Question #2 – Will the Aspen display the flight director command bars from the 800B on the display?

    Thanks!
    Robert

    #95713

    Robert,
    Can you get the HSI overhauled? What is the slaving issue? Could it be your magentometer and wiring?

    Last quote on the AI was $1500 to overhaul. Not many places work on those now. I will have to dig up the number.

    I am also curious to hear how the aspen works with the 800B

    Eric

    #95715
    quote EPANNING:

    Robert,
    Can you get the HSI overhauled? What is the slaving issue? Could it be your magentometer and wiring?

    We can’t figure out what the issue is – When I turn on slaving the HSI dutifully slaves to about 15 degrees off. No idea why (and yes, we’ve moved the magnatometor). I’ve given up troubleshooting it, but I’m wide open to other ideas – I’d gladly repair the HSI and go on with life, especially since I’m out the cost of the Aspen to fix my right engine…

    I didn’t know the 4″ AI’s were only $1,500 to overhaul – That’s not bad.

    Robert

    #95719
    quote RCJOHNSON:

    quote EPANNING:

    Robert,
    Can you get the HSI overhauled? What is the slaving issue? Could it be your magentometer and wiring?

    We can’t figure out what the issue is – When I turn on slaving the HSI dutifully slaves to about 15 degrees off. No idea why (and yes, we’ve moved the magnatometor). I’ve given up troubleshooting it, but I’m wide open to other ideas – I’d gladly repair the HSI and go on with life, especially since I’m out the cost of the Aspen to fix my right engine…

    I didn’t know the 4″ AI’s were only $1,500 to overhaul – That’s not bad.

    Robert

    Robert, just as a sanity check on the HSI, you know that you have to adjust it on the ground so that the little white line in the upper right of the HSI is about a 45 degree angle? This is the Gyro Slaving Indicator on the IG-895A HSI. The white line should be moving during flight, but it’s average position should be 45 degrees. Is this part working correctly? It’s not that intuitive that you have to manually set what should be slaved. The adjustment is made by pushing in the heading bug knob and adjusting. Once this is done it will maintain it. Sometimes called card alignment.

    The other HSI question is if you set the heading bug up on the HSI to match the current course, then what is the error (if any) in the flight director command bars? Good is less than 1 degree. If this is working, if the 15 degrees is constant, then it points back to the magnetometer to HSI adjustment referred to above.

    Good luck!

    Eric

    #95720
    quote EPANNING:

    quote RCJOHNSON:

    quote EPANNING:

    Robert,
    Can you get the HSI overhauled? What is the slaving issue? Could it be your magentometer and wiring?

    We can’t figure out what the issue is – When I turn on slaving the HSI dutifully slaves to about 15 degrees off. No idea why (and yes, we’ve moved the magnatometor). I’ve given up troubleshooting it, but I’m wide open to other ideas – I’d gladly repair the HSI and go on with life, especially since I’m out the cost of the Aspen to fix my right engine…

    I didn’t know the 4″ AI’s were only $1,500 to overhaul – That’s not bad.

    Robert

    Robert, just as a sanity check on the HSI, you know that you have to adjust it on the ground so that the little white line in the upper right of the HSI is about a 45 degree angle? This is the Gyro Slaving Indicator on the IG-895A HSI. The white line should be moving during flight, but it’s average position should be 45 degrees. Is this part working correctly? It’s not that intuitive that you have to manually set what should be slaved. The adjustment is made by pushing in the heading bug knob and adjusting. Once this is done it will maintain it. Sometimes called card alignment.

    The other HSI question is if you set the heading bug up on the HSI to match the current course, then what is the error (if any) in the flight director command bars? Good is less than 1 degree. If this is working, if the 15 degrees is constant, then it points back to the magnetometer to HSI adjustment referred to above.

    Good luck!

    Eric

    All good points that I’m aware of. I need to spend a day and just fly / mess with it / fly, but I haven’t yet.

    It works well enough in unslaved mode, but I do have to reset it pretty often. Not fun on a bad weather day when I’m getting vectors and I have to wing it a little bit.

    Robert

    #95721

    We have had similar issues with our 421B. We have replaced the HSI, DG, Flux valve, and all wiring from the flux valve to the DG. We moved the flux valve and have settled in the tail of the aircraft. Absolutely nothing mentioned previous helped with the constant precessing.
    We noticed on a flight at FL21 that the boots did not pop as robust as they should have. Upon landing we had the vacuum pressures checked and adjusted up to the factory settings.
    De Ice boots work great and our HSI/DG system barely precesses. I believe once we re set the flux we will be back in sync. – small things can cure massive headaches occaisionally. Not a single shop, and there were several suggested the vac pressures could be an issue.
    Never know what will cure the ill.

    #95724
    quote RCJOHNSON:

    All good points that I’m aware of. I need to spend a day and just fly / mess with it / fly, but I haven’t yet.

    It works well enough in unslaved mode, but I do have to reset it pretty often. Not fun on a bad weather day when I’m getting vectors and I have to wing it a little bit.

    Robert

    Robert, this is a 4″ electric HSI? If it is precessing in unslaved mode more than it should then it probably does need overhauled. Any service records? When was it last sent out and who did the work? Just to make sure I am clear on this, when you are in slaved mode it is stable – just 15 degrees off. Is that correct?

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