Avionics Ideas

[jlunseth]

I put this put on AOPA and thought I should probably do it here also, to get any Mooney specific ideas.

I have an M20K 231. It has a KFC autopilot, KNS80 RNAV, and King HSI. It also has an MX20 moving map, and had an old style GPS, an Apollo GX60, wired to the moving map. There is nothing else on the moving map.

The Apollo GX60 blew out, and I was thinking about adding a 430W anyway, so that is the plan. I am an instrument student, and want a well equipped instrument aircraft. Having had experiences with equipment failing, I want a second CDI, so the KNS80 will be wired to a new (or reconditioned) CDI, and the 430W will be wired to the HSI and autopilot.

One of the shops I have gotten quotes from is recommending two additional things, a DAC GDC31 GPSS Roll Steering adapter and also a Shadin ADC200 Airdata Computer. In my own thinking about this project, these had not occurred to me and I am not very familiar with either of them. I like the ideas alot. I have done a little research on the GPSS and am thinking that an Icarus might be better because of the audible alerts. I am an old guy and the typical high pitched warning horns in an aircraft are hard for me to hear. I know almost nothing about the Airdata computer except what I have been able to look up online. It looks neat, but the aircraft already has a Hoskins FT-101 fuel flow meter.

I guess I am looking for comments on either of these, and whether there are other units that I should look at. Also, how useful is the Airdata.

I will be doing some long distance travel in the aircraft (have already). Also, the long range plan is to fly this for a couple of years and then perhaps move to a different, larger capacity, faster aircraft, so this is not intended to be my forever one and only, although it might turn out that way. Never know.

[DonMuncy]

I have the  DAC GDC31 GPSS Roll Steering unit (along with my KAP 150 A/P) and think it is great.  It literally commands the A/P to do whatever you have programmed into the 430 except for vertical commands.  It is almost cetainly the best "bang for the buck" I have ever spent on my plane.

Don

[KSMooniac]

I agree with Don and think that GPSS coupled to a WAAS GPS and a/p is one of the best bang-for-the-buck item you can add to your airplane.  An engine monitor is the first thing I would add if you don't already have one.

One other idea you might consider...you could ditch the King HSI and go for an Aspen PFD.  I recommend that for two reasons... the King HSI will eventually require some expensive maintenance whereas (presumably) the solid-state Aspen should run without wearing out.  Right now, the King HSI still has some residual value on trade-in or the used market if you choose to sell it yourself, but that value will diminish as more people install Aspens or Garmin PFDs.  The Aspen includes GPSS, so you wouldn't have to pay for that twice.  You might want to get a quote for an Aspen installed (including trade-in or re-sale value of the King system) in addition to just adding the GPSS to what you have now.  You also might get some overhaul quotes on the HSI, and then see if you wish to roll the dice and hope you don't get to do that before trading airplanes...

[Chris White ex-N205KD]

Scott's idea has a lot of merit.

As stated above, this will give you solid-state attitude ADAHRS, but also a backup attitude indicator (by keeping and moving your steam indicator), another moving map, and an emergency GPS within the Aspen that will remember the flight plan from the 430W if it ever craps out.  Not to mention the wealth of information displayed on the unit that just cannot be shown on mechanical intruments, such as wind speed and direction.  Finally, an instrument scan is MUCH easier when all the instruments are combined into one!  Wait til you fly an ILS or WAAS approach with an Aspen...

You can easily get an Aspen installed for $10k, minus around $2500 +/- trade/resale on the HSI. 

How much does the stand alone GPSS cost installed?

[jlunseth]

Too much money for a plane I don't intend to keep more than a couple of years, and there is zero room in the panel.  If I were going to spend the money I would add traffic and strikescope first, I think.

[KSMooniac]

I think GPSS is somewhere around $1500-$2500 installed, but I'm not too sure since my plane came with it.  The HSI trade-in would put the out-the-door Aspen price in the neighborhood of $5-6k, so the cost delta is $3-4k vs. just the GPSS alone.  I'd say your resale value as well as desirability (ie quick sale when the time comes) would easily be worth the additional 3 or 4 AMU, which you could easily blow next month if you have to service the King HSI... I think the idea is worth serious consideration and a discussion with your avionics installer.

[jrjaks]

Quote: jlunseth

The Apollo GX60 blew out, and I was thinking about adding a 430W anyway, so that is the plan... the 430W will be wired to the HSI and autopilot.

One of the shops I have gotten quotes from is recommending two additional things, a DAC GDC31 GPSS Roll Steering...

[jlunseth]

No, as I understand it, the capability is there.  What the GPSS does, among other things, is smooth out the curves.  So, for example, the autopilot would fly to the approach course heading and then make a correction, which results in the aircraft overflying the approach course and then having to come back and align itself.  The GPSS would calculate the pre-turn needed to get on the approach course without overflying it. 

If your autopilot is like mine, you can enable APPR, it will then ARM and fly the course you select with the heading bug to intercept the approach course.  At the approach course, it will then capture the approach course, but by that time the aircraft is overflying the approach course, so the autopilot makes corrections to get the aircraft back on.  At least I think that is how it works.  I have not used the autopilot for this yet, just read the literature for the GPSS's and the autopilot manual/instructions.

You can do the same thing yourself, by changing the heading bug to create the pre-turn, since the aircraft will follow the heading bug.  The problem is you have to pay attention to it when you have a gizzilion other things that want your attention at that moment. 

The GPSS can also fly DME arcs for you.

I will look into the EFIS. 

[jrjaks]

Quote: jlunseth

If your autopilot is like mine, you can enable APPR, it will then ARM and fly the course you select with the heading bug to intercept the approach course.