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Upgrading Terra NAV & SL-40 to SL-30

B

Bob Axsom

Well Known Member
I just like the old ground based system that will be terminated in 2020 so don't slam the glass that will be out of date before then at me. I have been flying single nav receiver & indicator approaches with the RV-6A fo 6 years and that erratic on again off again Terra electronic indicator has made me sweat bullets and improvise with the SL-60 tied to a MAP 360 for the last time. It is not much cheaper than a 430 GPS system but I like single function dedicated instruments.

Bob Axsom
 
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Caution on SL-30 & Indicator purchase from ACS

I went to Aircraft Spruce's website and used there online catalog to order a Garmin SL-30 and the compatible indicator with glideslope. The GI 106A listed is not the one recommended by Garmin and there is one observed incompatibility. Probably not serious but still for $5,000+ you expect the units to be completely compatible. The SL-30 has a back course annunciator output and no VLOC annunciator output. The identified indicator has a VLOC annunciator and no Back Course annunciator. All other pinouts appear compatible and I will probably end up leaving the input inactive as a work around but I have sent a message to ACS and I will work this further. There was no documentation with the indicator but I was able to get the Mid-Continent Instruments manual for the MD200-202/203/206/207 as well as the MD200-302/303/306/307 and I checked the information at the Garmin site - it appears to be a ACS error.

Bob Axsom
 
Answer from ACS

The instrument works well with the SL-30 but the back course annunciator is not included in the indicator. I does have a VLOC annunciator that is used in the GPS vertical guidance world but no straight NAV BC annunciator. We agreed to make a switch of the GI 106A (aka MD200-206) for a MD200-306 (about $100 cheaper with the BC annunciator).

Bob Axsom
 
Here you go for the SL-30

sl30com.jpg

sl30nav.jpg
 
First Mistake

Somewhat casually, I ordered a Comant CI-1125VOR/LOC Quadraplexer so that I could retain my old Terra NAV receiver and my new SL-30. As I have only three more wires to connect to aircraft power and dimmer I started thinking about the RF input to the SL-30. It has only one RF input for the NAV function so the signal processing for GS and VOR/LOC is split internally. Warnings started going off in my mind. I talked to the technical specialist at Garmin AT about the problem. He said the Quadraplexer will probably not work with the SL-30 He said what is needed is the Garmin 013-00112-00 Splitter with one output feeding the existing splitter for the Terra Nav and the other output feeding the SL-30 Nav coax connector. Garmin does not list this part on their website and Aircraft Spruce couldn't find any such number. Since it is Friday evening and I need to fly to Mitchell, South Dakota next Saturday (7-24-10) for the AirVenture Cup Race I took a shot at a Google search and found the part at Avionics Mall. Ordered with next day air shipping and hope they have one in stock.

Bob Axsom
 
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More on the Garmin Splitter

The website said they do have one in stock and it also provided this information:

Garmin 013-00112-00 Nav Splitter for Garmin SL-30
$130.00
For use with one Nav antenna when feeding a SL-30 and another nav receiver. Unlike a Nav diplexer, this splitter will not degrade the Glide Slope signal needed for the SL-30.​

Things look hopeful.

Bob Axsom
 
Mistake #2

Mistake #2. Going in on this project I assumed that the SL-30 and SL 40 mounting configurations were identical and maybe two units bought today would be but mine are not. Today I completed the installation of the NAV cable and the NAV coax and started reinstalling hardware. When I got to the SL-30 it went in the tray (tube) nicely and all appeared well but it would not fully engage the tray/connectors, etc. Careful examination revealed that the latching mechanism is different. This is probably a generic design change made some time in the past decade. The SL-30 mechanism has a longer stroke and the machined part is less beefy but when the mechanism is moved to the fully inserted position the position of the fwd surface of the rear tang appears to be in the same plane as the same surface of the same element on the SL-40. There is a possibility that some careful positioning and perhaps a minor modification would make this work but my plan tomorrow is to go through the agonizing tray removal process and install the tray that came with the SL-30. By the way, the SL-40 will not latch in the SL-30 tray either. Even though the connector layouts appear identical, the full tray change out should be anticipated as a worst case situation for anyone else contemplating this change. I am planning to call Garmin AT Monday morning but I am supposed to fly to Mitchell, SD for the AirVenture Cup Race on Saturday so I'm running a little short of time.

Bob Axsom
 
Bob, You needed an MD-200 indicator which is actually cheaper that the GI (albeit almost identical) for the SL-30. Indeed the most of the -40's will work in the -30 tray's, but not the other way around.

Anyway, next time I'll save you some money, time, phone calls and posts! :)

Cheers,
Stein
 
Ah yes, but the education is priceless

It took all day, except for a trip to the dentist that didn't work out, but I got the SL-40 tray out at 8:30 pm last night. When I get the SL-30 tray in I should be on the home stretch - all of the actual wiring there is done. My plan is to fly to Mitchell, SD on Saturday for the AirVenture Cup race on Sunday so time is starting to get very tight. I have the Garmin 013-00112-00 splitter coming from Aerotronics (shipping today - next day air - per phone conversation) and coax cable and connectors coming from Aircraft Spruce (shipped yesterday - 2nd day air) for the splitter to Terra NAV diplexer link that I am dependent on.

I seem to be undergoing a test of some sort during this upgrade. Beside my faulty Garmin/Apollo mechanical design assumptions, I am coping with a Japanese beetle infestation of our rose garden, flat tire on wife's car, front tooth broken in half, grass growing extra fast requiring extra cutting and very high temperature. On a positive note, I have sweated off 5 pounds so far. I have fall-back plans that I can switch to to enable me to make it to Mitchell on Saturday unless the weather shuts me out. For example, after setting in the dentists chair for an hour and 15 minutes today I got up and told them I have to get my plane ready for a race this weekend and I have no more time - I don't smile all that much anyway so half of a missing upper front tooth shouldn't be noticed too much. As a last resort I will close the plane up and fly there with the SL-60 and the Terra NAV but I don't expect that to be necessary. Washing is optional (the plane) and waxing near impossible at this stage of getting ready to race - bugs from the West Texas 100 air race probably don't create that much drag.

My wife says I should have waited until after the AirVenture Cup race to upgrade the NAV system but I know I do my best work under pressure and if I didn't have this deadline it would be Christmas before I got it in.

Thanks for the suggestion Stein but this experience for this very old ex-USAF radio mechanic is priceless. If I were ever to build another airplane (it ain't happenin' folks) I would use fewer mounting screws in my radio racks.

Bob Axsom
 
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Things are looking up

I got the SL-30 rack installed this afternoon with all four connectors and installed the radio. Went together very nicely. A call to Brandy at Aerotronics confirmed that the splitter was shipped "next day air" today and the Coax hardware from Aircraft Spruce shows up on UPS tracking as scheduled for delivery tomorrow. May get to wash the plane yet.

Bob Axsom
 
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Bob,

Avionics, car repair, yard work...and a trip to the dentist...yikes! :eek:

When I see you in Mitchell, the beer is definitely on me! And I'm bringing some cleaning gear and quick-detailer wax...happy to help you shine up Bluebird for the race...you've been workin' hard, shipmate!

Good luck with buttoning up, and c-ya there!

Oh yeah, better be careful, we may have to give you a new call sign, "Chip"! :D

Cheers,
Bob
 
I Know!

It surely is a test to see if I'm worthy. If I get through this well I'm thinking my reward will be a good finish in the AVC race.

The weather looks good by the way.

Oh, and Chip just will not get it - half of the tooth is gone.

See you there.

Bob Axsom
 
Panel configuration

NAVCOMMOD72010008.jpg


Still have a lot of reassembly to do, plus labeling wire bundle tying etc. but this is the final panel configuration.

Bob Axsom
 
Another Little Surprise

As I was reinstalling my Carb heat cable I realized my hand was wet. It turns out my engine control cable shroud had worn a hole in the fuel pressure line directly above the exhaust pipe. Now I'm glad I had to take out the carb heat cable and relocate it to free up panel space.

Bob Axsom
 
Whew!

Bob Axsom said:
engine control cable shroud had worn a hole in the fuel pressure line directly above the exhaust pipe.
Click to expand...

That was a good find. Probably saved you from a very bad day! Glad you caught it when you did.

Thanks for the posts.
 
Installation complete and ground check is good

Installation complete and ground check is good. Bothe the SL-30 and the Terra NAV systems are functioning properly. The fuel pressure line repair components are at home now so it looks like flight test will be conducted tomorrow.

I don't think it will take too long to put everything back together maybe I can wash it tomorrow as well for the AirVenture Cup Race on Sunday - but am I tired - maybe sleep instead.

Bob Axsom
 
Replaced the fuel pressure line

IMG_4283.jpg


This is the damaged section cut from the leaking fuel pressure line (direct to gauge in cockpit - no transducer).

Bob Axsom
 
Flight Experience Indicates need for Change

I have been using the GPS MAP 360 display in conjunction with the SL-60 since I built the plane and it had become the NAV instrument I looked at most so in the modification of the panel I left it right where it was - under the VOR/LOC/GS indicator. As described earlier I found a way to work the old Terra VOR/LOC/GS into the panel on the right side of the radio stack for the occasional cross check on approach. I have been using the #2 com for several years since the com in the SL-60 got a few complaints from the controllers. Every thing worked but it is not efficient.

Switching back and forth between the visibility of com frequencies and nav frequencies on the SL-30 is not something I like doing during an IFR approach and using the same knob that is used to change frequencies to change OBS radials is also something I don't want to deal with procedurally when flying IFR. I am going back to #1 com for communication (SL-60) and the SL-30 will be dedicated to NAV except in emergency. I may have to work with the RF part of com #1 in the future but I believe it is good enough for now.

The big change is the #2 NAV indicator is going to have to be moved over to the left side of the radio stack directly under #1 and the GPS MAP360 is going to have to be moved to the right side of the radio stack. You wouldn't think glancing to the other side to monitor crossing radials for a step down on an approach would be that inefficient but it is.

I think this will get me back into my comfort zone using the panel.

Bob Axsom
 
No

Such long range plans controlled by government have a track record of delayed implementation - still I hope to be around to see what happens as a curiosity.

I suspect the the glass panel bought today will be a distant memory by 2020. The software configuration control will not be maintained by the developers, patches in the op sys code will not be implemented consistently, application code will vary from unit to unit and data bases will be obsolete, memory addresses will have bit flips, interface protocols and formats will not be consistent with the latest peripheral units, etc. Maintenance will be impossible.

Bob Axsom
 
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