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Thread: Selection of Nav/Comm, Comm and Audio

  1. #1

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    Selection of Nav/Comm, Comm and Audio

    I am doing the selection of avionics for a new design. One combination I have seen has all of these 3 components: Garmin SL30, SL40 and GMA340. My question is: do we really need all of them? It seems SL30 nav/comm has some overlap with SL40 comm in terms of functions, and GMA340 audio is pretty powerful. Can the combination of SL30 and GMA340 enough to cover and get rid of SL40?

  2. #2

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    So what type of flying do you intend to do. In my Pitts Special, the SL40 would be all that I need. It can handle the Comm and intercom. Don't need a VOR, LOC, or GS.

    If you intend to fly approaches, then I will suggest one of the moving map, all in one boxes like the GNS-430 and its peers gives you all of the nav and comm that you need and then you can add something like a SL40 for a second comm. With only two boxes you do not need a talented and expensive audio panel like the GMA-340.

    All of the current generation of boxes are light weight and draw only a little power. You did not ask, but you only need a 70W alternator if you have multiple landing and recognition lights. These days the avionics and the LED interior lighting has drastically reduced the electrical system power requirements.

    So the question is, what kind of flying are you going to do.

    Best of luck,

    Wes
    N78PS

  3. #3

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    Quote Originally Posted by wantobe View Post
    I am doing the selection of avionics for a new design. One combination I have seen has all of these 3 components: Garmin SL30, SL40 and GMA340. My question is: do we really need all of them? It seems SL30 nav/comm has some overlap with SL40 comm in terms of functions, and GMA340 audio is pretty powerful. Can the combination of SL30 and GMA340 enough to cover and get rid of SL40?
    You are asking the question backwards......

    What requirements does the gear need to meet?

    VFR/IFR?
    Dual Comm?
    Dual Nav?
    How many inputs do you need on the audio panel?
    How many people will use the intercom?

    For example, I fly IFR, so dual comm is a requirement for me. The SL30 allows you to monitor a second channel, but if the SL30 dies, I wanted a second comm available. I also carry a hand held as a third source of comm.

    I also have an IFR rated GPS (GTN650). This provides my main comm, along with GPS and VOR NAV. So all I added was a SL40 to meet the requiremetns for a second COMM. I don't need a second VOR NAV. I do have redundant (non-TSO certified) GPS devices in the panel if the GPS fails.

    You might want to look at Icom or ATS products. An AFS EFIS with the ATS remote comm and transponder will be a nice solution for folks with limited panel space. But again, it's hard to recommend since we don't know if this is for an experimental or spam can.

    The audio panel is more of a personal choice decision. The GMA340 has been the industry standard for years. However, there are newer products on the market. For example, if you have a tight budget PS Engineering has a combination audio panel and COMM unit for experimentals. I prefer the PSE 8000BT, but you may not need all the features of this unit. I also prefer how PSE squelches the voice over the way Garmin does it on the GMA340. I recommend getting individual mic squelching.

    The options are quite plentiful when you consider the combinations of vendors and models. If you define your requirements, then it's pretty straight forward to limit the choices to only those that meet or exceed your defined requirements. Seems like common sense, but it's quite common for folks to pick avoinics becuase that is what their buddy installed, without understanding if both aircraft are flying the same mission.
    --
    Bob Leffler
    RV-10 Flying
    www.mykitlog.com/rleffler

  4. #4

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    VFR/IFR?
    Ans: IFR

    Dual Comm?
    Ans: Does that mean both pilots can talk at the same time with different people? I need one channel talking, the other one standby, but not both pilots talking.

    Dual Nav?
    Ans: I would like to have a GPS and a VOR at the same time. Is this dual nav?

    How many inputs do you need on the audio panel?
    Ans: I do not understand this question. I do not plan to have music input.

    How many people will use the intercom?
    Ans: Just the pilot and a copilot in a side-by-side two seater.

    Thanks for the info!

  5. #5

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    Quote Originally Posted by wantobe View Post
    VFR/IFR?
    Ans: IFR
    Great, this will drive quite a few of the comments. There still is a fair amount of variabiliy due to the fact that each of us have different levels of risk we are willing to take on versus how much budget we have to work with.

    Quote Originally Posted by wantobe View Post
    Dual Comm?
    Ans: Does that mean both pilots can talk at the same time with different people? I need one channel talking, the other one standby, but not both pilots talking.
    That would be a side benefit, but in my opinion not the primary driver. Let's say you have one Comm and your are in IMC. The Comm fails, what are you going to do? Fly NORDO or wish you had a second Comm in the aircraft?

    Quote Originally Posted by wantobe View Post
    Dual Nav?
    Ans: I would like to have a GPS and a VOR at the same time. Is this dual nav?
    Technically yes, but that wasn't the point I was driving for. Do you need dual VOR Navs? Most people these days that have IFR certified GPS, the answer is probably no. But there are folks that still prefer to have two Navs on board. Many VOR approaches require them, but if you have a certified GPS on board you could use a GPS overlay instead. In my aircraft, my preference was that I have only one NAV for VOR/ILS. Most of these approaches are starting to go away which is why I just used a SL40 as Comm back up to my GTN650.

    When shopping for a GPS, you need to take a look at the variances. The GTN650 is the best choice in my opinion, but it isn't cheap. Things you may want to consider understanding better between the GTN650 and the GNS430W are alternate airport NAV requirements (430 requires other NAV sources). the 650 supports airways (this is huge if you are in a congested area or fly through one. I got rerouted once and it took me 5 minutes to look up all the intersections and input them into the 430), and my favorite feature is rubber banding (making quick changes via the touch screen). This is probably the hardest decision to make due to the cost. Since the 430 may be near end of life, I think the 650 is a better investment and well help resale value.

    Quote Originally Posted by wantobe View Post
    How many inputs do you need on the audio panel?
    Ans: I do not understand this question. I do not plan to have music input.
    EFIS, EFIS2, Comm1, Comm2, Nav1, Nav2, AOA, CO detector, ELT, ADSB, etc, etc may each want an input to the audio panel. You didn't mention if you are going with glass or not. A pair of EFIS will only require one EFIS. Since you are IFR, I would recommend a pair of EFIS from on vendor (AFS, GRT, or GARMIN) and a third smaller EFIS (Trutrak Gemini or Dynon D6) as a tie breaker. What would you do if you have two EFIS screens and the data doesn't match while you're in IMC. What would you do? You need a tie breaker from a different manufacturer. With three data sources onboard, the go with the data from the two that match. The reason why you want the third to protect from software bugs. Although quite rare, if a software glitch should happen, it could take both EFIS offline for a period of time. Obviously if the third unit was from a different vendor, it wouldn't be expose to the same issue.


    Quote Originally Posted by wantobe View Post
    How many people will use the intercom?
    Ans: Just the pilot and a copilot in a side-by-side two seater.

    Thanks for the info!
    This gives you a little more flexibility in the choices. However, since you are IFR and most likely have more avionics on board, I would suggest sticking with an auidio panel. Then it's just a decision of how many bells and whistles you need.

    I know this is probably like drinking out of a firehose at the moment, but since you plan to fly IFR, you really need to think about the process and what action you would take if any device should fail. Once you understand the failure mode, you can determine how important each piece of gear is and whether or not your're willing to invest in a piece of gear to mitigate the risk.

    If you are planning for an auto-pilot, which I would also highly recommend for flying IFR. I would recommend an AP head that is external to the EFIS. If the AP head is internal to the EFIS and the EFIS dies, you are now hand flying the aircraft in IMC. Do you really want this additional workload when things are going south fast? With an external AP head like (Trutrak or Trio) if your EFIS dies, you hit a button and the AP will keep you level. This buys you some think time to react to the situation.

    I sense that this may be pretty new to you. My recommendation would be to call an avionics shop to assist you with selection and installation. I can personally recommend Jason Smith (Aerotronics) or Stein and Jed (SteinAir). All of them provide great service. I'm sure that there are other great shops, but I have personal experience with these gentlemen.

    Fell free to email or pm me with additional questions.

    bob
    --
    Bob Leffler
    RV-10 Flying
    www.mykitlog.com/rleffler

  6. #6

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    Based on the original poster's questions, I would ask
    A) Do you now have an instrument rating?
    B) What gear have you flown IFR with?

    You can spend more $$ on electronics than on your airframe these days. If you leave space in the panel for nice boxes, you can start with just an audio panel and a comm radio and add later as your preferences for gear evolve.

    Best of luck,

    Wes
    N78PS

  7. #7
    Cary's Avatar
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    Having lost nav capability in one navcom in the clouds, I cannot imagine going into the clouds now without two of them, both working. It's a comfort level thing, even if it's not technically required. It's also really helpful in order to perform the 30 day check under 91.171, if there's no other approved way of doing it.

    The questions being asked suggest that the OP doesn't yet have an IR. I think there's a tendency to do too much guesswork before knowing what's necessary or desirable to fly "in the system", so before laying down a big chunk of bucks, I'd suggest completing the IR training, and then find an avionics shop that won't try to sell the unnecessary fluff but will sell the stuff that's necessary for now and into the reasonable future.

    I also cannot imagine flying IFR without an audio panel. My first airplane did not have one, and "switching" between one radio or the other meant turning one up and the other down. Sure, that works, but it's pretty awkward. Having one button, or one switch, to go from one radio to the other is a big help when things are busy. And being able to push a button or flip a switch to bring up the audio of other avionics is a lot handier than adjusting the volume individually.

    So just like figuring out the mission before buying an airplane, figure out the avionics mission before buying avionics. I'll use my airplane as an example, a much modified 63 P172D. I have no hesitancy in flying it in "soft" IFR, but like any other low powered non-FIKI single, it shouldn't be flown in difficult IMC. Today's system, with the approaches being rapidly changed to GPS, pretty much demands the capability of doing GPS approaches, along with ILS and VOR. So my newly installed 430W (May) fills that bill, although that admittedly has a much more difficult learning curve than the new GTN 650. As back-up, I retained one 760 channel navcom. For an audio panel, I chose a PSE 6000B, which has all the bells and whistles I need including a superb intercom and marker beacon receiver, allows the front seaters to use the com radios separately if desired, and allows music to be inputted for longer, less trafficked legs of a cross country. I kept my ADF which works well, figuring there are still NDB approaches here and there, and they are necessary for IFR in Canada, should I decide to go there.

    But what I did not consider at all was having two 430Ws, or even a second panel mounted GPS, or a much more elaborate audio panel. Redundancy is nice, but pretty soon it would be possible to double the cost of my airplane without doubling its value or utility.

    One other relatively minor thought: Install an avionics master. It's so much handier, and more protective of avionics, than having to turn each item on after starting the engine and off before stopping it.

    My 2 cents.

    Cary
    "I have slipped the surly bonds of earth...,
    put out my hand and touched the face of God." J.G. Magee

  8. #8

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    Thanks for the nice cents from bob, Wes and Cary. I do not have IFR and will not have time to obtain it before finishing this airplane. I will do it with my best knowledge now and change it later. Although drinking out of a fire hose, I learn a lot from the replies. Thanks buddy.

  9. #9
    steveinindy's Avatar
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    will not have time to obtain it before finishing this airplane.
    No offense, but it always scares me a little when I see someone imply that their build is on a "schedule". That might not be what you're implying but just remember that there is always an option to let the aircraft sit while you complete your training. There's also the option to design the "slots" for the installation of further systems into the aircraft at a later date.

    Fly safe my friend.
    Unfortunately in science what you believe is irrelevant.

    "I'm an old-fashioned Southern Gentleman. Which means I can be a cast-iron son-of-a-***** when I want to be."- Robert A. Heinlein.



  10. #10

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    My builds are always on schedule. I am 90% complete with 90% to go.

    These days, waiting to buy avionics until you are ready to use them is the way to go. The technology improves every year. A couple of years ago touch screens and Blue-Tooth in the cockpit was still a dream. Today we have both. So time is on your side, even if you plan to buy one generation old gear. I will suggest that all of the guys who are upgrading to the latest Garmin, Avidyne, etc gear will be selling their old boxes at half price. And the last generation of gear is not too shabby compared to even 10 years ago. I have friends who laugh about shooting approaches in a 727 with King Silver Crown gear (KX-175B etc). Now we can fly GPS WAAS coupled to the autopilot in a C-172.

    So work on the airplane first and think about your instrument rating as you get time and $$. Leave space in the panel for boxes using today's specs. When your airplane flys there will be avionics technology to fly with that you can only dream about today. Time is on your side.

    Best of luck,

    Wes
    N78PS

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