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When is the right time to buy avionics

PaulvS

Well Known Member
Is there a "right" time to buy EFIS/EMS components, radios, GPS, servos, sensors etc. for a new build?

Buy too early... and there is a chance that something new will appear on the market. And a good portion of the warranty period will be used up before the first flight.

Buying late on the other hand makes it more difficult to complete equipment trays/instrument panel, wiring looms and runs while access is still good. There is also the risk of unexpected delay due to back-ordered items and rising costs, with the current pandemic supply chain issues.

If you've done this before, what do you recommend? Previously "best practice" would've been to buy as late as possible, but I'm not sure that applies anymore.
 
Watching

I have the same concerns as i wrap up the wings ,

When i first started my build I always thought avionics last because of the constant evolving technology in avionics , ive also have the cash ready for a deal for someone who needs to sell a purchased package , ive seen some killer deals

Myself I’m going to try to anticipate a 6 month window on avionics ,
 
SNIP

Buying late on the other hand makes it more difficult to complete equipment trays/instrument panel, wiring looms and runs while access is still good. There is also the risk of unexpected delay due to back-ordered items and rising costs, with the current pandemic supply chain issues.

If “access” is driving you process, I suggest another approach.

For most of the airframe wiring is independent of avionics. This is stuff like power, grounds, lights, headphone jacks and such.

For the avionics, the one thing I suggest you do now is decide on your brand. From that you can do the simple stuff like pitot selection and mount, ADAHRS mount, Autopilot servo mounts. I only build with Dynon so for me this is simple. If you can’t decide what you want, at least buy and install the nice ADAHRS mount kit from Van’s - cheap at twice the cost.

From this you can run the few avionics specific wire runs (network connections for ADHARS modules, remote boxes like ADS-B receivers and such). You can also run the antenna leads as these are independent on your avionics selection.

When it comes time to do the big buy, then take the time to design your panel so it can be assembled on the bench. This translates to all panel interconnections being done (radios to audio panel and such). Connections to the rest of the plane is then via D connectors (non power stuff) and one large pin Molex for power and ground.

It is very helpful if you divide your panel into “what stays in the plane” and “what comes out”. For panels with an apron or side wings (e.g. RV-10 and RV-8) this simple. Stuff like master switches, landing/nav lights, ignitions switches, non-panel breakers, cabin heat cables go on the apron or wings.

The photos are of an RV-10 and RV-8 panel that follows this approach. Note the breakers on the removable part of the panel are for the loads only on the panel. These get power and ground via a large pin Molex.

Note - the RV-10 panel has been modified three times since this photo was taken (and I suspect you will modify yours as well - plan on it).

The point being this will, by approach, mean that when it comes time to troubleshoot, modify or upgrade the panel you can have it out of the plane and on the bench in ~15 minutes. This meets the design objective of never being on your back with your head under the panel.

Carl

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Carl offers a lot of great ideas on this.

"Is there a "right" time to buy"
"Previously "best practice" would've been to buy as late as possible, but I'm not sure that applies anymore."


As far as pricing, back orders, new product introductions, etc. are concerned - they will be there WHENEVER you decide to purchase your avionics. As Carl intimates, build in mind that sometime in the future, you will probably be wanting to update or change things in your panel. Build the physical structure to easily handle that.

As for timing, you have the advantage of not doing this 5 or 10 years ago. Today huge amounts of information is easily available that earlier builders couldn't access till actually receiving the units and manuals. Being able to download your choice of installation manuals to the various brands is a great advantage, you can practically pre-plan and pre-build complete installations (wiring, module dimensions & layout etc.) even before you have the units.

So, maybe the old "best practices" really don't apply as much anymore.

& as far as getting the latest & greatest out there - wait 5 minutes, upgrades will be ever in your future.
 
Thanks for the suggestions, particularly from Carl and Ralph, there are some really good points you make.

I think there are a couple of things driving the process:
  • Access and fitting.
  • Committing before purchasing and then running into availability problems when trying to order.

For access and fitting, I've seen how some builders use mock equipment along with a lot of careful planning to do 95% of the work before buying the actual "boxes". The tolerances can be tight for some of the display cut outs in the panel but the main vendors have good manuals with detailed dimensions and diagrams which show connections and mounting points.

The availability problem is a bit harder to deal with. I noticed that e.g. even simple items like Honeywell toggle switches are on backorder until October with a local supplier. There are ways of dealing with a relatively common standard type item like this, but I'm a bit concerned about fabricating the instrument panel including painting and labelling and then finding that the PFD is not available to order when ready for it at the "end".
 
I found the best option was to get a plan together and settle on a manufacturer relatively early, then buy some avionics trays from Stein Air so that you at least have something to get the metalworking side of things complete, knowing that the avionics themselves will likely change before you are done. I left the avionics install until after the engine, paint etc was complete, apart from setting up the mechanical fixings for the avionics. Avionics trays are particularly cheap in the scheme of things.

Tom
RV-7, G3X, IFR
 
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