AHRS Bracket Install

Greetings All,

I am installing a Van's VA-259 AHRS Bracket in my RV-7A and adapted it for mounting my Garmin GSU25 ADAHRS unit. The installation instructions (OP-47) call for dimpling all of the holes in the bulkheads, Bellcrank rib and aft bottom skin. With all the skins riveted together it makes dimpling the F-778 Aft Bottom Skin difficult. So, in lieu of dimpling the F-778 Aft Bottom Skin, I am thinking about using LP4-3 pulled rivets in the bottom skin and the AHRS Bracket bottom flange. Cosmetics aside and the potential parasitic drag , would the LP4-3s be an acceptable alternative to the AN426AD3-3.5 as called out in the install instructions? If anyone has some suggestions on how to go about dimpling the aft bottom skin, I would like to hear those as well.

Pop dimple tool

Can you use the pulled pin dimple tool?
Works pretty good on skins.

My personal opinion is you are better off keeping the GSU25 up front behind the panel rather than mounting it back by the pitch servo.

WireJock - yeah I have a set of those dimple dies but I tend to use few too many nails/pull pins. Must be squeezing harder than necessary. I may give it a go, not squeeze quit as hard and use NAS1097 rivets which have a shallower head.

Walt - thanks for the input. Curious to know your reservation as it would seem ok if the GRS77 AHRS was mounted there. Does the servo generate enough interference to affect the GSU25?

Wonder what the G3Xperts take is on this as well.

Thanks

Hi Dan,

Yes, as you and I discussed, our RV-7A started out with a G900X with a GRS77 AHRS mounted on this OP-47 bracket.

When we swapped out the G900X system for a G3X Touch system just before Oshkosh last year, we removed the GRS77 and re-used this AHRS bracket to mount two GSU 25 ADAHRS.

Walt is a sharp fellow and may know something that we don't, but so far this mounting bracket/location has worked out great for us.

Thanks,
Steve

Missing something?

I have to wonder if I am in fact missing something...

I have had my GSU 25 installed on the rear of my GDU for 25 hours without so much of a hiccup. When I say installed to it, I mean screwed to the rear of the GDU...it just seems so convenient for everything is there any advantage moving it off site?

G3Xpert/Steve - thanks for confirming our discussion. I was curious if others had traveled this road with mounting the GSU25 on the AHRS Bracket as well.
Yes, I have the utmost respect for Walt's comments and suggestions and have found many of his posts quite helpful over the years. Once again I thank Walt for his input.

Icarus - Thanks for the reply. Glad to hear you haven't experienced any issues with mounting the GSU25 to the GDU. I thought about mounting my GSU25 there as well, but in reviewing the GSU25 mounting requirements, it seems to indicate that mounting the GSU25 to the back of the GDU 4xx display is not generally recommended due to instrument panel flexing. With that, Since I had the bracket I figured I would try mounting the GSU25 there. Having one less item up front should reduce remote component crowding and give me more room for installing and servicing other forward mounted components and the associated wiring.

snoopyflys said:

Icarus - Thanks for the reply. Glad to hear you haven't experienced any issues with mounting the GSU25 to the GDU. I thought about mounting my GSU25 there as well, but in reviewing the GSU25 mounting requirements, it seems to indicate that mounting the GSU25 to the back of the GDU 4xx display is not generally recommended due to instrument panel flexing. With that, Since I had the bracket I figured I would try mounting the GSU25 there. Having one less item up front should reduce remote component crowding and give me more room for installing and servicing other forward mounted components and the associated wiring.

Click to expand...

Good to know I didn't miss something in the manual. If my -4s instrument panel flexes that much I tend to think I have worse problems than an erroneous reading!

My comment about mounting up front is strictly from a installation/wiring/maint/convenience perspective.

You'll have to run your pitot, AOA, power and other data to the back. Also for your 2 yr IFR cert I/you generally need access to the AHRS for hook up which means removing seats, baggage walls etc. just to gain access.

When I install equipment one of my primary objectives is ease of maintenance.