[xblueh2o]

I am into the wings on my 8 build and sort of need to start thinking about a few things for down the road. I searched the forums and found some partial answers but here are the rest. Since the questions are in various disciplines I decided to ask here in the general discussion area instead of single questions in specific forums.

1. I want to do an Archer antenna in the tip. I plan on having an IFR capable machine but am not planning on doing a lot of IFR with this airplane. I do that all day long at work, I don't want to do it on my day off. My question is this. Do I need an antenna in each tip to cancel out signal blanking from the aircraft structure?

2. OAT probes. Can a probe from company A be used for the equipment of company B? Here's the deal. I have no clue what I want as far as avionics goes and I would hate to install a OAT probe from company A but then decide I want a panel from company B only to have to buy/install a new probe.

3. AP roll servos. I see in the 8 community where there are two schools of thought regarding wing or fuselage mounting of the roll servo. My question is this. Do all the servos have more or less the same dimensions so the mounting brackets will be the same? Again, I would hate to decide on a servo and buy it now from company A only to change my mind to company B and have to change the entire bracket set up.

4. AOA pitot tubes. I see there is some discussion regarding the ability of using an AOA pitot from company A feeding the system from company B. Here is my two part question. First part. Do all the various tubes have the same mounting style? Can I get just an AN-5812 style mount and rivet it to the wing and then stick anybodies pitot in it? Second part. Aside from a power lead for the heating element, an air line for the pitot and a second air line for the AOA portion is there anything else associated with an AOA pitot tube? I am trying to figure out what services I need to run in the wing.

Have at it VAF brain trust and thanks in advance for any help you can offer.

 

[PaigeHoffart]

I am into the wings on my 8 build and sort of need to start thinking about a few things for down the road. I searched the forums and found some partial answers but here are the rest. Since the questions are in various disciplines I decided to ask here in the general discussion area instead of single questions in specific forums.

1. I want to do an Archer antenna in the tip. I plan on having an IFR capable machine but am not planning on doing a lot of IFR with this airplane. I do that all day long at work, I don't want to do it on my day off. My question is this. Do I need an antenna in each tip to cancel out signal blanking from the aircraft structure?
No

2. OAT probes. Can a probe from company A be used for the equipment of company B? Here's the deal. I have no clue what I want as far as avionics goes and I would hate to install a OAT probe from company A but then decide I want a panel from company B only to have to buy/install a new probe.
No, but you should pre-wire

3. AP roll servos. I see in the 8 community where there are two schools of thought regarding wing or fuselage mounting of the roll servo. My question is this. Do all the servos have more or less the same dimensions so the mounting brackets will be the same? Again, I would hate to decide on a servo and buy it now from company A only to change my mind to company B and have to change the entire bracket set up.
Yes, put it in the fuselage (pre-wire)

4. AOA pitot tubes. I see there is some discussion regarding the ability of using an AOA pitot from company A feeding the system from company B. Here is my two part question. First part. Do all the various tubes have the same mounting style? Can I get just an AN-5812 style mount and rivet it to the wing and then stick anybodies pitot in it? Second part. Aside from a power lead for the heating element, an air line for the pitot and a second air line for the AOA portion is there anything else associated with an AOA pitot tube? I am trying to figure out what services I need to run in the wing.
Dynon requires a third lead for a warning light, not sure about other brands

Have at it VAF brain trust and thanks in advance for any help you can offer.

Paige
RV-8A

 

[cfiidon]

1. I want to do an Archer antenna in the tip. I plan on having an IFR capable machine but am not planning on doing a lot of IFR with this airplane. I do that all day long at work, I don't want to do it on my day off. My question is this. Do I need an antenna in each tip to cancel out signal blanking from the aircraft structure?

Warning: This may be TMI

Having an antenna in each wingtip and split to one radio would actually induce one or more "nulls". This is a function of phase shift of the received signal. This technique is used to make antennas directional on purpose, so not something you would want to do.

I have a set of Bob Archer antennas in the wingtips of my RV-8. The nav antenna in the right wingtip works great by all indications. Any antenna may suffer from blanking by the aircraft structure but this one appears no more susceptible to that than any other. Think about the geometry ... when you are in the air with a VOR on the ground there is not much "structure" in the way. Both the the signal transmitted and the antenna are horizontally polarized, so you get good reception.

As for the comm antenna, that can be another story. The problem is that comm signals are vertically polarized, and the wingtip antenna is limited in this respect. Installation procedure has it installed at a slant to optimize the vertical polarization, but it is limited. Therefore, at relatively low altitudes you might notice a signal degradation from a weak station (my home field ATIS) as a function of aircraft heading.

My belly antenna seems great on the ground talking to other aircraft on the ground. From the ground to an aircraft overhead not so good. For that I can switch to the wingtip antenna and radio. I haven't had the opportunity to try it with the belly antenna to a tower facility. I suspect in "some" situations I'll need to switch.

In my RV-8 with the sliding canopy, available antenna locations are a problem, but should not affect the ability to fly IFR as long as you are aware of the limitations.

Don

 

[DanH]

Decide on Company A or Company B

Roll servo; I dunno about two schools of thought. I'll bet everyone agrees that access to anything under the front seat means removing a lot of screws while kneeling on the wing and bruising your chest on the canopy sill.

 

[flion]

Dan is right. In the meantime, you can conduit for your wiring runs later, if you really must delay making up your mind. AP servos are not generally interchangable, so don't pre-install brackets and such until you have the ones you will use in hand.

As for the AOA question, I assume you are asking about using a Dynon mast with AFS system? AFS uses 1/8 tubing and they have adapters for connecting to a standard pitot/static system but you will need to fabricate adapters for the AOA ports. Again, I'd advise you to make up your mind before you get to that point on the wing and choose one or the other. Or both. My Dynon EFIS is a backup to the Garmin and I have the AOA Pro as a standalone but I suppose I could swap out the Gretz mast for a Dynon and gain backup AOA. But I'm not going to; at this point I've already made the decision and the wing plumbing is done.

 

[xblueh2o]

Great stuff. Thank you all for your input. That was exactly the kind of info I was looking for.

Decide on Company A or Company B

Yeah, I know. I was hoping to be able to simply smooth edges, dimple stuff and rivet for a while and not have to start making those kinds of decision quite this early in the build. Dang it.

 

[DaleB]

I was hoping to be able to simply smooth edges, dimple stuff and rivet for a while and not have to start making those kinds of decision quite this early in the build. Dang it.

So don't! Just build on and leave your options open. I won't make a decision on avionics until I am forced to do so, AND until I've had a chance to see them all and hopefully fly behind a few. There's no telling what will happen in the EFIS and GPS market by the time I'm ready to do my panel, but I'm betting things will be significantly different than they are now.

I went ahead and mounted a pitot mast on my left wing, because either Dynon, Garmin, AFS or others will work with an AN-5812 mast. I'll run wire for my Duckworks landing lights, but there's plenty of room in the conduit for whatever else I need to run later on - heated pitot, A/P servo, etc. Everyone tells me installing servos after the wing is built is not a big deal. I got the SafeAir1 pitot/static/AOA plumbing kit and installed the tubing in the wing, but left it un-cut and un-terminated so I can connect it to whatever I need to later on. The kit will work with anyone's EFIS or steam instruments, near as I can tell.

Heck, I can't even decide whether to go with someone else's strobe/position lights or roll my own, so I'll decide later on when I have to. It seems we're seeing new options in that market every few months, too. No sense buying something now when I won't need them for another couple of years.

 

[PaigeHoffart]

AP servos are not generally interchangable, so don't pre-install brackets and such until you have the ones you will use in hand.

If I'm not mistaken, Trutrak, GRT, Dynon, AFS, and Garmin all use the same mounting bolt pattern for their servos. I'm sure there are a couple of others that aren't physically compatible, but the ones listed above probably cover 90% of the market.

 

[flion]

If I'm not mistaken, Trutrak, GRT, Dynon, AFS, and Garmin all use the same mounting bolt pattern for their servos. I'm sure there are a couple of others that aren't physically compatible, but the ones listed above probably cover 90% of the market.

If mounting bolt pattern were all there were to it, you would be correct. Look at the dimensions for the various TT servos; they might fit the same mounting bracket but otherwise all bets are off. Still, you have a point. If there are no interferences behind the bracket and plenty of room, then you should be able to use any of the offerings without too much trouble. So much easier, though, to do these installations before you close up the airframe.