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Pitot Mast Mount Location

J

jpharrell

Well Known Member
Merry Christmas to all. I don't know if anyone is paying attention to this forum today but I am struggling with where to mount the pitot mast on my RV-7A wing and can use some advice. I am using a SafeAir1 mast with the Dynon heated pitot with AOA. There are three options:

1) Just outboard of the 10th rib. This is just a couple of inches beyond the third inspection access cover but only about 8 inches outboard of the tiedown ring. I have heard that in this location tiedown chains might hit the pitot tube. Not a good thing.

2) Just inboard of the 9th rib. This puts the pitot about 6 inches inboard of the tiedown ring so it should be less likely to contact tiedown chains but it is a little close to the aileron bellcrank pushrod and routing of the plumping (pitot, AOA, and heater in this case) will be more difficult. On the other hand this is very close to the pitot location shown in the Vans plans for the standard bent tube pitot.

3) Just inboard of the 11th rib. This is similar to Option 1 but moved out about 6 more inches which puts it about 17 inches outboard of the "standard" location and far enough away from the tiedown ring that it shouldn't interfere with the chains.

I know this pitot and mast have been used by many. Option 1 is my initial first choice but has anyone that installed it there actually had problems with the tiedown chains? I don't know if this is a serious issue or not. How about those that moved it inboard of the 9th rib? Any issues with routing around the pushrod?:confused:

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RV-7A
Empennage done
Wings in-work
www.johnsrv7a.wordpress.com
 
Inboard Mounting

Jason,

I've referred to your web site numerous times. Any issues with routing the pitot/AOA plumbing or heater wiring such that there no concerns with interference with the pushrod?

John
 
Mine is similar to Beav - the tie downs at pretty much every airport are wider apart than RV tie down rings. So I reasoned the pitot tube should be in-board of the tie down rings to avoid any possibility of inadvertently putting loads onto the pitot mast (especially when it is tied into the skin - don't want to pull on the mast and tear the skin).

Pete
RV-6A flying
RV-7 building
 
Assembly Order

As for the assembly order do I have this correct? After the the mast, tube and routing are all laid out and match drilled, disassemble everything until after the lower wing skins are riveted on, then reinstall the mast and buck the rivets through the access hole pretty much blind, then reinstall the pitot tube and reconnect wiring and plumbing again through the access hole? Is it possible to rivet the mast in as the skin is being riveted on?

John
 
There should be no interference issues with the aileron pushrod. The pitot/static tubes come out of the mast and immediately bend forward and go through an adel clamp on the spar web. This keeps them at least 1-2" from the push tube.

I haven't riveted my bottom skin on yet, so I can't confirm assembly order for sure, but it looks like your order would work fine if the primary push tube is removed. It looks like it would be in the way otherwise. I was planning on slipping the mast in place before clecoing the skin on then clecoing everything together before starting to rivet.
 
SafeAir Pitot Mast Install

Thanks for the feedback. Looking at the instructions for riveting the bottom skins it looks like it might be difficult to install the mast as the skin is being riveted because the flange of the mast overlaps the bottom of the spar and the skin lies on top. I assume someone else has tried this and knows for sure.

For now I'm planning to make sure I can install the pitot mast through the inspection hole after the skin is down flush just in case.

John Harrell - Building RV7A
Empennage completed
Wings in work
www.johnsrv7a.wordpress.com
 
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