RV-3B Dave's in Colorado

[jliltd]

David,

In my RV-3 any toggle switch along the bottom of the panel was primed for being inadvertently bumped while moving my hands around the cockpit. I had similar panel control placement such as yours where items in the center and right side, such as your com radio, iPad and clock, needed to be grasped, flipped or touched. While reaching around I was always unintentionally knocking toggle switches up or down. It was even more prevalent if I swapped hands on the stick to free up my right hand to twizzle or touch something on the panel, such as your iPad location. The hand coming off the stick is already low and near the bottom edge of the panel so after releasing the stick the upward movement of the hand was right at the bottom toggle location, as was the action of the other hand reaching to grab the stick. Remember the RV-3B is a personal rocket with the flight control location low and forward compared to the Cessna. It also does not have the panel setback or vertical spacing of Cessnas or even other RV models. You might want to mock up the stick in place and move it around while changing hands on the controls and then reaching towards the panel with the free hand. You might also be surprised how short the RV-3 control stick is and how close it crosses under the panel with little clearance. Mine only had about 1/8" clearance below the stock panel. You might have to cut down the stick even further for the switch panel.

Point being there is nothing fundamentally wrong with your current layout but focus on hand movement ergonomics and selector switch locations. You might want to run a towel-bar type switch bump guard below and maybe even above the switches. Think twin-engine mag switch guards. There are also individual switch bump guards that can be installed from the likes of Perehelion Designs.

I can't tell you how many times I bumped a switch while moving my hands around the RV3 cockpit. The master was the worst one to bump off. Thankfully I had a keyed ignition switch so never unintentionally switched off the mags. I would prefer ignition/mag switches be set off in a non-operating area since they are used during start and run-up and then mentally tucked away. Why not physically tuck them away too? Maybe locate them to a less valuable non-activity real estate area in lieu of, or in addition to a bump guard.

I would like to see some responses from other RV3 pilots with decent operational experience with their panel ergonomics and switches. All this could very well be "just me". I haven't had this type of issue in other model RV's. I only have an hour in an RV-4 which might have just as tight cockpit as the 3.

In your layout switches 2 thru 4 (from L to R) are fairly critical and #'s 3 & 4 right by the centered flight control stick are ripe for bumping. Especially with the comm radio controls in the same area. Have you considered moving the comm radio control head to above the Dynon EFIS (I am assuming something like a TY-91 or Dynon remote VHF com). Puts it where easily accessible by the left hand and in good view of the pilot. The EFIS and comm radio will probably get the most action in flight, followed by the right-hand accessed iPad.

I love keeping up with your project here. It's going to be an amazing bird.

[David Paule]

Thanks for these comments.

I have sat in the cockpit a number of times with the switch panel (and the avionics shelf, which is part of the same fiberglass part) installed. I need to pay attention to my legs getting in to miss the switch panel but not much all in all; it's not a big deal. Getting out, there is no issue.

Once in the cockpit there's plenty of room for me. The switches are inset about 3/4" from the panel, forward (that is, airplane-forward, and away from me) of the panel and there's plenty of clearance, about 1.5", between it and the stick. That's shown a couple of posts earlier. While accidentally moving something might be an issue, I don't think it will be - especially with the current switch panel layout, which moved the push-button switch closer to the center. I'm also changing switches for better feel, but that's a separate issue.

I am about 5' 7" and have relatively short arms. When I buy long-sleeved shirts they are always too long in the arms and often either just right or a bit short in overall length. For me, it's enough of a reach to the switches that I'm not worried about accidentally bumping one.

The RV-3 as designed has an indented seat, allowing more height for a tall person like Van. I filled that in and still need a cushion.

Please keep the cockpit comments coming. Cockpit layout is a new science to me and I want your comments and insight. It's curious.... I can tell good design from bad but have little idea how to get there except by trying out concepts.

Dave

[David Paule]

One of the things in the cockpit on the left side that affects other things is the trim handle. I need to know where it goes. Since the trim cable is made, the handle is at the forward end and the trim tab is at the aft end. But to get to the aft end, there’s this little problem - how to carry the cable around the horizontal stabilizer?

I asked VAF readers to let me know how they did it. Since many RV-3s seem to have electric trim, the information is a bit sparse. I got three replies and drew them on a section of Drawing 26 from the plans.

The red path was used by two builders. It fits under the empennage fairing, but requires somewhat of a deep dive into the stabilizer. On my plane, the cable will interfere with the ADAHRS and its mount which is in the tailcone just ahead of that bulkhead. It’s too bad because this is simple and fairly straight-forward.

The blue path was used by one builder. It’s a nice clean direct path except that it requires a hole in the forward spar. I’m reluctant to do that.

I chose the green path, even though I needed to figure out how to get the cable through the aft deck (the red and blue paths bypass it).





With a hole through the aft deck and a hole through the horizontal stabilizer root rib, the trim cable is in place. The lengthwise positioning of the cable is not correct, it’s about 7” too far, but that’s been adjusted subsequent. The holes are too small and there are a few more minor tweaks to do. But this is the general path.





It was sufficient to let me find out where the forward end of the cable will be in the cockpit, and that was the purpose of the exercise.

The bulkhead fittings for the brake lines arrived and I drilled holes for them in the firewall. This is the first equipment mounting on the firewall, and it’s now so that I can figure out the brake flex hoses from the cylinder (there’s one cylinder on the left) and mount those and the rudder/brake pedals. The circles show where they are.





This is my busy season so work tends lag a bit.

Dave

[David Paule]

Since I’m making my own throttle lever, and I’m putting the PTT switch on the throttle, I got to get intimate with the switch today.

The PTT uses soldered wires. Both the Otto switch and Stein’s inexpensive switch need this.

I’m using Dsub pins to terminate the bitter ends of those wires so that I can remove the throttle if need be.

I don’t have any shrink tube the right size or color yet, but plan to hold the wires to the throttle lever arm with that - I’ll shrink over the whole thing, until I get close to the pivot.

In place, the Otto PTT switch that I’d thought was too stiff, is just about right. No concerns at all.



The plug in the back can get pushed in farther but is then difficult to remove. It’ll be held in with everyone’s favorite adhesive, Pro-Seal.

Here are a couple shots of the brake hoses trial-mounted. Thanks to Tom at TS Flightlines for the hoses and parts.



and



For some now-lost reason, I’d routed the manual trim cable below the rudder cable in the baggage and cockpit areas. Turns out that’s quite wrong. After adding a couple more holes in the bulkheads, I relocated it above. Here, you can see the old exit hole in the seat bulkhead below the rudder cable as well as the cable housing fitting. The stack-up of parts at the fitting means there’s only a tiny bit of cable housing adjustment available.



The exact positioning of the trim cable is still a bit TBD.

Remember that the short flap quadrant is only there to secure the internal assembly. That’s not the flight part.

Dave