Dave’s RV-7A Building Log

I didn’t get down to the hangar last night. I worked on the Pilot’s Operating Handbook and checklists on the computer. Need to get those finished up for Tuesday.

Tonight I again got a bunch of little stuff done. The plan was to do a taxi test, but it was spitting rain all evening. I started off by checking the air pressure in all the tires, and securing the cotter pins on the wheels (just remembered that I hadn’t done that yet).

The fuel pump overflow fitting is once again broken, I’m going to try fixing it one more time. It’ll be easier than figuring out which AN fittings I need.

I started working on securing the canopy release mechanism. I cut the handle short so it will stick out of the subpanel, but not the main panel. I’ll then secure it with an adle clamp.

I was messing around with the stick again, and noticed a strange clunking sound. Turns out the forward elevator pushrod was hitting the bottom of the opening in the F-705 bulkhead. Must be related to me securing the push rod during the last session. I’ve never noticed it before. I filed the opening a bit larger until it stopped hitting/rubbing.

I used a short section of vinyl tubing secured with Shoe Goo to create a chamber under the top AOA port. That will help guide the pin for draining it.

I replaced one spark plug. Many months ago, I accidentally dropped it on the floor. I was slightly concerned about it, but figured it was fine. Well, I read an article last week that said the insulator can crack causing all sorts of problems including pre-ignition. Not good. I remembered exactly which one it was, so I picked up a replacement at B&B Auto Parts and installed it (Shucks, the world’s worst auto parts store, doesn’t stock it).

I’m sure I did a few other things, but I can’t remember them at the moment. Lots of little details. My (hopefully) final order from Vans arrived, so I’ll take care of the last few items tomorrow and Saturday.

Chris Kleen, an RV-6 builder and flyer, stopped by. I figured we’d chat RVs for a while, but he was soon poking around in the engine compartment and spent the better part of an hour going all the way around the plane checking all sorts of little things. He had a bunch of suggestions and I wrote down a few things to fix. Thanks for stopping by Chris. It was great to have a set of experienced RV eyes look over the plane.

I keep crossing things off the list of items left to do, and I keep adding stuff to it. Luckily, the stuff I’m adding is pretty minor. For example, clean the canopy, secure the wing conduit pull string, etc. I took care of a bunch of little stuff like that today.

I tried fixing the canopy skin. It will no longer catch, but it definitely doesn’t look pretty. Still need to do some cosmetic work there.

I was messing around in the cockpit and decided to look into why there’s a tiny bit of pitch freeplay in the stick. Turns out I never tightened the jam nut on the forward push rod. Guess I thought I would need to adjust again. Once I noticed it, the loose nut seemed like a glaring omission. Of course, I’ve looked down there a hundred times over the past few months and never noticed it. Luckily, the push rod is designed such that even if the nut is loose, the push rod can’t get free.

I then decided to check the other end of the push rod. Sure enough, that nut was loose, along with the autopilot servo push rod. Getting back there was uncomfortable, but I tightened and torqued everything that was loose. I’m planning on doing a full check out of everything on Saturday, following an annual condition inspection checklist. I would have found these loose fittings anyway.

Tightening up all the push rods reduced the freeplay significantly. There’s still a tiny bit left, but it’s got to be less than 1mm. Very, very minor. There’s absolutely no freeplay in the ailerons. I went on to measure the elevator and flap angles. The elevators are within Vans published specs, but the flaps go down 44 degrees versus the 40 degree max specified by Vans. I’ll double check, but that shouldn’t be a big deal.

I also installed the fire extinguisher. I put it right behind the passenger seat. It’s out of the way and accessible. It was tricky reaching under the seat pan to tighten the nut, but it’s done now.

I confirmed my inspection appointment with Richard Tardif for March 20th. Woo hoo! And I confirmed Terry Burch will do the first flight as soon as the weather cooperates after that. Double woo hoo!!

I noticed the fuel pump overflow fitting broke a while ago. It’s just a brass plug with a hole drilled in it and a tiny copper tube soldered in. The solder joint broke at some point while I was installing it way back when. I tried fixing it yesterday by re-soldering the joint with a plumbing torch. I was down in Renton at lunchtime dropping off my airworthiness paperwork at the MIDO, so I stopped by the hangar to re-install it. In the process of wrapping the safety wire around the tubing, it started to jiggle again. Vans funky fitting is just a poor design. There isn’t enough contact between the brass and copper to make a good solder joint. The whole reason Vans created this fitting is that there isn’t much room between the engine and firewall in an RV-4. There’s plenty of room on an RV-7A. I’m going to switch to real AN fittings, eventually.

While I was at the hangar, I also wrapped the fire sleeve around the fuel flow sensor and secured it with safety wrap. Now that I know there’s no leaks, I’m comfortable covering it up. It’s not super pretty, but is functional.

The first task for today was to make and install the fuel tank vent lines. They’re a little tricky, but not too bad. I tie wrapped the tank sender wires to them.

I was never happy about the method I used previously to set the aileron neutral position. I decided today to use the established method of lining up the wing rib tooling holes with the aileron tip. I secured both ailerons in that position and then modified the push tube length until the stick was straight up and down. (The picture looks strange, but that’s just the wing tip sitting upside down on top of the wing.)

I then altered the flaps to match the aileron position. The flaps were hitting the fuselage, so it was not possible to get them exactly the same as the ailerons, but the top surfaces line up. The flap trailing edges have a slightly larger radius, so the bottom skins are slightly off (like 1/32″). Close enough. In that process, I noticed that I needed to enlarge the hole in the fuselage some more. The flap push rod bearing ends can swivel a bit, and in some positions they were catching on the fuselage side and bottom skins. A little filing took care of that.

Going back to the ailerons, I installed and tightened all of the bellcrank and stick hardware. The ailerons are now rock solid. There was a slight amount of play before I tightened everything up, but there is absolutely zero play now. Also figured out that I need to adjust the springs for the aileron trim. There’s not enough centering action with the current set up.

I measured the aileron deflection as 31 degrees up and 17 down on both sides. The max is 32 and 17, so these values are perfect.

This picture didn’t really turn out that well, but it shows condensation forming on the tanks. The temp and humidity both went up about 15-20 units over the course of an hour. Everything that was cold in the hangar, including the fuel tanks, tools, even the floor, formed condensation. Quite yukky. I’m going to make a homemade engine dryer after seeing this.

Just before I was about to leave, I decided to play pilot with the stick, and a strange thing happened. The stick wouldn’t go all the way forward. I checked all of the control mechanisms and surfaces. Couldn’t find a problem. It finally dawned on me that the aileron push tube was causing the problem. I had it tightened in such a position that it was preventing full elevator deflection. I adjusted the angles on the push tube bearings until it was fixed.

One of my candidates for DAR finally called back. I set up an appointment for next week. He’s not cheap, but at least he’s available. We’ll see if the MIDO can process the paperwork in time. Guess I should get that mailed in. And I confirmed that the MIDO does process the paperwork, at least for him.

The goal today was to finish everything in the wing tips. I connected the right nav light, and the VOR and marker beacon antennas in the right wing tip. I drilled and countersunk the lens. The fit isn’t perfect, but good enough for flight.

I found some aluminum duct repair tape for making a better ground connection between the wing skin and the antenna. I then used Shoe Goo in a few spots to glue the VOR to the wing tip. I think that stuff is just a fast-setting RTV.

I used the Shoe Goo on the MB antenna as well, seen here weighted down to hold it in place.

The right nav light is on in this picture, although it doesn’t look like it. It’s definitely bright when it’s on.

Next task was to attach the fuel tanks to the fuselage. It’s a pretty straight-forward process of bending the bracket a little, drilling the hole, installing a nut plate, bolting everything together, and then safety wiring. However, access in this area is not great. Got both sides done.

Last task for the day was to measure the fuel flow. I disconnected the fuel line at the servo and directed into my calibrated fuel can. On 3 separate trials, it took an average of 3.75 minutes to fill to the 3 gallon mark. That calculates to 48 gallons per hour, which is about what I expected–way more than the engine consumes. The strange thing is that the engine monitor was reporting a flow of 24.1 gph. The sensor is supposed to handle up to 70 gpm, so not sure what’s going on there. I’ll ask AFS about it. I used this opportunity to balance the fuel as well. There’s now 12 gallons on the left and 9 on the right. Should be good enough for first flight, although I’ll ask my test pilot what he prefers. Probably best not to fill them up completely.

At some point during the day, I decided to take a couple side pictures of the firewall forward. I’m not exactly sure I have the wires secured well enough, and was going to ask around about it.

Long, but productive day.

Calibrating the fuel level sensors is not exactly straightforward. The Princeton capacitive converters need to be set at empty and full. The engine monitor system then needs to be set at various calibration points. I couldn’t figure out any other way then to start with an empty tank, set the empty point, fill it up, and set the full point. Then with an empty tank again, set the EMS empty point and I used 3 gallon intervals for calibration points to full. I was basically jockeying fuel back and forth between tanks with a fuel can that I marked at the 3 gallon mark from the self-serve pump on the field. Very, very time consuming. To make things a little easier, I found a fitting at Ace hardware that converted the fuel drain to a barbed fitting for a hose. I used the hose to direct the fuel into the gas can, and to shut off the flow.

Before doing all of that, I hooked up the left nav light.

I bought a high-end bathroom scale accurate to 350 pounds for the nosewheel and re-weighed the plane. The results were much better this time. I also discovered I might have messed up the arm lengths on Tuesday. I measured those with the plane on the ground, and not level. That would have moved the CG artificially forward as well. My numbers didn’t exactly match Vans published numbers, but it’s obviously important to measure the arm lengths in the exact configuration that you weigh the plane.

Here’s the spreadsheet breaking everything down. The net result is that the plane with everything but paint will be 1150 pounds and an empty CG of 79.55″. That is much more in line with what I expected. I am done monkeying with scales.

I moved on to the wing tips. I never finished the wing tip lenses, so I drilled those to the wing tips and installed nut plates. I wanted to light something up, so I started working on installing the navigation light/strobe combos. I got the left one installed and then temporarily hooked up the right strobe. It makes quite a light show in the hangar. I’m very happy with the nav lights from CreativAir and glad I painted them white. They look great.

I think I’ve tracked down a DAR, but I need to submit my paperwork to the MIDO first. That involves getting the weight and balance of the plane. I borrowed some scales from a local builder (thanks Joe). The only problem is that he only had two industrial type scales. For his Cozy the nosewheel is only 20-30 pounds, so a bathroom scale is adequate. An RV-7A nosewheel is in the neighborhood of 300 pounds, which is the max for the scale.

He made some cool ramps for the scales. I set those up and got the plane up on to the scales. Using a jack to get the nosewheel onto the bathroom scale, it became obvious I needed more height under the mains. The plane needs to be level. I put some blocks on the main scales and pulled the plane onto those. Much better. I loaded the plane down with all the covers, fairings, seats, cowl, etc. Basically everything except for the wheel pants, leg fairings, and the interior parts I’m planning on leaving out during the test period, side panels and carpeting. I drained all the fuel from the tanks via the fuel pump and filled the engine to the 8 quart mark. The total was about 1130 pounds. Not great, but not terrible. I then put the carpet and side panels in as well. That put it at 1170. Ouch. With fuel tanks and using Vans recommended 1800 gross, that leaves a payload of only 378. Without paint.

I use some plumb bobs to measure the locations of the wheels relative to the wing leading edge. Forgot to verify those against Vans numbers.

When I got home, I did some rough calculations. The non-carpet/side panel empty CG came out to 77.77. Cool number for an RV-7A, but way too far forward. Looking at Dan’s RV Weight and Balance Database, no other RV-7A is that far forward. There’s one at 78.61, but he’s got an IO-390 engine that is much heavier than mine. I think the bathroom scale was not a good idea. The wheel was pushing down pretty heavy right in the middle of the scale and deforming the surface. I think that is throwing everything off including the total weight. I hope.

While I was still down at the hangar, I drained the rest of the fuel from the tanks. I didn’t have any measuring device handy, so I used an empty water bottle that I previously drained/dried of all water. I was expecting much more fuel than actually drained out. It was about 1/2″ in the bottle. Same for both tanks. (No flop tubes.) I calculated that to be about 0.04 gallons. That’s great. I know that’s not exactly the right way to measure unuseable fuel. I should have the plane in the climb attitude and then drain all the fuel with the pump. However, it’s very difficult to safely get the plane into the crazy steep climb attitude of an RV. The value I got is right in line with other builders, so I’m happy with it.

I had a bit more time in the evening, so I wired up the Gretz heated pitot tube. I actually did most of the wiring a while back with the wing in the stand. I just had to connect the power and display wires. I gave it a quick test. First the red and yellow lights turned on, low heat and heat on. Then red/low heat turned off and the green/temp OK light turned on. Then yellow/heat on turned off. Worked perfectly. And man does that thing get hot. Well over 100°F.

Almost forgot. I also hooked up the laptop to the P-mags and set the advance curve offset to 0.0 from the factory default of 4.2. That’s supposed to be better for keeping the temps down until the rings seat.

Now that the engine runs, it’s time to knock out the rest of the little details. The most major detail was finishing the hook ups for the pitot and static lines. These air low pressure air lines that run to the instruments for calculating speed, altitude, and rate of ascent/descent. I ran most of the tubing a while back, but discovered that the Trutrak autopilot and AFS EFIS have the ports too close together to use T fittings. I ordered some straight fittings a while back, but have been too busy to install them. There’s not much room behind the panel, but I eventually got everything hooked up and the autopilot re-installed.

I used a trick I read about for testing the system. I bought a few feet of surgical tubing from Lowes and stretched that over the pitot tube. I pinched the end closed and slowly rolled up the tube to increase the pressure. Sure enough, the airspeed indicator and EFIS both registered the same speed. I held it for a while to make sure there were no leaks. The static system was a little trickier. I had to hold the surgical tubing up to the static system with it already rolled up and then unroll it. I was able to get a few hundred feet of altitude on the EFIS, but I really need another set of hands to do it right.

Next I decided to knock off an “easy” task from the list, fixing the safety wire on the autopilot roll servo. It was a bit too loose. After 3 tries, 20 minutes, and a bit of swearing, I eventually got it looking better. I’m not a big fan of safety wire.

Since the autopilot was back in, I decided to test it out. I remember switching the roll servo wires months ago when I first tested it. Well, I somehow reversed things in my mind. I had to switch the wires again, and it started working correctly. Increasing the heading should make the stick tilt right. The pitch servo has been in and working correctly for a while.

Started the engine for the first time!!

I got to the airport before Julie and Adele and checked a few things. First, I made sure the prop was tracking. That looked perfect. I then checked every oil, fuel, and wiring connection to make sure nothing was loose. I pulled the plane out front of the hangar, chocked the wheels, tied the tail to the fence, got the fire extinguishers handy, and moved the cars well away from the scene. All systems are go!

The engine didn’t kick the first couple of tries. I had the throttle closed the first try, and I think should have re-primed it for the second try. Maybe it just needed to get some fuel through the system. The third time she started right up. Unfortunately, I followed the directions from AFS and moved the RPM feed from the P-mags to pin 33 of the EMS harness. No RPM at all. I ran the engine for a minute, but decided not to go any further. Still a very cool first start!!

I changed the RPM wire back to pin 32 and tried again. Bingo. All sensors were working great. I ran the oil temperature up to about 90 degrees, the engine up to around 1700 RPM and tried cycling the prop. Worked on the first try. I cycled it a couple of times. The idle is a little low at 600 RPM, but otherwise the engine is purring like a tiger. I was hoping to catch the stats for the event from the engine management system, but for some reason the Advanced Flight Systems AF-3400 didn’t capture any data. Strange.

One bummer on the day is that the stupid tip-up canopy decided to catch in a major way when I opened it. It’s been fine for weeks, but the engine must have settled it somehow. I’ve got some repair work to do there.