« Archives in March, 2011

Neural activity detected.

2 hours.

Instead of hemming and hawing about not having the switches I need, I went ahead and wired up some of the stuff I actually do have. Power was available, so I wired up the harness for the EFIS and the power/ground for the RDAC engine monitor module. I’ll let the video explain it:

OK, I said “firewall,” but I meant “subpanel.” I’m new at this whole video thing.

Power feeds wired.

3 hours.

Most of them, anyway. Turns out I need a couple of different switches. I need a dual-pole on/off switch for the battery master, because I’m deleting the alternator field enable. The idea with the alternator field enable is that if for some reason your alternator goes blooey and starts up with runaway voltage, you can shut off the field before it zaps all your goodies. This is a throwback to the days when alternators sucked, some time in the early sixties, and the chances of you interrupting the field before your fancy MFD’s and other computerized avionics surge out are next to nil. Modern alternators are usually pretty bulletproof, unless you switch the field on and off while it’s spinning. Doing that can reduce the life of the alternator from thousands of hours to hundreds, so the battery master is going to be a DPST switch that engages the battery master and the alt field simultaneously. I had to order another couple of switches from B and C also: the one from Van’s sucks. It has no keyway or tabbed anti-rotation ring, and it doesn’t even have a hex nut on the panel side. So I ordered a DPDT switch for the flaps. I also brain-farted on my initial layout, and forgot the heated pitot switch. Ran the circuit for it, allotted amperage for it, forgot to put it on the panel. So I needed another SPST on/off switch for that, because the one I had originally for the pitot heat was repurposed for the pax enable switch.

Yesterday was a bit of a milestone. I installed the firewall grounding plate, which is a brass plate with a bunch of fast-on tabs on one side. The other side is in contact with the firewall, and a big 5/16 brass bolt goes through the firewall, where it becomes the attach point for the negative battery cable and the braided strap that connects to the engine block. With this in place, I ran the wires for the master battery switch. For the first time, I connected the positive power lead to the battery. When the battery master switch was turned on, there was a satisfying >clunk< from the firewall, which meant that the master contactor was working. I checked the main and endurance busses and read 12.5 volts on the multimeter. I didn't hook up the starter switches. I'm still puzzling out wiring runs, But I'll get to that soon enough.

Radio stack.

3 hours.

Ugh.. I hate being sick, especially if it’s on a weekend. The previous weekend was Dave’s (yes, the Dave appearing in this blog) birthday. His 40th. So a gaggle of us went to a rented karaoke room, drank sake, sang songs and ate sushi. We did this until they kicked us out around midnight or so, then we all went back to Dave’s and the revelry continued until 4am or so. Epic, awesome, amazing weekend. Paid for it this weekend with an unbelievably bad cold and fever. It started Wednesday afternoon and I was flattened until yesterday. I managed to get a little bit of work done, but not much.

Here we have the EFIS and the radios all in their trays, switches in position. I’m going to have to replace the battery master with an on-off switch instead of the one that’s in there, because I have no plans to kill my alternator field in flight or otherwise. Killing the alt field shortens the life of the alternator by hundreds of hours, so buggerit, I’m doing it differently. If the battery master is off, the alt field is off. That’s it. I also have the EFIS backup battery swictch and the warning light, which gets hooked up to the EFIS, which will theoretically warn me about things that are, uh, interesting.

Next step was to mount this whole bastardly collection on board. The hole in the subpanel, carefully measured, should accommodate the end of the GNS 430.

OK, fine, but It looks like my measurement was off. I had to cut another half inch of metal off the hole at the bottom otherwise the panel wouldn’t sit right against the remaining support rib.

No big thing. Once that was all set up, I could solidify the radio stack by riveting a couple of ears onto the GNS430 tray and bolting them to the subpanel. I also made some angle brackets to support the transponder by tying it to the audio panel, which is on top of the GNS430. None of this is going anywhere. I could stand on this setup and it wouldn’t budge.

Test fit-up looks good, not hard to screw the panel back on, and everything is rock solid.

I’m thinking about doing a couple of angles on the back side of the subpanel where the ears on the 430 are. This will spread out the load even more, plus it’ll give me some beef to put on a couple of platenuts for the ears instead of just using hex nuts. As it is though, I was able to fit all the components in and lock them down, then get them back out again, which means that I got my geometry right when I set it all up on the bench.


3 hours.

I’ve been on the road the last couple of weeks, and I haven’t exactly been wonderful about updates, so let me give you the big picture. After fiddling around with various combinations of throttle body configurations, I figured out that the way the AFP manual states, with the TB clocked 90 degrees and the arms on the bottom, is the way it’s going to be. This will let me get the mixture cable on a straight run across the bottom of the sump and the throttle cable in at a 45 from the left side. Interference between cable brackets might be a factor, I’ll have to check, but I think I’ll be OK. The only thing that concerns me is the distance from the #1 exhaust pipe to the throttle body and cable. The plan is to use the heat muff as a shield, which should work, as there will be cold air coming into it constantly and carrying away heat radiated from the pipe. This makes the fit a little tight, and there will be a need to shield the cables as well. Fortunately, there is a plethora of products designed to do this very thing. Now, one thing to be aware of is that the shielding must not interfere with the cable operation, and must be effective enough to keep the cable from being damaged, because damaged cables stick. You do NOT want a stuck fuel system cable. Best case scenario is that it sticks open and you have to regulate power on landing by turning the ignition on and off, a digital engine, so to speak. A worse case than that is that it sticks closed and you basically join the engine-out club. Absolute worst is that it catches on fire and burns and you hit a UFO on the way down, provoking an interstellar war while trying to wrestle a burning aircraft to the ground. This, however, is unlikely. Custom brackets will still need to be made, and I think I can make them either from billet aluminum or schteel, but I might have to draw on my uncle’s machining capability for steel. I can also make them from 1/8″ 4130 sheet, so for the first time in my life, I can honestly say I NEED a plasma cutter.

So with the firewall forward install more or less on hold for now, I went on to installing probes and senders. I got the CHT probes installed, K-type wires spliced, and extensions run back to the RDAC on the firewall. These will need dressing and permanent mounting. Oil temp probe is in, and I got my fitting to go from AN3 to AN4 on the oil pressure line. I also re-clocked the right mag so the harness clears the battery. This was interesting. I got a timing box from Sac Sky Ranch, then timed it according to procedure in the manual. Pull the mags, rotate the engine to 20BTC as marked on the flywheel, insert the timing pin in the mag, reinstall. Then connect the timing box and turn the other mag so the lights both go on at the same time. It’s a little more involved than that, but that’s the general ideal.

So with that done, I decided to cut my instrument panel. I cut the hole for the EFIS, which had to be adjusted after someone on VAF mentioned the tube under the glare shield of the canopy. I did the poor-man’s laser technique. Marked it out, masked it off, cut it out with a sabre saw. I’ll post pics when I get a chance. After that, I had to dial in the radio stack. I put all the components on their side with the bezels aligned, then taped them all together. I marked lines on the trays for alignment later, then measured the hole I’d need based on the dimensions of the components minus the trays. Once I got the hole good enough to get all the components in, I lined up the stack to the panel by means of lots of clamps. Then I took the components out of the trays, got out some more clamps, and fastened everything down for drilling. I now have the hole for the stack, the primary angle on either side to hold the stack, and next is the bracket that ties them all together at the back end. I’m going to have to cut the subpanel to account for the GNS430’s massive booty, and the whole thing will be bracketed to the subpanel for extra rigidity.

I also lined up and drilled the holes for the toggle switches above the radio stack. I still need to drill the holes for magneto switches, battery master, and alt e-bus feed to the left of the EFIS, but I need to determine what kind of switchgear I need. I think I’m one switch short, which is puzzling, because I checked my order against my plan several times. I also have to go to Fry’s and pick up some electrical supplies like a warning light and a dimmer for the cockpit lights, but it’s getting to the point where I can start actually wiring things instead of just making wire runs.

I’ll post some pics as soon as I get them off my phone.