« Posts tagged electrical

Even more legal, and some argh

10 hours.

Friday I got the static/transponder test done and that’s now in the logbook.   That took a bit, because I had to chase down some leaks.   And, somehow, I managed to snap off the hose barb that connects to the EFIS’s AOA pressure sensor.   That really, really sucks.   Now, once again, I have to dismount the EFIS and take it to MGL to have the AOA sensor replaced.  Can’t fix the barb.  The good news is that the AOA isn’t really necessary for first flight.   Also, my combination AOA/Pitot doesn’t lend itself well to the usual testing method of slipping a hose over the end of the pitot and hooking it up to the test machine.   But we worked around it by connecting the test line to the fitting where it connects to the pitot tube, so I’m going to assume it works.   We’ll find out.

Static tests eventually worked out OK, and we were able to calibrate using the EFIS’s setup menus.    All good!  Signed off, sticker in the airframe logbook.

Today was about picking up the pieces and extracting the EFIS backup battery for replacement.   I think it got run down too far too often and now it won’t take a charge and tops out at 6v.   To do that, I had to relocate the IO Extender module to someplace that would allow me to get to the screw securing the backup battery in its bracket.   When I had to move the IOX before to get it out of the way of the canopy, I’d put it on the end of a piece of angle behind the EFIS.  This solution was kind of half-assed, and I never actually felt good about it, so this is actually an improvement: I put it on top of the throttle quadrant bracket, up out of the way of everything.   I’ll have to dismount the transponder to make changes to the wiring, but that’s OK, it shouldn’t be necessary to change the wiring much.  It’s much more elegant, and gives me plenty of room behind the EFIS to do what I need to do, plus it’s more secure.

I did have to extend the power and ground wires for the IOX, but I was able to use the trim position wires as-is.  It also enabled a much neater wiring bundle instead of the slightly messy arrangement I had previously.

Magnetos timed (again) and RPM sensor fixed.

6 hours.

One of the day’s tasks was to replace the magneto gasket we tore with a new one.   This necessitated removing the right magneto, the one that was cranky about timing.   This is also the mag that has the hinky contact spring on one of the harness wires.  I figured what the hell, I’ll make sure both are timed, so I’ll pull both, put new gaskets on both, and set the timing again.   Big mistake.   Timing mags with two people sucks, as you might have gathered from an earlier post.   Doing it on your own sucks too, and then some.   Yesterday it was hot and windy at OXR, so the hangar was warm and the doors were rattling and making freakish noises every couple of minutes.

There are various sources of knowledge as to how to time mags, but the general idea is that you turn the engine over until the crankshaft is at 25 degrees before top dead center.   Then you zero the mag position by sticking a pin in the timing hole in the back of the magneto where it will sink into another timing hole on the gear inside, thus locking the thing into the position where the points are open.  Then you stick the mags back on your timed engine.

A number of factors are at work here.   There’s the impulse couplers, there’s the slop in the mags even with the timing pin inserted, there’s gear lash in the engine itself, and there’s the ambiguity of where 25 degrees BTDC actually is.   Near as I could figure out, there’s a little lump in the rotation of the mag gearshaft where the points open.   This is no great mystery.   A cam inside opens and closes the points to make a spark.  That fires the spark plugs.  This is no different from your common Briggs and Stratton-powered suburban lawnmower.

But the magnetos are buried amongst wiring, hoses, and engine mount tubes, and getting them back on can be extremely frustrating.  The mag gasket is a little wider than the magneto housing, so it’s really easy to dislodge it.   The engine gears of the mags are also wet with engine oil, so they’re slippery.   It’s also of primary, critical importance that nothing falls down the open mag hole into the accessory case.   If that happens, game over.  If that happens, you better hope whatever fell, like a nut or a washer, falls all the way through into the oil sump where it gets stuck to a magnetic plug — if you have one.  The obstacles in the way make it easier, but not by much, to insert the timing pin into the housing with the mags more or less in place, but supporting them, spinning the gear, and inserting the pin is one of the more frustrating solo tasks there are.  The trick is to get both mags installed so they’re within just a few degrees of each other, because there’s only about 70 degrees of twist available to bring them into line.    If they’re too far off, they’ll never sync up.

The next part is relatively easy, assuming the first part goes OK.   This is where the buzz box comes in. This thing has two lights on it, and you connect the leads to the P-lead connections on the mags.  When the points are closed, the lights are on.  When the points are open, the lights are off.   Or vice versa.   Can’t remember.   The point is, the status of those lights is supposed to change when the engine turns through the specified timing mark on the flywheel.   Both mags are supposed to change at the same time.    There’s actually enough wiggle room with the timing pins in the magnetos to put the timing off by a whole gear tooth.  If it’s off in opposite directions on each mag, there might not be enough range to bring them both back into line at the right point.     But eventually, I got it.   The trick is pulling the prop backwards a bit, then advancing to see the lights go.   The prop has to be pulled backwards enough so that going forwards takes out the gear lash well before the points open, otherwise the adjustments are crap.   But you don’t want to go so far back that you catch the impulse couplers again.    Maybe this isn’t the proper way to do it, but this worked for me.  Also of important note: pull the timing pin out of the magneto before cranking the engine around.   If you don’t, best case is you’ll bend your timing pin like a wet noodle.  Worst case is you damage the innards of the mag.

So I got them as close as I possibly could.    Then I put the shielded ground wires back on.   For safety, the shielded wires go back on the P-lead and ground before the distributor caps go on, because until they’re on and grounded, the mag is hot, and if a spark is triggered, it could swing the prop and really ruin your day, especially if you or your stuff is in the prop arc.   Imagine that.  The prop kicks and sends a blade into the tank of your air compressor or a nearby tool cart.   Prop strike!   Have fun tearing down that engine, sunshine.

By the time this process was over, I was already well past my scheduled time to head back to Los Angeles.   But if you’ll remember, this exercise was only part of the day’s activities.   The other things I needed to attend to were the RPM sensor and the oil temperature probe.   Earlier in the week, Matt at MGL responded to my email and said I needed to remove the ballast jumper on the RDAC and that I could delete the resistor between 12v power and sensor signal.   I pulled the ballast jumper, then proceeded to push the ship out into the wind for a quick test.    Ron and Melody helped me push out and get pointed into the Santa Ana wind.   With the wheels chocked, I fired it up, once again.

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It lit right up, after Owen reminded me that I needed to run my boost pump for a second to get some fuel pressure on startup.   It ran strong and smooth, and I had an RPM reading this time, but like a monkey, I forgot to test each mag individually.  But here’s another ground run video:

This time, however, was another milestone.   We pulled the chocks and I actually taxied down to the end of the hangar row, then back.   At that point, my EGT’s were starting to get a little high, so I thought I’d quit while I was ahead.  We pushed it back into the barn and I went home.

Working on engine-start squawks.

7 hours.

Last week’s engine start, while exciting, wasn’t without issues.   The one I thought was going to be most difficult to fix turned out not to be.   The governor operation was reversed, and the fix turned out to be pretty simple.   I just flipped the governor bracket over and mounted it so the cable operates the arm from below.     All I had to do was put a small piece of angle on the side of the arm to secure the #2 fuel injector line.   We’ll have to see about conflict with the cowl.  I put the top cowl on and it looks like there might be about 1/8″ of clearance between the new governor cable arc and the underside of the cowl.  That’s not a huge deal though, and I’d rather put a blister on there than go through the hassle of dismounting the governor and sending it back to American Propeller to see if maybe, just maybe, they can reverse the operation.   Either way, that would cost me in time, in shipping, in ability to test the engine in other ways and debug the two sensor squawks from last time.   The hardest part was the firewall-penetration eyeball.  It’s almost impossible to get to and I still need to torque it down, because it’s not laying flat like it’s supposed to.  I had to take it out so I could get the extra half inch of cable slack necessary for the flipped bracket.

On the others, I had no luck.   No RPM reading, no oil temperature reading, although I have no idea how long it takes the oil to warm up to a minimum of 72 degrees.    The rpm thing is a little scarier because i don’t know if it’s the wiring, the sensor, or the magneto the sensor is attached to.   I’m going to have to break down the wiring of those two pieces and go through it piece by piece.   I really hope the senders aren’t bad, because those things are not cheap.  Replacing both is about a taildragger lesson’s worth.

Speaking of which, I have replaced the ON/ON/(ON) magneto switches with ON/ON DPST  switches.   One side of the switch handles the start circuit and the other handles  the mags.   When the start circuit is enabled, the magnetos are ungrounded.   Since I have two impulse-coupled mags, I can get away with this.   At this point, the starter button on the stick is the only way to kick the engine over now, which is OK, but I plan to install a pushbutton to forcibly engage the starter should the relay the stick button actuates takes a dive.

The magneto timing still needs work.  Even after the switch replacement, the right magneto still makes the engine backfire like mad when it’s on its own.   I’ll need to retime it anyway when I install the new gaskets, but it’s still a royal pain and I’m not keen on doing too many more runs with it in that condition.

Oh, and joy of joys, there’s a small crack in my canopy, in the aft right corner, coming up from the last screw hole on the canopy frame.   I didn’t catch it until now, because it has been  covered with masking tape, which I removed yesterday.   I removed all the protective plastic from the canopy, except for a swatch between the rear canopy and the roll bar brace.   Now the fun is going to be getting that last piece of plastic out from there.  I’ll probably have to dismount the rear canopy, which I would have had to do anyway to get some kind of seal in there.

Engine Start, Part 2.

  1. 5 hours.

Armed with last weekend’s knowledge and suspicion, David and I headed up to OXR to debug and correct the mag and start wiring, then actually start the engine.    We had a copy of The AeroElectric Connection and more importantly, the airport gate card, which allowed us to come and go as we pleased.

Even though we knew what was wrong, it was puzzling, because we were trying to follow Bob’s diagram and make an open circuit for one thing while making a closed circuit for another.   Maddening.

Eventually, we did figure it out and we were rewarded with the sound of an airplane coming to life.

Hooray! Huge milestone, and only three squawks:

  1. No RPM reading.   This is most likely a bad ground or a severed wire coming from the pickup on the magneto.
  2. No Oil Temperature reading.   Maybe this shares a ground with the tach sensor.
  3. (and this is a big one)  Governor operation reversed.   The prop does cycle and the governor doesn’t leak, but it operates the wrong way.   I need to set it up so the prop increases pitch when I pull the blue lever back.

No leaks, no fires, no pieces flying off.   I’d call it a good day!

Engine Start, Part 1.

6 hours.

A tiring and ultimately unsuccessful day.   Dave and I went out to the airport with the intention of starting the engine for the first time.   We were off to a stellar start: I’d forgotten my airport key card; it was still attached to my motorcycle safety vest at home. I didn’t notice it until we were actually in Oxnard, so that sucked.   We did manage to find somebody to let us in, then went about the business of readying the plane for engine start.   We dumped 8 quarts of oil in the tube, then attempted to time the magnetos.    This is harder than it sounds.   Once we actually figured out how to use the buzz box, the cylinder plug, and our own eyes, we got the mags in and timed to the engine.   That’s when the fun started.

We wheeled the plane outside and prepared to start it up.   We left the distributor caps off the mags so we could spin the engine a bit and pre-oil it.   with four plugs removed, we were able to spin the engine around and get oil into all the nooks and crannies and actually see an oil pressure reading come up on the EFIS.      Prop spins, there’s oil, let’s start it!  Foolish us.   Slick magnetos are designed to run when their circuit is open, that is, the two leads connected to them, when connected to each other, make the magneto safe, cold, whatever.   The AeroElectric diagram has you connecting these two switches together in such a way that the right mag fires when you’re starting and the left one doesn’t do squat until the engine’s running, that is, you’ve let go of the spring-loaded upper position toggle because the engine is running.

Somehow, I’d wired it in such a way that the mags were connected/safe when the switches were “on” and the start circuit was on.   The engine spun, but wouldn’t start.   Fortunately, safety wasn’t in question.   The way I had it wired, no matter what position the toggles were in, the mags were grounded, so it’s not like the prop would have taken our faces off.

By the time we’d gotten wind of the problem, it was too late to debug and we were tired.  Tired people working with dangerous things tend to get hurt, so we packed it in and crawled home, after begging to be let out the airport gate.

More connections and a flight

6 hours.

Today was spent tidying some wing attach stuff.   I got my order from ACS, so I was able to finish installing and torquing all the wing attach hardware.   I also did the fuel line on the left tank, remembering this time to put the rubber grommets on before flaring the ends.   There’s a $30 tool that will stretch those rubber grommets out so you can get them over flares and fittings, but I figure it’s good practice just to try to be less stupid.

The most interesting part of the day was the short flight I took in my hangar mate’s Luscombe.

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I’m not sure which model this is, but I think it’s an 8C or 8D.   It burns 4 gallons per hour, which is probably about half of what the Pipers I learned on did.   It has no flaps, no lights, and only the minimum equipment of single radio and transponder to get around Southern California’s interesting airspace.

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Now, I’ve never been in, much less flown a taildragger, and the oldest airplane I’ve even sat in was an old L-19 Bird Dog in Ft. Leavenworth KS when I was a little kid.    This aircraft was built some time during the early 1940’s, and Ron was kind enough to let me follow him on the pedals to get a feel for the quirks of a taildragger.   This shot is one out the right window, us taxiing to runway 22 at OXR.

20130616-093659.jpgAnd another out the front.

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The instrument panel is simplicity itself.   Everything you need for day VFR, nothing you don’t.   The mount for the Garmin 296 GPS looks strangely out of place, over to the side out of frame.   There’s a single vernier cable control for throttle and a small one for carb heat.  I didn’t see one for mixture.  I don’t think there is one.   The fuel gauge is on the bulkhead behind me, between the two seats.

 

20130616-093736.jpgWe did a landing at Santa Paula, where I was able to get a picture of Steve McQueen’s old hangar.   I love this airport already.   I just wish we’d had the chance to buy McQueen’s old ranch when it popped up on Jalopnik last year and it was dangerously close to something we could afford at its fire-sale price.

 

20130616-093750.jpgThat adventure only took about 20 minutes to half an hour.   When I got back, I did most of the real work.   Here’s the right flap, on and conneted.  There’s some more rigging to be done,  and some more wiring, but the wings are nearly fully on and connected.   I also got the left rudder pedal connected to the cable, but ran out of time before I could do the right one.   I’ll hit that in a week.  Soon it will be time to mount the prop!

FWF Sensor Wiring DONE!

10 hours.

This is yesterday and today. Yesterday started with an epic shop cleaning. I have those every so often, and it’s helpful, extremely good to have a workbench devoid of clutter, if only for a little while. Stuff got put away, stuff got tossed out, floors got swept and vacuumed.

The fiddling with the FWF stuff has been progressing as well as I can make it, and the wiring has been a bit of a challenge, especially since the K-Type wires on 2 of the sensors were too short to make it all the way to the RDAC engine monitor module. Then there’s the business of where to actually run things so they don’t rub on other bits or get roasted alive by the exhaust pipes. I got the current sensor done, although I suspect I’ll have to flip it over, I got all the temperature sensor wires run, wrapped, and grounded. About the only thing that didn’t happen is the MAP sensor, which needs a 1/8″ to 1/8″ barbed elbow fitting. Searches have turned up no such animal so far. But technically, that’s not wiring, so legally speaking my FWF sensor wiring is done.


Here’s the beginning of the attachment process. The overbraid K-type wires are a ratbastard to work with. They’re a little like shielded cable, but they’ve got an extra woven sheath below the braid that absolutely sucks to try to get off. Maybe there’s a trick to it, but this was by far the worst suckage of this task.


A slightly different angle. On the RDAC (the grey box), the first 4 pairs are exhaust gas temperature thermocouple inputs. Can’t change them, which kind of sucks, because then I wouldn’t have had to extend a couple of TC wires to make them reach the proper input. Oh yeah, splicing TC wire sucks too. The ty-wrapped snarl at the bottom is the FloScan fuel flow sensor wiring. I installed the FloScan months ago, but never got around to properly wiring it until today.


Still a rat’s nest, but there is progress there. This is right after grounding all the things that needed grounding, being the FloScan, the tach sensor, and the RDAC itself. The EGT and CHT probe wires haven’t been cut to length yet, nor have they been secured by Adel clamps to the firewall.


Ahhh, that’s better. Still some wrapping to be done, but all the wiring is secured and attached.


This shows the oil pressure sensor hooked up and run into the bundle. This will benefit from a couple of Adel clamps attaching the main bundle to the engine mount, but we’re in a pretty good place.

Even more fun: Once I got everything wired, I fired up the EFIS and decided to test out whether or not I’d actually inserted the right wires into the right terminals on the RDAC. This was done by means of a heat gun and a blowtorch. The heat gun raised the temperature of the actual cylinder itself so I could check the reading on the EFIS. The blowtorch was for the EGT probes. Suffice it to say that the method of testing was a great success: I found I had miswired the 1 and 3 cylinders for EGT, and the 2 and 4 cylinders for CHT. It is now all fixed.

Oil Door.

6 hours.

Yesterday and today.
Yesterday I worked on the oil door. The finish kit comes with a fiberglass version, and it’s meant to be held down with an elephant-ear Camloc fastener, but it looks like ass if you do it that way. A better alternative is the Nonstop Aviation hidden hinge kit.


It mounts the door on a sprung hinge that opens up and out of the way of the cowl. You can use the fiberglass part from the kit for the actual door, but like some others have done, I made mine out of .032 aluminum. The reason? When the fiberglass part gets heated by the engine, the pressure from the hinge trying to open will warp it. Aluminum has no such limitation.


Once the door is cut, formed and drilled, the flush-mount Camloc release latch goes on. I actually made two of these things, because I screwed up the Camloc location on the first one. No biggie. I still have half of a .032 horizontal stabilizer I’m using for stock.


When it’s all in place, it closes flush and latches properly, but getting the hole for the latch handle was kind of a bear.


When it’s open, the spring keeps it out of your way so you can check oil, remove hinge pins, etc.

Today I was doing more checks of things under the area where the top skin will go, because that’s going to have to go on soon. I spent some more time securing wires and torquing down Adel clamps. In doing so, I found that I never riveted the row on the longeron right next to where the canopy closes. They leave them open at the QB factory because the slider canopy mounts a little differently. This isn’t all that easy to deal with when the panel and other things are installed, but it’s not that bad either. All I had to do was disconnect the vent hoses so I could get hands and bucking bars up inside the channel by the longeron.

After that, I started putting the baffles back on, but didn’t get very far. I’ll do some more of that tomorrow.

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Here are some pics from the last couple of weeks.  I’ve recovered my server-side image processing script, so I promise more photos in the future.


This is the mess before I cleaned it all up.


Flap actuator and servo reinstalled (Yay!)


Fuel pump reinstalled, lines secured.


This is me working on the endless process of dressing cables and zip-tying everything.

Avionics Install (almost) DONE!

4 hours.

Sweet FA got done over the weekend (New Years, hangover, etc, etc.), but today I finished wrapping and securing various wires, as well as rerouting the starter ground in a bundle instead of floating around all by its lonesome.

Only two things left to do, really, and that’s to install the OAT probe and reconnect the IOX when it comes back from MGL in a couple of weeks.  For now, i’m not sure whether or not to start the baffling or the FWF sensor wiring.