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Mechanical Gauge for oil

Someone on Van’s Air Force asked about the backup oil pressure gauge I installed.  After combing through this blog and not finding any pics, I decided to make a post about it, since it was a super-easy fix and a qualified A&P could do this in their sleep if they had to add one later.   The reason for this was a gnarly scare I got during test flight back in 2014, when I had what appeared to be a complete loss of oil pressure over the Ojai foothills.   

It turns out I was getting bad data from the RDAC on my EFIS/EMS.  For some reason, and I was never really sure why, the oil temperature didn’t seem to map to reality, and when it got above 200 degrees, other readings became erratic. When the oil temp cooled back down to ~180 degrees, everything leveled out. What I suspect is that heat-soaking the RDAC may have damaged some of the components on the board, or the heat expanded something just enough to cause a short or disconnect a path to ground. 

This problem went away completely after I replaced the RDAC with the new version, which is mounted on a thick aluminum plate and has much more robust hardware.

I put in a mechanical oil pressure gauge from Autozone, because oil pressure is the one instrument I can’t afford to have lying to me.  The rationale was that if the digital and analog readings mostly agree with each other,  I can make good operational decisions. The analog gauge didn’t have to be dot-accurate either; as long as it was consistently showing a number in line with the expectations in the Lycoming 360 manual, I could reasonably conclude that it was safe to fly.

There’s a manifold mounted on the firewall for engine fluids, typically fuel and oil.  The manifold has 3 places to plug in some type of fluid under pressure.  To install the AutoZone gauge, I simply removed the plug from the 3rd hole on the oil input and installed a fitting appropriate for the connector on the nylon oil line.  I don’t own the plane anymore, so I can’t check, but generally, the idea was to undo the firewall pass-through seal, run the line from the gauge out from the cockpit through the pass-through, connect it to the fitting on the manifold, then reseal the pass-through with high-temp RTV and high-temp zip ties.

The pic below shows the situation before I actually did the work, but the annotations describe what happened.   NOTE:  The squiggly yellow line from the manifold plug running through the pass-through is where the mechanical gauge’s oil line runs.


As much as it pains me to do this, I need to sell 313TD.    Life has course-corrected a bit, so flying and maintaining an airplane are not compatible.  Info is below the pictures.

S/N: 72402
Location: KCPM
Asking Price: $105,000
IFR/VFR: VFR Day/Night (IFR equipment is installed, but never flown IFR)

Why selling: Life and aircraft ownership are now divergent.  
Total Time (hrs) on airframe:  137
First flight date: March 3rd, 2014
I am the original builder

Empty Weight (lbs):
– CG (empty weight – inches from datum):
– date of last weighing:
Year painted: 2016
Painted by: Century Air Paint in Chino, CA
Engine Make/Model: Lycoming O-360-F1A6
– HP: 180
– Total Time Air Frame: 137
– Time Since Overhauled (hrs): 1180SMOH, 137STOH, IRAN/Reassembly by Tim’s Aircraft Engine
– Ignition:  Slick Mags
– Carb/FI:  AFP FI
– Exhaust system:  Vetterman 4-pipe
– Engine Purchased from: Private seller, eBay
– Engine Assembled by: Tim’s Aircraft Engines
– Date of last compression check: 8/8/2019
– – Cylinder #1: 76/80
– – Cylinder #2: 79/80
– – Cylinder #3: 78/80
– – Cylinder #4: 73/80
Other unique features FWF:
Superior cold-air sump
PCU5000X front-mount governor
10-row oil cooler
– Hartzell CS Blended Airfoil
– HC-C2YR-1BF Hub, F7496-2 blades
– Inspected, re-sealed, lubricated, and tested by Santa Monica Propeller 11/10/2010
– “B” suffix serial number- no eddy current inspection required
Flaps: Electric
Rudder Trim: none
Elevator Trim: Electric
Aileron Trim: Electric
Strobes Make/Model: Nova 606X
Landing Lights Make/Model: MR16 12v in wingtips
Age of tires/tubes: New tires, tubes from 2010, still good.
MGL Odyssey G2 EFIS
Garmin GNS430W
Garmin GTX3207 xpdr
Garmin GMA340 audio panel
MGL V6 radio
MGL Stratomaster Velocity 3″ MFD
Dynon Heated Pitot
MGL Serial port Expander
MGL IO Expander

Trio Gold Standard Servos, pitch and roll, integrated with EFIS

Interior: Classic Aero Aviator, gray/dark gray w full carpet
Modifications:  Koger sunshade
Real World Cruise Figures:
– 180 mph IAS at  23″ of MAP spinning  2300 rpm while burning 8.5 gph.

Past incidents/repairs/damage repair:
New rudder in 2019 from wind damage

Date last annual: 7/21/2019
– Maintained by: Me

Date last transponder check: 3/2/16
Date aircraft last flown: 9/29/2019
Willing to deliver: Maybe

Contact Info
– John Courte
– voice/text:  310-614-two five two four
– email: tangodelta313 at gmail dot com
– Preferred hours to call: 0800-2100 pacific time



2019 Condition inspection and other stuff

The condition inspection was the least fun I’ve had since the spilled-paint episode back when I painted the interior.  I rented a hangar at Compton, planning to spend the week before the SIGGRAPH conference getting most of the tasks out of the way.  The airplane itself only had a few minor squawks that I took care of, like the corrosion starting around the ELT antenna and a few things here and there requiring tightening or replacing.  Compressions were between 73/80 and 79/80.  No metal found in the oil filter, nothing really wrong that I could find.  What sucked was having to have four wisdom teeth pulled on the Tuesday of that week.  Cost me three days of work, that did.  Then, the wing jack slipped and ran a nice dent in the wing skin near the tie down point.   I cut an inspection hole  near it so I could keep an eye on it for later cracking, but it wasn’t a crease, so I filled it with micro and painted it.  After that I wised up and lifted the plane by the engine mount to get at the wheels.

I also recalibrated the fuel levels on the new RDAC, which was an onerous pain in the ass.  Drain the tank, transfer it to the other tank, drain 4 gallons at a time and put them in the empty tank, set fuel level, repeat.

Speaking of the RDAC, I finally noticed that my fuel pressure was stuck at 35psi, which is the maximum for that type of sensor.  I checked and rechecked all the grounds, redid the wiring, and eventually replaced the sensor, all to no avail.  That is because the manual for the RDAC makes no mention of the fact that when connecting to a MGL Odyssey G2 rather than the iEFIS unit, the fuel pressure sensor must be connected to AUX2 and not FUELP, which is where the RDAC installation manual says to connect it, and is the most obvious place.   The manual does make a provision for connecting the RDAC to an Odyssey EFIS, so it’s odd that this little factoid would be omitted.

All Together Now

Finally, after four months of interruptions, priorities, fragmented blocks of time, and truly awful weather, some of which begat the need for a new rudder, N313TD is back to operational status.

When I installed the new RDAC, I had to leave the left side CHG and EGT probes unconnected, because the wires wouldn’t reach the new RDAC location.  Yesterday, I ran the K-type extensions from both sets of probes to the new location and connected them accordingly, and as far as I know, they all go to the right terminals.  To truly test it out, I need to heat up the cylinder head and probes with a heat gun to find out which is which, but that’s not happening at a tie down in Santa Monica.   I know 1 and 3 are right.  It’s 2 and 4 that might not be.  You see, I ran the wires and wrapped them in spiral wrap before I thought to mark which was which.   The photo above shows a messy, but functional arrangement with enough extra wire to allow switching terminals, although I believe I can set them in the EFIS.  At that point, I can clean them up and make them all nice.  But for now, they’re secure and self-supporting, so I’m good.

The other thing that happened on the way to the new RDAC module was that I somehow picked up an extra 2500 ohms between the fuel tank and the Fuel Level inputs.  This new RDAC has a DIP switch for a pull-up circuit on most of the sensor inputs.  The manual says you’re supposed to have the pull-up on for float-type senders, but if it’s on, the resistance drops to zero and the fuel level reads full.  Not useful.

With the pull-up circuit off, ~8 gallons reads about 1500 ohms, according to the raw level reading in the EFIS.   One of my tanks is pretty much there, because I leveled the airplane and the fuel on the left side is juuuuuust touching the outboard rib of the tank.  So I half-assed it using the settings below until I can properly calibrate by emptying each tank and adding back 3.5 gallons at a time.   The gradations are from the previous measurements.

Opinions are strong on this, with most of them in the key of “you should use a totalizer and do the math” and “if you keep track of what you put in and the time you fly, you don’t need a gauge.”   But the saner voices acknowledge that fuel gauges are a good redundancy to a totalizer, and I tend to agree.  Either way, I now have everything I had before the old RDAC went tits-up, and then some.  #1 and #3 CHT’s aren’t randomly dropping out anymore, and the left-side fuel level doesn’t randomly jump from its normal reading to full tank.  The EFIS is still a mess.  I can’t get it to take the latest update and it can’t read any of the raster maps I’ve uploaded, and I’m getting pretty damn good at QGIS, so I’m not as happy with it as I should be.  But it’s still performing well for a 2010 unit that’s no longer being manufactured.

Did I mention I was doing this stuff outside at a tie down at SMO?  Yeah, about that.  No electricity, so no luxuries, specifically, no heat gun, which means yours truly was shrink-wrapping wire with a barbecue lighter and a cupped hand.

All repairs are field repairs, yo.   Can’t wait to install the Fed-mandated ADSB equipment before 2020.

New Rudder is On!

The new rudder is on, and the plane flies well. I think it may even fly a little better than before, but that could be a placebo effect. A couple of notes though:

  • The rod bearing distance measurements on the drawing referencing the inner surface of the spar is farking stupid. It means you have to subtract the thickness of the spar and doubler plates if you want to adjust your rod bearings using the accessible side of the spar as your starting point.
  • There’s also no way I can think of to get a 1/64″ accurate measurement of the rod bearing hole center to the spar without some weird contraption.
  • Salvage as much as possible from the old piece. In this case, I was only able to get the counterweight and the fairing attach strips, but it provided an excellent opportunity to practice drilling out rivets.
  • Use a plastic zip tie to cut out the excess pro seal from the rivet holes on the trailing edge before riveting. This works way better than it should and won’t scratch the work.

Once I actually got the parts and a solid block of time to work on it, it went really quickly. 10 years ago, I spent a lot of time puzzling things out and correcting mistakes. This time around, it was almost easy.

Rudder 3.0

It was easier to build new than repair the old one. Here are various stages – riveting skins to spar, and the dreaded trailing edge pro seal. Fortunately, I still have the drilled angle aluminum I used to do the last one, so of course it worked out fine.

Pro tip: use the end of a plastic zip tie to carve out the excess sealant that squeezes out into the dimples.


Foo bar bar

Rudder 3.0

This time around, I kind of know what I’m doing. I’ve done the stiffeners, removing the plastic, all that Jazz. The only part I was able to salvage from the old rudder was the counterweight, and this time, I know the order of riveting in such a way that I’m not fighting the counterweight to do the top rib.

Time To Fix Some Stuff.

For a while now, the MGL RDAC XD engine monitor module has been a little weird, mostly in the form of erratic oil pressure and temperature readings. To wit: Whenever the oil temperature would get above a certain point, the reading would bounce around all over the place, and the oil pressure reading would do the same, resulting in a low pressure warning. It’s very important that neither of those two lie to me, so I installed a steam gauge for the pressure. Oil pressure is solid on the steam gauge, no matter what shenanigans the temp and pressure sensors are up to.

The story so far…

Oh, that’s just a bad ground, you’ll say. Check your connections. Yeah, been there, done that. A lot. And it’s no use. A couple of weeks ago, I went for a nice flight after all the rain, and on takeoff from OXR, I had a complete failure of the RDAC module. Every measurement flashed “rdac fail.”

This, as you may imagine, was almost a code brown, at least until the RDAC came back to life, upon which I promptly flew back to SMO. Popped the cowl, checked the connections to the EFIS, to the grounding block, to all the things. Went for another flight. This time, the RDAC packed up over Malibu and didn’t come back. I flew home old-school, with only the sound of the engine (which I know by heart) as my RPM indicator.

Eventually, I made the connection: When the RDAC gets heat-soaked, it fails. It’s mounted on the firewall, which is extremely convenient because only a couple of wires go through the firewall port back to the panel. Unfortunately, it’s a harsher environment than I anticipated, and after less than 200 hours, I suspect the RDAC has succumbed to the heat and vibration of the engine compartment.

So now I have a job to do: Replace the RDAC, with MGL’s shiny new RDAC XF unit, and this time, don’t mount it low on the firewall where the engine radiates all the heat into it. And maybe, figure out some sort of enclosure for it to keep the worst of the engine’s emissions off it.

When I first installed the RDAC, I had no engine, no accessories, and no clue. I had a vast, untouched expanse of stainless steel where just about anything could go. Over the course of the build, the left side of the firewall got really crowded, and I think the logic was to avoid running data wires along the main power cable coming off the battery on the right-hand side. What we have is a job broken into two lists, for starters: stuff to buy and things to do.

Oh, and by the way, it’s time to start thinking about plumbing the mandated ADSB equipment for 2020. But that’s a whole ‘nother post.

To Buy:

  • CHT probes and wire (2x probes, 4x wire, steel crimp connectors)
  • EGT probes and wire (2X probes, 2x wire, steel crimp connectors)
  • Heat-resistant shrink tube
  • 3-wire shielded cable (+, -, and ground, plus shield). See http://spectrum-instruments.com/resources/documents/splicing_STP.pdf
  • 4″ SCEET tube (See the oil cooler scoop post, the tube’s getting ratty).
  • 1″ Fire sleeve for firewall port
  • 3″ Fire sleeve for cable wrap in firewall port
  • Aluminum Z-channel to mount new RDAC (this is a maybe)
  • Blast tube (look for this in the garage)
  • EZ-Up (to keep the sun off while working. Yeah, I park outside at SMO)
  • Fire barrier goop
  • Tarp/cover (in case I have to leave the cowl off overnight. Or for a whole damn week)

To Do:

  • Dismount Oil Cooler Scoop, gain access to old RDAC
  • Dismount CHT probes from 1 and 4 (these are the ones that work intermittently)
  • Dismount old RDAC, fill firewall holes
  • Mount new RDAC. Somehow.
  • Extend fuel flow wires to new RDAC location
  • Extend fuel pressure and oil pressure probe wires to new RDAC location (Do this at home)
  • Run and wrap all wires to new RDAC location (The existing Adel clamps will work)
  • Wire up new RDAC.
  • Remount Oil Cooler Scoop
  • Devise a way to keep the hose clamps from cutting up the SCEET tube
  • Install SCEET connection from baffle to cooler scoop (Do it right this time)
  • Test all connections!
  • Fly.

Oil Cooler – Day 5. Progress.

Today sucked a lot less than yesterday.  I got the oil cooler attached to the engine mount, which is a significant milestone.  I also learned that you can attach anything at any angle using this One Weird Trick, which I’ll describe later.

The oil cooler itself doesn’t weigh all that much, and there are no significant loads placed on it.  The attachment method is Adel clamps, which serve to isolate it from some of the engine’s vibration.  Given that, it seems that the beef I put into the brackets is unnecessary and an example of overengineering.  That said, it’s really, really important to me that the oil cooler stays firmly attached and that it retains its structural integrity until the end of time.

Forward Bracket - Oil Cooler

Forward Bracket – Oil Cooler

The  Weird Trick I mentioned earlier is shown below.  On the right of frame, there is a large-ish piece of angle connected to another angle bolted to the cooler.  The way this works is that there’s enough span on the opposite side to cover the distance needed  by two Adel clamps when the angle is laid up alongside the tube and the adjacent side lines up with the angle connected to the cooler.  This made for a much easier test-fitting, and the same technique is in use on the bracket shown above.

So it’s come to this.  The oil cooler is suspended where it needs to be to get air to it from the big hole in the baffle. At this point, the whole setup will take nearly my full weight, so I’m not terribly concerned about the parts failing.  At this point, the weakest parts are the flanges of the oil cooler itself, and they can be reinforced with angle or bent sheet.

This is the best fit possible for access, airflow, clearance from other important things (fuel line, for example).  There should also be enough room to get a  fiberglass intake plenum between the cooler and the middle engine mount tube.  I measured.  But “best fit” means the least hideous compromise.   Now for shaping the  plenum.  Yay, fiberglass.

Happy New Year.