Empennage: Empennage attach.

This section had to wait 2 years until I had the space to complete it.  To start, I had to place 165 pounds from my weight set on the engine mount to keep the airframe from tipping back.  Even with that much weight up front, it only took about 20 pounds more on the tail, with everything mounted (stabs, rudder, fairings, etc.), to tip it.

Below is the only image I obtained of the horizontal stabilizer after match drilling it to the F-01411C Horizontal Stab Attach Bars.  It's important to keep the drill bit perpendicular to the parts and not let it chatter or wobble.  These holes need to provide a snug fit for the AN4 bolts.

My friend, who was helping me this week, and I decided to mount and match drill the elevators when the horizontal stab was on the aircraft, contrary to plans.  We felt that it would provide us more space to work with and help align things better.

It was found that the rolled leading edges were contacting both the HS-00903-1 Rear Spar and the HS-912 Hinge Brackets.  My friend spent some quality time massaging the edges into a shape to prevent this.  Recall, I was not pleased with how my rolled leading edges came out back in August 2014 when I rolled them and finally when they were riveted after being "re-rolled" by my friend in January 2016.

Next, the elevators were clamped into an in-trail position.

  

Following the plans with the "E drill bushing" (that bushing needed to be "turned down" on a drill press with sandpaper prior to getting a good fit into the bearing), I could match drill the left horn first (left).  Layering pieces of 0.020" aluminum strips provided for a good spacer.  The right side could then be match drilled in the same way.  Then both holes were upsized with a unibit to accommodate the AN4 bolt (right).  The washers necessary to prevent binding of the bearing are also visible.

My aft-most elevator horn was the right side.  So the hole was marked on that side first to accommodate the elevator pushrod (top left) then it was drilled to size (top right).  A spacer was fabricated, with a perpendicular hole pre-drilled, that was clamped in place to match drill the left horn (bottom left).  The spacer and its hole were important to ensure a perpendicular hole.  The horns could then be attached to the pushrod (bottom right).

Read Van's RV-14 Control Deflections Letter before adjusting control surface stops.  The horns contacted the F-01412C Deck Angle (which serves as the control surface stop in the "up" direction) prior to achieving the required full up deflection.  Quite a bit of it had to be filed away to accommodate the required travel.  I confirmed with Van's that this was acceptable:  "Your work as shown in your picture is perfectly acceptable. This angle is intended to be filed away to allow the appropriate elevator deflection."  Two other builders I contacted did something similar.

My elevator horns contact the Deck Angle simultaneously with the control stick stops in the upwards position.  In the downwards position, the control stick stops engage just prior to the control surface stop (the latter being the F-01411E Deck Doubler).  I have 29 degrees up and 24 degrees down elevator travel.  Were I do build another RV-14A (ha!), I would forgo the hours I put in filing down the control stops on page 36-13 until this step is reached.

I took the occasion of the elevators being attached to test the wiring of my pitch trim. It worked.

The vertical stab is then placed (left) and finally the rudder (right).

Rudder deflection is checked, left and right.  I am at 9/16" on both sides which is 3/16" short of the 3/4" spec.  This means I need to add offset tabs to achieve spec.

Empennage: Aft empennage. Match drilling vertical stabilizer.

The last step remaining for me to complete in Section 10 was the match drilling of the vertical stabilizer to the aft bulkhead.  I waited until I was ready to complete Section 11 to do this step, meaning it was delayed by 2 years.  I just needed more space.

Per the plans, it is critical to drill these holes perpendicular to the surface.  A friend of mine created for me a UHMW piece to aid in that process.  It keeps the bit trajectory true.  A well cut piece of wood with a hole drilled on a press would achieve the same result.

Once the holes are drilled, the stab can stand proud to negotiate the slipstream.

The above image also shows that the airframe has been moved to the other side of the garage.  This gives space to fully mount the tail to complete Sections 11 and 12 as well as mounting the engine and prop.

FWF: Spinner & Propeller. Spinner plate assembly.

The S-602-1 Spinner Plate and S-602B Doubler Ring are match drilled.

The center section of the Spinner Plate is removed via a combination of a multitude of holes made with a large unibit (left) and careful, though judicious, use of the Dremel (right), the latter of which was completed by my friend.  I attribute to "the 51% rule" that these parts aren't both pre-cut.

The parts are then primed with Napa 7220 and subsequently riveted together.

Panel: Airspeed indicator purchased.

I purchased my Winter 7 FMS 523 airspeed indicator.  It's a 360 degree, 2.25", 0-200 kts, zero up indicator.  I had them place the following markings.

• V_NE  200
• V_A   130
• V_FE  100
• V_X    70
• V_S1   62
• V_S0   51

A shot of the panel essentially complete.

Avionics: Nav/Strobe and landing/taxi lights circuit

Here are the posts pertaining to nav-strobe lights.

• 12-Aug-13, initial thoughts
• 17-Aug-13, lenses cut 
• 9-Sep-13, lights ordered
• 7-Jan-14, wiring completed
• 30-Apr-17, mounts fabricated 
• 16-May-18, first night flight

The navigation and strobe lights can be operated independently, as can the landing and taxi lights.  So there are four possible combinations to run them:

	Nav/Strobe	Landing/Taxi
1	Both off	Both off
2	Nav on. Strobe off.	Taxi on. Landing off.
3	Nav off. Strobe on.	Taxi off. Landing on.
4	Both on	Both on

I don't anticipate needing to use combination 3 (in red) for both sets of lights.  And, in the interest of consolidating panel space, I wish to control the remaining combinations, 1, 2 and 4 (in green), with only one switch for each light set.  An example of how to do that is shown below.

The diode is the key to this arrangement.  When the taxi light is selected, the diode prevents the landing light from being powered (option 2).  However, when the landing light is selected, the diode permits powering the taxi light (option 4).  In this way, one can select "off", "taxi" or "taxi+landing" with a single switch (or "off", "nav" or "nav+strobe").  The issue with using a diode is that its forward voltage drop causes heat generation when taxi+landing is selected.  This is especially an issue with a high current taxi light, like mine and a non-issue with the nav/strobe lights (due to their lower current demand).

Initially, I used a high current Schottky with a V_f  of 0.58 V (somehow I managed not to take a picture of that setup).  However, with the taxi light pulling 7.3 A when set to "high", that means the diode will create more than 4 W of heat.  And it sure did!  That was too much heat (again, this wasn't an issue with the nav/strobe lights since the navigation lights pulled only about 400 mA).

A more efficient approach would be to use a high-sided FET in a switching configuration, like shown below.  The PFET will only be switched on when its gate is effectively brought to ground.  This occurs when the landing light (or strobe) is powered on by the switch (not shown). When that happens, the NPN is switched on since V_BE>0.7 V.  With the transistor on, its V_CE is brought from +12 V to effectively ground.  With the FET's gate now at ground, V_GS is effectively -12 V, switching the FET on so that the +12 V at the source is now presented at the drain, where the taxi light is (or nav).  The taxi light (or nav) is then powered on with the landing light (or strobe).

Since R_DS for a FET is tiny (in my case, less than 0.004 Ohms!), there is a negligible amount of heat generated, even with more than 7 A being pulled through for a taxi light (which amounts to less than 30 mW of heat in the PFET).  Finally, a diode is placed to provide a path for the collapse of the magnetic field in case of any inductive reactance in the load (a.k.a., a flyback diode). 

With my planned approach determined, next I needed to design the circuit board appropriate for the OTTO K2 DPDT switch I planned to use (left).  I wanted my circuit board to plug in directly to the K2.  Here is a diagram I made to better show the K2's terminal connections (right).

My schematic is below.  It's a bit messy to present.  The K2 switch terminals are represented in the upper center.  Each K2 terminal needs a female tab so it can plug in to the switch.  In additional, each terminal needs a male tab to receive the wires (e.g., ground, power, landing and taxi or ground, power, nav and strobe).  The switch is DPDT, so that left and right lights can be on separate fuses (or wing and tail nav/strobes).  A single NPN transistor controls both the left and right PFETs.  In case the fuse blows on either side, the NPN is powered from both inputs, so a blown fuse will not result in the PFET changing its state and turning on or off a taxi light (and with 20 k-ohms between each powered input, neither side can power the other through that connection, should a fuse blow).  Finally, should the circuit fail, the lights are still controllable mechanically through the switch:  If a PFET remains off, then either lighting position can be selected, so either 'landing or taxi' or 'nav or strobe'.  If a PFET remains on then either 'taxi or landing+taxi' or 'nav or nav+strobe' can be selected.

Next I needed to design the circuit board so that I can just plug it in to the back of the K2 switch.  Using a micrometer and the K2 specs sheet, I mapped out the dimensions necessary.  Since space was limited due to the proximity of other switches on my panel (left), the board needed to be about the same width as the switch itself.  That criterion also necessitated using surface mount components.  The right image shows the board design.

Here are 3D rendered images of the board.

 

 

The boards were then manufactured.  The top image shows the front and back of the board (actually, the right board is an earlier revision, but it's similar enough to my final design).  The bottom images show the front (left) and back (right) after I soldered one up. The two red jumper wires were necessary since, when designing the board above, I ran out of room to lay down associated traces.  Lastly, the observant will notice that the PFETs are held down by LP4-3 rivets (hey, it's an airplane, right?).

And finally, here are two boards plugged in to the back of both my nav/strobe and landing light K2 switches.  After running the taxi+landing lights on for 15 minutes, the PFETs do not get noticeably warm (same for the nav/strobes, however they have much lower average current so it wasn't an issue).  Success!

As an aside, the wigwag line for my lights is active low.  Yet I wanted the panel switch to light up when wigwag was selected.  So I needed to use an independent rather than dependent light OTTO K1. To make sure the light turned on when wigwag was selected, I had to switch in the ground to the K1's light.  However, when the switch was off, the wigwag line would be connected to the ground of the K1's light.  Unfortunately, the wigwag line floated low enough to cause the OTTO K1 switch to illuminate slightly when wigwag was off (i.e., the landing light control line was sinking current from the switch's light).  Can't have that!  Hence the simple isolating Schottky diode on the switch.

In the above image, you can see that diode encased in a few layers of heat shrink tubing (it's the clear heat shrinked discrete on the ride side).  Below shows a representation of the circuit for the wigwag switch.  To ensure that wigwag line is pulled low enough when the switch is thrown, that diode I chose has a V_f of 450 mV.

For the curious, as in the case of when I designed my panel, I am a proponent of open-source software.  For schematic generation and board layout, I used KiCAD.  And there are a myriad of so-called "board houses" that manufacture circuit boards when provided with the CAD files for one's design.  Then it's just a matter of whipping out the soldering iron and affixing the components.

 

Parts list:

• Diode:  Kyocera AVX's SD1206S040S2R0
  
• PFET:  Infineon's IPP80P03P4L04AKSA2
• Quick Connect male:  Keystone Electronics' 4902
• Quick Connect female:  Keystone Electronics' 3528
• Resistor:  Panasonic's ERJ-8GEYJ103V
• Schottky diode:  On Semiconductor's 1N5817
• Transistor:  On Semiconductor's MMBT2222ALT1G