Chronicling my Long EZ construction (and a few other things).
Disclaimer
This blog is for entertainment purposes only, and is not meant to teach you how to build anything. The author is not responsible for any accident, injury, or loss that occurs as a result of reading this blog. Read this blog at your own risk.
Making JT more… shall we say… weather-resistant, is going to require a couple more items, a heated Pitot tubeand an Alternate Static source. Today we'll look at the last one, and a few other things.
I have covered making heated Pitot tubes ad nauseam on this blog (heated Pitot and heated retractable Pitot), but just in case you came late to this party, a heated Pitot tube prevents icing of the super-important total air pressure port (static + dynamic pressures), while the Alternate Static source provides an ice free location inside the cockpit from where to get a static air pressure input.
The airspeed indicator mechanisms puts total air pressure on one side of a diaphragm and static pressure on the other, effectively subtracting the two. The result of this mechanical operation is dynamic pressure, which is independent of static pressure variations, such as during altitude changes or just day to day fluctuations. Because dynamic pressure's only variable is airspeed squared (if we regard air density a constant), an airspeed indicator really is just a pressure gauge marked in airspeed units (knots, mph, or kph) instead of pressure units (PSIs, millibars, or Pascals).
As in the case of the Pitot heat which can be selected ON or OFF, the Alternate Static source can be selected closed (normal operations) or open, if necessary.
Generic Pitot Static system with heated probe and Alternate Static source
Static probe icing is a lot less common problem than Pitot icing due the nearly insignificant profile of the static source, but because icing is still a possibility, and the installation of a backup source simple and inexpensive, we are going to tackle it now, while the panel is apart again due to other updates.
Getting pretty deep into it, again.
Before making any changes to the current plumbings though, we need to take stock of what we've got.
JT's plumbings before this update
A bit too many splits and too leak prone for my taste, this also makes it hard to follow and debug as necessary. I will replace most Y with a single manifold and run new hoses from it to the various “loads”. This manifold will be hanging upside down right behind F28 bulkhead, and due to its size I will have to machine a custom made click-bond out of a stainless steel bar.
My CNC Mini-Lathe will go through Stainless without any problems, albeit slowly.
Custom Click-Bond core threaded for 4-40
Finished Frankenstein Click-Bond
Proof that even a "Monster" can have a purpose
Click-Bond floxed to the top deck of the instrument bay
Manifold plumbed
Finding a location for the switch proved challenging, but I eventually settled on a location a bit out of sight (as it ought to be) on the left armrest.
Toggle valve protected and out of the way when closed
Here you can see a little better where the toggle valve is located
Landing gear lever
I like the idea of putting often used switches on the stick, but the nose gear retraction/extension switch has been a source of irritation from day one. Mind you, it has never failed to produce results, the problem is that it is too easily bumped into while getting in and out of the plane, or when working on it.
Current Nose Gear up/off/down switch
This always produces a lot of excitement at the worst of times, although not as much as if JT had three retractable legs instead of one.
After an extensive search for a three position locking toggle switch, the only place I could find who carried one was StainAir. This switch cost $72 plus shipping (😱), but it is much beefier than the original, and can no longer be accidentally activated. I chose a location right above the speed brake for it, since my left hand is always nearby while on the throttle.
Switch handle has to be lifted above the small lip before it can be moved
The switch came with no instructions, so the first order of the way was to sort out its electrical inner workings.
Reverse engineering the gear switch electricals
Next on the list was to 3D print a wheel to mount on the switch to make it look the part. A setscrew would hold it on.
ABS wheel
Setscrew on the bottom locks the wheel in place
New landing gear switch in its new location
Canopy’s latch
The switch worked really well, however I had not considered the fact that during gear operations the back of my hand would be in too close a proximity with the sharp edges of the canopy latch’s lever.
Nut and bolt sticking out
Back of my hand after one just takeoff and landing (next day)
After just one flight a new style handle had to be fashioned to minimize takeoff and landing induced "blood losses”
Latching lever removed from the plane
Sharp edges
CNC lathe at work. Facing, turning, drilling, reaming, boring, and edge radiusing operations were necessary to produce the new handle.
Old and new handle inserts
New handle is same height but slightly fatter, and sports a 10 degrees taper cut to match the original lever's dimensions.
All edges received a 0.050" radius
Hardware is now fully enclosed within the handle
Of course I had to go fly the plane in order to verify the installation, you know how important testing in actual conditions is 😁.
Alternator Circuit Breaker
Old Alternator CB. This place is now occupied by the new Landing Gear switch.
Yeah I know, but labeling it "Circuit Breaker for the Alternator Field input from the Voltage Regulator" would have used up all my remaining labels and most of the panel's free space. Given that this breaker effectively stops the production of electricity when pulled, I will consider it a way to turn the alternator ON or OFF, hence I shall label it just "Alternator".
But why would I ever want to disconnect the alternator from the electrical system in the first place, outside of an Emergency situation that is?
Marc Ausman, founder of Vertical Power, wrote the following in his excellent book “Aircraft Wiring Guide”…
“When the engine is OFF, and the alternator is ON, the voltage regulator sees low bus voltage (about 12.4 volts) and tries to raise the bus voltage to 14.2 volts by increasing the output to the field wire to its maximum capacity. Because the engine is not turning, nothing happens and the voltage stays at 12.4 volts while the voltage regulator is at maximum output, drawing about 4 amps of current. This also makes the alternator harder to turn and adds drag while the engine is starting (how much drag is added, I don’t know).
Based on this assessment, I don’t recommend turning on the alternator until after engine start. Get the engine running, then turn on the alternator, then turn on the avionic”
Because of Marc’s advice I've always pulled the Alternator CB after shutting down the engine, and pushed it back in after starting it, but it has occurred to me that I could replace it with a CB/switch combination, and stop having to pull on the tiny CB with my fingertips. Since I had already reused the old Alternator CB hole to install the new landing gear switch, I had to make another one further up on the panel.
Looks like the only place left for this CB/switch combo
Up is ON for all the switches. During an overload the switch trips back OFF on its own.
Rudder cable linkage
During last year’s roll servo installation, I machined a snag-resistant rudder cable linkage of my own design for the right rudder, which has proven itself effective and trouble free. As a result of this success, this year I made another one for the left side. The inner bushing are made on the lathe out of stainless steel, and space the two halves of the linkage just enough that the thimbles are no longer squeezed tight by the sides and are now free to articulate.
Not a big fan of this linkage, though it worked well enough thus far.
The thimbles get squeezed until they are unable to articulate.
The bolts stick out a bit much and could catch on the oil cooler fan assembly (not currently installed)
This design eliminates any edges that could catch on something
One side encloses the bolt head, the other the nut.
Each line represents a tool path, 5 tools were used.
Drilling relief holes for the bolt head's corners.
CNC Mini-Mill taking some pretty aggressive cuts
The two components roughed out of a 2.5" 2024 Aluminum bar
Not looking forward to the cleanup
Parts essentially done
After machining the bottom off, and making two stainless steel bushings.
New linkage in action
Hardware fully contained
Only one ¼" socket on the other side is required to take this assembly apart
Using this linkage I did loose the ability to lengthen the cable run, but since the rudder pedals were originally setup for JT's builder (Terry Lamp) who is in excess of six feet, I've actually always had the opposite problem, needing to shorten the cables as much as possible, and this linkage will work just fine for me.
