Gauges

AIS Markings

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Long ago I ordered some operating range decals from aircraftspruce.com so I can mark the air speed indicator. While the decals worked ok they are a little short. The more expensive decals they sell are full circles so no worries about being too short.

I needed more green than what is provided
I needed more green than what is provided

I labeled the stall speed with and without flaps, maximum speed with flaps extend, normal operating range, cautionary range and maximum speed. For three dollar decals they look very professional but you might need two of them to get the job done.

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AIS tubing

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The air speed indicator requires some tubing that goes to the pitot tube and static ports. Previously I wrote about the static port installation, you can read about that here. This article covers the tubing for the pitot tube. I decided to use the removable pitot tube kit, sold by Leading Edge Airfoils, so I can remove the pitot tube when removing the wings.

I thought that putting it out the leading edge of the wing would look nice, trouble is I already built the wings so installing is not going to be a simple task. I created two wood blocks, one to fit inside the wing just below the leading edge stringer and another to fit in the outside of the wing to support the pitot tube mount.

Pitot tube mount and blocks
Pitot tube mount and blocks

The inside block was threaded to match the pitot tube mount. I added CA glue to the wood as I tapped the threads to ensure the threads remain strong.

Pitot tube mount and blocks
Pitot tube mount and blocks

The only access hole in the leading edge is where the strut mounts are located so that’s where I decided to mount it. I cut a hole in the leading edge ply and epoxied the threaded block in place.

Pitot tube hole in leading edge
Pitot tube hole in leading edge

All of that was done about a year ago, now that the wing is covered in fabric and painted, time to finish. I first run the vinyl tube inside the leading edge from the root to the access hole. There I slid the tube through a 3/4″ deep well socket, then the plastic nut and out the threaded hole.

Pitot tube mount nut
Pitot tube mount nut
3/4 socket to tighten pitot mount nut
3/4 socket to tighten pitot mount nut
Vinyl hose for pitot tube
Vinyl hose for pitot tube

The outside wood spacer block was slid over the pitot tube mount and then the vinyl tube was slid over the barbs on the mount.

Pitot mount and external spacer
Pitot mount and external spacer

The mount was threaded into the wing, I had to ensure that the vinyl tube inside the leading edge was rotating too instead of rolling up into a knot. Now for the hard part, I used some long forceps to get the plastic nut started on the pitot mount. To tighten the nut I dig around my junk drawer and found the perfect tool, an old useless screwdriver. After a trip to the disc sander and vice it now looks like this.

Custom wrench
Custom wrench

My newly designed wrench fits into the hole on the side of the socket allowing me to turn the socket about 1/4 turn at a time.

Turning socket with wrench
Turning socket with wrench

I used my $20 USB endoscope camera hooked up to my phone so I could see if the nut was indeed fully tight.

Pitot mount nut tightened
Pitot mount nut tightened

I retrieved the socket using a magnetic pickup tool.

Retrieved socket with magnet
Retrieved socket with magnet

Next I made a plate to hold the quick disconnect.

Quick disconnect mounting plate
Quick disconnect mounting plate

Here I forgot to take a picture. Before I drilled that 5/8″ hole in the plate above, I had only drilled a small 1/16″ hole at the center. While chewing some gum I installed the wing so I could mark the center of the quick disconnect on the fuselage.

Tasty center finder
Tasty center finder

Grabbed the hole saw and drilled a hole in the fuselage side. 

Hole in fuselage for pitot disconnect
Hole in fuselage for pitot disconnect

The vinyl tubing was cut to length, disconnect plate varnished and disconnect installed.

Pitot quick disconnect on wing
Pitot quick disconnect on wing

The 90° disconnect inside the fuselage was attached to the vinyl tubing that runs up to the AIS.

Pitot quick disconnect inside fuselage
Pitot quick disconnect inside fuselage

I’m using the same valved disconnects I used for the fuel lines. So I don’t have to worry about bugs crawling inside my tubing and clogging it while I have the wings removed.
The final result looks great, hope it works well too!

Remove Before Flight!

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Various parts of the airplane need to be locked for safety or plugged to keep bugs/debris out when the airplane is parked and not in use. These locks and plugs are usually attached to a flag stating “Remove Before Flight.” I purchased some inexpensive, well made,  keychains for my flags.

Remove before flight keychain
Remove before flight keychain

The BRS ( aka ballistic parachute ) came with it’s own flag. This is for safety because you do not want to accidently activate it. It does not have ballistic in it’s name for show, that rocket needs treated like a loaded gun.

BRS remove before flight
BRS remove before flight

The static ports are used to measure atmospheric air pressure and are integral to the air speed indicator (AIS) and altimeter. I bent a small piece of music wire that attaches to the keychain and doors snuggly into the static port.

Remove before flight in static port
Remove before flight in static port

Maybe not necessary but seemed like a good idea I got a small rubber stopper and eye bolt to make a plug for the exhaust. 

Exhaust Remove Before Flight
Exhaust Remove Before Flight

The pitot tube, for the AIS, was a little more difficult to block because the tube can be removed. We not to plug the hole the tube goes in or the end of the tube when it’s installed. 

Drilled a hole in the side of a 1/4″ aluminum rod to attach the form.

aluminum rod for pitot flag
aluminum rod for pitot flag

The rod can easily plug the pitot holder.

Pitot mount and plug
Pitot mount and plug

Added a piece of 1/4″ ID tubing, this will be used to plug the tube when it is installed on the airplane.

Pitot Remove Before Flight flag
Pitot Remove Before Flight flag

With the pitot tube removed the hole is easily plugged and looks nice.

Pitot mount plugged with flag while pitot tube is removed
Pitot mount plugged with flag while pitot tube is removed

When the pitot tube is installed the same flag can plug the hole. The only downside is that it does add a couple inches to the length.

Pitot tube plugged with flag
Pitot tube plugged with flag

ADS-B in for $20

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ADS-B ( Automatic Dependant Surveillance Broadcast ) provides much needed information to pilots and air traffic controllers. ATC can see the location, speed and direction of any aircraft equipped with ADS-B out. Pilots can see other aircraft with ADS-B out and get updated information such as weather and temporary flight restrictions. Historically getting access to this data required expensive avionics but recently a few low cost solutions have appeared.

With some specialized software European USB TV tuners can pickup the ADS-B signals and thanks to mass production such devices can be purchased for under $20. I purchased a tuner that comes with an external antenna from Amazon.

NooElec SDR
NooElec SDR

Using a USB OTG cable I connected the tuner to my tablet.

USB OTG with charge cable
USB OTG with charge cable

I already had Avare installed and setup so I only needed to install ADSB Receiver Pro on my tablet. Now when using Avare I can see other aircraft and weather data.

Blue dots represent other aircraft
Blue dots represent other aircraft

If you need more detailed directions to get this setup head over to the site that made this possible: http://hiz.ch/index.php/home/adsb-receiver

The FAA has mandated that aircraft flying in nearly all controlled airspace must be equipped​ with ADS-B out by Jan 1st 2020. I hope this mandate helps drive some competition in the market and bring down prices of ADS-B out transponders. In the meantime at least I can pickup ADS-B in with little investment.

Wiring Engine Information System

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The EIS monitors the cylinder head temp, exhaust gas temp, RPM, battery voltage and air temperature. Each item can have limits set so if something is out of the ordinary the warning light on the dash will illuminate.

The cylinder head temperature probes sit between the sparkplugs and head. I ran the wires through the fins and up the side of the engine where they are held in place with a clamp. The exhaust gas temperature probe wire is also held by this same clip.

Cylinder head temperature probe wires run through fins
Cylinder head temperature probe wires run through fins
EGT and CGT probe wire secured with wire clamp
EGT and CGT probe wire secured with wire clamp

The probe wire then run to the front of the engine where another wire clamp was added.

EGT and CHT wires routed over starter
EGT and CHT wires routed over starter

The EIS harness terminates in from of the battery where the probes are connected. I kept the pair of wires for the second exhaust gas probe in the harness even tho I’m not using them. Maybe some day this airplane is updated to two cylinder and then they are needed.

EGT and CGT connected to EIS harness
EGT and CGT connected to EIS harness

The grey  tachometer wire goes to the other side of the engine and connects to the lighting coil. I spliced an extra connector into the voltage regulator wires to connect the tach input. Still need to put an end on the grey tach wire.

Lighting coil & tach connection
Lighting coil & tach connection

The EIS uses a single DB-25 connector for all the wires. I took the connector apart and removed all of the unused wires by pushing the pins out with needle nose pliers. A few of the wires exit the EIS harness just behind the connector such as power, ground, fuel sender and warning light.

EIS connector
EIS connector

The violet wire runs through the harness to the warning light with the other side of the warning light is connected to power. I made sure that the dash is easily removed by disconnecting wires as opposed to having to cut wires to remove it.

EIS warning light
EIS warning light

The last item to connect is the green wire to the fuel level sending units from the gas tanks. When it gets a little warmer I’ll roll her outside, mount the wings and tanks and then work on routing the fuel sensor wires. I’m not exactly sure where everything ends up so not much I can do with that for now.

Fuel Gauge

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Started working on the electrical wiring and discovered that the EIS 2000 I have only supports a single fuel level input. They sell the EIS 2000 as a two or four stroke model when in reality it does not matter if you have a two or four stroke the difference between the two models is features not engine type. When I build the next airplane I think I will build my own EIS or use the flybox.

So the Grand Rapids folks suggested using a switch so I can select what tank level I want to monitor. After thinking about this for some time I decided this is the best option but that it needs to be implemented carefully. Imagine monitoring the full tank but running the engine from the empty tank. That could result in a bad day. 

In designing this I decided the goals should be as follows: 

  1. The position of the tank selector valve dictates what fuel tank is monitored by the EIS
  2. If the fuel selector valve is in the off position then the EIS should see an empty tank triggering the warning 

The typical inexpensive fuel selector valve is not suitable for triggering some electrical switches. I ended up purchasing a WSM 006-600 jet ski fuel valve on Amazon.com and a couple of 2750017 micro switches from the local RadioShack. 

Fuel valve and micro switches
Fuel valve and micro switches

Using a file I put a flat spot on the knob that was parallel to the flat side of the D hole in the knob. The location of the flat spot is important so if you have a different valve you might need to change the location.

Fuel valve knob modified with notch
Fuel valve knob modified with notch

When the knob is installed on the valve the flat spot should line up with a micro switch roller only when the valve is turned to the left or right tank. This will require the switches to be mounted 180° from one another. I used OnShape.com to make a drawing that I printed out in reverse on toner transfer paper. This will provide accurate centers for the holes and the labels for the valve. 

Putting the switches to their marked locations on the toner transfer paper you can get an idea of how this will work. 

Arrangement of micro switches
Arrangement of micro switches

I varnished a piece of plywood, sanded it smooth and applied the toner transfer. Then the parts were cut out and drilled. A smaller valve support plate needs to be 5/8″ away from the panel so the notch in the knob is just below the plywood. 

Micro switch actuated by notch
Micro switch actuated by notch

On the outside, for asthetics I used 1/4″ X 3/4″ pine. A 1/8″ notch was cut into the outside piece and the valve support set into the notch. The inboard side used a small piece of 1/4″ X 5/8″ pine. Alignment is important so I glued this together with the valve and knob installed to keep everything indexed.

Fuel valve support
Fuel valve support

Once the epoxy cured the switches were mounted using #3 screws and the valve installed. 

Fuel valve, switches and wiring
Fuel valve, switches and wiring
Fuel selector knob and labeled panel
Fuel selector knob and labeled panel

The electrical wiring did take a little bit of planning. I wanted to make sure that should there ever be a malfunction that only a single fuel level sensor would be connected to the EIS. Here is the wiring diagram that does this: 
http://schematics.com/embed/fuel-sender-selector-46440/full

Before takeoff simply turning the valve to all three positions will confirm if the system is functioning properly.

I think this turned out well, looks pretty good mounted on the fuselage side. 

Fuel tank selector valve
Fuel tank selector valve

Toner Transfer

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I’m still not happy with the dash so time for the fourth iteration. This time I designed it in CAD using OnShape.com, including all of the labels. To fabricate it and apply labels I thought using a tuner transfer method might be nice.

First the wood was vanished and sanded smooth. I only had A4 size toner transfer paper so I had to print multiple pages to cover the whole dash. PosteRazor was very helpful in printing the pages, just don’t forget to mirror your CAD image before printing.

Starting with the center bottom page I taped it to the board and used the wife’s iron to transfer the toner. To align the next page I pushed T-pins into various reference points.

Pins to mark index locations
Pins to mark index locations

Those same reference points were poked through the paper.

Pins to mark index locations
Pins to mark index locations

Then using the holes the next page was aligned using multiple reference points.

Aligning the transfer paper
Aligning the transfer paper

Then the page was tapped in place and toner transferred with the iron. This process was repeated until the whole dash was completed. The nice thing is if you mess up just sand off the mistake and try again!

Since all the holes were marked with toner it was really easy to cut out all of the holes precisely where I wanted then.

Toner transfer also marked hole locations
Toner transfer also marked hole locations

I might want to add some more text or switches before I complete the airplane so for now I am leaving off the final coat of varnish. But once completed I plan to add a couple of coats to help protect the toner from abrasion.

Preview of final dash
Preview of final dash

I recently started working on the electrical wiring and quickly discovered that most 12v USB phone chargers emit RF interference like crazy. When tuned to around 132Mhz the interference makes reception impossible. Anyone know of a decent priced charger that does not emit tons of RF?

Dashboard Take Three

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Lurking on ETLB forum I stumbled across a post from Brian about his V-Max dash that had some rubber insulators between the fuselage and the dash. Makes sense to me, reducing the amount of engine vibration that reaches the gauges is a good thing. So I decided to do the same thing.  Ordered some rubber vibration isolation mounts.

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Vibration isolators

These isolators have M5 threads and are about 5/8″ in diameter. The rubber section is also about 5/8″ high.

Next I created three triangular brackets using some RS-1 and 1/8″ plywood. 

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Dashboard Bracket

The dash panel is attached to the brackets using two bolts. By using bolts I can easily replace the dash panel in the future should I ever install different gauges.

The most important thing to remember is that the dash panel and anything attached to it must not touch any part of the airplane. Any wiring or tubing that is attached must be loose and free otherwise it will transmit vibrations to the dash.

Because of that I mounted the trim adjuster to the fuselage using an aluminum bracket, this way vibrations are not transmitted to the dash through the stiff cable.

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Pitch trim adjuster bracket

Since the dash is angled I made a shim so the adjuster can be mounted at the same angle.

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Pitch trim shim

The notch is to clear the front spar carry through bolt.

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Pitch trim adjuster

The hole is the dash is made about 1/4″ diameter larger than the adjuster knob so it does not touch the dash.

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Clearance for pitch trim

Mounting the dash this way will make it easier to inspect and maintain these components.

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Rear of dash panel

On the right side the bolts holding the EIS in place are also used to attach the dash panel to the bracket.

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The final result looks great.

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Completed dash

Now I just need to take it all apart so I can varnish the panel and brackets.

Mounting the Radio

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After sitting in the cockpit trying different locations I decided to mount the radio on the dash. I had to make a small spacer of 1/8″ ply because the back of the radio is recessed where the screws are located.

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Spacer for radio
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Back of radio

It fits well in this location with the modified Yaesu adapter I made.

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Radio mounted

This location did block one of the two switches I had on the dash and the one unblocked switch cannot have a cover because the radio adapter keeps the cover from opening. I plan to enlarge the blocked switch hole to feed the radio wires through the dash. I’m undecided on what I want to do about switches. I really only need one switch but if my generator fails it would be nice to be able to turn off non-essentials to preserve battery power.

At this time I will go with just one switch next to the starter key. The dash is looking really nice so far.

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MiniMax dash with radio mounted

Static Ports

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Before covering the tail section of the fuselage I thought it would be a good idea to build some static ports and run the tubing. The flight manual says to put the static ports in the center of the diagonal between stations six and seven.

I cut a 3/4″ cube from some scrap wood and drilled a 19/64″ hole through the center. Then used a 11/32 to drill nearly all the way through leaving about 1/8″ of the 19/64″ hole.

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Static port block

I then put some CA ( super glue ) on the 19/64″ portion of the hole. Once dry I run a 1/8-27 NPT tap through the hole. As the tap cut I would remove it, add more CA, let it dry and then tap a little deeper. The end result is some nice strong threads in the block.

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Static port block with threads

Next I cut a 1 1/2″ square piece of 1/8″ plywood and drilled a 19/64″ hole in the center.

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Static port base

Next I used the 19/64″ drill bit to line up the block and plywood to glue them together.

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Now the hose adapter can be installed so you can get an idea of the final result.

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Static port assembly
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Static port assembly

The plug on the outside is some fastener I found at the local hardware store. To make them useful I drilled a 1/16″ hole in the center.

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1/16" hole for static port

I glued the assembly in the center of the diagonal between stations six and seven.

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Attached static port to fuselage

Once the glue was set I vanished the exposed wood then started running the tubing. I put a tee between the two ports.

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Static port tee and tubing

Drilled a hole in the elevator cable bracket on station six to hold the tubing.

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Tubing support

Did the same at station five and a hole was drilled in station four directly under the left rudder cable.

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Tubing support

Another hole was drilled in the seat support directly above the elevator trim cable.

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The tube follows the same path as the trim cable up behind the instruments. I did not connect it to the instruments yet because I have not decided on the exact routing behind the dash so no pictures of that. The plan is to add tee so it can be connected to the air speed indicator and altimeter.