tailwheels

Unintended Adventures

Tag: Avionics

So Close

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On December 31, 2018

In S-20

Not much exciting things to show since the wings went on. It has been a lot of wiring to wrap up the avionics and also to get the engine wired up. But, that is coming to a potential end and I wanted to get something written down before the end of the year.

(If you’re reading this on the 31st of December 2018, there are no pictures because my iPhone doesn’t like to be below 30% battery when it is 32 deg F or below. I’ll get some photos tomorrow and add them to the post.)

The avionics wiring is complete. I will make the wire runs a little prettier, but all the wires go to what they need to go to and nothing exploded. The wiring for the engine is almost complete. Currently I am working on finishing the wiring for the ignition/mag switch which will complete my engine wiring.

Hoses on the engine have been a not so fun endeavor. The hoses that are giving me problems are the oil hoses and specifically the hose from the oil pump housing to the oil cooler. The provided hose does not lend itself to any sort of acceptable routing and I fussed with it over the course of a few weeks before giving it up. I will have to make my own hose for that run, but I have put it off to accomplish some other tasks I had put off previously. I’m not sure if it was in a previous update, but I fabricated a hose to go from the firewall bulkhead fuel fitting to the gascolator and installed the Rotax fuel hose to the gascolator. I still need to install the return line fuel hose and the fuel pump vent hose. I also will make a vent tube similar to the oil tank breather vent for the fuel pump vent.

I was fitting up the radiator duct a while ago and realized I needed to install the oil hoses which led to me figuring out the fun in the paragraph above, so it is currently waiting for me to finalize the hoses. Something that came up with another builder is making an access panel in the radiator duct so the oil hose at the bottom of the engine can be accessed without removing the duct. It sounds like a good idea and I need to get some aluminum to accomplish that.

Probably should have put this sooner, but I installed the oil tank mount brackets. These are what sort of cradle the oil tank and get riveted to the engine mount. I hope to never have to remove those rivets. The manual calls for the use of pan head screws, but I had a hard time tightening the nut on and replaced them with some hex head bolts which worked fine. One thing spotted by someone else was that the heads of the screws or bolts will touch the oil tank. By using some plastic edging material on the aluminum angles, the tank is offset enough to avoid this. 

Another big item was finally diving into the header tank. I had put it off for a year and then bought an updated version from RANS and then put if off for another few months. I installed all the fittings into the tank, installed the mount for the new header tank. I also added a piece of aluminum angle to the read of the mount for added strength since the forward attach locations didn’t do much for the aft part of the tank and it will be relatively heavy with fuel in it. I also had to relocate the tank sump location. I marked it and then cut through the fabric. What I should have done is fabricated a new exit ring, glued it where I wanted the hole, and then cut the hole. Now I will fabricate the ring and glue it, but I probably could have gotten a better finish by doing it differently. I patched over the old opening with some extra fabric from cutting out some inspection cover holes. I still need to run the fuel lines from the wing tanks and to the firewall.

I final installed the flap lever. This was frustrating because somethings are off center and require some odd washer placement. There are also bushings to be fabricated and I don’t have a great way for getting those cut perfect, so I end up putting them on and taking them off a lot. In the end I added some washers as well because the right rod end would hit the fuselage frame when I tried to move it to the last detent. I added washers to center the cables better and avoided this. It is still close, so I may file some of it away to provide better clearance. The material that would be filed away is not a structural tube, so I think it will be safe to do.

Things that are up on the list are installing the jury struts, installing flap gap seal, rigging the wing (and control surfaces), finalizing the oil hose issue, installing fuel return/pump vent hoses, and finalizing the routing of wiring on the firewall forward side. 

My engine monitor has also progressed quite a bit. I had thought my software was in a pretty good place and then I installed it into the panel and found some bugs in the data acquisition and sensor conversion code. I fixed those and now my only issue is not understanding how to auto start the application after booting and I need to integrate a real time clock into the board so it actually keeps track of the date and time. The latter should be the easier one to fix and I just placed an order for an updated PCB.

In related aerospace news, I am finally graduated from Iowa State with a B.S. in Aerospace Engineering! It was a crazy 3.5 years to get to this point and it took  lot of hard work. A lot of thanks goes to Maria for agreeing and supporting more school. I also owe a lot to all the friends who shared the misery of engineering school and the large group projects that accompany it. It was a ton of fun to go back to school and intern with some exciting companies. I’m looking forward to a fun career.

I learned a lot of new stuff that has guided me toward some neat projects that I am hoping will turn into big things. I am really interested in manufacturing composites and hopefully some structural composites as well in addition to making parts from metals and plastics. I’d like to think I could make a business out of it at some point, but there is a lot of learning and tool acquisition required before that point. I have some neat ideas for upgrades to the RANS and also some standalone ideas, but they will have to wait till the RANS is actually flying.

(40 h)

Mad dash to the finish

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On September 5, 2018

In S-20

The summer for students has come to an end and I’m back in Iowa. Summer job was fun, I learned a lot, and met some great people. Alas, it is now time for airplane building once again. A lot happened since the last update in March, so I’ll try to cover all of it.

I made a crazy work week before leaving for Denver in May to get a lot of stuff done. I accomplsihed most of what I wanted to do. I mounted the ailerons/flaps, fitted up the windshield, completed the second seat (that had been waiting since Thanksgiving of 2016), and prepped the hangar in case I got a hangar spot closer to home. The last bit did happen which was great. The plane now resides a mere 15 minutes from home compared to the 55 minutes it was for the last year. Still not quite as good as just being in the garage, but it’s too big now anyways. This should allow me to get a lot done on the plane these next 4-6 months (or until I convince someone to give me a job 🙂 ). I only have one class to finish up my fancy-pants degree and I will be doing some flight instruction, but I should be able to go full airplane build mode for most of the time.

The second great news is that we finally committed to finish the project and have purchased the avionics and the engine. The plane will use a Rotax 912ULS (100HP) engine. I started to become nervous about this before the decision since there was and still may be a chance we will move to higher elevations. The Rotax 914 would be the safest bet and make an awesome airplane, but in the end I couldn’t find any reason at this point in our lives to drop another $11k-13k on an engine to get a turbocharger. Maybe the next plane or when this 912 gives up.

The avionics are pretty bare bones. I’ll go into more depth when I get to wiring stuff, but I’ll have a Garmin G5 for primary flight information, a Appareo ESG transponder (RST Engineering has a great deal for EAA/AOPA), a Garming GTR200 radio, and my homegrown engine monitor (also looking at purchasing something from MGL as a backup and to reduce the risk that my engine monitor doesn’t want to work; I don’t want to delay flight testing for an engine monitor). The wingtip lights are the AeroLEDs Pulsar NSP variety. The other big (maybe controversial) decision was to forgo circuit breakers for most of the electronics. I will be using fuses for all of the equipment in the plane and then circuit breakers for the master and generator circuits. With my desire to fiddle with electronics, I couldn’t devise a plan that would let me hack the electrical system as easy as having banks of fuses with available slots. More to come as I get into wiring.

As I get further into the build, I find I have less and less to say about the specific tasks I’m doing. I wish I had more to say to help others, but I have been putting off writing these for too long after doing the tasks. I hope to change that moving forward.

One thing I will say about the boot cowl sides. For us tailwheel builders, you have a choice. You can either install the boot cowl sides with the gear off or you can trim the boot cowl sides to go around the gear blocks. I did the latter and ended up trimming off too much of the boot cowl and now I have a gap. I plan on getting some thin aluminum to extend the area I trimmed and make it a more flush finish with the fuselage. So if you’re tailwheel and don’t want to remove the gear to install the boot cowl, go very slow and check often. I think it would have gone better with another person to help me hold the boot cowl up and check interference. With only two hands, it gets difficult to check and trim quickly.

Some other small items being completed are on the firewall. This includes the battery box build up, and mounting the coolant overflow bottle. I had a very annoying spat with some stainless steel rivets on the battery box. The stem would pull completely out of the rivet on most of my attempts. I took a break, ordered some more rivets, and used some rivet backing washers. That solved the issue. Not sure what was wrong, but my casual internet reading (very dangerous) leads me to believe it may have been the rivets themselves, but I don’t know enough to say how much belief to put into that thought.

In general shop news, after 3.5 years of building I finally bought some shelves and a work table to supplement a small workbench. Not sure why I didn’t do it sooner, but I was younger then 🙂

The panel is off to the laser cutter in town and some more orders to Spruce and Digikey are inbound. I’ve attached a picture of the cutouts I’m making for the panel. Hopefully it works well. I think I could do much better from a human factors stand point, but we shall find out when it is flying.

I’ve been adding to this for a few weeks, so I’m pushing it out and I’ll be getting some more updates in the coming few days.

Long time no update

By

On January 7, 2018

In S-20

The Spring 2018 semester is almost ready to start. This weekend I will be wrapping up some painting for my rudder, doors, and a few fairings around the tail area.

Not much work was done over the Fall mainly because of me taking on quite a few projects at school. Sort of depressing, but projects are good and they provide me with things to talk about during interviews when I’m not talking about the RANS :-).

The big task going on since the last update is painting. Although it has only taken place over two weekends, that is the big project for the last 4 months. I finally painted the landing gear and as mentioned above will have completed the rudder and doors. The bigger task before that was completing the door trim. That was a fussy task, but as with all other things, it has passed. If you have questions or want some tips, get in touch with me. I would like to write a detailed process, but it was messy haha.

Other little things were getting the tail brace wires installed, some hardware installed on the ailerons, attaching some interior fabric, and starting to fit up the wing tips.

In other big kit news, I ordered the firewall forward kit back in mid-November. I’m hoping that will keep me busy for a while. I will be out of town for 3 months over the summer, so I won’t have any airplane work going on although I do plan on working with some of my electronic projects.

On the electronics side, the Engine Monitor software is pretty much where I’d like it. It is really ready for some higher level testing. I’m preparing for this by working on some circuits to help protect the electronics from voltage surges and other things.

For some new ideas, I am beginning to toy with some components that would provide a means for an electronic circuit breaker and provide current monitoring for individual loads. My idea is to somewhat emulate other commercial offerings that provide electronic circuit breakers. I’m going to go slow with this one and test as much as I can. Even if I do put it in the airplane, I am planning on some standard fail safe circuit protection devices.

Here is an example of the circuit that I am going to play around with for the circuit breaker. The green line in the graph shows a simulated current draw. The system senses a voltage drop across a resistor. By changing the value of that resistor, the device will trip at the specified current. This example is using a resistor that should trip at 2A. The simulation shows it being tripped at 1.8A, which is caused by an additional resistor on on of the sensing pins of the chip. I need to do some researching on why they have used a resistor in that location.

Example current trip.PNG

Busy Fall

By

On December 5, 2016

In S-20

The airplane is still progressing. I voted to work on the plane vs. write an update after each work period.

Since the last plane update, the right wing has had all patches, tapes, and exit rings attached. In addition, the brushed on coat of EkoFill was applied.

The next step is to get the left wing mounted and prepped to cover. This will entail cleaning all the dust and bugs off the frame, applying anti-chafe tape to sharp edges, and getting the fuel cap screws sealed up. Then we will get it mounted into the rotating stand and get to covering.

A few things that I found from last time will hopefully make this wing go better. First is the coat of glue applied to the root skins and the leading edge skin. On the right wing I used a normal brush and I got a lot of bubbles and streaks. This will definitely show through the paint, but I wasn’t too concerned with it since I think it will not detract from the look overall. My options for the left wing are thinning the EkoBond down, using a different brush, or forgoing the coat of glue all together (need to call Stewart’s on this one). Hopefully that will eliminate the bubbles.

The engine monitor project is coming along pretty well. Not much to show at the moment since I’m just coding (very slowly due to a lot of work and school), but I’ve started adapting a configuration file so the limits of the gauges will be configurable. My coding as of now is geared towards the Rotax 912ULS, but I’m trying to keep it as configurable as I can where it is somewhat simple. If this thing keeps moving on and someone else wants to use it with another engine, then I figure we can cross that bridge then. I did find a new source for a lot of bright, industrial screens. They are pricier than the other outlets I found and the smallest screen seems to be 8.4″. Not a deal breaker overall, but I don’t know if an engine monitor needs to be 8″. I found a 6.5″ screen for around $140. It’s not the brightest, but it is close to the requirements I had decided on and some of the soaring community are using it with apparently good results.

(12 h)

A student’s approach to avionics

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On October 22, 2016

In S-20

Pretty excited at the moment. I think I’m actually going to get this engine monitor project off the ground and it will look nice as well.

If you recall my last posting I kind of talked about that I was going to limit myself to simple displays powered by an Arduino because I was having trouble finding a way to create a GUI on the Raspberry Pi. I resigned myself to pixely LCD displays and figured I would start looking for one to buy until a magical moment when I was searching Google for a display and with a combination of search terms I ended up on a search page on SourceForge. SourceForge is a website that can serve as a repository for software projects and sharing those projects.

Wouldn’t you know that I stumbled upon a really cool project that mimicked exactly what I wanted to do and it even used some tools that I had looked at before I gave up. The picture below shows the display that was created. If your into software I encourage you to check it out. You can find it at (https://sourceforge.net/projects/enginemon/). It looks to be a great jumping off point for my project and I think we’ll end up with something very cool.

So after discovering the code I set off getting my Raspberry Pi setup to run it. It wasn’t too hard and there were much fewer headaches then the path I had started down a few weeks ago. I got it running and then decided to try interfacing the Pi and the Arduino. That took a little time, but I used a quick tutorial I found online and I got it working. The video below shows me turning on an LED on the Arduino using a program running on the Raspberry Pi. The method of communicating back and forth is what I’ll use to transmit values received from sensors by the Arduino to the Raspberry Pi.

The current thought is to house the Arduino itself as a standalone sensor box and then the RPi will be housed with or near the display and use some wires to connect to the Arduino. That way I won’t have too massive of a box hanging off the back of the panel.

I also found a 6.5″ screen that is being used by some glider pilots running an open source glider computer. They seem to have good luck with reading it in direct sunlight and they see more sunlight more often than a normal plane. The nice thing too is that the display is relatively inexpensive, so if it doesn’t work as well or I find a brighter one it should be a trivial process to change out the displays.

(3 h)

Riveting

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On October 13, 2016

In S-20

Little late, but wanted to get a short note written to just stay on top of the log.

Last weekend was devoted to getting the fabric on the right wing riveted down. I thought it would be fairly quick, but as usual it was not. Nothing hard for this part, but just a lot of repetition. The plastic strips all laid down nicely and seemed to go better than when I was using the strips on the horizontal stabilizer.

Maria helped out with the riveting and we got it done pretty quick. It was a quick work day, but now we’re all set to start adding exit rings, patches, and tapes.

On an aside, I have started on a side project to attempt some simple avionics. I really like the systems produced by Dynon and Garmin, but I’m haven’t been able to fully commit myself to one for this airplane. The information that I really am interested in is engine data and specifically temperatures. My idea is to use a popular micro controller (Arduino) to interface with the thermocouples and then display this data on a small screen. The end goal would be then to use the power of 3D printing to make a case for the system and be able to mount it in the panel.

I’ve looked into also using a small Linux computer (Raspberry Pi) in order to get access to nicer displays and graphics, but my lack of GUI programming has limited that area. I have a Raspberry Pi, so I may try to figure something out, but the Arduino is a relatively simple platform with a lot of community support for sensor applications.

If anyone reads this and has questions or has done this sort of thing shoot me an email. Should be a fun project and lower my desire for a full-blown glass cockpit. I’m going to add this stuff to the avionics page on the blog and try and track some progress there.

(5 h)

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