Avionics Bending: Mechanical Synchro Signal Producer (Part 4)

Mechanical Digital to Synchro Assembly

Here is the first design draft of the mechanical digital to synchro converter. The stepper motor on the bottom turns the Synchro Transmitter on the top of the design. The gear ration between the NEMA 17 motor and the Synchro should allow for very fine adjustment of the Synchro. The next rendering shows the the top plate and the Synchro Transmitter removed.

Mechanical Digital to Synchro Assembly

The picture below shows the assembly with the holder on the left hand side for the optical zero detection.

Mechanical Digital to Synchro Assembly

Another view of the prototype assembly from below. Here you can see the cutout for the NEMA 17 motor.

Mechanical Digital to Synchro Assembly

The entire assembly will be 3D printable. I will print the first prototype in PLA and then see how rigid the design is. The next step will be to add the design for the Beagle Bone Black holder and the 400Hz 26VAC  connections into the design.

Mechanical Digital to Synchro Assembly

Avionics Bending: Mechanical Synchro Signal Producer (Part 3)

L-1011 Project - Mechanical Synchro Converter

Modeled the motor and synchro components to go into the design. Here is how I currently envision the device to work .... it's actually quite simple. Above is a block diagram of initial idea for the device.

Let's take an example of the Airspeed indicator:

1. The device initializes by rotating the assembly until Zero Detection is reached. We have now stablished the starting point. 
2. Indicated Airspeed (IAS) is sent from X-Plane via UDP across the Ethernet to the Beagle Bone Black (BBB). 
3. The BBB translates the airspeed into angular information around the airspeed indicator dial. 
4. The BBB instructs the Stepper Motor Controller to move a computed number of steps forward or backwards. 
5. The linked Synchro Transmitter takes a 26V 400Hz input sources and creates the 3 Phase Synchro output needed by the L-1011 Airspeed Indicator. 

Avionics Bending: Mechanical Synchro Signal Producer (Part 2)

Mechanical Digital to Synchro Converter - Modular Mounting Plate Back

Mechanical Digital to Synchro Converter - Modular Mounting Plate Front

Working on the design of the motor mounting plate for the Stepper and the Synchro. This modular plate should accommodate a single stepper motor and a single Synchro Control Transmitter. The modular motor holder. I am also working on an alternate design that can accommodate the Coarse and Fine CTX for Altitude encoding. 

Once getting closer to a more practical design of the holder I will make it available as an Open Hardware project. 

Avionics Bending: Mechanical Synchro Signal Producer (Part 1)

Components for the initial Synchro Transmitter Controller

Today, I am embarking on a project to build a mechanical Digital to Synchro converter. Digital to Synchro converters are, of course, available in the form of very very expensive solid state devices form companies like DDC or other. However, for the L-1011 project I don't have the financial resources to purchase several of these devices to address all of my synchro signal needs. If you remember, synchro transmitters produce a 3 phase signal that is created form a single 400Hz 26V AC reference signal. The 3 phase shifted signals encode the angle of the synchro shaft. This technology has been around for a very long time and was, and in many cases still is, the standard for transmitting shaft angle between components.

For example, on the L-1011 the airspeed indicator and the mach number are both transmitted form the transducers to the cockpit instruments as 3 phase synchro signals. If you want to read more about Synchro Transmitter, like the ones I will be using to build this first prototype with, you can read about them here.

To build this first prototype idea I will create a mechanism for a stepper motor to drive a synchro transmitter. I will print the components using my Makerbot 3D printer and since none of the components need too much rigidity for the initial testing I will print them in PLA. I will use a Be able Bone Black as a way to drive the stepper motor and to read the Zero point on the Synchro. My initial idea is to zero the synch by using an indexer on the synchro gear.

PLA printed Synchro Gear with Indexer

The plan is to read the index with an optical switch.

I picked a NEMA 17 stepper motor not because they are needed to drive a tiny little synchro ... they are really an overkill and rather large ... but because I bought 50 of them for close to nothing on eBay.

I would very much like to make this an Open Hardware project and would like to invite you to participate in it. I am drawing the components in Autodesk Fusion 360. Please send an e-mail to curdzechmeister@gmail.com and I will add you to the Fusion 360 project.

L-1011 Trainer Installation: Flight Director Integration Tests

L-1011 Flight Director Integration Tests

The ADIs in the L-1011 simulator incorporate Flight Director (FD) bars for Pitch, Roll and Yaw. Today I worked on moving Flight Director information from X-Plane to the ADIs. To do so, I am using ARNIC 429 Label 170, 171 and 172. The Flight Director bus is a slow speed bus and FD information is passed to the ADI at 12.5Kbps. For the first few tests tonight I focused on the roll and pitch data. X-Plane actually does not have Flight Director data for guided yaw, however, that information can be derived from a number of other X-Plane data points.

The video below is a short demo of a Flight Director guided roll to the left to heading 225 and then we see a flight director guided roll-out at the target heading. Watch the HSI and the ADI in particular:

p.s. Ignore the erratic Localizer indicator on the ADI, it's only getting test data.

Avionics Bending: End-To-End Test of the ADI, HSI, VSI and ALT with X-Plane

L-1011 Trainer Installation - X-Plane to ARINC End-To-End Test

Today Jim and myself reached another important millstone with the L-1011 project. We performed a complete end-to-end test of the ARINC 429 compatible primary flight instruments. This now finally tests all of the components in the loop for both the Captain's as well as the F/O station. The instruments tested today are:

• Altimeter (ALT)
• Vertical Speed Indicator (VSI)
• Attitude Director Indicator (ADI)
• Horizontal Situation Indicator

All in all we are transmitting 46 ARINC 429 labels over 8 discrete transmit buses. 4 of the buses are 100Kbps buses and 4 are 12.5Kbps buses. Of the four 12.5Kbps buses two are standard ARINC 429 buses and two are ARINC 575 compatible buses (so no SSM information on the label word). The video below is a short demonstration of flying the L-1011 sim in a very basic mode with no trim and only basic functions enabled, again, the test if for the ARINC instruments and not for the A/D conversion of the control inputs. 

In addition to the ARINC and X-Plane end-to-end tests we also installed the left hand side audio side panel. 

L-1011 Left Hand Side - Audio Side Panel

L-1011 Trainer Installation: Captain's and F/O ARINC 429 Instrument Tests

We are slowly ramping up the number of ARINC 429 labels sent as test data to the simulator instruments. The test data set has now enlarged from 26 to 48 labels sent over a total of 6 different buses; 3 buses on the Captain's side and 3 buses on the F/O side. Both sides will receive different data sets just as they would on the actual aircraft, this way we will be able to simulate complete subsystem failures. The video above show generic test data being sent to the Capt ARINC 429 instruments as well as to the F/Os instruments.