Avionics Bending: Mechanical Synchro Signal Producer (Part 7)

Mechanical Digital to Synchro Converter - Test Assembly

Made lots of little tweaks to the individual parts and did a test assemble of some of the components. Eventually the entire assembly will be held together by four rods. Right now, I did a test assembly of the connector plate, the stepper motor plate, the synchro transformer plate and then the section that hold the electronics. Yep, those are cable ties holding the pieces together right now; however, I did this just to double check the sizing of the spacers and to make sure that the gear mechanism lines up.

Mechanical Digital to Synchro Converter

The image below shows the basic Beagle Bone Black in the the rear section of the design. There will actually be a cape on the Beagle that will handle the Stepper motor.

Mechanical Digital to Synchro Converter - Test Assembly

The images show the center core with the Synchro Transformer not yet assembled. I will try to get some rods over the next few days and then put the entire design together and cable it.

Mechanical Digital to Synchro Converter - Test Assembly

So far I am about $86 into this effort. Really want to keep it below $100 if possible. The most expensive part, so far, was the Beagle. Maybe in future iterations I go with a RaPi, but, actually both the BBB and the RaPi are a bit of an overkill for this.

Avionics Bending: Mechanical Synchro Signal Producer (Part 6)

Mechanical Digital to Synchro Converter - Connector and Electronics Bay

I added the connector plate and the electronics bay to the design. The Beagle Bone Black (BBB) will ride in an "electronics bay" on the backside of the design. This will be located behind the synchro transmitter. For the initial design there will be daughter board on the BBB driving the stepper motor (see image below). All connectivity, except for Ethernet, will be brought in through a Tyco Circular Connector. 

Mechanical Digital to Synchro Converter - Connector and Electronics Bay

The image below show the current design from behind. I envision a case around the complete design and a DIN rail holding bracket so that the unit, or multiple units, can be attached to a DIN rail in the simulator. The 26VAC 400Hz power sill also be brought in via the Tyco circular connector.

Mechanical Digital to Synchro Converter - Connector and Electronics Bay

Here is the left hand side view of the current design iteration. 

Mechanical Digital to Synchro Converter - Connector and Electronics Bay

Over time I will probably come up with a more space optimized design. If you have any design ideas please call them out to me. 

Avionics Bending: Mechanical Synchro Signal Producer (Part 5)

Mechanical Digital to Synchro Convert

Here is the first printed and assembled version of the mechanical digital to synchro converter motor assembly. It's a pretty simply assembly and together with the stepper motor and the synchro transmitter and the optical sensor I am about $22 into the project. In the image below you can see the proposed location of the optical sensor.  Next will be to design the plate that holds the Beagle Bone to drive the stepper motor with.

Mechanical Digital to Synchro Converter

Once I get a little further with the design I will put the CAD files on grabcad and the code on github. 

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.

Avionics Bending: Honeywell VSI/TRA

Honeywell VSI/TRA Display from TCAS-2000 System on the L-1011

Many of the L-1011's got upgraded with TCAS during their service time. The most commonly installed TCAS system on the L-1011 is the Honeywell TCAS-2000. I recently got my hands on a pair of Honeywell 4067644 VSI/TRA displays. The displays are vintage 1990s and will make the L-1011 simulator a lot more authentic, and, they are a lot of fun to work with. They take ARINC 429 input for both the VSI data as well as the TACAS data. The image above shows the VSI/TRA without any data sent to it, therefore, it indicates both TCAS and VSI as FAIL.

Here is a short demo of the VSI/TRA receiving Vertical Speed data from the ARINC 429 Primary bus

From: Honeywell TCAS-2000 Installation Manual

The VSI/TRA display runs off 115V 400Hz power and can take both ARINC 429 data as well as ARINC 575 ADC data. The 575 stuff is purely analog so not so interesting for working with the flight simulator, but the ARINC 429 stuff comes in very handy. Also, the VSI/TRA comes in a 41pin as well as a 55pin version. The ones that I have are the 41 pin version; and, here is the pinout for the 41pin VSI/TRA:

J1-1	VS +DC REF	ARINC 575
J1-2	VS DC RATE	ARINC 575
J1-3	VS -DC REF	ARINC 575
J1-4	Primary VS (HI)	ARINC 565
J1-6	Primary VS (LO)	ARINC 565
J1-5	VS 26 VAC Ref (Hi)	ARINC 565
J1-7	Not Used
J1-21	Not Used
J1-8	VSI Valid Flag	ARINC 575/565
J1-9	5V Lamp Dimming (LO)
J1-10	5V Lamp Dimming (HI)
J1-11	TCAS TA/RA (B)	ARINC 429
J1-26	TCAS TA/RA (A)	ARINC 429
J1-12	VS No 1 (B)	ARINC 429
J1-27	VS No 1 (A)	ARINC 429
J1-13	Not Used
J1-14	VS No 2 (B)	ARINC 429
K1-30	VS No 2 (A)	ARINC 429
J1-15	Config Common
J1-16	VS 26 VAC Ref (C)
J1-17	CS3	Configuration Bit
J1-18	PTM Common
J1-19	PTM PWR Out -15VDC
J1-20	PTM PWR Out +15VDC
J1-22	Chassis Ground
J1-23	115VAC 400Hz (C)
J1-24	Remote Light Sensor (LO)
J1-25	Remote Light Sensor (HI)
J1-28	Not Used
J1-29	RA Valid Out
J1-31	Source Select In
J1-32	CS0	Configuration Bit
J1-33	CS1	Configuration Bit
J1-34	CS2	Configuration Bit
J1-35	CS4	Configuration Bit
J1-36	CS5	Configuration Bit
J1-37	CS6	Configuration Bit
J1-38	CS7	Configuration Bit
J1-39	DC Ground
J1-40	115VAC 400Hz (H)
J1-41	CS8	Configuration Bit

The Vertical Speed input label for the VS 1 and VS 2 sources is Label 212.

Avionics Bending: Audio Panel Integration for the L-1011 Trainer

Tim Joransen and myself discussed how to do realistic audio panel integration for the simulator. So, to use a Virtual Air Traffic Control System (in our case VatSIM) we are currently thinking about using XSquawkbox.

To make the cockpit experience as realistic as possible from an audio perspective we need to have a number of discrete audio channels that can be fed into and received from the 4 audio panels in the cockpit. What and where are the four audio panels?

1. Captain's Audio Selector Panel on the aft center console
2. First Officer's Audio Selector Panel on the aft center console
3. Second Officer's Audio Selector Panel on the lower Flight Engineer's Console
4. Observer Audio Selector Panel to the left of the observer's seat

L-1011 Audio Selector Panel Locations - From Delta Pilot's Reference

Most audio panels made by Gables Engineering have a very similar pin configuration. And allow for a number of external components to be connected. For the L-1011 project, here are the external elements that connect to each audio selector panel:

• Headset (All Stations)
• Boom Microphone (part of the headset) (All Stations)
• Oxygen Mask Microphone  (All Stations)
• Hand Microphone (Captain, F/O and S/O only)
• Overhead Speaker (Captain and F/O only)
• Yoke R/T and INT Switch (Captain and F/O Only)

Here are the different audio channels that need to be fed to the Audio Select Panel to make the simulation as realistic as possible:

1. VHF COM 1 Audio (xsquawkbox)
2. VHF COM 2 Audio (xsquawkbox)
3. VHF COM 3 Audio (xsquawkbox)
4. HF COM 1 Audio (tbd)
5. HF COM 2 Audio (tbd)
6. VOR 1 Audio (xplane via plugin)
7. VOR 2 Audio (xplane via plugin)
8. ADF 1 Audio (xplane via plugin)
9. ADF 2 Audio (xplane via plugin)
10. Marker Beacon (xplane via plugin)
11. Ground Proximity Warning (xplane via plugin) 
12. Interphone (within the simulator)

The audio panel also routes the microphones for each of the audio stations to the respective channels. For the simulator here is the proposed mapping:

1. VHF COM 1 Microphone (to xsquawkbox)
2. VHF COM 2 Microphone (to xsquawkbox)
3. VHF COM 3 Microphone (to xsquawkbox)
4. HF COM 1 Audio (tbd)
5. HF COM 2 Audio (tbd)
6. Voice Recorder Output (tbd)
7. Interphone (within the simulator)

Of course there is still the Passenger Address (PA) system that would be, of course, part of the L-1011 however, for the purpose of building the simulator we will not worry too much about the PA system. We will not integrate the PA into the audio panel, however, the L-1011 has a Passenger Address panel on the overhead panel and we might consider connecting that. 

Avionics Bending: APFDS Engage Panel - Part 1

L-1011 APFDS Engage Panel

The next component of the Lockheed L-1011 Autoflight system is the APFDS Engage panel. This panel is located in the middle of the L-1011 Glare Shield (see below)

The panel has switches for the Autopilot A and B as well as the Left and Right Flight Director (FD). The Autopilot of the L-1011 as both a Control Wheel Steering (CSW) modes as well as a full Command (CMD) mode. Both the A and the B system of the auto flight systems work independent unless the aircraft is in Approach/Land (A/L) mode during which both automatic flight systems are required. 

The panel that I am using for this demo and the test integration with X-Plane is one of several APFDS Engage panels we have at the museum. This particular panel is a little beaten up, but, it makes for a great test instrument. The switches on the panel have long extensions and are frequently called "bat-switches". The flight director switches are normal toggle switches with the SYNC position having a spring return. The autopilot swathes are magnetic latch switches that will be held in certain positions by solenoids. For example, if the the autopilot system is not ready, the switches can not be moved out of the OFF position, or, if engaged and the pilot presses the A/P Disengage switch on the control wheel ... the bat switches will return to the OFF position. Below is a short video showing the action of the switches as well as a schematic of the panel taken from the WDM fiche.

APFDS Engage Schematic - From L-1011 WDM

Avionics Bending: L-1011 Autopilot - Pitch Mode and Heading Panel - Part 3

L-1011 Autopilot - Vertical Speed Select

The VERT SPEED window and Vertical Speed Select thumb wheel are two pretty interesting components of the Heading/Pitch Mode Panel oft he Lockheed L-1011 autopilot. The Vertical Speed is indicated using a tape that is motorized and the thumbwheel allows adjustment of the value once the VERTICAL SPEED (VS) mode is selected on the panel.

The module takes +12 and -12V bipolar power. For todays hack I have worked on reading the vertical speed select values as output by the panel. The values are between -5V for 4000 feet per minute climb and -10V for 8000 feet per minute descent. I love the face that 8000 fpm can actually be selected on the L-1011 autopilot ... makes sense for an emergency descent ... of course, would probably also make about 80% of the 280+ people behind you loose their lunch. :)

Here is short video of the values produce by the panel ... for detail information please also see the chart below:

Avionics Bending: L-1011 Autopilot - Pitch Mode and Heading Panel - Part 2

Over the holidays I have been working on the digital input/output integration of the L-1011 panels using the Interbus components that I chose a few months ago. The project is not going quite as fast as I had hope it to progress due to chronic funding problems. However, every week I am making are small steps towards breathing live back into this great machine. After all, it is the largest project I have ever undertaken.

Here is a test setup for the Ethernet to Interbus I/O testing. The test setup consists of a single 32 port Digital Input and one 32 port Digital Output element. The Interbus terminal, DI-32 and DO-32 modules are made by Phoenix Contact.

Phoenix Contact Interbus Test Setup

Slowly the autopilot is becoming clearer to me and how to interface it with X-Plane. Below is a short video that demonstrates the initial digital integration between the Heading/Pitch Panel mode selectors and X-Plane.

Avionics Bending: Engine Oil Pressure Indicator

L-1011 Engine Oil Pressure - Smiths' Ltd.

The Engine Oil Pressure indicators used on the Lockheed L-1011 are made by Smiths. All in all there are three of these, one for each engine. They have a range from 0 to 100 psi in increments of 5 psi. Pressure range markings are red from 0 to 35 psi, yellow from 35 to 40 psi and green from 40 to 100 psi.

The three indicators have a common test switch on the panel (not shown in this posting). The test switch will drive the indicators to about 22 psi.

To indicate pressure the instrument would send a 400Hz SIN and COSIN signal to a sensor. The oil pressure presses down on a piston that then moves a coil that sends back a phase shifted signal to the instrument. The phase difference between the 400Hz reference signal and the signal produced by the sensor is then indicated as the pressure on the front of the instrument.

The image below shows a simulated phase shifted signal that outputs the 55 psi you see in the image at the top of this posting. The phase shift can be somewhat reproduced with a digital potentiometer, however, a much more elegant way would be with a resolver or a Digtial to Synchro Converter. The video at the bottom of the posting shows the instrument in action receiving a number of different wave offsets.

L-1011 Engine Oil Pressure Indicator - Phase Offset

Here is the schematic and pinout for the L-1011 Engine Pressure Indicator made by Smith Ltd.:

Avionics Bending: Engine Oil Quantity Indicator

L-1011 Engine Oil Quantity

The Engine Oil Quantity used on the Lockheed L-1011 is a General Electric 8DJ173 LWD1 and is a relatively simple instrument. It takes 115V 400Hz power. The instrument has a BITE test button on the lower left front. The test switch drives the indicator needle to 10.5 Quart. You can see operation of the instrument in the short demonstration video below.

On the real aircraft the instrument acts as the power source for the oil quantity probe. The instrument outputs 6.5VDC which can then be run through a digital 10K potentiometer to simulate the oil level probe. 

Below is the schematic and pinout for the Instrument from the L-1011 Training manual:

Engine Oil Quantity - Pinout and Schematic

Avionics Bending: Aural Warning Unit

L-1011 Aural Warning Unit

The L-1011 has a set of somewhat very distinct cockpit sounds. The sounds are created by an "Aural Warning Unit" located right underneath the second officer console. Finding this unit in L-1011 surplus and scrap was not particularly easy however, I got my hands on one that is in really neat shape and is an original L-1011 unit. The serial number on the unit is #160 so it's from somewhere out of the middle of the production run. The Aural Warning Unit produces audible alerts for:

• Unsafe Landing 
• Unsafe Takeoff 
• Cabin Pressure 
• Altitude Alert
• Flap Load Relieving 
• Overspeed Clacker
• Autopilot Disconnect

The following video lets you hear the different audio warning (caution, this is somewhat loud ... you might want to turn your speakers or headphones down a little)

The unit features two speakers ... there are actually two audio systems in the unit the Clacker has a discrete speaker and the rest of the oscillator driven warnings have their own speaker.

L-1011 Aural Warning Unit Speakers

Avionics Bending: Honeywell CD-800 Display Unit

Honeywell CD-800 Display Unit

Every now and then I need to take my mind off the L-1011 for a moment and go play with something totally different. Today I powered up a Honeywell CD-800 Display Unit. They are pretty neat little terminal units most frequently used on Gulfstream business jets and would be connected to something like a Honeywell NZ-920 Navigation Computer. While it is not totally unrealistic that such an avionics package could have been installed on the L-1011 I have not found any evidence that it was ever considered. The FMS on the L-1011 typically consisted of, for example, a Litton INS. However this unit is still a lot of fun and has a lot of ARINC 429, RS424 and RS232 inputs and it might become a good fit for the next project, the MD-83 project.

The CD-800 Control Display Unit (CDU) is the pilot interface with the FMS. The CRT displays relative flight information to the pilot. The pilot enters alphanumeric data into the system via the full alphanumeric keyboard. This data appears in the scratchpad to be line selected to the appropriate position on the CRT display. (from Honeywell Maintenance Guide)

Honeywell CD-800 Annunciators

Annunciators - The six annunciators located at the top of the CDU keyboard panel operate independently from the CRT and keyboard. Lighting of the annunciators is initiated by the navigation computer or performance computer via the RS422 serial data link. The two colors used for annunciations are white and amber. White indicates an advisory type annunciation, and amber indicates an alerting type annunciation (810 and up only). (from Honeywell Maintenance Guide)

Honeywell CD-800 Without Navigation Computer

Here it the block diagram for the unit:

(from Honeywell Maintenance Guide)

Avionics Bending: Percent N3 Tachometer Indicator

L-1011 %N3 Tachometer - RB.211

For today's avionics bend I am going to show you the %N3 Tachometer. The RB.211 is a three spool engine and therefor there is a %N1, %N2 and %N3 tachometer present in the L-1011 cockpit. The %N1 and %N3 tachometers are part of the engine cluster on the center main instrument panel. The %N2 tachometer is part of the engine cluster on the Flight Engineers station. The %N3 tachometer works pretty much just like the %N1 and %N2 tachometers in that they take a frequency and coverts it to a needle position as well as a digital readout (bottom of the instrument). Here is the schematic for the %N3 instrument:

L-1011 %N3 Tachometer Schematic and Pinout

What makes the %N3 tachometer different from the %N1 and %N2 tachometer is the fact that the instrument plays a pretty critical role during engine start up. To be more exact, it controls the duration of bleed air being supplied to the air-start motor on the engine.

Below is a picture of the Ground Start Switchlight for Engine 1:

The magic inside the %N3 instrument (on the left) happens during the engine start up and once the 3rd compressor stage has spooled up to 52% N3 with the air-start motor. Here is what happens 

The GROUND START switchights are solenoid held, and are latched in to initiate the start . This gives a command to open the associated start control valve to allow air (from the APU, another engine, or a ground cart) and begin the rotation of the compressors. The green VALVE OPEN light illuminates to indicate that the associated start control valve is NOT CLOSED. Once the %N3 Indicator reaches 52% the Ground Start switch for that engine is released and the valve closes. At this point the engine runs on it's own.

Here is a demo video of the %N3 action and solenoid held switch release:

Avionics Bending: Fuel Consumed Indication

L-1011 Fuel Consumption Indication System

The Engine Fuel Consumption indicator in the L-1011 cockpit consists of two instruments. The "Fuel Used" instrument located on the Second Officers lower console and the "Fuel Flow" (FF) instrument located on the main instrument panel. There is one of these instrument combinations for each engine.

The instrument on the right is the Fuel Used indicator which receives signals from the fuel flow meter installed as part of the engine fuel flow system. The signals received from the sensors are then routed through the Fuel Used instrument to the Fuel Flow instrument shown on the left in the image above.

Fuel Used Schematic 

From Lockheed L-1011 WDM, 1981

The Fuel Used Instrument is a GE 8DJ171 LWA 3

Fuel Flow Schematic 

From Lockheed L-1011 WDM, 1981

The Fuel Flow Instrument is a GE 8DJ170 LWA 1

Typically on the L-1011 every instrument has a test switch right on the instrument that drives the indicator to a predefined position. However, as you can see, the Fuel Flow instrument (on the left) does not have a test switch, because, it is tested via the Fuel Used instrument.

Below is a short video the shows the test of the Fuel Used and attached Fuel Flow instrument using the two position test switch on the Fuel Used Instrument