Avionics Bending: VHF COMM Radio Head (Prototyping)

Last week, I posted the Design Specifications for the Radio Head interface for the Lockheed L-1011 project. Today, I built the prototype for the USB Attachment Unit (AU) based on the ATMEL ATmega32U4 micro controller. The I/O element used for the prototype is a MCP23016.

I have not modified the diode plate in the actual radio head quite yet, but as you can see in the image below, I have attached temporary connections from the radio head to the proto-board.



The layout is rather simple, as can be ween below. I will post the software for the project once the final board has been designed.



You can watch a short video clip below to see the radio head in action. Currently, the AU data is simply dumped to the MAC reading the USB output (the integration into X-Plane, as described in the Design Specification, will follow next week).

Original Flight Hardware: Main Instrument Panel - Captain's Side (Left)

The instruments for the main instrument panel of my Lockheed L-1011 project are coming along very nicely. As of today, the instruments missing from the captain's side of the main instrument panel are:

• Clock
• RDDMI
• Digital Attitude Indicator (ADI)
• Radar Altimeter Tape

Most of your certainly realized that the surface position indicator on the bottom right hand side is not the correct one for the L-1011 (it's actually from a Boeing 727). I am also still looking for the correct surface position indicator.

Avionics Bending: Cabin Vertical Speed Indicator (Analysis)

There are a number of different configurations of the Cabin Pressuizaiton control panel for the Lockheed L-1011. Most L-1011's had a combination instrument that would show cabin pressure and cabin altitude (similar to what you would find on the overhead of Boeing 737 panel). However, versions of the L-1011 had a discrete VSI, Pressure Differential and Cabin Altitude instrument .... very much like the Boeing 747. The pressurization panel that I have happens to be one that takes all 3 instruments. Today, we are going to look inside the fully analog CABIN VERTICAL SPEED Insrument.

Top View: The inside of the instrument is dominated by the large copper disk that flexes under different air pressure and controls the needle. Air will either enter the instrument at a fixed rate or leave it at a fixed rate ... hence, the differential will show the cabin climb or descent in thousands of feet per minute.

Design Specification: VHF COM/NAV Frequency Selector

I have written a design specification for the VHF NAV and VHF COM frequency selectors used on the Lockheed L-1011 Project. I call them "radio heads". I would like to get some input on the design document. You can see the document by following the link below:

Radio Head Design Specification

The electronics components selected for this initial design specification are the ATMEL 8bit ATmega32U4 MCU and a I2C controlled I/O chip made by NXT.

Avionics Bending: Cabin Pressure Control Module (Analysis)

I described the function of the Cabin Pressure Control system of the Lockheed L-1011 in a previous posting: Original Flight Hardware: Cabin Pressure Control (Sub-Panel) In this analysis we will discover that the actual control panel is a rather simple device consisting of a number of switches and two tapes for ALTidude SET and BAROmetric pressure SET. The pressurization control module on the L-1011 was built/designed by the engineering company Hamilton Standard. (By the way, they also designed the life-support systems for NASA's space suits amongst many many other things).


The only enclosure component that can be easily removed is the top panel.


Top View


The tape mechanism in the cabin pressure control module is significantly simpler than the tape used in the trailing edge flaps indicator. In essence, the tapes are the same size as 35mm motion picture film and use a similar transport mechanism (one perforation side only) with a supply and a take-up reel. For position encoding, the tape is linked to a potentiometer (see image below).



The original flight hardware had a number of pressure switches that would actuate different functions of the instrument. The pressure switch and the pressure transducer in the image below will not serve any function once we re-work the module to connect to the flight simulator.

Cockpit Design Study: Control Wheel

The spacious cockpit of the Lockheed L-1011 has a dual control column layout. Each control wheel has an electric trim wheel, an auto-pilot disconnect and a takeoff/go-around switch (see images below). The control column is 25" tall and connects to a 6" raised platform.



All images in this posting are from the Lockheed L-1011 section owned by the Delta Air Transport Heritage Museum in Atlanta, GA.

Original Flight Hardware: Engine Status Panel

The flight engineer station on the Lockheed L-1011 is home to a number of engine panels. A few days ago I showed you the ENGINE OIL panel. In today's posting we are taking a look at the ENGINE STATUS panel. There are actually a total of 3 panels that specifically deal with engine information, they are: ENGINE STATUS, ENGINE OIL and ENGINE FUEL.

The panel is home to the following instruments for the number 1, 2 and 3 engines.

• %N2 Stage RPM
• Engine Vibration

The Engine Status panel has a number of selector switches, a rotary switch and a test button (as seen in the image above). The TEST button is a momentary switch that will drive all the indicators towards zero for testing. The PICKUP SELECTION switches decide if FAN (A) or TURB (B) vibration will be indicated on the VIB instruments. The rotary switch sets the sensitivity of the vibration indicators from NORM, LOW, MED to HIGH.


Panel Location

Avionics Bending: Audio Selector Panel (Analysis)

I chose a set of Audio Selectors made by Gables Engineering for the Lockheed L-1011 project. The L-1011 used a number of different audio selectors, depending on the avionics package selected by the customer. This particular audio selector panel is from a TWA L-1011.



The case for the selector panel is split into two pieces: a top plate that unscrews with four screws, and a "U" shaped enclosure that also fastens with four screws.


Top: The top view of the audio selector is dominated by the brown circuit boards for the push button selectors.


Right hand side view


Bottom view


Left hand side view
Each of the audio selector push buttons has a dual function: (a) when depressed, the audio source is switched to the amplifier and, (b) turning the push button regulates to volume of the selected source. The volume is changed with a potentiometer on the backside of the switch, as can be seen below.


Each audio selector has a primary and an alternate amplifier. The amplifier can be selected with a toggle switch on the lower left hand side of the audio selector panel.

Avionics Bending: AFCS Warning Panel (Analysis)

The AFCS WARNING panel is the last of three panels for the AFCS system that we will examine for the Lockheed L-1011 cockpit. In previous postings we looked at the AFCS MODE panel and the INSTRUMENT COMPARATOR panel. Like the other two panels, the AFC WARNING panel uses solenoid driven flags to indicate warning messages.

This particular unit was made COLLINS AVIONICS and goes hand in hand with the AFCS Mode display.



Whenever a flag is raised on the panel, the ALERT button will blink until the ALERT button has been pressed. Pressing the button for a 2nd time resets the flag(s). The large print board on top of the instrument implements the former described feature.

Top View


Right hand side view. Here you can see the typical push solenoids used for the flags.


Bottom View.


Left hand view.


The two test switches, one in the top left and top right corner of the instrument, will show two different warning states each flag can be in.


Test 1 Button: AP DISC (Autopilot Disconnect), ATS DISC (Auto Throttle System Disconnect), AP LIMIT (Approach with Limited functions), NO FLARE (Automatic Flare not possible)


Test 2 Button: NO DUAL (No dual autopilot information for auto-land), NO GA (No automated go-around available). NO ALIGN (The Yaw Stability Augmentation System can not align the aircraft with the localizer), CMD DISC (Autopilot Command Mode not available).

Avionics Bending: Indicator Oil Temperature (Analysis)

There are number of temperature gauges in the Lockheed L-1011 cockpit. The three engine oil temperature gauges and the fuel temperature gauge are built the same way. The ECS temperature gauges are different. The gauges are basically synchros. At instrument shown in this posting was made by General Electric Corporation (GE) to Lockheed specifications.


Typical for this instrument is the way the instrument casing is mounted. There are three screws on the back of the instrument holding the core to the shell with 3 mounting clips.



Top View. What is interesting with this type of instrument is that the circuit boards are an integral structural component of the entire instrument. The boards have the back plate with the connector mounted on one side the instrument head mounted on the other. Also, note the use of flexible printed circuits as a replacement for hookup wires.


Right hand side view


Bottom View

Left hand side view

Just as the engine instruments from the main instrument panel cluster, the temperature gauges also have small post lights in the top left and top right corners. There is a test switch that can be used to test the instrument. Pressing the test switch will drive the needle to zero.


There is a large round transformer that would be used for transformation of the 115V 400Hz 1 Phase input signal.