L-1011 CPT Installation - DC Hot Battery Bus

L-1011 Trainer - AC/DC Power Buildout

The last few weeks there had not been overly much to blog about. We continue work on the AC/DC power subsystems for the trainer. In the image above you can see 24V T/R units that will simulate the 3  transformer rectifiers (T/R) that are powered by the aircraft engines as well as the BATTERY simulator. There is only one more T/R unit that is missing and that will be for the DC Essential (ESS) bus.

All the power supplies are convection cooled and the video clip below is a short clip of the fan monsters coming alive.

The hot Battery bus is used for a lot of things on the L-1011; like APU start up and some very basic instrumentation. One good example for the use of the hot battery bus are the clocks in the cockpit. In order to not loose time, these clocks are powered by the hot battery bus on the actual aircraft. To stay as close to the original as possible, we are simulating the aircraft's battery with the 24V 20A power supply pictured below.

L1011 Trainer - Battery System Simulator

This supply forms the battery as well as the hot battery bus and is now driving the Haydon clocks installed in the Simulator. Below is a short video of the clocks running of the central universal time base as well as the 24V Hot Battery bus.

L-1011 Trainer - Clocks on Hot Battery Bus

Avionics Bending: Haydon Chronometer (Functional Test)

In two previous postings on the Haydon Chronometer here on the L1011 blog I have gone into detail on the general hardware and the pinout for the Haydon Chronometer. They are actually really neat instruments and not so difficult to control. I have created a very small setup that uses an ATMEL ATmega chip to create the two phase signals with. In the most simple form the clock could really be driven by using either a 60Hz AC source and a few caps for the phase shift or a 555 to create the two phases with. However, I prefer using a micro controller because I wanted to play around with different waveforms. I am excited to see Roberto use the setup as well in his B737-200 cockpit. Here are two images of the clock powered off (the red dot indicates no-power) as well as the backside of the clock with the original Deutsch connector. The connector was cut from the original L-1011 cockpit at about 4 inches after the connector ... so I had to repair the cable with 12 cable splices. I used a twisted shielded pair cable for the phase signals. 

Below is a short video that shows the functions of the A. W. Haydon Company Chronometer. 

Avionics Bending: Haydon GMT Chronometer - Pinout

One of the more frequently asked question is how to drive the aircraft clocks, or chronometer, that can be found on eBay from time to time. The L-1011 had at least two of them, in most cases 3 of them including the clock provided to the second officer. Most of them look somewhat like the one below and most frequently came out of B737s ... just like the one below (A.W. Haydon Company A15580-P1 - Clock, Aircraft Electronic) :

The short answer is that the clocks are not self-contained ... so no simple 28V to two pins and it will run. In other words, they receive their time signal from a central clock source (Master Time Base) ... this very much happens like the old analog clocks you sometimes see in airports or the old clocks you used to have in your school. All these receive the same clock signal so the they all run in "sync" with each other. Below is the standard schematic for a GMT Chronometer made by Haydon:

The schematic is pretty self explanatory with the clock on the right and the Mater Time Base Unit on the right. the Master Time Base Units are somewhat hard to find ... however, they have been on eBay from time to time and this is probably the easiest way to drive the clock ... however, you can also generate your 1V 60Hz signal yourself. Here is the most common pinout:

Pin 1: Instrument Lighting 5VAC (Hi)

Pin 2: Instrument Lighting (Lo)

Pin 3: 28VDC Clock Power

Pin 4: GND

Pin 5: Casing Ground

Pin 6: Clock Signal Phase A (1V)

Pin 7: Clock Signal Phase B (1V)

Pin 8: Remote Switch Output A

Pin 9: Remote Switch Common (Input)

Pin 10: Remote Switch Output B

The phase-shift between pin 6 and pin 7 needs to be 90º for this to work.

Avionics Bending: Chronometer / Clock (Analysis)

The clock/chronometer that I picked for the Lockheed L-1011 project was used on many different aircraft types, including the L-1011. The pair of clocks that I use for the main instrument panel are sourced from a Boeing 737.

The chronometer is a beautiful old analog instrument that uses stepper motors for both the GMT time as well as the sweeping second hand. Below is a description of the clock controls.


The top picture of the instrument shows the two tapes. The top tape is for hours on a 24h clock and the bottom tape displays minutes. The tape is advanced by a sprocket mechanism that is similar to that in an old film camera.

1) Top View


2) Left Side


3) Bottom



4) Right hand side.


There are several versions of this clock, below is a pin-out that applies this this particular clock only:

Pin 1 -> Integral Lighting 5V DC or AC
Pin 2 -> Integral Lighting 5V DC or AC
Pin 3 -> Instrument Power 24-28VDC
Pin 4 -> Instrument Power GND
Pin 5 -> Instrument Case Ground
Pin 6 -> Chrono Generator Phase 1
Pin 7 -> Chrono Generator Phase 2
Pin 8 -> Remote Switch 1
Pin 9 -> Remote Switch Common (12V-15V)
Pin 10 -> Remote Switch 2