L-1011 Trainer Installation: ARCIN 429 for Altimeter and Audio Side Panel

L-1011 Altimeter ARINC 429 Integration Tests

Today Jim Blasco and myself worked on doing ARINC 429 label integration tests with the Altimeter. The Altimeter uses Label 204 and due to the fact that it uses a slightly different variant of a ARINC 429 compatible protocol it has to run on it's own bus. The 204 Label for the Altimeter uses a 32bit word that does not have a SSM field or Parity Bit.

The short demo video bellows shows data being sent to the ADI, HSI, VSI and ALT.  The next steps will be to send actual simulator from X-Plane to the instruments. 

Besides the tests with the Altimeter we also installed the first of two audio side panels. The L-1011 Cockpit Procedure Trainer did not come with these side panels and we got them from an actual (British Airways) L-1011. The audio side panels provide the hookups for the headset (boom and headset) as well as a connector for the hand microphone. The side panel also has room to store the headset in.

L-1011 Audio Side-Panel Installation

L-1011 Flight Instruments: Barometric Altitude Indicator (ALT) (31-8)

The most typically installed Altitude Indicator on the L-1011has two fail flags:

• SSC - the Static Source Correction feature of the Air Data Computer (ADC) altitude computing has failed. When this flag is displayed, the ADC is still providing altitude data, however, the data is uncorrected. 
• OFF - there has been an ADC input failure or loss of power to the instrument.

Pressing the ALT ALTN Switch on the pilots panel (located below the HSI) will provide the opposite side data to be the affected altimeter and vertical speed unless the actual indicator has failed. 

Avionics Bending: Sperry Rand Barometric Altitude Indicator - Pinout

This posting gives you the schematic and pinout for a Barometric Altitude Indicator such as as the SPERRY Rand Barometric Altitude Indicator Part Number 2594620. This instrument is loaded with synchros and requires quite a lot of external devices to drive it with. The schematic below shows you how one of those altitude indicators would have been connected to the Central Air Data Computer (CADC). This is analog at its very best and an amazing piece of engineering!

In the L-1011 the Captain's and the First Officer's barometric altitude diagram are connected in such a way that the instrument source for one instrument can be referenced by the other and the other way around. It's a really neat way of "bootstrapping" the instruments together. To use this instrument with the flight simulator, you will need to create the many synchro sources and act as the CADC.

Below is the pinout for the SPERRY RAND Barometric Altitude Indicator:

Format: Connector | Pin | Function (see schematic for details)

J1	10	Fine Altitude CADEC 1 (Z)
J1	12	ALT Valid
J1	22	EXC Monitor to ICM
J1	23	26V 400Hz Excitation from Ohter Side J1 Pin 54
J1	24	Bootstrap From/To Opp (X)
J1	25	Bootstrap From/To Opp (Y)
J1	26	Bootstrap From/To Opp (Z)
J1	28	Instrument Lighting (Lo) - Ground
J1	29	Instrument Lighting (Hi)
J1	3	115 VAC 400Hz Power Input
J1	30	SSEC VALID
J1	31	Fine Altitude Output (X)
J1	32	Fine Altitude Output (Y)
J1	33	Fine Altitude Output (Z)
J1	36	Valid To Opp Ind
J1	37	Coarse Altitude Output (X)
J1	38	Coarse Altitude Output (Y)
J1	39	Coarse Altitude Output (Z)
J1	4	115 VAC 400Hz Ground (Lo)
J1	42	26V 400Hz Excitation from Other Side J1 Pin 34
J1	43	Tresh Adjust To ICM (X)
J1	44	Tresh Adjust to ICM (Y)
J1	45	Tresh Adjust to ICM (Z)
J1	47	Instrument Lighting (Hi)
J1	5	Coarse Altitude CADEC 1 (X)
J1	50	26V 400Hz Excitation Input
J1	51	26V 400Hz Excitation Ground
J1	53	26V 400Hz Excitation Input
J1	55	Valid Monitor Output
J1	6	Coarse Altitude CADEC 1 (Y)
J1	7	Coarse Altitude CADEC 1 (Z)
J1	8	Fine Altitude CADEC 1 (X)
J1	9	Fine Altitude CADEC 1 (Y)

Avionics Bending: Altimeter (Analysis)

For the Lockheed L-1011 cockpit project, I picked a set of Altimeters made by ADS Inc. There are a number of altimeters throughout the cockpit; 3 of them on the main instrument panel and one on the pressurization panel. The instrument featured in this posting would be the primary altimeter used by the captain and the first officer.


Altimeters are corrected for barometric pressure at a flight level below 18000ft (180). Hence, all altimeters have a BARO correction method (a knob or something) to adjust for either In.HG or MB (Millibar are mostly used in Europe).


This altimeter has an interesting mechanism for barometric correction. It uses a number of servos to do that with. Here are the three standard views of the instrument:

TOP


RIGHT HAND SIDE


BOTTOM


LEFT HAND SIDE


There are total of five syncro devices in the instrument. Two of them are differential resolvers (CD) to encode the altitude reading and the barometric correction, one syncro limiter, a syncro transmitter and a syncro generator (basically the motor driving the instrument).



The flag arm is moved by a simple solenoid.



The altitude is displayed by four number drums. Two large ones for the 1000s and 10,000s of feet and two small ones for the hundreds and tens of feet.