Avionics Bending: Gear Lights

For the last few days I have been working on the instrument cluster. There are 48 annunciators on the center panel and six of them are for the landing gear. 

• LEFT GEAR - Green - Down and Locked 
• NOSE GEAR - Green - Down and Locked 
• RIGHT GEAR - Green - Down and Locked 
• DOOR - Red - Landing Gear Doors
• IN TRANSIT - Red - Landing Gear in Transit 
• TRUCK - Amber - One of the landing gear trucks is not level 

The gear handle has a lock down solenoid that does not allow the gear level to be moved out of the down position if the aircraft is on the ground. The solenoid is held by 24VDC. The solenoid would be energized once the aircraft is airborne which would allow safe gear retraction.

L-1011 Electrical: Standby Power to ON (24-27)

Placing the standby power switch to the ON position will complete the circuitry to power both AC and DC standby busses from the batter, regardless of other power sources that are available.

L-1011 Electrical: Pilot Controlled Standby Power (24-26)

Standby power is automatically transferred to the battery if a failure occurs. However, the pilots may also manually control standby power by means of a switch located on the pilots' overhead panel.

Next to the switch is an amber light that warns if the standby power switch is unarmed.

L-1011 Electrical: Battery Powering AC and DC Standby Busses (24-25)

Should essential power fail, the battery is capable of powering both standby power busses.

The battery provides DC power directly the DC standby bus and, by means of an inverter, AC power to the AC Standby Bus.

A fully charged battery will provide power to both standby busses for approximately 40 minutes, minus 5 minutes for every unsuccessful APU start attempt.

Avionics Bending: ADVANTECH Relay Boards

I decided to stay with many of my instruments in the 28V realm. In order to switch that and to switch high current loads I decided to use ADVANTECH relay boards. These boards can be rather pricy, but I found them in surplus in Thailand and the first lot of boards has shipped to me this past week. The boards are in good shape and the folks in Thailand took good care during de-installation.

The exact type of the relay boards are ADVANTECH PCLD-785B with 24 relays. The boards are externally powered or can be bus powered. I plan on stacking two of the boards together with risers for 48 channels per stack. Four boards, or 96 channels, will be driven by a single National Instruments PC-DIO-96 card.

The L-1011 project will require a massive amount of relays because of the large amount of incandescent lights used on the various panels. The relay board is also handy for the many solenoids used in the L-1011 cockpit to hold switches in place.

L-1011 Electrical: Standby Power (24-22)

Standby power is that power that is required to descend the aircraft and land. If the airplane has only standby power, only the following items are powered:

• Captain's Instruments
• Fire Protection and Detection
• Manual Pressurization
• Start Ignition

The DC Standby bus is powered from the the DC essential bus.

One phase of the AC essential bus provides AC standby power.

Avionics Bending: SFENA ADIs are Going on a Trip

The SFENA ADIs are going on a trip to Spain for a few months. Javier Pérez at the Universidad de Las Palmas de Gran Canaria (ULPGC) will use the instruments in support of a paper that he will be writing over the next few months. The project will be heavily focused on driving the instruments with the ARINC 429 protocol. It will be really cool to see what Javier will be able to do with them. I will post some updates from time to time as he makes progress with the ADIs.

L-1011 Electrical: Multiple Power Failures (24-21)

To loose essential AC power, and I think is of particular interest to you Ian, it would be necessary to lose Bus 3 and generator #1.

To loose essential DC power it would be necessary to lose the essential Transformer/Rectifier T/R) unit and have the circuit breaker 3F3 open.

As you can see, essential power is well protected in the Lockheed L-1011.

L-1011 Electrical: Essential Power on Bus No. 3 (24-20)

With the essential power selector in the B3 position, bus #3 is providing AC essential power. This is the only position where the APU generator can be used as the source for essential AC power. The former is done via the AC tie bus.

L-1011 Electrical: Essential Power on Generator One (24-19)

Selecting G1 on the Electrical System Panel powers the AC essential bus directly from generator one, again prior to the generator breaker.

L-1011 Electrical: Essential Power on Generator Two (24-18)

With the essential power selector in the G2 position power is taken directly from generator two, prior to the generator breaker.

From this schematic it is easy to see that as long as the generator field relay (GFR) is closed the generator is capable of powering the essential AC bus if selected.

Avionics Bending: %RPM N1 Tachometer Frequency Test

Below is a short video of sending five different tachometer frequencies to the the %RPM N1 Indicator. This is work in progress but should give you a rough idea of what the actual indicator performance will look like:

In the example above the instrument runs of a 115V 400Hz Inverter and draws about 600mA. The frequency is a 5V differential square wave.

L-1011 Electrical: Essential Power Selector (24-17)

Essential power is defined as "that power that is necessary to continue the flight indefinitely."

It is the power necessary to operate the items that are essential to flight. Any generator on-board is capable of providing essential power to the flight critical systems.

The Essential Power selector switch is located on the lower right hand corner of the Electrical Panel.

The switch has two basic modes of selection, MANUAL and AUTO. The switch position determines the source of power to the AC Essential Bus.

L-1011 Electrical: Normal AC and Normal DC (24-16)

A quick review of the normal AC and DC power supply and distribution.

The three engine IDGs and the APU generator may be paralleled together. any one of the four generators may power all the aircraft AC busses through the tie bus.

Three Transformer/Rectifier (TR) units powered from the AC busses power the DC load busses. The DC busses are paralleled through a DC tie bus.

L-1011 Electrical: DC Busses in Parallel (24-15)

Each DC bus is connected to the DC tie bus by means o the DC Tie breakers. There are no electrical loads on the DC tie bus. All the main DC electrical loads are on DC Bus 1, DC Bus 2 and DC Bus 3.

L-1011 Electrical: Normal DC Power (24-14)

Normal DC power is obtained from Transformer/Rectifier (TR) units powered from the corresponding numbered main AC bus.

Each TR is rated at 75 amps and 28 VDC. Normal TR amperage with all TR's operating is 20-30 amps.

an overload capability exists:

• 100 AMPS for up to 5 minutes
• 175 AMPS for one minute max

Avionics Bending: RDDMI Pointer - Pinout

The second posting for the RDDMI deals with the pointers and the rotating compass card. Each of these elements is controlled by a synchro.

The compass card has one signal source and both the single as well as the double barbed arrow can be switched between ADF 1/VOR1 and ADF2/VOR2 respectively. Below is the pointer schematic for the RDDMI:

Below is the pinout for the RDDMI:

J1	01	Heading Input (X)
J1	02	Heading Input (Y)
J1	03	Heading Input (Z)
J1	08	Heading Synchro (X)
J1	09	Heading Synchro (Y)
J1	10	Heading Synchro Excitation
J1	11	VOR 2 Synchro (X)
J1	12	ADF 2 Excitation
J1	13	ADF 2 Synchro (X)
J1	15	ADF 1 Synchro (X)
J1	16	VOR 1 Excitation
J1	17	VOR 1 Synchro (X)
J1	18	115V 400Hz Power Input (Hi)
J1	23	Heading Synchro (Z)
J1	24	Heading Synchro Excitation Ground
J1	25	VOR 2 Synchro (Y)
J1	26	VOR 2 and ADF 2 Excitation Ground
J1	27	VOR 2 Excitation
J1	28	VOR 2 and ADF 2 Synchro (Z)
J1	29	ADF 2 Synchro (Y)
J1	30	ADF 1 Synchro (Y)
J1	31	ADF 1 and VOR 1 Synchro (Z)
J1	32	ADF 1 Excitation
J1	33	VOR 1 and ADF 1 Excitation Ground
J1	34	VOR 1 Syncrho (Y)
J1	38	VOR 2 - Flag
J1	40	ADF 2 - Flag
J1	54	ADF 1 - Flag
J1	55	VOR 1 - Flag
J2	b	DME1 Warning Flag - 28VDC
J3	b	DME2 Warning Flag - 28VDC
J3	B	DME2 - DATA
J2	B	DME1 - DATA
J3	S	DME2 - WORD SYNC
J2	S	DME1 - WORD SYNC
J2	T	DME1 - CLOCK
J3	T	DME2 - CLOCK

L-1011 Electrical: APU Power On Busses (24-12)

The APU generator is capable of powering all busses on the aircraft. With the APU generator field relay and generator breaker closed the APU powers the main busses through the tie bus.

Avionics Bending: RDDMI Digital DME Display - Pinout

The dual DME readouts are independent from the radial displays below. There is a DME indicator for DME1 and one for DME2. Below is the schematic for the dual DME display:

Here is the pinout:

Conector J2

Pin B: DME 1 Serial Data In

Pin T: DME 1 Serial Data Clock

Pin S: DME 1 Word Sync

Pin b: DME 1 Flag

Conector J3

Pin B: DME 2 Serial Data In

Pin T: DME 2 Serial Data Clock

Pin S: DME 2 Word Sync

Pin b: DME 2 Flag

L-1011 Electrical: Engine Generators in Parallel (24-11)

In normal operation the engine driven generators are paralleled with the electrical loads shared equally by all operating generators. The white flow bars indicate the associated relay is closed. The KW meters will indicate approximately the same load.

L-1011 Electrical: Generators In Parallel on Tie Bus (24-10)

The main AC busses are tied together to the AC tie bus by means of the AC tie breakers. this is the normal parallel condition for the generators.

The AC tie bus serves only as a connection point, these are not electrical loads on the tie bus. All the electrical loads are on the main buses.

Avionics Bending: Evacuation Signal Panel - Pinout

The evacuation signal panel is located on the pilots overhead panel. It is coupled to a number of evacuation signal stations throughout the aircraft. If you have one of these and you power it up ... be forewarned, they are very loud.

The instrument is made by Pacific Electro Dynamics, Inc. in Bellevue, Washington and has a part number of 247-1. Below is the schematic for the panel that also shows the combination of the master panel (pictured above) an the panels distributed throughout the cabin:

Here is the summary of the pinout for the Emergency Evacuation Signaling Panel made by Pacific Electro Dynamics, Inc part number 247-1:

Connector	Pin	Function
Sort	Sort	Sort

J1	10	Command Switch Light (+24V)
J1	03	Command Switch Light (GND)
J1	06	Power Input 26VDC
J1	05	Remote Command Switch (A)
J1	04	Remote Command Switch (B)
J1	11	EVAC Light Test (GND)
J1	07	EVAC Light Test (+24V)
J1	01	Light Plate (+5V)
J1	02	Light Plate (GND)

L-1011 Electrical: Generator Field Switch (24-9)

Excitation power for the main generator is controlled by the Generator Field Relay (GFR).

Permanent Magnet Generator (PMG) output passes through the GCU and is regulated to the proper values. As long as the GFR is closed, the main generator is putting out power.

The white flow bar above the generator KW meter on the Electrical System shows the the GFR is closed.

L-1011 Electrical: Typical AC Generator (24-7)

There are two parts to each generator.

• Main power generator
• Permanent magnet generator

both are turned by a common shaft. any time the shaft is turning the permanent magnet generator is producing a voltage.

L-1011 Electrical: KW Meters (24-6)

Each operating generator is being continuously monitored by a KW meter.

KW reading on the meter s the real power or energy the generator is supplying, such as operating motors, lights and heaters on-board.

The maximum continuous load on any single generator is 81 KW.

When in parallel operation, normal KW difference between the generators should be:

• 6 KW with the IDG's paralleled.
• 9 KW with APU and IDS's in parallel.