mercoledì 26 novembre 2014

Avionic bending: Rudder Trim Position Indicator


The rudder position indicating system provides the flight crew with the amount of deflection of the rudder surface. This system does not include the rudder trim indication system. For information on the rudder and rudder trim control system

Component Details
Position Transmitter

The rudder position transmitter is mounted below the lower power control actuator. The transmitter's crank is attached to the rudder front spar by adjustable control rod. The position transmitter is clamped to a bracket mounted to a vertical fin rib 
Electrical power to the transmitter is controlled by the RUDDER POS circuit breaker on overhead circuit breaker panel P11.

Position Indicator

The rudder position indicator appears on the lower center display. The indicator scale in each direction is equal to 26 degrees.

The left power bus supplies 28 volts ac to the rotor in the transmitter, which is inductively coupled to the stator. The rotor is mechanically connected to the airplane control surface and rotates with the surface at the same time. Movement of the rudder changes the rotor position which in turn changes the stator output.This output signal is interpreted by computers and displayed on the flight deck. The control surface position is displayed on the lower center display.

The following video shows how the gauge behaves on power up and power down
This other video shows how the indicator behaves using a synchro transmitter moved manually

lunedì 27 ottobre 2014

Avionics bending: HF comm radio head

The HF (high frequency) communication system (referred to as the HF system) provides long-range air-to-ground or air-to-air communications. The HF system operates in the 2.800 to 23.999 MHz frequency range on 21,200 channels in either AM (amplitude modulated) or USB (upper side band) modes.

Two HF (high frequency) communication systems are installed on the airplane.

The left and right HF systems consist of two HF comm transceivers, two HF comm control panels, two HF comm antenna couplers and a single slot-type shunt-fed HF comm antenna. The audio, microphone and PTT functions of each HF system interface with the audio selector panels (ASP's) of the flight interphone system.

The left HF system utilizes 115v ac 400 Hz 3-phase power from the left bus. The right HF system utilizes 115v ac 400 Hz 3-phase power from the right bus. The LEFT HF COMM and RIGHT HF COMM circuit breakers are located on the overhead circuit breaker panel P11.

HF Comm Control Panel:

The left and right HF comm control panels (referred to as the control panels) are located on their respective side of the pilots' overhead panel P5. The control panels weigh approximately pounds and are self-contained, including power supply. Each control panel is dedicated to providing mode control, frequency selection, and RF sensitivity adjustment for its respective HF comm transceiver.

The front panel of the control panel contains a mode selector switch, two concentric frequency control knobs, LCD frequency display, and a RF sensitivity adjustment control. The function selector provides on/off control and the selection of the AM (amplitude modulated) or USB (upper side band) modes. The left frequency control selects the MHz and 100 kHz digits displayed on the frequency counters. The right frequency control selects the 10 kHz and 1.0 kHz digits on the frequency counter. The RF SENS control adjusts the signal sensitivity of the receiver circuits of the HF comm transceiver.

The control panel contains circuits which convert the mode and frequency selections into digital form. The control panel provides a 32-bit word to the HF comm transceiver in the ARINC-429 format.

lunedì 20 ottobre 2014

Avionics bending: VHF Comm tuning panel

Three VHF (Very High Frequency) communications systems (referred to as the VHF systems) are installed on the airplane.
The VHF systems supply line-of-sight voice communications with ground stations or other airplanes. The VHF systems operate in either 8.33 kHz or 25 KHz increments from a frequency range of 118.00 MHz to 136.975 MHz.

Each VHF system uses 28-volt dc power. The VHF system circuit breakers are located on the overhead circuit breaker panel, P11.

The left VHF system uses power from the dc standby bus and the right VHF system from the right dc bus.
The center VHF system uses power from the left dc bus.

Each control panel contains two frequency controls and displays, two frequency-in-use lights, and a transfer switch.

Each frequency control has two concentric knobs to change the frequency. The outer knob rotates to change the ones, tens, and hundreds units; the inner knob changes the tenths and hundredths units of frequency.
The transfer (TFR) switch can select either displayed frequency. When set, the selected frequency display shows -ACTIVE-.

Avionics bending: ADF tuning panel

The Automatic Direction Finder (ADF) system is a navigational aid. It provides bearing to selected ground stations and is used as an audio receiver. It processes frequencies from 190 kHz to 1750 kHz. This includes the standard AM broadcast and low frequency non-directional beacons.

The ADF control panel is used to select the operating frequency of the system. The system always operates in the ADF mode. In this mode, the system can use the sense antenna input to receive AM radio or weather broatcasts. By using both sense and loop antenna inputs, the system can also determine bearing to the selected station. This bearing data can be displayed on RDMI or RMI and EHSI (if installed).


sabato 18 ottobre 2014

Avionics bending: Fuel Temperature indicator

The fuel temperature and indicating system measures the fuel temperature and supplies visual indication of the temperature on the overhead panel, P5. The system has a fuel tank sensor and a temperature indicator. Power is supplied to the system by the 28 volt dc left bus. Information displayed is used in conjunction with the fuel de-icing system when it may be advisable to use the fuel heater to prevent fuel icing at the fuel filter.


The sensor and lead resistance form two legs of an input bridge circuit. The resulting signal from the bridge circuit is amplified, converted from analog to digital, and shown as a digital readout.To do a test of the fuel temperature indicator, put the fuel quantity test switch on the P61 panel to FUEL QTY. The readout should show -185+/-2.


martedì 23 settembre 2014

Avionics bending: Pilots Call Panel


The SELCAL system provides notification to the flight crew when a ground station desires contact on one of the communication transceivers. SELCAL reduces pilot diversions and workload by eliminating the need for continuous monitoring of communications frequencies.

A ground station calls a particular airplane by transmitting a set of four audio tones over a
communications transceiver. The SELCAL decoder receives the audio from the particular transceiver and compares the tones to an assigned code. When the tones and the code are the same, a chime sounds and a call light on the pilots' call panel comes on, corresponding to the communications transceiver which received the signal. The decoder and call switch are manually reset after each call.

The SELCAL system consists of a SELCAL decoder, a coding receptacle, HF, and VHF call switches on the pilots' call panel. System electrical power comes from the left DC bus, through a circuit breaker on overhead panel P11.

There is one blue call switch on the pilots' call panel for each transceiver connected to the
SELCAL decoder. Each call switch alerts the flight crew of a ground-to-air call received by that transceiver. Pushing the call switch, or pushing the PTT button on the associated transceiver, resets the light and decoder.

Following pictures are during light test.


Power and audio inputs are wired directly to the decoder. Thus, the only operational control is for the reset function. The system is reset by pushing the associated call switch or by
pushing the PTT button for the associated transceiver.

The decoder monitors audio from the VHF and HF transceivers. When the received code matches the code programmed by the coding receptacle, the decoder recognizes it as a call to that airplane.
The decoder then turns on the call switch associated with the transceiver which received the call, and also sounds a chime in the flight compartment. The call switch and SELCAL decoder are then manually reset to await the next call.

This panel is on the overhead panel, P5. The cabin interphone system connects to the pilots' call panel through lighted call switches (FWD, MID, AFT, ALERT). The blue lights in the buttons come on to show incoming attendant calls and go off when pushed.
The CABIN CALL switches are also used to signal the related attendant station. To make an alert call the ALERT call switch signals all stations at the same time.
The FLT INT switch connects the cabin interphone and flight interphone amplifiers in parallel to give the flight crew access to the cabin interphone system through the audio selector panels.
The GND CALL switch signals between the flight compartment and nose Landing gear area.


mercoledì 17 settembre 2014

Avionics bending: Compartement Temperature Indicator

The primary (zone)temperature indication system is used to display the compartment and duct temperatures for the flight deck zone, forward zone, and aft zone.

The temperature indication system for each zone consists of a compartment temperature indicator, a compartment temperature bulb, a duct temperature bulb.

The compartment temperature indicator is located in the flight compartment near the air conditioning control panel, and has three liquid-crystal-display (LCD) readouts to display the temperature (1 to 99-degrees) in each of the three zones.
Twenty-eight volt dc power operates the compartment temperature indicator. The indicator sends a reference voltage through each compartment temperature bulb. The resistance through each temperature bulb varies with temperature and the signal then returns to the indicator. Thus the voltage level returning to the indicator produces the temperature readout corresponding to the actual compartment temperature.
Following the schematic and wiring diagram of the unit


The following picture shows the temp indicator with power still on, but no signal from the sensors.

In the following picture I simulated a sensor using a 100 ohm resistor for each compartement which gives a readout of 22°Celsius


martedì 8 luglio 2014

Avionics bending: Mode Control Panel (MCP)

Hello people, sorry for the long time but I've been really busy with lot of stuff and had no time to make posts...

Anyway here I will show you one of the most used parts by the pilots those days, the MCP.

The MCP sends and receive data to/from many equipements, mainly involved are the 3 FCC (Flight Control Computers) and the TMC (Thrust Management Computer) and it's only a part of the Autoflight system.
The following scheme simplifies the interaction between the various equipements operating the autoflight functions.

The MCP has 3 connectors in the back which directly correspond to the 3 channels it operates (L, C, R)

The following pictus shows internal autopilot block scheme and the connections that each channel features

As you can see the MCP operates with 28VDC and a simple power up test allows some functions to work as you can see in the following video:

The following video shows the Airspeed's Speed Bug driven from the MCP dedicated ARINC channel

venerdì 7 marzo 2014

Avionics bending: Engine Standby Indicator

Hello people. I finally am the owner of a very neat unit, the engine standby indicator from a B767-200 used along with CF6-80A2 engines.
I did a did power up test with 28VDC and used its internate BITE test function to chech the unit was workin as expected.
Here is the schematic of the unit

and here are few pics and a video of it running, enjoy!