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-.