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.

 

 

 

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).

 

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.