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The 344A or B Instrumentation Unit from Collins is the companion of the 51X-2 VHF receiver. It translates the received audio signal into signals for navigation instruments like a Course Deviation Indicator (CDI) and Radio magnetic Instrument (RMI).
The 51X-2 VHF receiver has an output contact that indicates whether tuning is to a NAV channel (108-117.95 MC) or a comm. channel (118 and up) and another contact to indicate whether this NAV channel is one of the 20 Localizer (ILS) channels or a VOR channel.
Like the 51X-2 receiver and 17L7 transmitter, the instrumentation unit has a 3/8 ATR case . There is only one (32-pole) plug for all connections. The unit has a modular construction., and came in two versions with half, or all modules fitted : The 344A has 7 modules and can drive one Course Deviation Indicator. The 344B with 11 modules can drive two Course Deviation Indicators, the Autopilot, and a Radio Magnetic Indicator (RMI)
The Instrumentation Unit is powered by 115V/400Hz and 27.5Vdc, together 35W in average. The filaments are the main consumer, and a versions exists were they are DC powered, and a version with ac powered filaments.
The circuit diagram of the 344A is here The circuit diagram of the 344B is here ( with RMI drive capability, shown below )
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1957 |
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VINTAGE AVIONICS |
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INSTRUMENT LANDING SYSTEMS |
The Collins 344A or B VOR/LOC converter was used with the 51X-2 VHF Receiver (bundled as VOR-101) or as part of the AN/ARC-73 VHF Comm/Nav set. |
