Monday, August 22, 2011

NAC develops local modification

Beginning in October last year, the South African Civil Aviation Authority (SACAA) required Supplementary Type Certificates (STCs) for any major avionics installation into a pressurized aircraft.

Due to the unavailability of suitable HF STCs for Embraer-120s, NAC Avionics, together with the NAC Sheet Metal department and Aerostruct, undertook a project to develop a local modification that led to the approval of KHF-1050 installations into three Embraer 120s. The modification falls within the SACAA engineering and certification review and, if approved by this body, NAC Avionics will be issued with an STC which can then be re-used and made available to other operators that might require the use of this STC.

One major element of the design was to enable field installation of the system with minimal downtime of the aircraft.

This was accomplished by the design of an equipment tray that can be pre-manufactured as a module, together with equipment trays and wiring attached. Field installation is a simple matter of mounting the shelf, running the wiring loom to the flightdeck and mounting the antenna in a matter of only three days downtime.

The KHF-1050 is a solid-state, high frequency, long-distance voice and data communication system made by Honeywell. The system is composed of four units, which function as follows:

• KRX1053 receiver/exciter to receive and transmit low-level signals

• KPA1052 power amplifier to amplify the low-level signal from the KRX1053

• KAC1052 antenna coupler to match the various impedances of the antenna to the 50ohm output of the transmitter

• Last but not least, the PS440 CDU (Control Display Unit) mounted in the cockpit that allows the pilot to select the frequency and mode of operation of the system and displays that information to the pilot.

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