• Centralized control for all radios
• State-of-the-art Active Matrix Liquid Crystal Display (AMLCD)
• Consistent tune and mode selection operation of all radios
• Extended frequency ranges and spacing for international operation
• Full cross-side radio control capability
• No loss of radio tuning due to a single RTU failure
• Independent volume control for each radio
• TCAS control
• COMM, NAV, ADF and HF presets
• Standby HSI display
• Standby engine display (application dependent)
• Real-time display of system interface, fault history and radio diagnostic codes
• Built-in-test capability

The Collins RTU-4220 Radio Tuning Unit product family provides integrated control of Communication, Navigation, Surveillance (CNS) radio sensor operations. Incorporating state-of-the-art Active Matrix Liquid Crystal Display (AMLCD) and electronics packaging technologies, these RTUs reduce weight and power consumption by nearly two-thirds compared to similar CRT-based units. Convection cooled and only six-inches deep, these RTUs can be conveniently positioned for true man-machine efficiency.

Extensive, self-contained input/output permits these RTUs to interface with a full suite of radio sensors without the need for an external data concentrator. Comprehensive system diagnostics provides fault isolation down to the offending line replaceable unit, while the fault history memory will capture and identify intermittent failures.

All versions of the RTU may be Dzus rail or panel mounted.

Two RTUs are required to provide the necessary redundancy in a typical installation. A single RTU-42XX can, however provide full control of the entire radio complement. In reversion or emergency power operations, the remaining RTU can carry on without any loss of radio tuning function.

Rockwell Collins' proprietary high-technology optics has contributed to the highest quality AMLCD displays available. The RTU-4200s 3ATI display provides a clear, bright, sunlight-readable display and excellent off-center viewing angle performance.

The RTU-42XX incorporates one common control scheme and philosophy to provide a centralized control point for all CNS operations. A logical, intuitive menu structure minimizes pilot workload; only preset frequency programming resides beyond second level menu operation.

The RTU-42XX operates concurrently with both Commercial Standard Data Bus (CSDB) and ARINC 429 digital interfaces. The RTU can act as a bilingual translator, formatting FMS ARINC 429 commands for a CSDB radio. Hybrid systems integrating both interfaces are now possible. A complement of discretes keeps RTU application flexible.

The Collins RTU-42XX incorporates a complete set of radio management functions into a single unit. It provides a convenient means of selecting frequencies, codes, channels, operating modes and volume levels for all Collins Pro Line II and for 400 Series CNS sensors and the HF-9000. Additionally, the RTU-42XX has an optional backup Horizontal Situation Indicator (HSI) display and, at the request of airframe manufacturers, backup engine data display capability.

The application of the RTU provides enhanced reliability and simplified man/machine interface. Other key benefits are reduced radio control panel space and the ability to install optional radios without requiring additional controllers. Since all radios are managed by the RTU, one common control scheme and philosophy may be utilized, resulting in reduced pilot workload and training.

Consistent operation means that all radios are tuned in the same way using the same set of keystrokes and knob adjustments. Even future expansion of the aircraft radio complement does not change the pilot interaction with the RTU. Isolation is provided between the two RTU-42XX units such that failure of one unit will not affect the integrity of the other unit.

Dimming of the RTUs display is designed to track other flight deck displays by means of the airplane's master dimming control bus. Additional control within this range is possible by use of the display dimmer on the bezel of the RTU.

Nonvolatile memory is utilized so frequencies and settings will not be lost during power shutdown. At each power-up, all frequencies in use or stored at the last shutdown are again available, eliminating the need to reload often-used frequencies.

The RTU-42XX may be integrated with the Flight Management System (FMS) such that tuning of the radios can be performed via the FMS control display unit keyboard. Additionally, the RTU accepts FMS automatic tune requests for the VHF omnidirectional radio range/distance measuring equipment radios and routes them appropriately. The result is that the tuned frequency is always displayed on the RTU regardless of the tuning source.

Control of frequencies and Air Traffic Control (ATC) codes is performed on the top level page. The top level page displays Very High Frequency Communications (VHF COMM), Very High Frequency Navigation (VHF NAV), Automatic Direction Finder (ADF), ATC and Traffic Collision Avoidance System (TCAS) information. This page provides all normal tuning functions, complete with annunciation for abnormal operating modes. Pages selected below this top level page will return automatically after 20 seconds of control inactivity.

Radio mode control is performed on the main radio pages. In addition to radio mode selection, these pages provide frequency control, unique operation, self-test initiation and selection of preset frequency channel modes.

Radio preset control is performed on dedicated pages. These pages provide preset tune mode selection and numbered channel preset programming. Selecting the preset tune mode will, for that radio link the top level page tuning to the programmed numbered presets. (Both channel and frequency will be displayed on the top level page.)

Twenty numbered preset channels are provided each for VHF COMM, VHF NAV, ADF and HF COMM radios. Current active frequencies and mode annunciations are provided on all radio preset pages.

The RTU has an optional standby HSI page. The HSI display presents magnetic or true heading, VOR/ILS selected course and deviation and glideslope deviation. The active COMM, NAV and ATC frequencies/codes are displayed and can be adjusted on this page.

For custom OEM installations, a standby engine display page can be provided. This display presents a simple digital readout of engine parameters, e.g., low pressure, high pressure, engine pressure ratio, turbine gas temperature and fuel flow. The user may return to the appropriate top level page via the RETURN selection.

The RTU also provides maintenance display pages for CNS system interface status, radio diagnostics and fault history records. Available only to maintenance personnel, these pages allow extensive sensor system troubleshooting to facilitate quick repair and a reduction of expensive no trouble founds.

The RTUs system interface status pages provide a real-time indication of digital bus interface and discrete input status. Displayed in English text, these messages identify inactive/active data buses and gnd/open discretes to assist in fault isolation to the Line Replaceable Unit and wiring level. Bus port numbers and discrete input pin numbers are also displayed.

The radio diagnostics pages provide a real-time readout of the RTUs CNS frequency/code commands and the corresponding echo information from the sensors themselves. The sensor digital diagnostic word outputs, including the label number, side ident and diagnostic code (documented on Rockwell Collins' familiar key ring cards) are also displayed.

Fault history pages provide a recorded history of CNS failures that occurred during flight. The failure history, stored in nonvolatile memory, includes the sensor failure (diagnostic code) and the flight leg in which it occurred. For installations that include FMS, the failure date and time is also displayed. The RTU will store up to 100 faults. To prevent fault history clutter, a particular fault for each specific radio will be recorded only once during a flight leg. A provision for fault history clear is also included.