1616-055-10 – EMS Aviation MMU-II Mission Management Unit 📡
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Overview
The EMS Aviation (now Honeywell Sky Connect) 1616-055-10 MMU-II Mission Management Unit is a compact, Dzus-mounted cockpit control device central to the Sky Connect Iridium satellite communication and tracking system. Designated specifically as a Mission Management Unit, its primary function is to serve as the pilot-facing interface for voice telephony (POTS) and two-way text messaging via the globally available Iridium satellite network. The $-10$ variant is often associated with specific panel lighting (non-NVG) and feature sets.
The MMU-II is a critical tool for fleet managers and flight crews demanding seamless, reliable communication outside of traditional air traffic control (ATC) coverage. It connects to the Iridium transceiver unit via a serial (RS-232) or POTS interface, allowing the pilot to initiate voice calls via a headset connection into the aircraft audio panel and to generate, store, and transmit pre-formatted or free-form text messages. By integrating a full telephone keypad and a clear display, the 1616-055-10 significantly minimizes pilot workload during satellite communication tasks.
Key Features
Voice Telephony Interface (POTS): Functions as a standard telephone dialer, connecting the pilot's headset via the aircraft audio panel to the Iridium satellite voice channel. Supports standard POTS (Plain Old Telephone Service) 2-wire interface.
Two-Way Text Messaging: Allows the pilot to create and receive Short Burst Data (SBD) text messages, including the use of highly customizable, pre-stored message sets and forms to rapidly communicate status or telemetry.
Large Memory Capacity: Designed with significant internal memory (typically 32K Flash memory) to store up to 500-1000 prestored phone numbers, names, and a directory of up to 200 customized text messages/mini-forms.
Ergonomic Cockpit Design: Features a two-line, 32-character alphanumeric Vacuum Fluorescent Display (VFD) and a rotary control knob/push-button for efficient, low-workload navigation and operation.
DZUS Rail Mount: Designed to fit securely into a standard Dzus rail location in the cockpit panel, ensuring a robust, integrated installation.
Flexible Dimming Control: Includes various dimming options (photocell, manual, or dimmer bus input) compatible with 5VDC, 14VDC, or 28VDC systems for cockpit lighting integration.
Technical Specifications
Part Number: 1616-055-10 (Specific model variant of MMU II)
Component Type: Mission Management Unit / Satellite Communications Dialer
OEM Manufacturer: EMS Aviation, Inc. (Now Honeywell Sky Connect)
Mounting Standard: Standard Aircraft Dzus Rail Mount (Requires approximately 6.5 inches panel depth).
Display: 2-line, 32-character Alphanumeric VFD Display.
Input Power: 10 VDC – 32 VDC (Nominal Current: <1A Continuous, <3A Peak at 28 VDC).
Audio Interface: Supports headset-level interface tied into the aircraft audio panel (4-wire audio system compatible).
Ringing Voltage: Utilizes a generated 65Vrms ringing signal via an internal DC/DC converter for phone functionality.
Interface: RS-232 Serial Data Port (for Transceiver control/messaging) and POTS 2-wire audio system.
Environmental Compliance: Qualified to meet DO-160E temperature specifications (e.g., -40 degrees C to +70 degrees C short-term).
Certification Status: FAA and EASA Certified (TSO/PMA dependent on the overall Sky Connect system certification).
Aircraft Compatibility
Primary Usage: A key interface component for the Sky Connect Tracker System on aircraft requiring global voice and data communication.
Typical Aircraft: Found in a wide variety of airframes from General Aviation high-performance pistons and light twins to corporate jets and helicopters (e.g., EMS, SAR, Offshore).
System Integration: Requires connectivity to the Iridium transceiver unit (e.g., Sky Connect Tracker III) and the aircraft's audio panel.
Verification Note: The MMU-II is installed under various STCs. The specific STC's Approved Model List (AML) for the Sky Connect system is the definitive and final authority for aircraft eligibility.
Applications Section
The 1616-055-10 MMU-II unit streamlines critical communication tasks:
Urgent Reporting: Enables pilots to rapidly send pre-configured, high-priority text messages (SBD) to ground operations, bypassing voice channel congestion.
Mission Coordination: Facilitates two-way communication with dispatch and ground crews for logistical updates, routing changes, and mission-specific coordination.
Maintenance Communication: Allows remote technicians to download message sets or perform over-the-air configuration updates via the RS-232 link to the transceiver.
Why Choose the 1616-055-10 OEM MMU-II Unit?
The EMS Aviation MMU-II is the certified command center for reliable satellite communication. The critical value of the OEM unit lies in its adherence to DO-160E standards for vibration and its precisely engineered POTS interface. Non-certified dialers cannot guarantee the required 65Vrms ringing signal compatibility or the electromagnetic interference (EMI) shielding required to operate alongside sensitive cockpit avionics. The MMU-II's highly customizable prestored message function minimizes cockpit workload and the risk of transcription errors when communicating critical data or coordinates.
The MMU-II's interface logic is designed to minimize complexity for the flight crew, relying on a human-factors optimized menu structure accessed via the single push/turn rotary controller. Electronically, the unit converts pilot inputs into coded digital commands sent over the RS-232 link to the main transceiver, which manages the satellite communication link budget. The internal POTS audio circuit requires a built-in DC/DC converter to generate the high-voltage 65Vrms AC ringing signal, necessary to simulate a standard ground telephone line and ensure the headset audio interface functions correctly for both ringing and voice transmission.
Note: The 1616-055-10 MMU-II is an avionics control unit that must be configured using specialized software to load the required Message Set (including phone numbers and text forms) before it is fully operational. The unit requires power from the aircraft's electrical bus. Installation must be performed and certified by a licensed Avionics Technician or authorized Sky Connect Dealer in strict accordance with the MMU-II Installation Manual and the applicable STC documentation to ensure proper audio panel and transceiver interface.
Documentation
Authoritative documentation for this certified avionics component includes:
EMS Aviation (Sky Connect) MMU-II Mission Management Unit Installation Manual (P/N 1616-964-12, or latest revision).
RTCA DO-160E Environmental Testing Standard.
Applicable Iridium SATCOM System STC documentation.