Envoy Data Link



CPDLC, Controller Pilot Datalink Communication, is also known as ATC Data Link. It enables two-way data link communication between the flight crew and the controller. It allows clear communication to be carried out over long sectors that would have traditionally been serviced by HF radio. FANS 1/A CPDLC normally uses SATCOM as the communication path due to its operation in remote regions – but it can also be used in areas of VHF coverage to reduce satellite media usage.


ADS-C supports the sending of flight information from the aircraft to specific ground Air Traffic Service Units (ATSUs). The aircraft can have multiple ‘contracts’ with each ATSU and each contract specifies when and what information will automatically be down linked by the aircraft. The system is two-way in that the contract is uplinked to the aircraft, which then responds when complying with the contract.


CPDLC Messages

ATN CPDLC is also known as ATC Data Link. It enables two-way data link communication between the flight crew and the controller.

ATN CPDLC implementation was originally driven by the Data Link Services (DLS) mandate for ATSUs and airlines operating above FL 285 in DESIGNATED European airspace. The fundamental driving requirement for the ATN mandate was the radio frequency congestion experienced within the airspace when utilizing voice for the requesting and reception of clearances by the flight crew.

Due to performance requirements for ATN CPDLC, VDL Mode 2 at a baud rate of 31.5Kb is the only approved media for ATN CPDLC.

Envoy ATC Main Menu R1


AOC Messages Uplink and Downlink Messages

Envoy has the capability to send ACARS messages over VDL Mode A, VDL Mode 2 (AOA), and SATCOM media connections.

ACARS ARINC 620 messages such as Weather requests, ICAO and IATA Out-Off-On-In (OOOI) reports and Aircrew Initiated Engine Reports are capable of being downlinked from the unit.

In addition, the Envoy unit has been designed to support construction of a wide variety of user downlink messages. These messages are constructed and tailored for individual airlines operational needs. Downlink messages are triggered as a result of a defined single event, multiple events, or continuous interval events.

Envoy ACARS Main Menu R1


Envoy enables Global Flight Tracking every 15-minutes per ICAO recommendation. To further aid flight crews and enhance airline operations, Envoy features condition-based reporting. By monitoring the condition of configured events and triggers, the timing of automated position reporting can change and increase in frequency depending on the severity of monitored parameters.


When Envoy is configured for ACARS operation, ATC requests for the following information and clearances are available to the flight crew:

  • •   D-ATIS
  • •   TWIP (Terminal Weather Information for Pilots – U.S.)

Additional  Capabilities


The Envoy unit has been designed to provide the capability to forward configured aircraft system parameters and uplinked messages for broadcast from the secure low-power Bluetooth transmitter located under the faceplate. Messages are broadcast at specific intervals and received by an application running on a specified crew device such as a tablet or phone.Use of broadcast only data and secure passwords eliminates security risks of non-authorized personnel electronically accessing an LRU on a commercial aircraft.


Envoy can be configured to work with an assortment of on aircraft end system devices in order to provide datalink capability for messages originating from the device or destined for the device.

Devices include Flight Management Computers for requests such as Winds Aloft or Flight Plan updates. These requests are transparently sent through the unit to the ground when initiated from the FMC. The accompanying response message from the ground is then routed by the unit back to the FMC where the uplinked message and data is available.


From the Envoy unit, connections are made to a 741 protocol compliant SDU data channel to support both FANS 1/A (CPDLC and ADS-C) messages and ACARS message exchanges.


Cockpit printer systems are commonly interfaced to data link avionics products. The cockpit printer interface to the unit allows for printing of ACARS and CPDLC messages to support flight crew procedures and for general reference.


Envoy includes an integrated Multi-Purpose Control and Display Unit, or MCDU. In addition, the unit conforms to the ARINC 739 characteristic and is capable of hosting displays and menu access of other avionics that are also 739 compliant.

Examples of hosting other avionics displays includes hosting a SATCOM SDU display so that the unit can be used to access functions such as dialing of phone numbers.

Interfaces and System I/O


  • •   ARINC 429 Interfaces to aircraft systems
  • •   ACMS (Aircraft Condition Monistory Systems): ARINC 619 interface
  • •   CDU (Control Display Unit): ARINC 739
  • •   CVR (Cockpit Voice Recorder): ARINC 619
  • •   Printer: ARINC 740 and 744
  • •   SATCOM transceiver (iridium and Inmarsat): ARINC 741
  • •   Network: ARINC and SITA



  • •   18 ARINC 429 Receivers
  • •   7 ARINC 429 Transmitters
  • •   16 Discrete Inputs
  • •   8 Discrete Outputs
  • •   2 FULL Duplex RS-485 buses
  • •   1 CANbus
  • •   1 100BaseTx Ethernet Port (maintenance)
  • •   ASCB
  • •   Bluetooth Data Out
  • •   External Pins allocated for future growth


General Specifications

  • •   Environmental Categories: RTCA DO-160G
  • •   Software Certification: RTCA DO-178C Level B
  • •   Complex Hardware: RTCA DO-254
  • •   TSO-C113a Airborne Multipurpose Electronic Displays
  • •   TSO-C160a VDL Mode 2 Communications Equipment

 All-In-One CMU + CDU + VDR

  • •   Dimensional envelope: 5.75” wide x 4.5” high x 8.5” deep
  • •   Mounting: DZUS Rail
  • •   Weight: 6.0 lbs. (2.7 kg)
  • •   Power: 28 VDC, 25 Watts Typical
  • •   Operating Temperature: -40 to +70C

Remote CMU + VDR

  • •   Dimensional envelope: 2 MCU
  • •   Operating Temperature: -55 to +70C
  • •   Power: 28 VDC

Standalone CDU

  • •   Dimensional envelope: 5.75” wide x 4.5” high x TBD” deep
  • •   Operating Temperature: -40 to +70C
  • •   Mounting: DZUS Rail
  • •   Power: 28 VDC


For a Link to our Brochure, click here.