**DAG-TM -- Controller-Pilot DataLink Communications (CPDLC)**

# Document Purpose

Provide DAG-TM pilot participants with:

background and general information on CPDLC,

information on DAG-TM ground-side CPDLC operation, and

instructions on DAG-TM air-side CPDLC operation.

# Background

Voice radio messages between pilots and aircraft traffic controllers are
exchanged continuously. The Controller-Pilot Data Link Communication
system reduces the number of voice messages by using a special link for
routine messages. These messages are digitally displayed on a computer
screen in the cockpit. Shifting routine transmissions from voice to data
link communications frees up voice frequencies and reduces delays. CPDLC
achieved initial daily use by controllers at Miami Center on October 7,
2002. American Airlines is the CPDLC launch airline with 20 aircraft
operating in the Miami Center airspace. By the end of 2003, Miami Center
will be controlling CPDLC equipped aircraft from American Airlines,
Delta Air Lines, Continental Airlines, FedEx, and the U.S. Air Force.
(FAA, 2003)![](media/image1.jpeg){width="2.7291666666666665in"
height="1.8083333333333333in"}

In DAG-TM research, CPDLC is a ***test variable***, simply meaning
(*from the DAG-TM pilot perspective*) that there will be scenarios where
it is present and used operationally, and other scenarios where it is
not present.

**DAG-TM Ground-Side CPDLC Operations**

During DAG-TM flight scenarios, Air Traffic Controllers (ATC) manage the
study airspace from the Airspace Operations Lab (AOL). The controllers
interact with:

single-aircraft operator, MACS/CDTI pilot stations (pilot participants)

single-aircraft operator, ACFS/CDTI simulator (pilot participants)

multi-aircraft operator, pseudo-pilot MACS station operators
(confederate pilots)

Multi-aircraft operators manage between 5 and 25 aircraft at any one
time. As far as ATC is concerned, however, all aircraft within their
airspace are individually controlled by a unique flight crew.

Like the pilots, the controllers have a suite of advanced tools
available to them for completing their tasks during a scenario. Several
of these ATC tools are also ***test variables***, including CPDLC, and
may or may not be available to them on any given scenario.

The DAG-TM CPDLC ground-side interface and operational characteristics
are being modeled on that which is currently in place at Miami ARTCC.
Using a panel on the ATC radar display, along with a trackball and
keyboard, controllers can quickly transmit and manage a variety of
DataLink operations. Figures 2 though 4 illustrate different CPDLC
interface elements. In short, the controller typically enters a DataLink
two-letter shortcut code, slews over the aircraft of interest, and
clicks the trackball to send the message.

![](media/image2.png){width="4.479166666666667in"
height="3.0701388888888888in"}

![](media/image3.png){width="4.001388888888889in"
height="3.9569444444444444in"}

![](media/image4.png){width="3.627083333333333in"
height="3.0972222222222223in"}

**DAG-TM Air-Side CPDLC Operations**

During DAG-TM flight scenarios, single-aircraft operator, MACS/CDTI and
ACFS/CDTI pilot participants will 'fly' scenarios -- en route through
the study airspace, or arrivals into DFW. One element that will be
present on specific scenarios is CPDLC. On the MACS flight deck, the
interface consists of two panels -- a DataLink Controls panel, and a
DataLink Message panel. (The use of CPDLC hardware on the ACFS flight
deck will be covered during hands-on
training.)![](media/image5.png){width="3.4569444444444444in"
height="1.5659722222222223in"}

DataLink messages (uplinks from ATC) must be responded to,
electronically, within 40 seconds of receipt on the flight deck. The
controller receives an alert if more than 40 seconds transpire without a
DataLink "ACCEPT" response from the aircraft. In the event the flight
deck needs to reject a DataLinked instruction, the "REJECT" button
should be activated (see Note 1, below).

"**Accept**(ing)" a CPDLC message on a MACS flight deck will map to an
appropriate response on the ground-side -- for example WILCO or ROGER --
based on the type of instruction received from the ground.

"**Load**(ing)" a CPDLC message, if related to route, will update the
CDU accordingly, and require an "EXEC(ute)" on the keypad. DAG-TM
MACS/CDTI pilots should ensure that the route change accurately reflects
on the CDTI.

"**Reject**(ing)" a CPDLC message on a MACS flight deck will also map to
an appropriate response on the ground-side -- for example UNABLE or
NEGATIVE -- based on the type of instruction received from the ground
(see Note 1, below).

When a traditional voice communication is received, for example to
change frequency, or execute a specific heading, etc., DAG-TM pilots
should respond by voice in the traditional, expected manner, and comply
with the ATC instruction/s accordingly. In the case of a frequency
change (from one ATC sector to another), you should acknowledge the
message from the departing sector, and contact the new sector-controller
frequency in the customary manner.

**Uplink messages** generated by ATC are limited to lateral route
changes (for example, a direct-to), speed advisories, and RTA meter fix
crossing requirements. ***PDA Spacing instructions will be via voice
only.*** Standard altitude restrictions apply at all times.

Upon receipt on the air-side, the flight deck must either accept or
reject the message instructions. After "ACCEPT(ing)" a DataLink message,
"EXEC(cute)" the modifications in the CDU, or in the case of an RTA,
"ACCEPT" the message, set up and execute the RTA on the CDTI, and then
"EXEC(ute)" the procedure in the CDU. If the message instructions need
to be rejected, click the "REJECT" button and contact ATC (see Note 1,
below).

**Downlink messages** generated by the flight deck are limited to route
modifications trial-planned using the CDTI. Upon receipt on the
ground-side, ATC is required to either accept or reject the route
modification. Upon receipt of an uplinked CPDLC "Accept" message on the
flight deck, the route modification must be "EXEC(uted)" on the CDU. If
ATC rejects the route modification request, they are required to contact
the flight deck and address the circumstances. On the flight deck the
route modification in the CDTI should be removed by turning the RAT off.

**Note 01 -- REJECT(ing) a DataLink Instruction:** If at any time it is
necessary for you to reject a CPDLC transmitted instruction from ATC,
click the "REJECT" button and contact ATC as soon as is practical,
referencing the DataLink message, and the reason/s for your aircraft's
inability to comply. Your message should take the following approximate
form:

> "*Center, American 123. Reference DataLink message, am unable to meet
> crossing restriction at Hyde, please advise.*"

![](media/image6.png){width="2.875in"
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