<s>
Controller	B-Device
–	I-Device
pilot	I-Device
data	I-Device
link	I-Device
communications	I-Device
(	O
CPDLC	B-Device
)	O
,	O
also	O
referred	O
to	O
as	O
controller	O
pilot	O
data	O
link	O
(	O
CPDL	O
)	O
,	O
is	O
a	O
method	O
by	O
which	O
air	B-Application
traffic	I-Application
controllers	I-Application
can	O
communicate	O
with	O
pilots	O
over	O
a	O
datalink	O
system	O
.	O
</s>
<s>
The	O
standard	O
method	O
of	O
communication	O
between	O
an	O
air	B-Application
traffic	I-Application
controller	I-Application
and	O
a	O
pilot	O
is	O
voice	O
radio	O
,	O
using	O
either	O
VHF	B-Algorithm
bands	I-Algorithm
for	O
line-of-sight	O
communication	O
or	O
HF	B-Algorithm
bands	O
for	O
long-distance	O
communication	O
(	O
such	O
as	O
that	O
provided	O
by	O
Shanwick	O
Oceanic	O
Control	O
)	O
.	O
</s>
<s>
As	O
the	O
number	O
of	O
flights	O
air	B-Application
traffic	I-Application
controllers	I-Application
must	O
handle	O
is	O
steadily	O
increasing	O
(	O
for	O
instance	O
,	O
Shanwick	O
handled	O
414,570	O
flights	O
in	O
2007	O
,	O
an	O
increase	O
of	O
5%	O
-	O
or	O
22,000	O
flights	O
-	O
from	O
2006	O
)	O
,	O
the	O
number	O
of	O
pilots	O
tuned	O
to	O
a	O
particular	O
station	O
also	O
increases	O
.	O
</s>
<s>
Controller	O
–	O
pilot	O
data	O
link	O
communication	O
(	O
CPDLC	B-Device
)	O
is	O
a	O
means	O
of	O
communication	O
between	O
controller	O
and	O
pilot	O
,	O
using	O
data	O
link	O
for	O
ATC	O
communication	O
.	O
</s>
<s>
The	O
CPDLC	B-Device
application	O
provides	O
air-ground	O
data	O
communication	O
for	O
the	O
ATC	O
service	O
.	O
</s>
<s>
An	O
auxiliary	O
capability	O
is	O
provided	O
to	O
allow	O
a	O
ground	O
system	O
to	O
use	O
data	O
link	O
to	O
forward	O
a	O
CPDLC	B-Device
message	O
to	O
another	O
ground	O
system	O
.	O
</s>
<s>
All	O
exchanges	O
of	O
CPDLC	B-Device
messages	O
between	O
pilot	O
and	O
controller	O
can	O
be	O
viewed	O
as	O
dialogues	O
.	O
</s>
<s>
The	O
CPDLC	B-Device
application	O
has	O
three	O
primary	O
functions	O
:	O
</s>
<s>
Simulations	O
carried	O
out	O
at	O
the	O
Federal	O
Aviation	O
Administration	O
's	O
William	O
J	O
.	O
Hughes	O
Technical	O
Center	O
have	O
shown	O
that	O
the	O
use	O
of	O
CPDLC	B-Device
meant	O
that	O
"	O
the	O
voice	O
channel	O
occupancy	O
was	O
decreased	O
by	O
75	O
percent	O
during	O
realistic	O
operations	O
in	O
busy	O
en	O
route	O
airspace	O
.	O
</s>
<s>
Today	O
,	O
there	O
are	O
two	O
main	O
implementations	O
of	O
CPDLC	B-Device
:	O
</s>
<s>
FANS-1/A	O
is	O
an	O
ACARS	B-Algorithm
based	O
service	O
and	O
,	O
given	O
its	O
oceanic	O
use	O
,	O
mainly	O
uses	O
satellite	O
communications	O
provided	O
by	O
the	O
Inmarsat	O
Data-2	O
(	O
Classic	O
Aero	O
)	O
service	O
.	O
</s>
<s>
The	O
ICAO	O
Doc	O
9705	O
compliant	O
ATN/CPDLC	O
system	O
,	O
which	O
is	O
operational	O
at	O
Eurocontrol	O
's	O
Maastricht	O
Upper	O
Airspace	O
Control	O
Centre	O
and	O
has	O
now	O
been	O
extended	O
by	O
Eurocontrol	O
's	O
Link	O
2000+	O
Programme	O
to	O
many	O
other	O
European	O
Flight	O
Information	O
Regions	O
(	O
FIRs	O
)	O
.	O
</s>
<s>
The	O
VDL	B-Algorithm
Mode	I-Algorithm
2	I-Algorithm
networks	O
operated	O
by	O
ARINC	O
and	O
SITA	O
are	O
used	O
to	O
support	O
the	O
European	O
ATN/CPDLC	O
service	O
.	O
</s>
<s>
The	O
following	O
UACs	O
offer	O
CPDLC	B-Device
services	O
:	O
</s>
<s>
Following	O
the	O
PETAL	O
I	O
and	O
II	O
(	O
Preliminary	O
Eurocontrol	O
Trial	O
Air	O
Ground	O
Data	O
link	O
)	O
trials	O
in	O
1995	O
including	O
NEAN	O
(	O
VDL	B-Algorithm
Mode	I-Algorithm
4	I-Algorithm
)	O
,	O
today	O
both	O
ATN	O
(	O
VDL	B-Algorithm
Mode	I-Algorithm
2	I-Algorithm
)	O
and	O
FANS	O
1/A	O
services	O
are	O
supported	O
.	O
</s>
<s>
More	O
than	O
40	O
major	O
airlines	O
participate	O
in	O
the	O
CPDLC	B-Device
programme	O
with	O
Maastricht	O
UAC	O
.	O
</s>
<s>
More	O
than	O
30,000	O
LOG-ONs	O
were	O
reported	O
in	O
2007	O
,	O
leading	O
to	O
over	O
82,000	O
CPDLC	B-Device
uplinks	O
,	O
each	O
saving	O
precious	O
frequency	O
time	O
.	O
</s>
<s>
CPDLC	B-Device
will	O
probably	O
be	O
a	O
major	O
enabler	O
for	O
following	O
on	O
projects	O
as	O
monitor	O
message	O
,	O
route	O
clearance	O
uplink	O
,	O
2-4	O
D	O
trajectories	O
,	O
continuous	O
descent	O
approaches	O
,	O
and	O
constraint	O
coordination	O
also	O
.	O
</s>
<s>
All	O
CPDLC	B-Device
deployments	O
must	O
be	O
supported	O
by	O
an	O
approved	O
safety	O
case	O
demonstrating	O
that	O
all	O
safety	O
objectives	O
for	O
the	O
applicable	O
airspace	O
have	O
been	O
met	O
.	O
</s>
<s>
EUROCAE	O
ED-120	O
(	O
RTCA	O
DO-290	O
)	O
is	O
the	O
safety	O
and	O
performance	O
requirements	O
(	O
SPR	O
)	O
for	O
continental	O
airspace	O
and	O
should	O
be	O
consulted	O
for	O
the	O
safety	O
objectives	O
relevant	O
to	O
the	O
use	O
of	O
CPDLC	B-Device
in	O
continental	O
airspace	O
.	O
</s>
<s>
ED-120	O
provides	O
a	O
hazard	O
analysis	O
and	O
identifies	O
the	O
hazards	O
applicable	O
to	O
systems	O
implementing	O
the	O
ATC	O
services	O
that	O
CPDLC	B-Device
deployments	O
are	O
currently	O
providing	O
.	O
</s>
<s>
A	O
consequence	O
of	O
these	O
requirements	O
is	O
that	O
CPDLC	B-Device
implementations	O
,	O
both	O
on	O
aircraft	O
and	O
at	O
ATC	O
centres	O
,	O
must	O
have	O
access	O
to	O
an	O
accurate	O
clock	O
(	O
to	O
within	O
1	O
second	O
of	O
UTC	O
)	O
.	O
</s>
