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About the Air Traffic Services Message Handling
System - AMHS
AMHS (short for Air Traffic Services Message
Handling System) is a modern electronic messaging
system used to transfer and deliver air traffic flight related saftey and emergency information among the members of the global air traffic control community. It is a replacement technology for the Aeronautical Fixed
Telecommunications Network
(AFTN) which has been in operation for many decades, but which is now technically obsolete.
The messages carried by AMHS and AFTN are all defined by ICAO and are used by:
- Air Traffic Controllers
- Airports
- Airlines and flight staff
- Meteorological Offices
- Others, including emergency services ...
A variety of information is carried in these messages:
- Flight Plans & their related take off slot allocations
- Air Traffic Services Information (AIS)
- Meteorological forecasts
- Emergency signals ...
AMHS supercedes the older AFTN
which has been in operation since the 1930s, and which has serious limitations on
the type of information that it can carry.
Over time, the AFTN will be replaced by AMHS technology. Since
the AFTN is now a global network serving all states, and supports all air traffic,
it cannot be replaced in a single operational
'big bang', and therefore, the AMHS will have to
be introduced over a longer period of time, with arrangements to ensure that the AFTN
and AMHS interwork to exchange the current AFTN traffic at all times. During this
transition
period, it will be necessary to have the two systems interconnected with each other
using AFTN<>AMHS Gateways.
The way that AMHS works, and the required AFTN<>AMHS gateways are specified by the International Civil Aviation Organisation
in
ICAO
Document 9880.
Why AMHS?
As pointed out earlier, the AFTN is an ageing technology which is very specialised,
it is not based on modern standards, and has no market outside the air
traffic
control community.
The market is therefore very small. This means that the
costs associated with AFTN supply and procurement are relatively high. Furthermore, AFTN technology
is based on the
Telex protocols, and is severely limited with regards to messaging functionality and the types of information
that its messages can carry (e.g. it can carry text only in either IA5 or ITA2 form,
and of a length
of maximum 1800 characters).
AMHS, on the other hand, has a much higher functionality (which includes Security
and Directory access facilities), and the messages can carry any kind of digital information, including
text, graphics, images, files, databases, audio and video.
So, whereas the AFTN technology is sufficient for the currently defined AFTN messages,
AMHS can expand the type and functionality of messages to support a wider range
of ATC messaging requirements within a standardised framework.
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