View Full Version : FMS and ACARS

11th Feb 1999, 03:17
Could any of you ladies and gentlemen give me a layman's description of an "FMS Approach" as is being put into practice by Kestrel A320's currently?
Also is ACARS a thing of the future or just a partial success that may become the Betamax of the Air Communication world?
Many thanks

11th Feb 1999, 16:54
FMS/ILS Transitions are basically published procedures which contain vertical, horizontal and speed elements which are coded into the aircraft's FMS database. The procedures will deliver the aircraft to a position on final approach at the right height and speed to allow a transition to a normal ILS arrival. Normally this would be at about 8NM.

Some of the possible benefits are increased situational awareness to both pilots and ATC (both know the aircraft's future flightpath in advance), optimised routeings and continuous descent profiles (subject to local airspace restrictions of course), reduced environmental impact by placing routes away from populations accurately, reduced RT workload since the aircraft is cleared for the whole procedure without ATC having to issue vectoring or level instructions, etc, etc.

Trials are currently underway with limited participation at Manchester and Newcastle.

On ACARS, I think it's here to stay, mainly as an airline ops tool (how else do you get the football/cricket scores when over the Atlantic ?) but also with some possible ATC uses too.

11th Feb 1999, 16:54
Sorry, there's an echo on this machine !! Disregard.

[This message has been edited by 10W (edited 11 February 1999).]

12th Feb 1999, 04:39
Thanks 10W,
It now starts to make sense, and I suppose with the sensitivity of a second runway at Manchester and the environmental affect thereof the predictable and adjustable approach paths will be of increased importance. Does the actual FMS approach totally remove the need for vectoring so that once an aircraft is established on the FMS approach an ATCO can to all intent forget about it and pass it on the tower?

13th Feb 1999, 03:05
Once cleared on the FMS Transition, there need be no further input from ATC in terms of vectoring, descent or speed. Although tactically some of these could of course be varied in respect of other traffic. Another possible angle is that they might help introduce a simplified Radio Failure procedure. If you know exactly what the aircraft's profile is then it would be possible to manage and position all the other traffic in front of and behind the aircraft which is incommunicado. Unlike today where you would clear everything out the way and try and guess what the pilot is going to do.

I have flown onboard a trial profile into Glasgow which with the co-operation of the Centre and Airfield ATC's meant that we had a continuous descent from Cruise Level all the way to 2100' on final. We entered the FMS Transition at the Terminal Holding Fix (LANAK) and were given no further ATC instruction till we called established on final.

Canada have also done a lot of work on these procedures and Air Canada now use them on their A320 and B767 fleets into most of the Canadian major airfields. There is a lot of interest in the UK and Europe now also and once we get the concepts proven then they will no doubt spread. In busy environments such as Heathrow though their benefits will be limited but I suspect will still provide some possibilities.

15th Feb 1999, 19:25
With regards to the question about ACARS, my understanding is that ACARS based technology is here to stay for the short-term future. It will eventually be replaced by applications from the Aeronautical Telecommunications Network (ATN). A number of trials / simulations are currently being run which are related to the implementation of ATN.
If you wish to know more about one of these particular trials, have a look at the EOLIA web site (www.eolia.org). EOLIA, European pre-Operational Datalink Applications, is a multi-national project examining the initial implementation of ATC services using datalink messages passed via the ATN.

19th Feb 1999, 03:05
ACARS is the next best thing to TCAS. With the D-ATIS function pilots can find out the biggest secret in aviation...runway in use. When problems occur, a dialogue between the engineers or ops can take place without the SELCAL going off every 5 mins. FMS VNAV/LNAV is great in theory and a non-precision approach could be carried out in LNAV/VNAV if there were no map-shift, which is taken out on an ILS when the localiser is captured. Profile descents should become a reality, but tell that to the USA where ATC will cock you around throughout the approach. Coordination between ATC and pilots could make all this happen BUT....

ATC Watcher
19th Feb 1999, 14:48
ACARS is an old (fashionned )character orientated communication system owned by the airlines ( ARINC/SITA)whose messages have to travel half way around the world before it reaches it destination (Singapore or Atlanta )
ATN is a digital bit-orientated sytem which whose messages will be transmitted via ATS providers or Satelites\links and will be quasi instantanous.
The difference is about the same as between CD and US 8-tracks audio cartrides.
I leave it to you to find out what the future system will be.

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