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Automatic Messages

Tue Jun 02, 2009 11:25 am

Tragically in the news these days, the above topic re automatically-generated aircraft messages.

What are these exactly, and what systems compile and emit them? I thought all messages including ACARS were manually generated. Is the flight crew aware of the enroute broadcast of such automatic messages and their contents or are these purely technical in nature?

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RE: Automatic Messages

Tue Jun 02, 2009 11:53 am

I don't know a thing about the Airbus, but on the B747-400 the aircraft will transmit the status of a system, sometimes down to the failed component, if there is a problem in flight. These are automatic and I don't think the crew is aware of the transmission. Not sure how often or at what phase of flight these transmissions occur.

Also, the maintenance folks can request information from the aircraft using the same system.
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RE: Automatic Messages

Tue Jun 02, 2009 12:59 pm

Quoting Faro (Thread starter):
What are these exactly, and what systems compile and emit them?

The messages are primarily used for maintenance. However, there are some messages that can be triggered by exceedences, such as overspeed of flaps. In addition, there are some parameters that can be set by the company. For instance, taxi speed, IVSI below 1000' feet or 500'. If those parameters are exceeded a message will be sent. They are sent via ACARS through the data bus on the aircraft.

Quoting Faro (Thread starter):
I thought all messages including ACARS were manually generated.


Quoting Faro (Thread starter):
Is the flight crew aware of the enroute broadcast of such automatic messages and their contents or are these purely technical in nature?

No, the flight crew isn't aware of the messages (until they're called for tea and biscuits with the chief pilot). The messaging system operates in the background.

[Edited 2009-06-02 06:06:30]
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RE: Automatic Messages

Tue Jun 02, 2009 3:33 pm

This new A330's system is more advanced than most. It has constant health checks and maintenance data, much like you can get from a car by jacking in.

The A380, 787, and A350 all will have the same sort of stuff - it isn't exactly ACARS.

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RE: Automatic Messages

Tue Jun 02, 2009 10:43 pm

Airbus have a sysaten called Airman. Whenever a fault occurs the a/c will automatically transmit a msg made up of the following.

1. Cockpit effect (Any ECAM msg's the crew see)

2. Flight phase & time of event.

3. Any Central Maintenance Computer (CMC) msg's. The CMC continually talks to all the major computers on the a/c and will correlate any faults it or any other computers see's with any cockpit effects.

Armed with this info engineers on the ground can evaluate the fault with the aid of the trouble shooting manual and have the correct spares avail at the planes next port of call.

In my job in Maintenance Control I take SATCOM calls from a/c in flight with the crew asking for advice if they have a particular fault. My first response is to get a download from the a/c and then base my advice on the crew observations and what I see on the download.

As a previous poster says the airline can set up the system to download and/or print out any info their little heart desires. Once again in my line of work if a a/c does a heavy landing we get an ACARS message detailing the the landing parameters such as a/c landing weight, vertical acceleration, Rad alt & G and from this we have to evaluate if the landing was outside prescribed limits and the extent of any required maintenance actions.

Another example of a in flight report is flap speed exceedance
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RE: Automatic Messages

Wed Jun 03, 2009 8:59 am

On modern Boeing aircraft, there is a box called Digital Data Aquisition Unit (short: DFDAU), which is connected to all aircraft systems containing electronics via an ARINC 429 serial datas bus. This unit collects all sorts of information, sorts it and sends part of it (the mandatory data, as required by the authorities) onward to the Digital Flight Data Recorder (FDR) for accident investigation. There exists also the possibility that the operators install an additional non-mandatory software in the DFDAU, which then collects additional data and sends it to a Quick Access Recorder (QAR) to store it on removable disks for maintenance purpose or a transmission encoding device like ACARS or, what we have on our planes, a Wireless Quick Access Recorder (WQAR), which, while on ground only, uses the Vodaphone GSM cellphone network to send the accumulated data back to maintrol.
ACARS in turn converts the data to it's own transmission format and uses either a dedicated VHF radio or SATCOM to transmit it to a ground station while inflight.
The data collected consists of trend monitoring of engine parameters, exceedences and, lately also information about APU use on ground for economical reasons (pilots and ground crew are to use ground power if possible because it is cheaper. Any APU use of more than 20 minutes requires a justification, e.g. no ground power available, which would be an issue between the airline and the ground handler, who by contract has to provide ground power, or maintenance).
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