drexotica
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Aircraft Telemetry Data Rates

Thu Jul 11, 2013 4:54 am

I am curious if anyone knows the following - on a modern widebody aircraft, what are the common data rates observed between the flying aircraft and the manufacturer or the airline itself?

I've done a bit of searching and found one company (LMS) that provides a data acquisition system during testing; I read that they had the capability of collecting data from roughly 136 sensors and transducers, with each sensor having a dynamic range of 24 bits, with sample frequencies of 80kHz. This works out to roughly 32MB/sec, or ~120GB/hour (1TB/8 hours).

For operational aircraft, how many sensors readings are transmitted back to the manufacturer, at what resolution, and at what frequency?

The reason I ask? I recently read some information in the context of discussing "Big Data" problems and some outrageous figures were being reported. Specifically: "For every 30 minutes that a Boeing jet engine runs, the system creates 10 terabytes of operations information".

[sigh]

This statement is tragic on many levels ...

In any event, thanks for any info or insight.
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mandala499
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RE: Aircraft Telemetry Data Rates

Thu Jul 11, 2013 7:51 am

Quoting drexotica (Thread starter):
For operational aircraft, how many sensors readings are transmitted back to the manufacturer, at what resolution, and at what frequency?

For normal operations, they are usually periodic reports (snapshots), and tolerance exceedances.
For flight testing, yes they can go up to a ridiculous number, and wireless telemetry I know are done in several frequency bands (I know one that transmits in S-Band) to a ground station, but these are done only when continuous telemetry relay is required.

Time resolution is anything from per 30 seconds to per 20 minutes, depending on what the airline's choice.
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zeke
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RE: Aircraft Telemetry Data Rates

Thu Jul 11, 2013 8:52 am

Quoting drexotica (Thread starter):
For operational aircraft, how many sensors readings are transmitted back to the manufacturer, at what resolution, and at what frequency?

Probably nothing directly to the manufacturer, normally it goes to the operator, and then if the operator has paid for a service it will go to the manufacturer. It is very low frequency, and done via ACARS. What and how it get transmitted is up to the operator. Some airlines have no capability to transmit anything from their aircraft.

Quoting drexotica (Thread starter):
The reason I ask? I recently read some information in the context of discussing "Big Data" problems and some outrageous figures were being reported. Specifically: "For every 30 minutes that a Boeing jet engine runs, the system creates 10 terabytes of operations information".

Aircraft have quick access recorders that have a lot of data stored, normally on magneto optical drives, one mag/op drive will hold 3-5 days of data. The trend now if for this data to be sent via WiFi to the operator while the aircraft is at the gate. A large airline might generate GBs a day, 20 TB/hr of information I think is way over the top.

We are in the process of moving to a 3G/4G/WiFi solution to replace the drives on the aircraft, similar to this concept
http://www.aviationtoday.com/Assets/TELEDYNE-TECHRERPOT.pdf
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nomadd22
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RE: Aircraft Telemetry Data Rates

Thu Jul 11, 2013 11:46 am

Quoting drexotica (Thread starter):
I've done a bit of searching and found one company (LMS) that provides a data acquisition system during testing; I read that they had the capability of collecting data from roughly 136 sensors and transducers, with each sensor having a dynamic range of 24 bits, with sample frequencies of 80kHz. This works out to roughly 32MB/sec, or ~120GB/hour (1TB/8 hours).

Sample frequencies of 80khz? There might be things you need that kind of sampling for, but aircraft telemetry would probably not require 1/1,000th that sort of period.
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Klaus
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RE: Aircraft Telemetry Data Rates

Fri Jul 12, 2013 10:54 am



Quoting drexotica (Thread starter):
The reason I ask? I recently read some information in the context of discussing "Big Data" problems and some outrageous figures were being reported. Specifically: "For every 30 minutes that a Boeing jet engine runs, the system creates 10 terabytes of operations information".

That's actually quite plausible. The high data acquisition rates are primarily needed for live engine control in the FADECs. There is just no practical way to store or transmit that raw data in flight normally – and usually no need to do that in the first place. In real life, the massive amounts of data from the sensors will be filtered, analyzed and only exceptional events or longer-term trends are actually stored, with likely just again a smaller amount being transmitted via low-speed in-flight data links.

AF447 was an example of how little bandwidth these links usually have / had – there were only very basic indications of what had happened because the plane transmitted so little data during its stalled descent:
http://www.flight.org/blog/2009/06/0...rance-flight-447-unofficial-acars/

Had there be a wider data link, the extremely expensive deep-sea search for the flight recorders might not have been as crucial for the investigation as it was.

It is possible that some airlines with in-flight internet connections use these much wider channels for telemetry transmission as well, but I wouldn't bet on it.

[Edited 2013-07-12 03:55:26]

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