Black Box 4

[dik]

Is the 'Black Box' (recorder) found in aircraft independently powered?

 

[IRstuff]

The only power it should have is for the ULB

TTFN

FAQ731-376

 

[rb1957]

i'm abit surprised that we have black boxes at all ... ok, maybe as a back-up. with today's technology, i'd've thought you would broadcast your flight data to home base (no 30min limitiation) ... presumably wipe it all after a safe arrival (since no-one looks at the black box unless the airplane around it is bent or US).

 

[IRstuff]

There are upwards of 5000 aircraft over the US alone. That's a lot of bandwidth to suck up with routine data 99.9999% of the time. Total bandwidth required would be around 40 Gbps, but there's thunderstorm, solar flare, etc. potentially interfering with transmissions, not even accounting for transmitter/receiver failures, etc. Transmittal to the ground would require thousands of ultrareliable ground stations that are all networked together. Great work to get if someone wants to fund that.

Current FDRs record over 17 hrs of data on a continuous loop.


TTFN

FAQ731-376

 

[debodine]

dik:

There are two "black boxes", actually international orange in color. They are usually located in the aft area of the aircraft for survivability. (Aircraft normally don't back into the earth!)

The flight data recorder records information about the aircraft systems and the cockpit voice recorder records sounds in the cockpit. Both of them typically operate from the aircraft primary electrical AC/DC systems, from electrical busses that are not shed in an emergency. But the black boxes are not typically independently powered. I say typically because while I have a LOT of experience with many airframes, I have not seen them all so I want to be careful not to assume too much.

And as you are probably thinking by now, yes a complete electrical system failure on the aircraft will render the black boxes dead and they stop recording.

IRstuff:

On the very slight chance dik may not know the acronym ULB, allow me to explain. ULB = Underwater Locator Beacon and it is battery powered as IRstuff indicates. If the black box is immersed in water, it activates the ULB to start broadcasting locator signals.

rb1957:

I am not an FAA person, but one question I might raise if I were was how could I insure that the transmitted data could not be altered by someone at the receiving end? The typically scenario for an aircraft crash is someone finds the "black box(es)" and gives them to the on scene FAA/NTSB authorities. The black box(es), or more correctly the data they contain are not reviewed by anyone that is not permitted by that authority.

I completely agree with you that technology allows what you suggest, but the regulatory authorities may not be ready to trust it yet. )

And from the other side of the coin, you could say that the data is transmitted directly to an FAA reception point. But how many pilots do you know that would like the FAA to have a permanent record of every single control input and every single sound they made during a flight? ) )

As a final caveat I will note that I am primarily describing transport category aircraft (airline aircraft) and not everything I said above necessarily applies to either military aircraft, business aircraft or general aviation.

 

[rb1957]

uplink via NASA's TDRSS satellite network ... have a redundant copy away from the airline ... why do that ? why not send the data to the FAA, or the airowrthiness authority of the carrier ??

i was thinking that since most large transport planes have a satcom onboard, the FDR data stream would be small compared with the other traffic.

 

[eng3000]

rb1957

The datalink concept you suggest is being introduced in the 787, nevertheless significant security issues remain as raised by the FAA.

http://www.flightglobal.com/articles/2007/09/21/216948/hackers-hardwalled-from-787.html

The technology is therefore with us, but as with all such systems, someone is going to have to pay for it; right now there are a lot of cost pressures on carriers from multiple directions.

CVR (voice recording) / FDR (data recording) systems are found installed on smaller aircraft, both rotary and fixed wing, either at customer request, or increasingly through airworthiness authority mandate.

The FDR concept in particular has proved flexible and reliable in recording an increasing number of data parameters as mandated requirements have grown, and is small/light enough to fit in virtually airframe. Airworthiness authorities such as the FAA, EASA etc, do make cost/benefit analyses before making the fitting of new equipment mandatory. I suspect that the case for adopting a data link won't be with us for some time yet.

By the way, the 787 and likely the A350 will feature the newest generation of FDR called the EAFR which features an independent power supply.

http://www.reuters.com/article/pressRelease/idUS172359+24-Jul-2008+BW20080724

 

[IRstuff]

There's not an issue with any individual plane or its transmitters, it's the notion that it all has to feed into the FAA, or whatever. For the US that would mean that the FAA would need a portal that handles around 20 Gbps data bandwidth on a continual basis and that there will be infrastructure to get all the data there and reassembly it accordingly.

TTFN

FAQ731-376

 

[dik]

Thanks debodine and others: I was reading a newsclip about the Air France crash off Brazil and someone had commented that the 'black box' was connected to the electrical system and in the event of an electrical failure, the data could stop. I thought it seemed silly that it would be directly connected without an independent 'redundant' power supply. I was also wondering about a satellite uplink. I hadn't thought of data security. This should be easy to achieve. Even if the data is uploaded digitally, it's possible to purge the data on a regular basis, and automatically. It's also possible for the carrier to receive a copy of the data at the same time; they can independently analyse the material. Is it legislation that makes the FAA the recipient? I'm surprised that you could 'clog' bandwidth. A black box working in milliseconds or slower can easily be digitally uploaded at gigabits...

I was going to ask what a ULB was... slight chance <G>.

Thanks, gentlemen.

Dik

 

[IRstuff]

Again, any single box is not the problem. It's the receiving end. Picture the FAA receiving 8000 planes worth of a minimum of 88 data streams at 50 Hz at 12 bytes each. That would be a minimum of about 4 Gbps data stream, and allowing for collisions and whatnot, you're around 20 Gbps datastream capacity.

Guess where the hackers are going to concentrate their efforts. And given the large number of access points required to make that all happen, guess how often the database will be compromised.



TTFN

FAQ731-376

 

[rb1957]

ULB = Underwater Locator Beacon

as proof of concept, and to develop the technology, in parallel with an onboard (compliant) black box, broadcast at least some data (why 50Hz for all data ? how rapidly can airspeed change, 1Hz, <10 Hz ?) for some planes.

things weren't done, achieved, by saying "we can't"

 

[debodine]

dik:

You bring up some good points. I would like to expand just a bit on one of your points about a redundant, independent power supply. I am not saying it can't be done, but it would be a bit complicated for the flight data recorder, at least on older aircraft. As eng3000 noted above the 787 with a much more modern information transfer architecture may have an independently powered flight data recorder on board.

There are generally two types of data monitored by the flight data recorder. digital bits, and analog waveforms.

Both types of signals require the aircraft electrical systems to be operating (both AC and DC systems) to power the systems and the sensors. In other words, simply maintaining the operation of the flight data recorder would not be enough...all of the systems and sensors that require electrical power would also have to remain operative.

Now for the cockpit voice recorder, you only need to power the recorder itself and the microphone(s) in the cockpit. A redundant, independent power supply here might not be too difficult to implement.

I look forward to seeing the 787 versions of the "black boxes" myself so I can see what has changed.

debodine

 

[kontiki99]

A lot of data is constantly collected outside the black box now. There are many Flight Ops QA (moniker FOQA teams) constantly sifting through tons of data daily. Condition monitoring of power plants data is the norm for monitoring Maint trends and fuel efficiency. Many modern avionics computers for standard avionics systems have built in non volatile memory storage with buffers to preserve the last few moments of data recorded before trigger events (collision avoidance computers and ground prox computers often do that).

The explosion of fast and small digital avionics and data collection systems makes all sorts of data collection very possible.

Access to FOQA data cockpit voice recorder and FAA required Flight Data recorder data is heavily controlled and protected by pilot unions. In some cases an Airframe OEM (like Boeing) might really struggle to obtain safety related data from a carrier because of the ALPA agreements with the airline. The flight data recorder is only required to capture a relatively few parameters compared to what is technically possible.

Digital technology has led to some interesting shifts in how accident investigations are handled. For many years the approach has been to avoid criminal prosecution of pilots implicated in accident investigation at all cost. The argument is that pilot cooperation is indispensible for understanding what actually occurs in the cockpit.

That premise is now being challenged as we now can collect sufficient data to know if that errant control input occurred 1ms. before or after the accelerometer signal peaked. That is to say we can collect so much digital data, pilot cooperation is not so indispensible.

In an era where lower time pilots are making their way into cockpits this argument is gaining some momentum. A school bus drive may be filmed constantly as he travels his route every day. As far as I know there is no camera in any commercial cockpit recording the actions of the crew.

 

[KENAT]

Well of course there's no camera in the cockpit.

It would be dangerous if cabin crew had to leave the controls to have their liasons with the cabin crew just for the sake of privacy;-).

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

http://eng-tips.com/market.cfm?

What is Engineering anyway: faq1088-1484

 

[Dan320]

Debodine,
The idea is to interrupt the power at the moment of a crash. If the recoders were independently powered, they may survive the crash only to overwrite the interesting data with blank input.

Dan

 

[IRstuff]

That would depend on how the protocol is configured. You would want to record as much as possible, and only stop recording when you get no more data. Even TCP/IP would work in that situation. Your browser doesn't make up random webpages if there's nothing being sent, it just sits there. Likewise, if no data packets arrive, there's nothing to record.

And with a 17-hr recording capacity, a few seconds won't make make much of a dent.

TTFN

FAQ731-376

 

[dik]

I guess there was some type of messaging system in place:

The pilot sent a manual signal at 11 p.m. local time saying he was flying through an area of “CBs” – black, electrically charged cumulonimbus clouds that come with violent winds and lightning. Satellite data has shown that towering thunderheads were sending 160-kilometre-an-hour updraft winds into the jet's flight path at the time.

Ten minutes later, a cascade of problems began: Automatic messages indicate the autopilot had disengaged, a key computer system switched to alternative power and controls needed to keep the plane stable had been damaged. An alarm sounded indicating the deterioration of flight systems.

Three minutes after that, more automatic messages reported the failure of systems to monitor air speed, altitude and direction. Control of the main flight computer and wing spoilers failed as well.

The last automatic message, at 11:14 p.m., signalled loss of cabin pressure and complete electrical failure – catastrophic events in a plane that was likely already plunging toward the ocean.

“This clearly looks like the story of the airplane coming apart,” the airline industry official said. “We just don't know why it did, but that is what the investigation will show.”

Dik

 

[RPstress]

Dik - where did you get your info from? (No criticism implied - just curious.)

 

[dik]

Not sure off the top, either the BBC News or the Toronto Globe and Mail. I usually include an attribute, sorry.

Dik

 

[WKTaylor]

Anyone here have any idea as to the structural design requirements are for the FDR & CVR??

I suspect that water impact followed by submersion to -28,000 ft [7600M, estimated depths for this area] is beyond design requrements. The FDR & CVR in this mishap may be usless, for data retrieval... even if they can be found. I suspect that the ULB ["pinger" to the rest of us] may also not survive these depths.

Oh yeah. I have a strong suspicion that the US Navy SOSUS system has useful sono data on the mishap... but it may be VERY hard for the US to release classified data cross national boundaries due to the secrect nature of the SOSUS system.... and non-military nature of the incident.

Regards, Wil Taylor