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Malaysia Airlines flight MH370 makes it clear: we need to rethink black boxes

theguardian.com

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Re: Malaysia Airlines flight MH370 makes it clear: we need to rethink black boxes

#81

Post by wglb »

fnordfnordfnord wrote: post #76
yaakov34 wrote: post #20

Let's start estimating the technical challenge here (we're supposed to be techies, after all). Bandwidth: quick googling shows that a flight data recorder records between 64 and 256 12-bit words a second, i.e. 1-3 kbps. Browsing http://en.wikipedia.org/wiki/Bit_rate shows that another 2-8 kbps is needed for voice recording (from one microphone). Let's call it 10 kpbs all together. Number of simultaneous connections:…

Why use satellites? There is plenty of long-range terrestrial radio tech that could do the job. Land-based and or even cargo ship based listening posts would be much cheaper. Aircraft-to-aircraft comms could also potentially do the job. Granted, aircraft fly high in the air, but there are no line-of-sight problems as with terrestrial radio links, so even high frequency comms are possible.

Keep in mind that over-the-horizon radio communication is subject to the vagaries of the ionosphere and is not totally reliable. Further, there is a day/night difference, and a dependence on latitude. Line of sight at 30000 feet is about 200 miles, so there are huge areas where everything is over your horizon.

Re: Malaysia Airlines flight MH370 makes it clear: we need to rethink black boxes

#82

Post by tzs »

m4x wrote: post #34
objclxt wrote: post #15

Earlier quoted context omitted.

I pointed this out somewhere else, but satellites aren't particularly helpful because you won't be able to transmit to them when you most need it , which is when there are problems with the plane. It's still highly likely that you're still going to end up with planes going 'off the grid' so to speak. You could lose power, stopping you from transmitting telemetric data. Or there could be a cabin depressurization or br…

Real time telemetry via satellite could definitely be useful in some situations. The Air France crash could have been prevented if somebody on the ground had taken a look at the data from the plane, realised that the junior pilot has been pulling up the whole time, and made the crew aware of it. That was one of the worst crashes in history and there was never even a problem with the plane. All they needed to save the…

> The Air France crash could have been prevented if somebody on the ground had taken a look at the data from the plane, realised that the junior pilot has been pulling up the whole time, and made the crew aware of it

There are something like 10k commercial flights in the air at a given time around the world. How would that somebody on the ground know to look at that particular plane's telemetry?

Re: Malaysia Airlines flight MH370 makes it clear: we need to rethink black boxes

#83

Post by Perdition »

fnordfnordfnord wrote: post #76
yaakov34 wrote: post #20

Let's start estimating the technical challenge here (we're supposed to be techies, after all). Bandwidth: quick googling shows that a flight data recorder records between 64 and 256 12-bit words a second, i.e. 1-3 kbps. Browsing http://en.wikipedia.org/wiki/Bit_rate shows that another 2-8 kbps is needed for voice recording (from one microphone). Let's call it 10 kpbs all together. Number of simultaneous connections:…

Why use satellites? There is plenty of long-range terrestrial radio tech that could do the job. Land-based and or even cargo ship based listening posts would be much cheaper. Aircraft-to-aircraft comms could also potentially do the job. Granted, aircraft fly high in the air, but there are no line-of-sight problems as with terrestrial radio links, so even high frequency comms are possible.

There is nothing reliable for oceanic flights but shortwave, which doesn't have the bandwidth available for streaming.

At 40,000 ft altitude the horizon is still only ~240 miles, which will still give LOS problems for VHF and above, particularly in bad weather.

Re: Malaysia Airlines flight MH370 makes it clear: we need to rethink black boxes

#84

Post by alexeisadeski3 »

AmVess wrote: post #46
pcurve wrote: post #23

Earlier quoted context omitted.

In both Air France 447 and Malay Air MH370, local authorities found traces of crash / wreckage within 1-2 days. People don't fully appreciate how difficult it is to find anything in the middle of ocean when there's no visual trace. Even if you can narrow down the point of impact within a few square miles, you won't know for sure until you get underwater equipment. When you're dealing with deep underwater recovery, al…

It's difficult even on land. I recall an accident that involved a twin engine light aircraft that vanished in the middle of the night in Alaska perhaps 20 years ago. Search parties searched for quite some time, but gave up. Five years later, the plane was found in the woods some 100 meters away from a fairly frequently traveled two-lane road.

Forget Alaska, there are crashes in Nevada which haven't been found after decades.

A large airliner would be easier to find on land though - just look for the glow.

Re: Malaysia Airlines flight MH370 makes it clear: we need to rethink black boxes

#85

Post by WalterBright »

WalterBright wrote: post #42
Zancarius wrote: post #24

Earlier quoted context omitted.

I was hoping you'd chime in on one of these discussions, given your history in the aircraft industry. What are your thoughts on the rather knee-jerk articles as of late that seem to think that some form of streaming technology is somehow absolutely imperative, and how might that compare to the tried-and-tested flight recorders given what we know from AF447 sharing periodic updates as to its status?

My knowledge of what is and isn't practical with streaming technology isn't much better than that of a layperson. I do find the aviation industry to be sometimes peculiarly behind the times. For example, a few years ago, I wondered online why airports did not have constant video recording of the runway and taxiways. Such would have been enormously helpful in solving many accidents, such as the SST crash. But an airli…

A lot of accidents happen on the runway or shortly after. Video will tell a lot of things that telemetry won't - visibility, runway incursions, just where the airplane lifted off, ice on the wings, fire or smoke, any missing parts (!), open doors, working lights, bird strikes, etc. It can also be a backup if the telemetry is lost, such as speed, position of the flaps, problems with the landing gear, etc.

Re: Malaysia Airlines flight MH370 makes it clear: we need to rethink black boxes

#86

Post by jarek »

tzs wrote: post #82
m4x wrote: post #34

Earlier quoted context omitted.

Real time telemetry via satellite could definitely be useful in some situations. The Air France crash could have been prevented if somebody on the ground had taken a look at the data from the plane, realised that the junior pilot has been pulling up the whole time, and made the crew aware of it. That was one of the worst crashes in history and there was never even a problem with the plane. All they needed to save the…

> The Air France crash could have been prevented if somebody on the ground had taken a look at the data from the plane, realised that the junior pilot has been pulling up the whole time, and made the crew aware of it There are something like 10k commercial flights in the air at a given time around the world. How would that somebody on the ground know to look at that particular plane's telemetry?

This is the least difficult part of the whole scheme. A program looking at all incoming data and picking out extraordinary data (in AF 447's case, for instance the stall warnings) to flag for a human operator to inspect would help greatly. There'd be a lot of false alarms but still vastly less work than looking at telemetry of every plane ever. (And even if - 10k is around the number of employees of one mid-size airport - hardly undoable if you wanted.)

Re: Malaysia Airlines flight MH370 makes it clear: we need to rethink black boxes

#87

Post by m4x »

gvb wrote: post #79
m4x wrote: post #34

Earlier quoted context omitted.

Real time telemetry via satellite could definitely be useful in some situations. The Air France crash could have been prevented if somebody on the ground had taken a look at the data from the plane, realised that the junior pilot has been pulling up the whole time, and made the crew aware of it. That was one of the worst crashes in history and there was never even a problem with the plane. All they needed to save the…

a) Nobody on the ground knew AF447 was in trouble. The aircraft never broadcast a declaration of an emergency. b) Even if there was telemetry that sent the aircraft control inputs and instrumentation to the ground, with thousands of aircraft in the air, nobody would have been watching AF447's telemetry, waiting for Something Bad to happen. c) It was about four minutes between when the aircraft got in trouble and when…

So ask yourself why it never broadcast a declaration of emergency - the autopilot had disengaged due to an instrument malfunction, which should have generated an automated broadcast on the spot. Then somebody could start monitoring the telemetry from the the one (or five, or some other low number of planes) that were in trouble of some sort.

It would also be quite simple to be running a bunch of automated tests on the telemetry from every plane in the sky and flagging anything out of spec. AF447 fell into the ocean. It's pretty fucking simple for a computer to monitor the altitude of a plane and say "one of your planes has significantly deviated from it's target altitude".

And "highly unlikely they would have been able to identify the cause" seems highly unlikely. The plane was stalled, and somebody was pulling up as much as possible. Is it really hard to imagine a pilot on the ground being unable to spot what was going on?

Even the captain on board figured it out quickly once he was summoned - the problem was flagging the issue/asking for help was done solely at the pilots discretion and they chose not to tell any body what was going on until it was too late

Re: Malaysia Airlines flight MH370 makes it clear: we need to rethink black boxes

#88

Post by fnordfnordfnord »

wglb wrote: post #81
fnordfnordfnord wrote: post #76

Earlier quoted context omitted.

Why use satellites? There is plenty of long-range terrestrial radio tech that could do the job. Land-based and or even cargo ship based listening posts would be much cheaper. Aircraft-to-aircraft comms could also potentially do the job. Granted, aircraft fly high in the air, but there are no line-of-sight problems as with terrestrial radio links, so even high frequency comms are possible.

Keep in mind that over-the-horizon radio communication is subject to the vagaries of the ionosphere and is not totally reliable. Further, there is a day/night difference, and a dependence on latitude. Line of sight at 30000 feet is about 200 miles, so there are huge areas where everything is over your horizon.

But don't most actual aircraft flight paths tend to stay near land? For those flights that must go over that horizon, couldn't they fail over to a lower freq / lower bandwidth channel, when needed; while still keeping near real-time status updates?

Or connect via another aircraft who is further behind them but on a similar flight plan.

Here is probably one of the worst flight paths for this type of potential comms http://flightaware.com/live/flight/UAL888/history/20140310/0...

I had intended to use that to support my notion that aircraft tend to stay near land. I've flown that route several times and each time we flew an arc that kept us near or overland. Like this, but never in Russian airspace. http://flightaware.com/live/flight/CCA985/history/20140309/0...

Man, these guys are all over the place. I may have to reform my ideas about flight paths.

Re: Malaysia Airlines flight MH370 makes it clear: we need to rethink black boxes

#89

Post by Zancarius »

melling wrote: post #39
Zancarius wrote: post #27

Earlier quoted context omitted.

> Btw, what's the transmission range of a black box? If it's 10,000 ft down, how close do you have to be to hear it? Apparently 2-3 kilometers according to [1], which I found in the comments from here [2]. [1] http://www.hydro-international.com/issues/articles/id1098-Ai... [2] http://www.aticourses.com/blog/index.php/tag/side-scan-sonar...

So, if the plane is traveling at 13 km a minutes and you have a 20 minute window, it's going to take a long time to find it. Doesn't the technology exist to detect low power signals from a much greater distance? The US military must be able to do it?

> Doesn't the technology exist to detect low power signals from a much greater distance?

The pingers are sonar (well, sonic, but detected with sonar), with all the limitations that implies.

Re: Malaysia Airlines flight MH370 makes it clear: we need to rethink black boxes

#90

Post by Maxious »

adanto6840 wrote: post #61
melling wrote: post #39

Earlier quoted context omitted.

So, if the plane is traveling at 13 km a minutes and you have a 20 minute window, it's going to take a long time to find it. Doesn't the technology exist to detect low power signals from a much greater distance? The US military must be able to do it?

I'm more surprised that there isn't a single (imagery-related) satellite that would, over the last 24 hours or so, have taken imagery (or been able to be re-assigned to do so) of the area(s) of interest. If for nothing else than to rule out some areas / possible outcomes... But yeah, very far out of my realm of expertise, though I do hope to finish my PPL fairly soon & am an avid AVHerald & LiveATC follower! :-) http…

You can look at Landsat imagery for some of the search area http://www.geosage.com/Special/Landsat8_Flight370.pdf
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