Air France Crash (2009): Investigators homing in on black boxes

Recent news article: investigators are getting closer to locating the black boxes from last year’s Air France crash in the south Atlantic:

Air France crash ‘black box site found in Atlantic’:

Still no guarantee that they’ll actually be able to find and recover them:

I hope they find these black boxes! There is not much more information to be gleaned from the ACARS messages and the few existing pieces of found debris. I know the BEA is collecting data on other A330/340 airspeed indicator malfunction events, but I’m not sure that any of them can tell us why that plane crashed.

One thing that I hope comes out of all this is a change in the regulations regarding the length of time the pingers are qualified for (I don’t believe it’s technologically all that challenging to extend it), and perhaps the recommendation to add additional pingers to other parts of the fuselage.

Amazingly enough, there is speculation now that the aircraft may have turned around prior to crashing; analysis of the sonar and pinger data from last summer seem to be pointing to an area south west of the last known location of the plane. They need to find those recorders! What did the pilots know about their situation? Why did they turn around? What happened!

This case is so fascinating.

I would hope for the onboard systems to be supplemented/replaced by continuous satellite data links, basically expanding ACARS to include all flight data and all cockpit voice recordings. Nothing would be lost and all data would be available immediately.

The most likely reason for them to turn around would be to avoid the thunderstorms that were in the area, but it would definitely be good to know just what happened up there.

I thought the box(es) had some sort of radio beacon that would only last as long as there was battery power. After that, there wasn’t a chance of finding them.

If this is the case, why weren’t they able to find them immediately? And how would they possibly find anything now.

The recorders are designed (required) to have radio beacons - pingers - which can broadcast for a minimum of 30 days off of battery power. Ideally, the pinger is “heard” by searching aircraft and/or ships, and the location of the underwater wreckage is found within those 30 days.

It seems that, during that initial search, some random pings were picked up, but no definite location was found. Analysis of that data and the regions of ocean being searched seems to have pointed to the sounds originating from an area further away than expected (although still within the initial search zone). Using that idea, they will be searching the area using other technologies to try and find the metal of the plane; in theory, if the tail section can be found, the recorders will be as well, since that’s where the recorders are attached to the plane and they may not have become separated.

I’m not really familiar with navigation and communication; would there not have been a way for the pilots to inform either the INTOL or TASIL waypoints that they were turning around/changing course (if that’s what happened)? Would they not have been able to communicate to other aircraft in the area? It seems to me they would have had time, but perhaps a million things started going wrong (including potentially communication system failures) and they just weren’t able to. The curiosity is getting to me… it’s just such a mystery, and I hate waiting for answers!

Wreckage and bodies just found:

Not sure I understand this; I thought radio waves didn’t transmit through water. How would a radio beacon pinger be “heard” if it’s underwater? But maybe the pinger has a sound-projecting (sonar) element as well?

And if the beacon(s) were designed to detach and float, it seems likely they’d soon drift far enough to be useless in pinpointing the crash site.

If they didn’t, submarines would need to surface every time they needed to send or receive a message.

Regarding radio waves and water: I found this:

It sounds like radio transmission in salt water is challenging, unless you’re using extremely low frequency transmissions (which explains why ELF transmissions are used to communicate with subs).

They did, up and until the innovations of radio buoys (that did the surfacing for them), and later, ELF (detailed above).

They do, if they want to send/receive a message of any significant complexity. High-frequency radio waves don’t penetrate water very well at all. As kenobi 65 notes, ELF is used to send an extremely brief “HEY” message; that’s about all you can send in a reasonable time frame using ELF radio. But it’s enough so that the subs know they need to surface so they can pick up higher frequency radio communications, which can be used to exchange meaninful messages.

The fact is, it’s much more common for airplanes to go down over land than sea, and in a land crash finding and retrieving the black boxes is not as difficult as retrieving from the ocean depths.

They have to balance power, weight, and ruggedness - black boxes, after all, have to survive an airplane crash and possible subsequent fire. At least the data does - accessory parts can burn away as long as the information survives.

Well, not lost unless the satellite link went down - ideally you’d like both systems if possible, to maximize data gathering and minimize chances of that data being lost.

The airplane went down in water deeper than the underwater beacon can transit through - and yes, they have both radio and underwater beacons.

Searcher did lower listening devices down into the ocean in hopes of picking up the signal, but were not successful in locating the beacons.

And, of course, you can find them after the signal stops… they’re bright orange, for goodness sakes, very visible. If you’re in line of sight. And close enough. They’re just a lot harder to find without the beacon.

And yes, there is a very good chance the data is still intact on those recorders, even after a couple years immersed in salt water.

The first priority is to fly the airplane. If the crap was really hitting the fan they might have been so busy flying they didn’t have time for talking.

On top of that - over the major oceans there aren’t a lot of navigational beacons or radio relays. Sure, they could talk to other airplanes, if they happened to be on the same frequency (and the emergency channel 121.5 is supposed to be monitored by everyone) but if no one was in range, and that’s possible, they simply wouldn’t be heard.

The Nova show that aired just this year seems to have a pretty good handle on what happened, but the black boxes would confirm the speculation.

Basically, as I understand it, the contributing factors were:[ol][li]In the fly-by-wire console, when the automatic systems reduce power, the throttle handles don’t move accordingly, so the indication is only on the display[]The minimal on-board radar has a short range and may have been blinded by a near storm that hid the bigger one right behind it[]The likely presence of supercooled moisture caused all three pitot tubes (air speed indicators) to fail at once by plugging up the orifice faster than the heaters could melt the ice.[/ol]So when the failures were detected by the computer, it shut down the automatic systems, since without any airspeed indication, it would have no way of knowing the correct speed. With so much going on in the cockpit, the pilots didn’t notice that the plane’s speed had already been reduced by the autopilot just before they took over (because of the storm), and before they had gone far, the plane stalled and fell out of the sky.[/li]
According to the NOVA show, the correct way to handle the situation would have been to put the tail elevator in a 5 degree up position, bringing the nose up, and set the speed to 85%, the best compromise if your speed is unknown. However, the pilots only had seconds, not minutes, to do that before a stall, and they didn’t react in time.

It seems unlikely that they tried to turn back. The turning maneuver alone would add a dangerous component. Let’s hope the black boxes will settle this.

The Master Speaks on black boxes, including a passing reference to gleaning usable data from a box that had been submerged in sea water for seven years:

I suspect that Cecil’s 1997 report referred to tape-based units. Modern boxes use solid-state storage and the vulnerability to damage is, while maybe not better (I wouldn’t call flash memory indestructable), at least different.

There’s some talk about using redundant units, and one of the dual units would detach before a crash using a deceleration sensor like air bags do. In the case of 9/11 flights 11 and 175, the detached units would have had a better chance to survive (both black boxes from both flights were never recovered). That seems like a awful lot of expense when realtime data transmission is cheaper and indestructible by its very nature.

Satellite communications – the next big thing.

And both approaches represent an awful lot of expense when you realize that retrofitting every commercial aircraft with it would only result in the recovery of a few more black boxes. You’ve mentioned two 9/11 flights, and also the present Air France flight. How many other crashes have their been in which the black box was not recovered/recoverable?

Found the answer: 12 crashes in 46 years.

The NOVA show probably guessed right in regards to the accident. If everything died all at once the pilots probably would have reacted in time but the cascade of events meant that the computer made decisions that were not visually evident and the cockpit situation got too busy to figure it out in time.

the only solution can see would be to add an impact deploying satellite beacon that floats. It would be similar to the Canadian emergency beacon required on small planes but deploys on impact.

The 9-11 is irrelvant for black box survival. The collision of a plane with a building consisting of concrete floors and steel lattice pretty much guarentees that everything is shredded like wheat. Tossing the box out at the point of impact would not have made a difference, because it was travling at the same speed as the aircraft and only serve as another object to hit the WTC. Maybe your thinking of ejection charges, but then the question is which way? Not straight out the back; no pilot or passanger is going to tolerate a missile pointed at them while the plane is taxiing down the runway. I might see some projectile being ejected at a vertical 45 degree angle towards the rear of the aircraft, but even such a device had worked, my guess is the black box momentum would have caused it blast into the WTC itself, or hit the building, tumble down to the ground below and then destroyed by the debris from the building collapse. It’s possible they survived, (I know of an old radar CRT that survived a plane crash, whereas four people did not), but until somebody can provide that information, I presume for now, the black boxes did not survive.

With the availibilty of broadband on aircraft, you could conceivably provide real-time information during the flight. I know that IMARSAT offers a broadband service of around 400+kbitsec for IP for their higher gain antennas (lower for wimpy antennas) (forget about polar regions though, the antenna footprint is only specified to 75° North and South). But the question is how much bandwidth do need to send said information? I presume not much since the flight recorders are relatively limited in their memory specs, and they operate on a loop. I would guess the cost verses benefit would justify it for transoceanic flights (because of the difficulty of search and retrieval after an accident, terrorist, etc.), but I doubt it would be worth it for terra firma flights. I’m not aware of any large commercial flights that have ever disappeared over land without a trace (Well, there was the mysterious case of American Pride Flight 29)