Why do they continue to use what seems like antiquated technology for airliner black boxes?

Question

Whenever a plane goes down, (or even the space shuttle), there's a big search for the black box. When they find it, they invariably discover the tape with the data has been damaged by heat, sea water, etc. I get the impression they are still using analog tape recorders. It seems to me they could easily have a real-time digital stream of data to the ground. That way, if a plane crashes, they already have all the flight data. Can someone in aviation explain?

Answer 1

One word...MONEY

With the industry on shakey footing since 9/11, they're no going to spend a dime to improve anything. But the "Black Box" no longer employs analog tape. Plus, there are two units:

Flight data recorder
Cockpit voice recorder (although some newer models have combined both into one unit).

Currently, EUROCAE specifies that a recorder must be able to withstand an acceleration of 3400 g (33 km/s²) acceleration for 6.5 milliseconds. This is roughly equivalent to an impact velocity of 270 knots and a deceleration or crushing distance of 450 mm. Additionally, there are requirements for penetration resistance, static crush, high and low temperature fires, deep sea pressure, sea water immersion, and fluid immersion.

Modern day FDRs are typically plugged into the aircraft's fly-by-wire main data bus. They record significant flight parameters, including the control and actuator positions, engine information and time of day. There are 88 parameters required as a minimum by current U.S. federal regulations (only 29 were required until 2002), but some systems monitor many more variables. Generally each parameter is recorded a few times per second, though some units store "bursts" of data at a much faster frequency if the data begins to change quickly. Most FDRs record 25 hours worth of data in a continuous loop.

Early CVRs were analog wire recording (in the 50's) and were later replaced by analog magnetic tape. Some of the tape units used two reels, with the tape automatically reversing at each end. Other units used a single reel, with the tape spliced into a continuous loop, much as in an 8-track cartridge. The tape would circulate and old audio information would be overwritten every 30 minutes. Recovery of sound from magnetic tape often proves difficult if the recorder is recovered from water and its housing has been breached. Thus, the latest designs employ solid-state memory and use digital recording techniques, making them much more resistant to shock, vibration and moisture. With the reduced power requirements of solid-state recorders, it is now practical to incorporate a battery in the units, so that recording can continue until flight termination, even if the aircraft electrical system fails.

Answer 2

The pilots would never go for having all their conversations and control actions constantly available for review. They accept the black boxes because they have no choice, and they know the information can only be used after a crash.

Your idea does have merit though, but every plane would need to be retrofitted, and they'd need receiving stations all over the world. Again, who guarantees that the data is kept confidential?

From a few things I've read, they found that the recording medium they use is actually more durable than something like an electronic memory, and that's why they haven't switched. It's possible that technology will change this in the future, but I can't see them beaming the data to the ground anytime soon.

To the umpteenth person that asked why they don't build the plane out of the same material, just read the link below.

EDIT: I guess I'm out of date on the switch to digital. It's about time.

Answer 3

If data was streamed to the ground would be security issues that would put the plane at risk of anyone picking up data of what was going on with that plane and give terrorist an edge on takeing down planes.
What is an example of the black box being damaged because I was under the impression that they used the black box because it was a proven technology. [e-mail]

Answer 4

Modern Cockpit Voice Recorders (CVR's) and Flight Data Recorders (FDR's) are digital.

It depends on the model, but in the aircraft I fly, the CVR stores 120 minutes of information in a solid-state non-volatile memory. It has an Underwater Locator Device (ULD) which works like sonar. The ULD can transmit for 30 days after activation.

The FDR also records data using a solid-state non-volatile memory. It records the last 25 hours of critical aircraft and flight parameter data. I don't know all the flight parameters recorded, but there are a lot. The FDR also has a ULD.

If a crash occurs, electrical power is automatically removed from the CVR and FDR. This prevents the erasure of stored information.

Answer 5

New and retrofitted black boxes are indeed totally digital. Only a small fraction of those currently in use use analog tape. Not only are the new boxes more survivable, they also track many more 'channels' or instrument inputs, voice or data tracks, etc.

I think your recollection is playing tricks on you. When a plane crashes and the black box works perfectly you don't hear about it. It's only when there is a problem do you hear about it and it sticks with you.

Answer 6

The analog technology is used because it is much more durable. The incredible forces and heat the box is subjected to would never allow for digital data to survive. Digital requires an electronic, optical or magnetic storage device that is much more sensitive to outside forces than the thin piece of wire that is currently used for voice recordings.

Answer 7

I don't know the answer for sure but I think it is the same reason that we are still using antiquated technology for our planes. When I was a kid, they told us that by the year 2000, we'd all be traveling by flying cars, monorails, and teleportation. We're supposed to all own our personal robots. I think they're spending all our research money on bullets and bombs.

Answer 8

i'm not in aviation but my question about the black box is if its so indestructible why dont they make the entire plane out of what ever the black box is made out of