The 'black box' was found a couple days ago. What is taking so long to analyze? The voice recording part is fastest, as we have seen from info leaks. But there are lots of other things these boxes record:
FDR (Flight Data Recorder) recorded the following parameters until 1960:
» pressure altitude
» indicated airspeed
» magnetic heading
» normal acceleration
» microphone keying.
Usually FDR is combined with CVR (Cockpit Voice Recorder), latter of which records pilot voice, any sound in the cockpit that can be heard, including engines or what sound gets in from outside.
After around 1960 it became a lot more complex:
..modern jet aircraft far exceed this, and are fitted with FDRs that can record thousands of parameters covering all aspects of the aircraft operation.
The FDR retains the last 25 hours of aircraft operation and, like the CVR, operates on the endless-loop principle. As FDRs have a longer recording duration than CVRs, they are very useful for investigating incidents and accidents.
The signals recorded can be anything from control surface positions to auto-pilot mode and from switch positions to smoke alarms. So FDRs will usually record anything that pilots have control over (rudders, flaps) - that can be turned, switched, operated, etc.. - from the cockpit as well as other parts of the plane and outside measurements too.
I found this list of Aircraft Condition Monitoring System codes most satisfying:
Pilots on this forum are trying to find out what abbreviated readouts their airplanes produce, when they are able to get those printed or recorded. Look at the "machine code" abbreviations Airbus (ACMS) uses for example to dump data: (highly interesting!)
http://www.pprune.org/tech-log/189295-airbus-acms-alpha-codes.html
BLACK BOX DATA TYPES AND HOW THEY ARE USUALLY VISUALIZED:
How is the data recorded?
1. The parameters are recorded as raw binary data (1s and 0s)
2. The format used is ARINC standard (Aeronautical Radio, Incorporated)
3. Parameters to be recorded are determined by the
DFDAU , NOT the recorder! = Digital Flight Data Acquisition Unit, the processor on an aircraft that feeds data to the black box flight data recorder.
What airplane working parts does a black box record?
Before impact:
Flight
Data
Recorder explanation with pictures:
http://www.aerospaceweb.org/question/investigations/q0302.shtml
Black box data can be read / displayed as "excel table" too:
Check out the headers!
Mag heading = magnetic heading
_https://en.wikipedia.org/wiki/Course_(navigation)
For us this could be the most interesting and easiest to read black box recording data type:
How hard it is to recover from a damaged recorder?
We 'computer technicians' know that when the data recorder in a computer is damaged its a very costly and lengthy operation to
professionally recover data in a lab. Worst case scenario is your disk is sent to a laboratory, where your data is recovered and will cost you approximately 4 times the price of your entire computer: Add engineer man-hours and lab hours and any material costs for recovery.
Damage types:
FDR can withstand heat (1100°C) and crash (3,400 g) shock, but damage - burn-, water-, oil-, shock-, crush-, etc.. - can be partial, making the data recovery process last longer and possibly resulting in entirely missing or fragmentary damaged flight data. Hopefully the TU-154 FDR tape was not damaged 'at the exact spot', where it recorded the crash.
We know that Russians love exceptionally well built, hardy old stuff that "works for thousand years" and "can withstand an apocalypse", so tapes are possible in case of the TU-154.
Are black boxes always in pristine condition?
Another interesting point to consider:
(Dave Robinson, 25+ year career as an Aeronautical Industry Professional)
I can however point out that like all other aircraft systems, the CVR and FDR units and their associated connections require regular inspections and periodic maintenance.
It is however not extremely unusual to find the older style (magnetic tape storage) units in a non-functional (broken tape) state when removed for maintenance or to be replaced by a more modern digital (integrated circuit) type storage unit.
Thus depending on the length of inspection and maintenance cycles, older malfunctioning units can go undetected for a number of flights, depending on what type of cockpit indication there is regarding the status of the CVR and the FDR (may only be a light indicating power is being supplied to the recorders but no indication as to whether they are indeed recording).
Intermittent power supplied due to corroded connectors or wiring can also lead to recording dropouts and indications in the cockpit can go unnoticed if such are provided in the first place.
Unfortunately because these units are quite expensive, some airlines and commercial operators resort to purchasing and installing second hand units (removed from decommissioned aircraft) sold through the aftermarket supply chain. Although such units will have been inspected and given a certificate of airworthiness and a certificate of conformance and compliance, their reliability naturally diminishes with age and thus the MTBUR (mean time between unscheduled replacement) is likely less than that originally specified by the manufacturer because the older the unit, the more likely it has been exposed to conditions beyond the scope of those taken into account by the manufacturer when originally determining its useful life.
The above answer does not address the specific case you are thinking of. It only serves to indicate that CVRs and FDRs do indeed fail and such failures can go undetected for some time and it has happened on more that one occasion whereby the prior failure was only detected in the aftermath of an accident, much to the disappointment of the accident investigators.
_https://www.quora.com/Why-would-a-cockpit-voice-recorder-not-record-the-last-dialogue-before-a-crash#
