# What is the form of information stored in black box?

Black boxes contain the information regarding to a flight. What is the form of those information? Any particular language log?

There are 2 different black boxes.

1. The cockpit voice recorder. This holds audio from several different sources, including the microphone for each pilot, the radio and a general cockpit microphone.

2. The flight data recorder holds at least 88 different parameters including attitude of the craft, engine performance, autopilot setting, pilot input one the controls, etc.

• this answer the question of what data, but the question is rather about how is stored. I wonder why it got accepted, does the OP know what he's asking? – Federico Jan 29 '15 at 13:18
• @Federico judging from his other questions I guess not. – ratchet freak Jan 29 '15 at 13:20

Although I have no specific information on this I do work around electronics/computer for a living so if I had to guess...

The older units most likely ran on slow speed audio tapes of some sort, the quality is not great but you can get a lot of time on a single tape. I don't know how the old ones stored flight data or if they even did but tape format would be an option for that as well.

Modern ones most likely store data in solid state chips or on a platter style hard drive. I would think solid state non volatile memory is used (think SD memory card) as its far less susceptible to shock damage than a platter style hard drive. Since these devices most likely use components made for generic purposes the audio could be encoded at any variety of resolutions but is most likely 44.1Khz/16bit or something like that simply because thats what many A/D converters run at.

The flight data may have some custom data format but is stored in some normalized way like any data set on any computer. Maybe JSON, maybe XLM who knows, but things like GPS data have standard string representations that I would think are used. I would think they use some kind of sequential writing on the memory chip so that if something goes wrong mid memory write they can extract based on specific memory locations. Basically if you know that every write of data takes 1000 bytes and you started writing at address 0 you can grab the data from any point in time by directly addressing the memory location.

At least thats how I would design a black box...

• I think it is extremely unlikely that JSON, XML or standard GPS (NMEA) is used. These formats are extremely inefficient for storage. Instead a binary format is used. – DeltaLima Feb 4 '15 at 20:26
• You are correct that older units mostly used tape, and modern units use SSD's (I don't think they ever used hard drives, as the 1000g requirement would be rather difficult). I agree with DeltaLima that using anything other than a binary data format would be surprising. – raptortech97 Feb 4 '15 at 21:45
• @Dave, keep in mind that its simply a big ring buffer where entries are written either periodically or as the data come over the various busses (ARINC 429, the most common data bus in avionics, is one-way, so each sensor has separate wire going from it). The easiest way to implement a ring buffer is with fixed size records. Most likely either exactly as they came or just simply decoded to binary integers or floats. – Jan Hudec Nov 15 '16 at 20:12
• @Dave, keep in mind that this is a microcontroller. Your typical JSON or XML library wouldn't even fit in it! Also, being safety-critical device, all code on it must be validated and writing validation tests for a JSON or XML library would just be a lot of extra work that is completely unnecessary when all it needs to do is dump the received message at the next address and increment the address counter! – Jan Hudec Nov 15 '16 at 20:15
• I think you would be hard pressed to find a Flight Data Recorder that didn't store all of it's data in binary form, packed as densely as possible or in a fixed byte width. I also wouldn't be surprised if it used redundant micros that wrote the same data to two different data storage banks. – selectstriker2 Nov 16 '16 at 1:39