When are black boxes used?

• Recording
• Reading
  • Accident investigation
  • Operational testing
    • Annual
    • Daily
  • Other purposes

Used for recording data

The FDR and CVR are obviously in-use, for recording data, when the aircraft is being used to transport passengers or cargo.

Used for reading data

In the event of an accident

As we all know, after an incident, the recorders are used by the investigators to retrieve the data that has been recorded prior to and during the incident.

For operational testing

There is no point having a recorder installed if it is not working. This means that the recorder must be used for operational tests.

###Annual checks

The regulatory bodies have varying rules for testing of recorders.

Here is an extract from ICAO regulations

6.10.10 Flight recorders — continued serviceability Operational checks and evaluations of recordings from the flight data and cockpit voice recorder systems shall be conducted to ensure the continued serviceability of the recorders.

Attachment D - 3.2 : Annual inspections should be carried out as follows: a) the read-out of the recorded data from the FDR and CVR should ensure that the recorder operates correctly for the nominal duration of the recording;

b) the analysis of the FDR should evaluate the quality of the recorded data to determine if the bit error rate is within acceptable limits and to determine the nature and distribution of the errors;

c) a complete flight from the FDR should be examined in engineering units to evaluate the validity of all recorded parameters. Particular attention should be given to
parameters from sensors dedicated to the FDR. Parameters taken from the aircraft’s electrical bus system need not be checked if their serviceability can be detected by other
aircraft systems;

The French investigation body "BEA" state

2.1.5 Information on US regulations

Regulations concerning FDRs in the United States are prescribed in FAR (Federal Aviation Regulations), Part 125 – “Certification and Operations of airplanes which have a seating capacity of 20 or more passengers or a maximum payload capacity of 6,000 pounds or more,” section 125.226. Aircraft operators are required to establish a method of readily retrieving data and to maintain documentation sufficient to convert recorded data into engineering units (in data frame layout documents). However, a single document may be established for any group of aircraft that are of the same type and on which the flight recorder system and its installation are the same.

In addition, the FAA’s HBAW (Handbook Bulletin for Airworthiness) 97-13B of 15 December 1997 provides Principal Avionics Inspectors (PAI) with guidance needed to evaluate FDR maintenance programmes. In particular, PAI’s should check if the data frame layout documents are kept up to date and any modifications/retrofits to DFDR systems are documented and accounted for. Furthermore, it is stated that, “PAI action should include air carrier operator readout of each airplane’s DFDR to determine that all required parameters are being recorded, and to verify that each parameter is working properly.”

###Daily checks

It is easy to find airline checklists that specify that the FDR is to be tested (e.g. Emirates 777 Freighter, p5)

I don't know what form this test takes, perhaps there is some sort of quick self-test capability built into at least some recorders?

Other Purposes

Surely the black box could be used for other purposes?

###Cockpit Voice Recorders

Note that there are regulations preventing other uses of cockpit voice recorders specifically. Federal CVR nondisclosure laws (refer to 49 United States Code (USC) Section 1114(c) – Disclosure, availability, and use of information

###Flight Data Recorders

This is a subject that has been looked at in the past by academics.

FLIGHT DATA PROCESSING - TECHNIQUES TO IDENTIFY UNUSUAL EVENTS begins

Modern aircraft are capable of recording hundreds of parameters during flight. This fact not only facilitates the investigation of an accident or a serious incident, but also provides the opportunity to use the recorded data to predict future aircraft behavior. It is believed that, by analyzing the recorded data, one can identify precursors to hazardous behavior and develop procedures to mitigate the problems before they actually occur.

Instead, I believe airlines, and their partners, use ACARS transmissions, Quick-Access recorders and other methods of collecting data.