Aircraft DFDR

[HH Chan]

Hi all..
Any kind soul can explain..the aircraft Digital Flt Data Recorder (DFDR) as I understand has a recording capacity of around 25hrs.

Question..

1. When does it reset to zero hrs? After each flight? Or it continues until its data has reached 25 hrs and then its resetted automatically?

2. If it resets after 25hrs, past data all gone?

[giggitygiggity]

Whatever you've done, it's probably best to come clean!

As far as I know, it just keeps looping for 25hrs.

[DaveReidUK]

If by "reset" you mean deleting all the data, that's not how they usually work.

A 25-hour FDR will normally store the last 25 hours of flight, across however many sectors occupied that duration.

[HH Chan]

.info for my students.

[tdracer]

DR is correct - that also applies to Voice Recorders (although the storage period is normally shorter).
BTW, 25 hours for the DFDR is the current minimum, many of the new ones go longer. Quick Access Recorders (QAR) can also record for a very long period (although they are not 'crash proof' they are often very valuable for incident investigation since they record stuff not typically on the DFDR).