Power supply for the black boxes
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Join Date: Sep 2002
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Power supply for the black boxes
To the one and only John-tullamarine Q ?
do you know pwr source for the Flt data recorder and the voice data recorder on the 73/800 , and does the voice and data recorder have their own internal clock ? and if so do they update with the master clock at pwr up ?
News media reporting gap of 3 minutes on United 93 black boxes from end of tape to time of impact , knowing the news media I don't give to much credit to the news but you never know , stay tune . In the mean time I may as well learn how my black boxes do work . Thank you in advance John or to any one that will educate me on the subj .
do you know pwr source for the Flt data recorder and the voice data recorder on the 73/800 , and does the voice and data recorder have their own internal clock ? and if so do they update with the master clock at pwr up ?
News media reporting gap of 3 minutes on United 93 black boxes from end of tape to time of impact , knowing the news media I don't give to much credit to the news but you never know , stay tune . In the mean time I may as well learn how my black boxes do work . Thank you in advance John or to any one that will educate me on the subj .
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Afraid I can't help you on this one. While I might profess to have some limited understanding of why bits of tin creak and groan and an aircraft wiggles and waggles I, like most, stand in awe of the black devil art of electronics .....
Presuming that you are flying the -800 at present, might I suggest that you direct the question to your Tech Service department, in particular the electronics/avionics engineers.
Should be a simple set of questions for the guys to dig out some answers from the WDM and unit spec data.
Presuming that you are flying the -800 at present, might I suggest that you direct the question to your Tech Service department, in particular the electronics/avionics engineers.
Should be a simple set of questions for the guys to dig out some answers from the WDM and unit spec data.
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Don't know about your specific aircraft (didn't do the narrow bodies at the Lazy B) but per the FARs, the CVR must be on the most reliable power source (read Battery Bus). The FDR must be on the next most reliable but not the same as the CVR. As some aircraft actually link Battery & Essential Busses together when in extremis, this can mean the DC Bus 1 or AC Bus 1 (your choice).
A good set of guide lines is in EUROCAE ED-55.
The latest FDRs & CVRs take in ship's clock over an ARINC 429 databus. Older CVRs took in an audio signal from the DFDAU called Frequency Shift Keying (FSK). Older CVRs again just used the PTT Discretes on the FDR to synch the recorders. If there's no clock available, the FDR relies on its internal frame count and the CVR is either microprocessor time from on/last time (solid state) or fom its quartz tape drive.
A good set of guide lines is in EUROCAE ED-55.
The latest FDRs & CVRs take in ship's clock over an ARINC 429 databus. Older CVRs took in an audio signal from the DFDAU called Frequency Shift Keying (FSK). Older CVRs again just used the PTT Discretes on the FDR to synch the recorders. If there's no clock available, the FDR relies on its internal frame count and the CVR is either microprocessor time from on/last time (solid state) or fom its quartz tape drive.
Last edited by ICT_SLB; 28th Sep 2002 at 03:45.
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I am afraid I can't help with this particular ADR but in my experience they normally keep turning on the battery bus and record the time of day if nothing else. Once they lose AC power, however, a lot of interesting parameters like engine RPM and roll rate tend to go offline.
