ignorantAndroid
July 14, 2025, 04:15:00 GMT
permalink Post: 11921848

Quote:

Originally Posted by Lonewolf_50

I think we'll need to agree to disagree, since those cameras won't prevent any accident (all they'll do is improve post mortems)

That would apply to FDRs and CVRs as well. The purpose of investigating accidents is to prevent future accidents.

Subjects: None

ignorantAndroid
July 14, 2025, 06:02:00 GMT
permalink Post: 11921875

Looking at some past FDR data, it appears that the fuel cutoff switches are sampled at 1 Hz, but the actual valve position is sampled at 4 Hz. The position of the fire switch (fire handle) is also recorded. N1 and N2 are sampled at 1 Hz.

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): FDR Fuel (All) Fuel Cutoff Fuel Cutoff Switches

ignorantAndroid
July 14, 2025, 20:32:00 GMT
permalink Post: 11922481

Quote:

Originally Posted by tdracer

Again, not familiar with the specifics of the 787, but on the 747-400/-8, one pole of the fuel switch feeds EICAS - which uses it in various message logic - and sends it out to any other aircraft systems that use it. There is "Digital Flight Data Acquisition Unit) DFDAU (pronounced Daff Du) that takes all the various system digital signals, sorts them and provides them to the DFDR and QAR. The 787 has something similar to the DFDAU but I don't recall what it's called.

It was stated earlier that 2 of the poles in the switch are wired to separate Remote Data Concentrators. The RDCs feed data into the Common Data Network (essentially an Ethernet LAN).

The EAFRs simply sniff the required data from the CDN, so there's no DFDAU as such.

For some parameters, including the fuel cutoff switches, the EAFRs also record a "Source Index." For the fuel cutoff switches, there are 4 sources numbered 1 through 4 as well as a valid/invalid flag. I don't know what the sources are, but perhaps they're the 2 RDCs plus the 2 channels of the EEC/FADEC. It appears that source 1 (the default) is not the EEC.

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): DFDR Digital Flight Data Acquisition Unit EICAS Fuel (All) Fuel Cutoff Fuel Cutoff Switches Parameters

ignorantAndroid
July 16, 2025, 05:00:00 GMT
permalink Post: 11923427

Quote:

Originally Posted by Musician

Where is the RadAlt antenna on a 787? Is it in the nose, or further back between the main gears?

Subjects: None

ignorantAndroid
July 17, 2025, 20:08:00 GMT
permalink Post: 11924625

Quote:

Originally Posted by Sailvi767

The displayed EICAS messages are very different when an engine is shut down via the fuel cutoff switch vice other reasons. The EAFR records those messages. I am quite sure they have eliminated the TCMA as a problem in this accident.

Indeed, there are dedicated parameters for TCMA:

Eng1_TCMA_Shutdown_Local_EEC_A
Eng1_TCMA_Shutdown_Local_EEC_B
Eng2_TCMA_Shutdown_Local_EEC_A
Eng2_TCMA_Shutdown_Local_EEC_B

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): EAFR EICAS Fuel (All) Fuel Cutoff Fuel Cutoff Switches Parameters

ignorantAndroid July 14, 2025, 04:15:00 GMT permalink Post: 11921848	Quote: Originally Posted by Lonewolf_50 I think we'll need to agree to disagree, since those cameras won't prevent any accident (all they'll do is improve post mortems) That would apply to FDRs and CVRs as well. The purpose of investigating accidents is to prevent future accidents. Subjects: None
ignorantAndroid July 14, 2025, 06:02:00 GMT permalink Post: 11921875	Looking at some past FDR data, it appears that the fuel cutoff switches are sampled at 1 Hz, but the actual valve position is sampled at 4 Hz. The position of the fire switch (fire handle) is also recorded. N1 and N2 are sampled at 1 Hz. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): FDR Fuel (All) Fuel Cutoff Fuel Cutoff Switches
ignorantAndroid July 14, 2025, 20:32:00 GMT permalink Post: 11922481	Quote: Originally Posted by tdracer Again, not familiar with the specifics of the 787, but on the 747-400/-8, one pole of the fuel switch feeds EICAS - which uses it in various message logic - and sends it out to any other aircraft systems that use it. There is "Digital Flight Data Acquisition Unit) DFDAU (pronounced Daff Du) that takes all the various system digital signals, sorts them and provides them to the DFDR and QAR. The 787 has something similar to the DFDAU but I don't recall what it's called. It was stated earlier that 2 of the poles in the switch are wired to separate Remote Data Concentrators. The RDCs feed data into the Common Data Network (essentially an Ethernet LAN). The EAFRs simply sniff the required data from the CDN, so there's no DFDAU as such. For some parameters, including the fuel cutoff switches, the EAFRs also record a "Source Index." For the fuel cutoff switches, there are 4 sources numbered 1 through 4 as well as a valid/invalid flag. I don't know what the sources are, but perhaps they're the 2 RDCs plus the 2 channels of the EEC/FADEC. It appears that source 1 (the default) is not the EEC. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): DFDR Digital Flight Data Acquisition Unit EICAS Fuel (All) Fuel Cutoff Fuel Cutoff Switches Parameters
ignorantAndroid July 16, 2025, 05:00:00 GMT permalink Post: 11923427	Quote: Originally Posted by Musician Where is the RadAlt antenna on a 787? Is it in the nose, or further back between the main gears? Subjects: None
ignorantAndroid July 17, 2025, 20:08:00 GMT permalink Post: 11924625	Quote: Originally Posted by Sailvi767 The displayed EICAS messages are very different when an engine is shut down via the fuel cutoff switch vice other reasons. The EAFR records those messages. I am quite sure they have eliminated the TCMA as a problem in this accident. Indeed, there are dedicated parameters for TCMA: Eng1_TCMA_Shutdown_Local_EEC_A Eng1_TCMA_Shutdown_Local_EEC_B Eng2_TCMA_Shutdown_Local_EEC_A Eng2_TCMA_Shutdown_Local_EEC_B Subjects (links are to this post in the relevant subject page so that this post can be seen in context): EAFR EICAS Fuel (All) Fuel Cutoff Fuel Cutoff Switches Parameters

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