D Bru
2025-06-28T17:04:00
permalink Post: 11912578

Quote:

Originally Posted by Someone Somewhere

I am not certain on that. Remember the 737 didn't have them on the standby bus (Jeju). The NTSB doc states they're powered from the L/R 28VDC buses on the 787.

This shows the centre TRUs can only power the instrument buses not the L/R DC buses, the RAT can't really power the right TRU without powering both R1/R2 buses, and powering the left TRU would require powering the left 235/115 ATU which would probably be a lot of magnetising current even if not much actual load. The contactor naming supports that.

My money is on the L/R DC buses being unpowered in RAT operation; only the CA/FO instrument buses and the 235VAC backup bus.

That's exactly why I would really recommend reading through the NTSB FDR report on the 2013 JA829J Boston incident helpfully posted by EDLB . There's potentially a wealth of data concerning a to me at least surprisingly number of 2000 of parameters written on a 787 EAFR, that is that at least if there's elec power. Even the 10 min RIPS is useless if there's no data sent from electrically shut off systems.

Last edited by D Bru; 28th Jun 2025 at 17:06 . Reason: deleting a repeat image of the elec system

5 users liked this post.

AAKEE
2025-06-28T18:19:00
permalink Post: 11912613

Not useless

Quote:

Originally Posted by D Bru

Even the 10 min RIPS is useless if there's no data sent from electrically shut off systems.

As there of corse will not be any data from shutoff systems, there still will be from systems not shut down. Basic flight parameters, I guess.
much netter than\x85nothing. Thats most certainly the background to the new regulations to battery backup.

EXDAC
2025-06-28T18:53:00
permalink Post: 11912625

Quote:

Originally Posted by AAKEE

The requirements I have seen indicate that RIPS is applicable only to CVR or the CVR function of an EAFD. If you are aware of any requirement for RIPS to support flight data recording would you please provide a reference.

FAA requirements and the discussion/changes that resulted from the initial NPRM here -

https://www.federalregister.gov/docu...er-regulations

1 user liked this post.

PJ2
2025-06-28T19:12:00
permalink Post: 11912634

Quote:

Originally Posted by D Bru

Link to the NTSB Report to which D Bru refers, (@EDLB goes to member’s profile):
Auxiliary Power Unit Battery Fire Japan Airlines Boeing 787-8, JA829J Boston, Massachusetts January 7, 2013

2 users liked this post.

nnc0
2025-06-29T15:01:00
permalink Post: 11913074

Quote:

Originally Posted by EXDAC

By the time you're down to EMER GEN you usually know what the problem is and most systems with parameters that could be recorded on the FDR are unpowered so what's the point of trying. The CVR with a RIPS at least helps us to try understand how or why the events to regain control after that failed.

EDLB
2025-06-30T06:50:00
permalink Post: 11913386

Yes positively. In the doc I posted above page 16
https://data.ntsb.gov/Docket/Documen...man-Master.PDF

Eng1_Fuel_cutoff
Eng2_Fuel_cutoff

You get a good impression about the overwhelming wealth of parameters.

3 users liked this post.

island_airphoto
2025-06-30T13:12:00
permalink Post: 11913614

Quote:

Originally Posted by Lonewolf_50

Then why didn't that happen on the previous flight from Deli to Ahmedabad, or any of the previous flights since that install in March?

Thanks for the update, and in particular that bolded bit.

If rigorously applied, an "engine thrust balancer" would cause the good engine to fail if something happened to the other one. Surely there is some logic in there somewhere to give up and disconnect past a certain amount of adjustment??
* as for why not before, probably because it didn't happen that way or in Boeing's worst nightmare some weird corner case in the software that does this if certain parameters are in rare combination.

Lonewolf_50
2025-06-30T13:20:00
permalink Post: 11913619

Quote:

Originally Posted by island_airphoto

Thank you for that answer, edge cases do abound in complex systems, but would not moving the throttles forward by hand (as the thrust was beginning to reduce {for that strange reason}) overcome that and restore thrust?
(As I don't fly the 787, I may be missing something basic on how the systems work).

NSEU
2025-06-30T13:35:00
permalink Post: 11913630

Quote:

Originally Posted by island_airphoto

The FCOM explains that the system only operates when there is a large thrust to weight ratio and will maintain the required climb performance. If applied during an engine out, it will provide directional control only when airspeed drops below normal operating speeds.

1 user liked this post.

Innaflap
2025-06-30T14:42:00
permalink Post: 11913673

Quote:

Originally Posted by EXDAC

I am not aware of any requirement for a DFDAU (or equivalent) to store any data. I say "or equivalent" because in B717 the DFDAU is not an LRU. It is a functional partition of the VIA.

It's not clear to me that 787 EAFR even requires an external DFDAU. The GE EAFR does not -

"Provides Flight Data Acquisition function of ARINC 664 p7 data parameters \x96 No need for a Digital Flight Data Acquisition Unit (DFDAU)."

ref https://www.geaerospace.com/sites/de...rder-3254F.pdf

In this case, there is still an AU - it's just integrated into the EAFR.

D Bru 2025-06-28T17:04:00 permalink Post: 11912578	Quote: Originally Posted by Someone Somewhere I am not certain on that. Remember the 737 didn't have them on the standby bus (Jeju). The NTSB doc states they're powered from the L/R 28VDC buses on the 787. This shows the centre TRUs can only power the instrument buses not the L/R DC buses, the RAT can't really power the right TRU without powering both R1/R2 buses, and powering the left TRU would require powering the left 235/115 ATU which would probably be a lot of magnetising current even if not much actual load. The contactor naming supports that. My money is on the L/R DC buses being unpowered in RAT operation; only the CA/FO instrument buses and the 235VAC backup bus. That's exactly why I would really recommend reading through the NTSB FDR report on the 2013 JA829J Boston incident helpfully posted by EDLB . There's potentially a wealth of data concerning a to me at least surprisingly number of 2000 of parameters written on a 787 EAFR, that is that at least if there's elec power. Even the 10 min RIPS is useless if there's no data sent from electrically shut off systems. Last edited by D Bru; 28th Jun 2025 at 17:06 . Reason: deleting a repeat image of the elec system 5 users liked this post.
AAKEE 2025-06-28T18:19:00 permalink Post: 11912613	Not useless Quote: Originally Posted by D Bru Even the 10 min RIPS is useless if there's no data sent from electrically shut off systems. As there of corse will not be any data from shutoff systems, there still will be from systems not shut down. Basic flight parameters, I guess. much netter than\x85nothing. Thats most certainly the background to the new regulations to battery backup.
EXDAC 2025-06-28T18:53:00 permalink Post: 11912625	Quote: Originally Posted by AAKEE As there of corse will not be any data from shutoff systems, there still will be from systems not shut down. Basic flight parameters, I guess. much netter than\x85nothing. Thats most certainly the background to the new regulations to battery backup. The requirements I have seen indicate that RIPS is applicable only to CVR or the CVR function of an EAFD. If you are aware of any requirement for RIPS to support flight data recording would you please provide a reference. FAA requirements and the discussion/changes that resulted from the initial NPRM here - https://www.federalregister.gov/docu...er-regulations 1 user liked this post.
PJ2 2025-06-28T19:12:00 permalink Post: 11912634	Quote: Originally Posted by D Bru That's exactly why I would really recommend reading through the NTSB FDR report on the 2013 JA829J Boston incident helpfully posted by EDLB . There's potentially a wealth of data concerning a to me at least surprisingly number of 2000 of parameters written on a 787 EAFR, that is that at least if there's elec power. Even the 10 min RIPS is useless if there's no data sent from electrically shut off systems. Link to the NTSB Report to which D Bru refers, (@EDLB goes to member’s profile): Auxiliary Power Unit Battery Fire Japan Airlines Boeing 787-8, JA829J Boston, Massachusetts January 7, 2013 2 users liked this post.
nnc0 2025-06-29T15:01:00 permalink Post: 11913074	Quote: Originally Posted by EXDAC The requirements I have seen indicate that RIPS is applicable only to CVR or the CVR function of an EAFD. If you are aware of any requirement for RIPS to support flight data recording would you please provide a reference. By the time you're down to EMER GEN you usually know what the problem is and most systems with parameters that could be recorded on the FDR are unpowered so what's the point of trying. The CVR with a RIPS at least helps us to try understand how or why the events to regain control after that failed.
EDLB 2025-06-30T06:50:00 permalink Post: 11913386	Yes positively. In the doc I posted above page 16 https://data.ntsb.gov/Docket/Documen...man-Master.PDF Eng1_Fuel_cutoff Eng2_Fuel_cutoff You get a good impression about the overwhelming wealth of parameters. 3 users liked this post.
island_airphoto 2025-06-30T13:12:00 permalink Post: 11913614	Quote: Originally Posted by Lonewolf_50 Then why didn't that happen on the previous flight from Deli to Ahmedabad, or any of the previous flights since that install in March? Thanks for the update, and in particular that bolded bit. If rigorously applied, an "engine thrust balancer" would cause the good engine to fail if something happened to the other one. Surely there is some logic in there somewhere to give up and disconnect past a certain amount of adjustment?? * as for why not before, probably because it didn't happen that way or in Boeing's worst nightmare some weird corner case in the software that does this if certain parameters are in rare combination.
Lonewolf_50 2025-06-30T13:20:00 permalink Post: 11913619	Quote: Originally Posted by island_airphoto If rigorously applied, an "engine thrust balancer" would cause the good engine to fail if something happened to the other one. Surely there is some logic in there somewhere to give up and disconnect past a certain amount of adjustment?? * as for why not before, probably because it didn't happen that way or in Boeing's worst nightmare some weird corner case in the software that does this if certain parameters are in rare combination. Thank you for that answer, edge cases do abound in complex systems, but would not moving the throttles forward by hand (as the thrust was beginning to reduce {for that strange reason}) overcome that and restore thrust? (As I don't fly the 787, I may be missing something basic on how the systems work).
NSEU 2025-06-30T13:35:00 permalink Post: 11913630	Quote: Originally Posted by island_airphoto If rigorously applied, an "engine thrust balancer" would cause the good engine to fail if something happened to the other one. Surely there is some logic in there somewhere to give up and disconnect past a certain amount of adjustment?? * as for why not before, probably because it didn't happen that way or in Boeing's worst nightmare some weird corner case in the software that does this if certain parameters are in rare combination. The FCOM explains that the system only operates when there is a large thrust to weight ratio and will maintain the required climb performance. If applied during an engine out, it will provide directional control only when airspeed drops below normal operating speeds. 1 user liked this post.
Innaflap 2025-06-30T14:42:00 permalink Post: 11913673	Quote: Originally Posted by EXDAC I am not aware of any requirement for a DFDAU (or equivalent) to store any data. I say "or equivalent" because in B717 the DFDAU is not an LRU. It is a functional partition of the VIA. It's not clear to me that 787 EAFR even requires an external DFDAU. The GE EAFR does not - "Provides Flight Data Acquisition function of ARINC 664 p7 data parameters \x96 No need for a Digital Flight Data Acquisition Unit (DFDAU)." ref https://www.geaerospace.com/sites/de...rder-3254F.pdf In this case, there is still an AU - it's just integrated into the EAFR.

Posts about: "Parameters" [Posts: 50 Pages: 3]