EAFR Page: 9 of 9

nikplane
February 01, 2026, 19:49:00 GMT
permalink Post: 12030813

Technical aspects

Hello everyone.
There's this rumor and/or question going around:
Someone was promoting the idea that a diode failure in the backup battery had disabled the battery and both buses.
He claimed that the FDR inputs from the switch sensors were coming from opto-isolators, and since they had lost power, they showed the switches going into the open state until power returned from the RAT.
For this theory to be valid, a single diode failure would have had to disable the entire aircraft.

Please,
- just comments on technical aspects?
- It's unclear this refers to the forward EAFR backup battery or
the Hot Battery Bus (Hot BB).

Thanks

Last edited by nikplane; 1st February 2026 at 20:04 .

Subjects EAFR FDR RAT (All)

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MechEngr
February 01, 2026, 22:10:00 GMT
permalink Post: 12030848

Quote:

Originally Posted by nikplane

One would need a detailed electrical schematic to determine what the function of the diode was. Absent the electrical schematic it's an idea that is not worth consideration.

Subjects EAFR FDR RAT (All)

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Musician
February 01, 2026, 22:18:00 GMT
permalink Post: 12030849

Quote:

Originally Posted by nikplane

The engines have their own power supply, separate connections to the cutoff switches and thrust lever angle resolvers, and would be unaffected in this scenario.

Notwithstanding the fact that this failure mode is also technically implausible/impossible. Here's a 787 that landed with the battery on fire:
https://skybrary.aero/accidents-and-...and-japan-2013

On 16 January 2013, a Boeing 787-8 (JA804A) being operated by All Nippon Airways (ANA) on a scheduled passenger flight from Yamaguchi-Ube to Tokyo Haneda in day Visual Meteorological Conditions (VMC) made an emergency diversion to Takamatsu after a main battery failure was annunciated climbing through FL320.

.
The original perpetrator of this idea is Jeremy John Thompson, with a Youtube video titled "How Air India AI171 B787 crashed - Lithium Battery Diode Module Failure" positing that the battery diode module failed, the battery overcharged and short-circuited, and disaster ensued. This was half a year ago.

Last edited by Musician; 1st February 2026 at 22:41 .

Subjects AI171 EAFR FDR Fuel (All) Fuel Cutoff Switches RAT (All)

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paulross
February 02, 2026, 12:21:00 GMT
permalink Post: 12031064

Quote:

Originally Posted by nikplane

This post might help clear up your confusion: Preliminary Report Timeline

Subjects EAFR FDR Preliminary Report RAT (All)

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nikplane February 01, 2026, 19:49:00 GMT permalink Post: 12030813	Technical aspects Hello everyone. There's this rumor and/or question going around: Someone was promoting the idea that a diode failure in the backup battery had disabled the battery and both buses. He claimed that the FDR inputs from the switch sensors were coming from opto-isolators, and since they had lost power, they showed the switches going into the open state until power returned from the RAT. For this theory to be valid, a single diode failure would have had to disable the entire aircraft. Please, - just comments on technical aspects? - It's unclear this refers to the forward EAFR backup battery or the Hot Battery Bus (Hot BB). Thanks Last edited by nikplane; 1st February 2026 at 20:04 . Subjects EAFR FDR RAT (All) Links are to this post in the relevant subject page so that this post can be seen in context. No recorded likes for this post (could be before pprune supported 'likes'). Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
MechEngr February 01, 2026, 22:10:00 GMT permalink Post: 12030848	Quote: Originally Posted by nikplane Hello everyone. There's this rumor and/or question going around: Someone was promoting the idea that a diode failure in the backup battery had disabled the battery and both buses. He claimed that the FDR inputs from the switch sensors were coming from opto-isolators, and since they had lost power, they showed the switches going into the open state until power returned from the RAT. For this theory to be valid, a single diode failure would have had to disable the entire aircraft. Please, - just comments on technical aspects? - It's unclear this refers to the forward EAFR backup battery or the Hot Battery Bus (Hot BB). Thanks One would need a detailed electrical schematic to determine what the function of the diode was. Absent the electrical schematic it's an idea that is not worth consideration. Subjects EAFR FDR RAT (All) Links are to this post in the relevant subject page so that this post can be seen in context. No recorded likes for this post (could be before pprune supported 'likes'). Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
Musician February 01, 2026, 22:18:00 GMT permalink Post: 12030849	Quote: Originally Posted by nikplane Hello everyone. There's this rumor and/or question going around: Someone was promoting the idea that a diode failure in the backup battery had disabled the battery and both buses. He claimed that the FDR inputs from the switch sensors were coming from opto-isolators, and since they had lost power, they showed the switches going into the open state until power returned from the RAT. For this theory to be valid, a single diode failure would have had to disable the entire aircraft. Please, - just comments on technical aspects? - It's unclear this refers to the forward EAFR backup battery or the Hot Battery Bus (Hot BB). Thanks The engines have their own power supply, separate connections to the cutoff switches and thrust lever angle resolvers, and would be unaffected in this scenario. Notwithstanding the fact that this failure mode is also technically implausible/impossible. Here's a 787 that landed with the battery on fire: https://skybrary.aero/accidents-and-...and-japan-2013 On 16 January 2013, a Boeing 787-8 (JA804A) being operated by All Nippon Airways (ANA) on a scheduled passenger flight from Yamaguchi-Ube to Tokyo Haneda in day Visual Meteorological Conditions (VMC) made an emergency diversion to Takamatsu after a main battery failure was annunciated climbing through FL320. . The original perpetrator of this idea is Jeremy John Thompson, with a Youtube video titled "How Air India AI171 B787 crashed - Lithium Battery Diode Module Failure" positing that the battery diode module failed, the battery overcharged and short-circuited, and disaster ensued. This was half a year ago. Last edited by Musician; 1st February 2026 at 22:41 . Subjects AI171 EAFR FDR Fuel (All) Fuel Cutoff Switches RAT (All) Links are to this post in the relevant subject page so that this post can be seen in context. 2 recorded likes for this post. Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
paulross February 02, 2026, 12:21:00 GMT permalink Post: 12031064	Quote: Originally Posted by nikplane Hello everyone. There's this rumor and/or question going around: Someone was promoting the idea that a diode failure in the backup battery had disabled the battery and both buses. He claimed that the FDR inputs from the switch sensors were coming from opto-isolators, and since they had lost power, they showed the switches going into the open state until power returned from the RAT. For this theory to be valid, a single diode failure would have had to disable the entire aircraft. Please, - just comments on technical aspects? - It's unclear this refers to the forward EAFR backup battery or the Hot Battery Bus (Hot BB). Thanks This post might help clear up your confusion: Preliminary Report Timeline Subjects EAFR FDR Preliminary Report RAT (All) Links are to this post in the relevant subject page so that this post can be seen in context. No recorded likes for this post (could be before pprune supported 'likes'). Reply to this quoting this original post. You need to be logged in. Not available on closed threads.

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