The black boxes from Air india disaster.

[wiggydiggy]

Are you saying that the switches, which have to be lifted against spring pressure before they can be repositioned over a metal detent as a safety measure against accidental operation, turned themselves off in sequence?

I'm keeping an open mind for now that the switches could have turned themselves.

That's what I said.

 

[Bonefish Blues]

That's what I said.

You believe '...that the switches could have turned themselves'

OK thanks.

 

[DaveReading]

That's what I said.

Yes, that's all anyone can really say at the moment.

Every pilot of a Boeing 737/747/757/767/787 pulls those switches up at the end of every flight and moves them to the Cutoff position to shut down the engines.

The Service Bulletin advising of the existence of defective switches that could simply be flicked between Run and Cutoff without being lifted through the gate was advisory only, and Air India was one of the airlines that chose not to do the checks on its aircraft (nor, presumably, on any of the spare throttle control modules in its stores).

 

[markemark]

Yes, that's all anyone can really say at the moment.

Every pilot of a Boeing 737/747/757/767/787 pulls those switches up at the end of every flight and moves them to the Cutoff position to shut down the engines.

The Service Bulletin advising of the existence of defective switches that could simply be flicked between Run and Cutoff without being lifted through the gate was advisory only, and Air India was one of the airlines that chose not to do the checks on its aircraft (nor, presumably, on any of the spare throttle control modules in its stores).

Or maybe the locking mechanism wore over time if constantly used?

 

[Mike_P]

You believe '...that the switches could have turned themselves'

OK thanks.

Its happened before re 737s which use the same - a pilot interviewed on 5 Live this morning 1:09:40 in this https://www.bbc.co.uk/sounds/play/m002ft09

 

[Bonefish Blues]

Its happened before re 737s which use the same - a pilot interviewed on 5 Live this morning 1:09:40 in this https://www.bbc.co.uk/sounds/play/m002ft09

What time in the programme please?

 

[DaveReading]

Or maybe the locking mechanism wore over time if constantly used?

Maybe, but the issue highlighted in the SB concerned faulty installation, rather than wear.

 

[PhotoNic69]

Good grief! Complete anal speculum speculation! Nobody will know until the investigation is complete and then we probably won't know the full facts anyway! I don't think it's helpful to make assumptions at this stage.
After all, if the ghost of Maradona was on board it could have been the 'hand of god'

 

[DaveReading]

Speculation is human nature.

 

[Mike_P]

What time in the programme please?

1:09:40 as I posted

 

[Bonefish Blues]

1:09:40 as I posted

Thanks, I didn't notice the time.

I just listened to that. The pilot did not say that the switches moved themselves. He says that he noticed that his 737 fuel switch locking mechanism wasn't operational as they were taxiing so they returned to the jetty to get it fixed. That was the issue that was the subject of the notice to operators in 2018.

 

[DaveReading]

I just listened to that. The pilot did not say that the switches moved themselves. He says that he noticed that his 737 fuel switch locking mechanism wasn't operational as they were taxiing so they returned to the jetty to get it fixed. That was the issue that was the subject of the notice to operators in 2018.

In normal operations the switches are only operated twice during a flight - on engine startup and shutdown.

I can't see any situation where a switch fault would become apparent when taxying to the runway for takeoff, other than inadvertent/uncommanded movement and resulting engine shutdown (a scenario foreseen in the SB).

This happened on a 747, by the way, not a 737 - though the same considerations apply.

 

[Bonefish Blues]

Here's the extract from the Special Airworthiness Information Bulletin in 2018:

The FAA recommends that all owners and operators of the affected airplanes incorporate the
following actions at the earliest opportunity:
1) Inspect the locking feature of the fuel control switch to ensure its engagement. While the
airplane is on the ground, check whether the fuel control switch can be moved between the
two positions without lifting up the switch. If the switch can be moved without lifting it up,
the locking feature has been disengaged and the switch should be replaced at the earliest
opportunity.

That was the check.

It would be hard for any pilot to miss a defective switch for very long, but as said, it could not be checked whilst taxiing so the captain's account doesn't make sense as he told it.

 

[Illaveago]

Speculation is human nature.

It gives us something to talk about.

 

[Illaveago]

Here's the extract from the Special Airworthiness Information Bulletin in 2018:

The FAA recommends that all owners and operators of the affected airplanes incorporate the
following actions at the earliest opportunity:
1) Inspect the locking feature of the fuel control switch to ensure its engagement. While the
airplane is on the ground, check whether the fuel control switch can be moved between the
two positions without lifting up the switch. If the switch can be moved without lifting it up,
the locking feature has been disengaged and the switch should be replaced at the earliest
opportunity.

That was the check.

It would be hard for any pilot to miss a defective switch for very long, but as said, it could not be checked whilst taxiing so the captain's account doesn't make sense as he told it.

If the locking mechanism was faulty then there was nothing to prevent the switches from being turned which could happen during taxying.