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-   -   Automation vs Seat-of-the-pants-flying talking as devil's advocate - so no abuse plea (https://www.pprune.org/tech-log/519746-automation-vs-seat-pants-flying-talking-devils-advocate-so-no-abuse-plea.html)

DozyWannabe 18th Sep 2013 00:16


Originally Posted by Centaurus (Post 8049071)
If I recall, a Lion Air Indonesia B737 went into a gradual spiral at night with devastating consequences. Seems the crew were having difficulties with one of the to IRS. in fact there were many reported snags on that IRS previously.

Hi Centaurus,

I can't find a Lion Air incident matching that profile - are you sure you're not thinking of Adam Air 574?

Admittedly it wasn't at night, but the weather was pretty rotten. The Captain was experienced, but new to the airline. They had INS issues as you say, exacerbated by the fact that the aircraft tended to roll to the right when AP was disengaged. They attempted to reset the two INS units without realising that this should be done on the ground, or at the very least with wings held level (as a last resort only). The INS therefore reset itself with a significant tendency to roll right and the rest is history.

The issue was in part incorrect problem-solving on the part of the crew, but underlying that was a significant can of worms regarding company maintenance. One of the leading theories was that the airframe itself was damaged, leading to a tendency to roll to the right, but as soon as AP was engaged, the automation compensated. The Captain noticed this when AP disconnected, hence his desire to re-engage in order to troubleshoot. He incorrectly assumed that the right roll tendency was a fault within the automation, and I have to wonder how many other pilots would have done the same?

Centaurus 18th Sep 2013 13:09


I can't find a Lion Air incident matching that profile - are you sure you're not thinking of Adam Air 574?
Apologies. You are quite right. I meant Adam Air.:ugh:

syseng68k 18th Sep 2013 13:19

You could argue that allowing the ins to be reset when the a/c was not on the
ground was a system design failure. Even if you could reset with wings level
in flight, all you have then is an attitude and perhaps vector reference and
not an ins.

Some of this kit is just bad by design, but that issue was discussed at length
in the AF447 thread with no concensus, fwir :-)...

DozyWannabe 18th Sep 2013 13:30


Originally Posted by syseng68k (Post 8054224)
You could argue that allowing the ins to be reset when the a/c was not on the ground was a system design failure. Even if you could reset with wings level in flight, all you have then is an attitude and perhaps vector reference and not an ins.

Well, that particular aircraft was a 737 Classic, so implementing and retrofitting that kind of lockout would be a significant headache. I can't believe that the restriction on resetting wasn't mentioned in the manual, to be honest!


Some of this kit is just bad by design, but that issue was discussed at length in the AF447 thread with no concensus, fwir :-)...
I wouldn't go so far as to say it was "bad" - as long as it's used correctly, which means thorough training - and maintained correctly, which this aircraft was not. There's a reason Adam Air's operations certificate was withdrawn not too long afterwards.

Of course, AF447 was an Airbus - which tends to bring a whole lot of extra unnecessary baggage to the conversation...


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