AAIB special bulletin ~ Loganair
de minimus non curat lex
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AAIB special bulletin ~ Loganair
Special Bulletin S1/2015 Saab 2000, G-LGNO
Well worth a read.
Well worth a read.
Last edited by parkfell; 2nd Mar 2015 at 16:48. Reason: Syntax
Very simple system...no THS or elevator trim tabs. The control column always tells you where the elevator is.
Originally Posted by Report page 4 at the top
Pitch trim consists of elevator movement without associated control column movement.
I have been told by an industry insider that CVRs on CAT were randomly selected for playback as part of a HP study.
One of the most frequent recording heard was " what's it doing now?".
Increased automation has significant benefits but the system limitations must be fully understood by the crew.
One of the most frequent recording heard was " what's it doing now?".
Increased automation has significant benefits but the system limitations must be fully understood by the crew.
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Scary biscuits. I wonder if it was a factor that the captain only had 143 hours on type and looks like he'd only been flying it for about four months?
Spot of remedial training to tick the box but neither of them will ever make that mistake again.
Yup! Heard that a few times on them new-fangled hairyplanes.
" what's it doing now?".
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Reading the report it seems more basic in that the pilot may have expected his control column inputs to disconnect the autopilot as per more sophisticated APs.
It was implied in the report that how to disconnect the autopilot may not have been fully known by some pilots/operators. Remedial actions included the operator revise their SOP to explicitly state AP disconnect methods and to incorporate it into their Type Conversion and Recurrent training.
It's interesting though, how would most pilots instinctively expect an AP to function when say, after having converting from a type with a more sophisticated AP to a less sophisticated AP or vice-versa?
Further, the design sounds a bit contrary.....it has sophisticated FBW, no mechanical trim-tab elevator control system but mated to an AP with only basic logic/functionality that ignores most of the flight control inputs the pilot is making?
It was implied in the report that how to disconnect the autopilot may not have been fully known by some pilots/operators. Remedial actions included the operator revise their SOP to explicitly state AP disconnect methods and to incorporate it into their Type Conversion and Recurrent training.
It's interesting though, how would most pilots instinctively expect an AP to function when say, after having converting from a type with a more sophisticated AP to a less sophisticated AP or vice-versa?
Further, the design sounds a bit contrary.....it has sophisticated FBW, no mechanical trim-tab elevator control system but mated to an AP with only basic logic/functionality that ignores most of the flight control inputs the pilot is making?
Nock187, Yes, doesn't matter what the book says, I'd still press the disconnect button.
I guess we should remember they'd just had a lightning strike which I recollect as VERY loud (and Bas is ex artillery) which could have caused a little disorientation leading ol' skip to think he'd already pressed the disconnect.
Not excusing, merely looking for reasons - there's always a reason.
I guess we should remember they'd just had a lightning strike which I recollect as VERY loud (and Bas is ex artillery) which could have caused a little disorientation leading ol' skip to think he'd already pressed the disconnect.
Not excusing, merely looking for reasons - there's always a reason.
de minimus non curat lex
Thread Starter
Saab 340B Icing with AP involvement
This Saab 340B AAIB report was published in September 2006. (09/2006)
Icing conditions with the AP engaged. Again some initial confusion as to what was happening. An experienced Captain, with an FO who was previously a licensed engineer on type. Probably helped the situation?
As part of the AAIB involvement, an Inspector spent a day on the Saab jumpseat. He was then flying a fews days a month with Flybe on the Q400.
Icing conditions with the AP engaged. Again some initial confusion as to what was happening. An experienced Captain, with an FO who was previously a licensed engineer on type. Probably helped the situation?
As part of the AAIB involvement, an Inspector spent a day on the Saab jumpseat. He was then flying a fews days a month with Flybe on the Q400.
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Thanks Basil, quite possibly, although initial reading of the report that may not quite fit? Admittedly the initial bulletin doesn't state either way.
The sequence of events was:
The very first bit of the subsequent advice published by Saab, in response to the incident, to operators is interesting too, as it implied that some operators/pilots may not know that manual control inputs or main trim switch inputs do not disengage the AP on this type. That in turn implies that some pilots may "instinctively" think that manual control inputs disable the AP and they don't necessarily have to hit the Disconnect button?
"Manual control inputs will not cause the autopilot to disengage and the main trim switches are disabled when the autopilot is engaged. Consequently, operation
of the main pitch trim switches will not have any effect on aircraft trim nor cause the autopilot to disengage.
Disengaging the autopilot is normally done by pushing the disconnect button on either control wheel..."
The sequence of events was:
- Approach with AP On with Heading Select and Altitude Tracking modes selected
- Decision was made to discontinue, and the pilot then manually turned the aircraft using control inputs. So he was manually making control inputs before the lightning strike, whilst the AP was still engaged. (I'm interested though, on a type like the Saab 2000, if the approach was discontinued and needed manual control inputs like a heading change, would a crew disconnect the AP first or not? Maybe he thought the manual control inputs had auto-disconnected the AP at this stage in the flight?)
- As rolling out, lightning strike and pilot pulled back in a climb in response and (tried) to manually add in more up-trim to boot. Initially he "won" against the AP, but it progressively added more and more down-trim to get back to its altitude setting
The very first bit of the subsequent advice published by Saab, in response to the incident, to operators is interesting too, as it implied that some operators/pilots may not know that manual control inputs or main trim switch inputs do not disengage the AP on this type. That in turn implies that some pilots may "instinctively" think that manual control inputs disable the AP and they don't necessarily have to hit the Disconnect button?
"Manual control inputs will not cause the autopilot to disengage and the main trim switches are disabled when the autopilot is engaged. Consequently, operation
of the main pitch trim switches will not have any effect on aircraft trim nor cause the autopilot to disengage.
Disengaging the autopilot is normally done by pushing the disconnect button on either control wheel..."
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Ah, my apologies, I need to read reports properly!
You're right, the bulletin doesn't say (and my error was saying the report stating that pilot made manual control inputs to turn away to a new heading after discontinuing the approach.....re-reading it actually doesn't say the pilot used the control column to initiate roll/heading change).
Further re-reading it, it implies it is more in line with what Basil said, they probably left it on AP and used it to change heading after discontinuing approach....this is implied by the event straight after the aircraft just completed the roll out and the almost-immediately-after lightning strike with the commander announcing that "he had control". This means he probably didn't have his hands on the control column prior to the lightning strike but he was effectively announcing he now had his hands down to it.
You're right, the bulletin doesn't say (and my error was saying the report stating that pilot made manual control inputs to turn away to a new heading after discontinuing the approach.....re-reading it actually doesn't say the pilot used the control column to initiate roll/heading change).
Further re-reading it, it implies it is more in line with what Basil said, they probably left it on AP and used it to change heading after discontinuing approach....this is implied by the event straight after the aircraft just completed the roll out and the almost-immediately-after lightning strike with the commander announcing that "he had control". This means he probably didn't have his hands on the control column prior to the lightning strike but he was effectively announcing he now had his hands down to it.
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This was a disorientating experience, and would result in a significant reduction in spatial awareness.
You can discuss these events during recurrent training, but until you actually experience it you don't fully appreciate just what impact it can have on your mental processes at the time.
Sleepless nights are not uncommon, and visits to the "Trick Cyclist" would be perfectly understandable.
The Captain was PF, and following the event he said " I have control ". This implies reversion to manual flying? So did the AP "cavalry charge" alert sound due to the strike, but the AP stayed engaged?
Why did he not push the AP disconnect button on the control wheel? The effects of mild shock?
The AP operation of the 2000 is not the same as the Saab340 which I guess was the crews previous type? On the 340, operating the pitch trim switch WILL disconnect the AP. This is not the case on the 2000. You can see how confusion might arise.
You can discuss these events during recurrent training, but until you actually experience it you don't fully appreciate just what impact it can have on your mental processes at the time.
Sleepless nights are not uncommon, and visits to the "Trick Cyclist" would be perfectly understandable.
The Captain was PF, and following the event he said " I have control ". This implies reversion to manual flying? So did the AP "cavalry charge" alert sound due to the strike, but the AP stayed engaged?
Why did he not push the AP disconnect button on the control wheel? The effects of mild shock?
The AP operation of the 2000 is not the same as the Saab340 which I guess was the crews previous type? On the 340, operating the pitch trim switch WILL disconnect the AP. This is not the case on the 2000. You can see how confusion might arise.
I do have to wonder why the system was designed to allow pitch trim with the AP engaged.
On every type I've flown, manual pitch trim with the AP engaged disconnects the autopilot immediately. Indeed on one, using the pitch trim to disengage the autopilot was the most common method used by pilots (the other was the MCP button) as the master cutout switch on the yoke also took out the YD, which was typically not taken out until minimums.
On every type I've flown, manual pitch trim with the AP engaged disconnects the autopilot immediately. Indeed on one, using the pitch trim to disengage the autopilot was the most common method used by pilots (the other was the MCP button) as the master cutout switch on the yoke also took out the YD, which was typically not taken out until minimums.
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Wow, what a scary incident? Tsk tsk tsk! How did this incident escaped notice by aviation forums? Hmmmmmmm.
The A300 Supervisory override feature with A/P engaged and THS auto-trimming was the cause of a couple of fatal accidents.
The A300 Supervisory override feature with A/P engaged and THS auto-trimming was the cause of a couple of fatal accidents.
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Would the Go Around buttons in the power levers have solved the problem? Haven`t flown 2G,but in 340,if i remember right,GA buttons disconnected the a/p and Eadi moustache reverted to G/A pitch guidance,so it was hand-flying then on. Correct me if i`m wrong.
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The lightening strike triggered the AP disconnect "cavalry charge" to sound.
They believed that the AP had disconnected ~ that was their mind set ~ that was the fundamental issue ~ until the penny finally dropped.
Learn from the mistakes of others, as you won't live long enough to make them all yourself.
They believed that the AP had disconnected ~ that was their mind set ~ that was the fundamental issue ~ until the penny finally dropped.
Learn from the mistakes of others, as you won't live long enough to make them all yourself.