Flydubai Flight 981, 737, Rostov-on-Don, Russia

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3WE
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Re: Flydubai Flight 981, 737, Rostov-on-Don, Russia

Postby 3WE » Sat Apr 30, 2016 3:58 pm

I experienced somatogravic issues during my most recent missed approach in IMC in the 182RG. Everything felt and sounded fine while I was fiddling with the radio and when I resumed my scan I was leveled off and accelerating instead of climbing at Vy. Contributing factor was probably that this was the one one with the bigger STC'd engine and has 15% more power than I'm used to. Very real scary phenomenon but I don't think it was the cause of this accident.

More likely, especially with underslung engines, is that they had excessive pitch up due to skill/scan/distraction, and then overreacted.
Bradley...look at what I bolded in the quote.

You had a somatographic illusion...yeah, they are powerful...(I don't know this first hand, but the classic lean over and back and grab a map makes it into lots of "What I Learned from That" articles).

But you and you alone did not enter a 50 degree dive (with Gabriel Ardvark2zz) calculating that would result in -1G.

This is two professional guys and let me repeat- I find "a momentary level off" to be within the realm of plausible screw ups...But to 1) Execute an OK climb for 2000 feet and then nose over into a 50 degree dive??? without taking a peek at the attitude indicator???
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Gabriel
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Re: Flydubai Flight 981, 737, Rostov-on-Don, Russia

Postby Gabriel » Sun May 01, 2016 8:27 am

But you and you alone did not enter a 50 degree dive (with the MAK finding in the FDR) that would result in -1G.
Fixed.

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Re: Flydubai Flight 981, 737, Rostov-on-Don, Russia

Postby PurduePilot » Sat May 07, 2016 4:42 am

I experienced somatogravic issues during my most recent missed approach in IMC in the 182RG. Everything felt and sounded fine while I was fiddling with the radio and when I resumed my scan I was leveled off and accelerating instead of climbing at Vy. Contributing factor was probably that this was the one one with the bigger STC'd engine and has 15% more power than I'm used to. Very real scary phenomenon but I don't think it was the cause of this accident.
I just shot like 10 missed approaches in the sim during my recurrent last week. Even with 27,000lbs of underslung might per side, no somatogravic illusions. None! That's how awesome I am.
That's a lot more approaches than I have shot in the last year.
And do you really think a sim can simulate this sensation? Honest question. Just seems a little difficult for the simulator to recreate using only deck angle...

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Re: Flydubai Flight 981, 737, Rostov-on-Don, Russia

Postby flyboy2548m » Sat May 07, 2016 2:27 pm

I just shot like 10 missed approaches in the sim during my recurrent last week. Even with 27,000lbs of underslung might per side, no somatogravic illusions. None! That's how awesome I am.
That's a lot more approaches than I have shot in the last year.
And do you really think a sim can simulate this sensation? Honest question. Just seems a little difficult for the simulator to recreate using only deck angle...
Beats me. You coulda just acknowledged my awesomeness...
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3WE
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Re: Flydubai Flight 981, 737, Rostov-on-Don, Russia

Postby 3WE » Sat May 07, 2016 8:23 pm

I experienced somatogravic issues during my most recent missed approach in IMC in the 182RG. Everything felt and sounded fine while I was fiddling with the radio and when I resumed my scan I was leveled off and accelerating instead of climbing at Vy. Contributing factor was probably that this was the one one with the bigger STC'd engine and has 15% more power than I'm used to. Very real scary phenomenon but I don't think it was the cause of this accident.
I just shot like 10 missed approaches in the sim during my recurrent last week. Even with 27,000lbs of underslung might per side, no somatogravic illusions. None! That's how awesome I am.
That's a lot more approaches than I have shot in the last year.
And do you really think a sim can simulate this sensation? Honest question. Just seems a little difficult for the simulator to recreate using only deck angle...
Aggie thinks it's adequate for the broader concept of ignore whatever $20 illusion you feel and instead, follow "the instruments".
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3WE
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Re: Flydubai Flight 981, 737, Rostov-on-Don, Russia

Postby 3WE » Wed May 18, 2016 8:57 pm

...the nose-down trim operated for 12 seconds...
Dare I suggest a $20 word? "Microsleep" (no, not as a single, primary cause, but as something that's kind of plausible and potentially significant).
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Re: Flydubai Flight 981, 737, Rostov-on-Don, Russia

Postby elaw » Wed May 18, 2016 9:56 pm

Or possibly something much more basic like a shorted or stuck switch?

I imagine the FDR probably records whether the pilot(s) were commanding trim movement (as opposed to the command coming from some sort of automatic system) but I doubt it has the ability to detect whether someone was actually applying force to the switch.
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3WE
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Re: Flydubai Flight 981, 737, Rostov-on-Don, Russia

Postby 3WE » Wed May 18, 2016 10:11 pm

Or possibly something much more basic like a shorted or stuck switch?

I imagine the FDR probably records whether the pilot(s) were commanding trim movement (as opposed to the command coming from some sort of automatic system) but I doubt it has the ability to detect whether someone was actually applying force to the switch.
Indeed.

Conversely, the talking point, "no mechanical malfunction" seems to be 'sort of established as fact' at the phorum of fotography and phallisies.

If it's a nose-down runaway trim, I'd think the FDR would also be recording (and the investigators reporting) an associated relentless pull up* (oh the ironing).

*...and maybe some indicative comments on the CVR
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Gabriel
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Re: Flydubai Flight 981, 737, Rostov-on-Don, Russia

Postby Gabriel » Thu May 19, 2016 3:52 pm

...the nose-down trim operated for 12 seconds...
Dare I suggest a $20 word? "Microsleep" (no, not as a single, primary cause, but as something that's kind of plausible and potentially significant).
Maybe, but a negative G would be a strong wake-up call (but maybe it is to late by then, if not for a recovery to be technically possible, for a confused, fatigued, sleepy pilot to get its wits back)

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Gabriel
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Re: Flydubai Flight 981, 737, Rostov-on-Don, Russia

Postby Gabriel » Thu May 19, 2016 3:55 pm

Or possibly something much more basic like a shorted or stuck switch?

I imagine the FDR probably records whether the pilot(s) were commanding trim movement (as opposed to the command coming from some sort of automatic system) but I doubt it has the ability to detect whether someone was actually applying force to the switch.
Well, you answered your own question. The thumb switch may be "active" with no pilot holding its thumb on it (a short in the switch or the switch getting stuck after a normal brief press by the pilot).

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Re: Flydubai Flight 981, 737, Rostov-on-Don, Russia

Postby PurduePilot » Fri May 20, 2016 4:50 am

Electric trim control uses two switches. Both must be activated in the same direction to get trim motion, in order to reduce probability of an electrical short or jammed switch causing uncommanded motion.

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Gabriel
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Re: Flydubai Flight 981, 737, Rostov-on-Don, Russia

Postby Gabriel » Fri May 20, 2016 1:25 pm

Electric trim control uses two switches. Both must be activated in the same direction to get trim motion, in order to reduce probability of an electrical short or jammed switch causing uncommanded motion.
Interesting. Thanks for the data.

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Re: Flydubai Flight 981, 737, Rostov-on-Don, Russia

Postby flyboy2548m » Fri May 20, 2016 2:07 pm

Electric trim control uses two switches. Both must be activated in the same direction to get trim motion, in order to reduce probability of an electrical short or jammed switch causing uncommanded motion.
Interesting. Thanks for the data.
I'm surprised an aerodynamicist of your caliber didn't know that, Gabby.
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Re: Flydubai Flight 981, 737, Rostov-on-Don, Russia

Postby PurduePilot » Sun Jun 04, 2017 8:30 pm

Electric trim control uses two switches. Both must be activated in the same direction to get trim motion, in order to reduce probability of an electrical short or jammed switch causing uncommanded motion.
Interesting. Thanks for the data.
I'm surprised an aerodynamicist of your caliber didn't know that, Gabby.
Aero guys don't usually get into system safety analyses. I don't know how I got this job.

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Re: Flydubai Flight 981, 737, Rostov-on-Don, Russia

Postby flyboy2548m » Mon Jun 05, 2017 2:58 pm

Aero guys don't usually get into system safety analyses. I don't know how I got this job.
Perhaps not, but we're talking about the very Greatest Aerodynamicist in Argentine History (certainly the most prolific one). How could something so elementary have possibly slipped his mind?
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