MU5735 chinese airlines crash

Liquid

NFLTG
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Over there
Seems simple enough...

Surprise switch to manual, roll aircraft 180 degrees and pull hard into an inverted +G turn towards the ground.

How quickly would the plane be beyond recoverable airspeed?

 

Rain Man

Super Anarchist
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Wet coast.
Seems simple enough...

Surprise switch to manual, roll aircraft 180 degrees and pull hard into an inverted +G turn towards the ground.

How quickly would the plane be beyond recoverable airspeed?
My guess would 15-20 seconds.  Any B737 pilots here?  You'd think you would at least have a little fun and loop the thing before checking out, like that guy that stole the Q400 from Seatac.  Not sure he did loop it, but he certainly did some semi-aerobatic stuff with it.

My instructors told me that if I ever found myself in an inverted dive, not to try to pull through, the aircraft would break.  

 
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pbd

Super Anarchist
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Skimmed a lot of the posts here so don’t know if this was pointed out, but I saw some interesting commentary on another forum that stated

1) Neither Boeing or the FAA have any ongoing work on any kind of technical bulletin related to this crash, so in their view there was no mechanical failure to advise on, and

2) The person who read the report only stated to the media that the airplane going into a dive was only doing what it was told to do, with no further judgement.  That it was a suicide was inferred but not supported by any evidence, as yet.  Other possibilities include medical event where pilot collapses forward on the controls, sudden dive to avoid stealth UFO, or any number of other crazy, but not impossible, scenarios.  Weirder thing have happened, in other words.

Found it to be interesting food for thought 
IIRC, TWA actually used that as a possible excuse when one of their planes went down back in the 90’s

 

Mark_K

Super Anarchist
Makes sense ... so within the normal functioning range of a jetliner's elevator, the plane COULD get that angle of descent if the elevator is purposefully held down? Even 30,000 some feet per minute descent?

What is your opinion about the debris field some 6 miles from the crash site?
With trim rolled full down it could be held in a vertical dive, recently demonstrated by the 737 MAXes. I got a hunch the rumor is based on data from a flight systems recorder that shows the stick was pushed forward and THEN the trim adjusted, which precludes the possible suspect of electric trim-runaway condition. That does happen every once in awhile, the fix is pull the breaker and use the manual trim wheel to re-adjust. This is however one of the most-beloved gremlins for the guys conducting simulator training to spring on their students this condition has killed (AFAIK) nobody yet though. 

It would be no surprise for a plane pushed well past VNE (velocity never exceed) to start shedding parts. Cowlings, fairings, perhaps some engine parts like vanes. I wouldn't put much on some of it being miles away. 

 

mikewof

mikewof
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If Mike could do math, he would know that the aircraft probably exceeded Vne which is around 340 kts.  So 6 miles is about a minute, much more time than the aircraft would have taken to descend and impact the ground from its cruising altitude.  The aircraft will start shedding parts when it exceeds Vne.  Depending on the angle of descent and the speed, which could be greater than Vne, finding parts 6 miles away is not surprising.
I did the math with SOHCAHTOA and the published 30,000 fpm descent yesterday when @Raz'rtreated the vertical speed as the composite velocity, I came up with about 380 knots composite minimum, potentially faster than 400 knots, from the published velocity profile that I looked at online.

Mark's suggestion makes sense ... at that speed, the soft stuff, the cowlings and fairings and fiberglass bits would likely fly off first and end "upwind" of the crash site. Of course, that does not agree with the Chinese report that there were no mechanical failures, parts popping off of a plane would be a mechanical failure, potentially making it impossible to recover from that dive anyway, even if it wasn't the result of a psychopathic pilot.

The report may have said that there was no mechanical failure BEFORE the pilot went ape-shit.

 
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βhyde

Super Anarchist
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Seems simple enough...

Surprise switch to manual, roll aircraft 180 degrees and pull hard into an inverted +G turn towards the ground.

How quickly would the plane be beyond recoverable airspeed?
You'd be toast within seconds. If the 737 was flying at normal cruise speed (0.78 mach) and you initiated a roll, pulled hard towards the ground, you'd be at the 737's +2.5g limit pretty quick. In a normal aerobatic loop you pull about 3.5g - 4.0g, and that's with the plane decelerating as it comes over the top of the maneuver. If the 737 was pointed straight at the ground doing 0.78m you would most certainly exceed the Vne. However, exceeding Vne doesn't necessarily mean the plane instantly disintegrates. Being at Vne and then deflecting a control suddenly is an entirely different story. Don't ask me how I know this. 

 


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