AS261 -- Perhaps it was an embedded nut

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No, not the Hawk kind of embedded or the Hawk kind of nut.

I would caution that the following has not been confirmed by a statement from the NTSB. Appears to be information obtained by ABC news from other sources, and sometimes these turn out to be incorrect.

The following from the end of the ABC News article located at this link

Critical Evidence in Alaska Crash

Meanwhile, investigators now have another critical piece of evidence in the crash of Alaska Airlines Flight 261.

Officials found a large aluminum nut that is attached to a jackscrew, part of the mechanism that moves the horizontal stabilizer.

The threads inside the nut are completely stripped, ABCNEWS has learned.

Some, but not all, of the threads were found in the wreckage twisted around the jackscrew.

According to sources, that may mean the threads came off in stages, which would indicate the nut was worn down before the plane hit the water.

Boeing said Friday the nut is designed to wear and airlines should check them about every two years and replace them if necessary.

The Alaska Airlines plane that crashed was built in 1992, but sources tell ABCNEWS the stabilizer mechanism was made in 1979. Investigators are looking into this age difference.

However, mechanics interviewed said the age of the part is not necessarily a safety issue.

Also Friday, the NTSB reported that the salvage effort of the California coast and turned up more of the wreckage from Flight 261. The pieces included large portions of the right and left elevators and an 8-foot section of the outboard right stabilizer.

-- Mikey2k (mikey2k@he.wont.eat.it), February 12, 2000

Answers

Boy! I opened the post thinking the Squirrel King had sabotaged something again.

-- justme (justme@myhouse.com), February 12, 2000.

As an authority on nuts, let me say that this report is only slightly less speculative that the stories promulgating the jackscrew hypothesis have been thus far. If anything, by establishing that "some" of the threads of the nut were found inside the wreckage, they render the jackscrew hypothesis less credible, becuase the presence of threads (and here I am PRESUMING they are refering to identifiable metal shavings that were FORMERLY nut threads -- so I stand to be corrected) obviously tends to indicate that the nut was stripped during the course of the crash. Well ... maybe that's dependent on the housing of the jackscrew mechanism -- I don't do planes. Or cars. ANYHOO all other things being equal, the threads would be more likely present if the nut/jackscrew was stripped as the plane crashed, rather than if they wore or were stripped away over the course of preceding months/years during routine usage ....

>"<

-- Squirrel Hunter (nuts@upina.cellrelaytower), February 12, 2000.


Dear " embedded nut " ( alais Y2K Mikey ) ... Have you ever stripped a nut ? You exert extreme pressure to the bolt ( jackscrew with manual control as you frantically try to move the stabilizer from down to up, in a final effort to prevent your death and ALL the rest of the people aboard , AFTER the embedded chip in the computer controling said stabilizer , has MALFUNCTIONED when on autopiolt ( your final mistake in trying it again , following the first plung of several thousand feet ). Move on to some Koo Koo forum Mikey , where your " tallents " will still be mediocure ! Eagle

-- Hal Walker (e999eagle@FREEWWWEB.COM), February 12, 2000.

Hal, you are only slightly more rational sounding than Squirrel Hunter. Let's see -- you said something about "frantically try to move the stabilizer from down to up, in a final effort to prevent your death ... "

WRONG The NTSB reports that the stabilizer was stuck at the full nose down position. No frantically moving it back and forth.

After reading yours and Squirrel Hunter's posts, I am reminded that I am already at a "Koo Koo" forum.

-- Mikey2k (mikey2k@he.wont.eat.it), February 12, 2000.


more information LA Times , quote from end of article:

Scientists at the NTSB's metals lab will now try to determine what caused the damage to the stabilizer control mechanism of the accident plane and the two other Alaska Airlines jets. Inadequate lubrication, misalignment, the failure of an automatic shut-off, or contamination by outside material are among the possibilities suggested by independent experts.

and this from Reuters , 1st two paragraphs.

A nationwide inspection of 1,100 planes touched off by an Alaska Airlines crash that killed 88 people has turned up 15 tail part problems in aircraft from eight airlines, federal aviation officials said on Saturday.

"The findings ranged from metal shavings found in jackscrew lubricant to metallic residue in the grease and a jackscrew with no lubricant," the Federal Aviation Administration said in a statement, adding that it was too early to draw any conclusions.

From this is sounds like the problems they found were not as serious as the one shown in the picture of the AS261 jackscrew. It sounds like they're being extra cautious which is warranted under the circumstances.

-- Mikey2k (mikey2k@he.wont.eat.it), February 12, 2000.



Possibly the stab went full nose down due to aerodynamic loads after the last threads holding it in place went. I know that in other model aircraft, the stab will move full nose up or down due to aero loads when the stab becomes unpowered.

The failure of the jackscrew ball nut is a failure in the same catagory as the o-ring failure on the space shuttle solid rocket booster. It's a failure that an inspection might have caught or a design difference might have avoided. But those two "mights" weren't there and there was a catastrophic failure.

As far as a 1979 part in the 1992 aircraft, that's going to be in the maintenance logs. Just like changing-out the alternator on your car for a rebuild, that rebuilt part could be older or newer than your car.

WW

-- Wildweasel (vtmldm@epix.ney), February 12, 2000.


That aircraft was serviced on January 30, the day before the crash. How could it go from not being noticed to such bad condition in one day?

-- did (something@cause.this?), February 12, 2000.

An ALUMINUM nut on a steel worm screw?

Hello?

-- Tom Carey (tomcarey@mindspring.com), February 12, 2000.


My dear sir,

An aluminum nut and a steel jack screw? Come on now,,,,They couldn't be so stupid as to use an aluminum nut! But man! If they did! Then no wonder the air liner went down. I just hope the inspectors check out this combination nut and jack screw set up on the other air craft.

For a space back in the 60-70 years we used aluminum in the electrical equipment, even feeder cables. But aluminum has way too many problems with thread gualding. Yes! I have seen many a large aluminum nut with it's threads stripped.

I just wonder what "junior" engineer thught up that design combo? I might have understood an aluminum jack screw...The nut is what has the turning pressure on it, not the jack screw. In any case Mikey. Good find there.

"As for me...I shall finish the Game"!

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~Shakey~~~~~~~~~~~~~~

-- Shakey (in_a_bunker@forty.feet), February 13, 2000.


An ALUMINUM nut on a steel worm screw?

Hello?

No... I don't think so... "have you seen the size of that thing?"...

Both the jack screw and follower nut are made of an aluminum alloy.. tough stuff by the pound :-)

Shakey..... me too :-)

-- Casper (c@no.yr), February 13, 2000.



Something wrong with my post? Looks to me like it's properly qualified and the limits of my knowledge of the mechanism and ALL mechanics laid forth at the outset. Hope Mikey2k, that you don't find yourself eating your words.

>"<

-- Squirrel Hunter (nuts@upina.cellrelaytower), February 13, 2000.


Is there no expert, anywhere? Gary's rantings, may have foundation, along with my consumer mentality research. Fill those water bottles, can't hurt.

-- Does Anybody (Reallyknowwh@ttimeitis.com), February 13, 2000.

Squirrel Hunter, I apologise for my comments about you.

-- Mikey2k (mike2yk@he.wont.eat.it), February 13, 2000.

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