Just came over KHQ news from Spokane.

Alaskan Airlines flight 631 from Reno to Seattle turned back due to "trim motor" problems. Said the motor was working "off and on".

Although it wasn't an emergency landing, the pilots thought it best to turn back. Passengers said everyone was terrified and thought that they were headed for the same fate as the other flight.

-- Steve Baxter (chicoqh@home.com), February 06, 2000

Answers

I should have mentioned that the aircraft was another MD-80.

-- Steve Baxter (chicoqh@home.com), February 06, 2000.

OOoooooooooooooooooooooooooooooooooooooo
Tooo many for "coincidence"

A horrible LONG drawn-out death, sheer terror, 11 minutes of being flung around a crazy plane

-- no fly (zone@2000.noway), February 06, 2000.

At least 3 flights with stabilizer problems in less than 5 days. Not just coincidence. Somewhere along the line in the system that controls those stabilizers there has to be some faulty coding.

"Planes will not fall from the sky"

... Senator Bob Bennett

-- Hawk (flyin@high.again), February 06, 2000.

http://www.washingtonpos t.com/wp-srv/aponline/20000206/aponline024813_000.htm

Alaska Jet Lands After Problem
The Associated Press
Sunday, Feb. 6, 2000; 2:48 a.m. EST

RENO, Nev.  An Alaska Airlines MD-80 jet returned to Reno's airport shortly after takeoff on Saturday night after its pilot reported problems similar to those under investigation in Monday's crash off the California coast, officials said.

The Seattle-bound flight left Reno/Tahoe International Airport at about 7 p.m. and returned about eight minutes later when the pilot reported motors controlling the plane's horizontal stabilizer were operating improperly, said Jack Evans, an Alaska Airlines spokesman.

The Saturday night flight made a rough landing, but none of the 129 people aboard were injured.

The stabilizer is the wide part of the tail that helps to keep a plane level. Investigators are looking into possible problems with the stabilizer on Alaska Flight 261, an MD-83 which crashed on Monday in the Pacific Ocean north of Los Angeles, killing 88 people.

As the Reno flight returned, "there was a lot of crying and a lot of praying because a lot of people were probably thinking about that crash," said passenger Dennis Smythe of Anchorage, Alaska.

As flight attendants donned life jackets and explained crash procedures, "we all just looked at each other and said we loved each other, kind of holding on," passenger Sandy McCollum told KRNB-TV.

Evans said the plane's motors likely overheated while the airplane was on the ground.

"We suspect people are being very cautious, and they are moving the stabilizer up and down and through a full cycle ... and it's overheating the motors," he said.

On Tuesday, an American Airlines MD-83 reported trouble with its horizontal stabilizer after takeoff and safely returned to Phoenix.

-- Steve Baxter (chicoqh@home.com), February 06, 2000.

Ya.... right....

"We suspect people are being very cautious, and they are moving the stabilizer up and down and through a full cycle ... and it's overheating the motors," he said.

Like all pilots don't do that in their preflight checks?... lets try to be real....

-- Casper (c@no.yr), February 06, 2000.

Life jackets over the DESERT?

-- go ahead (pull@the.other.one), February 06, 2000.

Me I say go by boat or dont go!

-- r lizana (noah@on mtn.safe), February 06, 2000.

Back in December I heard a radio broadcast concerning y2k and planes. They took a 747 rolled the clock ahead to 2000 and sat on the runway for 2 hours with the plane running. All seemed to work well,,,,,,,, untill they started to taxi for take off. Their main computer went out. The takeoff was aborted. Why????????? Because a CHIP that controled the cooling fan for the puter craped out. The puter OVERHEATED and shut down. Notice, the word OVERHEATED in this article?

Got fans?

-- Scotty (blehman202@aol.com), February 06, 2000.

Yes, stabilizer problems - just like our world.

-- paul leblanc (bronyaur@gis.net), February 06, 2000.

By now you'd think the Airlines would have a clue that something potentially serious is happening.

-- deplane (deplane@deplane.deplane), February 06, 2000.

Afghan airliner with 151 people missing

An Afghan Ariana airliner with 151 people on
board has been missing since 10 a.m. Sunday,
according to a report by the Afghan Islamic
Press (AIP).

Asia Briefs

-- spider (spider0@usa.net), February 06, 2000.

Spider, here's more on your Afghan flight. It was hijacked by non- Y2k-compliant spiky-haired mutants.

CNN Article

I would expect it would take around 10-15 seconds to run the stabiliser trim from one extreme to the other or around 30 seconds for a full cycle. One statement that didn't make it into the clip was that it takes a minute to a minute & a half to overheat the trim motor. Either the pilots are pretty paranoid, or there is a real problem with the stabiliser.

I wouldn't be to quick to dismiss it as paranoid pilots. However, it is NOT Y2k.

-- Mikey2k (mikey2k@he.wont.eat.it), February 06, 2000.

-- Mikey2k commented:

"I wouldn't be to quick to dismiss it as paranoid pilots. However, it is NOT Y2k."

Well Mr. "Know It All" do you have any FACTS to back up this to date baseless statement??

Ray

-- Ray (ray@totacc.com), February 06, 2000.

Check this out, amazing Airline Events List:

http://www.egroups.com/group/humptydumptyy2k/1057.html?

-- list (list@list.list), February 06, 2000.

JoeSchmo: The tire on my car blew out.

Mikey2k: Looks like you have a problem there, but it's NOT Y2k related.

Ray: Well Mr. "Know It All" do you have any FACTS to back up this to date baseless statement??

Mikey2k: Ray, were are the date-related functions in keeping air in the tire?

My experience in the aviation industry is the basis for my statement that Y2k is not a factor in the stabiliser trim system. No chips in this aircraft's system and no date functions either.

Some more background on the situation in the thread

Do you have any facts on which to base any speculation that a Y2k bug is the cause of the MD8x stabiliser problem? (besides the calendar)

-- Mikey2k (mikey2k@he.wont.eat.it), February 06, 2000.

Mikey,

How does the control system for the stabilizers supply timed electrical pulses to the servomotors without some type of time reference with which to measure the duration of the pulses?

-- Hawk (flyin@high.again), February 06, 2000.

Mikey2k commented:

"My experience in the aviation industry is the basis for my statement that Y2k is not a factor in the stabiliser trim system. No chips in this aircraft's system and no date functions either.

Some more background on the situation in the thread

Do you have any facts on which to base any speculation that a Y2k bug is the cause of the MD8x stabiliser problem? (besides the calendar) "

Well Mikey2k, you sure do sling around GENERALITIES here, any possibilities of telling the forum EXACTLY what it is you do or did in the aviation industry that would allow us to believe your statement "it is NOT y2k related".

I didn't say it was y2k related but YOU said "it was NOT y2k related".

Tha BALL is in your court Mikey2k.

Ray

-- Ray (ray@totacc.com), February 06, 2000.

Just got back up from ROFLMAO when I read that Ray said "well Mikey2k you sure do sling around generalities here"

You can read more on this thread . Ray, you're going to believe and disbelieve what you want to, and no fact is going to change your mind. I'm not going to waste more time on you.

-- Mikey2k (mikey2k@he.wont.eat.it), February 06, 2000.

Mikey said...

"I'm not going to waste more time on you."

I suspected you'd come back with something like that, because you don't have an answer to my last question. Why do you say it isn't Y2K related when in truth you don't really know that, is it just because it is the easiest way out?

-- Hawk (flyin@high.again), February 06, 2000.

Hawk, the reason I didn't answer your question is either because I missed it or because Ray's humor made me forget it.

I am familiar with an autopilot that generates timed pulses to drive a trim actuator. No embedded chip involved like you're probably thinking of, just a simple oscillator. The equivalent would be a metronome used by piano students -- no date function involved. Once the autopilot disconnects, the trim is controlled by pilot trim switches and relays. Also, your question was answered by others on the thread I reference two entries back on this thread -- a thread you started. Were you disappointed with the answers you got on that thread? They seemed adequate enough.

As far as a Y2k bug causing a problem, yes it could happen somewhere sometime. This is not such an incident. If a Y2k bug ever does cause a problem, it will be lost in the noise of Carl Jenkins' postings.

-- Mikey2k (mikey2k@he.wont.eat.it), February 06, 2000.

As far as a Y2k bug causing a problem, yes it could happen somewhere sometime.

Exactly.

This is clearly a Y2K problem.

-- (dave454@grepmor.net), February 06, 2000.

The folks on the forum are STILL waiting for an answer Mikey2k, or maybe we have the answer!!!!

Ray

-- Ray (ray@totacc.com), February 06, 2000.

Mikey,

A metronome? Gimme a break! You're telling me that the pilot has to go back and adjust the counterweight every time he wants the stabilizers to move to a different position? LOL!!

No, I wasn't satisfied with the answers I got on the other thread, and that's why I asked you. Cherri went on and on with elaborate explanations of how the Boeing was designed 30 or 40 years ago, but no one has yet been able to answer my question. How does this "ocillator" determine how to change the duration of the pulse to the servomotors when activated by the pilot to change position? Would it not have to have some type of RELATIVE TIME REFERENCE? In order to measure your heart rate to find out whether it is 60 beats per minute or 72 beats per minute, you have to look at a clock, do you not?

-- Hawk (flyin@high.again), February 06, 2000.

Whether Y2K related or not, after this many mishaps I can't believe people are still getting on planes. At least that particular model. I know I wouldn't. Yeah, and I know all the 'facts' about planes being safer than cars. Still, if a car goes bust you pull over to the side of the road...can't do that in a plane.

-- Kyle (fordtbonly@aol.com), February 06, 2000.

As I suspected, no answer.

-- Hawk (flyin@high.again), February 06, 2000.

From what i understand , a "clock" in this context , means a timed electrical pulse generated by some form of occilator (sp) , it doesn't need a point of reference as it occilates at a known frequency. similar to the crystal used to generate the clock pulse's used to drive your computers CPU.

-- XOR (drwizzard@usa.net), February 06, 2000.

Sorry , to clarfiy , to adjust the pulses generated one would pass the pulse through a divide or multiply logic circut , making the pulse train faster or slower but still occilating at a known frequency.

-- XOR (drwizzard@usa.net), February 06, 2000.

XOR,

Any risk of overload, overheating, or fire from such types of circuitry? Wouldn't it be lighter in weight and safer to simply control the pulse output rate directly at the source of the voltage, rather than split it up after it has already been discharged?

-- Hawk (flyin@high.again), February 06, 2000.

My mention of metronome was as an analogy. A metronome is a mechanical oscillator. The oscillator I mentioned was electronic. For a stabilizer trim actuator the frequency of oscillation is on the order of 3 times per second. The method of changing the speed is to make each pulse wider or narrower so the actuator moves more or less with each pulse. This is pulse width modulation (PWM -- as mentioned in the previous thread). The oscillator generates a triangular- shaped waveform. The pulse duration is changed by a voltage between the extremes of the waveform which is compared to the waveform -- a voltage near that of one extreme of the waveform generates a long pulse and a voltage inear that of the other extreme generates a narrow pulse. A voltage outside the extremes of the waveform will generate either a steady pulse or none at all, depending on which side. This type of control is active when the autopilot is engaged, and no, there is no relative time reference.

But when the pilots are in control of the trim actuator, there's no oscillator involved -- just the control switches and relays.

No embedded processors with date functions involved. The only thing Y2k related about this crash was the year number when it happened.

-- Mikey2k (mikey2k@he.wont.eat.it), February 06, 2000.

Hawk , >Any risk of overload, overheating, or fire from such types of >circuitry?

Firstly I am not very knowledgeable as to how these systems are implemented in aircraft so i can only hypothersise , but usually the clock will produce low voltage TTL output, generally <10v , this current needs to be increaced once it is at the desired frequency in order to drive/operate higher voltage switching/electro-mechanical devices. I can't picture a fire/overload with the pulse generating circut itself, but may occur elsewhere in the system. Overheating prehaps if the circut was producing a too higher rate of pulses/erratic pulses for a long period of time.

>Wouldn't it be lighter in weight and safer to simply control the >pulse output rate directly at the source of the voltage, rather than >split it up after it has already been discharged?

Not positive about how this is done but : The source of the voltage as i can see it would be one of the main electrical buses, attached to this would be a "little black box" that would have a range of frequencies that it can output. Assumning that you have to spliyt the voltage at source , it would probably involve splitting one if the electrical busses such that it carries multiple currents and in that case the lines carring the pulses could be interfeared with by EMI from the other electrical systems running in paralel. The circutry involved is insignificant in weight.

If there are aircraft engineers about that can explain in more detail how the electrics function in aircraft i might get a clearer idea.

-- XOR (drwizzard@usa.net), February 06, 2000.

Thanks XOR, I just found proof that microprocessors can be used as pulse train generators.

pulse train generator from embedded chips

Since these aircraft are only about 8 years old, I wouldn't be suprised if microcontrollers were used to generate the pulse train to the servomotor, as this would reduce the risk of fire caused by sparks or short circuits from unnecessary wiring and analog circuitry.

-- Hawk (flyin@high.again), February 06, 2000.

The Bulletin 1391 is a Pulse Width Modulated, single axis AC servo drive

The 1391-DES digital drive has the same features as the 1391 series products, but takes advantage of a microprocessor-based control structure.

-- Hawk (flyin@high.again), February 06, 2000.

Boeing MD-80 and MD-90 Family

You too Cherri, planes have changed a bit since the Vietnam days...

Technology advancements in the MD-80 include aviation's first digital flight guidance system.

-- Hawk (flyin@high.again), February 06, 2000.

Hey Hawlk,

You are acting like a MORON. If you want to know how does this "ocillator" determine how to change the duration of the pulse to the servomotors when activated by the pilot to change position?

I suggest you get off of your ignorant ass and go take a course in electronics. The fact that you do not understand HOW it works, does not change the fact that it functions with any "people type clock".

Do you expect someone to teach you aircraft systems or electronics? Get over yourself, geeze.... You are ridiculous! Sitting there demanding that others who are more educated than you reply to your demands. How can someone show you, if you do not have the ability to understand when they do? Or the intent?

-- Cherri (sams@brigadoon.com), February 07, 2000.

Blow me Cherri.

I don't want to know about stupid oscillators because the aircraft has a digital flight control system. That was my whole point you dimwitted bimbo.

-- Hawk (flyin@high.again), February 07, 2000.

" I would expect it would take around 10-15 seconds to run the stabiliser trim from one extreme to the other or around 30 seconds for a full cycle. One statement that didn't make it into the clip was that it takes a minute to a minute & a half to overheat the trim motor. Either the pilots are pretty paranoid, or there is a real problem with the stabiliser."

30 seconds for a full cycle and 60-90 seconds to overheat? Not much of a safety factor there, is there. F*ing accountants at it again.

-- A (A@AisA.com), February 07, 2000.

A - not necessarily beancounters. Airplanes are the only sort of engineering where huge safety margins are out of the question. The reason is simple: a plane built with the same sort of safety margins one puts in a building or a bridge would never get off the ground, because it would be too heavy! Every extra pound weight in the airframe is a pound subtracted from the maximum passenger and cargo load.

Working within the difficult constraints that flight imposes, the engineers do a fine job. You're more likely to die is a car crash getting to and from the airport, than in a plane crash between airports.

As for the spate of stabilizer problems ALL WITH ONE AIRLINE this is extremely suggestive of either defective service procedures or defective spare parts being used by this one organisation. If it were any sort of designed-in Y2K problem, the problems would be spread equally over all airlines operating this model of plane, which it isn't. I'm quite sure that the crash investigators will be studying these things most carefully, and there's little point trying to outguess them.

-- Nigel (nra@maxwell.ph.kcl.ac.uk), February 07, 2000.

Nigel:

This is a matter of some importance to me; not trivial. I've been on these buggars all week. In many threads, people keep saying "all on one airline". Don't remember it that way. American and Alaska both start with A but have little else in common.

Best wishes,,,,

-- Z1X4Y7 (Z1X4Y7@aol.com), February 07, 2000.