The crash of Alaska Airlines Flight 261 was caused by non-compliant on-board flight control computers. The main computer on the flight deck, which acts as the central nervous system for the entire aircraft, uses the current date and time (including GMT for some functions). The autopilot and all computerized digital electronics on the aircraft are of course networked into the central system, and quite dependent upon it in many ways. One of the smaller computers, which receives its digital commands either from the pilot or autopilot through the central computer, is of course the digital servo drive unit, which then relays the appropriate timed electrical pulses to the stabilizer servomotors in the tail section of the aircraft.

As you can imagine, any plane with this type of system (which includes nearly every commercial passenger aircraft built within the last 15 years), is loaded with all kinds of microprocessors, or embedded systems. These microprocessors were designed to intepret the digital instructions from the central computer, and execute the appropriate functions. Most of these microprocessors were programmed to receive input from the central nervous system computer in order to compute the required calculations needed to execute their various functions. The programmed code in some of them was written to utilize the date / time parameter of the central computer, in order to calculate and relay precisely timed instructions (sometimes to the nearest millisecond) to the control surfaces of the aircraft, including the stabilizers.

Somewhere in the link between the central computer and the stabilizer servomotors, microprocessors were not able to properly function when the current date and time were referenced, becuase they were outdated, non-compliant, and never properly tested. It may have been a malfunction within the autopilot system, but the most likely place where this error occurred is right here, within the digital servo drive unit...


(probably not the exact same model, but similar in function)

Some people are still confused about this. The SERVOMOTOR is the cylindrical object in the lower left corner of the image. It DOES NOT have any microprocessors. The SERVO DRIVE UNIT is the rectangular object in the right half of the image. It DOES have microprocessors. It is also networked to the central computer of the aircraft and the autopilot system, in order to receive its instructions and output its current status back to the flight deck. The microprocessors in these systems can come from different sources, some are compliant, some are not, and that is why we have seen several cases occur in the same aircraft, but not all aircraft. At the very least, all MD-80's should be grounded until all faulty units are replaced and the entire aircraft is thoroughly tested.

The entire world should thank Ed Yourdon and all forumites who tried so desperately to awaken the world to the seriousness of the problem. We knew that people would die if this issue were ignored, and they did. Sadly, because of corporate greed and ignorance, rather than an occassion to celebrate, we have an occassion for grief and despair. Even more unfortunate is the continuing lack of proper action in the aftermath of this tragedy, and the apparent efforts to conceal it from the public, leaving them at extreme risk. We all hope that the true problem will be revealed and repaired before any more lives are lost.

-- Hawk (flyin@high.again), February 08, 2000

Answers

For the idiot trolls, I'm going to show you how nice I am by saving you the effort of typing your response....

"Hawk, you ignorant moron." "Boy, you're really pissing in the wind this time." "You don't know a damn thing about airplanes, I work on them." "Hey there Hawk - boy you're really in the poop up to your neck." "Why don't you get off your ignorant ass and do some research." "Where's your proof?" "There's no date functions or digital chips on those planes, I know, I'm a mechanic." "I'm a pilot, and you're full of it." "You don't know a servomotor from an eggbeater." "You've been smoking too much dope you idiot." "It's just a mechanical failure." "There's NO way it is Y2K related."

-- Hawk (flyin@high.again), February 08, 2000.

And my reply to the trolls... Jeeeez, you really think so? Well, uh, sorry about that, but I already typed it. And there's no way you can show us that this isn't true because the plane is under 600 feet of water. Damn! So sorry. :-)

-- Hawk (flyin@high.again), February 08, 2000.

Thanks Hawk, pay no attention to the Trolls, they have NEVER had anything of value to offer to the forum and IMHO NEVER will.

It is my understanding that the most dangerous periods for planes is on take off and landing. These recent problems have taken place at cruising altitude.

Ray

-- Ray (ray@totacc.com), February 08, 2000.

Hawk, let's be clear about your statement. Are you stating this as a theory or as an established fact?

-- Mikey2k (mikey2k@he.wont.eat.it), February 08, 2000.

Ray, your statement of danger on take off and landing has some truth, but you can in no way extrapolate that out to what is happening with the stabilizers or the crash of Flt 262. The danger on take off and landing is a totally different set of potential/possible scenarios. Thats like someone crashing their car due to brake failure and you saying that its your understanding that its always more dangerous to hit the brakes while traveling on ice. Taz....who has a few hour in the left seat under her belt.

-- Taz (Tassi123@aol.com), February 08, 2000.

hawk, I hope you've really enjoyed this fantasy.

-- bikey (bickey@haricot_vert.com), February 08, 2000.

No bikey, when I think about the people who needlessly lost their lives, I hardly consider this task enjoyable. But I do feel very obligated to let the truth be known in hope that someone will be able to get this problem resolved before more innocent victims are killed. That's the same reason most of us have felt driven to post on this forum for the last year and a half, regardless of attacks by those who tried to stop us.

-- Hawk (flyin@high.again), February 08, 2000.

Son, I KNOW you think you're helpin us all out, but you have to remember that you've got a TOUGH crowd here. Care to cite a few sources for this position?? It'd help a LOT more than the "stuff" that you followed your opening with.

Joss

-- Joss Metadi (warhammer@Pride.of.Mandeyne), February 08, 2000.

Joss,

I think you'll find more than sufficient validation at this link, so graciously provided by Rachel...

read what the experienced aviation professionals say

-- Hawk (flyin@high.again), February 08, 2000.

OK, I see that you've given up calling it a theory -- it's now the "truth". Since over 1000 of the MD-80 aircraft were produced, why is it that only one of them fell out the sky. Given so many aircraft, there must have been dozens in the air at the Jan 2000 to Feb 2000 GMT rollover. If it's a date problem as you state, then why is it that multiple aircraft didn't fall out of the sky last week Monday evening PST?

-- Mikey2k (mikey2@he.wont.eat.it), February 08, 2000.

Thanks for your analysis, Hawk. It's so sad that so many people had to die in order for some to learn the truth. Sadder still is the fact that thousands more will undoubtedly be killed in the next few weeks as the problem spreads. Maybe they'll find it in time, but I doubt it.

-- (jeffDD@ticon.net), February 08, 2000.

Mikey, I'll have to ask you to re-read my post. You missed part of it.

-- Hawk (flyin@high.again), February 08, 2000.

Hawk, I know I shouldn't be doing his homework for him....but anyway:

"The microprocessors in these systems can come from different sources, some are compliant, some are not..."

-- Kyle (fordtbonly@aol.com), February 08, 2000.

So you're saying that only some of these aircraft have non-compliant chips? You determined that surfing the net on your own computer? So exactly what is the identification (Model Number and Part Number) of the "black box" with the non-compliant chips? You owe it to the thousands of people yet to be killed by the faulty equipment to publish this information so that their needless deaths can be prevented.

-- Mikey2k (mikey2k@he.wont.eat.it), February 08, 2000.

Still, even though I think the level of occurrences is much too high to be coincidental I wonder why more planes haven't had problems. Or are we just not hearing about them?

-- Kyle (fordtbonly@aol.com), February 08, 2000.

The entire world should thank Ed Yourdon and all forumites who tried so desperately to awaken the world to the seriousness of the problem. We knew that people would die if this issue were ignored, and they did. Sadly, because of corporate greed and ignorance, rather than an occassion to celebrate, we have an occassion for grief and despair. Even more unfortunate is the continuing lack of proper action in the aftermath of this tragedy, and the apparent efforts to conceal it from the public, leaving them at extreme risk. We all hope that the true problem will be revealed and repaired before any more lives are lost.

Gotta agree with Mikey2K. If you feel so strongly this is the case you are honored bound to contact the press and possibly the NTSB with this information.

Steve

-- Steve (sron123@aol.com), February 08, 2000.

What is the part number of the processor which can be purchased from different manufacturers, some of which are compliant and some of which are not? Identify the compliant manufacturers and the non- compliant.

You've stated this as truth, so you must have this information as well. Why are you jeopardising so many lives by not releasing the specific information you must have in order to make your statement of truth?

-- Mikey2k (mikey2k@he.wont.eat.it), February 08, 2000.

Hawk: You forgot I flew in a plane once so that means that you are wrong, because, err, welll, just because. Anyway an expert on CBS thinks your wrong and they just know, don't they.

The amazing thing is the likehood for failure of any type increases with the complexity and interdependence of the system. Because so much is required to maintain lift and control an airplane or shuttle are some of the complex system that most people know. There is a possibility it could be bad parts/maintenance or just freaky coincidence, but for anybody to discount the possiblity is silly.

Also it amazes me that all the problems with oil refineries and airplanes are reported as separate isolated incidence. The failure rates are so high that the public's threshold for concern has risen with the mass belief that if I don't see it, it will not be there.

I guess what we don't know can hurt us.

-- Squid (ItsDark@down.here), February 08, 2000.

Hawk,

I really do think you are going off in the wrong direction on this crash. Sure, there are computers that monitor and control various functions in the modern aircraft. But, they are usually built with redundant features and can always be turned off.

The stabilizer problem was a mechanical problem. The signal for a full nose down trim somehow went to the stabilizer trim motor and the stabilizer started to trim nose down and didn't stop. The crew could have, and should have, caught it long before it became unmanageable. Remember, they were at cruise altitude when all that started and the stabilizer at that point is almost nuetral. From what I am reading now, they just didn't get the faulty signal stopped before the stabilizer ran to full nose down.

At that point the crew only had elevator control left to counteract the stabilzer out-of-trim condition. They probably did have the control yokes pulled all the way back to the stops to try to stop the dive. As the airspeed picked up the load on the mechanical parts of the elevator became extreme, and the loud noise they heard was likely the failure of the elevator actuator due to extreme pressure on it. After the elevator failed it was all over. That's why the plane first dived and then when it got inverted it went into an inverted spin which was not controllable.

But, it all started with a simple runaway stabilizer which *could* have been stopped had they acted quickly enough. Seconds are crucial in this case. I have seen this sort of malfunction in the simulator many times and if it is not stopped quickly enough it is all over. A computor *may* have started it all. Any number of simple signal failures may have started it, without any computor input at all. Once it starts the crew must intervene immediately or the result is just what you are seeing in this tragic accident. It is not too far fetched to say it is like a tire blow out in a car at over 100 mph. It is only controllable if you catch it immediately and do the right thing immediately.

Now, if you want to go on about how computors are overused in aircraft and how manual backups have been eliminated, fine, I will join you in that. But manufacturers have decided to build them that way now, the airlines are happy to buy them that way, and the FAA puts it blessing on the whole thing. So good luck in getting any of those parties to change their ways. In our modern world of cost controls, the engineers have run statistical models of how likely a failure will be, then balanced that against the cost of the accident. If the failure probability is very small compared to the savings in daily operating expense they go with it and let the lawyers deal with the unhappy families who see their loved ones hurt or killed. That's what we have come down to in a highly competitive, deregulated, industry. And the customer wants to get the ticket as cheap as possible. The customer will fly on virtually any airplane if the price is right. Just look back at that Value Jet crash in Florida.

-- Gordon (gpconnolly@aol.com), February 08, 2000.

Mikey,

"You owe it to the thousands of people yet to be killed by the faulty equipment to publish this information so that their needless deaths can be prevented."

Better safe than sorry. 88 people died. How many would you like to die before someone checks into this?

Steve,

"Gotta agree with Mikey2K. If you feel so strongly this is the case you are honored bound to contact the press and possibly the NTSB with this information."

ROTFLMAO!! Right, tell the NTSB, and end up in the Hudson River wearing cement overshoes! LOL! Those guys are paid to cover this stuff up! Do you know how much money will be lost in the transportation industry if someone proves this to the masses? $$$ billions my friend, $$$ BILLIONS.

-- Hawk (flyin@high.again), February 08, 2000.

I know there are a lot of press people reading this forum, so I hope they will have enough public visibility and protection to investigate this. I don't.

-- Hawk (flyin@high.again), February 08, 2000.

Jim Hall's speech today. Has some FDR info.

"In November, the alternate trim switch was changed."

"The alternate trim system from the American Airlines airplane is being examined."

-- Rachel Gibson (rgibson@hotmail.com), February 08, 2000.

computors are overused in aircraft and how manual backups have been eliminated, SNIP But manufacturers have decided to build them that way now, the airlines are happy to buy them that way, and the FAA puts it blessing on the whole thing. So good luck in getting any of those parties to change their ways. In our modern world of cost controls, the engineers have run statistical models of how likely a failure will be, then balanced that against the cost of the accident. If the failure probability is very small compared to the savings in daily operating expense they go with it and let the lawyers deal with the unhappy families who see their loved ones hurt or killed. That's what we have come down to in a highly competitive, deregulated, industry.

So now Gordon knows all about the airline industry. The Airlines may be de-regulated, bit the manufacturers are not involved in that, they do not cut corners to save money. Gordon they have not done away with backups, you are making a false statement. Safety is the main concern of aircraft manufacturers, what airlines do (they do not make the aircraft) with their regulations and flight issues is a different industry.

Hawk, you are going too far.

-- Cherri (sams@brigadoon.com), February 08, 2000.

Come on Hawk, let's give all those press people monitoring this forum some facts that they can pursue. 88 lost lives are too many. How will you be able to live with yourself after even more people die -- deaths that you could have prevented if only you had presented your facts here for the press people? You don't even have to worry about the cement overshoes if you post the information here -- after all you are posting anonymously.

-- Mikey2k (mikey2k@he.wont.eat.it), February 08, 2000.

Too far???

How far is too far when people's lives could be saved?

And you wonder why we have problems with the polly mentality. Sheesh.

-- Hawk (flyin@high.again), February 08, 2000.

I can see how Y2K could cause an elevator trim problem, maybe.

It's a little harder to see how it could make the tail fall off the plane. The two loud sounds the precede the plane's demise--they gotta be some kind of impact sound. The Navy was firing missiles at Pt. Mugu at the time the plane went down within miles of Pt Mugu.

-- Ceemeister (ceemeister@hotmail.com), February 08, 2000.

Come on Hawk, where's the vital information that will save lives?

Or maybe you're a different kind of bird. A chicken. No, not a chicken hawk, a CHICKEN.

-- Mikey2k (mikey2k@he.wont.eat.it), February 08, 2000.

Hey Mikey, do you buckle your seatbelt when you get in your car, or do you wait until you run into a brick wall before you decide that you need it? I think we all know who has the facts locked up in their high security labs, and that is why none of us will ever be able to prove anything. People are being bribed, documents are being shredded, and facts are being concealed as we speak. This job requires a private party with a lot of power to investigate, and fast.

-- Hawk (flyin@high.again), February 09, 2000.

Poor Hawk...you couldn't find anyone to attack, so you pick a fight with YOURSELF? And then fight back? HAHAHAHA! How's that for mental masturbation.

Personally, I like that theory about flight 261 drifting into secured naval airspace, and then being shot down by friendly fire. YIKES

The missing Tail

-- cin (cinlooo@aol.com), February 09, 2000.

Oh by the way Mikey, just wanted to say thanks again for the good article you provided yesterday. I appreciate the support.

"There is no way to manually move the stabilizer."

It's really unfortunate that these planes have become so dependent on computers that there was nothing the poor pilots could do to get control back from the malfunctioning computerized control system. That is just one of many very important lessons mankind should learn from Y2K... always allow for a manual override.

Aviation week, re: MD80

-- Hawk (flyin@high.again), February 09, 2000.

Gordon, It is great to see your input into this subject. I feel that its about time that someone with real industry knowledge started responding to some of these aviation claims, so thank you for joining in.

Cherri, FYI Gordon has probably more time in heavies in the left seat than everyone else here combined.

-- Malcolm Taylor (taylorm@es.co.nz), February 09, 2000.

Uh-oh, here comes that brainless vegetarian California bimbo bitch again, the wannabe psychologist. I bet you spend a lot of time masturbating... with your vegetarian friend, Mr. Cucumber! ROTFLMAO!!!

-- Hawk (flyin@high.again), February 09, 2000.

[Fair Use: For Education and Research Purpose Only]

Crash Puts Stabilizer Trim System Under Scrutiny

Crash Puts Stabilizer Trim System Under Scrutiny

Summary: Functioning, maintenance, back-up safety features, emergency procedures and recurrent training likely to be probed thoroughly in wake of Alaska Airlines MD- 83 loss

Source: Air Safety Week

Subject(s): Accident; Aircraft; Airline; Airport; Alaska; Bank; California; Carrier; Communications; Consulting; Electrical; Electronics; Emergency; Fire; Investigation; Mexico; New York; News; Newsgrid; Oregon; Phl; Pilot; Steel; Training; Transportation; Water

=============================================== (Excerpt from story).........................................

Scenario of the final moments

The Alaska Air pilots experienced what appears to be a progressive failure situation from some initial event. Whatever defeated them does not appear to be a simple continuation of the initial problem.

Apparently the crew had completed the checklist for a runaway trim situation and, through the carrier's ACARS (Airborne Communications Addressing and Reporting System), had asked a mechanic if there were "any hidden circuit breakers." NTSB Member John Hammerschmidt said the pilots radioed they were in a worsening situation. That could be explained by two possibilities: resetting the circuit breakers for the primary or alternate trim motor in an effort to improve the situation, which may have had the reverse effect by enabling a full nose- down jammed stabilizer. Or, they had a malfunctioning trim switch in the yoke, which ran the trim motor only in the undesirable direction - perhaps to the nose-down stops. The crew of an American Airlines [AMR] MD-80 faced a similar situation last Wednesday, when the first officer experienced a jammed horizontal stabilizer. Hammerschmidt said an electrical short in the first officer's yoke- mounted trim switch was found. The stabilizer, he said, "Would only function intermittently in the nose-down direction."

-snip-

===================================================

Note: Story is VERY long, so I snipped.

Hawk, you may find the entire story of interest. I appreciate your critical thinking. IMO, however, it is *wise* to present your information and observations as *theory* for the obvious reasons.

-- Dee (T1Colt556@aol.com), February 09, 2000.

Top of new answers.

-- (T@t.t), February 09, 2000.

Hawk:

You and I have discussed this several times. It seems you have now gone from speculation, which is all any of us are really doing, to proclaiming that you now have the facts and that we are killing people through a coverup. Mikey asked you to provide facts to back up your assertions and all I've seen as personal attack back. Gordon, an actual airline pilot, says you are barking up the wrong tree. The examples you give about fly by wire apply to aircraft like the F-16, not an MD-83. Sorry, but you've gone over the edge here. I expect to be flamed back but, while you're at it, why not answer Mikey's questions?

-- Jim Cooke (JJCooke@yahoo.com), February 09, 2000.

Jim,

It sounds like the information that Gordon is providing is taken directly from the NTSB report. The problem with that is that they have the authority to alter the facts however they choose, and to protect the interests of Boeing and other organizations if they are so inclined.

I have provided several links within several different threads, but you people apparently do not even read them because you refuse to believe that Y2K computer problems could cause such a tragedy.

Gordon explains all the efforts made to counteract the stabilizer problem, and that is perfectly credible, but he never explains what CAUSED the stabilizer problem, and why this is happening on so many planes almost simultaneously.

As I referenced above, from an article Mikey provided, there is no way to manually move the stabilizers because they are operated by a computer controlled system. Even if the pilots did act quickly enough to recover them from a runaway occurrence, it didn't work because the microprocessors which relay the instructions were down for the count. The signal cannot be transmitted if the line is dead.

-- Hawk (flyin@high.again), February 09, 2000.

Hawk, DC9/MD80 flight controls are hydraulic assist direct cables. The trims are servos.

-- Chief (bmc@sealret.com), February 09, 2000.

Hawk:

The stabilizers are different than the trim tabs. As others have posted, they are also controlled by hydraulic assisted cables. Even if every computer in the airplane was fried, you can still move the stabilizers manually. If there was a mechanical problem with the cables and/or the trim tab attachments, you're in big trouble if you don't take action fast.

The links that you provided have nothing to do with MD-83's. They described stability testing for fly by wire aircraft like the F-16 and F-22. If there's something there that I've missed about MD-83's I'd be happy to have you point it out to me.

Why do you believe the NTSB is trying to cover this up? I've never seen any evidence that the NTSB is in cahoots with airplane makers. Do you have some evidence for this or is this just how you feel about government agencies in general?

As a final point, if there were major problems with MD series aircraft, don't you think the Airline Pilots Association and the Flight Attendants associations would be up in arms, not to mention the Airline Passengers Association? The pilots and flight attendants put their lives on the line every day for us and they would be the first to refuse to fly in unsafe aircraft.

-- Jim Cooke (JJCooke@yahoo.com), February 09, 2000.

Thanks Chief, when I refer to the stabilizers, I am of course referring to the stabilizer trim, since that was the original cause of the crash that the pilots reported. I assumed everyone by now was aware of that. It has nothing to do with the hydraulic systems.

-- Hawk (flyin@high.again), February 09, 2000.

As I referenced above, from an article Mikey provided, there is no way to manually move the stabilizers because they are operated by a computer controlled system.They are not controlled by a computer Even if the pilots did act quickly enough to recover them from a runaway occurrence, it didn't work because the microprocessors which relay the instructions were down for the count. They are not made that way, you are making that up, there are no instructions to relay because there is no computer The signal cannot be transmitted if the line is dead. They do not need to relay a signal, they needed to pull a fuse to stop any electron flow to a motor or other non digital device which was driving the stabilizers.

.

Gordon, I apologise, I was not aware of the fact that you were a pilot.

-- Cherri (sams@brigadoon.com), February 09, 2000.

Jeeezuz! Bold off!

Gaaawd, Miss Einstein here can't even handle a little HTML without screwing it up! You're right Cherri, you're such a genius.

-- Hawk (flyin@high.again), February 09, 2000.

Hawk,

It must be sad being so ignorant, I didn't sit there for 28 years working on the same equipment, I have worked on the newest computers in existance before you ever saw a computer. You may get stuck with one thing, but I know more about digital computing then you ever will. Get a brain, there are a lot of other people here the same age as I am, including the moderators, bet Diane doesn't appreciate your reference to her age and what you think of women her age.

The advantage of being at the forefront of technology as it came along has given me a head start on anyone just starting out learning computers in the last 10 years.

I may be old enough to have changed your diaper, you act like you still need it done for you.

What a big baby, having tantrums when you don't get your way or if someone tells you you are wrong.

-- Cherri (sams@brigadoon.com), February 09, 2000.

That's cute Cherri, typical troll, trying to put words in mouth. I've got no problem with your age, or Diane's age. I do have a problem with the fact that you keep denying the fact that a servo motor can be controlled by a digital computer drive, especially after I have told this to you at least SIX TIMES! You're dense, OK?!! Look, if you want to keep believing that every servo motor is controlled by nothing but analog circuitry like the B-52, go right ahead, but don't tell me that the digital control doesn't exist, because I have already proven that it does. You really should get a job or something so you'd have something better to do than go around pestering people all day.

-- Hawk (flyin@high.again), February 09, 2000.

Hawk,

Just a few more comments. The horizontal stabilizer does not have any trim tabs. The stabilizer itself moves up or down to *trim* the airplane for whatever flight condition is required. It is set for a lot of nose up trim on takeoff and landing when the speeds are slower. As speed increases the stabilizer moves toward a neutral position and is near zero trim during cruise. Also, it moves very slowly.

You have seen the rudder, or ailerons, or elevators move quickly as the pilots do a pre-takeoff check. The stabilizer only moves due to a jackscrew system that is like a worm gear which slowly increases or decreases the angle of attack of its leading edge. It is powered by either a hydraulic motor or electric motor or both. There is a higher speed mode for it (but still slow) when the hydraulic motor is used and a much slower mode when the electric motor is used. The autopilot uses the electric motor to trim the stabilizer in most cases. The pilots can use the hydraulic motor by either moving an electric switch on the control yoke or a lever on the center pedestal between the pilots.

Computer control, where it exists, is not very sophisticated for setting the stabilizer trim. And either switches or circuit breakers are within easy reach to disable the system. Once disabled the stabilizer will remain where it was and not move any further. However, if it was allowed to go to full nose down trim it will create an impossible situation for the pilots. They can try to overcome the bad trim scenario by pulling back on the control yoke but the elevators can not deal with the forces if it goes to extremes.

I don't know that the elevator actuator mechanically failed but that's the way it seems now. The crew was maintaining some limited control until they heard that loud bang in the tail and then lost it. So this is my educated guess about it all based on what I have seen happen myself. I have had to deal with a jammed stabilizer a few times but never a runaway condition, except in the simulator. We used to practice stabilzer problems every year in the simulator. Believe me, you don't need to go to computer problems to figure out stabilizer failures. They have been happening for years, long before computers were even introduced into aircraft. The stabilizer control is basically a simple mechanical system that can go wrong for any number of component failure reasons. Most flight control failures are the result of mechanical breakage or hydraulic package problems and have nothing whatever to do with any computer inputs. Of course the newest fly-by-wire aircraft are computer controlled but the actual movement of the control surface is still hydraulic/mechanical. And even in fly-by-wire systems the stabilizer is a slow moving control and gives you warning that it is going wrong.

Now, if we get into modern fighter aircraft they have neither a separate stabilizer nor elevator but rather a stabilator which is one single surface that can move very quickly. But that is another story and there is no need to confuse the issue with that matter for now.

As far as the NTSB is concerned, they are usually pretty good at sifting through the data and explaining the causes of accidents. Occasionally, such as in TWA 800, or the recent Egypt Air crash, they cover up the truth (to the public) for high level political reasons. I don't think that is happening in this case.

-- Gordon (gpconnolly@aol.com), February 09, 2000.

Gordon,

I agree with you in your assessment of the probable cause of the crash. Heck, I live with someone that works on birds every day. He thinks that maybe the nut that holds the long screw (jackscrew?) might have come off. He said that during normal maintence, all that was probably done was to grease this assembly. Now, if it did forcefully come apart, that could have been the noise which was heard. Just a thought. He seems to think that they sould ground these planes to examine this assembly.

-- (agree-with@Gordon.now), February 09, 2000.

I do have a problem with the fact that you keep denying the fact that a servo motor can be controlled by a digital computer drive, especially after I have told this to you at least SIX TIMES!

I do not deny that a servo motor can be controlled by a digital computer, I am deying that they are used in the movement of the stabilizer of the MD80. And as for you telling me 6 times, so what? You are saying a lot of things things that are just guesses and some that are completly wrong. Why should the fact that you told me anything mean I should listen?

As for your constant referral to the B-52, once again, it was one of the early ones I worked on. The latest is the 767. You are being childish again, pretending the first equipment I worked on was also the last.

You should listen to Gordon

-- Cherri (sams@brigadoon.com), February 09, 2000.

Hawk, your timing pulses theory doesn't fly, literally.

Aircraft flight control surface trim servo motors are straight dc motors, not high-speed, digitally synchronized motors like you're referring to. I took a little search time and found that the ones you're using as your example would most likely be used in industrial robotics for high speed, high precision motion control. I thought those looked familiar, because they're newer versions of what I worked with on automated maufacturing systems built by Universal Instruments Corp.

I know that in the fly-by wire aircraft projects I'm currently working with at L------- M----- Control Systems (C-17, F18, V-22, AV- 8B, JAS-39, JSF), the flight controls don't use synchronous motors. These all use Analog to Digital Comparators to determine the position of the flight control surfaces and plain DC motors to move the surfaces. A/D systems can be put onto a circuit board in the Flight Control Computer. In fact most aircraft use two, two channel flight control computers to have four parallel control channels, from computer to motors.

Synchro motor systems are too heavy. They are high-power motors that require high-power amplifiers and controllers that just don't fit with the needs of aircraft designers. Adding extra boxes for the equipment needed for synchro systems is a definite no-no.

WW

-- Wildweasel (vtmldm@epix.net), February 09, 2000.

The Alaska Airlines Prez, interviewed at length by the local NBC affiliate, KING-TV, in Seattle this morning, said that he, himself, got into the flight simulator, and tried and tried and tried and tried to "crash" the flight by locking-up or messing with the settings on the various parts of the tail control .....and couldn't! It couldn't be done. There has to be an additional factor or cause. A neat guy. More than a CEO. A pilot and an air-savvy guy. Often dressed in his leather jacket he looks like a Howard Hughes or Smilin' Jack from the old funny-papers. Alaska Air has always been the pilots' airline, from it's old bush flying days in the North onward. They plan to get on top of this; to REALLY LEARN from this. These mavericks will be hard to manage. Ron ---- By John Prukop
-- OR (orwelliator@biosys.net), February 09, 2000.

Try again...

A Pilot Suggests 'Additional Factor' Involved In Crash

The Alaska Airlines Prez, interviewed at length by the local NBC affiliate, KING-TV, in Seattle this morning, said that he, himself, got into the flight simulator, and tried and tried and tried and tried to "crash" the flight by locking-up or messing with the settings on the various parts of the tail control .....and couldn't! It couldn't be done. There has to be an additional factor or cause. A neat guy. More than a CEO. A pilot and an air-savvy guy. Often dressed in his leather jacket he looks like a Howard Hughes or Smilin' Jack from the old funny-papers. Alaska Air has always been the pilots' airline, from it's old bush flying days in the North onward. They plan to get on top of this; to REALLY LEARN from this. These mavericks will be hard to manage. Ron ---- By John Prukop
-- OR (orwelliator@biosys.net), February 09, 2000.

OK, here's one more comment. The fact that some Alaska Airlines guy got into a simulator and couldn't duplicate the problem is not significant. First off, he would have to trim the stabilizer (at 31,000 feet) to full nose down. This would leave him with only elevator control. Then, he would have to put the plane in a dive that approached the Mach speed limit of the aircraft. At that point the forces on the elevator would be extreme, far beyond normal design parameters.

What the simulator *would* tell him was whether the plane could still be aerodynamically controlled, to a certain degree. It would not tell him if there was a loose or sheered bolt or some other structural defect in the tail section parts that supported the stabilizer and elevator mechanisms. A part that would hold up under "normal" stress but not under extreme forces and pressures. Simulators do not simulate total failure of a *critical* part such as elevator hydraulic packages or hinges or pivot points. They don't simulate things that are considered to be far outside original design parameters, such as an elevator actually breaking off the tail section.

Thus, the fact that he couldn't simulate that accident is not too important. Once they determine what actually failed they can go into the simulator software and duplicate that problem. In most cases where they do something like that (afterward) they discover that in fact the plane can not be controlled after all. Military test pilots push new aircraft to their extremes to find out just where the system will fail or become uncontrollable. Beyond a certain point *any* aircraft can become hopelessly out of control. Luckily for the military pilots they get an ejection seat for just such a situation. Once that MD-83 got into an inverted spin, with major tail control unit failure, and extreme negative "G" forces, it was all over.

-- Gordon (gpconnolly@aol.com), February 09, 2000.

I think you just made an excellent point Gordon, thank you. There is no way the simulator would have the exact same digital equipment that was on the real MD-80 becuase it doesn't even have a real stabilizer trim. It also would not have the same non-compliant microprocessors that failed so miserably on Flight 261. Good point.

-- Hawk (flyin@high.again), February 09, 2000.

WW,

Man you are dense. How many times do I have to spell this out for you? I did not say the the failure was in the servo motor, IT HAS NO MICROPROCESSORS! I said the the microprocessors in the digital servo drive unit ( a SEPERATE piece of equipment ) or in the autopilot is the place where the failure occured. When the transmission of the instructional command signal is corrupted, things do not function normally. Why is that so hard to grasp?? Sheeesh!

-- Hawk (flyin@high.again), February 09, 2000.

Hawk,

I'm going to go out on a limb and *speculate* about a plausible scenario of what happened to that flight. This is based on what information I have gathered together with personal experience.

First off, the crew is reported to have been flying the airplane by hand for a while earlier in the flight. Crews don't do that if all systems are working OK. The autopilot gives much better cruise performance than hand flying does. So I think the problem with the stabilizer trim was coming from the autopilot inputs. I have personally seen this happen numerous times in aircraft without any computer controls at all. What goes on is that the autopilot detects forces being applied to the elevator and then trims the stabilizer to remove those forces. Ideally, there will be little or no force being applied to the elevators while in autopilot cruise.

I think the crew saw the out-of-trim happening and disengaged the autopilot. For some reason, yet unclear, the stabilizer still ran itself to full nose down trim and the crew had to try to use all the elevator authority they had to counteract it. This would mean pulling full back on the elevator (control yoke) to stop the dive tendency.

Now, the elevators work together but are not physically tied together. The hydraulic system keeps both the left and right elevator working the same but if one half of the elevator system were to jam or fail the other half would still be available to continue control. That is, *if* the stabilizer was at a normal position in the first place, which it wasn't.

So, my scenario is that the crew had managed to horse that plane into a semi-controlled position after the first loss of altitude, but were using all the elevator input they had available. Something then broke under the strain on the right elevator which removed that from control and probably just left it riding there in line with the out of trim stabilizer. Now with only the left side of the elevator in a full up position it caused the airplane to start to twist to the left, for the same reason that an arrow spins due to the offset of the feathers at the back end. This is what created the rolling to the left and another dive since there wasn't enough elevator force now to keep the plane's nose up. The combination of the roll and dive put them inverted and totally out of control.

The simulator is not designed for such a scenario, usually, but they can go back to reprogram it that way to see what happens. In any case, no matter how I look at it, I just can't see any computer malfunction that would result in the final upset that transpired. The key to this whole thing is that loud bang in the tail section just before the final loss of control. That says mechanical failure, not computor problems.

-- Gordon (gpconnolly@aol.com), February 09, 2000.

instructional command signal? Where did you make that up from? There isn't any such thing. Aircraft functions are not all tied together and run from some computer. Some systems have absolutly no connection to others. You act like there is a computer that evcerything is connected to. You don't fly planes like you run data through a bank. Where is this "computer" that is supposed to run the stablizer located? In the tail? Under the passenger compartment? You do not know aircraft systems and you have absolutly no clue as to wheather that servo unit even exists in aircrafts. You did a search and found a piece of equipment and now are trying to say it not only is in the aircraft, but caused the crash. Bet the company that makes it doesn't appreciate the lies you are spreading. What if they end up getting sued by the families for the crash because of the mis-information you are spreading? There are laws against spreading lies against people and companies. Are you willing to answer to the company if your speculation causes their reputation harm?

-- Cherri (sams@brigadoon.com), February 09, 2000.

Gaaawd Cherri, for someone who says she knows electronics you sure are clueless. The digital servo drive unit uses its microprocessors to interpret the instructional signals relayed from the flight deck. The microprocessors then perform the calculations necessary to relay the appropriate pattern of timed electrical pulses to the servomotor.

Why is that so hard for you to grasp? I swear, this is like trying to teach 3 year old children. If you need more details about the digital servo drive, please contact Rockwell, the manufacturer.

-- Hawk (flyin@high.again), February 09, 2000.

Hawk,

I don't think that that I have ever seen a non-expert take unsubstantiated conjecture based on such little research and not only attempt to pass it off as fact, but then defend it against others who apparently have more industry knowledge than you.

Actually, I think that Gordon and Cherri work for the NTSB and are getting paid to throw you off of the trail.

If you don't have brains, you certainly have balls, I'll give you that.

At the same time, while I think some pretty goofy things go on here at TB2000, your assertions are pretty far out there. I don't see a whole lot of regulars here rushing to support you.

-- CJS (cjs@noemail.com), February 09, 2000.

Hawk,

There aren't any digital servo drive units because there are no synchronous servo motors. That means thre aren't any microprocessors in the trim system.

What there is, is a "trim up"/off/"trim down" switch wired straight from the control columns to the trim motor. It's as simple as that.

Don't try and invent things that aren't there, guy.

WW

-- Wildweasel (vtmldm@epix.net), February 09, 2000.

Hawk:

Listen to WW. Or better yet, just read more than just "There is no way to manually move the stabilizer" from the link you provided above:

The entire MD-80 horizontal stabilizer moves to trim the airplane. The stabilizer is hinged at the rear and driven by a jackscrew at the front. The jackscrew is normally held fixed by an electrically released brake.

A primary and alternate electric motor power the jackscrew. The primary motor moves the stabilizer at 0.33 deg./sec. and is controlled by thumb switches on the control wheel, or "suitcase handle" levers on the center pedestal. Each control wheel has two adjacent thumb switches that are moved in unison. One applies power to the motor and the other releases the brake. The suitcase handles have the same logic, but they pull cables that activate electrical switches in the tail.

The alternate motor moves the stabilizer at 0.1 deg./sec. and is commanded by the autopilot, or by a pair of switches aft of the throttles. Full stabilizer motion is 2.1 deg. in the airplane nose- down (stabilizer nose-up) direction to 12.2 deg. nose-up. Normal stabilizer motion cannot be detected in the cockpit except for the motion of a stabilizer position indicator on the pedestal. Every 0.5 deg. of motion is annunciated by a tone. Alaska has an option so that when the autopilot is on, a voice says "stabilizer motion" if it moves more than 2 deg. in 30 sec. If the stabilizer is not keeping up with trim demands, an "out of trim" light illuminates.

The procedure to stop runaway trim motion is to first disconnect the autopilot, which should stop any alternate trim commands it is sending. Then a red guarded Stab Trim switch at the back of the pedestal is set to "Stop," ; removing power from the primary system, which clamps the brake. If the trim then stops, the pilot pulls the circuit breakers for the primary system and continues flight using the alternate trim to reposition the tail.

If the trim is still moving, the pilot returns the Stab Trim switch to " Norm," reactivating the primary system. He then uses this system to overpower the slower alternate trim and move the stabilizer to the desired position. Then he pulls the alternate trim circuit breakers and continues flight with primary trim. Pilots must memorize the runaway trim procedure because a rapid response is required.

Runaway trim requires a dual failure, usually caused by shorted switches or stuck relays, a Boeing engineer said.

Got all that? If not, it says the same thing that WW does - there are no servocontrollers or servo motors involved, just simple electrical motors with forward and reverse switches. Read the last sentence again "usually caused by shorted switches or stuck relays". Fly by wire controls do not use relays and switches, they are all digital.

Now, can you finally admit that you have blown this way out of proportion?

-- My Full Name (My@email.address), February 09, 2000.

From recent news stories, it appears that they have found the jackscrew (with stripped threads) from the crash, and are sending it to a lab to see if the threads were stripped prior to or after the crash.

Hawk, I don't see what the NTSB would have to gain by concealing evidence in this particular crash. The only result of doing this would be more problems of the same nature, whatever that may be. By the way, if the scenario was occuring as you say it was, with the thousands of airplanes taking off and landing everyday, wouldn't we see more crashes of planes with this Rockwell system that you know so much about?

One more thing-

The world doesn't own Ed Yourdon or the forumites here squat. The problem was exaggerated on this forum, fueled by fear, uncertainty, and doubt that was generated at times by irresponsible postings such as yours.

-- CJS (cjs@noemail.com), February 09, 2000.

The NTSB put up photos of the jackscrew portion of the trim actuator.

NTSB photos

Funny, but it doesn't look anything like Chicken-not-a-Hawk's photo. Guess it's "not the exact same model"

-- Mikey2k (mikey2k@he.wont.eat.it), February 09, 2000.

Jeeeezuz, no wonder you can't figure it out Mikey! That's not the digital drive unit for controlling the servomotor, that's the jackscrew! Now I see why you're having such difficulty understanding what happened, you wouldn't know the difference between a lawnmower and a tree. I've never in my life seen anyone as retarded as the polyannas on this forum. Wheeeeeewwwweeeyyy!

-- Hawk (flyin@high.again), February 09, 2000.

The reason the NTSB photo doesn't show the digital drive unit for controlling the servomotor? There isn't one on the MD-83.

No, Chicken-not-a-Hawk, I had the trim actuator figured out long ago. What I'm trying to figure out is the reason for your idiocy -- maybe your mother shoved you out the the roost when you were just a chick and you fell on your head.

Chicken-not-a-Hawk, you don't even have enough intelligence to be retarded.

-- Mikey2k (mikey2k@he.wont.eat.it), February 09, 2000.

I don't think Hawk really believes what he is saying. I think he just wanted to get a rise out of people. Nobody is this stupid.

-- CJS (cjs@noemail.com), February 09, 2000.

Hey Mikey, he likes it! The Life boy!! LOL!

"The reason the NTSB photo doesn't show the digital drive unit for controlling the servomotor? There isn't one on the MD-83."

You moron, they don't stick computers on the tail section dimwit. It's up in the forward section near the flight deck. The only thing running back to the servomotors are the wires carrying the electrical pulses, which are normally perfectly timed and synchronized until the microprocessors reference the real-time clock. Then they go kapuey because they're not compliant, and the whole damn system locks up. Man, some people just don't get it.

-- Hawk (flyin@high.again), February 09, 2000.

Read my post again, Chicken-not-a-hawk. I didn't say that your date- dependent was in the tail. I said it's NOWHERE on an MD-83.

Only true statement you made was that some people just don't get it. You and jeffDD sure don't.

So Chicken, when are you going to post the specific Model Numbers and Part Numbers of the non-compliant equipment you allege so that the hordes of press people monitoring this forum can investigate the facts and prevent further needless deaths? After all, since you're posting anonymously, the NTSB won't be able to send the CIA after you. A couple of layers of aluminum foil wouldn't hurt either.

-- Mikey2k (mikey2k@he.wont.eat.it), February 09, 2000.

Mickey, you put a link to a picture of the jackscrew and then said it doesn't look like my picture of the digital drive.

"Funny, but it doesn't look anything like Chicken-not-a-Hawk's photo."

Of course not you imbecile, the digital drive unit is not located anywhere near the tail section in your picture. If you have so much experience with these planes why don't you show us blueprints you moron. Answer: because you don't know jack about airplanes except little radio controlled toys.

-- Hawk (flyin@high.again), February 10, 2000.

Hey birdbrain, you've been asked for specifics. Do you give them?

NO!!!!!!!! Just more inane questions.

Tell us about YOUR aviation background. Hah! The only hawk about you is the phlehm you've spewed on this forum.

-- Mikey2k (mikey2k@he.wont.eat.it), February 10, 2000.

Breaking news from ABC

check out abcnews.go.com/sections/us/DailyNews/alaskacrash000210.html

-- (Sheeple@Greener.Pastures), February 10, 2000.

Hee, hee, hee.

Hawk, gotta love you. You are always good for a laugh. Gotta go now, my sides hurt too much to read any mroe of this.

-- Paul Neuhardt (neuhardt@ultranet.com), February 10, 2000.