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Engineering Disasters: Cracked Fitting Brings Down DC-10

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Charles Murray
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Sad memory
Charles Murray   11/19/2014 7:04:08 PM
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Unfortunately, I remember the DC-10 crash all too well. I lived in the city of Chicago at the time, and could see the smoke from about seven or eight miles away. I know people who worked in downtown high rises (approximately 40 floors up), and they could see the smoke from downtown Chicago, which is about 15 miles from O'Hare.

Jennifer Campbell
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Re: Sad memory
Jennifer Campbell   11/19/2014 9:46:18 PM
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Even though it's just a simulation, that video is terrifying and difficult to watch. Thanks for sharing, Chuck. I was 5 at the time, so luckily I was shielded from all the disasters in the world.

patb2009
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Re: Sad memory
patb2009   11/20/2014 1:15:49 AM
I suspect the Pylon was not designed for easy maintenance.

To me, an engine change should not require pulling the pylon too.

That said, the Operators got creative and it bit them.

 

If they wanted  a new procedure, either they should have certified the procedure

gotten a TSO and approved it, or got mcDac out there and had them approve it.

Steve Heckman
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Re: Sad memory
Steve Heckman   11/20/2014 8:18:13 AM
Part of the problem is many enginersd lack "hands on" experience. How many aerospace engineers have worked as an aircraft mechanic? Performing real maintenance, not just a team-based senior project? I'm glad our facility is not union, I get to build all my own prototypes and production fixtures, which gives me incredable insight on the process. Given how traditional organization work, it simply is not possible for a normal engineer to forsee such abuses in the field.

joe215
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Re: Sad memory
joe215   11/20/2014 9:18:10 AM
I find this a problem all over the country. little or no pratical experiance.  They are freshout of school and dumped into a job and to apply the education they leared which is most likely book and not pratical .  They should be given a job working with the hardware they are desiging as a learning tool before given important task like aircraft or spacecraft.

Quality should be envolved all through the design and human engineering along with system engineering practices should be used in reviewing the drawings and the drawings shall be used to review the work orders to build the items and also to test the items.

 

I believe uppermanagement and their cost saving ideas have just backfired.

Lets learn from the mistakes and go back to square one to get it right the first time.

bronorb
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Re: Sad memory
bronorb   11/20/2014 9:30:04 AM
Mr. Heckman,

Are you saying that if you were working in the engineering department at a facility that had a union on the shop floor, you would not be able to enter the shop and build your own fixtures? I suppose they would stop you at the door so that you could not observe anything that they were doing either.

Just curious. Have you ever worked in such a place or is this just conjecture on your part?

Steve Heckman
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Re: Sad memory
Steve Heckman   11/20/2014 9:48:26 AM
My intent was not to raise Union vs non-union, but to set the record straight, I have been a Union member, and yes, it CAN get that bad. Please do not focus on that point: my theme is hands-on engineers will most likely be better engineerrs in anticipating what could go wrong.

There is some value in watching machinists work... as greenhorn engineer I picked up a lot by watching some of our older machinists build my parts. But I was also allowed to operate many of the machines in our tool room. 

I will also add that you haven't lived until you replace a 30-pin connector in a F-4 cockpit while literally standing on your head (in the winter). I learned more about "design for maintenance" by performing maintenance than any test book could ever provide. The Air Force in the late 80's had a "Blue Too" program in an attempt to get engineers field experience, to make future designs more friendly to maintain (The F-16 had an avionics bay with swing down doors, the F-4 had black boxes under a number panels with 60+ screws each).

HarryB
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Re: Sad memory
HarryB   11/20/2014 9:52:02 AM
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To answer your question I have in indeed been in a "union" auto plant where I (the engineer) was not permitted to touch the touch the equipment I built for maintaining the system (a master workstation consisting of a networked computer).  Two union employees accosted me and demanded to know what I was doing with "their" equipment (typing in a command)... The insisted that only they could touch the equipment, it was their JOB and they would file a grievance if I continued. I gave them the keyboard and dictated what to type... I had to show them where the letters were and which key was "enter".   I should have known by the graffiti in the rest room. One said "UAW - usually avoids work" and that was crossed out and scrwaled beneath was "Salary - stupid @sshole liars always rip you".  A common expression was "Go scrub" which I leared was short for "go scrub your nuts with a wire brush" This was in the late '90s... things may have improved since then.

Other Union shops have had members who were more than happy to assist in any way possible... overall my experience with them is quite favorable.

LloydP
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Re: Sad memory
LloydP   11/26/2014 8:55:33 PM
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I have worked, as an engineer, with union and non-union shops throughout my career. (I am now retired) The rules of engagement in my experience depended on my relationship with the trades. I worked in a facility represented by the United Steelworkers Union where I could do almost anything, as long as a union tradesman was assigned to me. I worked in another USW plant where I could use a keyboard, or adjust anything that could be changed with a screwdriver that had a pocket clip. Anything more extensive required a tradesman to do the work under my instruction.

I worked in a UAW represented plant where I could do nothing other than instruct the tradesman what to do, one slow step at a time.

I worked in another plant of the same company, in the same town, where I could do almost anything, as long as the appropriate tradesman was nearby. We even joked about it. My job was to trick them into doing work for me. Their job was to trick me into doing something that they could file a grievance. They never did, because I had a good relation with the trades, and we both understood the rules. Most of the time, at that plant, the trades were eager to work with me, because I was willing to explain what we were doing, and why.

Daniel I
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Re: Sad memory
Daniel I   11/24/2014 6:43:42 PM
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no need to politicise a very sad event by mentioning unionisation. i am sure in the days of those 'dark satanic mills' - pre-unionisation - there were equally sad deaths. the issue of engineers not understanding shop floor requirements has more to do with the ways engineers are being trained than anything to do with unionisation.

wbswenberg
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Re: Sad memory
wbswenberg   11/24/2014 7:12:35 PM
I had joined the B compnay in 77.  We talked aout the failure alot.  One of the things I have found out in my 37 years of expeience is that the airlines will use and maintain the airplane as they damn well please.  Hopefully thier internal procedures are close to the manufacturers procedures.  

Elizabeth M
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Re: Sad memory
Elizabeth M   11/20/2014 6:40:37 AM
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I was only a child at the time of the crash but remember reading and hearing about it later. I try not to think about this type of thing when I'm flying, but of course airline crashes like this are a traveler's worst nightmare. Thanks for bringing to light what happened to cause this horrific incident.

jpratch
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Gold
Re: Sad memory
jpratch   11/20/2014 8:28:47 AM
At the time this happened, I worked for a Navy Headquarters organization responsible for extending the time between overhauls for Missile Submarines. One of our engineers discovered that bolts on the stern planes were not being tightened properly and could loosen and jam the submarine in a "dive". A few weeks after the Chicago crash, he was briefing those responsible for approving the expensive inspections needed. When asked to estimate the risk and how likely one of the boats might get stuck in a dive, he responded "... about as likely as an engine coming off a DC-10". The inspections were authorized and loose bolts were found on several ships. 

Battar
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Re: Sad memory
Battar   11/20/2014 9:18:14 AM
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Completely off topic here, but do you know who O'Hare airport is named after (or who his fathers' employer was?) It IS Chicago, after all...

patb2009
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Re: Sad memory
patb2009   11/20/2014 9:27:54 AM
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butch o hare flew combat in WW@2.0

Charles Murray
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Re: Sad memory
Charles Murray   11/20/2014 5:23:18 PM
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In honor of Butch O'Hare, there's a nice F4F Wildcat on display in Terminal 2 at O'Hare, Battar.

Charles Murray
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Re: Sad memory
Charles Murray   11/20/2014 5:31:05 PM
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Battar, nice story earlier this year by NPR about Butch O'Hare. http://www.npr.org/2014/05/24/315259241/butch-ohare-the-heroic-namesake-of-chicagos-airport

rsquared
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Re: Sad memory
rsquared   11/20/2014 10:05:42 AM
Biggest lessons to be learned from the DC10 Crash in Chicago were

1) Design Reduancy into systems,

2) Design seperation of critical systems,

3) Develop an Inspection plan to detect damage and fatigue cracks,

4) Design Damage tolerance into systems and structure 

5) follow processes procedures.

Although the official cause was ruled not following maintenance procedure. The maintenance procedure called for removing the engine from pylon before removing the pylon from the wing.   The engine is cantilevered off the front of the engine leading to very large loads on the front pylon attach bolts to the wing.   The revised procedure was to remove the engine and pylon from the wing as a single unit.   Greatly reducing the time required to remove the engine and pylon from the airplane during maintenance.  This change in procedure over loaded of the pylon attach bolts initiating damage to the pylon fitting and bolts initiating damage that developed into fatigue cracks that lead to the seperation of the engine and pylon from the airplane.   This damage and resulting fatigue cracks were easily detected by visually inspectiing the fittings.   Several other airplanes were found to have damage and fatigue cracks at this location.    Seperation of the engine and pylon from the airplane damaged the hydraullic lines which power in wing slats.   Proper design of the systems which include check valves, redundancy and seperation of the systems would have prevented the slats from retracting and possibly allow the plane to continue to fly and return to the airport.

William K.
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Re: Sad memory, and what was learned.
William K.   11/20/2014 6:39:28 PM
@R2, the one other lesson is that for all systems that may evenutally need to be serviced, design in a satisfactory service procedure. Satisfactory, in this case means that it does not overstress any parts, and also that it is not likely to be circumvented because of being too complex or difficult.

Designing in a set of lifting pads for use with a lifting frame would have prevented the overstressing of the pylon, and probably made the taskeasier as well. But it would have required additional design effort. 

And I wonder how the engines were installed when the DC10 was built. Does anybody know?

tekochip
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Re: Sad memory, and what was learned.
tekochip   11/21/2014 9:06:53 AM
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This is why procedures are to be followed.  My own aircraft is in the shop now for a crack at the horizontal stabilizer.  The crack is caused by ground handling crews turning the aircraft by pushing down on the stab to get the nose gear off the ground.  The POH doesn't even hint at this practice, but I have seen ground crews do it time and time again.

AnandY
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Re: Sad memory, and what was learned.
AnandY   11/23/2014 4:54:43 AM
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Having an "after every crucial step" check-up of the hydraulics, electricals and wings should be done when maintenance teams flock the aircraft. Although there are supervising officers when the aeroplane is worked upon, still many things can be missed. We can't say for sure if MH 370 had an electronic error or a pilot error, but whatever it was, engineers were to equally blame.

patb2009
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Re: Sad memory, and what was learned.
patb2009   11/23/2014 3:00:00 PM
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tekochip

 

Good thing the crack was spotted,  if it were internal, that would likely be

a critical failure in flight.

 

I've seen dozens of ground crews adjust air craft by yanking on the horizontal stab,

makes me wonder if a T-Tail is a better design solely to avoid ground crew malfunction.

 

 

ab3a
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Re: Sad memory, and what was learned.
ab3a   11/24/2014 3:31:42 PM
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Just out of curiousity Tek, how did you find that crack?  Was it during your annual inspection? 

tekochip
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Re: Sad memory, and what was learned.
tekochip   11/24/2014 7:14:45 PM
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ab3a, yes, it was during the annual, and is part of the normal inspection.  The cracks were exactly like all the ones you see on the web, sitting at about 10 o'clock and 4 o'clock.  There wasn't any buckling yet.

a.saji
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Re: Sad memory, and what was learned.
a.saji   11/28/2014 12:44:11 AM
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@tekochip: Does it happen regularly or is it a one-time thing ?

tekochip
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Re: Sad memory, and what was learned.
tekochip   11/28/2014 10:42:39 AM
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I've done some research and haven't seen any repeat offenders, but then again the aircraft is 40 years old, maybe it'll take 40 years for the repairs to fail.

bob from maine
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Re: Sad memory, and what was learned.
bob from maine   11/24/2014 4:42:56 PM
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Gosh, you mean you DON'T push down on the horiz stab to turn the aircraft 180 degrees inside a hanger? I don't think I've seen it done in any other way, either that or put the fat guy in the rearmost seat to lighten the nose! We did sometimes use dollies for the bigger aircraft.

 

tekochip
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Re: Sad memory, and what was learned.
tekochip   11/24/2014 7:25:00 PM
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Bob , no, not on the stab.  I've seen guys do it, and thought it was too easy to dent the skin if you missed the ribs.  I used to move the plane around by pushing down on the former near the vertical stabilizer, but my wallet changed that behavior when I wore out a new pair of Goodyears on the mains.  Those tires may be small but they sure are pricey.

a.saji
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Re: Sad memory, and what was learned.
a.saji   11/27/2014 2:19:47 AM
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@tekochip: That's some valuable piece of information mate. I also feel that the price is mapped not for the size or the thickness, its for the output and its quality

AnandY
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Re: Sad memory
AnandY   11/23/2014 4:59:18 AM
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There already are many steps followed, I actually like your idea of having a separate design for critical life support systems. Maybe if the plane passenger compartments could have heat resistant rubberized walls then the impact of the fall can be taken by the aeroplane, and since most of the deaths occur after the aeroplane breaks apart (sudden pressure changes makes people unconscious so they wouldn't feel the moment of death) deaths could be minimized since the aeroplane isn't going to break apart.

kenish
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Re: Sad memory
kenish   11/23/2014 11:04:02 PM
I was in college and my friend and I were traveling to LA on Memorial Day weekend.  We were supposed to take AA191 but they put us on an earlier flight.  Fate is a strange thing.

Tragically the pilots flew by the book, but the plane would have been controllable if they flew only 10 knots faster.  When the engine separated the slats on the LH wing retracted since the DC-10 had no hydraulic fuses or a brake system to stop assymetrical conditions (common on other aircraft).  A control surface indicator in the cockpit was inop because it was powered by generators on the left engine with no backup.  The pilot had no idea the slats on one wing failed and slowed to "best rate-of-climb- slats extended" speed, 10 knots slower than "slats retracted".  One wing stalled and the plane rolled.

An aside- a few months later the same thing happened to a 747 on takeoff.  It returned to the airport safely.  There have been several other major DC-xx accidents where a serious but manageable failure set off a series of system failures that brought the plane down. 

watsonm05
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Engineers and real-world experience
watsonm05   11/20/2014 8:40:29 AM
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The comment about the engineers not having real world experience reminded me of what one of my engineering bosses told me.

He was a mechanical engineer and his first project in the company was to design a support for a liquid storage tank that was being positioned some 15 feet in the air.  When he presented his design to the senior engineers for review they promptly tore it up and instructed him to redesign it.  He was told "You designed it for the wrong thing.  You designed it to hold the tank safely.  You really need to design it to withstand its legs being hit by a forklift because that is guaranteed to happen."  I think he adopted his motto after that: "If it doesn't have to fly, make it out of steel and lots of it!"

 

joe215
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Re: Engineers and real-world experience
joe215   11/20/2014 9:19:38 AM
He gave you some good advise

this should be a main stay in the education.

RogueMoon
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maintenance crews took a short cut
RogueMoon   11/20/2014 9:00:01 AM
I think we're all missing the larger issue here.  The maintenance crew took a shortcut and didn't follow the procedure to detach the engine and pylon separately.  Engineers, nor anyone for that matter, can not forsee all consequence of every permutation of someone not following the instructions.  It's literally an impossible task.   Did the shop ever consider engineering had a good reason for making the procedure in that way?  Why does engineering have to compensate for every whim of the maintenance crew?

We have drilled our shop to follow procedures without deviation, period!  If they have an issue, they stop work and bring it forward, otherwise follow the darn instructions!   If the instructions are deficient, it's the engineer's fault.  If the shop takes a short cut and doesn't follow procedure, it's entirely their fault. 

ChasChas
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nature of the beast
ChasChas   11/20/2014 9:45:01 AM
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Personnel elevators have safety factor of 12 by code.

If comercial aircraft had a SF of 12, they would be so heavy they would barely be useful.

You have to admire what aerospace engineers can do with so little to work with.

The maintainance people have special training to work on these critically stressed machines.

No unauthorized procedures can be allowed.

 

Wayne Eleazer
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Was There a Real Root Cause?
Wayne Eleazer   11/20/2014 10:09:54 AM
In October 1975, 18 months after I graduated with a Mechanical Engineering degree, I was rushed off to Myrtle Beach Air Force Base to look into a problem with their A-7D aircraft.

Air Force Logistics Command had just discovered that the bleed air ducts on the A-7D fleet had mysterious wrinkles in them, some quite large.  Since the ducts carried high pressure very hot bleed air out of the TF-41 engine the fear was that they would rupture and the hot air would damage the airplane.  By the way, there is a B-52 on display at the Oklahoma City Fairgrounds that had just that occur and it rendered the airplane useless for anything but a display item.  

Once I got to the base I found that various theories abounded that blamed the manufacturing process.  But then they let me observe a USAF maintenance team removing and reinstalling an engine and it all became clear.

The maintenance crews had devised a shortcut to aid in the engine removal and installation.  There was very limited access to the ducts and they normally had to come off to remove the engine.  But they had found that if you took safety wire and looped around the ducts you could pull them over against the fuselage skin far enough to clear the engine igniter box and thereby significantly ease the task.

The time-saving process wrinkled the ducts, subjecting them to forces similar to someone having his arm twisted behind his back.  The ducts were wrapped with a thick stainless steel foil for insulation and so the damage was not obvious.

However, at that time the A-7D was suffering from serious engine problems and the engines had to be removed and inspected frequently.  Ultimately, the problem was caused by those engine problems and the decision to require such inspections without considering the possible problems that could occur.

Working from my lofty height of an engineering degree, 18 months actual experience, my 2nd Lt rank  - and an urgent official message from my Colonel saying, "Never mind about his age and his rank!  He is a fully qualified engineer and representative of this Air Logistics Center  and if you want to fly your airplanes you will do just what he tells you to!" – I inspected and found enough flightworthy ducts to get half their airplanes back in the air.  The number of ducts sets I Okayed just happened to match the number of airplanes they had functioning engines for - and none of them crashed as result.

But whenever I think of that DC-10 mishap, I wonder what requirements might have been imposed on the mechanics that prompted that disastrous innovation.               

bobjengr
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Re: Was There a Real Root Cause?
bobjengr   11/25/2014 5:58:34 PM
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Wayne--I know the feeling.  I graduated in 1961 and took my commission as a second Lieutenant then assigned to the Air Force Logistics Command. The group I was in supported the Titan II ICBM, specifically the thrust chamber and turbopump assemblies.  I went through the training program during the months of January and February then went TDY to Davis-Monthan AFB the first of March.  Cracked rotor blades on turbopump rotors.  (Going was not my idea at all.) It was excellent experience but I was a bundle of nerves during the entire two weeks of the investigation.  Really nervous when I gave a report out the commanding officer.  Those two weeks was worth more than reading all of the manuals available but it was sink or swim.  

Excellent post Charles.    

jaydubau
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Started Working at McDonnell-Douglas That Summer
jaydubau   11/24/2014 5:09:20 PM
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With my newly minted Mechanical Engineering degree from the University of California-Berkeley, I started working at Douglas Aircraft in Long Beach. They, of course, built the DC-10's. I went into the pilot controls section of the mechanical engineering group.

Needless to say, that incident was THE topic of conversation. As part of our orientation week for engineering new hires, we were briefed on what ACTUALLY happened. Yes, there are many "What if's" and "If only's.". The first officer was at the controls. You can't physically see the engines from the cockpit, so he relied on his instruments. As mentioned, he went under the assumption that the engine lost power and proceeded accordingly. With the leading edge slats driven by a "bull wheel" and hydraulic cylinders, the aerodynamics forced them to retract. That wing then stalled and the plane rolled.

The plane was flyable. The pilot wasn't aware of the pending stall. The power for the stick shaker/pusher was also provided by the #1 engine. As an extra cost option, the stall system was offered powered by both the #1 and #3 engines. Such a shame....

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