Boeing 737 MAX - software wouldn't fix faulty airframe

jpanhalt

Joined Jan 18, 2008
11,088
That ship then and Iran now are completely at fault for killing those people, that's not the same situation at Boeing.
I remember that incident well The US paid $61.8 million compensation to the victims' families. Let's see how much Iran pays out.

My point, though, was different. It is often said that Nixon's downfall was his desire to document everything. The Oval Office recordings and notes did him in. Absent those, there might have been a lot of partisan palaver, but nothing would have come of it.

In this century, e-mails seem to have been at the source of every scandal large and small. Enron, Auction Rate Securities (2008), Mueller stuff, and so forth. My reference to e-mails was meant as hyperbole. They present a risk that far too many people ignore. Like Nixon's recordings, after awhile, he forgot it was being done and let his guard down. The same is true for the salacious stuff Mueller uncovered. There was no intent on my part whatsoever to make light of either what just happened or the Vincennes incident.
 

Rich2

Joined Mar 3, 2014
241
I wonder if passengers will avoid it. It certainly looks odd with the engines forward on the wings, what a lash up.

Someone said "if it looks right it will fly"... Well it does fly I suppose.
 

nsaspook

Joined Aug 27, 2009
9,488
I wonder if passengers will avoid it. It certainly looks odd with the engines forward on the wings, what a lash up.

Someone said "if it looks right it will fly"... Well it does fly I suppose.
Perfectly normal configuration for a modern airplane.

 

Tonyr1084

Joined Sep 24, 2015
6,861
By Eric M. Johnson and David Shepardson

SEATTLE/WASHINGTON (Reuters) - Boeing Co <BA.N> told the U.S. Federal Aviation Administration it does not believe it needs to separate or move wiring bundles on its grounded 737 MAX jetliner that regulators have warned could short circuit with catastrophic consequences, people familiar with the matter said on Friday.

The FAA confirmed Friday it had received a proposal from the planemaker regarding the wiring issue.

The FAA will "rigorously evaluate Boeing's proposal to address a recently discovered wiring issue with the 737 MAX. The manufacturer must demonstrate compliance with all certification standards," the agency said in a statement.

The U.S. planemaker and FAA first said in early January they were reviewing a wiring issue that could potentially cause a short circuit on the 737 MAX, and under certain circumstances lead to a crash if pilots did not react in time.

A Boeing spokesman referred all questions on wiring to the FAA, saying the agency would make the final decision and that the company is answering questions from the FAA.

Boeing's 737 MAX was grounded worldwide last March after two crashes in Indonesia and Ethiopia killed 346 people within five months.

Boeing has spent months updating the stall-prevention software known as MCAS linked to both crashes, but fresh issues have surfaced, complicating regulators' efforts to re-approve the plane.

Given intense scrutiny of the 737 MAX, Boeing is sure to face questions about whether the MCAS system makes it harder for pilots to react in the event of a short circuit.

There are more than a dozen different locations on the 737 MAX where wiring bundles may be too close together. Most of the locations are under the cockpit in an electrical bay.

If the bundles pose a potential hazard, regulations would typically require separating the bundles or adding a physical barrier.

Boeing has noted in talks with the FAA that the same wiring bundles are in the 737 NG, which has been in service since 1997 and logged 205 million flight hours without any wiring issues.

New safety rules on wiring were adopted in the aftermath of the 1998 Swiss Air 111 crash.

A company official told Reuters last month Boeing had been working on a design that would separate the wiring bundles, if necessary. Moving the bundles could pose further delays to the return of the MAX, however, and Reuters reported Thursday that a key certification test flight was not expected until April or later.

Three U.S. airlines this week pushed back the resumption of 737 MAX flights from June until August or later. Boeing has estimated U.S. officials would lift a safety ban on the aircraft around mid-year.

It is unclear whether the European Union Aviation Safety Agency will demand the MAX wiring bundles be separated. A spokeswoman for the agency on Thursday said regulators were "waiting for additional information from Boeing."

(Reporting by Eric M. Johnson in Seattle and David Shepardson in Washington; Editing by Chris Reese and Tom Brown)

[end of article]


Two things stand out here. Many years of safe operation with no accidents - and two catastrophic accidents within months. What changed? Well, I don't know. But it's possible some bean counter discovered a wire vendor that reduces cost by offering cheaper wires. Big business is always looking to reduce cost. So just because there has been decades of safe operation with a particular wire configuration doesn't mean nothing has changed. Something clearly has. It could also be a wire harness operator who takes shortcuts in the assembly process of these complex cable runs, leading to a compromised harness. Dragging cables on the ground; or walking (stepping) on wires. I've worked with wire harness operators who have no idea how to crimp connectors and they've been doing it for many years. You can't ignore the human factor in all this. Not saying that's what happened, just something that needs consideration.

I recall a C-130 wire stringer who's job it was to apply a shielding of shrink sleeving to fuel pump wiring. Standard practice was to apply a three foot length of shrink sleeving over the wires, then add a second length to reach the end of the harness. This particular operator was shrinking the sleeving but at the same time stretching it the full length of the harness. That meant the harness had a single length of sleeving stretched (probably) half the thickness originally intended. Plain and simple - people do dumb chit for the sake of saving some time and effort.
 

nsaspook

Joined Aug 27, 2009
9,488
By Eric M. Johnson and David Shepardson

[end of article]


Two things stand out here. Many years of safe operation with no accidents - and two catastrophic accidents within months. What changed? Well, I don't know. But it's possible some bean counter discovered a wire vendor that reduces cost by offering cheaper wires. Big business is always looking to reduce cost. So just because there has been decades of safe operation with a particular wire configuration doesn't mean nothing has changed. Something clearly has. It could also be a wire harness operator who takes shortcuts in the assembly process of these complex cable runs, leading to a compromised harness. Dragging cables on the ground; or walking (stepping) on wires. I've worked with wire harness operators who have no idea how to crimp connectors and they've been doing it for many years. You can't ignore the human factor in all this. Not saying that's what happened, just something that needs consideration.

I recall a C-130 wire stringer who's job it was to apply a shielding of shrink sleeving to fuel pump wiring. Standard practice was to apply a three foot length of shrink sleeving over the wires, then add a second length to reach the end of the harness. This particular operator was shrinking the sleeving but at the same time stretching it the full length of the harness. That meant the harness had a single length of sleeving stretched (probably) half the thickness originally intended. Plain and simple - people do dumb chit for the sake of saving some time and effort.
The wiring seems to be a non-issue with recent (or any know 737 crash.) Reworking the bundles IMO seems more of a risk for future wiring problems than just leaving them alone.
 

Tonyr1084

Joined Sep 24, 2015
6,861
Reworking the bundles IMO seems more of a risk for future wiring problems than just leaving them alone.
I would agree with that statement. All I'm suggesting is that there may be human factors in this. Perhaps it's a new employee who doesn't fully understand the potential harm from not following procedure. OR perhaps corporate profiteering may be behind it. Or a part of it. Or a number of combining factors.

To say the least - it's a problem.
 
The 737 Max wiring bundles have a hot power wire together with command wires. “If a hot short occurs between the power wire and either the up or down command wire, the stabilizer can go to the full nose-up or nose-down position”.
SwissAir111 disaster occurred due to short circuits in a wiring harness leading to loss of control. Regulations were changed in 2009. The FAA and Boeing missed all of it on the 737 Max. design/certification. What a mess.

We all know Boeing wants absolutely no hardware changes to the almost 800 planes out there. That would cost a fortune and take a very long time to do. Management loves a software fix but it ain't happening here. Do we cover for the corruption and dismiss the wiring concern.

Has Boeing just been lucky or are safety standards just silly and not necessary?
205 million flight hours? Several hundred people are dead and Starliner $400M launch a hilarious failure.

source: https://www.seattletimes.com/busine...a-over-737-max-wiring-flaw-that-boeing-missed
 

jpanhalt

Joined Jan 18, 2008
11,088
I don't know the details of the Swiss Air crash, but the Wikipedia description points to several causes of complete electrical failure and fire (https://en.wikipedia.org/wiki/Swissair_Flight_111).

Extending the logic of not having a power and elevator control wire in the same bundle, wouldn't that extend to all signal wires? An out of control rudder contributed to the Pittsburgh crash in the mid-1990's. And then, what if a control wire shorts against the airframe? Any insulation can fail given enough abrasion. Maybe a better solution is software. That is, ignore signals caused by shorts to power or to ground.
 

Ylli

Joined Nov 13, 2015
1,057
Could always maintain a mechanical linkage between the controls and the control surfaces. And *always* allow the pilot to override any automation simply by mechanically flying the airplane. After all, that is what a pilot is trained to do right? If not, we have a bigger problem
 

jpanhalt

Joined Jan 18, 2008
11,088
Could always maintain a mechanical linkage between the controls and the control surfaces. And *always* allow the pilot to override any automation simply by mechanically flying the airplane. After all, that is what a pilot is trained to do right? If not, we have a bigger problem
Mechanical linkages fail too and require a lot of maintenance. Moreover, it is hard to build in redundancy for a broken cable..
 

Ylli

Joined Nov 13, 2015
1,057
True, but I see and read of so many accidents that occur because the pilot either did not know how or was unable to fly the airplane. If we put qualified people in the left seat and gave them the ability to override any automation malfunction, I think we would have fewer accidents.
 

nsaspook

Joined Aug 27, 2009
9,488
Could always maintain a mechanical linkage between the controls and the control surfaces. And *always* allow the pilot to override any automation simply by mechanically flying the airplane. After all, that is what a pilot is trained to do right? If not, we have a bigger problem
The 737-MAX has a mechanical linkage to the trim control surfaces. The problem is at extreme angles of attract and speed the aerodynamic forces exceed human capabilities so the trim wheel was useless as a last ditch method of airplane control.
 

jpanhalt

Joined Jan 18, 2008
11,088
I have never flown anything much bigger than 8000 #. I do know some scheduled air carrier and 135 jet pilots. I don't think mechanical vs. wire is an issue with them. They fly both.

An awful lot of accidents occur with aircraft that do not have fly by wire. The recent Kobe Bryant crash was not due to a mechanical failure of the helicopter, so far as we know today.
 

SamR

Joined Mar 19, 2019
4,132
The "Kobe crash" was due to lack of ground sensing radar which was supposed to be a safety feature of that model. Not sure why it wasn't installed as it is supposed to be on that model.
 

jpanhalt

Joined Jan 18, 2008
11,088
The "Kobe crash" was due to lack of ground sensing radar which was supposed to be a safety feature of that model. Not sure why it wasn't installed as it is supposed to be on that model.
I disagree. It was purely due to pilot error flying under special VFR-helicopter conditions. The exception requires the pilot to be in visual contact with all terrain. With fixed-wing aircraft, there are clear visibility limits, not so with helicopters, as they can hover.
 

nsaspook

Joined Aug 27, 2009
9,488
The "Kobe crash" was due to lack of ground sensing radar which was supposed to be a safety feature of that model. Not sure why it wasn't installed as it is supposed to be on that model.
Sadly that crash IMO was due to the pilot having a bad case of “get-there-itis”. Poor judgement to make a VIP happy put them in a place nothing could recover from.
 

jpanhalt

Joined Jan 18, 2008
11,088
@SamR

This is one of my favorites from Farside:
1581898104034.png

I have a personal connection with that. Many years ago I was flying VFR form STL to BAL (BIA today) over Eastern TN via Roanoke. I thought about scud running and talked to flight service in Nashville. He convinced me to spend the night. I am glad I did, as are my yet to be born daughters and son.
 
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