THIS will certainly impact my desire for the S5, unless there are something inside we don't see that re-enforces the area. If it is as he described, sharp-edged metal hitting thin carbon, then it's absolutely a design FAIL, big time.

If actually true, I certainly didn't expect anything like this from Cervelo, but when this version came out, I just didn’t like the the design, which is what lead me to buy the previous year's S5 model.

“Impact” your desire. Love the pun!

that is ridiculous. this makes 5 significant design errors by Cervelo.

First iteration of their carbon R series bike, the R2.5 that CSC rode had a recall on frame
Second, the wolf fork had a recall
Third, the P4. The whole frame. Disc wheels wouldn't fit a TT bike.
Fourth, the B-Bright bottom bracket would creak like hell and 3 different mechanics I had work on it could not get it to go away. Apparently they have fixed that issue now with new design

and now this which is a significant safety risk by looks of it.

I just bought an Aspero gravel. fingers crossed!

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@rhyspencer

Add to that the safety recall for the 3T Aduro basebar that was stock on the last gen P5.

Also, for those interested, Hambini does a complete (NSFW) takedown of Cervelo bottom brackets as well. His main point: Cervelo engineers have loosened there manufacturing tolerance standards such that frames may be produced with ovular shaped bottom brackets, making it nearly impossible to fit bearings and or a bottom bracket into the frame. https://www.youtube.com/watch?v=GWDztuezn0g.

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CG

sounds like a 3T problem


taking anything that guy says seriously would be a mistake.

Some of what Hambini spouts about that is wrong tho.
He quotes tolerances for the bearing installation. But then compares to the housing (= frame hole) tolerances.
He chose to forget the metal bearing 'cup' that the bearing actually fits into - which will 'absorb' a considerable amount of ovality in the frame hole without doing the same distortion to the bearing housing bore.
He's selectively mis-quoting figures.

Good to know.

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CG

5 whole errors since the r2.5 holy crap call the BBB.

R2.5, limited number of frames and they were late model ones. Sounds like more of a manufacturing problem than design it wasn’t the whole model line.

Wolf fork - Cervelo didn’t produce these they specd them on their bikes. Not only that after the type of stress was determined to be a failure point Cervelo stopped using them and voluntarily recalled them, even though the company who produced them wouldn’t recall them.

P4- the frame was not recalled. If you tightened the bolt in front of the seatpost too tight it could potentially split a small piece of the carbon behind the seatpost making it very difficult to tighten moving forward. Cervelo basically have everyone a new 2011 p4 if this happened even though the person tightening the bolt was normally at fault.

The frame also fits disc wheels that were out at the time they were designing the frame. It was unfortunate that zipp went super wide with discs the same time the frames started to come out, but that wasn’t realistically their fault. Shit happens.


The bottom bracket can creak on the newer frames I will give you that.

You know he's also torn apart Enve, right?

He literally makes (something of) a living off cutting apart companies' products (literally and figuratively).

Okay.... are you able to explain away this S5 design flaw though?

I never said the P4 was recalled though I can see reading it carrying forward the previous 2 recalls it can be construed that was what I typed. I said the frame didn't fit discs. The P4 did not fit my Mavic disc at the time it launched. At that time Mavic was quite possibly the best disc on market. The brakes were, well not really brakes were they? What I was leaning to is the whole bike was crap. Please know, I have had 2 P3 bikes in my TRI racing. Great, affordable bikes. I have had an 2 R3s and an R5 which I loved. My point being if a company brands their business as outperforming competition with their engineering it is not a good luck. I am sure Specialized and Trek have had recalls but they don't brand themselves as outperforming engineers. I ride a Madone now and have a few complaints for sure. Love the bike, have issue with a few design flaws.

the design flaw in this video is pretty significant. If the internal piece causes delamination with it rubbing against the frame I assume a safety risk. As I traveler every time I packed down that bike its a risk.

perhaps I was a bit aggressive in the slam of Cervelo. Apparently I still hear the creaking in my ears-:)

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@rhyspencer

I have an S5 Disc and have not had any issues. My bike limits the turn well before it comes close to the frame.

Not sure I see this as a design fail. Take pretty much any new carbon aero frame and push the front beyond its turn limit and I am sure it will break too.

Sensational title with little substance. Reef your bars sideways and you bike may break might be a better title.

Nice to hear from a current S5 disc owner! Could you elaborate on how your bike “limits the turn well before it comes close to the frame”?

The turn limits about 2cm prior to coming in contact with the frame as he indicates. It may be a bit more or less. I have not pulled it apart to look at it but there is something inside the head tube which limits how far it turns. I could probably force it beyond that but that would require me to force it past where it wants to stop.

i believe luescher (sp) is referring to internal stop (i.e. inside the head tube). i have pulled apart my front end but i don't remember looking at the front of the head tube (on the inside).

it's not something i find worrisome, and i am sure that the people at Cervelo are smarter than the guy on youtube.

Wait, what?! So, some dude trolling for clicks on YouTube isn't smarter than the people getting paid to do this for a living? Imagine that.

That’s a little harsh! This dude used to be an aviation engineer who decided to start his own carbon bike repair company. If you look at the facts of the video, the S5 is designed in such a way where a metal cam comes into contact with the frame as a way to limit the travel. If you are comfortable with that, then good for you, however, I don’t think it’s fair to call that guy a troll.

Well..... the designers of the Boeing 737MAX were also paid to do it for a living. Mistakes can still happen.

To be fair, the problem with the Boeing 737 max was a systems engineering failure, not a design engineering failure. A bike is a bit less complicated than an airplane, so I doubt cervelo has that kind of problem. That being said, they can make mistakes I'm sure.

Also, regarding the metal cam that stops the travel, how is that any different than the metal pin which stopped travel in previous frames? Additionally, if I remember right the guy said that the damage happened when the bars were twisted violently in a crash. So yes, the S5 disc isnt very damage tolerant, but I dont think that makes it a bad frame.

It's not rocket science to build in a protective bumper.

example: Bianchi Aquila CV rubber bumper under the head tube. stops the fork from crashing into the frame and damaging it.

Sure, it isn't as elegant, but it's a much better solution.

still not clear how common that delamination is or how much force it needs - was his example frame from a crash?


its good to be aware of but isnt this still much preferred to when handlebars used to swing around (when dropped, in an accident, when carrying the bike) and the handelbars put a dent in the top tube?

why would cervelo would remove the lower limiter pin from the first model? was it too heavy?

Point taken on the 737!

The metal pin on the previous model was a sacrificial part that was non structural. The metal cam directly uses the inside of the HT to stop travel.

Handle bars swinging into the frame for most bike frames require an extreme angle which would happen only in a crash or very rare circumstances.

The angle in which the metal cam slams into the HT under the nose cone seems less than 90 degrees. I speculate that something as minor as a gust of wind while bike is racked in transition could lead to the handlebars turning enough for the cam to make contact. We don’t know what kind of tolerance to impact the frame has, but I would not underestimate the force produced by heavy aero handlebars and possibly clip ons combined with the torque from a long stem. This is then exacerbated by the fact that all this force is channeled into the small surface area of the metal cam into the head tube.

One could argue if it’s a flaw or not, but if I were to pay top dollar for this bike moving forward, I would definitely want Cervelo to come out and provide an explanation.

And interestingly they did exactly this on the P5 which came out after the S5... they surrounded the edge of the fork with rubber to better spread the load of such an impact!

Unfortunately I think the actual endstop is the brake cables running through the headset clamp parts which stops the rotation before this endstop. Does anyone have a pic of the inside of the frame? If it is not reinforced with a few extra plies in that area it will definitely impact my desire for this bike!

I just checked and see no problem on my S5D. The handlebar is not rotating as much as shown on the video which may be due to the removal of some internal parts. I will ask Cervélo about it and keep you all posted.

---

- Antony Costes -
PhD in Biomechanics / Professional Triathlete (9 pro wins)

"If you cannot measure it, you cannot improve it."
Lord Kelvin

Please note that the real possible problem being talked about in that video starts around 3:55. Namely, there's a wedge inside the frame which is the actual "stop" built in, but by the design, it essentially hits the wall of the steerer tube in every case when handlebars are rotated to around 70+ degrees - which can happen in many situations, as already pointed out in this thread. And you don't need to be a materials expert to think what happens when a quite thin layer of glued composites is repeatedly hit by a piece of metal - and in this case, even a sharp one!

Myself, as an owner of S5D, I'm quite shocked by this and would really appreciate Cervelo coming out with an explanation which is better than only "in ordinary use handlebars never turn that much", like in a statement which was quoted by Cervelo at WW forum (bolded areas by me):

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----------------------------
Need more W/CdA.

I haven't taken a close look at my wife's new P-Series tri bike, but the head tube area sort of looks like the S5 one in the video...makes me wonder if it will have the same issue...

Sure that n=1 without proof it’s what actually caused the problem isn’t a design flaw.

I’m going to trust the people who actually built and tested the bike that it’s not a problem. The person could have somehow slammed their bars to that side causing the problem, who knows, just because one guy with a YouTube channel and a few guys on a forum say that it’s a design flaw doesn’t mean it actually is one.

I don’t need to make up some outrage today I’m good.

no other cervelo bike is similar

Really ?
Well SOMEONE (who was not doing the work for free) designed a single point failure into the control system didn't they ?

See, now i know for a fact you’re talking bullshit and conspiring to cover up for Cervelo. When my P4 failed, they replaced it with a P5 *for free*, not a new P4 like you allege. I was outraged by their egregious business misconduct. Get your facts straight when trying to pull one over on us.

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Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”

That's some serious BS right there...

"...poor handling will cause damage to the bayonet area".



In what world a $5k frame should fail by poor handling?

Any time the bars of a SpeedConcept are turned more than say 35 degrees, you make nice carbon to carbon contact at the head tube and put a nice dent in the top tube. I have nice divots in there after the first time the bike was on a transition rack. Nothing stopping deep denting at all. At least this has a stop.

This is just an inherent limitation of an aero bayonet design it seems.

The Tririg Omni has a nice stop in the design, but in a fall, I think it could cause damage--but that is a fall. Bad things happen when you fall on aero bikes. Its not my dirt park jump bike.

I'd be fine with this design on a TT bike where the possibility of a crash or random handlebar movement is really limited, but on an aero bike, which is destined to be in the middle of the pack in an aggressive sprint, not so much.

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----------------------------
Need more W/CdA.

Couple of things to point out here. First of all, the "sharp piece of metal" that everyone is talking about (as if the pointy end of the stop is what's contacting the frame) is actually two flats. The flat parts of the cam are what's contacting the inside of the frame on each side, thereby spreading the load over the surface area of each flat. That's massively different than the sharp point making contact. Secondly, everyone (including the guy that made the video) is talking about carbon fiber like it's peanut brittle. It can take a fair amount of abuse, and it certainly can take some low-speed bumps from a flat on a cam. Now, if you crash or do something assinine where that metal piece makes contact with extreme force, then yes you may damage the frame. I can't see a situation where that happens in normal use, and I can't see how that's any different than wrecking your frame in any one of 1,000 other ways in a crash. Lots of hype and hysteria, IMO.

You saying that the head-tube is meant to take the load of regular impact can be perceived as pure speculation.

As a potential buyer doing my due diligence in researching the frame, I wish Cervelo would step forward and say something concrete rather than “poor handling will cause damage....”

It would be good if they can define poor handling. Does accidentally knocking your bike over at a coffee stop count as poor handling? How about lifting up the bike without holding the front end resulting in the handle bars swinging over?

No, saying the head tube is meant to hold up under normal use is just common sense. If it wasn't meant to, there would there would be a warning against it.

Besides this guy's video, is there any real-world evidence that this is an issue? Just treat the bike like you'd treat any bike and you'll be fine.

Edit: I have to come back to this point. You said that this guy is supposedly an ex aviation engineer who started his own carbon fiber repair business. And yet, at least 20 times in this video he appears to be in utter disbelief that a "sharp edged piece of metal" is making contact with the frame. This just shows a complete lack of understanding of how this stop even works. Who in their right mind would look at that mechanism and assume the pointy edge of that cam is what's making contact with that frame. Certainly not any engineer I've ever worked with. Just makes me take his whole rant with a giant grain of salt.

Of course they don’t have examples. It’s stupid. It’s not like Cervelo puts out shit bike and this is just another to the show how crappy they are. In generally they put out amazing bikes. But our forum keyboard engineers with no design experience with this bike or bikes in general just watched a YouTube video from a guy with some very questionable history and they’re gonna take his word over Cervelos history.

I'm an engineer (not material)... from what I can see, the cam piece's flat surfaces does have hard edges and they will be the ones tcome into contact with the inside of the headtube which is round.

Not saying Cervelo didn't/doesn't make good bikes; I have over the years owned 6 of them and still have 2 including the last gen S5. But that doesn't mean they may not have design flaws from time to time, and even taking with a large pinch of salt, what the video shows is somewhat concerning, and deserving a more specific response from Cervelo in terms of what's their definition of "poor handling" which could cause damage. I would certainly also like to know how many cases Cervelo knew.

I'm sorry - I'm not trying to be a jerk to you so please don't take this personally. I just don't understand this line of thinking. I think anyone that's ever ridden a bicycle intuititively understands what's normal use and what constitutes poor handling. It's this sort of thinking that results in getting a 30 page booklet with your new toaster telling you to not stick your head in the toaster, not to stick the power cord up your ass, not to make toast while in the bathtub, not to store paper products in the toaster, etc.

I feel like if you (not you necessarily, but anyone) bought this bike, you sort of deserve everything that comes along with it... this thing is hideous looking. Cervelo will be fine, they'll be able to replace all 27 of these that have been sold, and the 30 others they provided Team Sunweb. They'll be fine.

It may be just me reading that response from Cervelo, I thought "poor handling" also includes when I am riding and not handling well, e.g. turning too far. And it's that "poor handling" I found to be troubling.

I think it looks great, and is an awesome bike! I've seen a ton of them on the road. They sold way more than "27"

Even if it’s the flat bit, “hard and sharp” is the right term to use in the context of a small but flat metal cam coming into contact with a carbon fibre laminate. I think you are 100% correct in pointing out that it is the flat bit of the cam, and I also think Cervelo is good reputable company and won’t be stupid enough to use the edge of the metal cam as the point of contact with the frame. However, I can’t help but feel this design is downright dodgy, or at the very least, a point of concern that needs more clarification.

I also get your point on the company not being able to give a list of “what not to do.” But in light of this video, as well as interest generated in forums, surely they can come out and give further clarification that is better than “regular use does not affect the design” and “only crashes and poor handling will cause damage.”

As an aerospace composite scientist I am very aware of the impact resistance properties of carbon fiber. Using words like 'fair amount', 'low speed bump', 'asinine', 'extreme force' all suggest you're guessing. We do extensive impact testing at work and if there is one big limiter for carbon it's its limited impact resistance. (Number 2 would be compression resistance). And as higher cost models use more high modulus fiber (vs standard modulus in cheaper frames) it becomes even worse. This design of using a solid metal piece to hit a thin carbon tube is asking for trouble. You really don't need much speed to make a significant impact (a lot of our products have specific impact requirements that come from aircraft engineers dropping their tools on these parts during assembly). I think this design is really weak, but could have been much better if there was a metal inner tube bonded to the carbon headtube and the impact would have been metal to metal. It would limit the strain on the carbon caused by impact and make it much safer.

Great point on the high modulus carbon. Could changing the layup direction and fibre type at the impact zone help mitigate such a problem? Cause the engineers can’t be stupid right? Surely they have some measures in place that they just need to tell us.

Yes, ply orientation plays a big role. But if you optimize for impact by going with a more quasi-isotropic layup for example, you lose stiffness for the same ply count. So you'll have to add more plies to increase stiffness again which then again increases cost and weight.

The 737 has only ever had a single airspeed sensor. Therefore, this aspect of the design wasn't changed, because the upgrades to the max were primarily in the engines and the wings. What happened was that a proper systems engineering analysis was not performed to identify any unintended consequences of the stall prevention system, or to identify instances where there is a single point of failure. The individual systems worked as designed, the assembly did not. The DESIGN engineers were not responsible for the error, it was primarily a SYSTEMS engineering failure, as I said previously. You dont have a design engineer that makes an airplane. There are a lot of teams that design subsystems, and it is a systems engineer that ensures all parts integrate properly.

So there was a single point failure Designed in from the start.

Here "Poor handling" might mean dropping bike, letting bars swing aroung on bike rack, picking bike up on shoulder without holding front wherl etc rather than bikehandling (steering skills)

Every $5k bicycle frame in existence...

That's a tautology, though. Poor handling, by definition, is poor.

The question is whether the bars swing to the stops only during "poor handling," and whether even a frame where the owner engages in "good handling practices" can be expected to never have it swing to the stops with enough force to cause any damage.

The first is a clear "no". Bike racers do Bad Things to bikes through the nature of bike racing. There's the old saying, though, that if you can't afford to jack up your S5 in a race, don't race the S5. And always examine your bike carefully after a crash, particularly in the headtube area.

The second is debatable. Even people who are really conscientious sometimes accidentally cause light-force swinging of the bars. I've done it a few times to various expensive frames while, say, adjusting my workstand angle while working on them. (this has never caused any sort of visible damage whatsoever) Maybe this is a frame where you just have to secure the bars with some zip-ties every time you work on it or do non-trivial transportation. Which is a bit tedious.

See my previous post... I read "poor handling" to include "not handling the bike well while riding". So it could be my mis-reading.

Yes I think that is you misinterpreting the statement.

2 minutes of substance and 9 of pedantry. "do these design engineers who design these bikes actually understand anything about carbon fiber and impact?" that statement is arguably pedantic the 1st time, and by the 5th time one wonders what the real point is of the video.

at 8 or so minutes he says, "i could do a hambini, and use every word under the sun, but that's not my style." but my impression beginning early on was, this guy is a hambini. it certainly is his style. and like hambini there's a grain of truth surrounded by a mountain of self-importance.

there may well be a better way to keep the handlebars from contacting the frame. but to place this in perspective, the first bike i came across that had a device that limited turning radius was about a decade ago. somehow i rode and raced for 30 years without any design feature that kept the handlebar from hitting the top tube. this video could have been 2min of "here is how i would have done it" rather than 11min of hyperbolic clickbait.

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Dan Empfield
aka Slowman

A better way in my opinion is a external limiter like the P5D

fine. see? that didn't take long. i also think no turning radius limiter is okay. place a sticky rubber piece on the frame, at the point of contact, if you want. and, you know, do your best to keep the handlebars from hitting the top tube, which is contraindicated.

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Dan Empfield
aka Slowman

Style or clickbait aside, did he show something that's concerning? Sure. He's not the perfect messenger but the message should be heard.

I am in the market for an aero road bike since I sold my S3 last year (but still have the last gen S5), the new S5 is one I've been seriously considering. But not anymore. As someone else mentioned earlier in this thread, if Cervelo just bond some re-enforcement in that area, I would be much more likely to consider it again. As a consumer asked to put down our hard-earned $5k, I don't like the design and the risk associated with it, as it is now.

No, he did not. He identified one of a thousand ways you can ruin a frame if you are careless.

From what I've read on the interweb (please correct me before the lawsuits arrive)
1) Bigger engines are more efficient, which customers want.
2) But they don't fit under the wings without making the landing gear taller
3) Which would require a completely new FAA airworthiness certificate
4) But if you position the bigger engine further forward and up a bit you can keep the original landing gear and avoid the full homologation procedure
5) But that affects CofG and stability, so you need a cleverer anti-stall system
6) Which they implemented as it's cheaper than 2&3 and should be just as good . . .
7) But kept relatively quiet about it as "less stable than the one you're used to" isn't a great selling point
So IF it does't work too well and pilots aren't well informed about what it is doing, you have quite a big issue.

Interesting. My R3 does not have this problem but my NP3 has a flimsy ass pin that works as a stopper that already came out once... and when it was out the fork would contact the frame and the brake levers would hit the top tube - even the front brake would contact the frame. When I contacted them about it, they were not very helpful. I basically had to find someone who had a busted frame and were willing to pull the pin from that frame for me. Cervelo's position was that they did not have any spare pins because the company that made them was no longer making them. They even went as far as stating that by epoxying it back myself I could be voiding my warranty and it had to be done by their dealer. Although the original dealer that I bought from ended up getting Cervelo to send me a nice cycling kit and a bottle.

It's weird that Cervelo keeps having this issue in varying manifestations between different frame lines. They sure make nice frames though....

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Next races on the schedule: none at the moment

Except this is a built in stopper that will damage a frame much easier than any other frame and therefore is a ligit design flaw. It makes it much more prone to failure than most other frames out there.

...in which case there should be many examples of frames being damaged in this way. Aside from the one in the video, can you point me to another one? Lots of hand-wringing here and on weight weenies. Zero real-world examples of this being an issue.

What are you basing “It makes it much more prone to failure than most other frames out there. “ on? Have you looked at any others?

I have about 10k on my S5D and there is no indication of any type of wear or damage.

You are correct insofar as it goes but it was a business decision, not a systems engineering failure. They knew it was bad and went forward anyway. This is what happens when the executives are in Chicago and the engineers in Seattle.

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Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”

You are incorrect Eric (or inaccurate). They knew that they were cutting corners with the 737max, but thought the engineering was good and it will be ok. Maybe that was what you meant to say.
They saved a lot of money on training and re-certification of pilots by making the software of the max simulate the behavior of the original 737 (how they got the FAA to accept this is another matter). But software always has bugs and combined with the single sensor the results were catastrophic.
Not sure how this got dragged into this thread.

So, bigger, more fuel efficient engines, which also produce more thrust. They still had to be FAA certified, but they didnt want to have to retrain pilots, so they designed the new system so that it basically flies the same as the old 737. Problem is, new system is dependant on the airspeed sensor, which wasn't a point of failure in the old plane. Airspeed sensor went bad, plane was convinced it was going nose up and forced the nose down. Overrode pilot input, which is another key failing in the system, whenever they turned it off, the airplane turned it back on. Ended up forcing the crash. Basically the system wasn't analyzed properly to determine the critical points of failure, and the system couldn't be overridden

Based on my understanding of the mechanical properties of composites, and how using direct impact between metal and carbon fiber is using the material’s weakest property as an active operating mechanism when you could easily find better ways to accomplish the same.

So your argument against us is that we’re using an n=1 example, and then you go ahead and use your own n=1 experience to validate your claim.

Cool.

I am basing on my experience with the product. You started this thread based on a YouTube video.

We are basing on basic knowledge of materials. We are saying, hard metal cam knocking against soft structural carbon fibre is a bad idea.

Your response to that is essentially “mine rides fine, show me more failures first!” So if your personal experience trumps material science, and you are happy to continue riding your S5D as it hasn’t failed yet, I am happy for you.

i can't count on one hand the number of top tubes i've seen damaged from over-rotated drop handlebars.

that top tube is a pretty effective built in stopper in the event of "poor handling."

point of order: neither in law/politics (where the term is used) or in the description of a mechanical device, such as in a patent application (where the term is used) would i consider this to fall under the definition of "active operating mechanism". but i might be wrong and if i am then, fine, i'm about to learn something. (and to be clear, it's not the "operating mechanism" part i question, it's the term "active".)

metal and carbon are in contact with each other a lot, and on several parts of the bike. when a BB or headset bearings or dropouts or fork ends, or stems or compression rings attach to a carbon frame, it's metal against carbon in a way that absolutely is subject to stress (and therefore to testing). you used the term "impact" and, yes, that adds an additional element. but when i read the term "active operating mechanism" the way that term is typically used, when i've come across it, it's in the regular or prime function of the device or motor or unit. a prime action that makes it do its thing. for example, a chain hanger wouldn't be considered the "active operating mechanism" of the bicycle's drive train.

over the life of the bike the manufacturer could hope that such contact is never made. however, it's clear that such contact is contemplated, or else the bike wouldn't have been built as it was. i'm not saying this is the ideal way to limit the radius of travel. (personally, i've never liked having these devices in the bikes i own.) my only point here is to question whether "active operating mechanism" is the appropriate term of art in this case, and it's not a minor point, because the repetitive, hard, banging of these two surfaces is not the intended use of the product, it is a rare circumstance of bike ownership.

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Dan Empfield
aka Slowman

     
For what it's worth I'm a project engineer and senior engineering manager at a large aerospace and defense contractor. I've been in aerospace for 18 of my 26 years as an engineer. As such, I have ultimate technical responsibility for the design, manufacture, and certification for whole aircraft, avionics, and systems modifications. During my career I've been involve in a few crash investigations and detailed system operation and failure analyses to attribute the causes and reconstruct the events resulting in loss of crew SA (situational awareness) which resulted in a set of erroneous actions and ultimately deaths.

There are numerous factual errors in your description of the mcas system operation, and sensors. Number one on the list is that the primary sensor failure was an angle of attack (AoA) sensor... Not airspeed (pitot tube). However there are numerous other design and systems engineering, safety, and airworthiness errors involved. There are a whole host of errors in the failures and plenty of blame to go around. No major aircraft disaster in the last 50 years can be described by any one simple system failure. EVERY one is a complex set of circumstances and failures that results on a loss of crew control.

It is the complexity of the failures that has kept the fleet grounded. A simple problem such as a single point of failure would be easily rectified and the aircraft would already have returned to service.

Further your characterization of the division in responsibility between systems, and design engineer is simplistic... At best. As noted above, there are a lot of disciplines involved in the failure... Some are design, some are systems, some are safety, some are test, some are airworthiness, some are senior management (up the the ceo), and some are directly related the the FAA. Any description that simply attributes these failures to any single disciple is frankly wrong... And belies a fundamental lack of understanding of the way that commercial aircraft are designed, tested, and certified.



Back to the OP.

Thanks for the detailed post.

I still say the proximate cause was a business decision though...

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Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”

If you are interested to understand the full scope of the many failures of the 737 max, here you go:
https://spectrum.ieee.org/...a-software-developer

The bottom line, the plane is one kludge on top of another kludge. And, software fix or no software fix, the plane should be scrapped.

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Advanced Aero TopTube Storage for Road, Gravel, & Tri...ZeroSlip & Direct-mount, made in the USA.
DarkSpeedWorks.com.....Reviews.....Insta.....Facebook
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I get what you're saying, and I wouldn't ENTIRELY disagree. We (me and my fellow project engineers... Both in my group and outside it) have spent a good deal of time discussing the systems particulars.

And, it won't surprise me if what you say is the ultimate attibution in this instance. But, have you ever tried to get 50 people to all do the RIGHT THING? There are a lot more people involved in this debacle than THAT. BUT, Even THAT is more frustrating than sometimes seems worth the trouble. People suck.

I guarantee there are 100s of people involved in all the affected systems here. So, turn that around and try to get XXX to commit to doing THE WRONG THING... where no one will blow the whistle...for being "Forced" to shut up and do what they are told. No one is ignorant to (or callous of) the fact that human lives are at stake in this industry. It is lesson number 1-10. We live and breath it.

I work with engineers at Boeing. People who used to work at Boeing work for me, now. Hell, I work with every major airframe manufacturer in the world except airbus---not sure why that is, I've worked with dassault... So it's not a French thing. I have NEVER worked with someone who would consciously compromise aircraft safety for a dollar. Simply never. Further, the people on the certification side are an entirely different breed of ethical.

My point being... It's just more complicate than can be distilled to a simple, single decision. Too many people didn't realize the circumstances they were setting into motion. Every choice along the way seemed right, at the time. Nevertheless, we need a simple villain. So, as I said, it won't surprise me if there is a scapegoat in the news even if the ntsb report is more nuanced.

Ugh. That article is worse (less well informed) than anything written in this thread. I liken it to click bait. I'm not even going to start listing the errors in it. I don't know what that guy's problem is, but he is patently wrong about pretty much everything about how this really happens.

Well, you should definitely alert the IEEE about that, sounds like their publishing standards have gone down the toilet.

But having a bit of heavy metal experience myself, l would definitely be interested to hear your full critique.

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Advanced Aero TopTube Storage for Road, Gravel, & Tri...ZeroSlip & Direct-mount, made in the USA.
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A full critique would be longer than the article.

I don't know what IEEE publishing standards were used in publishing this, but I note the disclaimer at the top of the article...



That's not a damnation by itself... But nevertheless, IEEE has distanced itself from this article for some reason. Maybe IEEE always puts that disclaimer up....but, if so... Exactly what is the prestige of published in IEEE?

Much of the problems with this article are in the presentation of the problems (and solutions) with the 737 max as being unique / novel. Dynamic instability is not new. Further, it presupposes that the flight characteristics of the 737 max are, in fact, danamically unstable. But, the description of the flight characteristic is not correct, nor does it describe dynamically unstable flight.

Fly by wire is not new---to the degree that the 737max could be considered fly-by-wire. MCAS is not new, it was outfitted on the kc-46 for example. MCAS is NOT and anti-stall control system---and was NEVER intended as such. It was intended to mimic the flight control characteristics of the 737NG, so that 737NG certified pilots could directly transfer over the the max. Anti-stall systems work ENTIRELY in a different manner. Again, this was not intended as a safety system, rather just to make it fly like another aircraft. It is clearly imperfect---catastrophically.

Flight critical software development is not new. Flight critical software development is not under control of a software development manager. Review, evaluation, test and certification are roles that are performed by entirely independant entities... Each role is in dependant of the others in LEVEL A. I've written flight critical software, personally... And I've created entire flight critical development procedures for companies that I've worked for. The auther got more wrong than he got right. For reference, the standard that generally governs such development is DO-178. For direct control of flight surfaces that would be Level A--the most stringent. Such development is NOT performed by junior engineers....those kids get to cut their teeth on Level E---"does not apply". Level A is done by the most expert of software engineers. Engineers who DO inherently understand flight dynamics, and control laws. Often they have advanced degrees in flight sciences or aeronautics.

The article presupposes that that "right" aircraft design changes would have been too expensive for Boeing to contemplate. That is to wholly not comprehend the spending power of a giant such as Boeing---or where Boeing makes its real money. It's not just in the metal. As a sometimes partner, and other times rival with Boeing...trust me, they can spend money like very few can.

Finally, DERs and DARs would not be used by most aircraft OEMs including Boeing for a program of this magnitude. The DER/DAR system is typically used by smaller companies that only sparsely do airworthiness related work... Or for smaller projects that the OEM doesn't want to waste its own more precious resources on. Rather, an organization like Boeing or the company I work for has an independent arm called the ODA (organizational design authority). This is not a materially different process, but the fact that the author doesn't know the difference suggests he's mostly talking out of the wrong end.

The anonymous quote towards the end of the article is humorous, in that it is clearly by someone who CLAIMS to have written avionics software. However, they says this was "ten years ago" as if things were wholly different back then. They were not. I wrote my first DO-178, level B software in 1995, 25 years ago. At that time, the standard was on Rev B. I haven't looked up the original publication date of Rev NC. But, it certainly predates my entry into the engineering field.

Note... This is not a point by point exhaustive critique of the article. It's just enough to point out that there are numerous factual errors... And the article is riddled with bias. There are some truths in it, but... It's hard for those outside the industry to tell fact from fiction.

The worry is you have a light crash or pick up your bike and have the handlebars swing around a few times whatever but a few impacts you think nothing of and as the dude in the youtube video points out some light delimitation and cracking that you don't notice. Next thing you know you're sweeping down a mountain at speed braking hard into a bend and your frame front end is compromised... I don't want to be in that position.

I really liked the S5 and probably is a great bike to ride but I agree with the guy on the video a major design flaw in my opinion. Carbon is not designed to be impacted like that.

Thanks Dan for articulating my thoughts. The video editing was so bad – indeed non-existent – that I couldn't make it more than a few minutes through this tedious and repetitive diatribe. I'm surprised that so many viewers have the endurance to make it through the whole "production". Some journalistic integrity would also go a long way to boost confidence, like "I reached out to Cervélo to discuss the issue, and here is their response...".

Raoul . What would you suggest as a bump stop .Consumers demand integration ,aero dynamics stiffness and lightness .Sometimes complete practicality needs to be compromised for ultimate performance . Im suggesting an F1 car would struggle to park in the Maccas car park or if you crash it ,it breaks .

I’m not Raoul, just merely sharing his video. I’m no engineer, and will not pretend to be one. But I was thinking, why not an elongated piece of really hard elastomer clamped onto the steerer tube that will limit the travel as the nose cone tapers to the side.

Usually, the IEEE does not publish clickbait type articles, is your experience otherwise?

But I am puzzled, did you read the article? Because the author does not say dynamic instability is new. He does not say fly by wire is new. He does not say mcas is new. He does not say that mcas is primarily an anti stall system. He does not say that the development of flight software or flight critical software is new. He does not say that the software developent was under the control of a "software development manager" only that the code was created by humans under the direction of managers. He also does not say that such development is performed by junior engineers. He also does not say that aircraft design changes would have been too expensive for Boeing to contemplate, only that designing and certifying a new aircraft takes a lot of money, and that money (and selling points for the airline in saving pilot training costs--also back to money) was the main motivation for not going that route.

Ultimately, the economic decisions to create the frankenstein 737 max have proven to be an enormous disaster, one only needs to look at the dead bodies and boeing's bottom line to see that. And where exactly within boeing the buck stops is a good question. But this massive systems f*ck up will be one that will be studied for decades to come as to how NOT to design an aircraft.

Someone wiser that me once said, "It's more complicated than can be distilled to a simple, single decision. Too many people didn't realize the circumstances they were setting into motion. Every choice along the way seemed right, at the time." I would only add that good design systems are those where people DO realize the circumstances they are setting into motion. And, that in the 737 max case, many of the "choices along the way" were made purely on economic and marketing grounds, and that is where things started heading south fast ...


On a different topic, hope your recovery is progressing well. Hopefully you are finally home and out of the hospital.

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Advanced Aero TopTube Storage for Road, Gravel, & Tri...ZeroSlip & Direct-mount, made in the USA.
DarkSpeedWorks.com.....Reviews.....Insta.....Facebook
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Yes, thanks. Home and exercising (hill walking). Medical parole hearing is Tuesday....for release to work.

I understand the hypothetical concern, but I believe it's just that. Again, where are all the real-world examples of these types of failures if it's that big a design flaw?

He's playing dirty imo. There are compromises and limitations with aero designs. And the original engineering/service could be consulted. We don't know what kind of hit that frame took as well to get to that point.

What's his alternative proposal?

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Training Tweets: https://twitter.com/Jagersport_com
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He said several times that the previous generation with the replaceable pin was much better.

I’d say they're somewhere around equal given that there is no confirmed cases for either model of this being an issue.

How do you know that? Unless you are in charge of customer service at Cervelo you wouldn’t have access to that info, right? So let’s not make up ‘data’.

hill walking already. that's great. bionic man.

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Dan Empfield
aka Slowman

He has a couple of examples in his video even marked out where damaged with a marker. As he explained and I explained in my in my post, that it would concern me and what I consider a design flaw as it could happen so easy. I have a Dimond and they have a pin in the base of the fame behind the headset and carbon ridges on the fork in place as stops for over rotation so no structural carbon is impacted. Feel free to buy one, that is your choice but I'll give this model a miss.

Well let’s see, all we have as an example form anyone is this video. If this were an actual problem you think someone who is saying this is poor engineering could come up with someone on the internet that has had this actually happen to them.

So that's assuming and not knowing, and even your guessing doesn't mean a design can not be bad. Sticking your hand in boiling water is a bad idea even though I don't know anyone that's actually done that.

sticking head in the sand seems to be the strategy of some here, tho

But unlike boiling water no one can agree if it is a good or bad idea...

Don't be so F***ing stupid. You can't absorb ovality. If it's oval then whatever you put into it will either become oval or the strength of whatever you put in it will make the oval into more of a round shape OR more than likely an in between point of the two.

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HELLO HAMBINI FANS!!!

Three opinions here:
1. People here calling Raoul a "troll" are out of line. He makes his living repairing carbon frames and components, he does not make his living on YouTube clicks. He has no conflict of interest in calling out Cervelo here.
2. The Cervelo design is dumb, period. You don't need to have an engineering degree to see that a design that stops travel on the fork by having a pointed metal piece impact an unprotected, thin CFRP wall is a really stupid idea. I have no idea why people here are defending this design.
3. Cervelo hardly has a sterling reputation when it comes to engineering. Talk to any mechanic. For similar reasons, I'll never buy a BMC.

Ahh, truly the sign of a winning argument. When you can’t prevail with logic and facts, just yell and name-call.

But but but he’s a engineer 😜

1. Yes.
2. Yes, some triathletes love the Cervelo Kool Aid.
3. To be fair, can you point out instances where they have bad designs apart from this recent S5? Recalls due to manufacturing issues don’t count as that is a third party factory QC issue rather than a Cervelo engineering issue.

BBRight?

Note - I have been a Cervelo fan since their beginnings and have owned several, but I am now shopping for a new road bike and the S5 looks interesing but this design worries me and I will likely get something else because of that.