Hacker News Reader

Comment by rkagerer | Hacker News Reader

But what I see is innovation and trying new stuff.

I like your positive attitude. Though I think there were some engineering shortfalls that should have been avoided with common sense.

Eg. The original hook didn't work because the shoe was angled up too high to catch the wire. The engineers designed it based on a flawed simulation model. The guys field testing took one look and knew it wouldn't work. Heck, I showed this photo to my partner (non-engineer) and the first thing she said was "it's not pointing right".

https://the-engi-nerd.github.io/posts/welcome/images/clipboa...

You can see the original (blue) vs revised (red):

https://the-engi-nerd.github.io/posts/welcome/images/clipboa...

View on HN

My first class in Calculus based physics, my professor did an interesting thing. We would be asked to intuit the answer to problems before we did the math to know for certain. Physics is simply not intuitive.

Now, with regards to the simulation, the thing I think they failed on wasn't a lack of common sense. I think what they should have done is reproduce the results in real life using a similar jet. They relied on the model a bit too much and "Tested in production."

However, as far as mistakes go, this is a pretty small one.

There isn't a similar carrier aircraft in the inventory that could have been used, as far as I know.

I was thinking something like the Goshawk. Then use the video to compare with the model.

Looking at the image, and knowing designers assumed the cable would rebound before being cought by the hook, the original design of the hook itself makes sense: catch the cable in the air and make sure it doesn't slip down the hook.

Obviously it doesn't work to catch cable lying flat on the ground. Which was, again, not the initial design requirement.

In another thread about Boeing, the topic of good sources to learn about real engineering came up. Well, this is a great example. Just assume the engineers designing the initial hook were not complete clueless idiots.

> The guys field testing took one look and knew it wouldn't work.

You have a hearsay, hindsight story (no offense to the author) that one person thought it wouldn't work.

And now we have a hindsight HN comment that they would have known it all along. I'm guessing the people who worked on it weren't idiots, though people seem to delight in supposing they are smarter than all the dumb people whose plans don't work out perfectly.

No offense taken. The observation of an instrumentation technician and an engineer (me) definitely counted for not much at all in the grand scheme of things. And we could have just as easily been proven wrong.

Yes, that's what I'm thinking.

Since you're the author: can you remember any cases where the person with "common sense" thought "this crap ain't gonna work" but it worked anyway? Surely people only remember those cases when common sense won, and selectively forget those where it didn't?

> can you remember any cases where the person with "common sense" thought "this crap ain't gonna work" but it worked anyway

I have one! Totally different field though. Cruise ships (and roro ferries) look sooo ungainly in water that regular people frequently ask how do they not just roll over. The Icon of the Seas goes 9 meter underwater and 20 stories over the water. It does not feel or look right. Yet it is right, and keeps upright :), because it does not have uniform density. The engines and machinery, and tanks at the bottom of it keeps the center of gravity low enough to make it stable.

The funny twist is that vehicle carrier ships also look unstable the same way and there the intuition is more correct. There have been multiple accidents where such ships capsized. But the intuition there is still not correct about the reasons why they flip over. (It is not that they don’t have enough draft, but due to free surface effects and the cargo destabilising).

For F-35 flight test specifically, nothing comes to mind. Perhaps I'm a victim of the forgetting you mention.

Reply on news.ycombinator.com