Jesus nut | Hacker News Reader

Jesus nut

en.wikipedia.org

209 pointsBoogie_Man93 comments

Not to be confused with “Jesus Code”. Jesus code is any code written in a way that only the author and god (Jesus) would know how it works. That is until inevitably the author forgets. Leaving Jesus as the only source of reference.

It is believed that Jesus Code is the reason the second coming of Christ has not yet occurred. As Jesus would be flooded with support requests, jira tickets, and zoom meetings. (Some people believe the modern SDLC to be the devil’s way of keeping Jesus from coming.)

I briefly trained as a helicopter pilot. We do refer to it as the Jesus nut.

Bit of trivia: the bigger danger to helicopters is actually the rotor slowing down too much. If that happens, the rotor will fold. Yes, centrifugal force is the major force keeping rotors in one piece.

So lose your engine, and you must slam the collective down to keep rotor speed. (Nit: higher energy rotors give you more time.)

Are you saying the rotors will fold and bend upwards too far due to wind resistance?

ASCII diagram (the "o" is the j-nut):

  |         |
   \.__o__./

Due to lack of centrifugal force tensioning the blades. Yes, the will fold up like in cartoons.

Neat. Apparently it's called coning. https://en.wikipedia.org/wiki/Coning

> The tips of the rotor blades move faster through the air than the parts of the blades near the hub, so they generate more lift, which pushes the tips of the blades upwards, resulting in a slight cone shape to the rotor disc. This is balanced by centrifugal force. If rotor RPM drops too low, the rotor blades fold up with no chance of recovery.

> Rotors are typically designed with washout (twist) so that lift is relatively uniform along the blades. However, because lift increases quadratically with airspeed, coning still occurs at higher RPMs.

> Some helicopters such as the Bell UH-1 Iroquois are designed with "pre-coned" blades, which are curved downwards but lay more flat in flight.

But don't slam the cyclic down too quickly, otherwise you'll get a "mast bump"... which is a nice way of saying "the main rotor just cut the helicopter's tail in half". This also doesn't end well.

Good ol' Robinson Safety Notice SN-11:

https://robinsonheli.com/wp-content/uploads/2015/12/rhc_sn11...

(Though it does note that this scenario doesn't apply to an autorotation entry on engine loss, so I suppose you're okay in this example. Still terrifying though!)

That's the cyclic, not the collective.

Oh right, thanks! Good catch. :)

I just watched a vid about mast bump. It's not the rotor cutting off the tail, it's the mechanical linkage hitting the mast because the rotor has been unloaded and the collective .... something. Heli's are complicated.

Yep.

And yes, they are complicated.

Boy, is it a rush when you get good enough to fly one by feel.

I have a good friend who used to be an instructor, mechanic, and pilot. He was type rated in a ton of things, but refused to fly Robinson helicopters, ever.

Edit/Append: He explained because the rotor turns the opposite direction of most of the other helicopters he flew, his instincts would get him killed.

I'm not sure I agree with him.

Yes, Robinsons are known for mast bumping. On the other hand, they have the best tail rotor authority.

Ever pray to Jesus?

To your knowledge, has one of these nuts ever actually failed? That thing looks substantial.

Not to my knowledge, at least in the US.

All aircraft in the US have a manufacturer-decided, and FAA-approved max amount of time between overhauls, and such overhauls are so thorough as to make the aircraft new again. (Sometimes, they even change enough things that the aircraft has to go through airworthiness tests again.)

These overhauls would definitely replace the Jesus nut if there's any hint of problems.

Here's an article from 1975 claiming that the Jesus nut came off the main rotor of an OH-6, causing two fatalities: https://www.google.com/books/edition/The_MAC_Flyer/jBXi6uK1P...

Not a jesus nut failure, but some versions of the Super Puma had a gearbox failure mode that caused several accidents with rotor separation from the helicopter. For example this one that led to grounding of the EC225 and several related models:

https://en.wikipedia.org/wiki/CHC_Helikopter_Service_Flight_...

The wikipedia article has a link to an accident investigation report where unfortunately it was not put back onto the craft after maintenance.

Reminded me of the Jesus Clip.

> The term "Jesus clip" is a comical reference given to it due to its tendency to come loose and launch itself at high speed while removing or installing it, often leading to the remark "Oh Jesus, where did it go?"

https://en.wikipedia.org/wiki/Circlip

so. many. times.

This is what I was expecting when I clicked on the link. They really seem to almost always shoot off, especially if you don't have the special tool.

Some hang gliders have a Jesus clip at the top, holding all the wire wing struts to the frame.

Old kite surfers had a Jesus rope, that you pulled to collapse the canopy and stop you flying away in a gust.

Only in some helicopters. More of a trivia term than anything engineers reference. Source: was a helicopter stress analyst for 7 years on military and civil models.

https://i.pinimg.com/736x/4a/d0/d6/4ad0d68003a6d213e0a56f9b4... - CH-53K, No jesus nut

https://www.copters.com/mech/pictures/r22_head.jpg - R22, also none

Is this a "New v Old" thing or "cheap v expensive" thing? Or is it related to the task the helio is performing?

Mostly new vs. old. I'd guess that it's like Vietnam-era trivia for certain Bell models. I've never heard an engineer say "jesus nut" because it's just not a thing anymore.

Bell 206s, still used today, have retaining bolts. And while I don't know what the engineers call things, pilots certainly do call them Jesus nuts.

That first picture is absolutely fascinating. I knew that helicopters are complex, but wow.

I have heard that the rotor head on a ch-53 weighs more than an entire huey(uh-1).

update: I was unable to find any evidence for the rotor head story, but while looking I found this page full of -53 trivia and I wanted to share it.

https://sikorskyarchives.com/home/sikorsky-product-history/h...

I'd believe it. These things are huge. Also a single main rotor blade costs $500k.

When I was younger and rode motorcycles with my friends, we cast derision on the new trend of "Jesus Box" design, where any electrical issue meant buying a new, expensive black box that only Jesus could fix. No one with self respect would buy one, what if something failed out bush?

A decade later we all realised that the new bikes were insanely reliable, and never had random electrical issues in the rain.

I love it! Clearly related to the Jesus handle [1] but way more severe because helicopter.

[1]: https://www.urbandictionary.com/define.php?term=jesus%20hand...

lol! that reminded me, my HS friend, as urban dictionary says, called it the "oh shit handle". Some cars didn't have the handle, so the arm-in-front-on-dash was the "oh fuck brace"... of course, this was before passenger-side airbags everywhere.

ah yes, the 'oh shit handle'. i still call them that!

When I was learning to work in HP Laserjet IIP and IIIE (and 4SI) printers (I'm old...) I was taught that those little circlips that hold things were called "jesus clips" because they fly off into the nothing, never to be seen again, and the guy working on it usually yells out "JESUS!" in frustration.

But the helicopter thing makes sense too.

The Wikipedia article actually has a mention of that too, in regards to a pin on a tank machine gun.

I’ve personally heard of a tiny device called the “fuck wrench”…

I learned that fixing bicycles.

Iirc, mechanical watch repairers have a type of putty they can lay across sprung components likely to fly off never to be seen again …

Yeah: https://www.amazon.co.uk/BERGEON-Bergeon-Professional-Cleani...

Just to add, Chickenhawk, as mentioned in tfa, is a great read if you're interested in helicopter flight, Vietnam Huey tactics and Vietnam R&R.

When I was younger, I helped sell small Robinson helicopters, etc like the R22, R44. Saw some getting assembled for sale, honestly hard to believe some people have so much trust in not only the Jesus Nut but in the people putting smaller personal aircraft together.

At a previous job we installed a pair of SD-WAN appliances that supposedly had high availability built in. Except there weren’t enough Ethernet ports on the appliance, so both the WAN connections had to go through a single switch. Of course we referred to it as the “Jesus switch”.

The related slang term Jesus pin refers to the lock pin used to secure the retaining nut. More generally, Jesus nut (or Jesus pin) has been used to refer to any component that is a single point of failure which results in catastrophic consequences, and the only thing left to do is, metaphorically speaking, pray to Jesus, hence the name.

What would be the equivalent in software engineering? Loosing your domain name?

Prod database on a single server with a single drive

...with no backups.

Without reliable restores.

FIFY

What part of "with no backups" didn't you understand?

:-)

Perhaps the part where "having backups which are unreliable/unrestorable" is _more_ dangerous than "being known to have no backups", because the former provides a false sense of security?

"Good companies test their backups. Great companies test their restores."

Learned that lesson the hard way a few decades ago.

And stored under the developer's desk.

with the power button lined up with where their shoe rests.

A CEO once got up on stage to announce an important new phone to the world's assembled press not knowing that the picture on the screen of the phone was coming from a PC in a bedroom closet and the developers were sweating like dogs as they watched the broadcast on the BBC. I shall say no more.

Who needs backup when you just rsync every 10 minutes?

Rsync?

MTBF on a WD Green is 1M hours, we’ll replace it at 900K and be golden…

OT: that's how i recognise French people anywhere ;) only one o for "losing"

Huh? That's an idiomatic error typical of native speakers. People who learn English as a second language tend to do much better on the "loose-lose" and "there-their-they're" kinds of errors

For what it's worth, in my experience the GP's comment rings true. I don't see many native English speakers making that mistake, and I do see lots of native French speakers making it.

> People who learn English as a second language tend to do much better on the "loose-lose" and "there-their-they're" kinds of errors

This sounds logical, but I am not sure about it. I certainly make much much more errors based on similar sounding words in English than on my native language. (I believe I make a TON of such errors in English, and almost none in my native language, but hard to tell.)

I can confirm that as a non native English speaker I don't make this kind of mistake often. I think spelling is easier for me because I first learned how the word is spelled and only later how to actually pronounce it? And i separate homonyms like they're/their in my head because they're very different words in my language.

Idiomatic error is "would of"

haha good catch

DNS

When using AWS for anything, pray for the health of us-east-01. When that region has problems the whole internet quakes with fear. You never know what's going to break.

I'm shocked at how true this is. A huge amount of software is only redundant by being hosted in mutiple parts of aws us east.

That's the funny part. It is spread around 'US East'. If anything catastrophic (or mundane) knocks out power/internet in that region it won't matter how many backups you have. It will bring down large parts of the internet.

That seems to indicate a problem with the decision making behind putting important things in only one region.

I'm happy if it goes down , nice excuse to not get any work done that day

I hear "bus factor" bandied about.

https://en.m.wikipedia.org/wiki/Bus_factor

Encrypting your data at rest and losing the key.

Jesus Undersea Cable?

An interesting question, what in software causes catastrophic issues when it's broke, but also designed as it should, like the Jesus nut is for a helicopter?

Obviously many systems have a single point of failure, and can result in lost productivity, but is that designed as it should, or cause catastrophic results like a helicopter crash?

Load balancer? Cluster coordinator? STONITH device

BGP

The term made it's way into climbing too for building anchors when trad-climbing. (traditional as opposed to sport climbing)

Hmm, for anchors, or for that first piece (or two) that would keep you off the deck or from falling on the belay anchor?

It’s the first piece off the belay

It's surprising most rotor mast designs don't include a nested secondary nut and don't use lockwire.

In Japan, motorcycle racing requires lockwire on almost everything. It's a shame helicopter safety engineering generally doesn't meet this basic standard. Although, in fairness, relying on a single spinny thing without an all operational envelope survival passive glide capability is itself inherently dangerous.

... maybe because lockwire wouldn't help in this situation?

The Jesus nut on a Huey and a cobra both include a secondary lock (looked like a single gear tooth) secured by a bolt and lock wire.

The nut was torqued to 3000 ft-lb so this was kind of superfluous. But it does show that the nut was torqued, witnessed, and wired.

Literally the second sentence says that the the Jesus nut is secured by a retaining pin.

Is there a single major redundant aspect in a (single-rotor) helicopter's ability to stay airborne?

I thought helicopters were so expensive because every part had to work and last, or else.

I guess it depends on what you mean by "major". Pumps, injectors, spark plugs, etc tend to be redundant. You have airspeed & altitude. None of this is really specific to rotorcraft, though.

> I thought helicopters were so expensive because every part had to work and last, or else.

Yes, but the key to why helicopters are expensive is that is that aviation is highly regulated by the government. Individual manufacturers, pilots, airlines, etc. don't get to decide what is "safe enough," they have to obey the standards set by the law. Adhering to the standards of the law requires a lot of process and paperwork.

...737 MAX begs to differ.

Just gaslight the regulator and produce the best selling airframe of all time.

What about Jesus Christ?

[stub for offtopicness]

Isn’t that the shortest sentence in the bible or something?

Close, shortest verse is: “Jesus wept”.

Famous among kids who once attended Sunday school programs that asked them to recite a bible verse each Sunday. First kid to go always takes that one.

Perhaps in an apocryphal book, or the novelization of The Last Temptation of Christ

I am so sorry, I have to flag this because seriously, but also

Amazing joke, I lol'd, fantastic work sir

amen to that!

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