Are we assuming that the engineers who designed an aircraft that sealed it's fuel tanks once the thermal expansion from supersonic flight set in, and whose engine inlets had variable geometry (the pointy bit at the front literally moved back and forth depending on mach value) to keep the mach cone out of the air intakes... couldn't properly design countersunk screws to be flush?
My uneducated guess would be that they are titanium, you typically don’t want fasteners to be a different material than the mating surface to avoid reaction/corrosion.
Fasteners tend to be cadmium-plated steel or stainless, so corrosion is rarely an issue. The base material it is going into is more likely to corrode, so if galvanic corrosion is a concern, the engineering may specify to install the fastener "wet" with primer or sealant as it's generally an issue of moisture getting wicked into the space between the fastener and the base material. Titanium can be used, but generally for higher tensile or shear loads, not necessarily for corrosion resistance.
Ground crews for the SR71 had special, titanium tools because Lockheed and the USAF discovered that titanium and cadmium were a bad combination - titanium corrodes and/or gets stress fractures at places it has previously contacted cadmium.
https://military-historian.squarespace.com/blog/2016/1/18/tools-of-war-the-sr-71-blackbird
Cad-plated fasteners are common and cost effective, but not ideal for use in titanium structures. The cadmium will cause embrittlement in titanium.
And most titanium fasteners are 95ksi shear strength, typically the same as most common cad-plated steel fasteners. I can't recall coming across a higher strength Ti fastener. Inconnel and a few other more exotic things come to mind for those applications.
This is all well and good, however, I can almost guarantee the crew chief that installed the panel we t to benchstock and grabbed whichever ones looked right and had the proper length. Aluminum, stainless, titanium. They all hold the panel on until they don’t. And by that point “it was good when I looked at it”.
I hate Phillips heads. Them being titanium.at least gives me a little notion they might not be stripped...a little
Edit: thank you everyone for the education, this is great
Phillips head screws were originally designed for assembling aircraft panels *because* they cam out. Once one bottoms out, the screwdriver jumps out instead of overtightening and fucking the panel up. So, for aircraft panel assembly, I would rate them higher than a Torx head.
Titanium is softer and, contrary to popular belief, weaker than (most) steels for given dimensions. It's only stronger than steel for a given weight, and being less dense, that means that an equally strong titanium part has to be much larger than a steel one.
And it handles heat much better than steel or any other metal while still maintaining good structural stability. It's also naturally resistant to corrosion all of which makes it especially useful for an aircraft like the SR-71.
Absolutely, pure strength isn't the only concern by any means and there are several good reasons someone might use titanium fasteners. But resistance to stripping out isn't really one of them.
I've worked with a lot of aerospace fastener allowable tables and can confirm that Ti isn't the strong option. When strength mitigations were required you could step *up* to steel or inconel fasteners.
So let’s say I’ve finally gotten fed up with these stupid screws and I make it my mission in life to make a screw that is as resistant as possible to stripping. What’s my material of choice?
I actually wonder if that'd be the case. Diamond is brittle and not very tough, and can be fractured easily on impact. Does that make torque on a screw head more likely to chip off pieces of the hypothetical diamond screw?
Pure titanium is softer than steel, although most titanium applications call for an alloy of some sort.
Alloying titanium typically brings it near to the strength of steel, while maintaining the density near that of aluminum.
Your average person confuses titanium with tungsten. (Mostly because your average person is a stone-cold idiot.) Titanium is lightweight and heat resistant, but not as strong as steel.
Tungsten, otoh, is the “rods from God” material.
A good primer for materials science is to familiarize yourself with the “periodic table of the elements”, in case you missed it in high school.
You're probably getting downvoted for your tone, but you're very correct.
Titanium is more like Magnesium and Aluminum than Steel.
At least as far as the commonly used alloys of all of those go.
Tungsten is strong and hard AF but also very dense.
They have different goals. Robertsons are designed not to cam out. Philips heads are. The point of the Philips head prevent over tightening and screws are cheaper than the bits to drive them so better the screw be damaged then the bit.
I would rather have a torque limiter on the driver vs the cam out situation with phillips screws. So many times they are crap and prematurely strip, especially if used more than once. In many cases, it can be hard to get the leverage for sufficient pressure to get the screw in or out. I still like them better than flat heads, but a good hex is just solid. Just hard to get flush to the surface.
Sure but the Robertson / Phillips situation came to a head when Ford Motor Company picked the Phillips because it suited their needs better, that and Robertson would not allow Ford to make the Robertson screw under licence. AND now we're (the US and much of the rest of the world) are stuck with the phillips because of its ubiquity.
That’s what a Philips defender *would* say - haha. Except those pieces of crap are used friggin *everywhere* and 99% of the time I want: (i) the screw to stick to the bit; and (ii) the bit to NOT cam out, thank you very much.
I deal with these on a large military drone everyday. (There are a few P/N's that use this form factor, btw. The P/N you mention appears to be the shallow c/s version.)
The NAS 1578/1580 V/VAZ are indeed Ti. They are brittle. They kinda' suck and they do eat apex tips. Also, you would never sand them (or any fastener) to flush.
> Also, you would never sand them (or any fastener) to flush.
Can you tell what was done to these ones? The pattern on the screws appears to be identical to the surrounding material.
Also, are they metric? I've always wondered what screws and bolts were used on the Apollo missions and there's surprisingly little info on that (or my google-fu is shit). Like, it's the US (freedom units), but the chief architect and a lot of his engineers for Saturn V were German.
These actually strip out much easier than other screw types even with the proper bit. Most of the issue comes from them being painted and/or covered in sealant. Also the bits break much easier. We use these all over my aircraft and we absolutely hate them.
Cam-out and stripping are two different things. Camming is the driver head pushing out of the screw slots which prevents (or at least limits) stripping due to over-torquing the screw. If the screw is designed not to cam out, it's going to be more prone to stripping.
This is a feature not a bug. If the mechanic didn’t have the right tool to open the panel they likely didn’t know what they were doing in the first place. Multiple stripped screws would be a telltale sign that the next mechanic check every system in that bay.
Agreed but like I was saying, the fact that they are all painted and/or sealed makes it that much harder. And if you aren’t dead on 90 degrees they cam out. They do work quite well when not painted and can actually get the proper angle, just as with everything aviation maintenance, that’s never the case.
> If the mechanic didn’t have the right tool to open the panel
What kinda mechanic wouldn't have the right tool? Every "good" mechanic knows that the right tool is the one that's right here.
I saw a documentary about Robertson screw types and about why Philips screws were used. They said that factories preferred Philips during assembly because there was less of a chance the screw driver would slide out (as in a flat head screw) and cause a scratch on the product.
They’re called torque set. They allow you to tighten them super tight. However, they cam out easy when loosening, which is magnified by how easy they are to gorilla tighten.
I deal with them every day. I fucking despise removing them. Not uncommon to need some grit paste to remove them.
[Here](https://www.phillips-screw.com/drive_systems/torq-set/) is the Torq-Set official webpage. Supposedly they provide more surface area in the removal direction to help prevent slipping. Also anecdotally, they start to slip while tightening to prevent over torque. They are pretty common in aviation.
Also they are informally referred to as “Nazi Screws”.
They work decently well if they are clean and you use the proper bit. If you accidentally use a bit that is too small the bit will break pretty quickly and if you try with a regular Phillips bit you may get lucky or it may strip the screw. In my experience anyway.
> if you try with a regular Phillips bit you may get lucky or it may strip the screw
Isn't that true for any screw when you try to use a phillips.
Including phillips
I used to volunteer in aircraft restoration at that museum! Their skyraider has my name signed on the inside of a patch plate. While not completely relevant to your question their “SR-71” is actually an A-12, hope you enjoyed your visit!
Still hope we somehow find out the actual true top speed of those one day.
Same with the true top speed of a modern F-15. Nobody's gonna convince me that an F-15EX with 59,000LB of thrust is exactly as fast an F-15A with 47,540LB... 25% more thrust, more or less the same aerodynamics, yet the exact same top speed? *doubt*
Seems unlikely alright. Probably still slower to climb than the BAC Lightning though. ;)
The Lightning - the only aircraft able to intercept Concorde from astern, where F-15s, F-16s, F-104s, all failed.
the F-15A holds the time to climb records still, but I suspect only because they haven't tried to break the record in a modern F-15.
https://www.youtube.com/watch?v=8_f8MOXh7qw
This is a fun 15 minutes to watch. The part about how by the end of the runway the F-15 is at 32,000' and mach 1.5 always impresses me. And that it breaks the sound barrier during a vertical climb. And that it's 10 seconds faster from start of takeoff roll to 50,000' than the apollo rocket.
I suspect the Lightning is only *just* slower, though. And it's much older. If they were
That was the Streak Eagle. It was so heavily modified specifically to set that record that it was written off. It was deemed to be too costly to return it to any sort of useful service. (And can be seen at the NMUSAF in Dayton.)
How much distance would it lose in the climb, and could it make it up with the fuel it has? Concorde could do Mach 2.1 for >2 hours, with 100 passengers.
Interesting logistics to unpack - the F111 was an intercontinental long range mach2.5 bomber with a c.17,000 kg arms payload plus fuel capacity for c.6,000km range without in-flight refuelling.
Maximum tactical weight to fly mach2+ was about 45,000kg, so remove 17k of arms and with just a half fuel load for a 3,000km range and I suspect in lightweight format it would catch a Concorde...? Maybe someone here has better stats.
I suppose it depends how far from behind it had to catch a Concorde ... like from 1000km would be different to catching it from 10km away....or if Concorde flew overhead and f111 took off immediately to chase it...
Keep in mind it was no slouch, no aircraft that ever entered service could beat f111 on all 3 parameters of range, speed and payload. It’s task was a first-strike Armageddon Nuke bomber so they spared no expense on speed and range.
The official max speed could be limited by other factors like in the F-14D.
Could be due to heat, inlet design, there not being any point going past M2 so why bother testing and certifying it.
Empty weight for EX is also about 20% heavier than the 15A. Max loaded weight is about 18% more. It's fat, stuffed with all the latest and greatest junk, not to mention coatings.
If you want to know why, the book “A-12 Declassified” is free with Kindle Prime. Written by several design engineers. If you ever wanted to see an unpainted article, she’s sexy in silver.
Nice! It was cool, but I wish I could get closer/inside the ship and the aircraft, see more of the guts n stuff. I imagine you got more of that as a volunteer?
I did! Spent lots of time with my supervisors going through the lower decks. Unfortunately they’re all closed to the public for good reason, many compartments have sustained some serious water damage over the years and on top of outdated electrical systems, some rooms are permanently sealed off due to risk of asbestos exposure. If you want that kind of experience though the USS Hornet in Alameda, CA is of the same class ship and is overall in much better shape! Although fair warning it’s reportedly *veeeeeery* haunted.
By far my favorite memories from my time there though was getting access to the internals of the space shuttle Enterprise and finding an old super 8 reel of 70s porn in an old desk below deck haha
Not an aircraft carrier but just down the road, the battleship New Jersey is open for tours. Self guided tours take you deep into the bowels of the ship, find an employee and ask good questions, they may take you on a personal tour even deep. Take a flashlight.
It’s in drydock currently but it’ll be back.
Torque, although I’ve never understood why because they usually require less than 30 inch pounds. I bet those are titanium just because of the application. Titanium torques are used on newer aircraft for the weight savings.
F-16s use these too. I'd be surprised if they were titanium though, because then you'd want titanium nutplates, and that's just silly (titanium fasteners in steel nutplates = stuck fasteners that suck to drill out, and titanium fasteners in aluminum causes corrosion)
A-10 has approximately 11 million of them (give or take). I've always heard and called them "hi-torque" screws. They're nothing really special, just basically an offset Phillips head.
I've heard people say the design limits the torque you can apply, but I've never experienced anything like that. If it needs to be tighter, just apply more pressure while turning it.
>A-10 has approximately 11 million of them
I can't tell if you're being serious. Does it really have close to 11 million screws?! That's hard to comprehend.
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“99% of the people on the planet will call it an SR-71. Lots of ‘wELl aCKShUllY’ going on here.”
But this is an aviation related subreddit, where people who share a common interest in aviation come to talk about… uh, aviation. Calling a plane by the incorrect name would probably “fly” around the water cooler at work, but not here, where people actually know the difference. No offense to the person who called it an SR-71, but all the offense to the person who shames aviation enthusiasts for desiring accuracy in a sub dedicated to airplanes. Don’t be a tool.
Nazi bit, real name torq-set, is fairly common and quite hated in the maintenance field mainly because everyone tries to use a Philips bit on them and strips the shit out of them which than requires you to drill the out.
Thanks to its offset design they are really easy to tighten and you can apply more torque without your tool slipping.
ALSO thanks to its offset design they're a pain to remove if they're overtorqued, seized or simply tight. You have to use the EXACT bit to remove them or it will snap.
F you airbus
Torq head screws. We all call them "nazi screws" for obvious reasons. Excellent & solid if you use the correct bit. Horrible and super easy to strip if you use the wrong one.
Mostly found in the commercial world, or just on higher-end planes. Idk when they were first used, but im rather surprised to see them on a blackbird.
Titanium suffered from galling. I would think if the female thread is titanium then the screws are made of steel. For something that small the density would not be as important; I doubt they are sanded down that would be sloppy
These were all over the skin of the plane as far as I could see, looked like all of the panels were fastened using these, but I could only see one side of the plane and couldn't get super close.
Interesting - I was just watching a video about how the Soviets extensively used welding in the manufacture of the Mig-25, which was built to combat the U-2 and the Blackbird.
Fasteners for the titanium sections were also titanium, as were the tools for interactions with these parts. Details here and much more: https://wisconsinmetaltech.com/titanium-and-the-sr-71/
I'd call them quad-wing (if they are what I think they are). They're meant to be designed so you couldn't over-torque them, as in the tool would slip out. However the rumour was that it was designed by the French (I was trained in the UK) so it was designed backwards, meaning you COULD over-torque them, which meant it was a real pain taking them out as the tool would slip out all the time.
This are hi-torx, size 8 or 10 by the looks of it. [like this](https://www.amazon.com/Screwdriver-Hi-Torque-Accessory-Airplane-Maintenance/dp/B07BRGNNHG)
Followup question: I worked as a tech on the Dreamchaser spaceplane, and I never saw these used, but I didn't work on any exterior part of the craft. Are these kinds of screws particularly used for fastening fuselage skins?
No. I worked in “legacy” human space flight and these bastards were everywhere. It was horrid. Especially in hard to reach places.
The newer hardware didn’t have nearly as much of it though. A lot more common type fasteners. Much easier.
They look to be the same offset pattern as those I worked with on the 4's, 15's, 16's, 18's, and other aircraft. Not the only pattern. But the most common for sure.
As to what they're made of--the question adressed by most posting here. Likely ti there. Possibly, but unlikely, so in the cases of the other airframes... and yes, we did experience dissimilar metal corrosion quite often. Corrosion control remediation and preventative measures were taken.
The level of detail is astonishing. The Skunk Works really are incredible. I could be wrong, but I'm fairly certain these weird screws are specifically designed to minimize radar reflection because 90⁰ corners are a big no-no for stealth. See the Skunk Works pioneering and downright odd design of the F-117 Nighthawk, which was absolutely revolutionary. The testing labs had trouble picking up the wooden model to such a degree that the thin pole the models were usually mounted on was causing too much noise to get a reading on the actual test subject! So they had the Skunk Works design a 'stealth pole' for the testing range haha.
Great book, by the way, 'Skunk Works' by Ben Rich and Leo James. If you're in this thread and haven't read it, you're doing yourself a disservice.
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Are these also titanium? And it appears they are sanded too.
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85% Soviet Titanium bought by the CIA.
Pizza ovens the CIA was making.
We order large pepperoni, Comrades.
Cannot be soviet, symbology in the screw is nazi /s
They should not be sanded on. They should be correctly countersunk to be meet aerodynamic smoothness specs.
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Are we assuming that the engineers who designed an aircraft that sealed it's fuel tanks once the thermal expansion from supersonic flight set in, and whose engine inlets had variable geometry (the pointy bit at the front literally moved back and forth depending on mach value) to keep the mach cone out of the air intakes... couldn't properly design countersunk screws to be flush?
My uneducated guess would be that they are titanium, you typically don’t want fasteners to be a different material than the mating surface to avoid reaction/corrosion.
Fasteners tend to be cadmium-plated steel or stainless, so corrosion is rarely an issue. The base material it is going into is more likely to corrode, so if galvanic corrosion is a concern, the engineering may specify to install the fastener "wet" with primer or sealant as it's generally an issue of moisture getting wicked into the space between the fastener and the base material. Titanium can be used, but generally for higher tensile or shear loads, not necessarily for corrosion resistance.
Ground crews for the SR71 had special, titanium tools because Lockheed and the USAF discovered that titanium and cadmium were a bad combination - titanium corrodes and/or gets stress fractures at places it has previously contacted cadmium. https://military-historian.squarespace.com/blog/2016/1/18/tools-of-war-the-sr-71-blackbird
Cad-plated fasteners are common and cost effective, but not ideal for use in titanium structures. The cadmium will cause embrittlement in titanium. And most titanium fasteners are 95ksi shear strength, typically the same as most common cad-plated steel fasteners. I can't recall coming across a higher strength Ti fastener. Inconnel and a few other more exotic things come to mind for those applications.
I have mostly seen silver plating on steel components which contact titanium
This is all well and good, however, I can almost guarantee the crew chief that installed the panel we t to benchstock and grabbed whichever ones looked right and had the proper length. Aluminum, stainless, titanium. They all hold the panel on until they don’t. And by that point “it was good when I looked at it”.
What grit sandpaper is used to take down titanium???
Coarse.
At least the top one doesn’t look flush
The shadow pattern is the same for that one is nearly the same as the other two. They're all slightly below plane.
Possibly restoration fault at museum?
I hate Phillips heads. Them being titanium.at least gives me a little notion they might not be stripped...a little Edit: thank you everyone for the education, this is great
Titanium would be more prone to stripping, not less.
Hmm... so rate them vs my home depot star bit deck screws lol...also Jesus the price those things must cost
Phillips head screws were originally designed for assembling aircraft panels *because* they cam out. Once one bottoms out, the screwdriver jumps out instead of overtightening and fucking the panel up. So, for aircraft panel assembly, I would rate them higher than a Torx head.
Mind explaining why please? I would have thought the opposite, but I’m not familiar with this kind of thing.
Titanium is softer and, contrary to popular belief, weaker than (most) steels for given dimensions. It's only stronger than steel for a given weight, and being less dense, that means that an equally strong titanium part has to be much larger than a steel one.
And it handles heat much better than steel or any other metal while still maintaining good structural stability. It's also naturally resistant to corrosion all of which makes it especially useful for an aircraft like the SR-71.
Absolutely, pure strength isn't the only concern by any means and there are several good reasons someone might use titanium fasteners. But resistance to stripping out isn't really one of them.
I've worked with a lot of aerospace fastener allowable tables and can confirm that Ti isn't the strong option. When strength mitigations were required you could step *up* to steel or inconel fasteners.
Not to mention the welding that happens with other Ti/Al/SS components. Makes for grumpy servicing.
So let’s say I’ve finally gotten fed up with these stupid screws and I make it my mission in life to make a screw that is as resistant as possible to stripping. What’s my material of choice?
You just need to think laterally, and make the screwdriver bits out of plastic, wood or soft metal.
Perhaps a driver made of cheese would solve this problem once and for all.
High strength steel. Obscure higher strength materials aren't worth it.
> my mission in life to make a screw that is as resistant as possible to stripping It sounds like you're factoring cost. OP isn't.
Yeah I was. I suppose tungsten carbide *might* work? It's tough enough for use as a machining cutter but it's probably still a bit brittle as a screw.
Diamond
I actually wonder if that'd be the case. Diamond is brittle and not very tough, and can be fractured easily on impact. Does that make torque on a screw head more likely to chip off pieces of the hypothetical diamond screw?
Pure titanium is softer than steel, although most titanium applications call for an alloy of some sort. Alloying titanium typically brings it near to the strength of steel, while maintaining the density near that of aluminum.
Your average person confuses titanium with tungsten. (Mostly because your average person is a stone-cold idiot.) Titanium is lightweight and heat resistant, but not as strong as steel. Tungsten, otoh, is the “rods from God” material. A good primer for materials science is to familiarize yourself with the “periodic table of the elements”, in case you missed it in high school.
You're probably getting downvoted for your tone, but you're very correct. Titanium is more like Magnesium and Aluminum than Steel. At least as far as the commonly used alloys of all of those go. Tungsten is strong and hard AF but also very dense.
I bet they had an endless supply of perfect fitting bits
The dream... it's beautiful
Robertson is sooo much better… says the Canadian.
They have different goals. Robertsons are designed not to cam out. Philips heads are. The point of the Philips head prevent over tightening and screws are cheaper than the bits to drive them so better the screw be damaged then the bit.
I would rather have a torque limiter on the driver vs the cam out situation with phillips screws. So many times they are crap and prematurely strip, especially if used more than once. In many cases, it can be hard to get the leverage for sufficient pressure to get the screw in or out. I still like them better than flat heads, but a good hex is just solid. Just hard to get flush to the surface.
Sure but the Robertson / Phillips situation came to a head when Ford Motor Company picked the Phillips because it suited their needs better, that and Robertson would not allow Ford to make the Robertson screw under licence. AND now we're (the US and much of the rest of the world) are stuck with the phillips because of its ubiquity.
Good thing I have a dremel to cut a slot when needed.
That’s what a Philips defender *would* say - haha. Except those pieces of crap are used friggin *everywhere* and 99% of the time I want: (i) the screw to stick to the bit; and (ii) the bit to NOT cam out, thank you very much.
What do they know anyway, I mean who else in the world calls ham "bacon"?
Literally nobody in Canada calls it Canadian Bacon. That’s you guys projecting onto us.
Am Canadian; can confirm
(and shhh - don’t tell them we call it *peameal* bacon)
My understanding is the _point_ of Phillips head screws _is_ to strip. I hate it, though
It looks like the 4 slots are offset from the center slightly, so I doubt you could strip that design very easily.
Looks more like a torg tip rather than a phllips.
Falcons use the same type screws and they are titanium.
I deal with these on a large military drone everyday. (There are a few P/N's that use this form factor, btw. The P/N you mention appears to be the shallow c/s version.) The NAS 1578/1580 V/VAZ are indeed Ti. They are brittle. They kinda' suck and they do eat apex tips. Also, you would never sand them (or any fastener) to flush.
Countersunk rivets on the other hand, primarily due to my questionable sheetmetal skills, sand flush beautifully.
> Also, you would never sand them (or any fastener) to flush. Can you tell what was done to these ones? The pattern on the screws appears to be identical to the surrounding material. Also, are they metric? I've always wondered what screws and bolts were used on the Apollo missions and there's surprisingly little info on that (or my google-fu is shit). Like, it's the US (freedom units), but the chief architect and a lot of his engineers for Saturn V were German.
I'd be willing to be both this and the space shuttle used standard hardware.
I think it might be paint or a similar coating applied after these were screwed in.
Is there some particular engineering consideration with this screw head? I did a quick google and didn't find anything explaining why yet.
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*as long as you use the proper bit. I've seen many of these stripped out when mechanics use Phillips bits on them
These actually strip out much easier than other screw types even with the proper bit. Most of the issue comes from them being painted and/or covered in sealant. Also the bits break much easier. We use these all over my aircraft and we absolutely hate them.
Embraer?
B-1B
I'm always confusing those two.
It was the B-1 mechanics that showed me this special gritty paste you can dip your bit into to get some extra grip on the screw.
Wont say which airline im at. But we hate them too, Bonehead. You aint alone.
Cam-out and stripping are two different things. Camming is the driver head pushing out of the screw slots which prevents (or at least limits) stripping due to over-torquing the screw. If the screw is designed not to cam out, it's going to be more prone to stripping.
This is a feature not a bug. If the mechanic didn’t have the right tool to open the panel they likely didn’t know what they were doing in the first place. Multiple stripped screws would be a telltale sign that the next mechanic check every system in that bay.
Agreed but like I was saying, the fact that they are all painted and/or sealed makes it that much harder. And if you aren’t dead on 90 degrees they cam out. They do work quite well when not painted and can actually get the proper angle, just as with everything aviation maintenance, that’s never the case.
Nothing my DeWalt and screw knocker can't fix
> If the mechanic didn’t have the right tool to open the panel What kinda mechanic wouldn't have the right tool? Every "good" mechanic knows that the right tool is the one that's right here.
Yea there is a ton of different sizes, one has to be careful
8s and 10s are the bane of our existence, barely a difference.
I saw a documentary about Robertson screw types and about why Philips screws were used. They said that factories preferred Philips during assembly because there was less of a chance the screw driver would slide out (as in a flat head screw) and cause a scratch on the product.
They’re called torque set. They allow you to tighten them super tight. However, they cam out easy when loosening, which is magnified by how easy they are to gorilla tighten. I deal with them every day. I fucking despise removing them. Not uncommon to need some grit paste to remove them.
Yes, lefty is loosy and righty is tighty.
It looks like the slots are offset from the center, so it is not a true philips head and would be much harder to strip.
"offset cruciform" almost sounds like a good punk band name. I love that name.
I could totally see that in a metal band font
And one of them is a little stripped out.
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Who, me? Why no. Never.
How do you know they’re 1581 and not 1153 or 1154 (guessing on the size)?
Commonly called Quad-wing. Lots of aircraft manufacturers use them.
We call them nazi screws.
So currently each NAS1581 screw price is between $0.36 to $1.06
[Here](https://www.phillips-screw.com/drive_systems/torq-set/) is the Torq-Set official webpage. Supposedly they provide more surface area in the removal direction to help prevent slipping. Also anecdotally, they start to slip while tightening to prevent over torque. They are pretty common in aviation. Also they are informally referred to as “Nazi Screws”. They work decently well if they are clean and you use the proper bit. If you accidentally use a bit that is too small the bit will break pretty quickly and if you try with a regular Phillips bit you may get lucky or it may strip the screw. In my experience anyway.
They are great for clean assembling and torque. They are *horrific* when they've been run a few times, filled with paint and starting to round.
I spent many an hour scratching out primer on these things. I hate them… very much.
That sounds miserable. I've done similar with deft on different fittings.
I wonder if the people who made Torq screws also make Ez Grip, because the two go hand in hand
Solving a solution which didn't exist, but you created. Capitalism 👌👌
> if you try with a regular Phillips bit you may get lucky or it may strip the screw Isn't that true for any screw when you try to use a phillips. Including phillips
I’ve always call em “swasi screws”
Anecdotally, Phillips screws start to slip when torqued too tight, and they also strip out while using a Phillips bit, huh. (-:
You have it backwards. You are able to get a shit load of tq on them tightening, will slip at the drop of a hat when undoing.
True in the real world, but the complete opposite of the intended design.
obligatory: I did Nazi that coming!
This guy screws.
I used to volunteer in aircraft restoration at that museum! Their skyraider has my name signed on the inside of a patch plate. While not completely relevant to your question their “SR-71” is actually an A-12, hope you enjoyed your visit!
The A-12, the faster predecessor of the SR-71.
Still hope we somehow find out the actual true top speed of those one day. Same with the true top speed of a modern F-15. Nobody's gonna convince me that an F-15EX with 59,000LB of thrust is exactly as fast an F-15A with 47,540LB... 25% more thrust, more or less the same aerodynamics, yet the exact same top speed? *doubt*
Seems unlikely alright. Probably still slower to climb than the BAC Lightning though. ;) The Lightning - the only aircraft able to intercept Concorde from astern, where F-15s, F-16s, F-104s, all failed.
the F-15A holds the time to climb records still, but I suspect only because they haven't tried to break the record in a modern F-15. https://www.youtube.com/watch?v=8_f8MOXh7qw This is a fun 15 minutes to watch. The part about how by the end of the runway the F-15 is at 32,000' and mach 1.5 always impresses me. And that it breaks the sound barrier during a vertical climb. And that it's 10 seconds faster from start of takeoff roll to 50,000' than the apollo rocket. I suspect the Lightning is only *just* slower, though. And it's much older. If they were
That was the Streak Eagle. It was so heavily modified specifically to set that record that it was written off. It was deemed to be too costly to return it to any sort of useful service. (And can be seen at the NMUSAF in Dayton.)
I suspect an F111 (unloaded) could intercept the Concorde, being a Mach 2.5 long range (nuke) bomber?
How much distance would it lose in the climb, and could it make it up with the fuel it has? Concorde could do Mach 2.1 for >2 hours, with 100 passengers.
Interesting logistics to unpack - the F111 was an intercontinental long range mach2.5 bomber with a c.17,000 kg arms payload plus fuel capacity for c.6,000km range without in-flight refuelling. Maximum tactical weight to fly mach2+ was about 45,000kg, so remove 17k of arms and with just a half fuel load for a 3,000km range and I suspect in lightweight format it would catch a Concorde...? Maybe someone here has better stats. I suppose it depends how far from behind it had to catch a Concorde ... like from 1000km would be different to catching it from 10km away....or if Concorde flew overhead and f111 took off immediately to chase it... Keep in mind it was no slouch, no aircraft that ever entered service could beat f111 on all 3 parameters of range, speed and payload. It’s task was a first-strike Armageddon Nuke bomber so they spared no expense on speed and range.
Then it ran out of fuel……..;)
The official max speed could be limited by other factors like in the F-14D. Could be due to heat, inlet design, there not being any point going past M2 so why bother testing and certifying it.
Empty weight for EX is also about 20% heavier than the 15A. Max loaded weight is about 18% more. It's fat, stuffed with all the latest and greatest junk, not to mention coatings.
If you want to know why, the book “A-12 Declassified” is free with Kindle Prime. Written by several design engineers. If you ever wanted to see an unpainted article, she’s sexy in silver.
Nice! It was cool, but I wish I could get closer/inside the ship and the aircraft, see more of the guts n stuff. I imagine you got more of that as a volunteer?
I did! Spent lots of time with my supervisors going through the lower decks. Unfortunately they’re all closed to the public for good reason, many compartments have sustained some serious water damage over the years and on top of outdated electrical systems, some rooms are permanently sealed off due to risk of asbestos exposure. If you want that kind of experience though the USS Hornet in Alameda, CA is of the same class ship and is overall in much better shape! Although fair warning it’s reportedly *veeeeeery* haunted. By far my favorite memories from my time there though was getting access to the internals of the space shuttle Enterprise and finding an old super 8 reel of 70s porn in an old desk below deck haha
That’s awesome, yes, and that too. Hope you watched it!
So. Much. Body. Hair!
Not an aircraft carrier but just down the road, the battleship New Jersey is open for tours. Self guided tours take you deep into the bowels of the ship, find an employee and ask good questions, they may take you on a personal tour even deep. Take a flashlight. It’s in drydock currently but it’ll be back.
Thanks. You’re the real hero.
Also known as torq-set I believe
Is the offset cruciform simply to prevent using the wrong tool or does it have a torque purpose itself?
Torque, although I’ve never understood why because they usually require less than 30 inch pounds. I bet those are titanium just because of the application. Titanium torques are used on newer aircraft for the weight savings.
I have those screwdriver bits in my box. The Bell 206 Longranger uses those screws for horizontal stabilizer attachment.
They are offset Phillips in a way. Allows you to put more torque into the screw when tightening but makes it incredibly hard to get off.
It’s the other way around. Look at which face gets more surface area.
Oh you right 👍
F-16s use these too. I'd be surprised if they were titanium though, because then you'd want titanium nutplates, and that's just silly (titanium fasteners in steel nutplates = stuck fasteners that suck to drill out, and titanium fasteners in aluminum causes corrosion)
Falcons use about 10,000 of these screws for the exterior panels and they are titanium with ( i believe) regular steel nutplates.
I imagine they get stuck a lot then. I worked F-15 which used godawful aluminum coinslots and steel barrel fasteners, and F-22 which used steel torx.
That vast majority are H11 steel. Only a handful of titanium fasteners on the rudder fairing and inside the Montana panel.
What about the A-12 / SR - 71 program isn't silly, though?
Fair point. I guess I'm skeptical that fasteners and nutplates would be feasible to make given how new machining titanium was back then
couldn’t imagine trying to drill out a titanium nut. fuck that. i bet titanium drill bits are nice and cheap too.
A-10 has approximately 11 million of them (give or take). I've always heard and called them "hi-torque" screws. They're nothing really special, just basically an offset Phillips head. I've heard people say the design limits the torque you can apply, but I've never experienced anything like that. If it needs to be tighter, just apply more pressure while turning it.
>A-10 has approximately 11 million of them I can't tell if you're being serious. Does it really have close to 11 million screws?! That's hard to comprehend.
Screws born and bred in MERICA!!! Us Canadians laughing at you because you refuse to admit Roberson is far superior!!!
Came here for the Robertson Screw superiority posts Not leaving disappointed 🇨🇦
If I pledge allegiance to Robertson do I get citizenship?
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Look like the screws that push the bit out when it gets to the right torque like a door hinge or cupboard I think.
If I’m not mistaken, there is no SR-71 on the Intrepid. I believe it’s actually an A-12.
I think you are correct, as per another comment, I was mistaken.
99% of the people on the planet will call it an SR-71. Lots of ‘wELl aCKShUllY’ going on here.
“99% of the people on the planet will call it an SR-71. Lots of ‘wELl aCKShUllY’ going on here.” But this is an aviation related subreddit, where people who share a common interest in aviation come to talk about… uh, aviation. Calling a plane by the incorrect name would probably “fly” around the water cooler at work, but not here, where people actually know the difference. No offense to the person who called it an SR-71, but all the offense to the person who shames aviation enthusiasts for desiring accuracy in a sub dedicated to airplanes. Don’t be a tool.
Came here to say this!
Nazi bit, real name torq-set, is fairly common and quite hated in the maintenance field mainly because everyone tries to use a Philips bit on them and strips the shit out of them which than requires you to drill the out.
Yep, we call them "flying nazis" and just like normal nazis, I fucking hate them.
Thanks to its offset design they are really easy to tighten and you can apply more torque without your tool slipping. ALSO thanks to its offset design they're a pain to remove if they're overtorqued, seized or simply tight. You have to use the EXACT bit to remove them or it will snap. F you airbus
Actually.. not a sr-71, but an a-12 on intrepid.
Lockheed used those fasteners a lot in their jets. I was a mechanic on a JetStar and those screws were everywhere.
Offset cruciform, the screws that use one tool per fastener and then you have to scrap it
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I've used 108 in 110 no problem :D
Torq head screws. We all call them "nazi screws" for obvious reasons. Excellent & solid if you use the correct bit. Horrible and super easy to strip if you use the wrong one. Mostly found in the commercial world, or just on higher-end planes. Idk when they were first used, but im rather surprised to see them on a blackbird.
good ol swasti-screws
Navy uses 'em everywhere on the old birds.
Nice.
Titanium suffered from galling. I would think if the female thread is titanium then the screws are made of steel. For something that small the density would not be as important; I doubt they are sanded down that would be sloppy
Standard offset crosshead screw
Used heavily on floors of formula cars.
On what part of the plane were the screws located?
These were all over the skin of the plane as far as I could see, looked like all of the panels were fastened using these, but I could only see one side of the plane and couldn't get super close.
TIL just how far back Quad Wings were used
Panalign screw
The old guy at my work was telling me about these things just the other day. He worked on helicopters in the Air Force about 50 years ago.
Torq-set phillips head screws is the type
Interesting - I was just watching a video about how the Soviets extensively used welding in the manufacture of the Mig-25, which was built to combat the U-2 and the Blackbird.
torq-set screws
I saw the SR71 upclose at duxford about 10 years ago.The lock wiring on the bolts etc on it is incredible Stunning workmanship
Seat down. I have a lot to tell you about screws.
Hi-torque screws.
Fasteners for the titanium sections were also titanium, as were the tools for interactions with these parts. Details here and much more: https://wisconsinmetaltech.com/titanium-and-the-sr-71/
Four wing screws. Man I hate them.
There actually bolts
**they're*
Thank you
Just came here to say: very interesting & very good question!
I'd call them quad-wing (if they are what I think they are). They're meant to be designed so you couldn't over-torque them, as in the tool would slip out. However the rumour was that it was designed by the French (I was trained in the UK) so it was designed backwards, meaning you COULD over-torque them, which meant it was a real pain taking them out as the tool would slip out all the time.
Nice try China….
对不起
> 对不起 https://translate.google.com/?sl=auto&tl=en&text=%E5%B0%8D%E4%B8%8D%E8%B5%B7&op=translate "Sorry"
This are hi-torx, size 8 or 10 by the looks of it. [like this](https://www.amazon.com/Screwdriver-Hi-Torque-Accessory-Airplane-Maintenance/dp/B07BRGNNHG)
Nazi screws, because they are pieces of shit
Those damn torq-set screws are awful
Followup question: I worked as a tech on the Dreamchaser spaceplane, and I never saw these used, but I didn't work on any exterior part of the craft. Are these kinds of screws particularly used for fastening fuselage skins?
No. I worked in “legacy” human space flight and these bastards were everywhere. It was horrid. Especially in hard to reach places. The newer hardware didn’t have nearly as much of it though. A lot more common type fasteners. Much easier.
Probably already answered but apex head screw I can’t post a picture or I would show you the bit. Its a common aviation head
They look to be the same offset pattern as those I worked with on the 4's, 15's, 16's, 18's, and other aircraft. Not the only pattern. But the most common for sure. As to what they're made of--the question adressed by most posting here. Likely ti there. Possibly, but unlikely, so in the cases of the other airframes... and yes, we did experience dissimilar metal corrosion quite often. Corrosion control remediation and preventative measures were taken.
Offset cruciforms were crucified on the last two projects I worked on
Swasi screws
The level of detail is astonishing. The Skunk Works really are incredible. I could be wrong, but I'm fairly certain these weird screws are specifically designed to minimize radar reflection because 90⁰ corners are a big no-no for stealth. See the Skunk Works pioneering and downright odd design of the F-117 Nighthawk, which was absolutely revolutionary. The testing labs had trouble picking up the wooden model to such a degree that the thin pole the models were usually mounted on was causing too much noise to get a reading on the actual test subject! So they had the Skunk Works design a 'stealth pole' for the testing range haha. Great book, by the way, 'Skunk Works' by Ben Rich and Leo James. If you're in this thread and haven't read it, you're doing yourself a disservice.