The 1950s were a time in computing where it wasn't a given that digital computing was clearly "better". We still hadn't developed methods of mass-producing reliable, fast, and cheap microelectronics and controllers. So for high-reliability applications, analog computing was THE solution.
In 1954, Rex Rice wrote this piece about preferring a simple plugboard as the means of programming a computer, versus any sort of abstraction with a programming language (https://dl.acm.org/doi/10.1145/1455270.1455272). So it was still very much up for debate, whether high-level programming languages were even the right solution for the problems being faced.
But I agree with you, our forefathers were simply geniuses to have figured out how to manipulate the physical world to produce mathematical computations. Early in his career, my dad had to disassemble and reverse-engineer some Soviet-made aerospace devices, and he still fondly recalls how superbly engineered and precise the Soviet devices were. I wish there was more information out there about Soviet computing, but the winners do write history after all.
It's interesting that you note the unreliability. I always assumed tubes were unreliable, but thought anything solid state (even those card based systems) would be "reliable enough" to start taking for granted.
But then you look at it and think Yeah, obviously they're not going to have MTBF times in the millions. It's going to be hundreds of hours - once a week, or maybe every few weeks between real hard crashes.
I've wanted to add such an indicator to my car's dash (I already added a boat compass, which I find quite useful and aesthetic). Unfortunately, electronic indicators of any kind are much more rare than vacuum powered ones or all-glass cockpits.
Asking just out of curiosity/ignorance. The author mentions that the F35 has a completely digital touchscreen to basically do anything on the aircraft (I assume). I can also image a powerful gun damaging it, then how does pilot manage if that screen stops working at all? Compare the same situation in the F4. The hit would only break/damage the instruments on that line of fire, correct? So in one case you would be totally screwed while in the other one you would partially lose some instruments, right? I must obviously not be taking into account something (or many things) for the F35, but in my mind having a 100% digital aircraft seems pretty scary.
The backup for the display is an integrated standby instrument system (ISIS), which combines several essential instruments into one small digital display. An ISIS typically has its own sensors and a battery backup, so it should stay operational even if the main display fails. https://en.wikipedia.org/wiki/Integrated_standby_instrument_...
Generally, if the cockpit is getting hit with damage to the instruments, there is a very good chance the pilot has also been injured or killed, and doesn't care about the instruments anymore.
In old gun fights (which just don't happen anymore), shots were likely to come from behind (so, they intersect the pilot) or the top (so, through the canopy if they're hitting the instruments). This has to do with the orientation both planes are probably in if one is shooting at the other. Go back farther and you get shots from the front, not from fighters (head-ons are very difficult to pull off outside of videogames) but from bomber tail gunners - very old planes from WWII even had bulletproof glass in front of the pilot for this reason. If the F35 has gotten into a gunfight, the pilot has fucked up, it's not a dogfighter and wasn't designed to be one.
Even nowadays, if the missile or flak pops next to the cockpit and has managed to damage the instruments, there is a very strong chance the shrapnel has also hurt the pilot to the point that they're not flying home that day. This is the most likely way for the F-35 to be damaged in the modern era.
There are obviously scenarios where the instrument panel gets damaged but the pilot is okay, but it's such a low probability scenario that they likely deemed it to be less harmful than the benefit they foresee in a glass cockpit.
Thanks for replying! As other mentioned I was missing/not considering the most important case that the pilot is assumed to be dead and that the plane is not supposed to receive such fire.
Can't speak for the F35, but for the fighter I work on we basically consider the pilot dead if you have shrapnel damage in the cockpit. For instance, the FCS is located behind the pilot. That being said, I would assume the F35 display being at least dual redundant (think two displays merged together, which can be done seamlessly) for flight safety reasons.
They're not just regular screens. They're highly hardened, redundant, specialized displays, it's a whole industry.
There are companies that make displays that have clear conductors over the screen so they can heat them so they can be used and maintain function even when on the deck of an aircraft carrier in the arctic.
There are companies that still make CRTs for specific military purposes.
These screens are safer, more reliable, and durable than the mechanical systems they replace.
Basic flight instruments almost always have a backup. In case of F-35 there's a small square screen in centre console which shows attitude indicator and flight parameters. Needless to say, if main screens are out you are turning around and looking for the nearest airport.
Depending on the fighter: redundant systems. Ie multiple independent Ring Laser Gyros, (viewable on multiple independent displays), backed up by analog "round dials" instruments.
I'd imagine the ejection system is going to be activated by traditional handles, and not a screen. Same with the basic flight controls; there's no reason to move to a touch screen throttle or flight stick.
to be fair isn't the purpose of the F35 fairly different since it's extremely reliant on stealth and beyond visual range engagements?;Instead of getting close enough to be gunned down, it is supposed to strike from so far away that the enemy wouldn't know it's there.
According to a paper on navigation sensors, commercial grade sensors have gyroscope drift of 0.1º/s (which is consistent with iPhone data), while navigation grade sensors have a drift of <0.01º/hour. I couldn't find specific numbers for the F-4's inertial navigation system, but I assume it is navigation grade. So the aircraft gyroscopes would be orders of magnitude better than a smartphone. For the azimuth, the F-4 used a flux valve compass, which must be much better than the relatively poor compass on a smartphone. Of course, the smartphone sensors are orders of magnitude cheaper and smaller.
This instrument is only an display that shows data coming from another device that does the actual measurements. One of the reasons why the threewire synchro interface is used is that it is surprisingly accurate as long as you don't care about the fact that it is “slow” by modern standards. The same interface was used to direct artillery and similar things that require significant accuracy to be effective.
Well this is just an indicator, the accuracy from the actual IMU would also need to be considered. The indicator itself probably isn’t the main source of inaccuracy once the IMU has drifted a bit.
Fun fact is these airplanes are still being used as the backbone of Iranian Airforce and the very same unit was being used before they upgraded the avionics a couple of years ago on some variants.
pretty awesome to see the engineering details involved! -thanks. as a software person I always wonder how they handle bugs and QA when building complex pieces of hardware like this
The strangest concept for modern software engineers is that it had to ship bug free and it could never be updated with firmware patches. Shipping under those constraints brings a certain level of focus not experienced in modern design.
My dad used to work on certifying, servicing and making custom instruments for planes, subs, prototypes of all kinds of that era (60s to mid-90s).
His “lab” was basically all about testing and simulating environments for the instruments. He had tons of sayings about not having room for error in his line of work. This is as close as you can get from “building bridges” and to this day I don’t think I have seen this level of attention to detail/perfection in any other profession.
His job involved electronical engineering , mechanical engineering and programming amongst other things, not to mention a deep knowledge of the physics of these environments.
Back then also the tools or source of information that were available to them were quite crude compared to what we have now.
His spare time was all about flying, pimping his ham radio gear with all kind of “home made” electronics, build antennas and messing with computers. I guess he’d qualify as a “Hacker” nowadays.
I think the key is that in those days you didn't launch a product until you were absolutely sure it was going to work well, it was prototyped and debugged before it was launched. At least that is the impression one get with classical tech, solid reliability.
Physical products require "test engineers" to design and run appropriate physical tests of products. It's an entire discipline worthy of study. Design for Six Sigma is a great place to start if you're ever interested in understanding ultra-high reliability applications.
Thanks for including ridiculously high res images.
And it amazes me how many analog tricks they used. Modern day would be a couple lines of code.
The 1950s were a time in computing where it wasn't a given that digital computing was clearly "better". We still hadn't developed methods of mass-producing reliable, fast, and cheap microelectronics and controllers. So for high-reliability applications, analog computing was THE solution.
In 1954, Rex Rice wrote this piece about preferring a simple plugboard as the means of programming a computer, versus any sort of abstraction with a programming language (https://dl.acm.org/doi/10.1145/1455270.1455272). So it was still very much up for debate, whether high-level programming languages were even the right solution for the problems being faced.
But I agree with you, our forefathers were simply geniuses to have figured out how to manipulate the physical world to produce mathematical computations. Early in his career, my dad had to disassemble and reverse-engineer some Soviet-made aerospace devices, and he still fondly recalls how superbly engineered and precise the Soviet devices were. I wish there was more information out there about Soviet computing, but the winners do write history after all.
It's interesting that you note the unreliability. I always assumed tubes were unreliable, but thought anything solid state (even those card based systems) would be "reliable enough" to start taking for granted.
But then you look at it and think Yeah, obviously they're not going to have MTBF times in the millions. It's going to be hundreds of hours - once a week, or maybe every few weeks between real hard crashes.
How would that change your behaviour.
I've wanted to add such an indicator to my car's dash (I already added a boat compass, which I find quite useful and aesthetic). Unfortunately, electronic indicators of any kind are much more rare than vacuum powered ones or all-glass cockpits.
Boat compass on the dash is awesome, I might have to borrow that. Any issue with interference from the vehicle itself?
What you need my friend is a ring-laser gyro.
Asking just out of curiosity/ignorance. The author mentions that the F35 has a completely digital touchscreen to basically do anything on the aircraft (I assume). I can also image a powerful gun damaging it, then how does pilot manage if that screen stops working at all? Compare the same situation in the F4. The hit would only break/damage the instruments on that line of fire, correct? So in one case you would be totally screwed while in the other one you would partially lose some instruments, right? I must obviously not be taking into account something (or many things) for the F35, but in my mind having a 100% digital aircraft seems pretty scary.
The backup for the display is an integrated standby instrument system (ISIS), which combines several essential instruments into one small digital display. An ISIS typically has its own sensors and a battery backup, so it should stay operational even if the main display fails. https://en.wikipedia.org/wiki/Integrated_standby_instrument_...
Generally, if the cockpit is getting hit with damage to the instruments, there is a very good chance the pilot has also been injured or killed, and doesn't care about the instruments anymore.
In old gun fights (which just don't happen anymore), shots were likely to come from behind (so, they intersect the pilot) or the top (so, through the canopy if they're hitting the instruments). This has to do with the orientation both planes are probably in if one is shooting at the other. Go back farther and you get shots from the front, not from fighters (head-ons are very difficult to pull off outside of videogames) but from bomber tail gunners - very old planes from WWII even had bulletproof glass in front of the pilot for this reason. If the F35 has gotten into a gunfight, the pilot has fucked up, it's not a dogfighter and wasn't designed to be one.
Even nowadays, if the missile or flak pops next to the cockpit and has managed to damage the instruments, there is a very strong chance the shrapnel has also hurt the pilot to the point that they're not flying home that day. This is the most likely way for the F-35 to be damaged in the modern era.
There are obviously scenarios where the instrument panel gets damaged but the pilot is okay, but it's such a low probability scenario that they likely deemed it to be less harmful than the benefit they foresee in a glass cockpit.
Thanks for replying! As other mentioned I was missing/not considering the most important case that the pilot is assumed to be dead and that the plane is not supposed to receive such fire.
Can't speak for the F35, but for the fighter I work on we basically consider the pilot dead if you have shrapnel damage in the cockpit. For instance, the FCS is located behind the pilot. That being said, I would assume the F35 display being at least dual redundant (think two displays merged together, which can be done seamlessly) for flight safety reasons.
They're not just regular screens. They're highly hardened, redundant, specialized displays, it's a whole industry.
There are companies that make displays that have clear conductors over the screen so they can heat them so they can be used and maintain function even when on the deck of an aircraft carrier in the arctic.
There are companies that still make CRTs for specific military purposes.
These screens are safer, more reliable, and durable than the mechanical systems they replace.
Basic flight instruments almost always have a backup. In case of F-35 there's a small square screen in centre console which shows attitude indicator and flight parameters. Needless to say, if main screens are out you are turning around and looking for the nearest airport.
Depending on the fighter: redundant systems. Ie multiple independent Ring Laser Gyros, (viewable on multiple independent displays), backed up by analog "round dials" instruments.
I'd imagine the ejection system is going to be activated by traditional handles, and not a screen. Same with the basic flight controls; there's no reason to move to a touch screen throttle or flight stick.
The F35 is not meant to be a dogfighter. If it has gotten shot such that the control screen in unusable, something else has gone wrong.
It's a high performance fighter with a gun and SRMs, so...
to be fair isn't the purpose of the F35 fairly different since it's extremely reliant on stealth and beyond visual range engagements?;Instead of getting close enough to be gunned down, it is supposed to strike from so far away that the enemy wouldn't know it's there.
If you project a line that crosses an aircraft instrument panel it's hard to imagine a line that didn't also go through pilot's body.
Author here if there are any questions...
How accurate you think this instrument was compared to the ic based sensors found in your typical smartphone nowadays?
According to a paper on navigation sensors, commercial grade sensors have gyroscope drift of 0.1º/s (which is consistent with iPhone data), while navigation grade sensors have a drift of <0.01º/hour. I couldn't find specific numbers for the F-4's inertial navigation system, but I assume it is navigation grade. So the aircraft gyroscopes would be orders of magnitude better than a smartphone. For the azimuth, the F-4 used a flux valve compass, which must be much better than the relatively poor compass on a smartphone. Of course, the smartphone sensors are orders of magnitude cheaper and smaller.
[1] https://doi.org/10.1186/s43020-019-0001-5
This instrument is only an display that shows data coming from another device that does the actual measurements. One of the reasons why the threewire synchro interface is used is that it is surprisingly accurate as long as you don't care about the fact that it is “slow” by modern standards. The same interface was used to direct artillery and similar things that require significant accuracy to be effective.
Well this is just an indicator, the accuracy from the actual IMU would also need to be considered. The indicator itself probably isn’t the main source of inaccuracy once the IMU has drifted a bit.
Fun fact is these airplanes are still being used as the backbone of Iranian Airforce and the very same unit was being used before they upgraded the avionics a couple of years ago on some variants.
I bet the engineers responsible for this would be so stoked that someone figured out how they solved all these problems.
pretty awesome to see the engineering details involved! -thanks. as a software person I always wonder how they handle bugs and QA when building complex pieces of hardware like this
The strangest concept for modern software engineers is that it had to ship bug free and it could never be updated with firmware patches. Shipping under those constraints brings a certain level of focus not experienced in modern design.
My dad used to work on certifying, servicing and making custom instruments for planes, subs, prototypes of all kinds of that era (60s to mid-90s).
His “lab” was basically all about testing and simulating environments for the instruments. He had tons of sayings about not having room for error in his line of work. This is as close as you can get from “building bridges” and to this day I don’t think I have seen this level of attention to detail/perfection in any other profession.
His job involved electronical engineering , mechanical engineering and programming amongst other things, not to mention a deep knowledge of the physics of these environments.
Back then also the tools or source of information that were available to them were quite crude compared to what we have now.
His spare time was all about flying, pimping his ham radio gear with all kind of “home made” electronics, build antennas and messing with computers. I guess he’d qualify as a “Hacker” nowadays.
I think the key is that in those days you didn't launch a product until you were absolutely sure it was going to work well, it was prototyped and debugged before it was launched. At least that is the impression one get with classical tech, solid reliability.
So basically like designing and building a bridge?
Physical products require "test engineers" to design and run appropriate physical tests of products. It's an entire discipline worthy of study. Design for Six Sigma is a great place to start if you're ever interested in understanding ultra-high reliability applications.
https://www.youtube.com/watch?v=_g6UswiRCF0
kens@ is a treasure we do not deserve.