Bendix Air Data Computer - Part 1: First Look Inside

We open up an amazing jet fighter analog computer made out of gears.
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Dave Jones opening of a B-52 star tracker analog computer:
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[@toinoi123]

When the cover came off - all I could think of is "what a thing of absolute beauty!" The design, the engineering. Brilliant!

[@thesteelrodent1796]

Agreed. This thing looks amazing

[@Lowrider2905]

Something I can hide under glass in my living room or office as an eyecatcher for sure.

[@ptonpc]

I thought the same thing.

[@kevincrosby1760]

From an era when things were intended to be repaired rather than just disposed of when they quit working.

[@batman-cw2hd]

they could have just used some cheap microcontrollers.

[@scsirob]

To realize that people who designed this beauty used slide rules and math rather than CAD/CAM is nothing short of amazing.

[@simontay4851]

Yeah, it really is!

[@lopiklop]

really?

[@lopiklop]

cad doesn't factor into the actual manufacturing. design is design, it doesn't help you actually build it

[@lopiklop]

you're really overestimating things. even CAD classes have you actually draw stuff

[@homo192]

@@lopiklop He was talking about disigning, not building things. And there's absolutely no doubt in tools like CAD being very helpful to certain aspects of a design process, compared to doing all that stuff manually on paper.

[@DamnLyons]

I loved the excitement in your voice when you said "Tubes!?" hahaha. I think you're in the right line of work Marc

[@alanrogs3990]

Some Bendix tubes have decent value.

[@matthewrichardson828]

I build an air data computer for NASA in 2015. It was a challenge, and I lost money on it. It came out great through. Uses MEMS devices with temp calibrated pressure sensors.

[@miladirani4313]

👍👍👍

[@Bandit-u3u]

Individually addressable? What's the feature size

[@SkyOctopus1]

Across the pond, I teach a history of computer architecture including (electro)mechanical computers. I'm delighted to see you cover this.

[@lordgman1]

Another amazing piece of engineering that I didn't even know exists, let alone how invested in it I would be. Thanks Marc!

[@gertebert]

And I thought my Curta was complicated. This is a whole new level. Looking forward to this series. As an old analog microwave engineer and HAM I really really liked the last series.

[@michaelbauers8800]

Jealous you have a Curta. A bit pricey for me, but I admit I paid quite a bit for my slide rules.

[@ocsrc]

Look at how clean and pristine this is they really knew what they were doing and how to build equipment back in the 40s

[@gigigigiontis8]

Helps it's been hermetically sealed since the 40s...

[@ryansta]

There's a beauty to it. As for those post war decades, seems such a magical time. The dawn of the Jet age to the rockets taking men to the moon along with industry and a quality of life never seen before in human history. Although technology has advanced, in many ways it can feel we've gone backwards especially were the 'working man' and taking pride in what you do, for the mass majority is concerned.

[@bobert4522]

The be fair you open anything aerospace and it will look pretty darn sophisticated

[@TheGreatGastronaut]

It ain’t that old. The SMALC overhaul tag on the top (red & white) dates from the early 80s.

[@FiliusAestatis]

This is amazing tech and very well built. I'd say we still built pretty solid equipment today even in the consumer space. If you consider what a sophisticated machine a modern phone or PC is it's actually quite impressive that they survive everyday activities for years. Modern industrial or in particular military equipment still lasts for decades and is very reparable (at a price).

[@ocsrc]

Bendix had a factory in Green Island NY. In the 40s and 50s in upstate New York there were a lot of manufacturing plants. They're almost all gone now but they lined the river and they made everything from car parts to aircraft parts to brakes. Lots of military parts. These were places where a man could work and have a living wage that bought a house and two cars and vacations and raised a family and put the kids through school all on 40 hours a week It's a time we will never see again

[@craigs5212]

Thanks, can't wait to see it working. The WW2 USS Pampinito submarine is docked at Pier45 in San Francisco. I found a link to the torpedo firing computer's maintenance manual through some links on their web page. It was a marvel of mechanical engineering very much like what you are about to tackle only much larger. Basically a mechanical analog computer. It was composed of standardized mechanical modules that could be interconnected to calculate the firing solution. There were module for all the various math functions like addition, subtraction, integration, differentiation. Always thought you pointed your bow or stern of sub at the target and fired but that was not the case. You paralleled the target course and shot. The computer calculated the data and mechanically loaded the turn point into the torpedo before firing.

[@michaelbauers8800]

I think the original bomb sights were also analog computers.

[@oldcomputerexpert]

Reminds me of the "Range Computer" my dad bought for me from the surplus store to tear apart so I would stop disassembling appliances and other things around the house. It was full of gears, small motors, gauges, and switches, and was used in some WWII bomber. I still have some of the parts 50 years later.

[@w.p.958]

Former avionics tech here, and boy do I love me some aircraft computers/instruments! When I go to an airshow or museum, I don't care about the chassis, I want to see the cockpit and instruments... lol. Also, that is one clean ADC inside! Now I see why I was solder sealed.

[@BGTech1]

I would appreciate it if you took a look at my avionics teardown videos, as you might be able to shed some light on the topic with your experience.

[@mikebarushok5361]

Same here. Occasionally worked on some pretty old equipment, but rarely anything from before the late 1960s.

[@hernancoronel]

CuriousMarc you are turning into the TechMoan of computers! Unveiling wonderful and antique computers for us to enjoy. Thank you for the video!

[@umageddon]

Hes been doing this for quite some time. Maybe as long or longer then Techmoan? He's pretty much an original, not like any other youtuber.

[@KeritechElectronics]

@@umageddon yes, he is :) and check out Usagi Electric too!

[@ninetailscosmicfox5585]

There's a channel called @Le labo de Michel who takes these things apart. They probably have tons of useful information if you need!

[@vibrolax]

Why did you have to mention that? Now I'm going to sucked into even more retro technical depravity.

[@CuriousMarc]

Absolutely! Link to Le Labo de Michel already in the Doodly-doo! Has luck would have it, he is currently reverse engineering a slightly more recent version of this.

[@BGTech1]

I can’t even begin to imagine all the math, science, and careful engineering that must have gone into this unit. For the same reason, I will buy avionics to make my own teardown videos.

[@cvkline]

I can't wait for the rest of this series! I bet I get some good material to use when teaching pilot ground school!

[@WdyWP]

This was a flashback!! I was a Nav Systems Avionics Tech in the Marine Corps back in the early '80s and '90s.

[@garyflies]

I repair avionics for a living, a lot of jet aircraft engine instruments in a cylinder case are solder sealed like that, some of them have the rear plate pressed in and also soldered, they are buggers to pull apart. I use the same method - a small blowtorch. You might be interested in finding an old flight data recorder - for example Sundstrand FEB-542, it uses pressure capsules and stylus to record analog information onto stainless steel tape cassettes

[@michaelmiller641]

What an amazingly complicated and beautiful piece of engineering, I can't begin to think what development brainpower went into designing this! Good luck Ken!

[@stephenevans8355]

When I worked in aviation instrumentation we sealed/unsealed instruments by using a succession of large soldering irons with wooden handles, steel shafts and massive copper tips heated in a kiln. Asbestos gloves were required. That gas torch was so easy and comparatively safe.

[@VEC7ORlt]

Electromechanical computers have a special place in my heart, nothing quite like them.

[@wtmayhew]

The transistors in clips appear to be in TO-5 packaging. My guess is that would date this unit to probably 1956 or after based on the transistor packaging and the black flat top resolvers. That would be near the end of F-86 production. I hoped to catch a date code on one of the components in the video, but no luck. This is a very handsome unit indeed.

[@VintageTechFan]

I got "6024"-"6102"-"3161" as datecode looking numbers. So likely a later unit?

[@ianbell8701]

If this is anything like the early Boeing 707/720 mechanical air data computer known as the KIFIS (Kollsman Integrated Flight Information System), the cam and cam-follower arrangement shown momentarily in the video is part of the mechanism that corrected for static system position error. This provided the pilot and weapons system with corrected altitude based on sensed Mach number (Pt/Ps). The position error correction for a given aircraft was physically machined into the cam whose rotational position was a function of sensed Mach number. The static pressure position error varied with Mach number and was greatest as the speed of sound was approached. Thus the “bulge” on the cam seen here. The pilot’s altimeter probably had two pressure fittings on the back of its case…one each for total and static pressure, as well as an electrical connector for the servo-correction function from the air data computer. Power for a small mechanical vibrator was provided. The early jets were so vibration free that the altimeter was vibrated to minimize friction in the display pointer on the instrument face. The old piston powered airplanes vibrated enough due to the piston powerplant. Should be interesting to see the unit taken apart.

[@Derpy1969]

It’s the carburetor of computers!

[@zeeclone]

Hey! Maybe 2023 won't be so bad after all. Looking forward to these videos Marc!

[@stephano6793]

That gasp of excitement when the cover comes off.😆 An unboxing for engineers😉

[@daniel_wilkinson]

In the late 80s I worked on Marine Corps KC-130 communication/navigation avionics. A lot of it was circa 1945 or so, complete with vacuum tubes and gear trains and crystals. Very similar to this.

[@MScotty90]

I got some GE vacuum tubes a few years ago to upgrade an audio amplifier, and when they arrived I was surprised to see the boxes marked as USAF surplus and the manufacturing date as being from the mid-80's. I had no idea they used tubes for so long. I guess I shouldn't be surprised, though, considering how old some airframes like the C-130, KC-135, and B-52 are.

[@agw5425]

Incredible design and to think they built that with slide rules and paper drawings. The blueprints and design specifications must have been enormous to fit all that electromechanical wizardry in one fairly small and lite can, and all of it analog.

[@agw5425]

@@ssnerd583 You got that right.

[@Hopeless_and_Forlorn]

When the airline I was working for received its first Boeing 737-200 aircraft in 1968, the airplane was pure analog. It had a lot of RTL and TTL logic in various boxes, effected with discrete components, but no digital anything. The air data computer was analog, and drove the captain's altimeter by synchro signals and servos. Of course, it also output analog data to autopilot and pressurization systems & etc. Around 1975 or so the continuing stream of new 737 aircraft joining the fleet delivered one with a digital ADC transmitting altitude data to a new altimeter in the captain's panel via an ARINC 429 data bus at a whopping 12,500 bits/second. We were off to the digital races. However, when the last of the airline's turboprop Convair 580 aircraft was sold off, its fuel quantity indications were still being generated by capacitance systems with vacuum tube amplifiers. They were simpler and much more fault-tolerant than the later, digital systems. Now, of course, mechanic's torque wrenches are likely to be digital.

[@MacPoop]

There will never, ever be this high a skill level of pure, highly disciplined and beautiful mechanical engineering again. Ever. 😭

[@PeterPopovicsaStrucc]

I want to learn... More like I wish to learn...

[@MacPoop]

@@PeterPopovicsaStrucc The single-chip IC was more or less the death of mechanical engineering disciplines; Now all functions are either all done digitally, or the mechanics designed in/by computers. In some ways that's a good thing, in others it's been proven inferior to human-designed human-made things

[@cncshrops]

I am quite unreasonably excited by this series, possibly because it will add depth to what I have learned on one or two aviation channels that I also haunt. I look forward to your analysis with great anticipation.

[@vexguine]

00:48 what a piece of art

[@miladmiladzade7572]

This wonder me , usa had brilliant engineers that could make a very complicated machine like this!!!!!

[@renakunisaki]

I hope you can get it working and put it into a museum with a clear housing so everyone can watch the internals do their magic.

[@tuppyglossop222]

Ken in his Google lab coat. My day Is made!

[@obsoleteprofessor2034]

Hermetically sealed to preserve freshness

[@msylvain59]

The electronic assemblies, aluminium plates with teflon insulated solder posts, are very common in old avionics, all vintage Collins gear is made like this, check some teardowns of Collins aircraft boxes on my channel.

[@paulmorley1225]

The 'elevator music segment' on this one should be very interesting.

[@warup89]

I love mechnical computers, the military sure made good use of them back in the day, mainly in ships and aircrafts.

[@MrCarlsonsLab]

Neat stuff Marc! Needs more tubes :^)

[@TheDrunkenMug]

Hello Paul, nice to see you here! Were you as excited as I was when he said "There's tubes here" ?😁

[@chemputer]

The P-80 was the USA'S first jet fighter. It just didn't see combat. The F-86 Sabre is definitely iconic though, and had a much longer service life and saw actual combat over Korea.

[@jlwilliams]

Just because Larry Bell was a great guy, I feel I should point out that the Bell P-59 Airacomet was the first US jet fighter, making its first flight in 1942. It never saw combat, partly because the Whittle W.1 jet engine that the British donated for the US to copy wasn't really up to snuff and partly because of handling problems -- but the USAAF wasn't too disappointed, as they had ordered it mostly to get experience in the operation and maintenance of jet aircraft, and did use it as a trainer.

[@chemputer]

@@jlwilliams The P-59 is a very interesting aircraft and the story behind it is also fascinating. That said, the P-80 is still the USA's first jet *fighter* on a sad technicality, as the P-59 was only adopted by the USAAF as a Jet Trainer, not a fighter. Yes, it was designed, prototyped, and tested as a fighter, but it was never actually adopted in that role for the USAAF. Sadly you gotta draw the line somewhere, which is why I said the P-80, since that was the first Jet Fighter that was adopted *as a Fighter* by the USA (Whether USAAF, later the USAF, or the Navy.) Personally I like the P-59 more, and it looks better in my opinion. The P-80 is just... bland? Not sure if that's just me.

[@enzofitzhume7320]

Can't wait to see this historical Bendix MG-1 in action!!

[@GiorgioFirpo_IU1BKT]

It's beautiful to see a group of very highly professional engineer deal with any kind of technology solving problems and so .... but also a group of very nice friends working together .....all the best ...

[@ronniepirtlejr2606]

Wow that is some amazing technology for 80+ years ago!

[@mikewifak]

Man. I barely function as a human, and somebody designed this thing. I’m gonna sign up as an organ donor on Monday.

[@PurpleVidaar]

I like the "do not blow into the tubes" label cos you know someone would have tried

[@dennisyardn1ten238]

Bendix (Allied Signal Kansas City) was also one of the manufacturers of nuclear weapons' Permissive Action Links (PAL). I was told the early versions had a lot in common with this type of aircraft instrument in terms of mechanical and electrical wizardry.

[@douro20]

You should track down a pair of Sel-Syn synchros which run on 120V line current as they make good demonstration pieces. Synchros were apparently first used for position feedback in the control houses on the Panama Canal, and they are even found in ships, the first application being the electrohydraulic steering gear on the USS North Carolina back in the 1940s, where they were used to transmit the motion of the wheel to the hydraulics which moved the rudder.

[@ydonl]

Huh. I think they used those in the 5M Hale telescope mount control systems at Palomar, for remote tracking of positions and such (big mount! Everything is far away!). Does that make sense?

[@SkyhawkSteve]

If you want to test things out, you will need to generate suitable pressures for the static and pitot inputs. When I worked on avionics on aircraft in the 70's, we used the TTU-205 air pressure test set. It let us just dial in the airspeed and altitude, and it would generate the correct pressures. It cost about $80k back then, so maybe you can pick up a used model a bit cheaper??

[@T_Mo271]

This justifies collecting a whole bag of vintage aviation test equipment as well.

[@ulrichkalber9039]

or maybe some antique plane enthusiasts have one that could be borrowed?

[@SkyhawkSteve]

@@ulrichkalber9039 pitot-static test sets must still be needed, so perhaps the nearest avionics shop has one? They might enjoy being involved in a project like this.

[@TankerKC]

I scrolled down to see if someone would mention the TTU-205. We also had a hand pump unit, but I don't remember the designation. We called it "The suck and blow."

[@SRBrown9032]

One of the advantages of analog in those days was the ability to very quickly calculate an integration equation using a cam as pictured. It was accurate enough and very fast. Digital integrations / calculus simply break the integration interval into tiny segments than do a numerical calculation on the values of the variables at the mid-point of that interval. The results are the simply summed over the span of the calculation . This approach soon outperformed analog approaches, even though the analog is a physical, visible integration of the equation. Analog computers like this one were also used for fire-control calculations in warplanes into the 60's.

[@RingingResonance]

Wow! I recognize those gear-sets! My uncle had a bunch of them we used to play with when we were kids. He must have torn down one of these or something similar. I always knew it was aircraft, but never fully knew where it all came from exactly.

[@karlmadsen3179]

Very clever. Genius. Doing computing using gears, levers, and knowledge of physics and chemistry. Truly impressive.

[@BlahBleeBlahBlah]

“Central air computer” made me think you’d pivoted into the HVAC sector 😂

[@user2C47]

And I was thinking Air Traffic Control.

[@KieranOCarroll]

Fascinating! Thanks for the memories. When I entered the aviation / avionics business back in the 1970s this type of technology was common. Looking forward to your series of related videos and many more Apollo Unified S Band related videos also - please!

[@jdm2651]

I am waiting for the typical comment that makes YT so good. Like: "I'm now 78, and my father was an engineer at Bendix at the time this was developed. Even if it was a military secret my dad sometimes brought home some brass wheels and other small parts for me to play with. Later on, when I was at high school he explained to me some of the concepts the computer was based on. I wish I still had the beautifully drawings he made." Even if that won't come up, I'm sure it happened.

[@SimonWallwork]

Inputs will be pitot & static pressure, air density, and temp. Outputs will be IAS, TAS & Mach number- and TAT.

[@benedienst]

just look at them sitting arount the thing like the little curious children they kept to be, cracking it open like dads expensive stereo before her comes down on them raging and shouting on them. XD I love Marcs channel, won't miss an episode of this!

[@mikebarushok5361]

Definitely looking forward to this one. Old avionics tech here. Including at Kollsman where we made airspeeds, altimeters and air data computers.

[@KeritechElectronics]

Damn cool! Any computer-related story to share?

[@kyleeames8229]

Electromechanical engineers: *build highly sophisticated dedicated systems for computing everything from ballistics to fluid dynamics* Electronics and software engineers: This little silicon boi just made your profession obsolete. Electromechanical engineers: Are we a joke to you?? Software engineers: Nah, your stuff is still beautiful… as works of kinetic sculpture.

[@ran2wild370]

THis is precision mechanics, I guess you can't trash that industry without consequences. maybe not that public anymore, but should be kept alive otherwise.. Houston, we have a problem.....

[@MarcelHuguenin]

Wow, that's quite a teaser! Looking forward with great anxiety to the upcoming episodes! It's amazing what engineers figured out so long ago.

[@blendpinexus1416]

the fact that we can now make a little microcontroller to do the same job this does is amazing.

[@PeterPopovicsaStrucc]

Unbelievable.... beautiful.... I wonder about the engineering process of it.... This beauty have hundreds of individually designed parts... It's a serious amount even on paper. But how that could be manufactured that time, without CNC (not even mention 3D printing, CNC sheet metal works, etc.) How could that be managed at all? I'm proud of my designs, each of them takes months to reach perfection - but for that I use powerful computers and software, and the production is done by machines..... I wish to grow up to this engineering level...

[@Evergreen64]

"Where does he get all these wonderful toys?"

[@youtubasoarus]

Incredible layers of complexity. 😳

[@KeritechElectronics]

To be honest, I also thought about vacuum tubes first and foremost! What a thing of beauty. Antikythera Mechanism indeed. 10E10 out of 10, would reverse engineer. I never saw a pneumoelectromechanical computer. Hope it keeps us entertained for a longer while than the AGC!

[@pigpenpete]

I learned the basics of this sort of thing when I was in training for a job with the MOD, I never saw anything like it ever again! Thankfully!!

[@michaelbauers8800]

Without youtube, most of us would never experience this fascinating, even beautiful engineering. Thanks so much for posting this video. I would share this with everyone I know who loves mechanical stuff, electronic stuff, and analog computers. But I am the only one I know, into this stuff.

[@brianpoi5117]

"I think you want more accuracy if you're dropping bombs and stuff."

[@NuGanjaTron]

Yeah, cracked me up. Also: "This thing must do better math." 😆

[@lordskeletorde]

Loved every second of this episode.

[@Allan_aka_RocKITEman]

When I was a student pilot -- 1979 to 1980 -- a _"glass cockpit"_ would have seemed like _science fiction._ {I soloed in November of 1979, but did not continue on to get my PPL, mainly due to lack of $$$}. All that said, I am a bit 'envious' of people today who can put an action camera in an aircraft and record an entire training flight. I would love to have archived vids of myself flying.

[@T_Mo271]

That's a gorgeous piece of work.

[@djmips]

That third grade clock story had me thinking way back to when I was around third grade age and decided to take apart my visiting aunts alarm clock and it was fully wound!!

[@johnopalko5223]

Ouch! I'll bet you learned new respect for mainsprings.

[@dodaexploda]

While you've been working on the Apollo stuff, I've wondered about the Canadian equivalent which would be the Avro Arrow. I did some research and the arrow is all analog computing. So this is probably the closest I'll get to seeing someone tinker with Avro Arrow electronics.

[@mnoxman]

See also: Navy TDC Mk 3 (Torpedo Data Computer). All analog computer.

[@gort59]

What a find! I love old mechanical computers! Thanks for the great video!

[@barakmiller2890]

I'm looking forward to this series because I have always been fascinated by mechanical computers from the Charles Babbage Difference Engine to the Battleship flight data computer and the torpedo data computer and now I have this Bendix MG-1 Air Data Computer thank you :)

[@johnedwards1685]

And after an EMP burst, this would still be running. Quite unlike the modern equivalent.

[@davidwagner6116]

1940s analog aviation computing really appeals to an old nerd like me.

[@peterdegelaen]

I'm really looking forward to seeing the next episode.

[@alexpinkerton7459]

WOW! What a thing of absolute beauty! I can hardly wait for the next episode!

[@aerohk]

Most interesting of contents. Please do more avionics reverse engineering videos. As someone who make avionics for a living, this is very entertaining.

[@chrisnizer5702]

Damn, that is friggin' AWESOME!!

[@benjaminhanke79]

I was waiting for this because I forgot where I'd seen the opening part before. I re-watched some of your videos and scrolled down on Ken's Twitter but couldn't find it again.

[@tbp-channel8870]

Es wird nicht langweilig.. (It doesn't get boring..) 🙃

[@YassineKAOUANE]

awesome, glad to be here for this adventure

[@ericflower9855]

Now this is what I love...Old military electronics ....I'd love to see you do a video on the 1st chip for the F-14 tomcat

[@marianaldenhoevel7240]

I am drooling. I want to hug it.

[@Scrizati]

When's the collaboration with Le labo de Michel haha 😄

[@TheIceGryphon]

Love flying the F-86F Sabre in DCS Worpd. Can’t wait for G.91 module too.

[@jnbfrancisco]

I have removed, replaced and operational checked many air data computers on the F111D. They were a different shape. About the size shape of a small microwave oven. I never got to see the insides but I figured it was something like this one.

[@chriholt]

Can't wait for the rest of this series!

[@remlap]

Opened up like a tin of corned beef, was half expecting "Nice Hiss" Am looking forward to the rest of this series.

[@chrisdickens4862]

I’m so excited to see this series!

[@RickMunday]

That's a thing of beauty!

[@ruston1200]

I having a hard time making a Rasberry pi do as told, so I am very impressed by your skills here, keep up the good work!

[@13bigerdave]

Springs and Gears and Tubes oh my

[@splinky99]

Is that the famous ballistics solutions computer from the F-86?…..It doesn’t seem complex enough!?……..oops…the firing comber is the APG -30!

[@KD5NJR]

Looking forward to more !

[@xfol]

The Sabre was introduced in 1949 - this must be one of the first applications of germanium transistors

[@chrismofer]

soo beautiful how they crammed all that electromechanical computing goodness into a round can.