Saturday, January 31, 2015

Cannon Plugs

Machinist's Mate 1st Class Chad Craycraft, removes the tampion from a 24-pound long gun aboard U.S.S. Constitution.
U.S. Navy photo by Mass Communication Specialist 2nd Class Clay Weis
Admiral Sir David Beatty, RN, greeting Rear Admiral Hugh Rodman, USN, under the guns of HMS Queen Elizabeth,
upon the arrival of Battleship Division Nine, U.S. Atlantic Fleet. 1917.
Note the rather ornate tampions sealing the muzzles of the 15-inch guns.

(Public Domain Photo)

Uh Sarge, what's a tampion? I know what some of you are thinking, don't go there. While I enjoy sophomoric humor as much as the next guy...

Oh yeah, a tampion. What is it? I know, let's ask Mr Wiki!
A tampion is a wooden plug, or a metal, canvas, rubber, or plastic cover, for the muzzle of a gun. Tampions can be found on both land-based artillery and naval guns. Naval tampions have developed into works of art.

Although the cannons of ships of the line were protected as they were retracted inside the ships, many smaller vessels had exposed gundecks which required a plug to protect inside of the barrels. Later, the invention of mobile gun turrets meant that all guns were constantly exposed to water. Hence, when not in use, naval guns were protected by wooden, and, later, rubber, muzzle plugs. Typically, rubber and plastic tampions can be shot through in case of an emergency. Plastic tampions are normally designed to be expelled by the build-up of pressure in the barrel as the first shell is fired.

Over time, tampions were embossed or engraved with the arms of the unit, and they became collector's items. Nowadays, even warships that typically would not carry heavy guns, such as submarines, have their own badges in the shape of a tampion. (W)
While a tampion is indeed used to plug the barrel of a cannon, so could be referred to as a "cannon plug," those are not the subject of this post.
Yeah, this one. (Source)

Now, the "Cannon plug" is named for James H. Cannon, founder of Cannon Electric in Los Angeles, California (now part of ITT Corporation). So I guess I should be capitalizing "cannon" every time I refer to this sort of electrical connector.

But ITT Corporation is not the only outfit who makes this sort of connector. Bendix and Amphenol are two others and they both make what I would call a "cannon plug."

Cannon plugs were addressed in a recent post about the front radar scope on the F-4. That tale illustrated one potential difficulty of disconnecting a cannon plug in order to remove an LRU from a jet.

Cannon plugs will, from time to time, go "bad," as in "not work anymore," as in "what is wrong with this freaking piece of crap I'm getting no signal to the cockpit." Various and sundry other descriptions may apply.

When cannon plugs go bad they make really bad NETFLIX series about them in which the cannon plugs form a gang and produce meth-amphetamine out in the desert. All the while trying to maintain a low profile...

No, they don't. I'm just playing with you.

When cannon plugs go bad, they typically need to be replaced.

Why replace them Sarge? Can't you fix them?

Uh, not to my knowledge. One way in which these things go "bad" is that a pin connected to a wire won't seat properly. So when you plug in the connector, that pin slides back and does not make electrical contact, thereby preventing whatever signal is on that wire from getting through. These plugs used to be sealed units, once a pin was bad, it was bad. Couldn't fix it.

In these days of magic jets where the onboard computer tells you what's wrong and it's all unicorn farts and champagne dreams...

Sorry, showing my age there. (In my day we maintained aircraft with nothing but a hammer, a screw-stick and a pair of vice grips. We had to think in those days. We... Blah, blah blah, walked to school barefoot, uphill in the snow, both ways and other old guy ramblings. Actually I would love to have had the jet tell me what's wrong with it rather than trying to puzzle it out.)

Perhaps the newer connectors are repairable in the field. I don't know. My maintenance experiences all occurred back near the dawn of time. Shortly after the Earth cooled and the first single-cell organisms appeared. (No, those organisms were not called "politicians." Most single-cell organisms of my acquaintance have an actual purpose. But I digress.)

So there I was...*

Kadena Air Base, Okinawa, night shift 1976. I was a young airman, still wet behind the ears having only reported for my first assignment back in February. Fresh out of tech school after a month's leave I was the furthest away from home I had ever been.

While this was not my first time out of the country (I spent a long weekend in Montreal a few years before, hey Canada is kind of foreign, right?) this was the first time I had been away from North America.

When I got to Okinawa, we were on 12-hour shifts. Two of them, 7 to 7. Day shift and night shift, five days a week. Most of the experienced guys there had arrived from Thailand when we had pulled out of Southeast Asia. They said, "Hey, we did twelves in Thailand. With no days off, you guys have it easy."

Okay. What do I know?

So I get to work and find out that my trainer, SSgt Abbott, and I have to go out to one of the "nose docks**" and relieve Sergeant "Tokyo" Rose and his 3-level.*** They're replacing a cannon plug in the rear cockpit and are about half-way done.

This particular cannon plug was part of a major wiring harness running between the radar system in the nose and both cockpits. I do recall that this one plug had something like 120-pins, all of which had to be pulled out of the "bad" cannon plug, the flaky pins cut off and new pins attached to the correct wire, then inserted into the new cannon plug.

We were told that Tokyo and his 3-level had about half of the plug done. They had been at it all afternoon. They were also the guys who had troubleshot the problem down to the plug they were in the midst of replacing.

We got to the jet and SSgt Abbott went to get the debrief from Tokyo, he sent me up to the cockpit to see how the 3-level was making out. I climb up the ladder and lo and behold, it's A1C Schmuckatelli, aircraft marshaler extraordinaire and destroyer of dump masts. (Hhmm, we perhaps could have tagged him with the nickname Shiva.) We've met him before.

He is sitting on a stool in the rear cockpit (from which the ejection seat has been removed) and is merrily clipping off wires, checking the pins as he does so to make sure they are secure and he is surrounded by bits and pieces of wire and wire insulation. All over the floor of the cockpit.

Now like I said, I'm an inexperienced 3-level myself, but two things strike me right away. (I did kind of pay attention to some things in tech school and one of my civilian jobs was doing work as a wireman. Wiring the electrical panels of machines. I knew a couple of things about connectors and such.)
  1. All that crap on the cockpit floor would have to be cleaned up. Pilots get really annoyed when they roll their aircraft and crap flies up into their faces.
  2. Very few of the extracted pins seem to be labelled.
Oh shit, oh dear...

For you see gentle reader, each pin has a place where it needs to be in order for the equipment to function properly. Each pin in a cannon plug has a number (typically) and Schmuckatelli had not bothered to label all of the wires. Usually you had some masking tape which you would wrap around the wire, check the number of the pin, write that on the tape, then pull the pin.

Schmuckatelli had been less than diligent in his pin labeling. Some were labeled ("Yeah, I just labeled the good pins. Well, most of them.") many were not.

Which meant that SSgt Abbott and I would probably be spending the entire shift fixing Shmuckatelli's error.

Well, Tokyo and Schmuckatelli departed to head back to the shop and go home. I told Abbott what was what and waited for the great man's decision (SSgt Abbott was a great trainer, knew his stuff and was very patient. With me as a 3-level he required a great deal of patience. There are days when I can be as smart as a bag of hammers. And those are my good days mind you!)

Well, Abbott was a bit annoyed, while Schmuckatelli had made some extra work for us, he had also (most inadvertently I assure you) provided us with a great training exercise.

What we had to do was simple really. A pain in the butt, but simple. First we needed one of these:

The ubiquitous PSM-6, what we usually called an ohmmeter.
(Rick Gammon photo from the WCS Facebook group.)
We pulled out the tech order, with all of its assorted wiring diagrams, and then we would use the ohmmeter to check the continuity from the radar package to that plug in the rear cockpit. Note that there was more than one plug in the radar package which connected to our plug. It was going to be a busy and somewhat tedious night.

Eventually we got it all sorted out. The plug was replaced, the system was powered up and checked out and we discerned that the malfunction which required the replacement of that plug had been cleared. Everything seem to work in accordance with (IAW) applicable directives and technical specifications. As we were fond of saying.

I learned a lot from SSgt Abbott. One thing which was to never follow Schmuckatelli on a job. Like I mentioned in that post linked above, I don't know whatever happened to Schmuckatelli. He meant well, just seemed that bad luck and trouble followed him around.

Or maybe...

Do you think he did these things so that he wouldn't have to do them ever again? You know, the old "if I screw this up bad enough they won't make me do it next time" thing.


No way.

Then again, you have to wonder.

Thinking back on it, after his flightline antics Schmuckatelli was assigned to work in the shop. The shop with air conditioning, vending machines and chairs, tables and all the amenities. Instead of having to drag a heavy toolbox around on the flightline in the searing heat and (sometimes) pouring rain. Climbing up aircraft, getting Phantom bites and going deaf from the roar of the Dash-60 ground power units.

Maybe the kid wasn't so dumb after all...

** A nose dock at Kadena was a concrete shelter which covered the front half of the aircraft. At least we would be out of the weather should it start to rain. Any sort of maintenance which would take time and possibly expose the interior of the aircraft to water was done indoors. Or semi-indoors in this case.
*** At the time Air Force specialties had four levels of experience. 3, 5, 7 and 9. No, I don't know why they were numbered that way.


  1. Just for S&G: "Tampion" is pronounced "Tompkin". No I don't know why. Yes, I now know what spell correct tries to turn either word into ;-).

    1. I did not known that. Google doesn't know that. Of course, Google has never (to my certain knowledge) ever been in the Navy.

      So I'll go with your pronunciation Cap'n. (Which also doesn't sound like that other thing which spell checker likes.)

    2. Or function that way either--well, except in the most basic sense.

  2. Re: the old "if I screw this up bad enough they won't make me do it next time" I recall, that worked great for me when a girlfriend moved in with me then insisted that I do the laundry. One red thing in with her whites and I was never, ever allowed to touch anything laundry-related again.

    1. And that, my Friend, is the difference between a girlfriend and a wife. I tried that once. Mrs Juvat promptly deposited the pink garments on my side of the bed and went to the mall and bought all new lingerie and clothes. Not that that was a bad thing mind you!

    2. Murph, that always works with girlfriends. Do it enough and they find a reason to replace you with a more willing minion. DAMHIK

    3. And yes, Juvat is correct. A wife won't let you get away with that stunt more than once.

      By the way, well played Mrs. Juvat, well played!

  3. Thanks, FOD in the cockpit. HMMMM. I'm thinking Monday.......

    1. Excellent!

      We seem to have established some sort of synergy lately. What a team the three of us make!

  4. We had a Shmuckatelli. He was a Lt. Ghastly ongoing train wreck.

    1. Lt. Ghastly? Didn't he have a brother in the Air Force. I swear I know that guy.


    2. Should have said, ongoing ghastly train wreck. Doubt if he had a brother serving as we would have lost the Cold War.

  5. FYI: A comment on the Cannon plug . . . in 1972 I was sent (by my unit, a depot-level repair facility) to a civilian company for training in soldering and repair of multi-level printed circuit boards. (The name of this firm was Pace Inc., located in Silver Springs, MD.) One thing emphasized in training was proper techniques used when assembling Cannon plugs. We had to make damned sure that we'd filled each pin with solder, top to bottom. This was NASA Spec standards. Seems that there'd been a satellite launched that just stopped working. This was costly . . . several million dollars, I was told. After extensive trouble-shooting, it was determined that the culprit was one, or more, of the Cannon plugs that were used. Turned out that each pin on one of the plugs contained a minute air pocket formed during the soldering process. These plugs checked out fine when tested, pre-launch, here on Earth but once in the vacuum of space the air pocket expanded and blew the wire out of the pin. So . . . a new standard of soldering was developed.

    1. Excellent story Snuffy. Thanks for sharing that.

    2. Did the USAF ever use the ME-352 A/U VOM? Your picture of the PSM-6 got me remembering. We had a shite-load of the 352s at Field Station Berlin. Most were unusable or cracked or unreliable due to misuse and apathy through the years. Our TMDE (PMEL) guys did their best. Replacing the meters was a no-no, as it would impact our yearly budget. THEN . . . the mechs found out that if one ordered just the faceplate for the meter, it came with all the guts attached but wasn't counted as an equipment asset. Rather, it was now a repair part. Needless to say, in the van of an upcoming IG visit, all the meters received new faceplates. Repair parts were not "Hand Receipt" items, so tended to get lost in the crowd.

    3. It doesn't ring any bells. Your guys were pretty clever.

  6. Cannon plugs are almost as big a PITA as vacuum tubes... sigh

    1. And I used to deal with both.

      A long, long time ago...

  7. Tompkins aside, that's a great picture of Beatty and Rodman. I can almost hear Beatty saying, "There was something wrong with our bloody ships that day, you know." Rodman's uniform is interesting too, the "service dress pyjama" of the era. Worst uniform in navy history. Except for aquacam, of course.

    Your Schmuckatelli reminds me of an E-2 HM striker I knew. Did the most remarkable things. Once wrote in a medical chart, "the payshun has amimomma." I think they finally had to send him to OCS.

    1. Okay, two days in a row...

      Coffee meet monitor, monitor meet coffee.

      ...they finally had to send him to OCS...

      I think I have amimomma. Whatever that is.


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