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Allied Supportability Program

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Ed Thelen's comments - There are many MTBF (Mean Time Between Failure) numbers in this document. The lower numbers are supposed to reflect how many hours the various vacuum tube circuits were likely to last before experiencing a failure. I had almost 2 years on-site experience with the almost identical Nike Ajax IFC equipment. The only major difference in the IFC was the added Target Ranging Radar for the Hercules. The numbers quoted in this document would indicate that there would be about one disabling failure every 6 hours. That is just plane silly. Not just wrong, not wildly wrong, all the way to silly. Seems to me that somebody was trying to make a case for converting to more reliable solid-state equipment (a good thing of course) by doctoring the numbers for the existing equipment. As a point of reference, there are 24 x 7 hours in a week, 168 hours. Page 6 indicates that the analog vacuum tube Moving Target Indicator unit had a MTBF of 150 hours, less than a week of hot alert - The unit we had failed once in about 90 weeks I was on that site. (We found the bad tube and fixed it in less than a half hour.) Page 11 indicates a MTBF for the Target Tracking Radar Receiver of 275 hours (less than 2 weeks) - sheer balony - I well remember our first TTR failure/weakness when we couldn't get the specified minumum gain in the sum channel - about 4 months after the site became operational. In theory, because variations between tubes might de-tune the IF strip slightly, we should send the whole strip back to Ordnance. Big discussion, screw it, lets change the weak tube and see what happens - the strip looked good to us. Lets ignore Ordnance for this - AH - a favorite story about the analog computer. (Page 14 quotes an MTBF of 55 hours, about 2 days). There were three of us repair guys. Sizlak wanted the BC van so he could hang with the officers - He believed in "If it ain't broke, don't fix it." The computer always passed its internal tests, and Sizlak ignored it. About 8 months after we activated the site, went Sizlak was on leave. Lopresti and I took over the BC van as well as our normal RC van. One day the computer wouldn't settle during the daily tests we gave it. (A red zero set warning lamp kept blinking). Where to start? Lopresti and I had kind of forgotten how to trouble shoot the computer. We started testing tubes in the computer, AH this one must be it - it hardly wiggles the test meter. Computer still has warning light. We find another VERY weak tube, and another, soon we have more weak tubes than our spares, maybe 12 or 15, I don't remember. Another big huddle - with officers this time - and declare the site down due to weak tubes - and send off a big "Blue Streak" order for the high gain triodes that were sick. Ah - site down - white alert - wait for parts, kick back and relax :-)) Unfortunately, about 8 hours later an army sedan from Ft. Sheridan shows up with our order - vacation over ;-)) That computer did *not* fail every 2 or 3 days as predicted in the document !!! Maybe like 4 to 6 months !!! - We did start testing tubes in the computer on a regular basis after the above episode - Then they mention daily adjustments on things like the display scopes - more sillyness - about as silly as the maintenance manual for your car saying you should check the radiator fluid level, break fluid level and tire pressure daily. The auto manufacturer doesn't want to get sued, so gives this silly advice that is totally ignored by everyone I know.

Created Nov 18, 2000