AD 2000-01-16 covers the exhaust for most of the piston Twin Cessna fleet (excluding normally aspirated models). The AD itself is an airframe AD, pertaining to both the left and right hand exhaust systems. For each side, there are 6 paragraphs, each with their own unique initial and recurring interval values, thus providing 12 data points that need to be accurately tracked. Paragraph (b), for example, requires visual inspection of the exhaust every 30 days or 50 hours (whichever occurs later). Paragraph (g) calls for a complete replacement every 2,500 hours or 12 years, whichever is first. Paragraph (f) does not always apply to an airplane that has other paragraphs applicable because not every exhaust system has the multi-segment V-band clamps installed. Tach (pun intended) on the typical mathematical errors or omissions with aircraft total time calculations in maintenance entries, and you are setting yourself up to have confusion down the line without a proper system in place.
For this write up, we are focusing on the biggest and most expensive paragraph (g), and an interesting story that happened to one of our customers. As mentioned above, paragraph (g) calls for replacement or overhaul, and as of today (May, 2023), typical costs are about $13,000 plus labor. With his tail fresh out of annual, a customer of ours, who we will refer to as "Bob," signed up for our service and shipped his logbooks using our Pelican case system. We scanned and organized every document in house, hand typed the maintenance records, and set up his maintenance tracking profile. Through our detailed approach which allows for unprecedented search capabilities, we were able to determine that Bob's tail was overdue on paragraph (g). Bob went back to his shop, logs in hand, and asked them to verify our findings, which turned out to be accurate. Not only were they correct, the shop then noticed that there were holes in the exhaust! Two important details that were completely missed during the annual inspection.
Bob had his exhaust replaced immediately, and later told us in person that our service was priceless at that point, possibly saving his life.
Photo credit to www.aviationconsumer.com.