Some owners intently fly their old birds for years without upgrading anything, but others are repeat offenders—in and out of the shops on a regular basis for the latest gear. Somewhere in the middle is taking what you’ve got and modifying it to better suit your mission. Eventually, a retrofit or mod could require an FAA approval process that’s above and beyond the scope of the equipment.
Here’s a general rundown of the complex certification process that tags along with major modifications not previously approved for the airframe or engine.