Over the last several years I have seen many logbook entries from mechanics, some good, some bad and some just downright ugly. In the last several weeks I have been involved with a buyer looking for a used Flight Design CT ($70K - $90K). This has given me a unique opportunity to really look at logbook entries and documentation (or the lack of it) and see just how that might affect the ultimate selling price of the aircraft itself. Surprisingly, many poor entries have also come from A&P’s and not only RLSM-A’s from the logbook entries I have seen. These poor logbook entries and lack of documentation will cost the owner dearly when it comes time to sell. From what I have seen lately, it’s not hard to lose $5K-$10K in value due to lack of documentation. These are legal records and need to be treated as such. This is one of the only legal ways you can show either someone did something to your plane or did not. As important, log books showing compliance to not only the aircraft manufactures Service Bulletins for the airframe but also for its Rotax engine greatly increases the Aircrafts total value!