Q400
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Communication Breakdown; Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural MEL / CDL
Flight Crew Became Reoriented; General Maintenance Action
Procedure; MEL; Aircraft; Logbook Entry
Upon arrival in ZZZ found lavatory seat detached and FA (Flight Attendant)-A advised that Air Stair door lights were not working. Contacted Maintenance Control for those items.While making log book entries I found that the Air Stair door lights were working and advised FA-A on how to operate the push down button to activate the lights. I then made the Lavatory seat AML (Aircraft Maintenance Logbook) entry. Maintenance showed up some time later and took the broken seat and AML.While waiting for Maintenance to return I called my Dispatcher and she advised Maintenance was going to MEL the LAV and inquired about the Air Stair door lights. I advised her there was no AML entry for the lights as they were working properly. She then consulted Maintenance Control on her end and provided the Lavatory Inoperative MEL Dispatch release amendment over the phone to my dispatch release. We then boarded and I reviewed the MEL provisions with FA-A and the First Officer. As boarding was winding up; Maintenance showed up and performed the Maintenance actions required to MEL the lavatory. I reviewed the last page of the AML to verify my write up was complied with. And off we went.After takeoff we received a message to contact Dispatch. After contacting; I learned that Maintenance had put the air stair door lights on MEL during this process.After reviewing the AML more closely I discovered that Maintenance had made a Maintenance write up and MEL of the air stair door lights on a page prior to my lavatory entry. They were able to do this due to daily checks from the previous days still having white pages to write on. I did not expect this. My assumption is not use white pages with daily checks from previous calendar days for AML entries and to make AML entries sequentially.As a side note; I find it odd that Maintenance did not even ask me to make the additional AML entry for the Air Stair door lights and they did not verify the operation of the lights prior to the MEL.Lesson learned; do not try to get ahead of the game by amending the dispatch release with MEL's until the log book is back in your hands. Let the process work. This will make a great example of swiss cheese and expectation bias when conducting Captain OE.
DH8-400 Captain reported confusion regarding logbook maintenance entries and MEL procedures caused aircraft to be flown with an open item in the logbook.