Date: 202008
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Night
Aircraft: Light Transport; Low Wing; 2 Turboprop Eng
Operator: Air Taxi
Operating under: Part 135
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
Aircraft component: Minimum Equipment List (MEL)
Component problem: Improperly Operated
Reporter organization: Air Taxi
Reporter function: Captain; Pilot Flying; Single Pilot
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor; Flight Crew Instrument; Flight Crew Multiengine
Human factors: Communication Breakdown
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural MEL / CDL
Detector: Person Flight Crew
When detected: Other Post Flight
Result: General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft; Procedure; MEL
Primary problem: Procedure

Narrative: I was dispatched from my company to serve as Part 135 PIC (Pilot in Command) on board Aircraft X. The aircraft was operating under an existing MEL over a popped Right Transfer Pump Circuit Breaker. The Circuit Breaker was thereby collared. That MEL has a restriction that states that both fuel gauges be operational. However; given there was a flight restriction associated with this MEL; the mechanic who recorded the MEL in to the Record Of Deferred Maintenance (RODM) portion of the aircrafts Daily Maintenance Record (DMR) failed to notate 'Flight Restriction- See Item Remarks' within the Discrepancy portion of the RODM. During my preflight of Aircraft X I checked the RODM and was aware of the MEL; however because I did not see the specific notation 'Flight Restriction- See MEL Item Remarks' I did not take further action to investigate. I departed in Aircraft X from ZZZ to ZZZ1 where upon climbout I noticed the right fuel indicator operating erratically; varying from normal to below zero and back again. After landing and disembarking crew and patient I called the company on-call mechanic to report the discrepancy. During our conversation I reported there was an existing MEL for the transfer pump. It was decided to MEL the right fuel quantity indicator and then the on call mechanic asked me to call the company Maintenance Control operator to receive a MEL Control Number to use for the writeup. I then called Maintenance Control and discussed the discrepancy and was given the MEL Control Number. I was instructed to make the appropriate write-ups in the DMR (Deferred Maintenance Report) and RODM (Report Of Deferred Maintenance) and then send the Maintenance Control technician photograph copies of both. I did so and received confirmation of his receipt. Within the 'Remarks or Comments' section of the Fuel Quantity Indicators portion of the MEL it specifically states (among other things) that 'Both NO FUEL XFT Annunciators are operative.' I verified the operation of the NO FUEL XFT annunciators by pressing the Annunciator Test Button that illuminates all of the aircraft dashboard annunciators. Indeed both NO FUEL XFR Annunciators did Illuminate/Operate. I would later come to learn during a debrief with my Assistant Chief Pilot that the Right NO FUEL XFR Annunciator should not have been considered Operative since the Right Fuel Transfer Pump Circuit Breaker had been 'collared' by the previous MEL.I then departed Part 91 with my crew back to base ZZZ1 to ZZZ. After my required rest period I dutied back on with a call to Dispatch and then learned that the aircraft was out of service due to improper application of MEL.This Occurrence was 'Self Reported' to the FAA on DATE by our Director of Maintenance after the oncoming pilot performed the aircraft's preflight and discovered the conflict. Fortunately this was the same pilot involved with the initial discovery of the Right Fuel Transfer Pump discrepancy which led to the MEL. As such; he was recently made familiar with that MEL's requirement of operative fuel quantity indicators. A special ferry flight permit was later authorized and the aircraft was repositioned to ZZZ for necessary repairs.Upon reflection and after speaking with my Director of Operations; I realize that instead of relying on the writeup in the RODM; if I had taken the extra time to investigate the previous MEL; I would have been made aware of the MEL's Limitation requiring both fuel quantity indicators to be operative. I would have then known that the aircraft would require maintenance in ZZZ; be unable to apply for the Fuel Quantity Indicator MEL; nor allowed to fly further. Although the 2nd MEL would not apply; I also understand that the Right NO FUEL XFR Annunciator should not have been deemed Operative given the collared Circuit Breaker. However; it seems the MEL wording could make this distinction more clear.The company's General Maintenance Manual makes clear that Right Transfer Pump MEL requires the specific notation 'Flight Restriction- See Item Remarks.' I Believe the failure to make that notation was a link in the chain that led to this unfortunate event. The two maintenance technicians I spoke with on the phone that early morning were aware; or made aware of the existing (and conflicting) MEL. Specifically; as I understand it; it is the job of the Maintenance Control Technician to ensure compliance. Again; missed opportunities. Lastly; I believe the late/early hours of the morning in which this event occurred may have played a factor given the studies involving disrupted circadian rhythms which are an inherent part of our Medivac operation. I deeply regret this occurrence and will increase my diligence to help reduce the chance of something like this happening again.




Synopsis: Pilot reported misidentifying conditions requiring additional log book entries and MEL actions and operating the aircraft.