Date: 202106
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: 10
Light: Night
Aircraft: Bonanza 36
Operator: Air Carrier
Operating under: Part 135
Flight plan: IFR
Mission: Cargo / Freight / Delivery
Flight phase: Descent
Airspace: Class C ZZZ
Aircraft component: Reciprocating Engine Assembly
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Single Pilot; Captain
Reporter qualification: Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Flight Instructor; Flight Crew Commercial
Human factors: Time Pressure; Situational Awareness; Human-Machine Interface; Distraction
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Fuel Issue
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Inflight Shutdown; Flight Crew Landed in Emergency Condition; Flight Crew Requested ATC Assistance / Clarification; General Maintenance Action
Contributing factors: Aircraft; Human Factors; Procedure
Primary problem: Human Factors

Narrative: The flight was approximately 5 hours. Had fuel for 6.5 hours.Approximately 2/3rds of the way through the flight the engine began to get rough and vibrate. I started to troubleshoot with the checklist after verifying temperatures and fuel pressure. I used the 'engine discrepancy check rough running engine'. After doing this I determined the problem to be a spark plug on the third cylinder While on L mag.This process distracted me and I most likely did not keep up with changing tanks for the next bit of time as I was thinking about it. After about 15 minutes it went smooth again and so I re checked the magnetos and they were both back to normal. Again I was thinking about it for maybe 15 more minutes. Because of this I believe the fuel on the left tank was left on too long and the fuel gauge did not show an accurate amount.As I got closer to the airport and started descending I used the descent checklist and changed to the right tank. The left at the time was indicating about 13 gallons and the right about 19 gallons. I knew this was probably not correct because I had been flying already for 5 hours and that would mean I have 2 more hours of fuel. I reduced power when I started my descent slowly retarding throttle back to 18 in.As I descended to 4;000 feet and reached 18 in. the engine began to run rough again. I checked the instruments and saw that the cylinder 4 EGT was too low on the annunciator. And also the fuel flow was fluctuating. The engine started surging from lack of fuel. I quickly did the Engine Failure After Liftoff and noticed I was already on the tank with higher indicated fuel so tried the left tank. Without helping I tried to go back to right tank. Notified ATC that I was requesting priority handling and turning to the airport for [Runway] XXL. I knew there was a Learjet approaching for [Runway] XXR and this influenced my decision. Performed the maximum glide checklist. Shut down engine when I had the field made. Landed safely on Runway XXL with no damage to airplane requested for a tow and called my Dispatcher. The fuel gauges were indicating top of yellow arc still on left and half on right tank. After parking it settled down to 1/8th left tank half right tank. Confirming my suspicion; they were not accurate. After fueling the aircraft to bottom of tabs after Maintenance checked it out they found 3-4 gallons useable in the left tank and the remaining fuel in the right tank of approximately 20 gallons. Maintenance did not find anything wrong with the airplane.It is clear to me that I got distracted dealing with the problemMidway in the flight and missed changing the tank for an extended period of time. In the future I will write down the time I change fuel tanks and the estimated remaining fuel in each tank and compare it against the fuel gauge. I will also change tanks more frequently to prevent such a big imbalance. Every 30 minutes. I am unsure of why the airplane struggled to produce power other than the potential low fuel on the left tank. I would think switching to the tank that was fuller in the descent checklist would have solved this issue.Fuel was checked prior to the flight to confirm it was correctly filled.




Synopsis: Bonanza pilot reported distraction contributed to improper fuel balance; causing fuel starvation to the engine and an In flight Shut Down and precautionary landing.