Super King Air 300
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Physiological - Other; Time Pressure
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Fuel Issue
Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Returned To Departure Airport; Flight Crew Overcame Equipment Problem
Aircraft; Human Factors
Right aux bladder had been replaced the previous week. Noticed a fuel imbalance during preflight and maintenance said they only had 35 gals in the right aux since they replaced the bladder. We added fuel and left. First landing was uneventful but due to weather; we had just used the fuel in the aux tanks and were just a little bit into the mains tanks. The airplane was fueled and sat for about 1.5 hours while the crew coordinated the next inspection. When crew went to leave; another aircraft was parking on the ramp in front of our airplane while we had the main cabin door open. Crew noticed fuel/exhaust smell in aircraft but attributed it to the exhaust of the other aircraft. Crew started engines and taxied out for takeoff. Several comments were made by the crew members on how bad the smell was inside the aircraft. After takeoff; fuel fumes became more present in the cockpit and cabin. Burning eyes; irritation in throat was experienced by all crew members. Crew elected to go on supplemental Oxygen and return to departure airport for precautionary landing. Crew was getting vectors and believed the smell was getting worse. In order to not have any delays; PIC [requested priority handling] for immediate landing. No further assistance required. Landed without incident. PIC called off [support] trucks when switching to tower.Crew believes there was improper installation of the right fuel bladder causing a fuel leak in the belly of the aircraft.
Air carrier First Officer reported a fume event during initial climb.