Citation Excel (C560XL)
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Flight Crew Became Reoriented; General Flight Cancelled / Delayed; General Maintenance Action
Aircraft; Procedure
Earlier in the week the APU was replaced due to a chemical smell in the cabin. On our previous leg with the APU running on the ramp and the air on we noticed a fuel smell in the cabin. The PIC said it was from another aircraft's exhaust. I replied there wasn't another aircraft around us; and it smelled like fuel. We turned the air off and the smell went away. We departed and landed. APU running again and fuel smell again; this time we had one engine running and passengers on board. The line guy came up to our window and informed us we had fuel draining out the back of the aircraft and we should check it out. We shut down the engines and I exited the aircraft to take a look; fuel was pouring out of the aft drain and dripping/running out of the belly. A large pool of fuel formed under the tail. I asked the passengers to deplane and escorted them back into the FBO. This problem seemed to occur only when the air was turned on with the APU. We had flown the aircraft 9 legs since the APU was changed. The temperature outside had been perfect all week so we only need the APU generator and not the air. I don't know if the fuel leak was from an improper install or it occurred after. On the descent I debated starting the APU to get things done as soon as we could because we were pressed for time as usual and running late. We had another passenger trip schedule exactly 1 hour after scheduled arrival but the previous passengers were late. I did not start the APU in the air as I thought I should not rush things; what's the hurry? I'm thankful I didn't.
CE560 First Officer describes a fuel smell in the cabin that appears and dissipates when the APU air is turned on then off. During the next engine start a lineman notes fuel coming from the tail of the aircraft and informs the crew. The reporter suspects an improper APU installation to be the cause.