Date: 201702
Local time of day: 1201-1800
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Light: Daylight
Aircraft: Citation Excel (C560XL)
Operator: Air Taxi
Operating under: Part 135
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class B ZZZ
ATC / advisory: TRACON ZZZ
Aircraft component: Electrical Wiring & Connectors
Component problem: Failed; Malfunctioning
Reporter organization: Air Taxi
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Workload; Troubleshooting; Time Pressure; Situational Awareness; Distraction
Second reporter function: First Officer; Pilot Not Flying
Anomaly: Aircraft Equipment Problem Less Severe; Conflict Airborne Conflict; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Landed in Emergency Condition; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Diverted; Flight Crew Took Evasive Action; General Maintenance Action
Contributing factors: Chart Or Publication; Aircraft; Human Factors; Procedure
Primary problem: Aircraft

Narrative: While acting as Pilot in Command on a flight we smelled an electrical burning smell followed by smoke in the cockpit. We were on the RNAV arrival around 12000 ft. We executed an emergency descent to ZZZ airport to land. I was the flying pilot in the left seat while First Officer handled the radios and checklist items. During the emergency descent we encountered a TCAS RA and complied with it by climbing and turning to our right towards the north to avoid the VFR aircraft which was not talking to approach. Approach did advise us of the aircraft since it was on radar. After complying with the RA we continued with the emergency descent and checklist items prior to landing. We commenced and complied with the Electrical Fire or Smoke checklist from the CE-560XLS checklist. Once the checklist directed us to place the cabin master and generators to the off position the smoke subsided but the electrical burning smell was still present. I decided to deploy the passenger oxygen masks manually due to the continuing burning electrical smell. We briefed the passengers of the situation and advised them of our plans to immediately land. We landed and cleared runway and performed an evacuation of the aircraft on the taxiway due to the existing electrical burning smell. The landing was normal and uneventful. We immediately disconnected the ship's battery after exiting the aircraft. Fire and airport ops met us at the aircraft. Fire performed a search on the aircraft and advised us that there was no present danger. We had  the aircraft [towed] to the ramp. The crew and passengers suffered no injuries or problems from the event.Overall I feel as though the First Officer and I acted appropriately and worked well together as a crew under the circumstances we were dealing with. There are a lot of things going through your mind when you smell burning and see smoke in an airplane. Our goal was to get the plane on the ground as soon as possible. I would advise all crew members to pay close attention to the TCAS before initiating an emergency descent to avoid any conflicts with other aircraft like we had. I was focused on getting the airplane on the ground and [the First Officer] was focused on the checklist and radios. The TCAS system definitely helped to prevent a conflict with the VFR aircraft. Following the appropriate checklist lead to the turning off of several important switches which eventually put an end to the smoke. We both have learned positive things from this event and come out of this as better pilots in my mind.


Second narrative: The XLS electrical fire/smoke checklist is complicated. To be honest it is not a well-organized checklist; nor is it laid out in a way that guarantees that a crew can perform the checklist error free in a stressful emergency situation. Ideally the right seat pilot needs to be Pilot Flying (PF); so that the left seat pilot can read and execute the checklist items since most of the items are on the front left cockpit panel. I believe in this case it was good idea for PIC to remain PF in left seat; and perform the checklist items as I called them out with my confirmation for critical items. By remaining PM; it allowed me to be methodical with the checklist from the right seat and scrutinize each item in order to ensure that we did not turn off essential systems that we would want available if possible. (i.e. brakes; speed brakes; TR's). In this situation with time compression; had we run the electrical fire/smoke checklist to its completion including BATT EMER; we would have had a significantly degraded our chance of a successful landing; inability to clear the runway to evacuate; and potentially blown tires/overrun etc.The TCAS RA portion of this event was not a good situation. Each time that I think about whether we could have delayed our descent to coordinate with ATC on traffic; I decide that no we could not. We had no idea that the airplane was not going to be overcome with smoke; or worse. I believe that an immediate descent and landing was indeed necessary; and we did so under emergency authority and without ATC direction away from traffic. I credit the PIC for his quick reaction to the RA in arresting our rapid descent and turning away from the traffic.It may be worth noting that I had just returned from recurrent training on the tour immediately preceding this event. I had reviewed the electrical fire/smoke checklist during my personal study in recurrent. This may have helped in the decision to recognize that we needed to stop the checklist prior to 'emergency braking'; and avoid a more dangerous situation with an un-needed use of emergency braking.I do not believe that I would have done anything differently if I had do perform this same event again. If anything; I would have tried to divide my attention as Pilot monitoring (PM) between the emergency checklist; and assisting the PF in avoiding traffic using TCAS before it became a critical issue during our emergency descent. I was contacted by company managers and a union representative after the fact and I was able to discuss the event to my satisfaction at the time. I was assigned flight duty the next day on a different aircraft. I showed a few minutes early in order to visit the mechanics on our aircraft to see if they had found the source. I was advised at that time by mechanics that they believed the source was a unprotected set of wires under the forward left galley carpeting. The wires had burned the plastic non-stick material under the carpet. I do not know what the final resolution was; as the aircraft was still in maintenance at the time of my filing this report.


Synopsis: A CE-560XLS flight crew reported smoke and fumes on descent so the crew diverted to a nearby airport. Maintenance found a burned set of wires under the forward left galley carpeting and believe that to be the smoke's source. The First Officer commented about the aircraft emergency checklist complexity.