Date: 201603
Local time of day: 0601-1200
Location: MDW.Airport, IL
Flight conditions: VMC
Light: Daylight
Aircraft: Light Transport
Operator: Fractional
Operating under: Part 91
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise; Descent
Airspace: Class E C90
ATC / advisory: TRACON C90
Reporter organization: Fractional
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Distraction; Communication Breakdown; Confusion
Second reporter function: First Officer; Pilot Not Flying
Anomaly: ATC Issue All Types; Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Chart Or Publication; Equipment / Tooling; Human Factors; Procedure
Primary problem: Human Factors

Narrative: Shortly after departing we were cleared direct to the KAMBL intersection and to continue on the ENDEE4 arrival. Pilot Monitoring (PM) was getting ATIS and communicating with FBO at MDW making arrangements for our arrival. PM had just returned to my frequency as we approached KAMBL intersection and he was inputting approach and landing data. I noticed as we hit the KAMBL intersection that the aircraft did not turn towards the next fix. So; I zoomed in the scale on the MFD display and immediately checked my flight director mode to make sure I was in LNAV; and confirmed we were in the correct mode.This delayed my reaction a few moments. I spoke up and asked the PM to verify what I was seeing. We both agreed to go to heading mode and turn the aircraft back on the arrival. About this time ATC asked us if we were on the ENDEE arrival. I looked at the MFD as we communicated with the controller. We were turning back on course; but were 4 miles off course. The controller decided to clear us to another intersection along our planned route.The controller cleared us to what we heard as the HILLS intersection. This was read back to the controller and input into the FMS. This fix is the initial approach fix on the GPS/RNAV31C at MDW. The controller handed us off to the next approach controller. This controller asked us if we were still on the arrival. We responded that the previous controller had cleared us to the HILLS intersection on the approach. This controller said; 'No.' We were supposed to be flying to the 'JILLZ' intersection; which is on the arrival. He; then cleared us to ENDEE intersection and we continued with no further issue. Course deviation was detected by crew as aircraft did not smart turn towards next intersection. Then; by ATC. The next controller advised us of the next fix we were flying to being the wrong fix. Not sure why initial course deviation occurred. The MFD displayed a dashed line after KAMBL extending our inbound heading to the fix; and the FD was flying in this dashed line. The arrival was also displayed. So; going to heading mode and flying until we could correct the FMS problem was our best course for a timely correction. The second problem was most likely hear back/read back error with similar sounding intersections along our cleared route. We complied with ATC instruction as best we could. FMS vigilance would have helped. My MFD was zoomed out to a range where I did not notice the dashed lined past KAMBL intersection until the aircraft's lack of turning clued me in. By this time I was in reactionary mode versus being proactive. In communication; extra vigilance should be paid to look for similar sounding fix names anywhere in the cleared flight plan. Then; if any confusion arises to get clarification immediately.


Second narrative: We were cleared direct KAMBL to join ENDEE4 arrival shortly after departing. After crossing KAMBL the aircraft maintained the inbound heading instead of joining the arrival course. The angle off course was large enough that by the time we were able to identify the course deviation ATC asked us about our course. The controller cleared us direct HILLS and gave us a frequency change. The next controller asked us where we were cleared to and told us we should have been cleared to JILLZ. The new controller cleared us to ENDEE on the ENDEE4 arrival. The course deviation was detected by flying pilot and ATC shortly after. I am [questioning] what happen to the FMS because we went to heading mode and reprogrammed new instructions. The FMS was in LNAV1 and had a dashed line on the course being flown along with the ENDEE4. The confusion on the HILLS clearance was most likely a read back/hear back error. After the course error was detected; we went to heading mode to rejoin course. Be especially vigilant when intercept angles are large and there is little time to correct a missed intercept. Recheck the FMS after going directly to a fix to ensure the remaining flight plan is correct. When cleared to a fix look carefully for similar sounding fixes along the route and don't assume the controller's intentions if there is one.


Synopsis: Fractional Jet flight crew reported of a possible equipment problem with the FMS that might have taken them off course. Flight crew also reported of similar sounding intersections that also caused navigation problems.