Narrative:

While on initial approach to fll; after obtaining ATIS and having a normal descent and RNAV arrival; I was told by ATC to expect ILS 10R. I followed my standard single pilot procedure and sets both pilot and copilot sides up for the ILS 10R approach; tuned to proper frequency (111.75) for the ILS on #1 and #2 navs; identified both #1 and #2 navs for proper morse code identifications; and tuned the #2 pfd to short-range nav (green needle) and tuned final approach course to 096 degrees for the ILS; set both #1 and #2 pfds for DH of 250 feet for the approach.I did not set the #1 (pilot side) pfd course needle at this time because I was still navigating on the RNAV arrival and my standard procedure is to stay in the mode that I'm navigating with (in this case RNAV with purple needle) and keep the autopilot and flight director coupled to the primary (#1 pfd) which allows me to focus attention on setting up the rest of the cockpit and running the appropriate checklists. I usually perform the final setup on the #1 pfd (changing to short-range nav / green needle) and final course tuning) to be done once I am given a vector off of the RNAV arrival by ATC. Everything during my setup was normal; checklists were completed to current stage of flight and all flight phases were normal to this point.shortly thereafter; ATC assigned heading 110 degrees to join the localizer 10R; descend and maintain 5;000 feet. I tuned the #1 pfd heading bug to 110 degrees and selected heading mode on the flight director controller; tuned 5;000 feet in the altitude alerter and started a descent using vertical speed mode on flight director controller; auto pilot still engaged as it had been since shortly after takeoff. I then changed #1 pfd from RNAV (purple needle) to short range nav (green needle) and attempted to tune the final approach course on my pfd to 096 degrees. The course needle would not move when I tried to tune it to 096. I verified my selection and could not immediately recognize why I was unable to tune the needle.I estimate 30 seconds went by while I tried to diagnose the problem.I looked over to the #2 pfd and realized I had flown through the 10R localizer and although not a full needle deflection yet; was south of course as I was still at 220 knots IAS. ATC had asked to keep speed up. I had not noticed passing through the localizer on my #1 backup nav CDI on the pilot side while I was distracted with the course needle tuning problem.I immediately turned the heading bug left to 075 degrees to rejoin the localizer just as ATC called and said I had flown thought the localizer. I don't recall what heading he gave me to rejoin; but it was close to what I had already adjusted to.I briefly attempted again to set the #1 course needle to the final approach course of 096 and was unsuccessful. This took just long enough; given my high speed that I flew back through the 10R localizer on the north side. Frustrated; I disconnected the autopilot and commenced a 30 degree right bank back to 100 degrees and in doing so flew right through my assigned 'descend to' altitude of 5;000 feet.the very frustrated (and rightly so) ATC controller called and said I had now blown through both the 10R and 10L localizers; and gave me a corrective heading to the east southeast; I believe of 110 degrees. ATC said frequency for 10R is 11.75; say assigned altitude. I replied 5;000 feet while noticing that I had descended to 4;400 feet and immediately began a climb back to 5;000 feet. ATC replied with instruction to descend to 4;000 feet. I confirmed 4;000 altitude and told him I had the correct frequency tuned.I continued to hand fly the aircraft rather than re-engaging the autopilot because I was still confused as to why I was unable to tune the course needle and what exactly the malfunction was. I did transition my attention to my backup pilot side nav 1 CDI and cross-checked with the #2 pdf CDI; and did join the 10R localizer; but was sloppy on altitude level off at 4;000; and deviated + / - 400 feet on the level off. I re-engaged the autopilot with heading and vs modes and flew the remainder of the approach without any further deviation and with autopilot engaged. Landing; taxi and shutdown were all normal.after shutdown and securing the airplane; I investigated further and determined the problem with tuning course needle to be mechanical in nature. The course selection knob has two very small allen screws that keep the actual knob secured to the inner knob that actually allows you to turn the needle. Both allen screws had loosened during flight; allowing the knob to turn without having any effect on the tuning of the course needle. All functions had checked normal on the preflight.corrective action to repair the malfunction was simply retightening the two allen screws.contributing factors:high workload situation; single pilot; night; MVFR / IFR; higher than normal speed due to ATC request and traffic conditions at the time for the arrival; complex phase of flight (flying RNAV arrival; descending and setting up both pilot flying and co-pilot side instruments for the approach; self-briefing the approach; etc.)human performance considerationsperceptions; judgments; decisions:1.I was not able to quickly determine the problem with tuning the pilot side pfd course needle to the final approach course and things were happening fast enough that I did not focus on the primary job of flying the airplane and telling ATC I needed help (i.e. Delay vector and time to diagnose and set up for non -standard cockpit approach.)2. Error in judgments and decisionsa. I allowed a very simple mechanical malfunction to distract my attention from the primary job of flying the airplane.b. I should have asked ATC for a delay vector to allow me time to diagnose the problem and eliminate any confusion and ensure that I was fully prepared to execute the instrument approach with a nonstandard condition in the cockpit before proceeding inbound on the approach.c. I should not have disengaged the autopilot to attempt a hand flown correction. Big mistake and is what set me up for the altitude deviations as I was still distracted and not 100% focused on flying the airplane.factor affecting human performance:1. Fatigue. I had been up since xa:30am and had high stress during the day dealing with a long-distance health crisis of a sibling; which likely had an impact on my fatigue levels and stress levels.2. Combination of fatigue; flight conditions high traffic environment and high workload and a single; very simple malfunction triggered and chain of bad decisions resulting in course and altitude deviations in a short period of time during a critical phase of flight.

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Original NASA ASRS Text

Title: CE-550 Captain reported the inability to select the localizer final approach course during a night IFR flight into FLL. The aircraft is allowed to fly through the localizer twice and descend below the assigned altitude while troubleshooting. The Copilot side's instruments are used to fly the approach successfully and post flight inspection reveals that the course set knob was turning on its shaft due to loose set screws.

Narrative: While on initial approach to FLL; after obtaining ATIS and having a normal descent and RNAV arrival; I was told by ATC to expect ILS 10R. I followed my standard single pilot procedure and sets both pilot and copilot sides up for the ILS 10R approach; tuned to proper frequency (111.75) for the ILS on #1 and #2 NAVs; identified both #1 and #2 NAVs for proper Morse code identifications; and tuned the #2 PFD to short-range nav (green needle) and tuned final approach course to 096 degrees for the ILS; set both #1 and #2 PFDs for DH of 250 feet for the approach.I did not set the #1 (Pilot side) PFD course needle at this time because I was still navigating on the RNAV arrival and my standard procedure is to stay in the mode that I'm navigating with (in this case RNAV with purple needle) and keep the autopilot and flight director coupled to the primary (#1 PFD) which allows me to focus attention on setting up the rest of the cockpit and running the appropriate checklists. I usually perform the final setup on the #1 PFD (changing to short-range nav / green needle) and final course tuning) to be done once I am given a vector off of the RNAV arrival by ATC. Everything during my setup was normal; checklists were completed to current stage of flight and all flight phases were normal to this point.Shortly thereafter; ATC assigned heading 110 degrees to join the localizer 10R; descend and maintain 5;000 feet. I tuned the #1 PFD heading bug to 110 degrees and selected HDG mode on the flight director controller; tuned 5;000 feet in the altitude alerter and started a descent using vertical speed mode on flight director controller; auto pilot still engaged as it had been since shortly after takeoff. I then changed #1 PFD from RNAV (purple needle) to short range nav (green needle) and attempted to tune the final approach course on my PFD to 096 degrees. The course needle would not move when I tried to tune it to 096. I verified my selection and could not immediately recognize why I was unable to tune the needle.I estimate 30 seconds went by while I tried to diagnose the problem.I looked over to the #2 PFD and realized I had flown through the 10R localizer and although not a full needle deflection yet; was south of course as I was still at 220 knots IAS. ATC had asked to keep speed up. I had not noticed passing through the localizer on my #1 backup nav CDI on the pilot side while I was distracted with the course needle tuning problem.I immediately turned the HDG bug left to 075 degrees to rejoin the localizer just as ATC called and said I had flown thought the localizer. I don't recall what heading he gave me to rejoin; but it was close to what I had already adjusted to.I briefly attempted again to set the #1 course needle to the final approach course of 096 and was unsuccessful. This took just long enough; given my high speed that I flew back through the 10R localizer on the north side. Frustrated; I disconnected the autopilot and commenced a 30 degree right bank back to 100 degrees and in doing so flew right through my assigned 'descend to' altitude of 5;000 feet.The very frustrated (and rightly so) ATC controller called and said I had now blown through both the 10R and 10L localizers; and gave me a corrective heading to the East Southeast; I believe of 110 degrees. ATC said frequency for 10R is 11.75; say assigned altitude. I replied 5;000 feet while noticing that I had descended to 4;400 feet and immediately began a climb back to 5;000 feet. ATC replied with instruction to descend to 4;000 feet. I confirmed 4;000 altitude and told him I had the correct frequency tuned.I continued to hand fly the aircraft rather than re-engaging the autopilot because I was still confused as to why I was unable to tune the course needle and what exactly the malfunction was. I did transition my attention to my backup pilot side Nav 1 CDI and cross-checked with the #2 PDF CDI; and did join the 10R localizer; but was sloppy on altitude level off at 4;000; and deviated + / - 400 feet on the level off. I re-engaged the autopilot with HDG and VS modes and flew the remainder of the approach without any further deviation and with autopilot engaged. Landing; taxi and shutdown were all normal.After shutdown and securing the airplane; I investigated further and determined the problem with tuning course needle to be mechanical in nature. The course selection knob has two very small allen screws that keep the actual knob secured to the inner knob that actually allows you to turn the needle. Both allen screws had loosened during flight; allowing the knob to turn without having any effect on the tuning of the course needle. All functions had checked normal on the preflight.Corrective action to repair the malfunction was simply retightening the two allen screws.Contributing factors:High workload situation; single pilot; night; MVFR / IFR; higher than normal speed due to ATC request and traffic conditions at the time for the arrival; complex phase of flight (flying RNAV arrival; descending and setting up both pilot flying and co-pilot side instruments for the approach; self-briefing the approach; etc.)Human Performance ConsiderationsPerceptions; judgments; decisions:1.I was not able to quickly determine the problem with tuning the pilot side PFD course needle to the final approach course and things were happening fast enough that I did not focus on the primary job of flying the airplane and telling ATC I needed help (i.e. delay vector and time to diagnose and set up for non -standard cockpit approach.)2. Error in judgments and decisionsa. I allowed a very simple mechanical malfunction to distract my attention from the primary job of flying the airplane.b. I should have asked ATC for a delay vector to allow me time to diagnose the problem and eliminate any confusion and ensure that I was fully prepared to execute the instrument approach with a nonstandard condition in the cockpit before proceeding inbound on the approach.c. I should NOT have disengaged the autopilot to attempt a hand flown correction. Big mistake and is what set me up for the altitude deviations as I was still distracted and not 100% focused on flying the airplane.Factor affecting human performance:1. Fatigue. I had been up since XA:30am and had high stress during the day dealing with a long-distance health crisis of a sibling; which likely had an impact on my fatigue levels and stress levels.2. Combination of fatigue; flight conditions high traffic environment and high workload and a single; very simple malfunction triggered and chain of bad decisions resulting in course and altitude deviations in a short period of time during a critical phase of flight.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.