Narrative:

[We were] descending via the chsne 2 RNAV arrival/landing south into bna. The current meteorological conditions at the airport were VMC and the crew had expected a visual approach. The first officer (pilot flying) had thoroughly briefed the arrival and approach prior to the top of descent (TOD). The plan was to include the chsne 2 RNAV arrival followed by the RNAV (rnp) Z runway 20R since the approach is efficient; and often used for downwind entries for landing. Upon initial check-in with approach control; the captain (pilot monitoring) requested the RNAV (rnp) Z 20R to which approach control deferred to the final controller. As a result of the specific request; no runway assignment was given. Once control was switched to the final controller; the RNAV (rnp) Z 20 right approach was denied and an 'expect vectors for a visual approach to runway 20R' was issued. The first officer (PF) elected to change the FMC to reflect ILS runway 20R as a backup reference late on the arrival. The captain (pm) questioned the necessity for changing the FMC; but ultimately acknowledged its proper selection. In questioning its necessity the captain (pm) failed to ensure that the new entry was viewed on the legs page prior to execution. This distraction caused the crew not to recognize that a discontinuity had ensued and the LNAV and VNAV modes to cease at the nuvoo turn point. The captain (pm) recognized the error and intervened by quickly selecting heading select to regain lateral track and re-establishing RNAV guidance which now made the 5000 feet. Altitude restriction at joglo difficult to meet. As result [we] encountered both a lateral and vertical deviation. There are many items that contributed to the flight deviation; 1. Interaction with approach control which created late changes. 2. Risk management and unnecessary FMC programming. 3. Poor pilot monitoring to mitigate the risks. 4. A FMC that is poorly designed. Unfortunately; this is not my first time in writing such an as soon as possible. I am frustrated at myself for failing to properly monitor and stop such errors from occurring. I became distracted and questioned the need for the first officer (PF) to reprogram the FMC at a critical point and should have intervened. It was a good learning point for myself and a great learning point for a new first officer. We will continue to learn and attempt to mitigate such errors in the future. If [our company] is equally interested in managing risk; then this should be an important design flaw that could be addressed. There should be no reason why a discontinuity on the arrival is encountered while entering a different approach to the same runway. Additionally; there should be some caution that signifies the automation going to a 'stupid mode'. We continue to learn and improve our [resource management]; but we are always introducing new/inexperienced pilots. The one factor that remains constant is a poorly designed system!

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Original NASA ASRS Text

Title: B737-800 Captain reported track and altitude deviations occurred on arrival into BNA when ATC issued a late runway change.

Narrative: [We were] descending via the CHSNE 2 RNAV Arrival/landing south into BNA. The current meteorological conditions at the airport were VMC and the Crew had expected a visual approach. The First Officer (Pilot Flying) had thoroughly briefed the arrival and approach prior to the Top of Descent (TOD). The plan was to include the CHSNE 2 RNAV Arrival followed by the RNAV (RNP) Z Runway 20R since the approach is efficient; and often used for downwind entries for landing. Upon initial check-in with Approach Control; the Captain (Pilot Monitoring) requested the RNAV (RNP) Z 20R to which Approach Control deferred to the Final Controller. As a result of the specific request; no runway assignment was given. Once control was switched to the Final Controller; the RNAV (RNP) Z 20 R Approach was denied and an 'Expect vectors for a visual approach to Runway 20R' was issued. The First Officer (PF) elected to change the FMC to reflect ILS Runway 20R as a backup reference late on the arrival. The Captain (PM) questioned the necessity for changing the FMC; but ultimately acknowledged its proper selection. In questioning its necessity the Captain (PM) failed to ensure that the new entry was viewed on the LEGS page prior to execution. This distraction caused the Crew not to recognize that a discontinuity had ensued and the LNAV and VNAV modes to cease at the NUVOO turn point. The Captain (PM) recognized the error and intervened by quickly selecting Heading Select to regain lateral track and re-establishing RNAV guidance which now made the 5000 feet. Altitude restriction at JOGLO difficult to meet. As result [we] encountered both a lateral and vertical deviation. There are many items that contributed to the flight deviation; 1. Interaction with Approach Control which created late changes. 2. Risk management and unnecessary FMC programming. 3. Poor Pilot Monitoring to mitigate the risks. 4. A FMC that is poorly designed. Unfortunately; this is not my first time in writing such an ASAP. I am frustrated at myself for failing to properly monitor and stop such errors from occurring. I became distracted and questioned the need for the First Officer (PF) to reprogram the FMC at a critical point and should have intervened. It was a good learning point for myself and a great learning point for a new First Officer. We will continue to learn and attempt to mitigate such errors in the future. If [our company] is equally interested in managing risk; then this should be an important design flaw that could be addressed. There should be NO reason why a discontinuity on the arrival is encountered while entering a different approach TO THE SAME RUNWAY. Additionally; there should be some caution that signifies the automation going to a 'Stupid Mode'. We continue to learn and improve our [resource management]; but we are always introducing new/inexperienced pilots. The one factor that remains constant is a poorly designed system!

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.