Narrative:

Flight to las was taken off of the tyssn 3 RNAV arrival prior to prino; and given vectors northeast of the airport; to follow a B767. We were at 6000 ft and had other aircraft in sight. ATC told us to follow the 767; and cleared us directly to trrop to begin the RNAV visual to runway 19L. We subsequently lost sight of the 767; but the jumpseater kept calling out the aircraft's position. First he pointed towards las and said that the aircraft was just over the horizon - and there were two of them. The captain realized that what the jumpseater was actually looking at was the light from the solar mirror farms south of las. Realizing that the likelihood of there being two 767s in formation was nil; the captain was correct. Now; turning over trrop the jumpseating captain; again; inserted himself into conversation; and pointed out the aircraft on the arrival. Meanwhile; the captain selected and verbalized LNAV/VNAV path; zeroes set. As we approached eastr; the captain said; 'sure looks like we are high doesn't it?' and I agreed. We had a brief conversation about having seen this before at another airport; but both agreed that we looked very high. I mentioned that we were at 4500 ft approaching eastr; and the charted altitude said to cross eastr at 3500 ft. VNAV path showed us exactly on the path. As soon as we crossed eastr though; the VNAV deviation indicator moved rapidly to the bottom of the scale and showed us full scale high! The jumpseater again inserted himself into the conversation - now giving advice to the flying captain. 'Oh yeah; this is normal I see it all of the time. You're on a visual; just square it off and you will be fine'. We began to maneuver off of the RNAV lateral course; as the captain fully configured the aircraft; and tried to establish a good rate of descent.not seeing how we would be able to be stabilized by 1000 ft; I called for a go-around and the captain agreed. We executed a missed approach and ATC cleared us to 6000 ft on a runway heading and then proceeded to ask a bunch of questions regarding why we went around and what assistance we needed. I answered one or two; and then told him we would get back with him. The captain continued to hand fly the aircraft to 6000 ft; where he leveled off. Meanwhile I started setting up the aircraft for an RNAV visual for runway 25. When I looked up I noticed that our altitude was 6200 ft; I offered to engage the autopilot for the captain. To say that we were in the red would be an understatement. The addition of the third crew member added to the confusion and made things worse. Once the autopilot was engaged; we were radar vectored to follow an airbus. ATC kept us very close to the airbus and we quickly slowed and configured to safely follow. We turned final; and I cleaned up the FMS to meeup on the ILS 7R. During our maneuvering though; VNAV disconnected and the captain was left without vertical guidance on this visual approach. Unable to restore a glidepath to 7R for him; I gave him DME/altitude call outs ('3 miles from the runway; should be at 900 ft AGL; 2 miles; should be at 600 ft AGL; etc..')I have to add that during the missed approach; the captain's company issued headset broke (literally snapped) so he did not have a usable microphone; and had only one ear piece. Could anything else have gone wrong? This was leg three of four; on a rerouted trip after a minimum overnight the night before. Furthermore; we had been involved in a diversion and a 6.5 hour delay to finish our trip the night before. We were tired; so I will submit a fatigue report under separate cover. We think that we failed to recruise the FMC once we were taken off of the arrival; and that created an improper VNAV path; however; given that the VNAV was managing a descent to the next constraint (eastr at 3500) neither of us could figure out why. Further; once we began to get task saturated we should have asked the jumpseater to remain quiet unless he had critical safety information to offer.

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Original NASA ASRS Text

Title: B737-700 flight crew reported the events leading up to a go-around for an unstabilized RNAV Runway 19 Visual Approach to LAS. The reporter cited distractions from the jumpseater and the solar array along with FMC programing and fatigue as factors in the unstabilized approach.

Narrative: Flight to LAS was taken off of the TYSSN 3 RNAV Arrival prior to PRINO; and given vectors northeast of the airport; to follow a B767. We were at 6000 ft and had other aircraft in sight. ATC told us to follow the 767; and cleared us directly to TRROP to begin the RNAV Visual to Runway 19L. We subsequently lost sight of the 767; but the Jumpseater kept calling out the aircraft's position. First he pointed towards LAS and said that the aircraft was just over the horizon - and there were two of them. The Captain realized that what the Jumpseater was actually looking at was the light from the solar mirror farms south of LAS. Realizing that the likelihood of there being two 767s in formation was nil; the Captain was correct. Now; turning over TRROP the Jumpseating Captain; again; inserted himself into conversation; and pointed out the aircraft on the arrival. Meanwhile; the Captain selected and verbalized LNAV/VNAV PATH; ZEROES SET. As we approached EASTR; the Captain said; 'sure looks like we are high doesn't it?' and I agreed. We had a brief conversation about having seen this before at another airport; but both agreed that we looked very high. I mentioned that we were at 4500 ft approaching EASTR; and the charted altitude said to cross EASTR at 3500 ft. VNAV PATH showed us exactly on the path. As soon as we crossed EASTR though; the VNAV deviation indicator moved rapidly to the bottom of the scale and showed us full scale high! The Jumpseater again inserted himself into the conversation - now giving advice to the flying Captain. 'Oh yeah; this is normal I see it all of the time. You're on a visual; just square it off and you will be fine'. We began to maneuver off of the RNAV lateral course; as the Captain fully configured the aircraft; and tried to establish a good rate of descent.Not seeing how we would be able to be stabilized by 1000 ft; I called for a go-around and the Captain agreed. We executed a missed approach and ATC cleared us to 6000 ft on a runway heading and then proceeded to ask a bunch of questions regarding why we went around and what assistance we needed. I answered one or two; and then told him we would get back with him. The Captain continued to hand fly the aircraft to 6000 ft; where he leveled off. Meanwhile I started setting up the aircraft for an RNAV Visual for Runway 25. When I looked up I noticed that our altitude was 6200 ft; I offered to engage the autopilot for the Captain. To say that we were in the Red would be an understatement. The addition of the third Crew Member added to the confusion and made things worse. Once the autopilot was engaged; we were radar vectored to follow an Airbus. ATC kept us very close to the Airbus and we quickly slowed and configured to safely follow. We turned final; and I cleaned up the FMS to MEEUP on the ILS 7R. During our maneuvering though; VNAV disconnected and the Captain was left without vertical guidance on this visual approach. Unable to restore a glidepath to 7R for him; I gave him DME/altitude call outs ('3 miles from the runway; should be at 900 ft AGL; 2 miles; should be at 600 ft AGL; etc..')I have to add that during the missed approach; the Captain's Company issued headset broke (literally snapped) so he did not have a usable microphone; and had only one ear piece. Could anything else have gone wrong? This was leg three of four; on a rerouted trip after a minimum overnight the night before. Furthermore; we had been involved in a diversion and a 6.5 hour delay to finish our trip the night before. We were tired; so I will submit a fatigue report under separate cover. We think that we failed to recruise the FMC once we were taken off of the arrival; and that created an improper VNAV PATH; however; given that the VNAV was managing a descent to the next constraint (EASTR at 3500) neither of us could figure out why. Further; once we began to get task saturated we should have asked the Jumpseater to remain quiet unless he had critical safety information to offer.

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.