B737-700 captain reported getting high during the las RNAV visual runway 19L although the FMC showed...

Narrative:

On arrival to las on the RNAV visual 19L; we encountered a VNAV error which forced a go-around for an unstable approach. At trrop we were at 6000 ft; 170 knots with all briefings completed in accordance with training standards. All fix altitudes were verified. We even had a captain on the jumpseat who also verified the programming. Arriving at trrop; we had 3;500 ft set for the next intermediate fix altitude at eastr. After passing trrop I verbalized and verified LNAV/VNAV and set zeros. The aircraft started the descent with LNAV/VNAV on. We were fully configured by towen and still showing on vertical path.I verbalized that it didn't feel right and looked high. The jumpseater said 'that's normal for this approach.' we both verified the fixes and all altitudes again. The aircraft continued in the desert on path until eastr; and then dropped off; we realized we were 1;000 ft high at eastr despite showing on path. I tried to correct the deviation but soon realized we would not be stabilized at 1;000 ft and executed the go-around. We debriefed the event at the gate with all three crew members and could not determine any technical or procedure error that was performed. I'm not sure if the anomaly was within the VNAV software; but something was definitely wrong with the information it was giving us.

Original NASA ASRS Text

Title: B737-700 Captain reported getting high during the LAS RNAV Visual Runway 19L although the FMC showed on path until EASTR then showed high. A go-around was initiated.

Narrative: On arrival to LAS on the RNAV VISUAL 19L; we encountered a VNAV error which forced a go-around for an unstable approach. At TRROP we were at 6000 ft; 170 knots with all briefings completed in accordance with training standards. All fix altitudes were verified. We even had a Captain on the jumpseat who also verified the programming. Arriving at TRROP; we had 3;500 ft set for the next intermediate fix altitude at EASTR. After passing TRROP I verbalized and verified LNAV/VNAV and set zeros. The aircraft started the descent with LNAV/VNAV on. We were fully configured by TOWEN and still showing on vertical path.I verbalized that it didn't feel right and looked high. The Jumpseater said 'That's normal for this approach.' We both verified the fixes and all altitudes again. The aircraft continued in the desert on path until EASTR; and then dropped off; we realized we were 1;000 ft high at EASTR despite showing on path. I tried to correct the deviation but soon realized we would not be stabilized at 1;000 ft and executed the go-around. We debriefed the event at the gate with all three Crew Members and could not determine any technical or procedure error that was performed. I'm not sure if the anomaly was within the VNAV software; but something was definitely wrong with the information it was giving us.

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.

Attributes
ACN	1373082
Time
Date	201607
Place
Locale Reference	LAS.Airport
State Reference	NV
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	B737-700
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Route In Use	Visual Approach
Flight Plan	IFR
Component
Aircraft Component	FMS/FMC
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 182 Flight Crew Type 4500
Events
Anomaly	Deviation - Altitude Crossing Restriction Not Met Deviation - Procedural Published Material / Policy Inflight Event / Encounter Unstabilized Approach

B737-700 captain reported getting high during the las RNAV visual runway 19L although the FMC showed on path until eastr then showed high. A go-around was initiated.