# SDR SWAA2023091400024

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: September 12, 2023
- Submitted: September 14, 2023
- Operation: Air carrier
- Aircraft: [N8656B](https://openairdocs.org/aircraft/N8656B), registered now
- Make and model: Boeing 737-8H4
- Registry model: [Boeing 737-8H4](https://openairdocs.org/model/boeing-737-8h4) (OpenAirDocs)
- Aircraft serial: 42530
- Aircraft time: 27,895 hours, 12,976 cycles
- System (JASC): [3400 · Navigation System](https://openairdocs.org/jasc/3400)
- Part: Probe
- Part number: UNKNOWN
- Condition: Inoperative
- Location: Zn 200 Fus Top
- Stage of operation: CL
- How discovered: 9
- Nature of condition: O
- Precautionary procedure: D, O
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/SWAA2023091400024

## Discrepancy

ON CLIMBOUT (JUST AFTER LIFT OFF) WE LOST LNAV/VNAV AND FLIGHT DIRECTOR ON BOTH CA + FO DISPLAY. AROUND 1000FT WE LOST AUTHOTHROTTLE. AFTER A FEW TRIES WE REGAINED LNAV ONLY. WE LEVELED 10000 REGAINED A/T THEN LOST IT A SECOND TIME AND WAS UNABLE TO GET IT BACK. WE DECIDED TO RETURN TO LAS AND DECLARE AN EMERGENCY. WE HAD A SMOOTH APPROACH AND NORMAL LANDING. WE DID NOT LAND OVERWEIGHT. WE NEVER GOT THE VNAV BACK. AIRPORT EMERGENCY VEHICLES WERE PRESENT AT LANDING AND FOLLOWED US TO THE GATE.<[01] R&R?D LEFT ADIRU PER AMM 34-21-01 AND R&R?D TAT PROBE PER AMM 34-21-06

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