# SDR SWAA2019121239560

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: December 11, 2019
- Submitted: December 12, 2019
- Operation: Air carrier
- Aircraft: N781WN
- Make and model: Boeing 737-7H4
- Registry model: [Boeing 737-7H4](https://openairdocs.org/model/boeing-737-7h4) (OpenAirDocs)
- Aircraft serial: 30601
- Aircraft time: 67,026 hours, 39,509 cycles
- System (JASC): [3421 · Attitude Gyro and Indicating System](https://openairdocs.org/jasc/3421)
- Part: Reference Unit
- Part number: HG2050AC07
- Part serial: 56002976
- Condition: Faulty
- Location: E&E Bay
- Stage of operation: DE
- How discovered: O
- Nature of condition: J
- Precautionary procedure: A
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/SWAA2019121239560

## Discrepancy

DIVERSION/DECLARED EMERGENCY-------------------------------------------------------------AT FL400 INDICATED AIR SPEED DISAGREE FLAG ON PRIMARY FLIGHT DISPLAY +- 5-6 KTS BETWEEN CAPTAIN/FIRST OFFICER/STANDBY AIR SPEED. DURING DESCENT CAPTAINS AIR SPEED GRADUALLY DECREASED TO 45KT, FIRST OFFICERS STANDBY INDICATED 250KT. CAPTAINS ALTITUDE 300-500FT HIGH. ELECTRONIC ENGINE CONTROL SYSTEM     / SHIFTED TO ALTITUDE MODE. CAPTAIN AIR SPEED & ALTITUDE REMAINED ERRONEOUS UNTIL 5000-8000FT WHEN THEY SEEMED NORMAL. / FOUND FAULTY LEFT AIR DATA INERTIAL REFERENCE UNIT PER AMM.

---
OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.