# SDR ASAA2021091535958

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: September 15, 2021
- Submitted: September 17, 2021
- Operation: Air carrier
- Aircraft: [N419AS](https://openairdocs.org/aircraft/N419AS), registered now
- Make and model: Boeing 737990ER
- Aircraft serial: 41734
- Aircraft time: 31,498 hours, 10,136 cycles
- System (JASC): [2210 · Autopilot System](https://openairdocs.org/jasc/2210)
- Part: Control Panel
- Part number: 4082260939
- Part serial: 34094531
- Condition: Inoperative
- Location: Autopilot
- Part time: 31 hours, 10 cycles
- Stage of operation: CR
- How discovered: O
- Nature of condition: J
- Precautionary procedure: O
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/ASAA2021091535958

## Discrepancy

DURING CURISE AT FL 370 WITH AUTOPILOT "B" ENGAGED AUTOPILOT DISENGAGED, F/O'S FLT DIRECTOR DISAPPEARED AND F/O'S HEADING BUG WOULD NOT RESPOND TO MCP INPUTS.. CAPT'S SIDE AND "A" AUTOPILOT FUNCTIONED NORMALLY. GROUNDED - YES. REMOVED & REPLACED DFCS MODE CONTROL B737-900 AMM 22-11-34. PULLED & RESET 9 ASSOCIATED C.B. PATCHED IN COAXIAL SWITCH RELAY 315 REF AMM 34-31-72. NO HELP REQUIRES FURTHER TROUBLESHOOTING. PULLED & RESET 9 TOTAL C/BS, RESET ENGAGE C/BS LAST. BOTH CAPT & F/O VOR & LOC/GS OPS CK NML USING IFR4000 RAMP TESTER & LAX AIRPORT FREQUENCIES. ACCOMPLISHED MCP LRU REPLACEMENT TEST (GP 32) REF AMM 22-11-34, DFCS LAND VERIFY TEST (GP 49) REF AMM 22-11-00 & HGS SYSTEM TEST REF SMM 34-36-00, OPS CK NML. AIRCRAFT RELEASED FROM MCT DEFERRAL, C/N 15024419. REF L/P 60294551 FOR A/C APPROACH SURVEY.

---
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.