# SDR ASAA2022042438114

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: April 24, 2022
- Submitted: April 26, 2022
- Operation: Air carrier
- Aircraft: [N494AS](https://openairdocs.org/aircraft/N494AS), registered now
- Make and model: Boeing 737990ER
- Aircraft serial: 41729
- Aircraft time: 22,730 hours, 7,007 cycles
- System (JASC): [2310 · HF Communications System](https://openairdocs.org/jasc/2310)
- Part: Tuning Unit
- Part number: G7404124
- Part serial: 18805
- Condition: Faulty
- Location: Flight Deck
- Part time: 22,722 hours, 7,005 cycles
- Stage of operation: NR
- How discovered: V
- Nature of condition: O
- Precautionary procedure: K
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/ASAA2022042438114

## Discrepancy

HF #1 RADIO INTERMITTENTLY + AUTOMATICALLY CHANGES THE " ACTIVE" FREQ FROM WHAT WAS MANUALLY SET(8843) TO 3254 WITH NO PILOT INPUT. HF#1 CONFIRMED TO WORK FINE + SELCAL FINE WHEN TESTED BUT KEEPS CHANGING THE ACTIVE FREQ FROM WHAT IS SET TO "3254" ON ITS OWN ABOUT EVERY 20 MINUTES OR SO. GROUNDED - YES. PERFORMED B737-900 FIM FOR HF TRANSCEIVER PER 23-11 NO FAULTS FOUND. REMOVED AND REPLACED TUNING PANEL PER B737-900 AMM 23-12-41. PERFORMED HF & VHF CALLS. OPS CHECK GOOD. NO AUTOMATIC FREQ CHANGES AFTER 20 MIN.

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