# SDR 2004UALA00406

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: April 27, 2004
- Submitted: May 5, 2004
- Operation: Air carrier
- Aircraft: [N773UA](https://openairdocs.org/aircraft/N773UA), registered now
- Make and model: Boeing 777222
- Aircraft serial: 26929
- Aircraft time: 34,736 hours, 7,681 cycles
- Engine: Pwa PW4077
- System (JASC): [7200 · Engine (Turbine/Turboprop)](https://openairdocs.org/jasc/7200)
- Part: Seal
- Condition: Failed
- Location: Nr 1 Engine
- Stage of operation: NR
- How discovered: O
- Nature of condition: E
- Precautionary procedure: J, A
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/2004UALA00406

## Discrepancy

NR 1 ENGINE N1 VIBRATIONS. 6TH STAGE TURBINE AIRSEAL FAILURE REF: PW4074/77 IPC (PN 51A346)  72-53-00 FIGURE 7, ITEM 70A. A 4-INCH AXIAL BY 6-INCH CIRCUMFERENTIAL PIECE OF THE SEAL HAD BROKEN OUT & WAS MISSING. THE REMAINDER OF THE LPT SUFFERED HEAVY DOWNSTREAM DAMAGE. THE SEAL WAS OF THE POST SERVICE BULLETIN PW4G-112-72-171 CONFIGURATION. THIS IS A NEW FAILURE MODE.  THE 2ND SUCH FAILURE UA HAS SEEN. SEALS FROM BOTH FAILURES HAVE BEEN RETURNED TO PW & MTU FOR ROOT CAUSE ANALYSIS.

---
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.