Boeing 747SP incident near Churchville, New York, April 29, 1991
On April 29, 1991 at about 4:00 pm local time, a Boeing 747SP, registered N148UA, suffered minor damage in an incident near Churchville, New York. It was a flight of an unrecorded kind under scheduled airline rules (Part 121). No one was hurt; 102 people were on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
A FAILURE OF THE SIXTH ROTATING AIRSEAL WHICH LED TO AN UNCONTAINED ENGINE FAILURE.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- April 29, 1991 · about 4:00 pm local time
- Place
- Churchville, New York · map
- Type
- Incident
- Injuries
- No one was hurt; 102 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Boeing 747SP · all 747SPs on the register
- Registration
- N148UA · no longer on the register · serial 21648
- Damage
- Minor damage
- Flight
- Flight of an unrecorded kind · scheduled airline rules (Part 121)
The NTSB's narrative final · quoted from the NTSB record
THE BOEING 747SP HAD JUST LEVELED OFF AT FL350 AND WAS ACCELERATING FROM M.81 TO M.85. DURING THE ACCELERATION, A VIBRATION WAS FELT IN THE COCKPIT AND CABIN. NO ABNORMAL ENGINE READINGS WERE OBSERVED. THE VIBRATION LASTED FOR ABOUT 2 MINUTES AND WAS FOLLOWED BY A LOUD BANG HEARD IN THE COCKPIT. THE NUMBER TWO ENGINE REVEALED A FAILED SIXTH ROTATING AIRSEAL. METALLURGICAL EXAMINATION OF FAILED AIRSEAL SHOWED FEATURES TYPICAL OF OVERSTRESS WITH NO INDICATION OF PREEXISTING CRACKS.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
Pilot
- Certificate: airline transport pilot
- Ratings: multi-engine land; instrument: airplane
- Flight time: 16,202 hours in all; 51 in the last 90 days
- Medical certificate: Class 1 (valid medical--w/ waivers/lim.)
- Seat: left
The aircraft
- Last inspection: continuous airworthiness programme, January 2, 2000
- Maximum gross weight: 702,000 lb
- Landing gear: retractable
- Engine: P&W JT9D-7ASP (turbofan); 0 hours total
- Operator: United Airlines
The flight
- Departed from: EWR Newark NJ
- Destination: TYO Tokyo, Japan
- Flight plan: IFR
- Runway 0
- A second pilot was aboard
Weather at the time
- Light: daylight
- Sky: not recorded; not recorded
- Temperature: 0°F (-18°C), dew point 0°F (-18°C)
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 18 | |||
| Passengers | 84 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.