Boeing 747-122 incident near San Francisco, California, June 12, 1984
On June 12, 1984 at about 4:30 am local time, a Boeing 747-122, registered N4712U, suffered minor damage in an incident near San Francisco, California. It was a flight of an unrecorded kind under scheduled airline rules (Part 121). No one was hurt; 4 people were on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The NTSB has not yet published a probable cause for this incident. Investigations usually take one to two years; this page updates when the final report is released.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- June 12, 1984 · about 4:30 am local time
- Place
- San Francisco, California · map
- Type
- Incident
- Injuries
- No one was hurt; 4 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Boeing 747-122 · all 747-122s on the register
- Registration
- N4712U · no longer on the register · serial 19757
- Damage
- Minor damage
- Flight
- Flight of an unrecorded kind · scheduled airline rules (Part 121)
The NTSB's narrative final · quoted from the NTSB record
JUST INSIDE THE OUTER MARKER, A 'LOUD BANG' WAS HEARD & LEFT AILERON INPUT WAS NEEDED TO CONTROL ACFT HEADING. THE LANDING WAS MADE WITHOUT INCIDENT UNTIL THE FLAPS WERE RAISED WHILE TAXIING & THE FLT ENGINEER REPORTED A #4 HYDRAULIC SYSTEM FAILURE. THE CAPT LOST BRAKES AND HAD TO UTILIZE STANDBY BRAKES. AT THIS TIME A SPLIT FLAP INDICATION WAS OBSERVED. INSPECTION REVEALED FLAP TRACK FRACTURED APRX 6 INCHES AFT OF THE FORWARD ATTACH POINT. THE FRACTURE INITIATEDON OUTBOARD FLANGE #1 BOLTHOLE WALL BECAUSE OF PITTING CORROSION. A PORTION OF THE FORE FLAP & A SMALL WING PANEL SEPARATED FROM THE ACFT. DURING FLAP RETRACTION AFTER LANDING, THE TRANSMISSION BALL NUT JAMMED. THE DRIVE TORQUE TUBE FRACTURED AT THIS TIME AND THE BROKEN END OF THE ROTATING TORQUE TUBE DAMAGED HYDRAULIC LINES, CAUSING A LOSS OF HYDRAULIC FLUID. AN ALERT SERVICE BULLETIN WAS ISSUED BY BOEING AFTER THIS INCIDENT & UNITED AIRLINES INITIATED A FLEET WIDE INSPECTION.
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: 31,140 hours in all
- Medical certificate: Class 1 (valid medical--w/ waivers/lim.)
- Seat: left
The aircraft
- Airframe total time: 45,436 hours
- Last inspection: approved inspection programme, January 27, 1984; 1,178 hours since
- Maximum gross weight: 775,000 lb
- Seats: 429
- Landing gear: retractable
- Engine: P&W JT9D-3 (turbofan); 0 hours total
- Operator: United Airlines
The flight
- Departed from: HNL Honolulu HI at 11:40 pm
- Destination: SFO San Francisco CA
- Flight plan: IFR
- Runway 0
- A second pilot was aboard
Weather at the time
- Light: dusk
- Wind: from 280° at 25 knots
- Visibility: 15 statute miles
- Sky: clear
- Temperature: 55°F (13°C), dew point 45°F (7°C)
- Altimeter: 29.00 inHg
- Observation at 3:53 am from SFO, 5 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 3 | |||
| Passengers | 1 |
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.