- Date
- June 11, 1984, 21:30 local (Jun 12, 1984, 04:30 UTC)
- Place
- San Francisco, CA
- Injuries
- 4 uninjured
- Damage
- Minor damage
- Phase of flight
- Approach
- Aircraft
- N4712UBoeing 747-122
- Weather
- Visual (VMC) · Dusk
- Status
- Completed
- Report
- Approved by Office Director
- Case key
- 24044
From the NTSB’s public API. By law, NTSB reports can’t be used as evidence in lawsuits over the incident.
On this page
Sequence of events
NTSB’s coding before 2008: each occurrence and phase of flight, and the causes and factors under it. The codes are defined in NTSB’s coding manual.
Analysis
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.
Aircraft
- Registration
- N4712U
- Reported as
- Boeing 747-122
- Category
- Airplane
- Serial number
- 19757
- Airframe hours
- 45,436
- Engine
- P&W JT9D-3, turbo fan
- Damage
- Minor damage
- Flight
- Part 121
- Operator
- United Airlines
- Registered owner
- Banker Trust Co. Trustee
- Airworthiness certificate
- Standard, Transport
- Last inspection
- AAIP · January 27, 1984 · 1,178 hours before
- Departed
- HNL · Honolulu, HI
- Destination
- SFO · San Francisco, CA
- Flight plan
- IFR
Flight crew
As NTSB recorded them. NTSB leaves out names.
- Role
- Pilot
- Age
- 59
- Certificate
- Airline transport
- Airplane ratings
- Multi-engine land
- Instrument ratings
- Airplane
- Medical
- Class 1, Valid Medical--w/ waivers/lim
- Seat
- Left
- Flight hours
- 31,140 total
Weather
- Conditions
- Visual (VMC) · Dusk
- Wind
- 280° at 25 knots
- Visibility
- 15 statute miles
- Lowest ceiling
- None
- Temperature
- 55 °F, dew point 45 °F
- Altimeter
- 29.00 inHg
- Observed at
- SFO, 5 nm away