# Incident 20030326003729I: Cessna 421C, San Francisco, CA, March 26, 2003

- Type: FAA incident report (Accident/Incident Data System), as reported
- Date: March 26, 2003, 16:00 local time
- Place: San Francisco, CA
- Airport: San Francisco International
- Damage: Minor damage
- Phase of flight: Descent
- Operating rules: Air taxi and commuter (Part 135)
- Operator: JXKA
- Location: 37.6188° N, 122.3754° W: Placed by OpenAirDocs at SAN FRANCISCO INTL (SFO), within about a mile (OpenAirDocs)
- Nearby events: https://openairdocs.org/map.md?lat=37.6188&lon=-122.3754&mi=10
- Aircraft: N988NP (not matched to a registry record)
- Reported make and model: CESSNA 421C
- Reported engine: CONT GTSIO520C
- Pilot flight hours: 3,800 total, 1,580 in this make and model, 103 in the last 90 days
- FAA source: FAA Aviation Safety Information Portal (https://asip.faa.gov/)
- Page: https://openairdocs.org/incident/20030326003729I

## Narrative

As the FAA filed it, in capitals; the FAA replaces private details with ^PRIVACY DATA OMITTED^.

(-23) PILOT STATED THAT AT APPROXIMATELY 1600 HOURS, HE WAS IN LEVEL FLIGHT ON THE RIGHT DOWNWIND LEG TO RUNWAY 28R AT SFO AT 5,000 FEET MSL. HE EXTENDED THE LANDING GEAR, AND FLAPS IN PREPARATION FOR LANDING, AND HAD INITIATED A CLEARED DESCENT TO 4,000 FEET AT 130 KNOTS. SHORTLY THEREAFTER, HE HEARD A LOUD BANG, AND THE AIRCRAFT MADE AN UNCOMMANDED RIGHT ROLL. HE RECOVERED THE AIRCRAFT TO LEVEL FLIGHT, AND VISUALLY DETERMINED THAT THE LEFT FLAP WAS FULLY EXTENDED AND DOWN, WHILE THE RIGHT FLAP WAS UP AND IN TRAIL. THE FLAPS WOULD NOT RETRACT, AT WHICH TIME MR. CLARY ADVISED APPROACH CONTROL OF HIS SITUATION, AND REQUESTED THAT EMERGENCY EQUIPMENT STAND BY AS A PRECAUTION. HE THEN LANDED THE AIRCRAFT WITHOUT FURTHER INCIDENT. THERE WERE NO INJURIES TO ANY OF THE OCCUPANTS OF THE AIRCRAFT. IT WAS ASCERTAINED VIA INSPECTION, BY MATHER AVIATION, THE ROBERTSON FLAP SYSTEM WAS DISCONNECTED ON THE RH SIDE DUE TO FAILURE OF THE TORQUE TUBE. INSPECTION OF THE RH TUBE REVEALED A STRESS CRACK STILL DEVELOPING BY THE FAILED AREA, AND THE LH TORQUE TUBE WAS CRACKED WITHIN 30% OF ITS CIRCUMFERENCE.

From the FAA Accident/Incident Data System. Reports are matched to registry aircraft by N-number and event date, checked against the reported make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. For accidents, the NTSB's own investigation is the fuller record.

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