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20030326003729I

Incident · Minor damage
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FAA incident report · Cessna 421C · San Francisco, CA · March 26, 2003

FAA Aviation Safety Information Portal

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Date
March 26, 2003 · 16:00 local
Place
San Francisco, CA
Airport
San Francisco International
Phase of flight
Descent
Operating rules
Air taxi and commuter (Part 135)
Operator
JXKA
Damage
Minor damage
Aircraft
N988NP
Reported as
Cessna 421C
Reported engine
Continental GTSIO520C
Pilot’s flight hours
3,800 total1,580 in this make and model103 in the last 90 days

From the FAA’s Accident/Incident Data System (AIDS), through its Aviation Safety Information Portal, as reported. The NTSB investigates accidents separately, and its record of an accident is the fuller one. The aircraft is matched to the registry 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.

What happened

The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.

(-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.

As the FAA filed it

(-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.