Incident Overview
On June 1, 2009, at approximately 1500 eastern daylight time, a Cirrus Design Corp. SR22, registration N695CD, operated by SATSair LLC as a Title 14 Code of Federal Regulations Part 91 maintenance flight, experienced a control malfunction while on approach to Greenville Downtown Airport (GMU) in Greenville, South Carolina. The airplane was not damaged and the pilot, a certificated airline transport pilot, was not injured. Visual meteorological conditions prevailed and no flight plan was filed. The flight had departed from GMU at 1430.
Pilot Report
The pilot reported that he was returning the airplane to service following a maintenance inspection. No anomalies were noted during the preflight inspection, engine start, taxi, run-up, or takeoff roll. As the airplane became airborne, the pilot noticed that the elevator control felt "loose," with about 1/2 inch of "play." He proceeded to an area west of GMU and performed in-flight checks uneventfully.
On short final approach, the pilot reduced the throttle to idle power for landing. At about 25 feet above ground level, the nose pitched down. When the pilot attempted to pull back on the yoke to flare, the elevator control was stuck in the mid-range position. The airplane touched down on the nose gear first and bounced back into the air. The sudden jolt of the touchdown appeared to free the elevator control, and the pilot completed a normal landing. After taxiing from the runway, the pilot was able to duplicate the control jam.
Maintenance Findings
The operator's director of maintenance (DOM) reported that no work was performed on the pitch trim cartridge during the recent maintenance inspection. After the incident, the elevator pitch trim cartridge was removed. When the DOM actuated the cartridge by hand, he felt the spring functioning but noted that the control rod movement was "gritty." The anomaly did not reoccur after the pitch trim cartridge was removed and replaced.
Manufacturer Examination
The pitch trim cartridge was forwarded to the manufacturer's facility for examination under the supervision of a Federal Aviation Administration (FAA) inspector. The examination revealed some corrosion and black grease residue, but no conclusive evidence was found to support a flight control jam. Additionally, manufacturer representatives could not document the suspect cartridge as it was installed before it was removed and replaced. A manufacturer's representative noted that although the elevator control linkage moves through the pitch trim cartridge to the aft elevator bellcrank, an electric elevator trim motor moves the entire pitch trim cartridge and aft elevator bellcrank, providing system redundancy in the event of a primary elevator control malfunction.
Operator Actions
The DOM reported that the suspect pitch trim cartridge was the original cartridge installed on the airplane, which had been operated for 2,562 hours at the time of the event. Although the pitch trim cartridge was required to be inspected, there was no requirement to replace it at a specific time interval. After the incident, the operator implemented a voluntary program to remove and replace pitch trim cartridges at 2,000 hours of operation and forward the used cartridges to the manufacturer for examination.
Related Incidents
During the investigation, another operator reported similar issues pertaining to trim cartridge "sticking" involving five Cirrus airplanes. Those events occurred shortly after the new airplanes left the factory. Subsequent interviews with mechanics and an FAA inspector, along with further information from the second operator, revealed that one airplane had an elevator pitch trim cartridge sticking due to a lack of lubrication. Another airplane had a roll trim cartridge removed and replaced at the customer's request in an effort to troubleshoot a wing-rocking problem. The other three airplanes were noted to have trim cartridge (roll, yaw, and/or pitch) sticking possibly due to an aileron-rudder interconnect issue, cartridge misalignment, and/or debris particles becoming temporarily stuck in the cartridge.
A review of the National Transportation Safety Board database and FAA service difficulty reports for a 5-year period preceding the SATSair incident did not reveal any similar occurrences pertaining to sticking or temporary jamming of any Cirrus pitch trim cartridge.