Saturday, March 11, 2017

Grob G-109B, Terrapac Imagery LLC, N109FH: Accident occurred March 08, 2017 in Mokuleia, Hawaii

Aviation Accident Final Report - National Transportation Safety Board: https://app.ntsb.gov/pdf 

Investigation Docket - National Transportation Safety Board: https://dms.ntsb.gov/pubdms

Additional Participating Entity:

Federal Aviation Administration / Flight Standards District Office: Honolulu, Hawaii

Terrapac Imagery LLC: http://registry.faa.gov/N109FH

NTSB Identification: GAA17CA179
14 CFR Part 91: General Aviation
Accident occurred Wednesday, March 08, 2017 in Mokuleia, HI
Probable Cause Approval Date: 06/07/2017
Aircraft: BURKHART GROB G 109B, registration: N109FH
Injuries: 1 Uninjured.

NTSB investigators used data provided by various entities, including, but not limited to, the Federal Aviation Administration and/or the operator and did not travel in support of this investigation to prepare this aircraft accident report.

The pilot, who was the owner of the powered glider, reported that, during the preflight, he “did not note any anomalies or irregular motion of the control surfaces.” He added that, during a turn in cruise flight, the rudder pedals “abruptly became unusual.” He looked to the rear of the powered glider and saw that the rudder had detached from the top of the vertical stabilizer. He added that the adverse yaw was “mild,” so he continued to land. During the landing roll, the rudder separated from the empennage.

Photographs provided by the Federal Aviation Administration showed extensive corrosion on the rudder hinges. The upper hinge showed a clean fracture surface on both the rudder and vertical stabilizer sides of the hinge. 

The pilot reported that he has an outdoor tie-down space on the airport where he parks the powered glider. The airport is located in a marine environment, less than 1/2 mile from the Pacific Ocean. 

The flight manual section titled, “Daily Inspections,” stated, in part:

Prior to flight operations the following visual exterior checks have to be performed…

5. Tail unit
Proper installation
Securely locked
Control connections locked
Freedom of movement
Damage
Pitot pressure tube (vertical fin) checked, cover remove

A review of maintenance records revealed that the most recent annual inspection was completed about 14 months before the accident. The most recent inspection performed on the powered glider was a 6,000-hour “Extension of Life Time” inspection, which was performed about 9 months before the accident. In the 6,000-hour inspection checklist, all line items were initialed “satisfactory” except for the “visual check for any decay” line items for the aileron, controls in the fuselage, elevator/trim tab, and rudder, which were left uninitialed. 

The mechanic who performed the most recent annual inspection and the 6,000-hour “Extension of Life Time” inspection reported that he did not notice anything abnormal during either inspection and that, during the 6,000-hour inspection, he did not carry his initials down to the “visual check for any decay” line items but that they were performed and that the condition looked “satisfactory.” He added that he believed the corrosion was responsible for the upper rudder hinge failure and that it is not uncommon for that amount of corrosion to form between the time of the most recent inspection and the accident flight. He recommended that the glider should have been inspected more often and rinsed with water daily to remove any salt residue from ocean spray.

In followup e-mail correspondence, the pilot reported that he believed that, during the “Extension of Life Time” inspection, all inspections had been renewed. He added that he learned after the accident that the annual inspection had not been performed.

The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
The failure of the upper rudder hinge during flight due to severe corrosion. Contributing to the accident were the pilot’s inadequate preflight inspection and the lack of an annual inspection.

The pilot, who was the owner, of the powered glider reported that during the preflight he "did not note any anomalies or irregular motion of the control surfaces". He added that during a turn in cruise flight the rudder pedals "abruptly became unusual". He looked to the rear of the powered glider and saw that the rudder had detached from the top of the vertical stabilizer. He further added that the adverse yaw was "mild", so he continued to land. During the landing roll, the rudder separated from the empennage.

Photographs of the rudder hinges provided by the FAA showed extensive corrosion on the hinges. The upper hinge showed a clean fracture surface on both the rudder and vertical stabilizer sides of the hinge. 

The pilot reported that he has an outdoor tie-down space on the airport where he parks the powered glider. The airport is located in a marine environment, less than one-half mile from the Pacific Ocean. 

The flight manual section Titled "Daily Inspections" stated in part: "Prior to flight operations the following visual exterior checks have to be performed…

5. Tail unit

• Proper installation

• Securely locked

• Control connections locked

• Freedom of movement

• Damage

• Pitot pressure tube (vertical fin) checked, cover remove"

A review of maintenance records revealed that the most recent annual inspection was completed about 14 months before the accident. The most recent inspection performed on the powered glider was a 6000-hour "Extension of Life Time" inspection, which was performed about 9 months prior to the accident. In the 6000-hour inspection checklist, all line items were initialed "satisfactory" with the exception of the "visual check for any decay" line items for the aileron, controls in the fuselage, elevator/trim tab, and rudder, which were left un-initialed. 

The mechanic who performed the most recent annual inspection and the 6000-hour "Extension of Life Time" inspection reported that he did not notice anything abnormal during either inspection and that during the 6000-hour inspection he did not carry his initials down to the "visual check for any decay" line items, but they were performed and the condition looked "satisfactory". He added that he believed the corrosion was responsible for the upper rudder hinge failure and that it is not uncommon for that amount of corrosion to form between the time that the most recent inspection was performed and the accident flight. He recommended that the glider should have been inspected more often and rinsed with water daily to remove any salt residue from ocean spray.

In a follow up email correspondence, the pilot reported that he believed that during the "Extension of Life Time" inspection, all inspections had been renewed. He added that only after the accident had he learned that the annual inspection had not been performed.

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