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NTSB accident investigation · Burkhart Grob G 109B · Mokuleia, HI · March 8, 2017

Accident · No injuriesData collectionFinal report
Date
March 8, 2017, 13:30 local (23:30 UTC)
Place
Mokuleia, HI
Injuries
1 uninjured
Damage
Substantial damage
Phase of flight
Enroute
Aircraft
N109FHBurkhart Grob G 109B
Defining event
Enroute: Part(s) separation from AC
Weather
Visual (VMC) · Day
Status
Completed · report June 7, 2017
Report
Approved by Office Director
NTSB office
General Aviation Accidents
Parties
FAA
FAA report
20170308002989A
Case key
94843

From the NTSB’s public API. By law, NTSB reports can’t be used as evidence in lawsuits over the accident.

On this page

Probable cause

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.

Findings · 5

NTSB’s coded findings. Those marked are part of the probable cause; the rest are factors or other findings. Under each, the cases with the same finding.

Inspection: preflight inspectionPersonnel issues › Task performance · PilotBurkhart Grob G-109B: 1 caseAll aircraft: 551 casesProbable cause
Flight control system: rudder control systemAircraft › Aircraft systems · Fatigue/wear/corrosionBurkhart Grob G-109B: 1 caseAll aircraft: 93 casesProbable cause
Environmental issuesEnvironmental issues › Physical environment · Effect on equipmentBurkhart Grob G-109B: 1 caseAll aircraft: 24 cases

Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event is the one that best describes the accident. Under each, the cases with the same event anywhere in their sequence.

Analysis

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.

Factual narrative

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.

Aircraft

Registration
N109FH
Reported as
Burkhart Grob G 109B (UNDESIGNAT)
Category
Glider
Serial number
6367
Built
1985
Airframe hours
5,677.6
Engine
Grob 2500, 85 horsepower, reciprocating
Damage
Substantial damage
Flight
Personal · Part 91
Airworthiness certificate
Standard, Utility
Last inspection
Annual · January 15, 2016
Departed
HDH · Mokuleia, HI
Destination
HDH · Mokuleia, HI
Airport
HDH · Dillingham Airfield, runway 08, 9,007 × 75 ft, asphalt
Equipment
Handheld GPS

Matched to the registry by N-number and the event date; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.

Flight crew

As NTSB recorded them. NTSB leaves out names.

Role
Pilot
Age
35
Injuries
None
Certificates
Flight instructor, Commercial
Airplane ratings
Single-engine land
Instrument ratings
Airplane
Medical
Class 3, With waivers/limitations
Last flight review
February 23, 2017
Seat
Left
Flight hours
1,140 total · 326 in this make and model · 1,087 as pilot in command · 19 in the last 90 days · 5 in the last 30 days · 2 in the last 24 hours

Weather

Conditions
Visual (VMC) · Day
Wind
60° at 4 knots
Visibility
10 statute miles
Lowest ceiling
None
Temperature
75 °F, dew point 63 °F
Altimeter
30.01 inHg
Observed at
PHHI, 11 nm away

Docket · 6

The files NTSB released with the investigation on May 2, 2017, on NTSB’s docket system: statements, records, photos and specialists’ reports. 5.1 MB in all.

FAA reports on this event · 1

The FAA’s own accident and incident reports, matched to the aircraft by N-number and date.