Pilot Debrief

NORTH AMERICAN TB-25N near Georgetown, DE — 2011-09-04

Final reportERA11LA484
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Date
2011-09-04
Location
Georgetown, DE, USA
Airport
GED
Aircraft
NORTH AMERICAN TB-25N
Registration
N9079Z
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Landing

Probable cause

Maintenance personnel's inadequate examination of the main landing gear during the airplane’s most recent conditional inspection, which resulted in the fatigue failure of the right main landing gear shock strut drag arm during the landing roll.

NTSB narrative

According to both pilots, they landed the airplane and felt the right wing drop during the landing roll. They attempted to maintain directional control, but the right wing dropped further and the airplane veered off of the right side of the runway. During a subsequent examination of the wreckage, the right main landing gear shock strut drag arm was found broken. An examination of the broken drag arm revealed that it fractured in the I-beam at the blend radius of an orthogonal arm due to bending fatigue. Given the extent of fatigue crack propagation in the flange of the I-beam, it is likely that the fracture occurred due to high-cycle, low-stress fatigue. Since the depth of the fatigue crack was significant relative to the I-beam flange thickness, the fatigue crack probably developed and propagated over a long time under numerous low-stress cycles. The most recent inspection of the main landing gear was on July 7, 2011, which was in accordance with a conditional inspection. The inspection required a mechanic to verify the condition and security of the main landing gear. It is most likely that the fatigue crack would have been detectable at the time of that inspection.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Inspect landing gear more thoroughly before the flight.

NTSB coding

Evidence available

  • Photos
  • 11 docket documents
View NTSB final reportView NTSB docket

Docket documents11

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