Pilot Debrief

Sater Coot A-Amphib near San Andreas, CA — 2012-11-23

Final reportWPR13LA050
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Date
2012-11-23
Location
San Andreas, CA, USA
Airport
CPU
Aircraft
Sater Coot A-Amphib
Registration
N8VS
Category
Airplane
Highest injury
Fatal
Fatalities
1
Phase of flight
Maneuvering

Probable cause

The pilot's excessive flight control inputs, which led to flight that exceeded the structural limits of the airplane and resulted in structural failure of both wings.

NTSB narrative

A witness observed the airplane in a steep bank (estimated at between 60 and 80 degrees) while turning from the base leg to final approach in the traffic pattern. He then observed the airplane enter a spin and stated the airplane was in a near vertical nose-down attitude when the right wing separated from the airframe. Another witness reported that after the airplane’s first spin revolution, the leading edge came off of a wing and that during the second spin revolution the other wing separated. A postaccident examination of the airplane revealed that both wings had separated from the airplane about the same spanwise location (about 17 inches outboard of the wing attach points). The right wing’s front spar fracture face showed areas of tension and compression failures of the wood fibers that were consistent with the wing failing in a downward direction. Both the leading edge and front spar of the left wing had diagonal cuts through them that were consistent with having been struck by the airplane’s propeller. The inboard front spar fracture face was examined, but the fiber failures were destroyed by the ground impact, so a directionality of failure could not be determined. However, the propeller strike on the leading edge and front spar could only occur if the left wing failed upward into the propeller. There were no obvious signs of rot or preexisting conditions in the wood spars examined, and none of the wing attachment bolts failed. The witness reports indicating that the airplane was in a continuous steepening turn from the downwind leg to final approach immediately before the accident and the observed damage suggest that the pilot’s control inputs stressed the airplane’s wings beyond their design capabilities.

Analysis

Primary failure mode
Loss of control
First missed decision gate
Pilot could have decided against flying with landing gear retracted.

NTSB coding

Evidence available

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

Docket documents8

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