Pilot Debrief

ZENITH STOL CH701 near Ambler, AK — 2020-05-31

Final reportANC20LA053
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Date
2020-05-31
Location
Ambler, AK, USA
Aircraft
ZENITH STOL CH701
Registration
N324WS
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Takeoff roll

Probable cause

The pilot’s improper decision to take off from unsuitable terrain, which resulted in impact with uneven terrain, the subsequent failure of the nosewheel fork, and a nose over.

NTSB narrative

The pilot, who was also the owner and builder of the experimental amateur-built airplane, reported that he landed the airplane on sand dunes. Forty-five minutes later, he took off from the sand dunes, and during the takeoff roll, the airplane hit some bumps. Just before the airplane reached rotation speed, it hit a larger bump, which propelled it upward. The airplane then descended in a nose-high attitude and impacted terrain, followed immediately by the nose landing gear (NLG) collapsing. Subsequently, the airplane nosed over and came to rest inverted. Postaccident examination of the airplane revealed that the rudder and both wing struts sustained substantial damage. The nosewheel fork had separated from the nose strut in three fragments at two fracture locations, one on each side of the nose strut attachment. Examination of the fracture surfaces revealed that all the fractures exhibited features consistent with overstress fracture in upward bending of the nosewheel fork. No evidence of preexisting cracks, wear marks, or corrosion was found. The pilot reported that the accident may have been prevented if he had conducted a more “detailed” inspection of the takeoff area. Given the evidence, it is likely that, during the takeoff roll, the NLG impacted uneven terrain, which led to the airplane becoming airborne in a nose-up attitude and then impacting terrain with force that exceeded the nosewheel fork’s structural capabilities and resulted in the nosewheel fracturing.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Pilot could have conducted a more detailed inspection of the takeoff area.

NTSB coding

Evidence available

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

Docket documents4

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