GLAESER NIEUPORT 11 near Gardner, KS — 2016-06-18

Probable cause

The pilot's diverted attention during the approach for the precautionary landing, which resulted in low airspeed, an exceedance of the airplane’s critical angle of attack, and a subsequent aerodynamic stall. Contributing to the accident was the control system vibration and the airplane’s lack of a stall warning system.

NTSB narrative

The private pilot stated that a preflight inspection of his experimental, amateur-built airplane revealed no discrepancies. After takeoff, the pilot completed two circuits around the airport traffic pattern with "no problems." During the upwind leg of the third circuit, he "noticed some vibration" and saw that the horizontal stabilizer was shaking/vibrating. The pilot began an approach for a precautionary landing, but during the base-to-final turn of the approach, the airplane experienced an aerodynamic stall. The pilot stated that he did not lose elevator control authority during the last legs of the flight but that he was "distracted" by a fear that parts may be separating from the airplane. The airplane, which was built from plans based upon a 100-year old design, was not equipped with a stall warning system. The pilot further reported that the flight control vibration was likely the result of the control cable that linked the two elevators in a "Y" configuration. He stated that the single control cable was not supported for "a number of feet" through guides/fairleads, which can make the elevators "flutter."

Analysis

Primary failure mode

Loss of control

First missed decision gate

Pilot could have chosen to land on runway 26 despite inbound traffic.

NTSB coding

• Flight control sys malf/fail · Approach-VFR pattern crosswind
• Attention / Monitoring

Evidence available

• 3 docket documents

Docket documents3

• Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1form
• Pilot and Witness Statementsinterview
• Record of Conversation - Pilotother