Kolb KOLB TWINSTAR TSP 1 N217JM

Summary

On 13 June 2019 at about 14:50 local time, a Kolb KOLB TWINSTAR TSP 1 registered N217JM was involved in an accident near Hector, Minnesota, United States. One person was on board and nobody was injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

13 June 2019 at 14:50

Classification

Accident

Location

Hector, Minnesota, United States

Nearest airport

Hector Muni (1D6)

Coordinates

44.7315, -94.7126

Aircraft

Kolb KOLB TWINSTAR TSP 1

Registration

N217JM

Category

Airplane

Year built

1986

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Flight Test

Phase of flight

Not recorded

Route

Hector → Unknown

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

CEN19LA176

Nobody was injured.

The pilot’s operation of the airplane outside of the center of gravity limits, which resulted in an adverse aerodynamic condition and subsequent hard landing. Contributing to the accident was the pilot’s incorrect calculations of the airplane’s CG limits.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

The pilot was conducting a maintenance test flight and had been in the air about 15 minutes when airplane began to oscillate up and down. He had difficulty maintaining control, so he made a rapid descent toward the airport. During the rapid descent the oscillation and shaking reduced, but as he decreased the descent rate, the airplane oscillated violently. The airplane landed hard on the grass runway. The airplane sustained substantial damage to the wings, fuselage, and empennage. After the accident, the pilot stated that he thought the tail boom had fractured inflight. A postaccident examination of the airframe revealed that the tubular empennage structure had fractured and was separated. An examination of the fractured section determined that the fractures were due to overstress as a result of the hard landing. A review of the pilot’s calculated weight and balance information revealed that the pilot had incorrectly calculated the weight and balance and that the airplane’s center of gravity (CG) was aft of manufacturer limitations. After the accident, the pilot reported that he was adjusting his CG while airborne, and he placed a bag of bird seed in the passenger seat to assist during the inflight test. The bag was aft of the datum per the manufacturers specifications and would have moved the CG further aft. This likely resulted in an adverse aerodynamic condition and an uncontrollable pitch oscillation.

Quoted verbatim from the NTSB record.