Lancair IV N549CJ

Summary

On 10 February 2019 at about 23:00 local time, a Lancair IV registered N549CJ was involved in an accident near Laramie, Wyoming, United States. 2 people were 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

10 February 2019 at 23:00

Classification

Accident

Location

Laramie, Wyoming, United States

Nearest airport

Laramie Regional (LAR)

Coordinates

41.2875, -105.6075

Aircraft

Lancair IV

Registration

N549CJ

Category

Airplane

Year built

2014

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

Casper → Denver

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

WPR19LA088

Nobody was injured.

An environmental stress cracking failure of the acrylic windshield, which resulted in a rapid decompression during cruise flight.

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

Read the full NTSB narrative

The pilot reported that, during cruise flight at 15,500 feet mean sea level in the pressurized airplane, he heard a loud “bang” as the windscreen fractured. The pilot diverted to a nearby airport, where he landed the airplane uneventfully. An examination of the windshield pieces revealed that the fracture origin area displayed features consistent with a preexisting crack that developed due to environmental stress cracking (ESC). ESC is a fracture mechanism in polymer materials that occurs when a susceptible polymer material is exposed to a combination of tensile stress and exposure to a substance that degrades the integrity of the material. The ESC was likely a result of contact with a degrading substance, the origin of which could not be determined. Although a stress analysis of the windscreen structure was not completed, the location of the fracture origin was likely an area of high stress on the windscreen due to the curvature at that location. Sustained high stress in acrylic can promote crack development, particularly when the acrylic is also exposed to certain chemical agents. The overall appearance of the windscreen edge showed limited visual evidence of adhesive on the surface, suggesting a relatively low bond strength between the windscreen at the frame. Evidence of voids in the epoxy at the interior bond surface were observed; if portions of the windscreen became disbonded, this could have affected the stress state of the windscreen and contributed to increased stress at the fracture origin area.

Quoted verbatim from the NTSB record.