Cozy MARK IV N20MN

Summary

On 25 March 2024 at about 23:53 local time, a Cozy MARK IV registered N20MN was involved in an accident near Gonzales, Texas, 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

25 March 2024 at 23:53

Classification

Accident

Location

Gonzales, Texas, United States

Nearest airport

Roger M. Dreyer Memorial Airpo (T20)

Coordinates

29.5327, -97.4664

Aircraft

Cozy MARK IV

Registration

N20MN

Category

Airplane

Year built

1999

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

San Antonio → Houston

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

CEN24LA141

Nobody was injured.

Maintenance personnel’s failure to properly torque the crankshaft idler gear hardware according to the engine manufacturer’s service instructions, which resulted in separation of the crankshaft idler gear’s fasteners and disengagement of the camshaft, crankshaft, and crankshaft idler gear and a subsequent total loss of engine power.

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

Read the full NTSB narrative

While enroute, at 9,500 ft above mean sea level (msl), the engine lost all power. After multiple attempts to restart the engine, the pilot executed a forced landing to a nearby airport. The airplane landed short of the runway threshold and its nose landing gear separated as the airplane transitioned onto the asphalt runway. The left wing and left canard sustained substantial damage. Postaccident examination of the engine revealed that the left crankshaft idler gear shaft separated from its attach points, which prevented the crankshaft idler gear from engaging its corresponding crankshaft and camshaft gears. The disengagement prevented camshaft rotation and valvetrain timing to the crankshaft. The left crankshaft idler gear’s attachment hardware were both separated into two sections from abrasion. The capscrew was lockwired to the idler shaft but no lockwire was observed through the stud and slotted shear nut. It is likely that maintenance personnel did not follow the engine manufacturer’s service instructions and undertorqued the fasteners during installation, resulting in insufficient clamping force. Additionally, the absence of lockwire likely permitted the shear nut to back off during engine operation. Because the airplane’s maintenance records were not available for review, the investigation was not able to identify when the crankshaft idler gear was last serviced.

Quoted verbatim from the NTSB record.