Stinson 108-3 N812C

Summary

On 16 December 2016 at about 15:45 local time, a Stinson 108-3 registered N812C was involved in an accident near Ionia, Michigan, 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

16 December 2016 at 15:45

Classification

Accident

Location

Ionia, Michigan, United States

Nearest airport

Ionia County Airport (Y70)

Coordinates

42.9381, -85.0606

Aircraft

Stinson 108-3

Registration

N812C

Category

Airplane

Year built

1947

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

Lowell → Ionia

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

CEN17LA057

Nobody was injured.

A failure of the aft support cable on the left main landing ski due to an inadequately formed nicopress sleeve, which allowed the ski to rotate into a vertical position shortly after liftoff, and its unavoidable separation during the subsequent landing.

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

Read the full NTSB narrative

The private pilot reported that, shortly after takeoff from a snow-covered runway, he heard a "thump" and saw that the left main landing ski tip had rotated up, past vertical, and was in contact with the left wing strut. He was unable to reposition the left ski into a normal position. Upon landing, the ski separated from the axle, the left gear leg dug into the snow, and the airplane rapidly decelerated before it nosed over. As designed, the main landing skis are supported by two 5/32-in braided steel cables and bungee/shock cords. Both ends of the steel cables terminate with a thimble-eye and a compressed/swaged nicopress sleeve. On the accident airplane, the forward and aft support cables had pulled through their respective nicopress sleeves where the cables attached to the left ski's tip and tail. The nicopress sleeves for the left ski tip and tail attachments were not located during the investigation. However, a postaccident examination of the remaining nicopress sleeves established that they were likely improperly formed with a 3/16-in swage tool instead of a properly-sized 5/32-in tool. As a result, the steel support cables were able to pull through the inadequately-formed nicopress sleeves during the accident flight. It is likely that the aft support cable pulled through its nicopress sleeve during takeoff, which allowed the ski to rotate into a vertical position. The forward support cable likely pulled through its nicopress sleeve when the left ski separated from the axle during the subsequent landing. The pilot reported that the airplane was typically equipped with snow skis during the winter. He purchased the main landing skis in used condition, with an undocumented service history, from an individual about 8 years before the accident. The forward and aft support cables were already fabricated and installed on the skis when they were purchased. Additionally, the pilot reported that the support cables had not been repaired or replaced since he owned the skis. The pilot, who was also an aviation mechanic, installed the main landing skis for the winter snow season 2 days before the accident. The accident occurred during the first flight since the skis were installed for the season.

Quoted verbatim from the NTSB record.