Cessna T210N N4791C

Summary

On 24 January 2006 at about 17:51 local time, a Cessna T210N registered N4791C, operated by Ross Rankin, was involved in an accident near Mariposa, California, United States. 2 people were on board and one had minor injuries. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

24 January 2006 at 17:51

Classification

Accident

Location

Mariposa, California, United States

Nearest airport

Mariposa-Yosemite (MPI)

Coordinates

37.3289, -120.0578

Aircraft

Cessna T210N

Registration

N4791C

Category

Airplane

Engines

1

Operator

Ross Rankin

Operating rule

Part 91: General Aviation

Purpose of flight

Business

Phase of flight

Not recorded

Route

Visalia → Mariposa

Aircraft damage

Substantial

Weather

IMC

Light

Day

NTSB number

LAX06LA094

1 person had minor injuries.

The failure of the maintenance personnel to follow the procedures in the TCM maintenance manual and adequately torque the engine through-bolts, which led to the separation of the No. 6 cylinder and the catastrophic failure of the engine.

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

Read the full NTSB narrative

The aircraft collided with multiple obstacles during a forced landing in rough terrain following a catastrophic engine failure. While en route about 6,000 feet mean sea level, one cylinder in the engine indicated a loss of exhaust gas and cylinder head temperature. Thereafter, an increasingly strong vibration was felt, oil dispersed onto the front windscreen, and all engine power was lost. During the landing flare, the airplane impacted an oak tree, a fence, and a rock outcrop. The engine was found separated from the airplane's firewall. Also, the number 6 cylinder was observed broken from the engine case. The engine was torn down and the case was opened. The evidence of the torque values found on all the engine through-bolts, combined with the fretting signature at the base of the number 6 cylinder, and the oil residue at the union of the case halves, indicates that when the cylinders were installed on the engine their respective bolts were inadequately torqued. During an interview with the mechanic who had replaced the 6 cylinders on the engine, he reported that he followed the instructions in TCM's maintenance manual when he had replaced the cylinders in May 2005. He said he torqued the nuts on the cylinders to about 500 inch pounds. According to TCM's maintenance manual, 1989 edition, the required torque for the through-bolts was 690 to 710 inch pounds. By 1996, TCM had revised its manual by issuance of service bulletin 96-7. In that bulletin the required torque was increased to between 790 to 810 inch pounds.

Quoted verbatim from the NTSB record.