De Havilland TIGER MOTH DH 82A N523R

Summary

On 24 June 2012 at about 02:55 local time, a De Havilland TIGER MOTH DH 82A registered N523R was involved in an accident near Fontana, California, 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

24 June 2012 at 02:55

Classification

Accident

Location

Fontana, California, United States

Nearest airport

Flabob (RIR)

Coordinates

34.0492, -117.4653

Aircraft

De Havilland TIGER MOTH DH 82A

Registration

N523R

Category

Airplane

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

Flabob → Upland

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

WPR12LA275

Nobody was injured.

Partial loss of engine power during cruise flight due to a failed engine cylinder rocker assembly clamping bolt. Contributing to the accident was the failure of unknown maintenance personnel to perform a modification to the assembly that would have prevented the failure.

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

Read the full NTSB narrative

During cruise flight, the engine lost partial power. The pilot performed a forced landing into a field, and the airplane nosed over. Postaccident examination of the engine revealed that a rocker bracket assembly clamping bolt had failed in fatigue, causing the assembly to partially detach from the cylinder head. The detachment prevented the exhaust valve from actuating. Peening damage sustained to the bolt revealed that it most likely failed during a prior flight, at an undetermined time before the ultimate displacement of the bracket assembly. No airworthiness directives existed for the antique engine, which was overhauled 46 years prior to the accident. However, a “modification news sheet” was issued by the manufacturer 16 years before the overhaul, which detailed a design change intended to preclude the failure of the clamping bolts. The modification was not performed on the failed cylinder; however, the three other cylinders exhibited an undocumented modification to their rocker valve assemblies, which appeared to perform the same function.

Quoted verbatim from the NTSB record.