What aircraft was involved and where did it happen?

The accident on 1994-07-12 involved a North American NAVION 4, registration N8648H, at Dupont, LA.

Engine Power Loss and Stall During Forced Landing (N8648H)

On July 12, 1994, a North American NAVION 4 (registration N8648H) was involved in an aviation accident near Dupont, LA. Investigators recorded the probable cause as: THE LOSS OF ENGINE POWER DUE TO INADEQUATE MAINTENANCE ADJUSTMENT OF ACCESSORY DRIVE STARTER GEAR SCREWS WHICH DISENGAGED IN FLIGHT. FACTORS WERE THE LACK OF SUITABLE TERRAIN FOR THE FORCED LANDING AND NON COMPLIANCE WITH THE APPLICABLE SERVICE LETTER. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.

Sourcesthe U.S. National Transportation Safety Board (NTSB) historical archivePrimary reportUpdated 1781061362Data API Editorial standards

An airplane sustained substantial damage during a forced landing after a total loss of engine power. The pilot inadvertently stalled while maneuvering to avoid trees and wires. Loose hex screws were found in the engine, leading to gear misalignment and failure.

Introduction

An airplane was substantially damaged during a forced landing following a complete loss of engine power. While flaring to land, the pilot inadvertently stalled the aircraft in an effort to clear trees and wires.

Engine Examination

Post-accident examination of the engine revealed two loose hex screws. These screws, measuring 1/4 inch 20 by 15/16 inch, secure the starter gear pivot in place. One screw was found extended by 1 inch. The starter gear was misaligned, causing accessory gear teeth to grind. Metal shavings were observed on the starter gear and in the oil screen. Missing teeth on the aft crankshaft gear led to disengagement of the crankshaft from the aft camshaft gear, breaking engine continuity.

Maintenance History

The engine was assembled on July 14, 1992. Records did not indicate that a manufacturer service letter dated September 13, 1993, had been accomplished. That service letter contained instructions for tightening the hex screws and installing tab washers.

Conclusion

The total loss of engine power resulted from the disengagement of the crankshaft from the camshaft gear due to loose hex screws. During the forced landing, the pilot inadvertently stalled the airplane while attempting to clear obstacles.

Maintenance error

1994-07-12: North American NAVION 4 (N8648H) — Dupont, LA