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Casualties unknown

Hard Landing During Autorotation Following Engine Failure from Turbine Wheel Burst (N515EH)

Tomball, TX, US

On October 7, 1985, a Bell 206L-1 (registration N515EH) operated by Dhl Airways, Inc. was involved in an aviation accident near Tomball, TX. Investigators recorded the probable cause as: Fatigue failure of the turbine-to-compressor coupling, which allowed the shaft to decouple, resulting in the No. 1 turbine wheel bursting and an uncontained failure causing complete power loss. 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 2026-07-04Data APIEditorial standards

An aircraft was substantially damaged during a hard landing in an emergency autorotation after a complete power loss caused by an uncontained failure of the No. 1 turbine wheel, which burst due to a fatigue fracture in the turbine-to-compressor coupling shaft.

Overview

An aircraft experienced a complete power loss during departure, leading to an emergency autorotation and a hard landing that resulted in substantial damage to the aircraft. The power loss occurred at low altitude, and the pilot was required to maneuver the aircraft to the only available forced landing area.

Engine Failure

The power loss was caused by an uncontained failure of the No. 1 turbine wheel. The wheel burst after a fatigue failure of the turbine-to-compressor coupling, which allowed the shaft to decouple. When the turbine section decoupled, the engine experienced an overspeed. Metallurgical examination traced the origin of the fatigue fracture to the scallop area on the turbine end of the shaft.

Emergency Landing

Following the engine failure at low altitude, the pilot maneuvered the aircraft to the only suitable forced landing area. The subsequent autorotation landing was hard, causing substantial damage to the aircraft.

Probable cause

Fatigue failure of the turbine-to-compressor coupling, which allowed the shaft to decouple, resulting in the No. 1 turbine wheel bursting and an uncontained failure causing complete power loss.
Engine failureStructural failure

Frequently asked questions

What happened in the 7 Oct 1985 Bell 206L-1 accident near Tomball, TX?

An aircraft was substantially damaged during a hard landing in an emergency autorotation after a complete power loss caused by an uncontained failure of the No. 1 turbine wheel, which burst due to a fatigue fracture in the turbine-to-compressor coupling shaft.

What aircraft was involved and where did it happen?

The accident on 7 Oct 1985 involved a Bell 206L-1, registration N515EH, operated by Dhl Airways, Inc., at Tomball, TX.

What was the probable cause of the accident?

Fatigue failure of the turbine-to-compressor coupling, which allowed the shaft to decouple, resulting in the No. 1 turbine wheel bursting and an uncontained failure causing complete power loss.

More accident analyses

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001214X38012. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.