On April 8, 2000, a Hughes 369D (registration N5070J) was involved in an aviation accident near Lemont, IL. Investigators recorded the probable cause as: the loss of engine power for undetermined reasons. A factor was the operation within the cross "hatched area" of the helicopter's height/velocity curve by the company. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter conducting power line maintenance impacted muddy terrain following an autorotation from a hover at 100 feet AGL. The operation was within the cross-hatched area of the height-velocity diagram.
Incident Overview
A helicopter engaged in power line maintenance operations impacted muddy terrain after performing an autorotation. The autorotation was executed from a hover at an altitude of 100 feet above ground level. The helicopter struck the ground during the maneuver.
Height-Velocity Diagram Analysis
Review of the helicopter's height-velocity diagram showed that the operation was conducted within the "cross hatched" area. Operation within this region may not allow sufficient time for the critical transition from powered flight to autorotation, potentially leading to insufficient altitude for a safe touchdown.
Mechanical Examination
Examination of the airframe, engine, and related components revealed no anomalies. No mechanical or system defects were found.
Frequently asked questions
What happened in the 8 Apr 2000 Hughes 369D accident near Lemont, IL?
A helicopter conducting power line maintenance impacted muddy terrain following an autorotation from a hover at 100 feet AGL. The operation was within the cross-hatched area of the height-velocity diagram.
What aircraft was involved and where did it happen?
The accident on 8 Apr 2000 involved a Hughes 369D, registration N5070J, at Lemont, IL.
What was the probable cause of the accident?
the loss of engine power for undetermined reasons. A factor was the operation within the cross "hatched area" of the helicopter's height/velocity curve by the company.
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