Hughes 500D N549SW

Summary

On 12 June 1995 at about 13:15 local time, a Hughes 500D registered N549SW was involved in an accident near Ketchikan, Alaska, United States. 4 people were on board and 4 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

12 June 1995 at 13:15

Classification

Accident

Location

Ketchikan, Alaska, United States

Coordinates

55.6096, -131.5803

Aircraft

Hughes 500D

Registration

N549SW

Category

Helicopter

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Other Work Use

Phase of flight

Not recorded

Route

Fire Cove → Unknown

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

ANC95LA075

4 people had minor injuries.

AN AIR LEAK AT A 'B' NUT FITTING ON A PNEUMATIC PC TUBE TO THE POWER TURBINE GOVERNOR. COMPANY MAINTENANCE PERSONNEL DID NOT DETECT A LEAK AFTER PERFORMING MAINTENANCE ON THE GOVERNER AND P2 AIR LINE.

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

Read the full NTSB narrative

THE HELICOPTER PILOT WAS IN CRUISE FLIGHT ABOUT 250 FEET ABOVE THE GROUND, TRANSPORTING LOGGING PERSONNEL TO A REMOTE AREA. THE ENGINE SUDDENLY LOST POWER, AND THE PILOT BEGAN AN AUTOROTATION TO A GRAVEL PIT. DURING TOUCHDOWN, THE TAILBOOM WAS SEVERED, AND THE HELICOPTER ROLLED ONTO ITS RIGHT SIDE. DURING RECOVERY OF THE HELICOPTER, THE LIFTING CABLE BROKE, AND THE HELICOPTER DESCENDED TO THE GROUND FROM ABOUT 400 FEET. POSTACCIDENT EXAMINATION OF THE ENGINE FUEL CONTROL AND POWER TURBINE GOVERNOR DID NOT REVEAL ANY MALFUNCTION. EXAMINATION OF THE PNEUMATIC PC TUBE (AIR LINE) FROM THE PC FILTER TO THE GOVERNOR REVEALED AN AIR LEAK AT THE 'B' NUT ATTACHMENT TO THE GOVERNOR 'T' FITTING. LABORATORY TESTING REVEALED THAT A TORQUE OF 300 INCH POUNDS WOULD HAVE BEEN REQUIRED TO STOP THE AIR LEAK. THE MANUFACTURER'S SPECIFIED TORQUE VALUE WAS 100 INCH POUNDS. RECORDS SHOWED THAT ON 6/7/95, MAINTENANCE HAD BEEN PERFORMED TO REPLACE THE GOVERNOR AND TO CLEAN AND REINSTALL THE P2 AIR LINE; AND ON 6/11/95 (DAY BEFORE THE ACCIDENT), THE ENGINE SPEED HAD BEEN ADJUSTED. THE MAINTENANCE MANUAL FOR THE ENGINE WARNED THAT AIR LEAKS IN THE PNEUMATIC SENSING SYSTEM COULD RESULT IN FLAME-OUT, POWER LOSS, OR OVERSPEED.

Quoted verbatim from the NTSB record.