ASN Wikibase Occurrence # 358868
This information is added by users of ASN. Neither ASN nor the Flight Safety Foundation are responsible for the completeness or correctness of this information.
If you feel this information is incomplete or incorrect, you can submit corrected information.
| Date: | Monday 12 June 1995 |
| Time: | 05:15 LT |
| Type: |  Hughes 500D |
| Owner/operator: | Silver Bay Logging Inc. |
| Registration: | N549SW |
| MSN: | 800754D |
| Total airframe hrs: | 4278 hours |
| Engine model: | Allison250-C20B |
| Fatalities: | Fatalities: 0 / Occupants: 4 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Ketchikan, AK -
 United States of America
|
| Phase: | En route |
| Nature: | Unknown |
| Departure airport: | Fire Cove, AK |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
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.
Probable Cause: 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.
Accident investigation:
 |
|
Sources:
NTSB ANC95LA075
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 14-Mar-2024 19:07 | ASN Update Bot | Added |
Corrections or additions? ... Edit this accident description
The Aviation Safety Network is an exclusive service provided by:
Quick Links:
| ASN Home | Send Correction / Feedback |
| FSF Home | Disclaimer | Copyright |
| Contact Us | Privacy Policy |
| Press / Media |
CONNECT WITH US:
©2024 Flight Safety Foundation