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ASN Wikibase Occurrence # 14208
Last updated: 17 November 2018
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Date:22-MAY-1968
Time:17:51
Type:Silhouette image of generic S61 model; specific model in this crash may look slightly different
Sikorsky S-61L
Owner/operator:Los Angeles Airways
Registration: N303Y
C/n / msn: 61060
Fatalities:Fatalities: 23 / Occupants: 23
Other fatalities:0
Aircraft damage: Written off (damaged beyond repair)
Location:Paramount, CA -   United States of America
Phase: En route
Nature:Domestic Scheduled Passenger
Departure airport:Anaheim/Disneyland Heliport, CA
Destination airport:Los Angeles Intl Apt, CA (LAX)
Narrative:
Los Angeles Airways Flight 841, a Sikorsky S-61LY N303Y, crashed and burned at Paramount, California.
The accident sequence probably began while the aircraft was in cruising flight about 2,000 feet above the ground and about 2 miles east of the accident site. The black, yellow, and blue main rotor blades, followed by the red and white blades, underwent a series of extreme overtravel excursions in their lead/lag axis.
During the extreme excursions, the yellow main rotor blade overtraveled in the lead direction and, as a result, its pitch change control road was subjected to downward and rearward loading many times its design operating strength. Under these forces, the rod became detached at its lower trunnion end where it is normally secured to the attachment lugs of the main rotor rotating swashplate. With this separation, the blade went out of control and struck the right side of the aircraft diagonally across the baggage loading door. The other four main rotor blades then struck and penetrated both the aft and forward portions of the aircraft. The blade strikes destroyed the main rotor blades and separated major portions of the fuselage, including the tailrotor pylon and tail rotor assemblies. The aircraft, completely uncontrollable, crashed in a near-vertical descent.
The initial malfunction, failure , or condition which precipitated the accident sequence was probably a loss of main rotor blade damper integrity caused by either failure of the black main rotor blade damper or a loss of effective damper action by the white main rotor blade damper. An important portion of the black damper and a portion of the black blade horizontal hinge pin to which the damper attaches were not recovered.
The Safety Board determines that the probable cause of this accident was the loss of main rotor blade damper integrity due to either a failure of the black blade damper or a loss of effective damping action by the white blade damper. This resulted in uncontrolled excursions of the main rotor blades in their leadllag axis, an overload detachment of the yellow main rotor blade pitch change control rod and destruction of the structural integrity of the aircraft by blade strikes. The precise reason for either of the possibilities for the loss of damper integrity is undetermined.

Sources:

NTSB
https://www.ntsb.gov/aviationquery/brief.aspx?ev_id=13185&key=0
http://www.airdisaster.com/reports/ntsb/AAR70-01.pdf
http://mid.gov.kz/images/stories/contents/107_en.pdf


Helicopter named "Megapolis IV"


Revision history:

Date/timeContributorUpdates
25-Feb-2008 12:00 ASN archive Added
07-Apr-2009 01:18 harro Updated
28-Dec-2009 10:19 TB Updated [Source, Narrative]
09-Aug-2014 17:21 Aerossurance Updated [Source, Narrative]
13-Apr-2018 14:01 Aerossurance Updated [Source]

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