Power train cowling on an AS355 twin-STAR helicopter aircraft came loose in flight striking the main...

Attributes
ACN	270597
Time
Date	199405
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : ptn
State Reference	LA
Altitude	msl bound lower : 500 msl bound upper : 500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : eyw
Operator	common carrier : air taxi
Make Model Name	SA 360 Dauphin
Operating Under FAR Part	Part 91
Flight Phase	descent : approach
Flight Plan	None
Person 1
Affiliation	company : air taxi
Function	flight crew : single pilot
Qualification	pilot : atp
Experience	flight time last 90 days : 50 flight time total : 7000 flight time type : 4000
ASRS Report	270597
Person 2
Affiliation	company : air taxi
Function	other personnel other
Qualification	other other : other
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	other flight crewa
Resolutory Action	none taken : detected after the fact other
Consequence	other Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

During a maintenance flight to track and balance the main rotor system on an AS355 F-1 helicopter, the right transmission cowling opened in flight and was struck by the main rotor system. Maintenance personnel had removed the cowling earlier and reinstalled before the flight. I, as the pilot, looked the aircraft over and did not notice the specific cowling hatches being open. The aircraft had been cranked and ground run at least 3 times before a flight was made. After these run-ups and adjustments by maintenance personnel, aircraft was said to be ready for flight to check track and balance in flight. On first flight, aircraft was picked up to a hover, takeoff made, the aircraft transitioned to level flight at 500 ft MSL. On approach to the heliport at patterson, la, there was an initial shudder. At about 100 ft AGL there was another shudder. Aircraft was landed without further incident. On exiting aircraft, found cowling had come off and gone through main rotor system. This has happened before on this type aircraft. I feel another safety system of some type such as a cable attachment to preclude the cowling from being able to open to the extent of hitting rotor system should be implemented.

Original NASA ASRS Text

Title: PWR TRAIN COWLING ON AN AS355 TWIN-STAR HELI ACFT CAME LOOSE IN FLT STRIKING THE MAIN ROTOR BLADE BEFORE FALLING OFF THE ACFT. THE HELI WAS LANDED WITHOUT FURTHER INCIDENT.

Narrative: DURING A MAINT FLT TO TRACK AND BAL THE MAIN ROTOR SYS ON AN AS355 F-1 HELI, THE R XMISSION COWLING OPENED IN FLT AND WAS STRUCK BY THE MAIN ROTOR SYS. MAINT PERSONNEL HAD REMOVED THE COWLING EARLIER AND REINSTALLED BEFORE THE FLT. I, AS THE PLT, LOOKED THE ACFT OVER AND DID NOT NOTICE THE SPECIFIC COWLING HATCHES BEING OPEN. THE ACFT HAD BEEN CRANKED AND GND RUN AT LEAST 3 TIMES BEFORE A FLT WAS MADE. AFTER THESE RUN-UPS AND ADJUSTMENTS BY MAINT PERSONNEL, ACFT WAS SAID TO BE READY FOR FLT TO CHK TRACK AND BAL IN FLT. ON FIRST FLT, ACFT WAS PICKED UP TO A HOVER, TKOF MADE, THE ACFT TRANSITIONED TO LEVEL FLT AT 500 FT MSL. ON APCH TO THE HELIPORT AT PATTERSON, LA, THERE WAS AN INITIAL SHUDDER. AT ABOUT 100 FT AGL THERE WAS ANOTHER SHUDDER. ACFT WAS LANDED WITHOUT FURTHER INCIDENT. ON EXITING ACFT, FOUND COWLING HAD COME OFF AND GONE THROUGH MAIN ROTOR SYS. THIS HAS HAPPENED BEFORE ON THIS TYPE ACFT. I FEEL ANOTHER SAFETY SYS OF SOME TYPE SUCH AS A CABLE ATTACHMENT TO PRECLUDE THE COWLING FROM BEING ABLE TO OPEN TO THE EXTENT OF HITTING ROTOR SYS SHOULD BE IMPLEMENTED.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Power train cowling on an AS355 twin-STAR helicopter aircraft came loose in flight striking the main rotor blade before falling off the aircraft. The helicopter was landed without further incident.