A bell 407 during an autorotation RPM check the RPM did recover but the rotor decreased excessively with high blade angle. On touchdown 2 of the 4 rotors struck the tip of the left vertical winglet.

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Attributes
ACN	696195
Time
Date	200605
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	agl single value : 0
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : zzz.tower
Operator	general aviation : corporate
Make Model Name	Bell Helicopter Textron Undifferentiated or Other Model
Operating Under FAR Part	Part 91
Flight Phase	descent : approach landing other
Flight Plan	VFR
Person 1
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 71 flight time total : 4780 flight time type : 13
ASRS Report	696195
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	aircraft equipment other aircraft equipment : engine rpm indicator other flight crewa
Resolutory Action	none taken : detected after the fact
Consequence	other other
Supplementary
Problem Areas	Aircraft Chart Or Publication Flight Crew Human Performance Environmental Factor
Primary Problem	Flight Crew Human Performance

Narrative:

During autorotation RPM check; rotor RPM decrease to bottom of green range 95%. I continued descent to see if RPM would recover during deceleration. RPM did recover to normal range; and during termination to the ground without power applied; rotor decreased excessively low with very high blade angle applied. The bottom side of 2 of the 4 main rotor blades contacted the tip of the left side vertical winglet. No other damage to the aircraft occurred. No sudden stoppage inspection required. No injuries to the crew were incurred and no passenger were onboard. Callback conversation with reporter revealed the following information: the reporter stated the aircraft was in an autorotation RPM test and the descent was continued to check if the RPM would recover during deceleration. The RPM did recover to the normal range and at touchdown the rotor decreased excessively low with a high blade angle. The bottom surface of two rotor blades contacted the left vertical winglet. The blades when checked later were found to have spongy feel; blades were removed and sent to a shop for repair.

Original NASA ASRS Text

Title: A BELL 407 DURING AN AUTOROTATION RPM CHK THE RPM DID RECOVER BUT THE ROTOR DECREASED EXCESSIVELY WITH HIGH BLADE ANGLE. ON TOUCHDOWN 2 OF THE 4 ROTORS STRUCK THE TIP OF THE L VERT WINGLET.

Narrative: DURING AUTOROTATION RPM CHK; ROTOR RPM DECREASE TO BOTTOM OF GREEN RANGE 95%. I CONTINUED DSCNT TO SEE IF RPM WOULD RECOVER DURING DECELERATION. RPM DID RECOVER TO NORMAL RANGE; AND DURING TERMINATION TO THE GND WITHOUT PWR APPLIED; ROTOR DECREASED EXCESSIVELY LOW WITH VERY HIGH BLADE ANGLE APPLIED. THE BOTTOM SIDE OF 2 OF THE 4 MAIN ROTOR BLADES CONTACTED THE TIP OF THE L SIDE VERT WINGLET. NO OTHER DAMAGE TO THE ACFT OCCURRED. NO SUDDEN STOPPAGE INSPECTION REQUIRED. NO INJURIES TO THE CREW WERE INCURRED AND NO PAX WERE ONBOARD. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE ACFT WAS IN AN AUTOROTATION RPM TEST AND THE DSCNT WAS CONTINUED TO CHECK IF THE RPM WOULD RECOVER DURING DECELERATION. THE RPM DID RECOVER TO THE NORMAL RANGE AND AT TOUCHDOWN THE ROTOR DECREASED EXCESSIVELY LOW WITH A HIGH BLADE ANGLE. THE BOTTOM SURFACE OF TWO ROTOR BLADES CONTACTED THE LEFT VERTICAL WINGLET. THE BLADES WHEN CHECKED LATER WERE FOUND TO HAVE SPONGY FEEL; BLADES WERE REMOVED AND SENT TO A SHOP FOR REPAIR.

Data retrieved from NASA's ASRS site as of January 2009 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.