Partial nose gear downlock failure on small aircraft due unapproved and unrecorded modification.

Attributes
ACN	163515
Time
Date	199011
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : sez
State Reference	AZ
Altitude	agl bound lower : 0 agl bound upper : 0
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	general aviation : personal
Make Model Name	Small Aircraft, Low Wing, 1 Eng, Retractable Gear
Flight Phase	landing other
Flight Plan	VFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : private
Experience	flight time total : 280
ASRS Report	163515
Person 2
Affiliation	Other
Function	other personnel other personnel other
Qualification	other other : other
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	other other : unspecified
Resolutory Action	flight crew : overcame equipment problem
Consequence	other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

I had 3 green lights when I lowered the gear on my crosswind leg, and still had 3 green on downwind and final. After T/D, I felt the nose drop lower than normal and pulled back on the yoke, expecting that the nose gear had failed. The 'gear unsafe' light and horn came on, and the propeller momentarily struck the runway. I continued to hold the yoke back during the rollout, and observed that the nose gear was not supporting the weight of the nose. I stopped the engine as soon as I cleared the active and coasted to the ramp. Inspection confirmed the propeller strike, and a broken downlock. Later inspection by a mechanic, revealed a flange which had been permanently inserted in the gear support possibly preventing it from extending 'past center' into a fully locked position. Origin of this modification is not known.

Original NASA ASRS Text

Title: PARTIAL NOSE GEAR DOWNLOCK FAILURE ON SMA DUE UNAPPROVED AND UNRECORDED MODIFICATION.

Narrative: I HAD 3 GREEN LIGHTS WHEN I LOWERED THE GEAR ON MY XWIND LEG, AND STILL HAD 3 GREEN ON DOWNWIND AND FINAL. AFTER T/D, I FELT THE NOSE DROP LOWER THAN NORMAL AND PULLED BACK ON THE YOKE, EXPECTING THAT THE NOSE GEAR HAD FAILED. THE 'GEAR UNSAFE' LIGHT AND HORN CAME ON, AND THE PROP MOMENTARILY STRUCK THE RWY. I CONTINUED TO HOLD THE YOKE BACK DURING THE ROLLOUT, AND OBSERVED THAT THE NOSE GEAR WAS NOT SUPPORTING THE WEIGHT OF THE NOSE. I STOPPED THE ENG AS SOON AS I CLRED THE ACTIVE AND COASTED TO THE RAMP. INSPECTION CONFIRMED THE PROP STRIKE, AND A BROKEN DOWNLOCK. LATER INSPECTION BY A MECH, REVEALED A FLANGE WHICH HAD BEEN PERMANENTLY INSERTED IN THE GEAR SUPPORT POSSIBLY PREVENTING IT FROM EXTENDING 'PAST CTR' INTO A FULLY LOCKED POS. ORIGIN OF THIS MODIFICATION IS NOT KNOWN.

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.