<< >> NASA ASRS Report 786309, May 2008

An experimental spencer amphibian aircar S-12-east rear main landing gear lock failed and main gear collapsed on landing.

Attributes
ACN	786309
Time
Date	200805
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
Operator	general aviation : personal
Make Model Name	Experimental
Operating Under FAR Part	Part 91
Flight Plan	None
Person 1
Affiliation	other
Function	oversight : pic
Qualification	pilot : private
Experience	flight time last 90 days : 29 flight time total : 273 flight time type : 74
ASRS Report	786309
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa
Resolutory Action	none taken : anomaly accepted
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

Aircraft's rear (main) landing gear lock failed and the main gear collapsed on landing. The aircraft skidded on its keel (it's a seaplane) 100-200 ft to a stop. Nose gear remained down and locked throughout event. I believe it was caused by a too weak spring on the overcenter locking mechanism which will be replaced by a stronger spring. Prior to the event; the flight had been completely normal. Callback conversation with reporter revealed the following information: reporter stated both left and right main landing gears on his spencer amphibian aircar are cessna L-19 birddog spring gear legs. They are mounted to a 6.50 inch diameter tube that runs left to right inside the fuselage. Both main gears rotate together when the gear is raised or lowered; using a hand crank chain system drive sprocket. When the overcenter locking pin did not engage; the 3400 pound weight of the spencer forced the main landing gears to rotate aft; as if retracting.

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Original NASA ASRS Text

Title: AN EXPERIMENTAL SPENCER AMPHIBIAN AIRCAR S-12-E REAR MAIN LANDING GEAR LOCK FAILED AND MAIN GEAR COLLAPSED ON LANDING.

Narrative: ACFT'S REAR (MAIN) LNDG GEAR LOCK FAILED AND THE MAIN GEAR COLLAPSED ON LNDG. THE ACFT SKIDDED ON ITS KEEL (IT'S A SEAPLANE) 100-200 FT TO A STOP. NOSE GEAR REMAINED DOWN AND LOCKED THROUGHOUT EVENT. I BELIEVE IT WAS CAUSED BY A TOO WEAK SPRING ON THE OVERCENTER LOCKING MECHANISM WHICH WILL BE REPLACED BY A STRONGER SPRING. PRIOR TO THE EVENT; THE FLT HAD BEEN COMPLETELY NORMAL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED BOTH LEFT AND RIGHT MAIN LANDING GEARS ON HIS SPENCER AMPHIBIAN AIRCAR ARE CESSNA L-19 BIRDDOG SPRING GEAR LEGS. THEY ARE MOUNTED TO A 6.50 INCH DIAMETER TUBE THAT RUNS LEFT TO RIGHT INSIDE THE FUSELAGE. BOTH MAIN GEARS ROTATE TOGETHER WHEN THE GEAR IS RAISED OR LOWERED; USING A HAND CRANK CHAIN SYSTEM DRIVE SPROCKET. WHEN THE OVERCENTER LOCKING PIN DID NOT ENGAGE; THE 3400 LB WEIGHT OF THE SPENCER FORCED THE MAIN LANDING GEARS TO ROTATE AFT; AS IF RETRACTING.

Data retrieved from NASA's ASRS site as of May 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.