An S269C-1 helicopter had a hard landing incurring damage. Flight instructor alleged caused by ground resonance. Technician reports overhaul of front gear dampers in accordance with manufacturer's manual.

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Attributes
ACN	634135
Time
Date	200409
Day	Fri
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 : instructional
Make Model Name	Helicopter
Operating Under FAR Part	other : 141
Flight Phase	landing : roll
Person 1
Affiliation	other
Function	maintenance : technician
Qualification	technician : powerplant technician : airframe
ASRS Report	634135
Person 2
Affiliation	other
Function	instruction : instructor
Qualification	pilot : cfi
Events
Anomaly	aircraft equipment problem : critical ground encounters other
Independent Detector	other other : 1
Resolutory Action	none taken : detected after the fact
Consequence	faa : reviewed incident with flight crew faa : investigated other other other
Supplementary
Problem Areas	Aircraft Chart Or Publication Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

On jan/xa/04, I overhauled front landing gear dampers, with the proper tool and in accordance with schweizer basic hmi [strut overhaul manual] for C-1 helicopters. On sep/fri/04, the CFI with student made a hard landing at ZZZ airport and reported that the aircraft started to vibrate and collapsed on its left side, CFI claimed it was ground resonance. On oct/mon/04 schweizer aircraft inspected front landing gear struts, claiming that the struts were over svced with the military 5606. On oct/mon/04, contacted by FSDO ZZZ1 about schweizer aircraft's company findings. On 2 other 300 helicopters we had overhauled, the landing gear struts have been disassembled (dampers) and checked for proper charge and correct fluid level. On the dampers (before) inspection no defects found. This incident is still under investigation. Callback conversation with reporter revealed the following information: the reporter said the front landing gear dampers were overhauled per the manufacturer's overhaul manual 9 months prior to the hard landing.

Original NASA ASRS Text

Title: AN S269C-1 HELI HAD A HARD LNDG INCURRING DAMAGE. FLT INSTRUCTOR ALLEGED CAUSED BY GND RESONANCE. TECHNICIAN RPTS OVERHAUL OF FRONT GEAR DAMPERS IN ACCORDANCE WITH MANUFACTURER'S MANUAL.

Narrative: ON JAN/XA/04, I OVERHAULED FRONT LNDG GEAR DAMPERS, WITH THE PROPER TOOL AND IN ACCORDANCE WITH SCHWEIZER BASIC HMI [STRUT OVERHAUL MANUAL] FOR C-1 HELIS. ON SEP/FRI/04, THE CFI WITH STUDENT MADE A HARD LNDG AT ZZZ ARPT AND RPTED THAT THE ACFT STARTED TO VIBRATE AND COLLAPSED ON ITS L SIDE, CFI CLAIMED IT WAS GND RESONANCE. ON OCT/MON/04 SCHWEIZER ACFT INSPECTED FRONT LNDG GEAR STRUTS, CLAIMING THAT THE STRUTS WERE OVER SVCED WITH THE MIL 5606. ON OCT/MON/04, CONTACTED BY FSDO ZZZ1 ABOUT SCHWEIZER ACFT'S COMPANY FINDINGS. ON 2 OTHER 300 HELIS WE HAD OVERHAULED, THE LNDG GEAR STRUTS HAVE BEEN DISASSEMBLED (DAMPERS) AND CHKED FOR PROPER CHARGE AND CORRECT FLUID LEVEL. ON THE DAMPERS (BEFORE) INSPECTION NO DEFECTS FOUND. THIS INCIDENT IS STILL UNDER INVESTIGATION. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR SAID THE FRONT LNDG GEAR DAMPERS WERE OVERHAULED PER THE MANUFACTURER'S OVERHAUL MANUAL 9 MONTHS PRIOR TO THE HARD LNDG.

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.