NTSB Identification: MIA93LA088.
The docket is stored on NTSB microfiche number 51212.
Accident occurred Sunday, March 21, 1993 in NAPLES, FL
Probable Cause Approval Date: 02/10/1994
Aircraft: Christen Industries PITTS S1-T, registration: N218MC
Injuries: 1 Minor.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

THE PILOT, WHO DOES NOT HOLD AN AIRFRAME OR POWERPLANT MECHANIC'S LICENSE STATED HE INSTALLED A STRAIGHT AIR INTAKE TUBE ON HIS AIRCRAFT. THIS TUBE DID NOT HAVE ANY MEANS FOR ALTERNATE AIR OR FILTERING OF INCOMING AIR. HE FURTHER MODIFIED THE TUBE BY INSTALLING A SCREEN AND A PIECE OF AIR FILTERING MATERIAL IN THE TUBE. DURING THE FIRST TAKEOFF AFTER THE MODIFICATION THE AIRCRAFT CLIMBED TO 200 FEET, AT WHICH TIME THE MANIFOLD PRESSURE DROPPED AND THE ENGINE LOST POWER. HE WAS UNABLE TO MAINTAIN ALTITUDE AND THE AIRCRAFT TOUCHED DOWN HARD ON THE RUNWAY AND NOSED OVER INVERTED. POSTCRASH EXAMINATION AND TESTING OF THE INTAKE TUBE WAS PERFORMED BY AN FAA INSPECTOR. WHEN A VACUUM CLEANER WAS ATTACHED TO THE ENGINE SIDE OF THE INTAKE TUBE AND TURNED ON THE AIR FLOW THROUGH THE TUBE WAS NORMAL FOR SEVERAL MINUTES. AFTER THIS, MOISTURE BUILT UP ON THE AIR FILTERING MATERIAL AND THE FILTER COLLAPSED. THE VACUUM CLEANER THEN BEGAN TO STRAIN DUE TO LACK OF AIR FLOW.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

THE INSTALLATION OF AN IMPROPER DESIGNED INTAKE TUBE AND AIR FILTER BY THE NONMECHANIC RATED PILOT-IN-COMMAND, WHICH RESULTED IN MOISTURE BUILD UP AND COLLAPSE OF THE AIR FILTER, WHICH RESULTED IN BLOCKAGE OF AIR FLOW TO THE ENGINE AND LOSS OF ENGINE POWER. CONTRIBUTING TO THE ACCIDENT WAS THE FAILURE OF THE PILOT-IN-COMMAND TO MAINTAIN AIRSPEED AND FLARE PROPERLY DURING A FORCED LANDING.

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