NTSB Identification: FTW94FA176.
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Accident occurred Tuesday, May 24, 1994 in PHOENIX, AZ
Probable Cause Approval Date: 01/12/1995
Aircraft: PRAKER THORP T18C, registration: N86BP
Injuries: 1 Fatal.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

AFTER THE FIRST TEST FLIGHT FOR THE HOME BUILT AIRPLANE, THE TEST PILOT TOLD THE OWNER/BUILDER THAT HE HAD TO HOLD 35 POUNDS OF FORWARD STICK PRESSURE TO MAINTAIN LEVEL FLIGHT IN CRUISE. THE BUILDER AND TEST PILOT REMOVED THE STABILATOR ANTI-SERVO TAB CONTROL ARMS AND BENT THEM IN A VICE WITH A MALLET. THE ARMS WERE SUBSEQUENTLY REINSTALLED AND THE AIRPLANE TOOK OFF ON A SECOND TEST FLIGHT. VIDEO TAPE SHOWED THE SECOND TAKEOFF INITIAL CLIMB TO BE STEEPER THAN THE FIRST. SHORTLY AFTER TAKEOFF, THE TOWER ASKED THE PILOT WHY HE WAS TURNING RIGHT INSTEAD OF THE REQUIRED LEFT TURN. HE STATED 'I GOT PROBLEMS HERE.' THE AIRPLANE CONTINUED TO CLIMB AND WAS SEEN TO ENTER A RIGHT SPIN FROM A NOSE HIGH, STEEP RIGHT BANK ATTITUDE. THE TEST PILOT HAD SEVERAL YEARS TEST EXPERIENCE AND 1,000 HOURS IN THE ACCIDENT MAKE AND MODEL. THE REASON FOR THE STABILATOR CONTROL MALFUNCTION WAS NOT DETERMINED. HOWEVER, A MAINTENANCE INSTRUCTION ADJUSTMENT RIGGING CHECK WAS NOT PERFORMED AFTER THE REINSTALLATION OF THE ARMS.

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

THE PILOT'S INABILITY TO PREVENT AN INADVERTENT STALL AND HIS INABILITY TO RECOVER DUE TO A RESTRICTION IN THE MOVEMENT OF THE STABILATOR FOR UNDETERMINED REASONS. A FACTOR WAS THE FAILURE OF THE OWNER/BUILDER AND THE PILOT TO ACCOMPLISH A CONTROL RIGGING CHECK PRIOR TO THE FLIGHT.

Full narrative available

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