What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
Lost power during a spray run. Collided with ground. (From .4) an Ayres S2R airplane lost power and crashed following a landing attempt to a field. The subsequent disassembly of the engine revealed that the compressor turbine disk was intact, but that all of the CT blades were fractured across the airfoils adjacent to the blade root platform. The canadian transportation safety board's engineering branch found that there were 55 blades of one part number and 3 blades of another part number which were not authorized for use in a PT6A-34AG engine. The three unapproved blades had a different heat code than was approved for this engine. One of the unapproved blades revealed a fatigue fracture on the surface as seen by the scanning electron microscope. The blades were manufactured by doncaster, under a FAA parts manufacturing approval as an alternate part for pwc CT blades. They were then packaged and shipped to superior air parts. Superior air parts would repackage the blades in superior air parts packaging prior to reshipping the blades. Doncaster's stated that superior was the sole distributor of the doncaster blades. Both the quality control standards at superior air parts and air force turbine services did not notice the three incorrect CT blades, which were shipped from superior air parts and subsequently, installed on the engine. Additionally, when the engine underwent repair work and these blades were installed, the new CT blades were installed and the radial tip clearance between the blades and segments was 0.0025 inches less than the minimum required by the PT6 engine manual. (-23) on part 137 flight compression turbine blade failed, power turbine was severly damaged. Aircraft lost power and landed in a field
As the FAA filed it
LOST POWER DURING A SPRAY RUN. COLLIDED WITH GROUND. (FROM .4) AN AYRES S2R AIRPLANE LOST POWER AND CRASHED FOLLOWING A LANDING ATTEMPT TO A FIELD. THE SUBSEQUENT DISASSEMBLY OF THE ENGINE REVEALED THAT THE COMPRESSOR TURBINE DISK WAS INTACT, BUT THAT ALL OF THE CT BLADES WERE FRACTURED ACROSS THE AIRFOILS ADJACENT TO THE BLADE ROOT PLATFORM. THE CANADIAN TRANSPORTATION SAFETY BOARD'S ENGINEERING BRANCH FOUND THAT THERE WERE 55 BLADES OF ONE PART NUMBER AND 3 BLADES OF ANOTHER PART NUMBER WHICH WERE NOT AUTHORIZED FOR USE IN A PT6A-34AG ENGINE. THE THREE UNAPPROVED BLADES HAD A DIFFERENT HEAT CODE THAN WAS APPROVED FOR THIS ENGINE. ONE OF THE UNAPPROVED BLADES REVEALED A FATIGUE FRACTURE ON THE SURFACE AS SEEN BY THE SCANNING ELECTRON MICROSCOPE. THE BLADES WERE MANUFACTURED BY DONCASTER, UNDER A FAA PARTS MANUFACTURING APPROVAL AS AN ALTERNATE PART FOR PWC CT BLADES. THEY WERE THEN PACKAGED AND SHIPPED TO SUPERIOR AIR PARTS. SUPERIOR AIR PARTS WOULD REPACKAGE THE BLADES IN SUPERIOR AIR PARTS PACKAGING PRIOR TO RESHIPPING THE BLADES. DONCASTER'S STATED THAT SUPERIOR WAS THE SOLE DISTRIBUTOR OF THE DONCASTER BLADES. BOTH THE QUALITY CONTROL STANDARDS AT SUPERIOR AIR PARTS AND AIR FORCE TURBINE SERVICES DID NOT NOTICE THE THREE INCORRECT CT BLADES, WHICH WERE SHIPPED FROM SUPERIOR AIR PARTS AND SUBSEQUENTLY, INSTALLED ON THE ENGINE. ADDITIONALLY, WHEN THE ENGINE UNDERWENT REPAIR WORK AND THESE BLADES WERE INSTALLED, THE NEW CT BLADES WERE INSTALLED AND THE RADIAL TIP CLEARANCE BETWEEN THE BLADES AND SEGMENTS WAS 0.0025 INCHES LESS THAN THE MINIMUM REQUIRED BY THE PT6 ENGINE MANUAL. (-23) ON PART 137 FLIGHT COMPRESSION TURBINE BLADE FAILED, POWER TURBINE WAS SEVERLY DAMAGED. AIRCRAFT LOST POWER AND LANDED IN A FIELD
NTSB investigation
The NTSB’s investigation of this event, with its probable cause and findings. Matched to this report by N-number and date.