19970718018999A

Accident · Substantial damage

FAA accident report · Skrsky S-58T · Page, AZ · July 18, 1997

Date: July 18, 1997 · 14:15 local
Place: Page, AZ
Phase of flight: Power On Descent (Rotorcraft)
Operating rules: Rotorcraft external load (Part 133)
Operator: ONRL
Damage: Substantial damage
Aircraft: N47B
NTSB investigation: NTSBLAX97LA247
Reported as: Skrsky S58T
Reported engine: Pratt & Whitney PT6T3
People aboard: 1
Fatal injuries: 0
Pilot’s flight hours: 9,996 total4,750 in this make and model85 in the last 90 days

N47BRegistered now · Sikorsky S-58TS/N 58-530 Airframe modelSikorsky S-58T Engine modelPratt & Whitney Canada PT6A-60ATurbo-prop

From the FAA’s Accident/Incident Data System (AIDS), through its Aviation Safety Information Portal, as reported. The NTSB investigates accidents separately, and its record of an accident is the fuller one. The aircraft is matched to the registry by N-number and event date, checked against the reported make and model; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.

What happened

The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.

Helicopter over concrete pour site on external load, engine blew up, aircraft flew away from area and landed hard. (.4)the pilot was hovering with an external load, when he heard a loud noise and noticed a power loss. He turned and executed a precautionary landing with a hard touchdown. The main rotor blades flexed downward and impacted the tail boom. An inspection revealed that over half of the blades in the no. 2 power section were fractured. A metallurgical examination revealed that two consecutive blades showed evidence of solutioning and re-solidification; however, the fracture surfaces did not show similar evidence of heat distress. Discoloration was also found on the power turbine wheel at a point corresponding to the location of the two blades. The operator stated that the aircraft had flown about 138 hours since all the turbine blades were replaced. None of the pilots who had flown the aircraft since then reported experiencing any hung or hot starts.

As the FAA filed it

HELICOPTER OVER CONCRETE POUR SITE ON EXTERNAL LOAD, ENGINE BLEW UP, AIRCRAFT FLEW AWAY FROM AREA AND LANDED HARD. (.4)THE PILOT WAS HOVERING WITH AN EXTERNAL LOAD, WHEN HE HEARD A LOUD NOISE AND NOTICED A POWER LOSS. HE TURNED AND EXECUTED A PRECAUTIONARY LANDING WITH A HARD TOUCHDOWN. THE MAIN ROTOR BLADES FLEXED DOWNWARD AND IMPACTED THE TAIL BOOM. AN INSPECTION REVEALED THAT OVER HALF OF THE BLADES IN THE NO. 2 POWER SECTION WERE FRACTURED. A METALLURGICAL EXAMINATION REVEALED THAT TWO CONSECUTIVE BLADES SHOWED EVIDENCE OF SOLUTIONING AND RE-SOLIDIFICATION; HOWEVER, THE FRACTURE SURFACES DID NOT SHOW SIMILAR EVIDENCE OF HEAT DISTRESS. DISCOLORATION WAS ALSO FOUND ON THE POWER TURBINE WHEEL AT A POINT CORRESPONDING TO THE LOCATION OF THE TWO BLADES. THE OPERATOR STATED THAT THE AIRCRAFT HAD FLOWN ABOUT 138 HOURS SINCE ALL THE TURBINE BLADES WERE REPLACED. NONE OF THE PILOTS WHO HAD FLOWN THE AIRCRAFT SINCE THEN REPORTED EXPERIENCING ANY HUNG OR HOT STARTS.

NTSB investigation

The NTSB’s investigation of this event, with its probable cause and findings. Matched to this report by N-number and date.

NTSB LAX97LA247Accident · No injuriesLimited investigationFinal reportPage, AZan engine failure resulting from the fracture of two power turbine blades, which had been previously subjected to a hot or hung start.Jul 18, 1997 · Substantial damage