THE FATIGUE CRACKING AND FRACTURE OF THE PROPELLER HUB ARM. THE RESULTANT SEPARATION OF THE HUB ARM AND THE PROPELLER BLADE DAMAGED THE ENGINE, NACELLE, WING, AND FUSELAGE, THEREBY CAUSING SIGNIFICANT DEGRADATION TO AIRCRAFT PERFORMANCE AND CONTROL THAT MADE A SUCCESSFUL LANDING PROBLEMATIC. THE CAUSE OF THE PROPELLER HUB ARM FRACTURE WAS A REDUCTION IN THE FATIGUE STRENGTH OF THE MATERIAL BECAUSE OF MANUFACTURING AND TIME-RELATED FACTORS (DECARBURIZATION, RESIDUAL STRESS, CORROSION, MIXED MICROSTRUCTURE, AND MACHINING/SCORING MARKS) THAT REDUCED THE FATIGUE RESISTANCE OF THE MATERIAL, PROBABLY COMBINED WITH EXPOSURE TO HIGHER-THAN-NORMAL CYCLIC LOADS DURING OPERATION OF THE PROPELLER AT A CRITICAL VIBRATION FREQUENCY (REACTIONLESS MODE), WHICH WAS NOT APPROPRIATELY CONSIDERED DURING THE AIRPLANE/PROPELLER CERTIFICATION PROCESS.
N86SD
1973 BELL 47G-5A
Rotorcraft · Reciprocating · Standard
1 NTSB record
for this tail number, including destroyed damage, 8 fatal injuries. See the full record below.
Registration
Airframe
Powerplant
Live Flight Status
Checking live traffic…
Coverage depends on ground receiver reception and is not a complete picture of traffic.
Transponder & Tracking
The hex code is the aircraft's ICAO 24-bit address, broadcast by its ADS-B transponder. It is the key used to match live position reports to this registration.
Ownership History: 1 prior registration
| Registrant | Location | Cancelled |
|---|---|---|
| SOUTH DAKOTA STATE OF | PIERRE, SD | Jul 14, 1994 |
NTSB Accident & Incident Record
Apr 19, 1993
Accident
Destroyed ZWINGLE, IA
Injuries8 fatal
Phase of Flight-
ConditionsIMC
OperationFAR PUBU
Probable Cause
NTSB DCA93GA042