What was found
(CAN) A/C PERFORMING NORMAL APPROACH. DURING FINAL, A LIGHT WHINING SOUND HEARD AS POWER APPLIED. AS POWER INCREASED, SOUND INCREASED. AT APPROX 8 FT FROM TOUCHDOWN, ENG STOPPED, & CHIP CAUTION LIGHT ILLUMINATED. CONTROL MAINTAINED HELICOPTER LANDED WITHOUT INCIDENT. INVESTIGATION REVEALED ENG OIL LOW. MAG CHIP DETECTOR REMOVED & FOUND SILVER METAL PARTICLES. OIL FROM GEARBOX COLLECTED & FOUND TO CONTAINED SILVER & BLACK METAL PARTICLES UP TO 1/16 IN DIAMETER. ENGINE REMOVED FROM SERVICE & RENTAL ENGINE INSTALLED. A/C RETURNED TO SERVICE. FAILED ENG SENT IN FOR EVAL & REPAIR. PRELIMINARY INVEST REVEALED ACCESSORY DRIVEN GEAR FAILED & BROKE IN TWO. PRIMARY REASON FOR GEAR FAILURE UNDER INVESTIGATION BY NTSB.