AD NUMBER: PL2003-08-51
MANUFACTURER: MDHC
SUBJECT: Airworthiness Directive PL2003-08-51
SUMMARY: This Emergency Airworthiness Directive (EAD) covering certain Model 369 and 500 helicopters is prompted by two reports of cracked tail rotor blade pitch horns (pitch horns) that failed during flight. In both occurrences, the pilot was able to land the helicopter without further incident. Investigation revealed that the cause of the failures was a fatigue crack in the pitch horns that developed before the tail rotor blade reached its retirement life. This condition, if not corrected, could result in a pitch horn separating from the tail rotor blade leading to an unbalanced condition, vibration, loss of tail rotor pitch control, and loss of directional control of the helicopter. This unsafe condition is likely to exist or develop on other helicopters of the same type designs. Therefore, this EAD requires, before further flight, reducing the retirement life of certain tail rotor blades from 5,140, 5,200, or 10,000 hours time-in-service (TIS) to 400 hours TIS, performing a onetime visual inspection of each pitch horn for a crack or corrosion, and replacing unairworthy tail rotor blades with airworthy tail rotor blades. This EADalso requires revising the Airworthiness Limitations section of the helicopter maintenance manual to reflect the reduced retirement life, and reporting information to the FAA within 24 hours following the one-time inspection.

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