Robinson R44 main rotor blade fatigue cracks - Civil Aviation Safety Alerts (CASA) No. 2015-01


Owners, operators, and maintainers of Robinson Helicopter model R44, R44 II and R66 helicopters

Issuing Office: National Aircraft Certification
File Classification No.: Z 5000-35
RDIMS No.: 12276220
Document No.: CASA 2015-01
Issue No.: 02
Effective Date: 2017-04-21


The purpose of this Civil Aviation Safety Alert (CASA) is to alert owners and operators of Robinson Helicopter R44, R44 II and R66 helicopters of possible fatigue cracks on part numbers (P/Ns) C016-7 and F-016-2 main rotor blades and to recommend inspection and modification of the blades. This CASA also reminds operators that non-approved aircraft modifications and overweight operation can increase the risk of in-service failures.


Transport Canada Civil Aviation (TCCA) has been made aware of a report from a New Zealand R44 helicopter operator that conducted an emergency landing after encountering a severe vibration of the main rotor blades.

Further investigation determined that the main rotor blade had failed in flight due to metal fatigue. The accident helicopter was equipped with an unapproved spray system. If the helicopter had been operated with a full spray tank it would have exceeded maximum gross weight. It was also determined that the usage of the helicopter was relatively severe: ground-air-ground and/or rotor start/stop cycles per flight hour were above average with a large proportion of cycles flown at high gross weights.

Recommended Action:

Robinson Helicopter released R44 Safety Alert “C016-7 Main Rotor Blade Crack” in February 2015, recommending pre-flight visual inspection for possible damage and/or fatigue cracks of those rotor blades. Since that time, Robinson Helicopter superseded that Alert with Service Bulletins R44 SB-89 and R66 SB-13. These bulletins provide instructions to clean, inspect and modify rotor blades P/N C016-7 and F 016‑2. Modification of the rotor blade in accordance with the requirements of the Service Bulletins removes an abrupt shape change that currently exists at the blades’ trailing edge, reducing stress concentration that is believed to be associated with the New Zealand R44 blade failure.

TCCA strongly recommends that owners and operators comply with the applicable Service Bulletins on their aircraft and spares. Owners and operators should note that modification of a rotor blade is defined as a “Major Modification” by Canadian Aviation Regulations Standard 571 Appendix A. The Robinson Service Bulletins are considered to be “Specified Data” by Transport Canada. Specified data is information contained in authoritative documents which, although not approved by the Minister of Transport, has been specified by the Minister as appropriate for the purpose of major modifications and major repairs, in conformity with section 571.06 of the Canadian Aviation Regulations.

TCCA reminds operators that it is contrary to Canadian Aviation Regulations to operate an aircraft with unapproved modifications or outside of approved limitations. If in doubt, operators are encouraged to communicate with the manufacturer to determine if additional inspections, maintenance schedules adjustments or any other measure is required to account for the operating environment.

Defects, malfunctions and failures occurring on aeronautical products are to be reported to Transport Canada, Continuing Airworthiness in accordance with CAR 521 division IX, mandatory Service Difficulty Reporting requirements.

Contact Office:

For more information concerning this issue, contact a Transport Canada Centre; or Jean Grenier, Continuing Airworthiness, Ottawa, at 1-888-663-3639, facsimile 613-996-9178, or e-mail

Note: For the electronic version of this document, please consult the following Web address

For the Director, National Aircraft Certification

Original signed by

Rémy Knoerr
Continuing Airworthyness

The Transport Canada Civil Aviation Safety Alert (CASA) is used to convey important safety information and contains recommended action items. The CASA strives to assist the aviation industry's efforts to provide a service with the highest possible degree of safety. The information contained herein is often critical and must be conveyed to the appropriate office in a timely manner. The CASA may be changed or amended should new information become available.