AL 2002-05
15 July 2002
P/N 350A33.1058.03
Transport Canada has recently received two Service Difficulty Reports (SDRs) identifying cracks on the pitch change control bellcrank installed on two different AS 350B series rotorcraft. The subject bellcranks had 7461 and 1209 hours.
Both of these SDRs report cracks were found on the webs located on the upper outboard side of the bellcrank lever attached to the control rod end. A review of the SDR database and input from the manufacturer revealed that these two SDRs are the only reports of failure of this particular bellcrank.
Transport Canada forwarded the failed bellcranks to French Airworthiness Authority (DGAC) to facilitate analysis by Eurocopter France. Preliminary feedback from the manufacturer has confirmed the presence of cracks on both bellcranks located in the two upper ribs between the fork-end and the hinge bolt. These failures appear to be fatigue related originating on the upper radius and propagating toward the center web. The manufacturer has also cautioned that if the bellcrank is not installed in accordance with recommended instructions that control loads could result in damage to the lugs of the gearbox casing yoke, the bellcrank expandable hinge bolt and the pitch change unit.
In the interim, since the manufacturer has not yet completed their final analysis to determine the cause of these failures, Transport Canada hereby advises all operators of AS350/355 series rotorcraft to pay particular attention during inspection for possible cracking of the bellcrank. In addition, conduct a detailed inspection of the bellcrank assembly to verify that the installation is in accordance to the manufacturers' instructions.
Crack found on webs on the upper side of the bellcrank
Any defects or further occurrences should be reported by sending a Service Difficulty Report to Transport Canada, Continuing Airworthiness, Ottawa.
For further information, contact a Transport Canada Centre, or Mr. Barry Caldwell, Continuing Airworthiness, Ottawa, telephone (613) 952-4358, facsimile (613) 996-9178 or e-mail caldweb@tc.gc.ca.
For Director, National Aircraft Certification
B. Goyaniuk
Chief, Continuing Airworthiness