Improved tailrotor could help restore Canada's EH101 search-and-rescue fleet to full availability
AgustaWestland has produced an improved tail-rotor hub for Canada's CH-149 Cormorant (EH101) search-and-rescue (SAR) helicopter fleet in an effort to solve a cracking problem that has severely restricted operations and kept fleet availability at about 50% for the past nine months.
"An improved-manufacture half-hub has been produced and tested, and is currently undergoing clearance to fly on the CH-149," says Canada's Department of National Defence (DND), adding: "AgustaWestland is also pursuing other half-hub redesign activities."
Discussions are continuing between the Canadian government and the manufacturer over possible compensation for the problems, says the defence ministry. "At this time, the manufacturer has not charged the department for replacements or repairs."
AgustaWestland says the modified parts, which have been produced using an improved manufacturing process, are being shipped to Canada to start flight-testing "in the very near future". The cracking problem has occurred only in Canada's EH101 fleet and does not affect other operators, possibly because of the demands of SAR operations, says the company.
Cracks were first discovered in the half-hubs, which connect the helicopter's tail-rotor blades to the drive shaft, in October 2001, soon after the type's entry into service in Canada. The problem was first handled with more frequent inspections and it was only in October 2004, when severe cracking was found in one aircraft, that restrictions were tightened.
Those cracks were found 5.4 rotor hours after the previous daily inspection and 16.5 rotor hours after the previous 50-hour inspection. To date, 89 cracked half-hubs have been found, replaced and sent to AgustaWestland for repair.
"Over the past nine months, aircraft availability has averaged between seven and eight Cormorants out of a total of 15 aircraft," says the DND. Nine aircraft are now flying. Canada has restricted its fleet to training and SAR missions only and training flights are limited to two hours' duration. It also carries out daily half-hub inspections, with more detailed examinations at 50h and 200h intervals.
"No formal conclusions" have been reached on whether the cracking in Canada's rotor half-hubs could be related to the March 2004 crash of a UK Royal Navy EH101 Merlin HM1. AgustaWestland says the US101 selected as the USA's next presidential helicopter has a completely redesigned tail rotor.
ANDRZEJ JEZIORSKI/VANCOUVER
Source: Flight International
