A blade on a Tacke Windtechnik TW 600e machine sited near Kamen in inland North Rhine Westfalia came to grief in mid February, the company confirms. The blade snapped along its spar at a wind speed of about 15 m/s and remained hanging from the hub after the machine had shut down. It was removed some hours later and since its replacement with a new blade the machine has been running again. "The break was a one-off case, clearly due to human error," says Hartmut Zoppke of Tacke Windtechnik. In the bonding of the spar to the two halves of the blade, one of the four surfaces to be bonded had not been roughened so the glue had no purchase. "Such an error makes itself apparent very quickly," says Zoppke. The machine had only been in operation for about two weeks when the break occurred. The faulty blade was made by the Tacke Windtechnik blade factory at Huron Park in Ontario, Canada. The blade-making process is "stable" but one-off errors can never be entirely ruled out where crucial parts of the manufacture are carried out by hand, says Zoppke. Tacke has, however, installed additional quality control checks during production at the Canada works.