The coupled flutter of a pinwheel wide-chord blade was studied.In view of the pinwheel blade

the theoretical analysis made for the original pinwheel blade showed that some typicaly coupled flutter problems between the first-order bending vibration and the first-order torsion vibration occured on the blade.The blade was re-designed and the frequencies of the first-order bending vibration and the first-order torsion of the modified blade were changed so as to effectively avoid the coupled flutter.The cumulative test of the reliability shows that the cracks are found in the original pinwheel blade after running 80 hours

while the modified blade can run safely over 200 hours.