Don't forget the Tu-95/-142 Bear when thinking of speedy propellor aircraft. Props and a swept wing!:o
A couple of reasons for "scimitar props":
Props on an Islander
Below is G-NESU, the North East Spotter Unit which is a Britten-Norman BN-2B-20 Islander.
Based at Teesside Airport, it acts just as the helicopter does.
They are currently evaluating scimitar-shaped Hartzell propellors whcih are developed by NASA!
They are being used to reduce the Islander's noise footprint.
Hartzell Props PR
The blades are highly twisted from root to tip which is a characteristic of most higher performance
propellers allowing designers to optimize cruise while incurring the smallest possible drag penalties.