The Series 300 was introduced in 1969 beginning with serial number 231. Both aircraft performance and payload were improved by fitting more powerful PT6A-27 engines.
The Series 300 proved to be the most successful variant by far, with 614 Series 300 aircraft and their sub-variants (Series 310 for United Kingdom operators, Series 320 for Australian operators, etc.) sold before production ended in 1988.
This 300S aircraft series featured improved brakes, wing spoilers, general systems improvements, and fancy airliner-style accommodations for 11 passengers.