Convair CV-640

The Convair CV‑640 is a turboprop conversion of the earlier Convair CV‑340/440 series, undertaken by Convair in the early 1960s to extend the commercial life of its piston‑powered airliners. After the success of the original CV‑340 and its larger sibling the CV‑440, airlines sought more economical, higher‑performance aircraft, prompting Convair to replace the original Pratt & Whitney R‑2800 radial engines with two Allison 501‑D13D turboprop units driving four‑bladed propellers. The conversion also incorporated a revised landing gear, strengthened airframe, and updated avionics, yielding a cruising speed of about 300 knots, a service ceiling of 25 000 feet, and improved fuel efficiency compared with the piston models. Operators such as Continental Airlines, Eastern Air Lines, and several regional carriers employed the CV‑640 on short‑haul routes throughout the 1960s and 1970s, appreciating its quieter cabin and reduced maintenance costs. Though only 82 conversions were completed, the CV‑640 demonstrated the viability of re‑engining legacy aircraft, influencing later programs like the Boeing 727 and DC‑9 turboprop proposals. Its modest success marked a transitional step between piston‑driven transports and modern turbofan jets, cementing its place in aviation history.

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