The rugged and reliable Convair 340/440 platform was especially well-suited for conversion from piston engines to turboprop power. Operators added the Napier Eland engine (called the Convair 540) and the Rolls-Royce Dart (Convair 600 and 640) but the most common conversion used the Allison 501-D engine for the Convair 580, with the first example flying in 1961. This process also included an extension to the tailfin and lengthening of horizontal stabilizers, and were undertaken at Pacific Aeromotive in California, taking about 2 months. Frontier and Allegheny with their larger fleets were early adoptees of the 580, with North Central being the final carrier to undertake the process.
North Central
As North Central continued to gain route authorities in the late 1950s, leaders did look at the turboprop F-27 but its high cost and tight availability made the “used” market more appealing for the ever-frugal company. 5 CV-340s were acquired from Continental for $325,000 each, which was just the start as their productivity and low operating cost was perfect for NC’s system. Additional used Convairs were acquired by 1965 to bring the fleet to 28 examples (including the 340 and enhanced 440 variant).
In 1966 North Central signed a deal with Pacific Aeromotive to upgrade the first of an eventual 33 Convairs to 580 standard. First examples flew on the system in April 1967, and the work was completed in July 1969. Happily, NC found the upgraded aircraft were actually cheaper to operate than the piston-engined variant, and the extra speed allowed for more sectors to be flown per day, which put even more money in the bank! Passenger comfort was also well-appointed with wide, well cushioned seats and big windows. One of the fleet was converted into a special charter / executive transport.
23 of the passenger-configured 580s remained in service with North Central after the merger with Southern to form Republic Airlines in 1979, as well as the executive transport. Thirteen were still in service by 1986 and briefly joined the fleet of Northwest Airlines.
Republic
In the early 1980s, ballooning fuel prices and interest rates were two powerful arguments to keep the Convairs in the merged carrier – turboprops were more economical than pure-jets on RC’s many short-haul hops, and the airframes were paid for. CV-580s continued to support Minneapolis, Chicago, and Detroit, but were also sent south to Memphis and Atlanta to replace the unpopular and maintenance-intensive 19-passenger Swearingen Metroliners.
The Convairs were a popular upgrade on the former Southern local-service routes, but the advent of Republic Express, flying modern Jetstream 31s and Saab 340s with higher frequencies, allowed the 580s to migrate back north. The O’Hare feeder service was being wound down as well – and the Convairs which flew these routes were concentrated into Detroit and Minneapolis/St. Paul to build up short-haul frequencies on existing markets and open new stations like Akron/Canton, OH, Ft. Wayne, IN, and Erie, PA. The roll-out of Republic Express services from DTW/MSP allowed Republic to retire some of the older 580 frames, but also allowed the company to further utilize the type on routes where its 50-seat capacity could be filled. This role continued through the Northwest merger.
Northwest
As NWA blended its operations with Republic, the “best tool for the job” in the late 1980s for short-hop, high-frequency 50-seat hub supporting service in the combined company’s toolbox was still the Convair. The 13 remaining aircraft in passenger service were paid for with plenty of spare parts and had a stable cadre of crews and maintenance staff who knew it well. (N580N, the “executive conversion” aircraft, soon left the system.)
In addition, NWA’s Airlink carriers were constrained by contract scope clauses and available airframes from supplying lift in that intermediate range between 30-seat propeller aircraft and mainline DC-9-10 jets. Mesaba’s Fokker 27 turboprop fleet (fitted with 40 to 50 seats depending on the specific aircraft) was a menagerie of used frames and not getting any younger, either.
So the Convairs remained in service with hybrid titles (none were ever painted in the classic Northwest “thermometer” scheme) for two years after the merger, finally exiting the fleet in late 1988 as enough jets were sourced to cover lift in bigger markets, and as the Airlink carriers continued to grow their 30-seat fleets to add frequencies in smaller markets or to supplement frequencies on key short-haul routes.
The Convairs scattered across the earth, with many frames heading to Latin America, Canada, and even as far afield as New Zealand. Their last passenger services flew in the COVID era, and a handful still soldier on in cargo roles in the mid 2020s.
If you use these photos, please credit the Northwest Airlines History Center – please also contact us to let us know how you’re using them and if we can be of further help!
