In the late 1960s, the U.S. was deeply entrenched in the Vietnam War and aircraft development was markedly different than it is now. Rather than shoehorning one type into myriad roles in an effort to reduce development costs, as is done today, the U.S. military leaned strongly toward the belief that it was better to develop unique aircraft types tailored specifically to each role. Aircraft manufacturers predictably rose to the challenge and constantly competed with each other in pursuit of new aircraft contracts, large and small.
Cessna was no exception. Beginning with the O-1 Bird Dog in 1949, the company went on to manufacture a number of other military aircraft, including the T-37/A-37 jet and military versions of the 172, 185, 310, and 337. In the year following the introduction of the militarized 337, known as the O-2, Cessna spotted an opportunity to create a modified version and wasted no time manufacturing a full-scale mockup.
Known as the Cessna O-2TT, the proposed aircraft was an intriguing blend of design elements collectively focused on forward air control missions. Using the O-2 as a starting point, Cessna replaced the 210 hp piston engines with 317 hp Allison 250 turboprops. This, Cessna predicted, would result in notably improved performance.
In a November 1968 press release, Cessna listed the performance specs of the 3,220-pound (empty) O-2TT. Cruise speed at 75 percent power was listed as 174 knots and the rate of climb in standard conditions was listed as 2,160 feet per minute. The rate of climb with one engine out ranged from 710-795 feet per minute depending on which engine was shut down, but the specification sheet doesn’t articulate whether this is at the maximum (normal) takeoff weight of 5,000 pounds or the maximum (alternate) takeoff weight of 5,750 pounds. Useful load is listed as 1,780 pounds (normal) and 2,530 pounds (alternate).
More visually notable were the changes made to the fuselage. In an effort to provide the two occupants with unrestricted visibility, Cessna extended the forward fuselage dramatically, positioning each seat forward of the wing. Because the 138-pound Allison turbine engine was less than half the weight of the Continental piston engine it replaced, the repositioning of the forward engine would have been necessary regardless to maintain the proper center of gravity.
With both passengers moved forward, the change opened up ample space beneath the wing. Judging by the mock-up, enough space would be available for a third seat, but as the mission requirements only call for two occupants, it would instead be utilized for equipment and cargo. Given the additional fuel burn of the turbine engines, it could also be utilized for an auxiliary fuel tank to extend range and endurance.
To improve short takeoff and landing (STOL) performance, Cessna proposed modifying the wing as well. By increasing the span by over 4 feet and wing area by nearly 20 square feet, the wing would be notably larger than that of the standard O-2. Additionally, the O-2TT would incorporate high-lift devices to further improve STOL performance including a constant-radius leading edge and drooped ailerons interconnected with single-slotted flaps.
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The relatively straightforward and well-thought-out modifications used to create the O-2TT concept would likely have resulted in a formidable tool for use in forward air control missions. The improved, unrestricted visibility from each seat would have made the job easier for the occupants, the turbine engines would have improved performance and reliability, and the slow-turning propellers would have made the aircraft less noticeable to enemy units on the ground.
Unfortunately, the O-2TT concept never reached production, and the sole mock-up was presumably destroyed. In late 1969, the North American Rockwell OV-10 Bronco would enter service to fulfill the role—perhaps not coincidentally with twin turboprop powerplants, forward tandem seating with unrestricted visibility, and cargo space behind the two occupants.
