As I continue working my way through the updated and revised second edition of Cessna Warbirds, I’ll keep posting some excerpts. Chapter 5 is one of the longest chapters and details the long and storied history of the L-19 Bird Dog, which served admirable in both the Korean and Vietnam Wars.
If you missed the earlier excepts, be sure to catch up on them:
The Cessna Dynasty
The First Military Cessnas
The T-50 Bobcat
Since the Bird Dog chapter is so long, I’ll post a two-part except. Even so, this will represent less than 10% of the total chapter, which is about the length of typical novella with dozens of photos.
So, here we go…Chapter 5:
The L-19/O-1 Bird Dog
In August 1949, the US Army and the US Air Force announced a competitive procurement for an Army Observation Aircraft—an all‑metal, two‑place, high‑wing observation aircraft to replace the fabric‑covered Piper L‑4s and Stinson L‑5s that had served admirably during and after World War II. The new aircraft—intended to operate on wheels, skis, and floats—would serve as a platform for ground observation, aerial search and rescue, visual and photographic reconnaissance, forward air control (FAC), cargo and personnel transport, control and adjustment of artillery fire, and pilot training. In addition, the Army wanted a rugged aircraft easy to maintain in the field and able to operate from unimproved forward airstrips. The official specification, released on November 15, 1949, included a requirement for landing over a 50‑foot obstacle in a total distance of less than 600 feet. The Army scheduled a fly‑off between competing contractors (Piper, Taylorcraft, Temco, and Cessna) for March 1950.
With several civilian projects underway and an engineering staff of only 18, Cessna decided to capitalize on their existing designs to meet the planned fly‑off date. They chose the basic wing design of the Model 170 and the tail assembly of the Model 195 (which the military had already purchased as the LC‑126), and focused the majority of their design efforts on a new fuselage, new landing gear, and new powerplant installation. The landing‑distance‑over‑an‑obstacle requirement necessitated high‑drag, high‑lift flaps (unlike the plain or split flaps on other Cessnas of the day), manually operated to save weight. Cessna engineers decided to modify the 170’s 45° slotted flap design to allow for 60° of extension by using an external hinge bracket with a pivot point below the wing (a configuration later seen on civilian Cessnas).
They chose the six‑cylinder, 190‑horsepower Continental O‑470‑11, with a 213‑horsepower takeoff power rating, which Continental modified to meet the Army design and performance requirements. They coupled this to a 90‑inch McCauley two‑blade, fixed‑pitch, metal propeller with a very low pitch. This allowed high RPM for short takeoffs and landings but reduced available power at cruise to avoid exceeding the rated RPM. The carburetor delivered more pressurized fuel than the engine required so they installed a fuel return line. A unique fuel valve design ensured adequate flow while returning excess fuel to the currently selected tank (another design subsequently used on other Cessnas).
The engineers laid out the fuselage design on full‑scale Mylar sheets stretched out on six bolted‑together drafting tables. The Cessna Experimental Department built the first fuselage from laminated aluminum templates created from the original full‑scale Mylar prints. Prototype construction began on September 8, 1949. The first Model 305 rolled out of its Wichita womb a mere 90 days later.
The 1,400‑pound aircraft (200 pounds over the specification weight) sported a semi‑monocoque aluminum fuselage with bulkheads and stringers made of aluminum alloys. The semi‑cantilever wings, like those of the C‑170 from which they had been borrowed, had dual spars, stressed aluminum skin, and single struts. The cockpit provided tandem seating for a pilot and observer in a fishbowl of Plexiglas—windows all around plus six panels in the cabin roof. The pilot and observer each had a full set of flight controls, although the observer could remove and stow the control stick when it was not needed.
Model 305 engineering prototype (N41694). Kansas Aviation Museum/Robert J. Pickett Collection photo
The new airplane first flew on December 14, 1949. After further factory test flights to determine the optimum takeoff and landing procedures to meet the short‑field requirements, Cessna’s Chief Test Pilot, Hank Waring, ferried the prototype (registration number N41694) to Wright Field in Dayton, Ohio. During the fly‑off evaluation, conducted between April 6 and April 14, the prototype Model 305 logged just under four hours. When the 305 proved it could meet or exceed all performance requirements, including the rigorous 600‑foot landing over a 50‑foot obstacle, its slight weight problem ceased to be an issue. The Army notified Cessna on May 29, 1950, that they had won the competition and would be issued a contract for 418 aircraft, designated the L‑19A.
The Army requested delivery of the first production aircraft by September 1950, but that was delayed until December while Cessna acquired an approved type certificate from the Civil Aeronautics Administration (CAA—forerunner of today’s Federal Aviation Administration), as the Army had mandated adherence to Civil Aeronautics Regulations rather than military standards. The CAA pilots put the new aircraft through its paces between August 2 and October 26, 1950.
NOTE: This presents only a very small portion of the Bird Dog story, an aircraft produced by Cessna until 1963 with more than 3,000 delivered to the US Army and Air Force and armed forces around the world..
Copyright ©2013 Walter P. Shiel. All Rights Reserved.