Page 35 - Volume 14 Number 10

By design, the Cloudboy was a utilitarian flying machine. Although it lacked the graceful lines of its older siblings, the C3B and the Model 4 series biplanes, the Model 6 was a tough aircraft that could withstand the errors of student pilots in stride. In an effort to keep manufacturing costs to a minimum, the Cloudboy used conventional conduction practices for the time – a fabric-covered fuselage fabricated from welded chrome molybdenum steel tubing, wood wings with spruce spars with Friese-type ailerons on both the upper and lower panels.
The upper wings spanned 32 feet and the lower panels 28 feet with a chord of 60 inches for both sets. Total wing area was 272 square feet. An N-22 airfoil section was employed that provided good handling characteristics at the stall, during low-speed maneuvering and while landing. A simple but effective outrigger-type main landing gear with shock struts was installed and a tailskid replaced the tailwheel found on the more expensive Stearman airplanes.
The J6-5 engine ensured that the Model 6’s performance would be less than stellar, but it would be more than adequate for the flight training mission. Maximum speed was only 110 mph, slowing to 90 mph for cruise with a stall speed of 50 mph. The first airplane built (serial No. 6001) registered X786H, was soon followed by two other ships registered NC787H and NC795H. In September 1930 the Bureau of Aeronautics awarded the Model 6A Approved Type Certificate No. 365.
During 1930 and 1931 a series of other radial engines were approved for the Cloudboy, including a 165-horsepower Continental (Model 6F), the five-cylinder Kinner R-715 rated at 210 horsepower (Model 6H); the Model 6L equipped with a 215-horsepower Lycoming R-680, and the 300-horsepower Pratt & Whitney Wasp Junior engine (Model 6D). Lloyd’s hopes for a military contract increased when the United States Army Air Corps held a competition aimed at selecting a new primary trainer that would finally put the PT-3 out to pasture.
The Model 6 fit the Air Corps’ requirements well and the company submitted the first Model 6A built for evaluation and was assigned the military designation XPT-912. In the wake of flight trials held at Wright Field in Ohio, the ship was flown back to Wichita and a second Model 6A was built to comply with modifications specified by the Air Corps. In December 1930 another series of tests were conducted, followed by a contract to construct four airplanes for full service testing.
These aircraft, however, carried the designation YPT-9 and were powered by the Wright J6-5 powerplant. The first ship was delivered March 2, 1931. Soon after, the
other three airplanes were flown by Lieutenants C.J. Crane, A.C. Kelly and C.B. McDaniel to Brooks Field, San Antonio, Texas. Two of the pilots, Crane and Kelly, were instructors while McDaniel was an engineering officer as well as an instructor. Three of the aircraft were assigned to the 11th Training School Group based at Brooks Field, but the fourth YPT-9 went to Wright Field for further evaluations. In addition, one of the ships was displayed at the annual Detroit aviation show held in April 1931.
All of the service test airplanes underwent a series of engine changes and other modifications in an effort to improve climb performance, but the Air Corps chose the Consolidated YPT-11 over the YPT-9 and other competitors. Senior officials of the Stearman company
The Model 6 was designed from its inception as a commercial biplane and a primary trainer for the military. Late in 1930
the Stearman company was awarded a contract by the Army Air Corps to build four airplanes designated YPT-9. Note the tailskid that replaced the tailwheel on commercial ships. (Walter House Collection)
OCTOBER 2020
KING AIR MAGAZINE • 33