Beech Aircraft designed a high-performance tactical aircraft during the latter days of World War II.
Outstanding performance held promise of a bright future for the aircraft, but lack of availability of engines delayed the program so that its single contribution was to enhance the reputation of Beech Aircraft.
Designated the Beechcraft Model 28, the big, twin-tailed attack aircraft was known to the United States Army Air Force as the XA-38. It also was named the Destroyer and, more popularly, the Grizzly.
The Beechcraft Model 28 combined the size of a medium bomber with the speed of the fastest propeller driven fighters of the day. It was highly maneuverable and could take off and land in an area considerably smaller than needed by other airplanes of a comparable size.
The XA-38 was a departure in attack planes, being built around a 75mm automatic cannon, which extended from the nose of the ship, giving the plane a most distinctive appearance. The aircraft carried a pilot and gunner and mounted six .50 caliber machine guns in addition to the cannon. It was designed as an attack plane with a primary mission of attack and destruction of tanks, armored vehicles, light surface vessels, ground installations and submarines by gunfire. A secondary tactical mission of bombing and laying smoke screens could be performed by externally mounting bombs, depth charges and chemical tanks.
Empty weight of this twin-engine all-metal mid-wing monoplane was 23,230 pounds with a design gross weight of 29,900 pounds; however, various combinations of fuel, oil, external bombs, external long range fuel tanks and smoke tanks could be carried at gross weights up to maximum alternate gross weight of 36,332 pounds.
Length of the plane was 51.7 feet and wing span 67.08 feet. Outside maximum width of the fuselage was 56 inches and maximum fuselage height 92 inches.
Every means possible was employed to decrease drag, including flush riveting of all exposed skin surfaces. A striking demonstration of the resultant speed was furnished the Army when it assigned one of its fastest fighters to pace the XA-38 for speed calibration tests and found the Beechcraft outdistancing the fighter.
Despite these high speeds, the airplane at a gross weight of 31,250 pounds could land at low speed in a small area.
The forward part of the fuselage had a steep slope downward permitting the pilot an excellent view downward and forward. Access to the pilot's compartment was through a hinged section of the cockpit enclosure and was reached from the upper surface of the wing.
Cooling of the huge Wright Cyclone R-3350 engines was obtained from circular cowlings of the NACA type and careful design of the cowl entrance and exit, as well as by locating the exhaust stacks so that they augmented the flow of exiting air. Cooling was controlled by automatic cowl flaps operated by a control unit having a temperature element in the hottest engine cylinder.
Propellers were three-bladed, constant speed and full feathering, Hamilton Standard, with a minimum blade angle of 16 degrees and a maximum blade angle of 82 degrees as measured at the 72-inch radius.
Wing air foil section was derived from NACA-2300 series, 18.87 percent thick at the root chord and 12 percent at the tip chord. The wings were of conventional all-metal construction with an area of 625.9 square feet. Taper ratio was 3.07 to 1; incidence 4.39 degrees at the root and 1 degree at the tip; dihedral, measured at the quarter chord point, 5 degrees and aspect ratio 7.19.
For flight in icing conditions, leading edges were heated through internal air ducts and the entire surfaces of the wings were warmed by air discharged from the leading edge ducts and passed through the wing to the trailing edges.
The main spar was located at 25 percent of the wing chord and the rear spar at 75 percent of the wing chord. These spars were designed as the principal structural members resisting bending. Wing tips and outer panels were removable to facilitate fabrication and replacement. The center section was built in halves, joined together at the fuselage center line. Slotted type flaps extended over the span of the center section on each side, except for the portion enclosed in the fuselage. Ailerons extended from the outer panel joint to the removable tip.
Control surfaces were conventional with ailerons, elevators and rudders aerodynamically, dynamically and statically balanced.
Aileron area was 51.7 square feet, or 8.2 percent of the wing area with each aileron equipped with a balancing tab; the tab in the left aileron also acting as a trim tab controllable from the cockpit.
The dual vertical tail was similar in design to the twin-engine Beechcraft Model 18 series. Fins had an area of 33 square feet. Rudders had an area of 36. 8 square feet and were constructed with a formed aluminum alloy frame. Metal covered over the nose section. The chord of this balance area was increased somewhat near the top to provide additional balance area.
Area of the horizontal stabilizer was 115 square feet, with a span of 230 inches and a maximum chord of 81 inches. Stabilizers had an area of 64 square feet and construction was two spar, skin and stringer. The elevator area was 50.9 square feet and was constructed with a formed sheet metal aluminum alloy frame. Fabric covered over the portion aft of the elevator spar, with an aluminum alloy sheet covering over the nose section.
Slotted-type flaps had a control system designed to prevent retracting the flaps at a rate rapid enough to cause the airplane to settle in a dangerous manner. Each flap had a span of 155.5 inches, and the plane had a total flap span of 372 inches. Average flap chord was 29.48 inches and area 63.8 square feet.
Fuselage construction employed bulkhead rings and longitudinal stringers. Openings were reinforced by heavy stringers or box sections where extra rigidity was required.
Fuselage construction was in four main sections to permit easy repair and replacement. The entire forward section of the nose was arranged on counterbalanced springs to open like the hood of an automobile and expose the 75mm cannon for servicing and replenishment of ammunition. The nose section, complete with cannon, could be removed and replaced with other nose sections equipped with other armament arrangements.
The landing gear consisted of two large main wheels and a full swiveling tail wheel. Both main wheels and tail wheel were retracted and extended by hydraulic means, with separate and completely independent hydraulic and pneumatic emergency systems. The auxiliary systems were independent of the main system up to, but not including, the actuating cylinders. Shock struts were of the oleo-pneumatic type.
Wheel doors were operated mechanically through linkage to the landing gear mechanism. Main wheel doors opened while the wheels were extending or retracting and closed when the wheels were fully down or fully up. This feature minimized damage to the door structure due to buffeting.
Following its first flight May 7, 1944, the airplane was flown to Eglin Field, Fla., where it underwent extensive Army tests. In these tests it established outstanding records for availability, for flight and for efficiency.
Twin engine with 75mm cannon
TECHNICAL NOTES: Armament: Six .50-cal. machine guns (two fixed in the lower forward nose and two pairs in General Electric remote-controlled dorsal and ventral turrets), one 75mm cannon, plus a variety of external stores including bombs, fuel tanks, smoke screen chemical tanks, torpedoes and depth charges Engines: Two Wright GR-3350-43 Cyclone radials of 2,300 hp each Maximum speed: 370 mph at 17,000 ft. Cruising speed: 350 mph at 16,000 ft. Range: 1,625 miles Service ceiling: 29,000 ft. Span: 67.08 ft. Length: 51.7 ft. Height: 15 ft. 6 in. Weight: 36,332 lbs. maximum alternate gross weight Crew: Two (pilot and gunner) Serial numbers: 43-14406 and 43-14407; Beechcraft Model 28