Subject: Bomber Series--Boeing B-9

From: [email-masked]
Date: 27 Jun 94 16:13:34 GMT

>From [email-masked]

The Boeing B-9 was the first cantilever monoplane bomber to be produced 
for the US Army.  The B-9 began life as the Boeing Models 214 and 215.  
These were company-funded new bomber designs that were based on the 
concepts developed by the Model 200 Monomail commercial mail carrier.  

Both the Model 214 and the Model 215 were low-winged, all-metal 
cantilever monoplanes.  The fuselage was of semi-monocoque 
construction, which permitted the use of a more nearly circular cross 
section.  The main landing gear retraced rearward into the engine 
nacelles, but the lower halves of the wheels remained exposed.  Five 
crew members were carried--pilot, copilot, nose gunner/bombardier, a 
rear gunner, and a radio operator.  Four of the crew members sat in 
separate open cockpits.  The bombardier/nose-gunner sat in a cockpit 
in the nose, which was equipped with a bomb sight and aiming window in 
the bottom and had a mount for a single flexible 0.30-inch machine gun 
around the top.  Because the fuselage was so narrow, the pilot and 
copilot sat in separate tandem cockpits immediately behind the nose 
gunner.  A fourth cockpit for a rear gunner was located on top of the 
fuselage behind the wing.  He operated a single flexible 0.30-inch 
machine gun.  The radio operator was located inside the fuselage just 
ahead of and below the pilot, and had a window on each side of the 
nose.  

The Models 214 and 215 had rudder servo tabs to assist the pilots in 
moving the controls, which was the first such installation on an 
American-designed aircraft.  An internal bomb bay was located in the 
fuselage at the center of gravity, and additional bombs could be 
carried on external underwing racks.  

The Models 214 and 215 were virtually identical to each other, 
differing primarily in the choice of engines.  The Model 214 was to be 
powered by pair of 600 hp Curtiss V-1570 Conqueror Prestone-cooled 
V-12 engines, whereas the Model 215 was to be powered by a pair of 600 
hp Pratt & Whitney Hornet air-cooled radial engines with NACA cowlings 
fitted around the cylinder heads for aerodynamic drag reduction.  On 
the 214, the servo tab on the rudder was a small auxiliary surface, 
whereas on the 215 the tab ran the full height of the rudder.  

The radial-powered Model 215 was the first to be completed.  It took 
to the air for the first time on April 12, 1931.  Since it was a 
Boeing-owned airplane, it was painted in civilian colors and carried a 
civilian registration number (X-10633).  It was initially powered by a 
pair of 575 hp Pratt & Whitney R-1830-13 commercial engines.  It was 
tested by the Army on a bailment contract under the designation 
XB-901.  It achieved a maximum speed of 163 mph at sea level.  

Favorable testing of the XB-901 resulted in the Army deciding on 
August 14, 1931 to purchase both the Model 215 and the Model 214.  The 
Model 215 was assigned the designation YB-9 and was given the serial 
number 32-301.  Now owned by the Army, the plane was repainted in 
military colors and the civil registration number was cancelled.  The 
Model 214 (which had not yet flown) was designated Y1B-9 and was 
assigned the serial number 32-302.  At the same time, the Army ordered 
five new planes under the designation Y1B-9A.  Serials were 32-303/307 

Following the Army order, the YB-9 was re-engined with Pratt & Whitney 
R-1830-11 Hornets supercharged to yield 600 hp at 6000 feet and was
fitted with three-bladed propellers.  With these new engines, the YB-9 
attained a maximum speed of 188 mph at 6000 feet, an impressive 
performance for 1931.  The era of the biplane bomber was clearly
nearing its end.  

The Y1B-9 (Model 214) flew for the first time on November 5, 1931.  
After testing with the liquid-cooled Curtiss Conqueror engines at the 
Boeing plant in Seattle and at Wright Field in Ohio, these engines 
were later replaced by Hornet radials, duplicating the YB-9.  

The Model 246 was the company designation for the five Y1B-9As that 
had been ordered by the Army at the same time that the two prototypes 
were purchased.  The Y1B-9A was powered by a pair of Pratt & Whitney 
Y1G1SR-1860B Hornet radials, rated at 600 hp at 6000 feet.  
Externally, the Y1B-9A was virtually identical to the YB-9.  However, 
the Y1B-9A had the rudder tabs of the Y1B-9 and it had metal instead 
of fabric covering on the control surfaces.  Three-bladed propellers 
were fitted.  There were also many internal structural and equipment 
changes.  Later, the shape of the rudder was changed to more closely 
resemble that of the Boeing Model 247 commercial transport.  Maximum 
speed was up to 186 mph with the altitude-rated engines.  

The first Y1B-9A flew on July 14, 1932 and was delivered to the Army 
on July 21.  The last Y1B-9A on the contract was delivered on March 
20, 1933.  The five Y1B-9As served with the 2nd Bomb Group based at 
Langley Field.  The high speed of the Y1B-9A indicated that enclosed 
cockpits for the crew would be needed.  Although a greenhouse cockpit 
canopy was designed for the Y1B-9A, it was never actually fitted.  

The B-9 was a truly revolutionary design, and had a speed fully 60 
percent greater than that of the Keystone biplane bombers that were 
still the backbone of the American bomber force in 1932.  Boeing fully 
anticipated an Army order for substantial numbers of the new design.  
However, The Glenn L. Martin company in Baltimore, Maryland had in 
the meantime brought out a competing design of its own, the XB-907.  
The XB-907 was even more revolutionary than the XB-901.  It was 
slightly larger than the XB-901 and had a substantially better 
performance.  The Army decided to order the Martin design into 
production under the designation B-10 and B-12, and no production 
examples of the B-9 were ordered.  

So far as I am aware, no examples of the B-9 survive today.  

32-301 		Boeing YB-9 (XB-901) 
32-302 		Boeing Y1B-9 
32-303/307 	Boeing Y1B-9A 

Specification of the YB-9: 

Two 600 hp Pratt & Whitney R-1830-13 air-cooled radial engines.  
Maximum speed 188 mph at 6000 feet, cruising speed 165 mph, landing 
speed 63 mph, initial climb rate 1060 feet per minute, service ceiling 
22,600 feet, absolute ceiling 14,400 feet.  An altitude of 5000 feet 
could be attained in 6 minutes.  Range was 495 miles with 1997 pounds 
of bombs.  Dimensions: wingspan 76 feet 9 inches, length 51 feet 6 
inches, height 12 feet 8 inches, wing area 954 square feet.  Weights: 
8362 pounds empty, 13,351 pounds gross.  Two 1100-pound bombs could be 
carried.  Defensive armament consisted of two 0.30-inch machine guns 
in nose and dorsal flexible positions.  

Specification of the Y1B-9: 

Two 600 hp Curtiss GIV-1570 (V-1570-29) Conqueror liquid-cooled 
twelve-cylinder Vee engines.  Maximum speed 173.5 mph at sea level, 
171.5 mph at 5000 feet, cruising speed 147.5 mph, landing speed 62 
mph, initial climb rate 1160 feet per minute, service ceiling 19,200 
feet, absolute ceiling 21,000 feet.  Range was 1250 miles.  
Dimensions: wingspan 76 feet 9 inches, length 51 feet 6 inches, height 
12 feet 8 inches, wing area 954 square feet.  Weights: 8618 pounds 
empty, 13,591 pounds gross.  Two 1100-pound bombs could be carried.  
Defensive armament consisted of two 0.30-inch machine guns in nose and 
dorsal flexible positions.  

Specification of the Y1B-9A: 

Two 600 hp Pratt & Whitney Y1G1SR-1860B Hornet supercharged air-cooled 
radials, rated at 600 hp at 6000 feet.  Maximum speed 188 mph at 6000 
feet, cruising speed 165 mph, initial climb rate 900 feet per minute, 
service ceiling 20,750 feet, absolute ceiling 22,500 feet.  An 
altitude of 5000 feet could be attained in 7.1 minutes.  Range was 540 
miles with a 2260 pound bombload, maximum range was 990 miles.  
Dimensions: wingspan 76 feet 10 inches, length 52 feet, wing area 954 
square feet.  Weights: 8941 pounds empty, 13,932 pounds gross, 14,320 
pounds maximum.  A load of 2260 pounds of bombs could be carried.  
Defensive armament consisted of two 0.30-inch machine guns in nose and 
dorsal flexible positions.  

Sources:

  United States Military Aircraft Since 1909, Gordon Swanborough and
  Peter M. Bowers, Smithsonian, 1989.

  American Combat Planes, Ray Wagner, Third Edition, Doubleday, 1982.

  U.S. Army Aircraft, 1908-1946, James C. Fahey

  Boeing Aircraft Since 1916, Peter M.  Bowers, Naval Institute Press, 
  1989 

Joe Baugher				AT&T Bell Laboratories
1000 E. Warrenville Road		Naperville, Illinois 60566-7013