Subject: Bomber Series--Keystone B-4

From: [email-masked]
Date: 16 Jun 94 02:21:36 GMT

>From [email-masked]

In 1930, seven Keystone biplane bombers were ordered under the 
designation LB-13.  They were to be equipped with single vertical 
tails and were to be powered by a pair of 525 hp Pratt & Whitney 
GR-1690 radials.  Serials were 30-344/353.  

However, in the early 1930s, the USAAC abandoned its separate 
classification scheme for light (LB) and heavy (HB) bombers, and 
grouped them both under the B category.  The bombers in the LB series 
already under order had to be redesignated.  In particular, of seven 
LB-13s ordered, five were completed as Y1B-4s with 575 hp R-1860-7 
engines (30-344/348).  

On April 28, 1931, the Army ordered 25 examples of the B-4A, which was 
an improved production version of the Y1B-4.  Serials were 32-117/141.  

Like the B-3A, the B-4A carried five crew members--two pilots, a 
bombardier, and a front and rear gunner.  The B-4A was externally 
almost identical to the B-3A which preceded it (as well as to the B-5 
and B-6 which followed it).  These Keystone bombers usually differed 
from each other only in the type of engine which powered them, and it 
was often only possible to distinguish one from the other by an 
examination of their serial numbers.  

30-344/348 	Keystone Y1B-4 
32-117/141 	Keystone B-4A 

Specification of the Keystone B-4A: 

Two 575 hp Pratt & Whitney R-1860-7 air-cooled radial engines.  
Maximum speed 121 mph at sea level, 103 mph cruising speed.  Initial 
climb rate 690 feet per minute.  An altitude of 5000 feet could be 
reached in 8.6 minutes.  Service ceiling 14,000 feet.  Range 855 
miles.  Weight: 7951 pounds empty, 13,209 pounds gross.  Wingspan 74 
feet 8 inches, length 48 feet 10 inches, height 15 feet 9 inches, wing 
area 1145 square feet.  Armed with three Browning machine guns, one in 
each of nose, dorsal, and ventral positions.  A bomb load of 2500 
pounds could be carried.  

Sources:

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

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

  American Warplanes, Bill Gunston

  Jane's Encyclopedia of Aviation

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

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