Subject: Bomber Series--Boeing B-17 Fortress (12 of 27)

From: [email-masked] (joseph.f.baugher)
Date: 17 Aug 94 00:12:59 GMT

The YB-40 was the bomber escort variant of the Flying Fortress, where 
the Y stood for "service test".  This aircraft was produced in an 
attempt to provide better defenses for B-17 daylight bomber forces 
which were suffering appalling losses in their raids against German 
targets on the European continent.  The YB-40 was produced by 
converting existing B-17Fs in an attempt to provide additional 
firepower for the defense of bomber formations when they ventured into 
areas beyond the range of contemporary fighters.  

The first XB-40 prototype was produced in November of 1942 by the Vega 
division of Lockheed.  They converted a standard Boeing-built B-17F 
(serial number 41-24341) to escort configuration by adding a dorsal 
turret in the radio compartment position carring a pair of 0.50-cal 
machine guns, a chin turret underneath the nose equipped with a pair 
of 0.50 cal machine guns, and twin gun mounts instead of the usual 
single gun mounts at each waist position.  The regular top, belly, and 
tail turrets were retained, bringing total defensive armament to 
fourteen 0.50-inch machine guns.  Additional protective armor was 
fitted for better crew protection.  The bomb bays were replaced by 
storage areas which carried additional ammunition for the guns.  The 
normal ammunition load was 11,135 rounds, which could be increased to 
17,265 rounds if the fuel load was reduced.  

Twenty more Vega-built B-17Fs were converted to YB-40 configuration, 
plus four TB-40 trainers.  Although they bore the Vega model number of 
V-139-3, they were actually modified by Douglas at Tulsa, Oklahoma 
from Vega-built B-17F airframes.  A variety of different armament 
configurations was tried.  Some YB-40s were fitted with four-gun nose 
and tail turrets.  Some carried cannon of up to 40-mm in calibre, and 
a few carried up to as many as 30 guns of various calibres in multiple 
hand-held positions in the waist as well as in additional power 
turrets above and below the fuselage!  Oddly enough, there don't seem 
to have been any photographs ever published of these 30-gun YB-40s 
(insofar as I am aware), although I have seen some drawings.  

The first operational YB-40 sortie took place on May 29, 1943 against 
St. Nazaire.  Eight other missions were later flown, the last one 
taking place on July 4, 1943.  Five kills and two probables were 
claimed during these missions, with the loss of one YB-40.  Very early 
on, it was found that the net effect of the additional drag of the 
turrets and the extra weight of the guns, armor, and additional 
ammunition was to reduce the speed of the YB-40 to a point where it 
could not maintain formation with the standard B-17s on the way home 
from the target once they had released their bombs.  The YB-40 could 
protect itself fairly well, but not the bombers it was supposed to 
defend.  Consequently, it was recognized that the YB-40 project was an 
operational failure, and the surviving YB-40s were converted back to 
standard B-17F configuration or used as gunnery trainers back in the 
States.  However, the YB-40 was to have one lasting impact--the chin 
turret originally introduced on the YB-40 was later adopted as 
standard for the B-17G series.  

XB-40: Conversion of B-17F-1-BO 41-24342 

YB-40: Conversions of B-17F-10-VE 42-5732/5744, B-17F-30-VE 42-5871, 
and B-17F-35-VEs 42-5920, 5921, 5923, 5924, 5925, and 5927.  

TB-40: Conversions of B-17F-25-VEs 42-5833 and 5834, B-17F-30-VE 
42-5872, and B-17F-35-VE 42-5926.  

Sources:

  Flying Fortress, Edward Jablonski, Doubleday, 1965.

  Famous Bombers of the Second World War, Volume One, William
  Green, Doubleday, 1959.

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

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

  Boeing B-17E and F Flying Fortress, Charles D. Thompson,
  Profile Publications, 1966.

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

  Jane's Fighting Aircraft of World War II, Military Press, 1989.

Joe Baugher			**************************************
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