Subject: Bomber Series--Boeing B-17 Fortress (1 of 27)

From: [email-masked]
Date: 25 Jul 94 16:52:29 GMT

>From [email-masked]

The B-17 Flying Fortress was perhaps the most well-known American heavy 
bomber of the Second World War.  It achieved a fame far beyond that of 
its more-numerous stablemate, the Consolidated B-24 Liberator.  A 
total of 12,677 Fortresses was built before production came to an end.  
In August of 1944, the B-17 equipped no less than 33 overseas combat 
groups.  It was to achieve lasting fame in the daylight 
precision-bombing campaign over Germany in 1943, 1944, and 1945.  It 
achieved a reputation as being capable of absorbing a tremendous 
amount of battle damage and still continuing to fly.  In later 
variants, it had an exceptionally-heavy defensive armament.  It had an 
excellent high-altitude performance.  It was able to win the affection 
of the crews who flew in it, since it was often able to bring them 
home safely when other aircraft would have fallen.  However, the B-17 
generally had a performance inferior to that of its B-24 stablemate 
and it could not carry nearly as large a bomb load.  In typical 
missions over Europe, B-17s usually carried a bombload only as large 
as that which a twin-engined Mosquito could carry.  

B-17s dropped 640,036 tons of bombs on European targets during the 
war, as compared to 452,508 tons dropped by the Liberator and 463,544 
tons dropped by all other US aircraft.  Boeing records claim that the 
Fortress destroyed 23 enemy aircraft per thousand sorties as compared 
to 22 for Liberators, eleven by US fighters, and 3 by all US light and 
medium bombers.  However, the "kill" claims by both Fortress and 
Liberator gunner crews are probably greatly exaggerated, largely 
because the same enemy aircraft was being fired at by many different 
people.  Approximately 4750 B-17s were lost on combat missions, which 
is about one out of three of all B-17s built.  

The origin of the Boeing Fortress can be traced to a February 1934 
Army Air Corps requirement for a bomber with a range of 5000 miles at 
200 mph while carrying a bombload of 2000 pounds.  This became known 
as "Project A", and was more of a feasibility study than it was a 
serious proposal for a production bomber.  However, there was always a 
possibility that production examples would be ordered if the design 
proved successful.  Both Martin and Boeing submitted preliminary 
designs in response to the "Project A" requirement.  The Martin 
project was cancelled before anything could be built, but the Boeing 
design (assigned the company designation of Model 294) was awarded a 
contract for a single example under the designation XBLR-1.  The 
XBLR-1 was later redesignated XB-15.  

In May of 1934, the Army announced another bomber competition.  This 
time, it was for a multi-engined bomber capable of carrying a ton of 
bombs at more than 200 mph over a distance of 2000 miles.  As opposed 
to the "Project A" requirement, this Army requirement envisaged from 
the start that the winning design would have a production run of as 
many as 220 planes.  Several manufacturers (including Boeing) were 
invited to submit bids, with the entries being flown at Wright Field 
in a final competition to select the winner.  Preliminary work by 
Boeing on the design began on June 18, 1934.  Boeing engineers came up 
with what was basically a scaled-down version of the Model 294.  Like 
the Model 294, it was to be powered by four engines.  Four-engined 
bombers were a novelty at the time, most contemporary bomber designs 
having only two engines.  Construction began on August 16, 1934 under 
the company designation Model 299.  

The Model 299 was based heavily on the company's experience with the 
all-metal Model 247 commercial airliner.  It was basically a marriage 
between the aerodynamic and structural features used by the Model 247 
and the basic four-engined format used by the Model 294 bomber.  The 
aircraft was to be powered by four 750 hp Pratt & Whitney R-1690-E 
Hornet nine-cylinder air-cooled radials, each driving a three-bladed 
propeller.  The large, thick-section wing was to be mounted low on the 
cylindrical-section fuselage.  The main landing gear was to retract 
forward into the inner engine nacelles, with the lower edge of the 
wheel protruding into the airstream.  

The Model 299 aircraft was painted with the civilian registration 
X-13372, since it was a company-owned aircraft.  It carried a crew of 
8, a pilot, copilot, bombardier, navigator/radio operator, and four 
gunners.  There were four blister-type flexible machine gun stations, 
each of which could accommodate a 0.3-inch or 0.5-inch machine gun.  
One was in a dorsal position in the fuselage just above the wing 
trailing edge, a second was in a ventral fuselage position just behind 
the wing trailing edge, and a blister was mounted on each side of the 
rear fuselage in a waist position.  There was an additional station 
for a machine gun in the nose.  All of the guns were manually swung.  
Up to eight 600-pound bombs could be carried internally.  Loaded 
weight was 43,000 pounds.  

In order to prevent damage by wind to the tail surfaces while the 
plane was on the ground, the elevators were locked in position.  
Before takeoff, the pilot would unlock the tail surfaces by releasing 
a spring lock in the cockpit.  

First flight of the Model 299 took place on July 28, 1935 at Seattle 
with Boeing test pilot Leslie R. Tower at the controls.  According to 
legend, a reporter having seen the 299 for the first time remarked, 
"Why, it's a flying fortress!".  The name stuck.  

After a short period of factory testing, the Model 299 was flown by 
Boeing test pilot Leslie Tower and three other crewmen out to 
Wright Field on August 20 for Air Corps evaluation.  During this 
flight, it flew the 2100 miles nonstop at an average speed of 232 mph 
at an average altitude of 12,000 feet, breaking all records for the 
distance.  

The prototype was submitted to the Army as Model X-299, but the Army 
objected to the designation as being too similar to its experimental 
military project numbers, so it was officially changed to B-299.  

The competitors of the B-299 were the Martin 146 and the Douglas DB-1, 
which were both twin-engined designs.  The Model 299 surpassed all the 
Army requirements for speed, climb, range and bombload.  The Army 
decided to purchase 65 service test examples under the designation 
YB-17.  

On October 30, 1935, the Model 299 crashed during takeoff at Wright 
Field and burned.  Three of the crewmen managed to crawl out of the 
wreckage with only minor injuries, but pilot Ployer P. Hill (chief of 
Wright Field's Flight Testing Section) and Boeing test pilot Leslie 
Tower (who was riding as an observer) both died later of their injuries 
after being dragged from the burning aircraft.  An investigation later 
showed that the crash was caused by the crew forgetting to unlock the 
tail surfaces before takeoff, the aircraft losing control immediately
after leaving the ground and crashing.  

Although the aircraft was blameless in the crash, the Air Corps got 
cold feet about the wisdom of acquiring so many YB-17s with the 
limited funds that were available and cut their order back to to only 
13 examples on January 17, 1936.  The designation was changed to 
Y1B-17 on November 20, 1936, the "Y1" designation indicating that they 
were purchased from "F-1" funds rather than from regular 
appropriations.  

As insurance, the Army decided at the same time to order 133 examples 
of the competing twin-engined Douglas DB-1 under the designation B-18.
The B-18 was substantially slower than the Flying Fortress, had a 
shorter range, carried fewer bombs, and had a poorer defensive
armament.  However, it was only half as expensive as the B-17 and 
since the B-18 was based on a proven design (the DC-2 commercial
airliner), the amount of risk was deemed to be smaller.

The wreckage of the B-299 was salvaged and a section of the fuselage 
containing the the side blisters was used at Wright Field for the 
evaluation of new types of gun mounts.  

The Model 299 never carried a US Army serial number.  

Specification of Model 299: 

Four Pratt & Whitney R-1690E S1EG Hornet radials rated at 750 hp at 2250 rpm 
at 7000 feet.  Maximum speed 236 mph at 10,000 feet.  Cruising speed 204 mph. 
Service ceiling 24,620 feet.  Range 2040 miles with 2573 pounds of
bombs.  Maximum range 3101 miles.
Dimensions: Wingspan 103 feet 9 3/8 inches, length 68 feet 9 
inches, height 14 feet 11 15/16 inches, wing area 1420 square feet.  
Weights: 21,657 pounds empty, 32,432 pounds normal loaded, 38,053 
pounds maximum.  Armed with five 0.30-inch machine guns, with one gun 
in each of nose, dorsal, ventral, and two waist positions.  A maximum 
of eight 600 pound bombs could be carried in an internal bomb bay.  

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.

  McDonnell Douglas Aircraft Since 1920: Volume 1, Rene Francillon,
  Naval Institute Press, 1988.

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

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

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