Subject: Number Fifty-Six in the Series--Northrop XP-56 "Black Bullet"

From: [email-masked]
Date: 5 Mar 93 18:39:37 GMT

>From [email-masked]

The experimental Northrop XP-56 flying wing fighter of 1943 was one of 
the most unusual fighter aircraft to be evolved by any of the 
combatants during World War II.  Although unsuccessful in attaining 
production, the XP-56 gained a lot of valuable data on flying wing 
designs, some of which was ultimately used in the design of the 
Northrop B-2 stealth bomber of the 1990s.  

The founder of Northrop Aircraft Inc.  was John Knudsen "Jack" 
Northrop, who at one time worked for Loughead Aircraft Manufacturing 
Company (later changed in spelling to Lockheed) as well as for Douglas 
Aircraft.  It is not widely known, but there were actually THREE 
separate and distinct aircraft companies that carried Jack Northrop's 
name.  

The first one of these companies ("Northrop I") had been founded by 
Jack Northrop in 1927, initially under the name of the Avion 
Corporation.  For the first couple of years as head of the 
California-based Avion Corp., Jack Northrop spent his time 
experimenting with ideas for all-metal construction and for 
flying-wing designs.  Unfortunately for the bottom line, nothing 
actually got built or sold by Avion in the first two years of its 
existence, and economic reality eventually made itself felt.  Lacking 
sufficient capital to carry on by itself, the Avion Corporation was 
absorbed in 1929 by the United Aircraft and Transport Corporation, and 
operated until 1931 as the Northrop Aircraft Corporation, a division 
of UA&T Corp.  During this period, Northrop built the Alpha (a 
single-engined passenger- and mail-carrying aircraft) and the Beta (a 
two-seat sports aircraft).  

In 1931, UA&T consolidated its two subsidiaries--Northrop Aircraft 
Corp and Stearman Aircraft--into a single unit and moved everything to 
Wichita, Kansas.  Jack Northrop was a dyed-in-the-wool Californian, 
and found the prospect of facing Kansas winters unpalatable.  
Consequently, he left UA&T and tried once again to establish another 
California-based aircraft company.  He got together with his old 
friend and former employer, Donald Douglas, to found the Northrop 
Corporation ("Northrop II"), with Douglas retaining 51 percent of the 
stock and Jack being named as its president.  The main factory was 
located at El Segundo, California, ensuring that Jack could remain 
living in the state that he loved.  The Northrop Corporation was 
responsible for the famous Gamma and Delta commercial monoplanes which 
were so successful during the 1930s.  The Northrop Corporation was 
also responsible for the 3A monoplane fighter of 1935 and for the A-17 
attack plane of 1935/36.  Northrop was also responsible for the BT-1 
attack bomber, which was to evolve into the famous SBD Dauntless of 
World War II fame.  

However, the Northrop Corporation began to experience some serious 
labor strife in the late 1930s.  The labor problems eventually got so 
bad that the Army refused to accept any further deliveries of A-17 
attack planes until they were corrected.  In an attempt to correct the 
labor problems, on April 5, 1937, Douglas decided to acquire the rest 
of the stock of the Northrop Corporation.  Continued labor 
difficulties forced Douglas to dissolve the Northrop Corporation 
altogether on September 8, 1937.  It was immediately reformed under 
the direct aegis of Douglas, the name of the company changing to the 
El Segundo Division of Douglas.  

By 1939, the Northrop Corporation had become just another division of 
Douglas Aircraft, and Jack Northrop went out on his own for a third 
time to found yet another California-based aircraft company bearing 
his name, this one named Northrop Aircraft Inc.  of Hawthorne, 
California ("Northrop III"), the forerunner of today's Northrop 
Corporation, the maker of the B-2 stealth bomber.  

The Northrop XP-56 was the first USAAF fighter aircraft to be built by 
"Northrop III".  The Northrop XP-56, like the Bell XP-52, the Vultee 
XP-54, and the Curtiss XP-55, was evolved as a response to Circular 
Proposal R-40C, which was issued on November 27, 1939.  It called for 
a fighter that would be much more effective than any extant--with a 
top speed, rate of climb, maneuverability, armament, and pilot 
visibility, all of which would be far superior to those of any 
existing fighter.  In addition, the fighter was required to have a low 
initial cost and had to be easy and inexpensive to maintain.  The Army 
specifically mentioned in R-40C that they would consider aircraft with 
unconventional configurations.  

The Northrop entry, designated N2B by the company, was nothing if it 
was not unconventional.  It was a unique tailless interceptor made 
entirely of magnesium.  The N2B was a swept-wing tailless flying-wing 
aircraft with no forward-mounted elevators.  Northrop proposed to use 
the new and untried Pratt & Whitney X-1800-A3G (H-2600) liquid-cooled 
engine, mounted behind the pilot's cockpit and driving a pair of 
contrarotating pusher propeller.  

Jack Northrop had actually been thinking about flying wing aircraft as 
far back as 1929 when he was with the Avion Corporation.  In 1939, 
Northrop had, in fact, built a full-scale flying testbed to explore 
the possibility of all-wing designs.  Designated N1M by the company, 
the flying testbed was powered by a pair of Lycoming engines driving 
pusher propellers.  The N1M has survived to the present day and is in 
storage at the Paul Garber facility in Suitland, Maryland.  I saw it 
there in November of 1992.  It seems to be in pretty good shape.  

On June 22, 1940, Northrop Aircraft, Inc.  received a contract for 
preliminary engineering data and a powered wind tunnel model.  The 
designation P-56 was reserved for the project.  On September 26th, 
1940, a single prototype was ordered as the XP-56.  The serial number 
was 41-786.  

However, shortly after development of the XP-56 began, Pratt & Whitney 
abandoned all work on its X-1800 liquid-cooled engine.  This left the 
XP-56 (and the competing XP-54 and XP-55 along with it) out on a limb, 
without an engine.  Northrop's design team reluctantly decided to 
switch to the less-suitable Pratt & Whitney R-2800 air-cooled radial 
engine.  Although the R-2800 engine was more powerful (2000 hp as 
opposed to 1800 hp), it was also wider.  The larger diameter of the 
radial engine required in turn that the fuselage be widened in order 
to accommodate it.  These changes resulted in an increase in the 
weight.  

The fuselage was stubby and rounded, with an unpressurized cockpit 
situated well forward.  The plane had a short and stubby dorsal fin 
and a very large ventral fin, so large, in fact, that it very nearly 
scraped on the ground when the aircraft stood on its landing gear.  
The cantilever mid-mounted wing had elevons which functioned both as 
ailerons and wingflaps mounted on the trailing edge of the drooping 
wing tip.  Air ducts for cooling of the radial engine were located on 
the wing leading edge.  The mainwheels retracted into the wing, and 
the nosewheel retracted into the fuselage.  Proposed armament was to 
be two 20-mm cannon and four 0.50-inch machine guns, all mounted in 
the nose.  

On February 13, 1942, a USAAF contract was issued for a second XP-56 
prototype.  The serial number was 42-38353.  The name *Black Bullet* 
has been attached to the project, but I don't know if this name was 
official.  

The first XP-56 (41-786) was ready in April of 1943.  It was shipped 
out to Muroc Dry Lake (later Edwards AFB) for tests.  During initial 
ground handling trials, it was found that the aircraft tended to yaw 
sharply and dangerously while taxiing at high speeds.  It was thought 
that this problem was caused by faulty wheel brakes, and trials were 
halted until the aircraft was re-equipped with manual hydraulic 
brakes.  This delayed the first flight until September 30, 1943, when 
test pilot John Myers took the XP-56 into the air for the first time.  
An altitude of five feet was maintained, and the XP-56 appeared to fly 
normally.  Several additional flights were undertaken, during which 
somewhat greater altitudes were attained.  These test flights were not 
particularly encouraging.  Nose-heaviness was a persistent problem, 
and lateral control was difficult to maintain in all flight regimes.  
However, before any of these aerodynamic problems could be addressed, 
the port mainwheel tire blew out during a high-speed taxiing run and 
the aircraft somersaulted over onto its back.  It was totally wrecked.  

In an attempt to correct the deficiencies encountered with the first 
XP-56, the second XP-56 (42-38353) underwent some major changes.  The 
center of gravity was moved further forward.  There was a major 
increase in the size of the upper vertical surface--it was enlarged 
from a mere stub into a surface larger in area than the ventral fin.  
A new form of rudder control was fitted which made use of air bellows 
at the wing tips which operated a set of split flaps for directional 
control.  The control of the bellows was achieved by valving air to or 
from the bellows by means of wingtip venturis.  

On March 23, 1944, test pilot Harry Crosby took the second XP-56 up 
for the first time.  However, Crosby found it impossible to lift the 
nosewheel off the ground at speeds below 160 mph, and the test flight 
lasted only a few minutes.  The second flight went better, and it was 
found that the nose heaviness went away after the landing gear was 
retracted.  However, the aircraft was severely underpowered for its 
weight, and only relatively low speeds could be attained, much less 
than the projected maximum speed of 465 mph at 25,000 feet.  

On May 39, 1944, it was decided that NACA would use their wind tunnel 
at Moffett Field, California to look into the causes of the XP-56s low 
performance.  However, the higher priority of other projects led to 
postponement of the XP-56 wind tunnel tests until late October of 
1944.  

While awaiting the beginning of the wind tunnel testing, further 
flight test trials were undertaken with the XP-56.  On the tenth test 
flight, the pilot complained of extreme tail heaviness on the ground, 
low power, and excessive fuel consumption.  After consultations, it 
was concluded that the XP-56 was basically not airworthy , and that it 
was just too dangerous to continue flight tests with it.  Shortly 
thereafter, the whole project was abandoned.  The further development 
of higher-performance piston-engined fighters was futile in any case, 
since the advent of jet propulsion would soon bring the era of 
propeller-driven fighters to a close.  

Although the XP-56 project was a failure, it was not a total loss for 
Northrop, since the company had learned a lot about flying wing 
designs.  This data gained during the XP-56 project was put to good 
use in later Northrop designs such as the XB-35 piston- engined 
bomber, the YB-49 jet-powered bomber, and the B-2 stealth bomber.  

Specs of the XP-56: 

One 2000 hp Pratt & Whitney R-2800-29 eighteen-cylinder air-cooled 
radial engine.  Proposed armament was to be two 20-mm cannon and four 
0.50-inch machine guns, all mounted in the nose.  No armament was, in 
fact, ever actually fitted.  In view of the limited flight testing of 
the XP-56, the following performance figures are based on 
manufacturer's estimates and were never achieved during actual tests.  
Maximum speed 465 mph at 25,000 feet, 417 mph at sea level.  Climb 
rate of 3125 feet per minute at 15,000 feet.  Climb to 20,000 feet in 
7.2 minutes.  Normal range 445 miles at 396 mph.  Maximum range 660 
miles.  Service ceiling 33,000 feet.  Weights were 8700 pounds empty, 
11,350 pounds normal loaded, and 12,145 pounds maximum.  Dimensions 
(second prototype) were wingspan 42 feet 6 inches, length 27 feet 6 
inches, height 11 feet, wing area 306 square feet.  The length of the 
first prototype was 23 feet 6 inches and the height was 9 feet 8 
inches.  

Sources: 

  The American Fighter, Enzo Angelucci and Peter Bowers, Orion, 1987.  

  War Planes of the Second World War, Fighters, Volume Four, William 
  Green, 1964.  

Joe Baugher       AT&T Bell Laboratories    2000 North Naperville Road 
		  Naperville, Illinois 60566-7033.   (708) 713-4548