Subject: Number 103 in the Series--Republic XF-103

From: [email-masked]
Date: 13 Dec 93 17:23:39 GMT

>From [email-masked]

The Republic XF-103 had its origin in an early-1949 request by the USAF 
for an advanced interceptor capable of surpassing the speed and 
altitude performance of new Soviet intercontinental bombers that 
American intelligence officials warned would soon be available in 
quantity.  The North American F-86D Sabre, the Northrop F-89 Scorpion, 
and the Lockheed F-94 Starfire were all subsonic aircraft, and were 
deemed to have insufficient growth potential to be able to meet this 
threat.  This project came to be known as the "1954 interceptor", 
after the year that new interceptor would supposedly be entering 
service.  

At that time, the Air Force recognized that the increasing complexity 
of modern weapons made it no longer practical to attempt to develop 
equipment, airframes, electronics, engines, and other components in 
isolation and expect them to work properly when they were put together 
in the final product.  To address this problem, the Air Force 
introduced the "weapons system" concept, in which components of the 
the new interceptor would be integrated with each other from the very 
beginning, making sure that the various systems would be compatible 
with each other when they were incorporated into the final aircraft.  
The project was given the designation WS-201A, where WS stood for 
"Weapons System".  As originally conceived, WS-201A was a weapons 
system consisting of air-to-air guided missiles, all-weather search 
and fire control radar, all housed in an airframe capable of 
supersonic flight.  

The electronics package for the new WS-201A system came first.  
Project MX-1179 was the designation given to that portion of the 
project dedicated to the armament and electronic fire-control system 
of the 1954 Interceptor.  In October of 1950, the Hughes Aircraft 
Company was named the winner of the MX-1179 contract.  The Hughes 
proposal consisted of a MA-1 fire control system acting in conjunction 
with Falcon air-to-air guided missiles.  For a brief time, the Falcon 
missile was known as the F-98.  

The airframe part of the project was designated MX-1554.  Proposals 
for the aircraft were requested by the Air Force on June 18, 1950.  
When the bidding closed in January of 1951, nine proposals had been 
submitted by six different manufacturers.  Republic submitted three 
separate proposals, North American two, and single proposals were made 
by Chance-Vought, Douglas, Lockheed, and Convair.  

On July 2, 1951, the Air Force announced that designs by Convair, 
Lockheed, and Republic had been selected to proceed with preliminary 
development.  All three companies were to proceed with their designs 
all the way to the mockup stage, with the design being deemed most 
promising at that time being awarded a production contract.  Later, 
the USAF deemed it too costly to carry through with three concurrent 
development programs, and it cancelled the Lockheed project in its 
entirety.  The Convair and Republic entries were given the go-ahead to 
proceed.  

The Republic entry bore the company designation of AP-57.  It was a 
development of the AP-44A, a 1948 proposal for an all-weather 
high-altitude defensive fighter.  The AP-57 project called for an 
extremely advanced aircraft capable of achieving a Mach 4 performance 
(2600 mph) at altitudes of up to 80,000 feet.  The AP-57 was to be 
built entirely of titanium, this metal being chosen because of its 
resistance to the aerodynamic heating that would be encountered at the 
high speeds at which the aircraft would be operating.  

This phenomenal performance was to be achieved by the adoption of a a 
dual-cycle propulsion system.  Takeoff and normal cruise were to be 
powered by a Wright XJ67-W-3 turbojet, rated at 15,000 lb.s.t. dry 
and 22,000 lb.s.t. with afterburning.  The XJ67 was a license-built 
version of the Bristol Olympus.  At high speed, the thrust of the 
turbojet was to be augmented by a XRJ55-W-1 ramjet, capable of 
delivering 18,800 pounds of thrust.  A total thrust of 37,000 pounds 
could be achieved at altitude.  The engines were fed by a large intake 
mounted on the ventral fuselage, a geometry which was sure to invite 
foreign object ingestion and damage during takeoff and landing.  

The fuselage was smooth from nose to tail, with no bumps or kinks of 
any kind.  There wasn't even a kink or bump for the pilot's cockpit.  
There was no cockpit canopy to interfere with the air flow, and the 
cockpit was recessed into the fuselage.  For vision, the pilot was 
provided with only two small side windows.  The view ahead was 
provided by the use of a periscope.  In 1955, the periscope concept 
was tested on a specially modified F-84G which was flown on a long 
cross-country flight with the pilot's forward vision blocked.  For 
emergency escape, a downward-ejecting capsule was provided.  

The small wings were of delta configuration, but the Republic design 
was not a true delta, since there was a separate horizontal tailplane 
mounted on the rear fuselage.  A ventral fin was also mounted on the 
rear fuselage, the fin being retracted to the side during takeoffs and 
landings.  

The armament was to have consisted of six Hughes GAR-3 Falcon 
air-to-air missiles housed in flush-mounted individual weapons bays on 
the sides of the fuselage, plus 36 unguided rockets.  The fire-control 
radar was housed in the nose.  The estimated takeoff weight of the 
AP-57 was over 40,000 pounds.  

The Republic AP-57 was clearly a quantum leap ahead in the state of 
the art for the early 1950s.  It would clearly be quite a challenge 
even today.  

The competing Convair entry called for a scaled-up version of its 
XF-92A experimental delta-winged aircraft On September 11, 1951, 
Convair received a contract for this design under the designation 
F-102.  Work on the competing Republic design was also authorized, and 
that aircraft was assigned the designation XF-103.  

A full-scale mockup inspection took place in March of 1953.  Republic 
received a contract for three prototypes in June of 1954.  Work was 
slowed by lots of problems--difficulties encountered in the 
fabrication of the titanium alloy used in the structure, delays with 
the development of the advanced dual-cycle propulsion system, and 
massive cost overruns.  

It was clear that the XF-103 was so far ahead of the state of the art 
that it was much too risky to be a serious contender for the 1954 
Interceptor project.  This made the competing Convair F-102 for all 
practical purposes the winner of the contest, and the Air Force began 
to lose interest in the XF-103.  Continuing delays and cost overruns 
caused the program later to be cut back to only one prototype.  The 
Wright XJ67 engine encountered even more delays and ultimately never 
materialized.  Plans to substitute the Wright J65 turbojet proved to 
be unrealistic.  The Air Force finally threw in the towel on August 
21, 1957, cancelling the entire XF-103 project.  

Specifications of the XF-103: 

One Wright XJ67-W-3 turbojet, rated at 15,000 lb.st. dry and 22,000 
lb.s.t. with afterburning, plus one XRJ55-W-1 ramjet rated at 18,800 
pounds of thrust.  
Maximum speed: 1985 mph at 50,000 feet.  With ramjet power, it was 
estimated that 2600 mph could be achieved.  Initial climb rate was 
19,000 feet per minute.  An altitude of 50,000 feet could be attained 
in 7.1 minutes.  Service ceiling was 69,000 feet.  Normal range was 
245 miles, with maximum range being 1545 miles.  Total internal fuel 
capacity was 2440 US gallons.  Weights were 24,949 pounds empty, 
31,219 pounds combat, 38,505 pounds gross, 42,864 pounds maximum 
takeoff.  Dimensions: wingspan 34 feet 5 inches, length 77 feet 0 
inches, height 16 feet 7 inches, wing area 401 square feet.  Armament 
was to have consisted of six Hughes GAR-3 Falcon air-to-air missiles, 
plus 36 2.75-inch unguided rockets.  

Sources:

  The Illustrated Encyclopedia of Aircraft Armament, Bill Gunston,   
  Orion, 1988.

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

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

  Fighters of the United States Air Force, Robert F. Dorr and
  David Donald, Temple Press Aerospace, 1990.

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

  Post-World War II Fighters, 1945-1973, Marcelle Size Knaack,
  Office of Air Force History, 1986. 

Joe Baugher		AT&T Bell Laboratories   	
2000 North Naperville Road      Naperville, Illinois 60566-7033