Subject: Number Ninety-Eight in the Series--Hughes XF-98 Falcon

From: [email-masked]
Date: 18 Oct 93 16:39:37 GMT

>From [email-masked]

In 1947, the designation XF-98 was assigned to an "unmanned fighter" 
project that was eventually to result in the Hughes Falcon, the 
world's first operational air-to-air guided missile.  [ Question:
were there any operational tests of German air-to-air missiles during
World War 2?] 

In 1947, the USAAF asked for bids on a new type of aircraft armament 
system.  Two separate projects were to be undertaken--the first was to 
explore the use of a radar-based airborne fire-control system for 
manned interceptors and the second was to develop a guided air-to-air 
missile to be carried by later generations of manned interceptors.  
Both packages were won by the Hughes Aircraft Corporation of Culver 
City, California.  

The air-to-air missile component of the system was given the 
designation XF-98, a fighter designation.  It was assigned the name 
*Falcon*.  However, The USAF had second thoughts about giving an 
unmanned guided missile a fighter designation, and in 1950, the Hughes 
Falcon air-to-air missile was redesignated GAR-1, the GAR standing for 
*Guided Aircraft Rocket*.  

The Falcon initially operated on the principle of semi-active radar 
homing, that is, it tracked and homed in on a radar echo reflected 
back from a target illuminated by a radar set carried in the aircraft 
that launched the missile.  The missile did not carry its own radar 
transmitter.  

The Falcon entered production at a new Hughes plant in Tucson in 1954.  
The airframe was about the size of a person, and the missile was 
powered by a Thiokol solid-fuel rocket motor.  It had a hemispherical 
nose radome flanked by receiving aerials that looked like small nose 
fins.  These antennae gave proportional navigation and steering 
signals to the elevons mounted on the trailing edges of the four delta 
wings.  The length was 1.97 meters (6.48 feet), the diameter was 16.3 
cm (6.4 inches), and the wingspan was 50.8 cm (20 inches).  It carried 
a 29-pound high-explosive warhead that was detonated by a proximity 
fuse.  The launch weight was about 110 pounds.  Maximum speed at 
engine burnout was Mach 2.8, and effective range was about five miles.  

The first Falcon installations were on the wingtip pods of F-89H and J 
Scorpion interceptors.  At about the same time, the Convair F-102A 
Delta Dagger interceptor entered service with six Falcons housed 
inside the internal weapons bay.  Both aircraft entered service with 
the Air Defense Command in 1956.  

In late 1956, the first infrared Falcon appeared, the GAR-2.  The 
radar receiver of the GAR-1 was replaced by a passive infrared 
detector housed behind a glass nose.  This missile homed in on the 
infrared radiation emitted by the hot engine exhaust of the enemy 
aircraft.  The infrared Falcon had the advantage in that it was "fire 
and forget", enabling the launching aircraft to break away as soon as 
the missile was fired.  However, interceptor aircraft typically 
carried a mix of both radar and infrared Falcons, and it was common 
doctrine to launch one missile of each type at an enemy target in 
order to ensure a kill.  

The GAR-1D was an improved version of the radar Falcon, with the 
control surfaces being made larger and moved to a position well behind 
the delta wings.  

The GAR-2A was an improved version of the infrared Falcon with a 
better infrared detector.  The GAR-2A was built for export under the 
designation HM-58, and was built under license by SAAB-Scania of 
Sweden as the RB-28.  

The GAR-3 Falcon of 1958 was a vastly-improved version of the radar 
Falcon with a longer-during rocket motor, an improved radar receiver 
mounted behind a more pointed nose, long wing-root fillets, and a 
larger warhead.  Maximum speed was about Mach 4, and effective range 
was about 7 miles.  

The GAR-3A radar homer of 1959 had a new motor having boost/sustainer 
charges, improved radar homing guidance, provision for electronic 
countermeasures, and some changes in the airframe.  

The GAR-4A was the infrared homing version of the GAR-3.  It contained 
a new infrared seeker capable of locking on to smaller targets at 
greater ranges.  

The GAR-11 Nuclear Falcon of 1960 was designed to give a better PSSK 
(Probability of Single-Shot Kill) in head-on attacks.  Infrared homing 
was considered to be ineffective in head-on encounters, and since 
semi-active radar homing was less precise, it was decided that the 
best option was to increase the yield of the warhead.  A nuclear 
warhead similar to that of the Genie was carried, triggered by four 
active-radar proximity fuse aerials mounted flush with the body ahead 
of the wings.  The diameter was 11 inches, and the launch weight was 
203 pounds.  

The GAR-11A was similar to the GAR-11, but it carried a conventional 
high-explosive warhead.  This version was exported as HM-55 and was 
built under license by SAAB-Scania of Sweden as RB-27.  

The GAR-9 was a fourth-generation Falcon designed for the North 
American F-108 Rapier interceptor.  Following launch, the ASG-18 radar 
of the F-108 was to be used for mid-course guidance and target 
illumination, and an infrared sensor was to be used for terminal 
homing.  Propulsion was to be by a Lockheed-developed storable 
liquid-fueled rocket.  Mach 6 performance was envisaged, and ranges of 
up to 115 miles were anticipated.  Following the cancellation of the 
F-108 project in 1959, work on the GAR-9 missile project was 
transferred to the Lockheed F-12 project.  The F-12 project was itself 
terminated after only four aircraft were built, leaving the GAR-9 with 
no launching aircraft.  

In 1962, the GAR-1, 2, 3, and 4 Falcon missiles were redesignated 
AIM-4, where the AIM stood for "Airborne Interception Missile".  The 
GAR-11 was redesignated AIM-26 and the GAR-9 was redesignated AIM-47.  
The various Falcon redesignations are summarized as follows: 

GAR-1 -> AIM-4 
GAR-1D -> AIM-4A 
GAR-2 -> AIM-4B 
GAR-2A -> AIM-4C 
GAR-2B -> AIM-4D 
GAR-3 -> AIM-4E 
GAR-3A -> AIM-4F 
GAR-4A -> AIM-4G 
GAR-11 -> AIM-26A 
GAR-11A -> AIM-26B 
GAR-9 -> AIM-47A 

The AIM-4D was the final production version of the Falcon, It was 
specifically designed for air-to-air combat, all previous Falcons 
having been designed for the interception and destruction of enemy 
bombers.  It combined the small airframe of the earlier Falcons with 
the more powerful rocket motor and more sophisticated infrared seeker 
of the AIM-4G.  Numerous AIM-4As and Cs were remanufactured to the 
AIM-4C standard.  

I remember reading that the Falcon missile proved to be a dismal failure
when used in Vietnam, and that it was quickly withdrawn from service.
Details, anyone?

Source: 

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

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