Subject: Number 111 in the series--General Dynamics F-111 (6 of 13)

From: [email-masked]
Date: 15 Mar 94 17:19:29 GMT

>From [email-masked]

F-111D was the designation given to a more advanced version of the 
F-111.  It was powered by a pair of Pratt & Whitney TF30-P-9 engines, 
each rated at 12,000 lb.s.t. dry and 18,500 lb.s.t. with 
afterburner.  The aircraft were equipped with Mark II microprocessor 
avionics with improved air-to-air capability.  This system was a first 
generation version of what later came to be known as a "glass" 
cockpit.  

In addition, the F-111D was provided with Triple Plow 2 air intakes, 
which were intended to correct the F-111's seemingly chronic problems 
with compressor stall.  The Triple Plow 2 intakes were mounted four 
inches farther from the airframe in order to improve the boundary 
layer "plow", and the translating cowl was replaced by a series of 
blow-in doors.  These blow-in doors were a set of auxiliary inlets 
which enabled extra airflow to reach the inlet duct during takeoff or 
when the engine is at full power but the aircraft is moving slowly.  
They are normally sealed closed by spring-loaded doors which are 
pushed open by air pressure when additional air flow is needed.  

The Mark II system included 7 major components--an inertial navigation 
set and attack radar built by the Autonetics Division of North 
American Rockwell, an IBM computer system, converter and panels by the 
Kearfott Division of Singer-General Precision, Inc., an AN/AVA-9 
integrated display set by the Norden Division of United Aircraft 
Corporation, a Doppler radar by the Canadian Marconi Company, a 
horizontal situation display by the Astronautics Corporation of 
America, and a stores management set by the Fairchild Hiller 
Corporation.  The main forward-looking attack radar of the F-111D was 
the APQ-130, with MTI, Doppler beam sharpening, and illumination for 
radar-guided AAMs.  

The F-111D was ordered on May 10, 1967.  The first F-111D (68-0085) 
flew on May 15, 1970.  It was equipped with the new P-9 engines but 
did not have a complete Mark II system.  It was delivered to the Air 
Force on June 30, 1970, only one day after the lifting of the F-111 
delivery hold order imposed after the F-111A crash of December 11, 
1969.  

The F-111D went through a rather protracted development cycle before 
it was deemed fit for service.  There were difficulties in integrating 
the various complex electronic components with each other.  The 
Autonetics attack radar needed several improvements in its initial 
design, and the Norden integrated display set required extensive 
changes.  The radar problems required that the radar doppler unit be 
redesigned, which in turn caused interface problems with the Norden 
integrated display set.  By late 1969, the Mark II system was still 
not ready.  By mid-1970, the problems with the Norden integrated 
display set were still not resolved.  Several months of acrimonious 
arguments between Autonetics and Norden followed, Norden claiming that 
the IDS's original specification was beyond the state of the art.  

Development problems with the F-111D's advanced avionics caused so 
many delays that the Air Force decided to acquire the simpler F-111E 
as an interim version.  

It was not until November 1, 1971 that the first F-111D was delivered 
to the 27th TFW at Cannon AFB in New Mexico, the third TAC Wing to 
receive the F-111.  This aircraft was the sixth F-111D produced 
(68-0090).  It was equipped with a full Mark II avionics system, 
featuring one of Norden's early IDS productions.  The initial 
operational capability with the 27th TFW was in September 1972.  
Eventually, the F-111D equipped the 522nd, 523rd, and 524th Squadrons 
of the 27th TFW.  

Throughout the rest of 1972, TAC's few F-111Ds continued to be 
crippled by avionics problems.  The horizontal situation display was 
prone to frequent failures, delivery of field ground equipment was 
late, and depot support was poor.  Operational readiness remained low 
all throughout 1973, and the abort rate of the F-111D was higher than 
that of other F-111s.  It was not until January of 1974 that the 
F-111D was finally declared operationally ready.  

96 F-111Ds were delivered between June 30, 1970 and February 20, 1973.  
The serials were 68-0085/0180.  In 1993, the F-111D remains with the 
27th TFW at Cannon AFB.  

The RF-111D was a proposed but unbuilt reconnaissance version of the 
F-111D with very sophisticated avionics.  The program was abandoned in 
September of 1969 because of lack of funds.  Cheaper RF-111As were to 
be acquired, which were in turn cancelled as well.  

Sources:

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

  General Dynamics Aircraft and their Predecessors, John Wegg, 
  Naval Institute Press, 1990.

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

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

  The World Guide to Combat Planes, William Green, Macdonald, 1966. 

  Modern Air Combat, Bill Gunston and Mike Spick, Crescent Books, 1983.

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

  F-111 Aardvark--USAF's Ultimate Strike Aircraft, Tony Thornborough,
  Osprey Aerospace, 1993.

  F-111 Aardvark, Hans Halberstadt, Specialty Press, 1992.

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