Subject: Number 107 in the Series--North American F-107

From: [email-masked]
Date: 28 Feb 94 17:20:11 GMT

>From [email-masked]

The North American F-107 was a more powerful, higher-performance 
version of the F-100 Super Sabre.  In fact, it began its life under 
the designation F-100B and was originally intended to be the follow-on 
to the F-100A.  It was initially envisaged as a faster version of the 
F-100A day fighter, optimized to take maximum advantage of the power 
offered by the J57 jet engine.  It eventually evolved into a 
fighter-bomber aircraft and found itself in direct competition with 
the Republic F-105 Thunderchief.  

The F-100B project began in 1953 in response to an Air Force request 
for an improved F-100A.  On March 4, 1952, North American Aviation 
management asked their design team for an estimate of engineering 
requirements for the F-100B.  The F-100B retained the original swept 
wing planform of the F-100A but had a thinner wing cross section with 
a 5 percent thickness/chord ratio rather than the 7 percent of the 
F-100A.  An upgraded J57 engine was provided, and the aircraft was to 
be fitted with a variable-area inlet duct and a convergent-divergent 
exhaust nozzle.  Total thrust of this new engine was to be 16,000 
pounds.  Dual landing-gear wheels were to be provided which would make 
operations from unprepared airfields possible.  The fuselage was to be 
area-ruled and was to have an increased fineness ratio.  The fuel load 
was to be carried in integral wing tanks, no provisions being made for 
the carrying of external fuel tanks.  The F-100B was to expected to be 
approximately the same size and weight as the F-100A, and with the 
increased power and the aerodynamic refinements that would be made 
available, a maximum speed of Mach 1.80 at high altitude was 
anticipated.  Production was expected to begin in 1955.  

At the same time, North American began to study the feasibility of 
adapting the Super Sabre as an all-weather interceptor.  The project 
became known as the "F-100I" (I for *Interceptor*) or "F-100BI", 
although these designations were not official USAF designations.  This 
aircraft was similar in overall configuration to the F-100B except 
that it had a modified cockpit and was fitted with a nose radome.  In 
order to accommodate the radome, the forward fuselage had to be 
redesigned so that it had an undernose variable-area air intake.  
Provision were made for underwing drop tanks, and the wing leading 
edges were to be heated to prevent icing.  An all-rocket armament was 
to be fitted.  The F-100BI was intended to bear much the the same 
relation to the F-100A as the F-86D did to the F-86A.  

On October 20, 1953, the factory designation NA-212 was assigned to 
the project.  Work began on wind-tunnel studies and a detailed cockpit 
mockup was built.  Work was started on a full aircraft mockup.  

In November of 1953, North American started to give some consideration 
to adapting the NA-212 to a fighter-bomber role.  Six hardpoints were 
added underneath the wing, and the wing structure, controls, and 
cockpit were revised accordingly.  Single-point refuelling capability 
was provided and the windshield and canopy were revised to improve the 
pilot's view.  A retractable tailskid was installed and the flight 
control system was upgraded by the addition of pitch and yaw dampers.  

Neither the F-100B nor the F-100BI attracted all that much interest on 
the part of the Air Force.  Consequently, on January 15, 1954, the 
program was cut back drastically at the request of NAA president Lee 
Atwood.  Plans to undertake full production were abandoned, and the 
program was scaled back to a comprehensive engineering study.  

On April 16, NAA decided to settle on the general configuration of the 
F-100B as being basically that of the F-100BI interceptor.  However, 
later that month, NAA learned that the Air Force was interested in the 
fighter-bomber configuration of the NA-212.  On May 16, 1954, North 
American directed that all work on the F-100B interceptor project be 
terminated and that all efforts now be concentrated on the 
fighter-bomber adaptation.  The nose radome and the chin intake of the 
interceptor version were, however, to be retained.  

In the meantime, NAA engineers had discovered that low-speed handling 
properties could be improved and landing speeds lowered by about 30 
mph if an inboard blown flap were used for boundary layer control.  
These were incorporated into the design at an early stage.  The F-100A 
had been designed without any wing flaps at all.  

Among the changes needed to adapt the F-100B as a fighter-bomber was 
the change from a 7.33 to an 8.67 load factor, the installation of a 
maneuvering autopilot, the mounting of an AN/APW-11A radar beacon, a 
Low-Altitude Bombing System (LABS), an AN/ALF-2 chaff dispenser, an 
AN/APS-54 radar warning system, a plotting board and a cockpit 
computer.  Larger and heavier wheels and brakes had to be designed, 
and provision had to be made for electric fuseing of external stores.  

On June 11, 1954, the USAF authorized a contract for 33 F-100B fighter 
bombers.  On July 8, 1954, the Air Force notified NAA that the 
designation for the project had been officially changed to F-107A, the 
USAF concluding that since this aircraft was so vastly different from 
the original F-100A it deserved a completely new fighter designation.  

Late in 1954, the Air Force issued General Operational Requirement 68, 
calling for a tactical fighter-bomber and an air-superiority day and 
night fighter.  North American apparently responded to this 
requirement, but it is not quite sure how the F-107A fits into GOR-68.  
In any case, work continued on the F-107A at a feverish pace.  In the 
meantime, Pratt & Whitney had developed the J75 turbojet, a newer and 
more powerful adaptation of the J57.  NAA enthusiastically embraced 
this engine as the powerplant for the F-107A.  

North American engineers redesigned the vertical tail of the F-107A 
fighter-bomber as a single-piece, all-moving slab.  A similar 
innovation was adopted for the North American A3J (later A-5) 
Vigilante carrier-based strategic bomber.  A complex 
spoiler-slot-deflector system on the wings provided lateral control.  
The major offensive load was to consist of a nuclear weapon carried 
semi-submerged in the fuselage belly on the centerline.  

Unfortunately, wind tunnel tests showed that there would be major 
problems with weapon release and separation caused by airflow 
interference from the nose radome and chin air intake.  In order to 
correct this problem, it was decided to move the air intake from the 
nose to the top of the fuselage just behind the cockpit.  

The first F-107A (serial number 55-5118) took off on its maiden flight 
on September 10, 1956 at Edwards AFB, with NAA test pilot Bob Baker at 
the controls.  It went supersonic on its first flight, although there 
was some minor damage upon landing when the drag chute malfunctioned 
and the aircraft overran the end of the concrete runway and ended up 
in a ditch.  The aircraft was quickly repaired and flew again three 
days later.  

A variable air inlet duct was installed on the third prototype 
(55-5120).  The variable-geometry duct did not live up to its 
expectations.  In spite of repeated attempts at steady climbs at 
subsonic or supersonic speeds and even zoom climbs from maximum speed 
at 35,000 feet, 55-5120 was never able to get above 51,000 feet.  This 
was blamed on problems with the variable-geometry intake duct and with 
the J75 engine, both of which were relatively new at the time.  In 
addition, there was an annoying "buzz" in the variable air intake at 
high speeds, which was traced to instability of the airflow at the 
inlet.  

The F-107A found itself in direct competition with the Republic F-105 
Thunderchief for production orders.  In 1957, the USAF decided to go 
with the F-105, and the F-107 was relegated to aerodynamic testing 
duties.  The first and third F-107As were turned over to NACA for high 
speed flight testing work.  

The first F-107A (55-5118) reached NACA at Dryden on November 6, 1957.  
It was given the NACA number of 207.  However, it was so mechanically 
unreliable that it was grounded by NACA after only four flights and 
was scavenged for spare parts to keep the other one flying.  

The third F-107A (55-5120) reached NACA at Dryden in February of 1958.  
The flight testing of the variable geometry intake of the aircraft was 
cut short because of its mechanical problems.  Eventually, NACA gave 
up on the F-107A's variable-geometry inlet altogether and it was bolted
fixed in position, limiting top speed to Mach 1.2.  55-5120 completed 
some forty test flights for NACA/NASA during 1958-59.  On the basis of 
F-107 flight testing, North American refined the design of the 
side-stick planned for the X-15.  55-5120 was damaged on September 1, 
1959 when test pilot Scott Crossfield was forced to abort a takeoff 
because of control problems.  Both tires blew and the left brake burst 
into flames.  Crossfield was uninjured, but the resulting damage to 
the F-107A was deemed to be too severe for economical repair, and NASA 
decided to scrap the aircraft.  

The other two F-107As still survive.  After being retired by NASA, 
F-107A number 55-5118 was turned over to the Pima Air Museum in 
Tucson, Arizona, where it is now on display.  F107A number 55-5119 is 
in the Air Force Museum at Wright-Patterson AFB in Ohio.  

Specification of the YF-107A: 

One Pratt & Whitney YJ75-P-9, 17,200 lb.s.t. dry and 24,500 lb.s.t.  
with afterburning.  Maximum speed: 890 mph at sea level, 1295 mph at 
36,000 feet.  Initial climb rate: 39,900 feet per minute.  Service 
ceiling 53,200 feet.  Normal range 788 miles, maximum range 2428 
miles.  Dimensions were wingspan 36 feet 7 inches, length 61 feet 10 
inches, height 19 feet 8 inches, wing area 376 square feet.  Weights 
were 22,696 pounds empty, 39,755 pounds gross, 41,537 pounds maximum 
takeoff.  Armament was to consist of four 20-mm cannon, plus six 
underwing hardpoints for stores.  A centerline position was provided 
for a recessed store.  

Sources: 

  North American F-100 Super Sabre, David A. Anderton, Osprey, 1987 

  The North American F-100 Super Sabre, Ray Wagner, Aircraft in Profile, 
  1965.  

  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.  

  Flying the Frontiers: NACA and NASA Experimental Aircraft, Arthur 
  Pearcy, Naval Institute Press, 1993.  

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