Subject: Number One Hundred in the Series-North American F-100 Super Sabre (1 of 12)

From: [email-masked]
Date: 20 Oct 93 16:17:18 GMT

>From [email-masked]

The North American F-100 Super Sabre was the first fighter in the USAF 
active service inventory capable of attaining supersonic performance 
in level flight.  Although it was originally designed strictly for the 
air superiority role, it came into its own as a fighter-bomber, and 
flew many of the early combat missions during the Vietnam War.  

The quest for a supersonic version of the Sabre began in February of 
1949, when Raymond Rice and Edgar Schmued of North American Aviation 
began work on a company-financed design study for an advanced version 
of the Sabre capable of achieving supersonic performance in level 
flight.  This study came up with a proposal for obtaining this 
performance improvement by increasing the wing sweepback of the 
standard F-86 to 45 degrees.  However, wind tunnel studies indicated 
that only a relatively small increase in maximum speed would be 
attained by this change, due to the steep rise in aerodynamic drag 
that takes place as near-sonic speeds are attained.  

Clearly, aerodynamic changes alone would not be sufficient to achieve 
supersonic speeds in level flight.  More power would be needed--a lot 
more power.  To this end, the Allison Divison of General Motors 
offered an upgraded J35 turbojet rated at 9000 lb.st, which nearly 
doubled the thrust of the J47 engine of the F-86.  General Electric 
proposed an advanced version of the J47 rated at 9400 lb.st.  dry and 
13,000 lb.st with afterburning.  

On Sept 14, 1949, NAA decided that they would concentrate their 
efforts on the development of an improved version of the F-86D 
all-weather interceptor with the goal of achieving supersonic 
performance.  It was to be powered by the Advanced J47 proposed by 
General Electric.  A maximum speed of Mach 1.03 at 35,000 feet was 
envisaged.  The "Advanced F-86D" (as the aircraft came to be known) 
had a 45 degree wing sweep and an area-ruled fuselage.  However, the 
USAF rejected this idea, proposing that NAA design a day fighter 
instead.  

North American decided to try and give the USAF what it asked for, and 
responded with a proposal for an "Advanced F-86E", which was to be a 
high-performance day-fighter.  The Advanced F-86E that emerged in 
January of 1951 was similar in many respects to the Advanced F-86D, 
but had a slimmer fuselage and featured a nose air intake without a 
radome on the top.  The USAF rejected this idea as well, but indicated 
that the idea might be reworked into an air-superiority fighter.  

The next proposal was known by the company as the Sabre 45, the "45" 
indicating the angle of wing sweepback.  It combined features of the 
Advanced F-86D and the Advanced F-86E, but was to be powered by the 
new Pratt & Whitney J57-P-1 turbojet, rated at 15,000 lb.st. with 
afterburner.  Maximum speed was estimated at Mach 1.3 (860 mph) at 
35,000 feet and combat radius was 670 miles.  Estimated combat gross 
weight was 23,750 pounds.  Armament was to be a quartet of 20-mm T-130 
cannon.  

The Sabre 45 finally succeeded in attracting the interest of the USAF.  
NAA asked that the USAF purchase two prototypes of the Sabre 45, one 
to be used for aerodynamic testing and the other to be used for 
armament trials.  

In October of 1951, the USAF Council decided to press for the 
development of the Sabre 45 proposal, in spite of some misgivings of 
key development personnel who claimed that the design would be too 
costly and complex for a basic day fighter.  With the Korean War as a 
reminder of the perilous state of USSR/US relations, the Air Force 
Council wanted the Sabre 45 in service in a hurry.  They thought that 
two prototypes were not enough to achieve early operational status and 
recommended that the plane be purchased in quantity and full 
production be initiated even before initial flight testing was 
completed.  This is a high-risk philosophy, one which would give the 
Air Force a new plane in a hurry if everything went as planned, but 
one which would risk the high costs and long delays of a lot of 
in-service modifications should unexpected problems turn up during 
flight testing.  However, considering the pressures of the hot war in 
Korea and the cold war with the Soviet Union, the risk was considered 
worth taking.  On November 1, 1951, the Air Force issued a Letter 
Contract for two Sabre 45 prototypes, plus 110 production aircraft.  

On November 9, the Sabre 45 mockup was inspected.  The Mockup Board 
received more than a hundred configuration change requests, and they 
identified several armament deficiencies and requested a number of 
modifications that would improve the capabilities of the aircraft.  

Work on an F-100A production version was begun under the company 
designation of NA-192 on November 20, 1951.  On December 7, 1951 the 
USAF officially designated the Sabre 45 as the F-100, the first of the 
Century Series of fighters.  The two prototypes were designated YF-100 
by the USAF and NA-180 by the company.  

A Letter Contract for two YF-100 prototypes was issued on January 3, 
1952.  On February 11, 1952, the Air Force issued another Letter 
Contract for 23 production F-100As with Fiscal Year 1952 funds.  

Following the mockup inspection, North American reshaped the fuselage 
with an even higher fineness ratio and provided an extended 
clamshell-type cockpit canopy.  The horizontal tail was moved to a 
position below the chord plane of the wing, in the hope that it would 
keep the tail clear of the wing wake at high angles of attack and 
would help to prevent the dangerous tendency of a swept-wing aircraft 
to pitch up suddenly and violently following a stall.  This sometimes 
deadly phenomenon had come to be known as the "Sabre dance", and had 
been the cause of numerous accidents in the F-86.  YF-86D serial 
number 50-577 was experimentally modified to check out this new 
low-set horizontal tail arrangement.  

On June 23, 1952, the USAF approved the proposed changes, but asked 
NAA to consider the installation of external weapons racks and to 
substitute non-self-sealing tanks for existing bladder tanks to save 
400 pounds of weight.  

During the final design stage, NAA engineers made several changes to 
reduce drag and increase engine thrust.  They changed the air intake 
lip so that it had a sharp edge in order to improve the air flow and 
to deliver higher-energy air to the engine at supersonic speeds.  The 
nose was made nine inches longer.  The thickness/chord ratio of the 
horizontal and vertical tails was decreased to 0.035.  This last 
change was scheduled for production aircraft, but was too late to 
appear on the two prototypes.  These changes were approved on August 
26, 1952.  At that time, the USAF authorized the procurement of 250 
additional F-100As.  

The YF-100 that finally emerged from these design changes was 
sufficiently different from that originally planned that it was 
redesignated YF-100A.  The YF-100A had a wing thickness/chord (t/c) 
ratio of 0.082, as compared to the F-86's 0.10 t/c ratio.  A glove 
airfoil section was added to the wing leading edge which reduced the 
wing t/c ratio still further to 0.07.  The ailerons were mounted 
inboard on the wing rather than near the tips in order to reduce the 
tendency of the wing to twist during aileron deflection at high 
speeds.  The YF-100A was somewhat unusual for its time in that no wing 
flaps were provided.  However, the wing leading edge did have 
five-segment automatic slats that were actuated by aerodynamic forces.  
These slats were intended to increase lift at takeoff, to delay wing 
buffet, to improve lateral control near the stall, and to permit 
tighter turns.  

A retractable speed brake was mounted on the fuselage belly.  The tall 
and narrow vertical fin was swept back, and was provided with a thin 
rudder.  

No fuel tanks were mounted in the wing, all of the internal fuel being 
accommodated inside the fuselage in five non-self-sealing bladder 
tanks having a total capacity of 750 US gallons.  Two underwing drop 
tanks each carrying 275 US gallons could be fitted.  

The mainwheels retracted inwards into the fuselage, and the twin nose 
wheels retracted backwards into the fuselage.  

Heat-resistant titanium was used in the initial design stage, marking 
the first time that this metal had been used in large quantities in an 
airplane.  In fact, North American actually used 80 percent of all the 
titanium produced in the United States until 1954 in the manufacture 
of the Super Sabre.  Titanium is an extremely strong and light metal 
and is more resistant to heat than is aluminum.  However, it is rather 
brittle and difficult to machine, and the extensive use of titanium 
sent the cost of Super Sabre manufacture through the roof.  

The armament was to consist of four T-160 (later M39) cannon, two on 
each side of the fuselage below the cockpit.  Ammunition capacity was 
275 rpg.  An A-4 ranging gunsight was to be fitted which computed the 
lead automatically, aided by ranging information from a radar antenna 
mounted inside the upper nose inlet lip and covered by a flush-mounted 
dielectric panel.  

The engine for the YF-100A was the Pratt & Whitney J57-P-7, rated at 
9220 lb.st. dry and 14,800 lb.st with afterburner.  This engine was, 
however, derated from these numbers and was not tuned up to give its 
full power.  On August 26, 1952, the USAF increased its order to 273 
aircraft, plus one static test example.  

As the first YF-100A was nearing completion, the Air Force recognized 
that two prototypes would not be sufficient for the test program, and 
they decided that the first ten F-100As off the line would be used as 
test aircraft as well.  

The first YF-100A (52-5754) was completed on April 24, 1953.  It was 
moved in high secrecy from the Los Angeles factory out to Edwards AFB.  
Company test pilot George S.  Welch made the maiden flight on May 25, 
1953.  The YF-100A exceeded the speed of sound on its first flight.  

On July 6 the YF-100A achieved a speed of Mach 1.44 in a long dive 
from 51,000 feet.  However, on the early test flights, some problems 
were encountered with rudder flutter.  The installation of hydraulic 
rudder dampers solved this problem.  

USAF test pilots found that the YF-100A outperformed any other 
production fighter in the Air Force, but that there were some serious 
shortcomings that might cause problems upon introduction into service.  
The visibility over the nose was poor during takeoff and landing.  The 
longitudinal stability in high-speed level flight was considered 
inadequate.  The low-speed handling was rather poor, and there was a 
tendency of the YF-100A to yaw and pitch near the stall, the left wing 
dropping uncontrollably.  The climbing rate was too slow without 
afterburner--it took 16 minutes to get to 40,000 feet.  In addition, 
the landing was difficult and the touchdown speed was high.  

Phase II tests were completed by September 15, 1953, at which time the 
YF-100A had made 39 flights tasting a total of 19 hours, 42 minutes.  

The second YF-100A (52-5755) flew on October 14, 1953.  

In order to show off the Super Sabre, the USAF decided to use it to 
break the world's speed record.  At that time, the world speed record 
was held by the Douglas XF4D-1 Skyray which had averaged 753.4 mph for 
two runs in each direction over a three-km straight course.  In order 
to set a new record, the Super Sabre had to top the previous mark by 
at least one percent, which meant that the aircraft had to average at 
least 760.9 mph over the 3-km course.  Lt.Col. Frank K. (Pete) 
Everest was chosen to make the attempt.  On his first try over a 
3-kilometer course laid out over the Salton Sea, Lt.Col. Everest 
flying YF-100A 54-5754 averaged 757.75 mph on the required four runs, 
faster than the Skyray but not one percent faster, so it did not 
count.  It was decided to make another try over a different course, a 
15-kilometer course where the one-percent margin rule would not apply.  
Under the rules of the Federation Aeronautique Internationale (FAI), 
the fastest speed over either course counted as the official world 
speed record.  On October 29, 1953, Lt.Col. Everest averaged 755.149 
mph to set a new official world speed record.  Throughout the entire 
record-breaking run, Lt.Col. Everest kept his YF-100A within 100 feet 
of the ground.  This was the last world speed record set at low 
altitude.  

Serials:

52-5754/5755 	North American YF-100A Super Sabre 

Specificiations of the YF-100A: 

One Pratt & Whitney XJ57-P-7 turbojet, 9500 lb.st. dry and 13,200 
lb.st. with afterburning.  Wingspan 36 feet 7 inches, length 47 feet 
1 1/4 inches, height 16 feet 3 inches, wing area 385 square feet.  
Maximum speed 660 mph at 43,350 feet.  Landing speed 160 mph.  Initial 
climb rate 12,500 feet/minute.  Service ceiling 52,600 feet.  Normal 
range 422 miles, maximum range 1410 miles.  Fuel capacity 1307 US 
gallons.  Weights were 18,135 pounds empty, 24,789 pounds gross.  

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. 

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