Already in 1951, a mere half decade after Chuck Yeager first broke
the sound barrier in his
Bell X-1, the world was gearing up for the new reality of supersonic
warfare. Air superiority as a significant tactical advantage on
the battlefield was well-established during World War II, itself
only half a decade in the past at the time this article in a 1951
edition of Air Trails. The learning curve was steep but
the progress fast on how to build and fly aircraft operating beyond
Mach 1. Crazy phenomena like aileron control reversal came
as a surprise to engineers and pilots on the bleeding edge of that
technology, and were major issues that need to be dealt with and
mitigate. Here is a wee bit of early history on the supersonic warplane
By R. G. Naugle
We have a new breed of fighters coming out - and going up - supersonic
interceptors! These fast-climbing, sky-rocketing meteorites will
flash through the midnight sky in short bursts of supersonic speed
to slash and tear at high-flying enemy bombers. Fleets of reserve
craft will stand by on the alert, crouching on airport ramps ready
to scream off in near-vertical climbs.
The U.S. is developing a new breed of interceptor to
deal with high-flying enemy bombers that may try to attack
We've never had interceptors before. They're purely defensive
weapons and we've never needed them. We've always carried the fight
to the enemy's homeland with bombers and general-purpose fighters
modified to do the particular job. Some carried drop tanks and escorted
bombers over long distances, and then fought off the enemy's defending
interceptors over the target. Others, operating by themselves, carried
a small arsenal of rocket projectiles, cannon and guns on tactical
strikes to break up the enemy's ground defenses, transportation
and communication systems.
We still need such fighters - penetration fighters, as they are
now called. But modern war, like modern football, requires two teams,
offensive and defensive. One team to score on the enemy, another
to prevent him from scoring on you. We must still have penetration
fighters, but we now need and will soon build a huge fleet of East,
goal-line defending supersonic interceptors to prevent enemy touchdowns
on the North American continent.
Speed and ceiling of bombers now equal those of fighters since
both, in the practical sense, are held back by the sonic barrier.
For example, the F-86 and B-47 are not only similar in general design
but both have about the same top speed and maximum altitude capabilities.
Both fighter and bomber can now closely approach the speed of sound
with their thin sweptback wings and jet power, and both can achieve
stratospheric altitudes undreamed of during World War II. And herein
lies the rub - for fighters must chase, catch and shoot down bombers.
This means we must have supersonic interceptors, for not only
must they fly faster than the speed of sound to overtake fast modern
bombers, but they must also do so in order to regain their maneuverability
at extreme altitudes! This is not generally appreciated. But a simple
chart shows it quite clearly.
It is the chart of speed versus altitude that positively defines
the limits any subsonic airplane must fly within. We know that an
airplane must fly so fast to stay in the air - the normal low-speed
stall. On the other hand, a subsonic airplane cannot fly faster
than its critical Mach number - some fraction of the speed of sound.
"Buffeting" occurs in both cases, a breakdown of airflow over the
wings and the sudden loss of lift. Therefore these limiting speeds
are called the "buffet boundaries." If these speeds remained the
same at all altitudes a plane could fly as fast and have the same
maneuverability at high altitudes as it does near the ground. But
they do not remain the same.
The stalling speed tends to increase with altitude while the
critical Mach speed tends to decrease with altitude - thus squeezing
the flyable speed range together until, at some altitude, the stalling
speed equals the critical Mach speed. The altitude at which this
occurs is sometimes called the "altitude barrier" since an airplane
cannot fly any higher than this. The airframe as a heavier-than-air
machine can no longer support itself in the air and fly as an airplane
above this point. Power is not a factor. While considerable power
is required for a plane to approach its altitude barrier, more power
will not allow it to go any higher.
We see immediately how maneuverability is affected. The speed
range at any altitude - that is, the gap between the stalling speed
and the critical Mach speed - defines the maneuverability, the tightness
of turns, the number of G's that can be pulled in maneuvers; and
it is maneuverability that counts in fighter attacks. This then
is the graphic picture all subsonic aircraft are confronted with,
and we can see pictorially how both the B-36 and the B-47 baffle
The B-47 rides along the critical Mach speed line and challenges
any subsonic fighter to catch him. The B-36 flies slower - but it
goes higher, up into the corner near the altitude barrier and sits
there - forcing the fighter to come on up and fight him on his own
terms. The B-36's maneuverability is gone, but what is more important,
so is that of the attacking fighter. Only if the fighter can fly
at supersonic speed can he catch the fast B-47 type bomber; only
if he flies supersonic can he increase his speed-range and regain
his maneuverability at extreme altitudes to attack B-36 type bombers.
The present-day interceptor, like the F-94C shown here,
is only a stepping stone toward the full-fledged bomber-killer,
agile at stratospheric heights and deadly with its rockets
and electronic sights.
Let's see how this picture looked to Group Captain "Car's Eves"
John Cunningham, Chief Test Pilot of the de Havilland Aircraft Co.
of England, when he set his world's altitude record of 59,492 ft.
in a specially modified stripped-down Ghost-powered de Havilland
Vampire. (Each wing-tip had 8 ft. extensions.) At 59,000 ft. he
could only fly at speeds between 125 mph indicated (about 400 mph
true) and 150 mph indicated (about 465 mph true). If he flew slower
than 125 indicated, he'd stall. If he flew faster than 150 indicated,
he'd exceed his critical Mach number. He was sitting close to his
altitude barrier and didn't have quite enough power to reach it
- where theoretically, he could fly at only one speed. As it was,
he could only pull a theoretical 1.4 G maneuver, a gentle turn.
The slightest over-control would cause him to stall out.
Cunningham couldn't possibly have fought that day. Had a bomber
been sitting at 59,000 ft., Cunningham himself would have been shot
down from the more stable gun-platform on the bomber, able to train
its guns on him at will. For we must remember that up to now fighters
must point to where they shoot - and this means maneuvering.
This instance then, shows why interceptors, the goal-line defenders
of our cities, must be supersonic craft. For when they smash through
the sonic barrier, they not only smash through the altitude barrier
as well, but regain their original low altitude maneuverability.
They can thus successfully chase, catch and attack the bomber and
force him to fight his way through to the target.
Our "90" series of penetration fighters approach in performance
what interceptors must do. The sweptwing Lockheed F-90, for example,
with, afterburner added to its two Westinghouse 3,000 lb. axial-flow
J-34 engines, is reported to be able to fly supersonically and to
get upstairs - probably within 5 minutes. This 13-ton goliath was
designed for penetrating enemy lines and has the built-in range
to escort bombers. However, with less fuel, it can skyrocket to
altitude at fantastic speeds. The only ready-to-go interceptor we
now have is the straight-wing Lockheed F-94-similar in appearance
to the two-seat TF-80C trainer. The nose is extended to pack in
the required radar gear and an afterburner is added to the J-33
engine to shoot it into the stratosphere in a matter of minutes.
However, it is distinctly a subsonic airplane and is intended only
as an interim model until true interceptors can be made available.
Another modified service type is North American's sweptwing F-93A
- a modified F-86 with a Pratt· & Whitney J-48 engine and afterburner
installed. Flush inlets on the side of the fuselage leave the nose
section clear for radar equipment. The '93 therefore vies with the
F-94' as an interim interceptor, but only the prototype is in existence
at the present time.
Several of the "80" fighter model experimental series could also
be used as interceptors. These are the huge 13-ton giants designed
specifically as penetration fighters - fast long-range fighters
for penetration into the enemy's homeland for either bomber escort
or tactical operations against ground defenses. McDonnell's sweptwing
Voodoo F-88 is a rip-roaring fast-climbing meteor powered with two
Westinghouse J-34-W-34 engines. The second prototype and production
models will have afterburners installed, boosting its already impressive
performance considerably. The F-88 is a companion design to Lockheed's
Chart of Indicated Airspeed (AIS) versus Altitude for
various Mach numbers.
Northrup's straight-wing F-89 Scorpion, while originally designed
as an all-weather fighter, carries two jets with afterburners and
is equipped with the necessary radar equipment to spot and chase
high-altitude bombers. Its rate of climb with afterburners undoubtedly
places it within the required 5 minutes to 40,000 ft. category.
It is already in production and being delivered to the Air Force.
We see then that only those fighters with afterburners can be
classed as interceptors. True interceptors, now on the drawing boards,
will probably have rocket motors added as auxiliary sources of power,
since their power is unaffected by altitude. Jet engines, you remember,
lose all their thrust at about 67,000 ft., and at 50,000 ft. have
only about a fifth of their sea-level thrust. That isn't good enough.
The Navy has several fighters with the performance to be classed
as interim interceptors against B-29 type bombers. The Chance-Vought
twin jet F7U-1 Cutlass with afterburners is a standout contender
since, like all carrier borne craft, the wing loading is moderate,
allowing better maneuverability at altitude. McDonnell's twin jet
Banshee is another fighter with better than average high-altitude
performance. However, it is not sweptwing and is without afterburners-both
requirements for high-performance interceptors. It too has a low
wing loading and excellent performance at the 40,000 ft. level.
The true nature of the interceptor emerges. It will have a great
amount of electronic and radar gear aboard, it must be supersonic,
it will probably make its attack from the rear since several attacks
can be made, and it will use small supersonic rocket missiles -
probably with target-seeking devices and proximity fuses. They will
outrange the enemy bomber's rear turret cannons.
Such rockets were used briefly at the very end of the last war.
The Germans had their R.4/M supersonic rocket missiles. They were
unguided, weighed 7 3/4 lbs. when fired, carried 1.1 lbs. of warhead,
and had a maximum velocity of 1,800 ft. per sec. - Mach 2.0 or 1230
mph. Used only during the very last days of the war, six experimental
Me-262's each equipped with 48 such missiles once hit a raiding
party of B-17E's, destroyed fourteen and returned to base without
a single loss. That's the kind of interceptor superiority we must
Such an interceptor must hit 40,000 ft. in less than 5 minutes
and 50,000 in less than 10. It must be capable of going to at least
60,000 ft. with sufficient maneuverability to turn inside a subsonic
bomber. It must have a combat radius of at least 500 miles and carry
complete night-fighting radar equipment. It must have auxiliary
power-auxiliary rocket motors for rapid climb and supersonic speed
at extreme altitude.
And we need them now!
Posted December 7, 2014