History of combat aircrafts :Evolution
of the aircraft wing part – II
… WWII has
ended, and the world has just come out of a turmoil, when another knocks right
on the door. You guessed it right, The Cold War. The power disparity between
the USA and the USSR, had caused the world to split into two halves(not
literally). The imaginary “Iron Curtain” was drawn, and countries East of the
curtained, which agreed to the Warsaw pact, became a part of the Soviet Union,
and the countries west of the curtain, which complied with NATO, came under the
Western world. The drawing up of the iron curtain did not cause an open
confrontation, in essence, a full scale war, but each side didn’t want the
other to advance technologically, or create a mishap, which could lead to a
possible nuclear war, as both the sides of the curtain held nuclear weapons.
The same
happened with aircrafts. The aerodynamic and technological innovation, which
was a closely guarded treasure trove, fell into both the Russian and the Allied
hands. These troves included the discovery of high speed flight, swept wings
and a new engine- the jet engine.
One again
war breaks out, in the Korean peninsula and the countries allied with the
United States, took to action on behalf of UN and South Korea. The initial jet
aircrafts operated by the US, UK and UN forces, were equipped with straight
wings, which were common during the early days. This trend was soon replaced
with the swept wing. To the UN forces backed by the US, there awaited an
unpleasant surprise. During the Summer of 1950, American aircrafts encountered
this sleek, shark like jet which scratched over the skies. Its armament, though
small in quantity, could deliver a devastating blow to its opponents. Yes, the
MiG-15. America’s worst fears have come true. The aircraft jad a sweep back
wing of 35°, and could fly at transonic speeds. The deadly armament of 2x23mm and
1x37mm cannons. The Americans have to find a solution to this threat. Enter
the F-86A Sabre.
The F-86A
Sabre, which entered the Korean theatre in Fall of 1950, was the perfect match
for the MiG-15. It was highly powered than the MiG and had 6x0.5in machine
guns, the the MiG was more manoeuvrable at horizontal flight. The first jet vs
jet combat took place during the Korean war.
The Korean
war saw the expanding potential for jet aircrafts, and jet aircrafts started
becoming faster. This increase in speed was attributed to the increase in sweep
of the wing’s angle. A notable example of comparison is the MiG family. MiG-15
had a wing sweep of 35 degrees, MiG-15 had a wing sweep of 45 degrees and
MiG-19 a whopping 55 degrees. As the wing sweep increased, aircrafts could
break the sound barrier more easily.
During the mid
1950s, there emerged another secret to achieve high speed flight, which created
a balance between speed and lift. It was proportional to the Swept wing…
Birth
of the Delta Wing :
Another
discovery in high speed flying by the Nazis was the Delta wing. The wings
resembled a right angled triangle, who’s leading edge sweep could designed as
required. Notable examples of Delta winged fighter aircraft include the F-102
“Delta Dagger”, Mirage III and MiG-21(with the middle and the latter one having
a wing speed of 60° respectively), meanwhile Swept wing still remained mainstay
during the late 1950s and 1960s, such as the Su-7. The British had their own
innovation, the “notched delta”, which was used in the English Electric
Lightning.
While the
delta wing created a balance between speed and lift, it had its own cons.
Aircrafts with highly Swept delta had a higher takeoff/landing speed/stall
speed, due to the smaller lift surface. This indirectly effected on the runway
length. Often these aircraft required long runways and in most cases, ended up
using the whole runway during landings, and large runways became easy targets
for bombers. Hence a new solution was to be discovered.
Variable
sweep wings: The short lived solution:
In the
1970s, the idea of “Variable sweep” emerged within both the sides of the iron
curtain. This new technique enabled the pilot to change the sweep of the
aircraft wings at his/her will. At take offs and landings, the pilot made the
wing straight, so that more lift is generated and the takeoff run is reduced
drastically. For attaining maximum speed, the pilot would sweep the wings
completely backwards, so that airflow becomes smooth along the leading edge and
for ground attack,low speed flying or a manoeuvrable dogfight, at a medium
sweep, so that an optimum balance of speed and drag is created. For example,
MiG-23 pilots would straighten the wings completely upon take off and landing
(15° sweep), a 45° sweep for manoeuvrable flying and a 70° sweep back setting for
high velocity flying. Notable examples include the Soviet MiG-23/27,
British/German Panavia Tornado, American F-111 Aardvark and the F-14 Tomcat. This
alternative increased the aircraft weight and made manufacturing and maintenance
costshigh.
Another
alternative is the lift jet engines, which involved fitting of additional
smaller lift jet engines to conventional delta wing jet aircraft for shortening
takeoff runs, while the landing runs would be shortened with a drogue chute, or
in some cases, such as the SAAB JAS 37 “Viggen”, reverse thrusters.
In the
1970s, there emerged 2 new types of wings, the “Cranked Delta” and the “Cropped
Delta”. Cranked delta had an unusual protrusion towards the wing tips, which had
a diversion from the wings root angle. If the aircraft had a root angle of 60°,
towards the tips, there would be a bifurcation point, which would change the
angle to 45°(just an example). Notable example is the Sukhoi Su-15”Flagon”.
On the contrary, “Cropped Delta” has a cropped wing tip, or in layman’s
language, has the wing tips shortened by cutting off the wing tips. As compared
to a sharp wing tips of a delta wing, these had a flat edge. Examples include MiG-25”Foxbat”
and Boeing F-15 Eagle(which also includes cropped delta of 45°)
1980s
and 1990s: Decades of air superiority :
During the
1980s and 90s, where air superiority and to some extent, multi role flying were
prioritised, the concept of “Tapered Wings” were reintroduced. Tapered
wings weren’t a new discovery, and were used in notable examples such as Northrop
T-38 Talon and Northrop F-5 Freedom Fighter. Tapered wings, also
called as Trapezoidal Wings, have a wider wing rood and a narrowed wing
tip, resembling to the shape of a trapezoid. It has a better aerodynamic
efficiency than a normal wing. Notable modern example is the Boeing F/A-18
Hornet. “Cropped Delta” also became a common phenomenon, as in the
case of General Dynamics F-16 Fighting Falcon.
The Sukhoi
Su-27 and its family also sport a combination of cropped delta and swept wing.
Additional
lift surfaces: Canards, Tail planes, Flaperones and leading edge extensions:
On a typical
aircraft, the three control surfaces, viz-a-viz, ailerons, elevators and
rudders, are often replaced or accompanied by these additional control
surfaces. These include :
Canards: These are small winglets present in
front of the main pair of wings. These can be pitched up and down to control
the Angle of Attack. These are generally considered as a replacement for the
horizontal stabilisers, as in cases of the Eurofighter Typhoon and Dassault
Rafale, but it can complement the existing traditional tailplanes, as in
case of Sukhoi Su-30MKI/MKM. This combination enhances the Angle of Attack.
Flaperones: in modern jets, such as the Eurofighter
Typhoon, the flaps and the ailerons are combined into one surface, called
Flaperones. These are controlled using the Fly by Wiretechnology, so
that maximum can be achieved during manoeuvring.
Tail
Plane: These are
the standard pair of horizontal and a single vertical(sometimes double) wings,
present towards the trailing part of the aircraft. These horizontal stabilisers
enable the aircraft to pitch whereas the vertical stabilizer enables the
aircraft to yaw.
Leading
edge wing extensions: these are flaps which extend and retract according to the aircrafts
Angle of Attack. These are noticeable during the vortex cloud formation on the
wings during high g turns.
Wings
and stealth: wings on a 5th Generation aircraft :
As stealth became
a major component of 5th generation aircrafts, the wing had to be designed
in a way, which can deflect radar waves. Common examples include clipped delta
with stealth coating as in cases of Lockheed Martin F-22 Raptor and Lockheed
Martin F-35 Lightning II. Certain examples, such as Sukhoi Su-57 and
Chengdu J-20”Vigorous Dragon” incorporate a mix of wing types. A new
concept, called the Diamond wing is under development of the upcoming 6th
Generation aircrafts, as seen in the proposed British Aerospace
Engineering prototype.
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