Ilyushin Il-40
Encyclopedia
The Ilyushin Il-40 (NATO reporting name
: Brawny) was a two-seat Soviet
jet-engined
armored ground-attack aircraft. The first prototype flew in 1953 and was very successful except when it fired its guns, as their combustion gasses would disturb the airflow into the engines and cause them to flameout
or hiccup. Remedying this problem took over a year and involved the radical change of moving the engine air intakes all the way to the very front of the aircraft and repositioning the guns from the tip of the nose to the bottom of the fuselage, just behind the nose wheel. For all that the aircraft now resembled a double-barreled shotgun from the front its problems had been cured and it was ordered into production in 1955. But only five production aircraft had been completed before the entire program was canceled in early 1956 when the VVS discarded its close air support doctrine in favor of tactical nuclear weapons on the battlefield.
axial-flow
turbojets rated at 2150 kgf (4,740 lbf) at military power and 2700 kgf (5,952 lbf) with afterburner
. In January 1952 Ilyushin sent this proposal to the government, which was quickly accepted, and he was directed to design and build one prototype.
The Il-40 had wings set low on the fuselage, swept back at an angle of 35°, and a tricycle undercarriage. The two AM-5 engines were in pods adjacent to the fuselage. As was traditional for Ilyushin ground-attack aircraft the core of Il-40's structure was a load-bearing armored shell that protected both crew positions, six fuel tanks and part of the radio and electrical equipment. The thickness of the shell ranged from 3 millimetre in thickness. The armored bulkhead protecting the pilot from the front was 10 mm (0.393700787401575 in) thick. The cockpit
glazing was also bulletproof and the pilot was given an 8 mm (0.31496062992126 in) armored headrest to protect him against shells fired from above and behind. The gunner was protected by armor 4 millimetre thick. The total weight of the armored shell and the bulletproof glass was 1918 kg (4,228.5 lb). Ejection seats were provided for both crewmembers. Three perforated airbrakes
were fitted on the rear fuselage, one on each side and one underneath, to enhance the aircraft's maneuverability during a dive.
The initial armament was six 23 mm (0.905511811023622 in) Nudelman-Rikhter NR-23
autocannon
mounted in the nose, three on each side, each with 150 rounds, with their muzzles protruding into the slipstream
. One NR-23 was mounted in a remotely controlled Il-K10 tail barbette
with 200 rounds. It had a maximum elevation of 55°, a maximum depression of 40° and could traverse 60° to either side. The Il-K10 could traverse at a rate of 42° per second and elevate at a rate of 38° per second. Four small bomb bay
s were fitted in the wings with a maximum capacity of 100 kg (220.5 lb) each. Alternatively four bomb racks could be fitted under the wings that could carry bombs up to 500 kg (1,102.3 lb),82 mm (3.2 in) TRS-82 or 132 mm (5.2 in) TRS-132 rockets, or drop tank
s with a total capacity of 1100 litres (290.6 US gal). The normal bomb load was 400 kg (881.8 lb), but 1000 kg (2,204.6 lb) could be carried at overload. Under overloaded conditions a maximum of twelve TRS-82 or eight TRS-132 rockets could be carried. Two cameras were fitted in the rear fuselage for day and night damage-assessment photos.
First flown on 7 March 1953, flight tests revealed no serious shortcomings in the air. The operational CG
was too far aft, but this was only a minor problem when landing, taking off and taxiing
, especially when coupled with the rather short wheelbase
. The biggest problem proved to be the guns and their effect on the engines. During the first aerial test of the cannons at the end of March 1953 the muzzle flash
temporarily blinded the pilot and both engines flamed out
. The pilot was able to restart the engines and made it back safely, but Sergey Ilyushin immediately started an investigation into the cause of the engine problems. Ground tests with high-speed cameras revealed that none of the muzzle brake
s or blast suppressor
s tested made any difference; the engines would hiccup even if only a single gun fired just five to ten rounds.
A decision was made to replace the six NR-23 guns in the nose with four AM-23 cannon with 225 rounds per gun that had a rate of fire 50% greater than that of the NR-23 and to totally revise the gun installation. The guns were moved to the very tip of the nose in a separate compartment made of heat-resistant steel and provided with a special blast deflector chamber to deflect the blast gasses away from the engine inlets. Two doors were provided at the bottom of the chamber to ventilate the chamber while firing. One problem occurred almost immediately during testing when the blast gases accumulated in the section where spent cartridges and links were saved and sometimes ignited. Occasionally this was strong enough to actually deform the chamber. The spent shell case section was thoroughly ventilated and muzzle brakes were introduced to successfully cure the problem.
Resolving the problem with the guns had prevented the aircraft from undergoing its State acceptance trials in July 1953 as stipulated and a special commission was appointed to conduct the trials on 31 December 1953. After the manufacturer's trials were successfully concluded in January 1954 the aircraft was turned over and the State acceptance trials lasted from 21 January—15 March 1954. The tests were generally successful with the Il-40 proving to be easy to fly, maneuverable enough to be a handful for the MiG-15bis
and MiG-17
fighters opposing it and considerably superior to the piston-engined Ilyushin Il-10
M ground-attack aircraft then in service. However fight tests did reveal blast gas ingestion when firing in a sideslip by the engine on the side opposite the sideslip. Several solutions were evaluated to cure the problem, but Ilyushin pushed for the more radical solution of extending the air intakes for the engines all the way to the nose of the aircraft and moving the guns to the bottom of the nose, behind the air intakes.
The change in position of the guns and the extension of the air intakes, which looked "uncannily like a double-barreled shotgun", allowed the nose wheel to be moved forward to lengthen the wheelbase. The guns were mounted behind the nose wheel well and a special shield was added to protect the gun barrels from debris thrown up by the nose wheel; it was mechanically linked to the nose wheel and extended when it did. Other changes included the replacement of the original AM-5F engines by the Tumansky RD-9
V, an improved version of the AM-5F, the normal bomb load was increased to 1000 kg and 1400 kg (3,086.5 lb) in overloaded condition, and a rear-view mirror was added to allow the pilot to better observe the rear upper hemisphere.
ordered production to begin at Factory (Zavod) No. 168 at Rostov-on-Don
of the improved version, designated as the Il-40P. The Il-40P prototype first flew on 14 February 1955 and began State acceptance trials on 12 October 1955. The changes had resolved all the problems suffered by the earlier design and an order for a first batch of forty production machines was placed.
Five of these had been completed by the spring of 1956 and were undergoing pre-flight tests when the entire program was canceled on 13 April 1956 and all components in preparation scrapped. A week later, the Attack Aviation branch of the VVS was superseded by the Fighter-Bomber branch and the doctrine of the VVS was drastically modified. No longer would the VVS provide close support to the Army, but rather it would use tactical nuclear weapons as part of the nuclear battlefield.
Before the program was canceled two variants had been studied by Ilyushin. The first was an artillery-spotting version known as the Il-40K. This model added a third crewman in a redesigned forward fuselage. The air intakes were reverted to their original position as the guns had been placed in the small wing bomb bays and there wasn't any danger of the engines ingesting blast gasses from the guns. The spotter-navigator was given an extensively glazed position at the tip of the nose that was well-protected with armor and bulletproof glass. The first fuselage was nearing completion when the order came to cancel the entire program. The second variant was a torpedo
-carrying version called the Il-40T which was based on the fuselage of the Il-40K, but the navigator-bombardier's position had optically flat glass panels to facilitate aiming. Not much effort was devoted to this model and it was canceled at an early stage.
NATO reporting name
NATO reporting names are classified code names for military equipment of the Eastern Bloc...
: Brawny) was a two-seat Soviet
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....
jet-engined
Jet engine
A jet engine is a reaction engine that discharges a fast moving jet to generate thrust by jet propulsion and in accordance with Newton's laws of motion. This broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets...
armored ground-attack aircraft. The first prototype flew in 1953 and was very successful except when it fired its guns, as their combustion gasses would disturb the airflow into the engines and cause them to flameout
Flameout
A flameout refers to the failure of a jet engine caused by the extinction of the flame in the combustion chamber. It can be caused by a number of factors, including fuel exhaustion; compressor stall; insufficient oxygen supply; foreign object damage ; severe inclement weather; and mechanical...
or hiccup. Remedying this problem took over a year and involved the radical change of moving the engine air intakes all the way to the very front of the aircraft and repositioning the guns from the tip of the nose to the bottom of the fuselage, just behind the nose wheel. For all that the aircraft now resembled a double-barreled shotgun from the front its problems had been cured and it was ordered into production in 1955. But only five production aircraft had been completed before the entire program was canceled in early 1956 when the VVS discarded its close air support doctrine in favor of tactical nuclear weapons on the battlefield.
Development
Sergey Ilyushin had begun design studies during 1950–51 for a jet-engined ground-attack aircraft possessing better performance characteristics than was possible with piston-engined aircraft. By the end of 1951 the Ilyushin design bureau had prepared a technical proposal for a two-seat armored aircraft using two Mikulin AM-5Tumansky RD-9
|-References:* The Osprey Encyclopedia of Russian Aircraft: 1875-1995, Bill Gunston, ISBN 1-85532-405-9.-External links:...
axial-flow
Axial compressor
Axial compressors are rotating, airfoil-based compressors in which the working fluid principally flows parallel to the axis of rotation. This is in contrast with other rotating compressors such as centrifugal, axi-centrifugal and mixed-flow compressors where the air may enter axially but will have...
turbojets rated at 2150 kgf (4,740 lbf) at military power and 2700 kgf (5,952 lbf) with afterburner
AfterBurner
The AfterBurner is a lighting solution for the Game Boy Advance system that was created by Triton-Labs.Originally, portablemonopoly.net was a website created to petition Nintendo to put some kind of light in their Game Boy Advance system...
. In January 1952 Ilyushin sent this proposal to the government, which was quickly accepted, and he was directed to design and build one prototype.
The Il-40 had wings set low on the fuselage, swept back at an angle of 35°, and a tricycle undercarriage. The two AM-5 engines were in pods adjacent to the fuselage. As was traditional for Ilyushin ground-attack aircraft the core of Il-40's structure was a load-bearing armored shell that protected both crew positions, six fuel tanks and part of the radio and electrical equipment. The thickness of the shell ranged from 3 millimetre in thickness. The armored bulkhead protecting the pilot from the front was 10 mm (0.393700787401575 in) thick. The cockpit
Cockpit
A cockpit or flight deck is the area, usually near the front of an aircraft, from which a pilot controls the aircraft. Most modern cockpits are enclosed, except on some small aircraft, and cockpits on large airliners are also physically separated from the cabin...
glazing was also bulletproof and the pilot was given an 8 mm (0.31496062992126 in) armored headrest to protect him against shells fired from above and behind. The gunner was protected by armor 4 millimetre thick. The total weight of the armored shell and the bulletproof glass was 1918 kg (4,228.5 lb). Ejection seats were provided for both crewmembers. Three perforated airbrakes
Air brake (aircraft)
In aeronautics, air brakes or speedbrakes are a type of flight control surface used on an aircraft to increase drag or increase the angle of approach during landing....
were fitted on the rear fuselage, one on each side and one underneath, to enhance the aircraft's maneuverability during a dive.
The initial armament was six 23 mm (0.905511811023622 in) Nudelman-Rikhter NR-23
Nudelman-Rikhter NR-23
The Nudelman-Rikhter NR-23 is a Soviet cannon widely used in military aircraft of the Soviet Union and Warsaw Pact. It was designed by A. E. Nudelman and A.A. Rikhter to replace the wartime Nudelman-Suranov NS-23 and VYa cannon, entering service in 1949....
autocannon
Autocannon
An autocannon or automatic cannon is a rapid-fire projectile weapon firing a shell as opposed to the bullet fired by a machine gun. Autocannons often have a larger caliber than a machine gun . Usually, autocannons are smaller than a field gun or other artillery, and are mechanically loaded for a...
mounted in the nose, three on each side, each with 150 rounds, with their muzzles protruding into the slipstream
Slipstream
A slipstream is a region behind a moving object in which a wake of fluid is moving at velocities comparable to the moving object . The term slipstream also applies to the similar region adjacent to an object with a fluid moving around it...
. One NR-23 was mounted in a remotely controlled Il-K10 tail barbette
Barbette
A barbette is a protective circular armour feature around a cannon or heavy artillery gun. The name comes from the French phrase en barbette referring to the practice of firing a field gun over a parapet rather than through an opening . The former gives better angles of fire but less protection...
with 200 rounds. It had a maximum elevation of 55°, a maximum depression of 40° and could traverse 60° to either side. The Il-K10 could traverse at a rate of 42° per second and elevate at a rate of 38° per second. Four small bomb bay
Bomb bay
The bomb bay or weapons bay on some military aircraft is a compartment to carry bombs, usually in the aircraft's fuselage, with "bomb bay doors" which open at the bottom. The bomb bay doors are opened and the bombs are dropped when over the target or at a specified launching point.Large-sized...
s were fitted in the wings with a maximum capacity of 100 kg (220.5 lb) each. Alternatively four bomb racks could be fitted under the wings that could carry bombs up to 500 kg (1,102.3 lb),82 mm (3.2 in) TRS-82 or 132 mm (5.2 in) TRS-132 rockets, or drop tank
Drop tank
In aeronautics, a drop tank is used to describe auxiliary fuel tanks externally carried by aircraft. A drop tank is expendable and often jettisonable...
s with a total capacity of 1100 litres (290.6 US gal). The normal bomb load was 400 kg (881.8 lb), but 1000 kg (2,204.6 lb) could be carried at overload. Under overloaded conditions a maximum of twelve TRS-82 or eight TRS-132 rockets could be carried. Two cameras were fitted in the rear fuselage for day and night damage-assessment photos.
First flown on 7 March 1953, flight tests revealed no serious shortcomings in the air. The operational CG
Center of gravity of an aircraft
The center-of-gravity is the point at which an aircraft would balance if it were possible to suspend it at that point. It is the mass center of the aircraft, or the theoretical point at which the entire weight of the aircraft is assumed to be concentrated. Its distance from the reference datum is...
was too far aft, but this was only a minor problem when landing, taking off and taxiing
Taxiing
Taxiing refers to the movement of an aircraft on the ground, under its own power, in contrast to towing or push-back where the aircraft is moved by a tug...
, especially when coupled with the rather short wheelbase
Wheelbase
In both road and rail vehicles, the wheelbase is the distance between the centers of the front and rear wheels.- Road :In automobiles, the wheelbase is the horizontal distance between the center of the front wheel and the center of the rear wheel...
. The biggest problem proved to be the guns and their effect on the engines. During the first aerial test of the cannons at the end of March 1953 the muzzle flash
Muzzle flash
Muzzle blast is the term used to describe the release of high temperature, high pressure gases expelled from the muzzle of a firearm when it is discharged. Muzzle flash is the term used to describe the visible light of the muzzle blast. The blast and flash are caused by the combustion products of...
temporarily blinded the pilot and both engines flamed out
Flameout
A flameout refers to the failure of a jet engine caused by the extinction of the flame in the combustion chamber. It can be caused by a number of factors, including fuel exhaustion; compressor stall; insufficient oxygen supply; foreign object damage ; severe inclement weather; and mechanical...
. The pilot was able to restart the engines and made it back safely, but Sergey Ilyushin immediately started an investigation into the cause of the engine problems. Ground tests with high-speed cameras revealed that none of the muzzle brake
Muzzle brake
Muzzle brakes and recoil compensators are devices that are fitted to the muzzle of a firearm or cannon to redirect propellant gases with the effect of countering both recoil of the gun and unwanted rising of the barrel during rapid fire...
s or blast suppressor
Flash suppressor
A flash suppressor, also known as a flash guard, flash eliminator, flash hider, or flash cone, is a device attached to the muzzle of a rifle or other gun that reduces the visible signature of the burning gases that exit the muzzle. This reduces the chances that the shooter will be blinded in dark...
s tested made any difference; the engines would hiccup even if only a single gun fired just five to ten rounds.
A decision was made to replace the six NR-23 guns in the nose with four AM-23 cannon with 225 rounds per gun that had a rate of fire 50% greater than that of the NR-23 and to totally revise the gun installation. The guns were moved to the very tip of the nose in a separate compartment made of heat-resistant steel and provided with a special blast deflector chamber to deflect the blast gasses away from the engine inlets. Two doors were provided at the bottom of the chamber to ventilate the chamber while firing. One problem occurred almost immediately during testing when the blast gases accumulated in the section where spent cartridges and links were saved and sometimes ignited. Occasionally this was strong enough to actually deform the chamber. The spent shell case section was thoroughly ventilated and muzzle brakes were introduced to successfully cure the problem.
Resolving the problem with the guns had prevented the aircraft from undergoing its State acceptance trials in July 1953 as stipulated and a special commission was appointed to conduct the trials on 31 December 1953. After the manufacturer's trials were successfully concluded in January 1954 the aircraft was turned over and the State acceptance trials lasted from 21 January—15 March 1954. The tests were generally successful with the Il-40 proving to be easy to fly, maneuverable enough to be a handful for the MiG-15bis
Mikoyan-Gurevich MiG-15
The Mikoyan-Gurevich MiG-15 was a jet fighter developed for the USSR by Artem Mikoyan and Mikhail Gurevich. The MiG-15 was one of the first successful swept-wing jet fighters, and it achieved fame in the skies over Korea, where early in the war, it outclassed all straight-winged enemy fighters in...
and MiG-17
Mikoyan-Gurevich MiG-17
The Mikoyan-Gurevich MiG-17 is a high-subsonic fighter aircraft produced in the USSR from 1952 and operated by numerous air forces in many variants. Most MiG-17 variants cannot carry air-to-air missiles, but shot down many aircraft with its cannons...
fighters opposing it and considerably superior to the piston-engined Ilyushin Il-10
Ilyushin Il-10
Ilyushin Il-10 was a Soviet ground attack aircraft developed at the end of World War II by the Ilyushin construction bureau...
M ground-attack aircraft then in service. However fight tests did reveal blast gas ingestion when firing in a sideslip by the engine on the side opposite the sideslip. Several solutions were evaluated to cure the problem, but Ilyushin pushed for the more radical solution of extending the air intakes for the engines all the way to the nose of the aircraft and moving the guns to the bottom of the nose, behind the air intakes.
The change in position of the guns and the extension of the air intakes, which looked "uncannily like a double-barreled shotgun", allowed the nose wheel to be moved forward to lengthen the wheelbase. The guns were mounted behind the nose wheel well and a special shield was added to protect the gun barrels from debris thrown up by the nose wheel; it was mechanically linked to the nose wheel and extended when it did. Other changes included the replacement of the original AM-5F engines by the Tumansky RD-9
Tumansky RD-9
|-References:* The Osprey Encyclopedia of Russian Aircraft: 1875-1995, Bill Gunston, ISBN 1-85532-405-9.-External links:...
V, an improved version of the AM-5F, the normal bomb load was increased to 1000 kg and 1400 kg (3,086.5 lb) in overloaded condition, and a rear-view mirror was added to allow the pilot to better observe the rear upper hemisphere.
Production
Ilyushin began construction of another prototype to evaluate this solution and this was endorsed on 16 October 1954 when the Council of MinistersGovernment of the Soviet Union
The Council of Ministers of the Union of Soviet Socialist Republics , was the de jure government comprising the highest executive and administrative body of the Soviet Union from 1946 until 1991....
ordered production to begin at Factory (Zavod) No. 168 at Rostov-on-Don
Rostov-on-Don
-History:The mouth of the Don River has been of great commercial and cultural importance since the ancient times. It was the site of the Greek colony Tanais, of the Genoese fort Tana, and of the Turkish fortress Azak...
of the improved version, designated as the Il-40P. The Il-40P prototype first flew on 14 February 1955 and began State acceptance trials on 12 October 1955. The changes had resolved all the problems suffered by the earlier design and an order for a first batch of forty production machines was placed.
Five of these had been completed by the spring of 1956 and were undergoing pre-flight tests when the entire program was canceled on 13 April 1956 and all components in preparation scrapped. A week later, the Attack Aviation branch of the VVS was superseded by the Fighter-Bomber branch and the doctrine of the VVS was drastically modified. No longer would the VVS provide close support to the Army, but rather it would use tactical nuclear weapons as part of the nuclear battlefield.
Before the program was canceled two variants had been studied by Ilyushin. The first was an artillery-spotting version known as the Il-40K. This model added a third crewman in a redesigned forward fuselage. The air intakes were reverted to their original position as the guns had been placed in the small wing bomb bays and there wasn't any danger of the engines ingesting blast gasses from the guns. The spotter-navigator was given an extensively glazed position at the tip of the nose that was well-protected with armor and bulletproof glass. The first fuselage was nearing completion when the order came to cancel the entire program. The second variant was a torpedo
Torpedo
The modern torpedo is a self-propelled missile weapon with an explosive warhead, launched above or below the water surface, propelled underwater towards a target, and designed to detonate either on contact with it or in proximity to it.The term torpedo was originally employed for...
-carrying version called the Il-40T which was based on the fuselage of the Il-40K, but the navigator-bombardier's position had optically flat glass panels to facilitate aiming. Not much effort was devoted to this model and it was canceled at an early stage.
Variants
- Il-40 - First prototype
- Il-40P - Second prototype and five production aircraft.
- Il-40K - (korrektirovshchik - corrector) - Artillery spotter, three-seater with spotter-navigator in glazed nose cockpit.
- Il-40T - (torpedonosets) - Torpedo bomber, three-seater with navigator in glazed nose with optically flat panels for weapon aiming.
- Il-42 - Late 1960s revival of the Il-40 concept, beaten in competition with the Sukhoi T-8 (prototype Su-25)
- Il-102 - Ultimate iteration of the Il-40/Il-42, with modern avionicsAvionicsAvionics are electronic systems used on aircraft, artificial satellites and spacecraft.Avionic systems include communications, navigation, the display and management of multiple systems and the hundreds of systems that are fitted to aircraft to meet individual roles...
and engines, also beaten by the Sukhoi T-8.