SUKHOI'STUPOLEVDESIGNS

ANT-5 FIGHTER PROTOTYPEDuring the mid 1920s, the Air Forces

called for a new fighter capable of compet-ing with the best foreign aircraft In theautumn of 1925, Andrei Tupolev and NikolaiPolikarpov received an official request for aproposal for a new fighter aircraft A designgroup, headed by Aleksandr Putilov, wascreated at TsAG I

The duties within the group were sharedas follows Aleksandr Putilov was busy withthe fuselage and landing gear design,Nikolai Petrov handled assembly integra-tion, Nikolai Nekrasov was responsible forthe empennage, wing design was byVladimir Petlyakov, Evgeny Pogossky wasa head of aircraft equipment and IvanPogossky was responsible for the power-plant The task of designing the engineframe mounting was assigned to PavelSukhoi He was also designated as theleading engineerforthe aircraft

In two years, the first ANT-5 fighter (thedesignation ANT was derived from the ini-tials of Andrei N Tupolev) was ready to flyThis first Soviet all-metal fighter was pow-ered by the air-cooled 420 hp (313 kW)Jupiter-IV piston engine Developmenttests were conducted from August 10 untilSeptember 27 by test pilot Mikhail GromovAfter the tests were successfully accom-plished, the aircraft was moved to the NilVVS for official State Flight Tests eventuallyflown by test-pilots A Amsimov, AYumashevand Ivan Kozlov

Test results exceeded all expectationsThe aircraft proved to be superior to the bestforeign fighters Sea-level maximum speedwas 153 mph (246 km/h) and speed at analtitude of 9,843 ft (3,000 m) was 155 mph(250 km/h)

The ceiling was 27,100 ft (8,260 m) andthe fighter climbed to an altitude of 1 6 404 ft(5,000 m) in 1 1 4 mm The decision to initi-ate series production of a new fighter,designated I-4, was made in December1927, before the flight test program wascompleted

I-4 SECOND PROTOTYPE FIGHTERIn August of 1928, the second I-4 proto-

type powered by a 480 hp (358 kW)Jupiter-VI engine was built This aircraft haddetachable lower outer wing-panels Asmall center-wing section was integratedwith the fuselage structure It permittedremoval of the lower wing without the needto remove the landing gear Fuel tanks, witha total capacity of 1 1 1 gal (4201) of gasoline,were mounted from underneath Theirinstallation was simplified in comparison to

Designed by Pa vel Sukhoi during his tenure with the Tupolev Design Bureau, the ANT-5 served as theI-4 fighter prototype

the first aircraft On the ANT-5 they wereinstalled through the side door via a compli-cated traverse tube mounting The forwardfuselage structure was completelyredesigned for the convenience of machinegun ammunition loading, easy VOZ-1 andVOZ-2 radio installation and for the otherequipment installation Two footholds wereinstalled in place of the single one used on

the first aircraft Engine cylinder fairingswere installed during the flight tests whichwere conducted beginning December 1 ,1928 Flight performance of the second pro-totype was improved by the more powerfulengine The sea-level, the maximum speedbecame 160 mph (257 km/h) although at analtitude of 9,843 ft (3,000 m) the speedremained the same (155 mph)(249 km/h)

The ANT-5 was the first all-metal fighter developed and flown in Russia The corrugated metal (dural)fuselage was of semi monocoque construction

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The ANT-5 was powered by a British air-cooled radial engine the Jupiter IV then one of the most pow-erful and dependable in existence

The ANT-5 was technically a sesquiplane rather than a conventional biplane in that its lower wing wasof relatively diminutive span when compared to the upper

An improved version of the ANT-5 was equipped with the upgraded Jupiter VI radial Small span oflower wing is readily discernible in this view

The service ceiling decreased to 25 098 ft(7 650 m) but the rate of climb increasedThis fighter could reach an altitude of 16,404ft (5,000m) in 1 1 minutes

PRODUCTION I-4 FIGHTERPavel Sukhoi, as an official design

bureau representative was sent to FactoryNo 22 to supervise I-4 fighter productionThis factory was named after the 10thOctober Revolution anniversary Seriesproduction of the Jupiter-VI powered fighterbegan in 1928 The actual weight of 3,123 Ib(1 ,416 5 kg) exceeded the design weight of3,653 Ib (1,363 5 kg) Tests showed that theadditional weight caused the fighter perfor-mance to deteriorate Maximum sea-levelspeed was 155 mph (249 5 km/h) serviceceiling decreased to 23,260 ft (7 120 m),time to climb to an altitude of 16,404 ft(5 000 m) became 12 45 mm In spite ofthese figures, the I-4 fighter proved to beone of the best in the Soviet Union

Production of the I-4, powered by boththe Jupiter VI engine and its license version,the M-22, lasted for five years Factory No22 built 242 aircraft and the total number offighters built reached 370 The production I-4 weight increased even further to 3 153 Ib(1,430 kg) and the sea-level speeddecreased to 137 mph (220 km/h) Serviceceiling was 23,294 ft (7 100 m) Rate ofclimb had decreased only slightly It nowtook the fighter 1 4 3 minutes to reach16,404 ft (5 000 m) The high-speed turnrate was now 13 seconds, two secondsmore than that of the second prototype

Operational experience with the I-4made it clear that small aircraft had to have asmooth skin The corrugated skin, protrud-ing ribs and wheel spokes considerablyincreased the aircraft drag Developmentexperience with the I-4 proved to Soviet air-craft designers that all-metal fighter aircraftwere not only technically feasible but werewell advanced and promising

I-4BIS FIGHTER PROTOTYPEStriving to improve fighter performance

designers prepared the new, upgraded I-4bis fighter version for the flight testsm1931 The l-4bis prototype, a parasolmonoplane was built at TsAGI Wing slatswere operated from the cockpit Theyextended forward forming a slot with thewing and were the reason for the improve-ment in low speed stability A new engine

The I-4 as a fighter became one of the first true combat aircraft to enter the The I-4 s cockpit was equipped with basic instrumentation and a British-styleofficial VVS inventory control stick (note circular grip)

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cowling featured separate cylinder fairingsand Townend rings with added holes Theuse of such a ring fairing contributed greatlyto a 20-50% reduction of thefuselage/engine drag

On September 6, 1931 the l-4bis wassent to Nil VVS flight test facilities and wasflown for the first time on September 81931 Flight tests lasted from September 1 1until September 23 They showed consider-able improvement in the aircraft sperformance Sea level maximum speedincreased to 167 mph (268 5 km/h), speedat 9,843 ft (3,000 m) altitude was 158 mph(255 km/h) Service ceiling decreased to22,966 ft (7 000 m) as a result of the mono-plane configuration Rate of climbincreased considerably It took only 1 0 7minutes to get to 16,404 ft (5,000 m) alti-tude

Unfortunately, the slats were not imple-mented in the production version becausethis concept was thought to be ahead of itstime The designers decided that the slatsmust be automatic in order not to increasethe pilot workload Such an automatic sys-tem did not exist then in the Soviet UnionThis aircraft did not enter series productionDuring the I-4 development and production,experiments were conducted with manyvariants

I-4 VERSION FOR THE VLADIMIRVAKHMISTROI/AIRCRAFT UNIT

In 1929, the I-4 version intended for theaircraft-unit was built This modified versionhad a very small lower wing The aircraft-unit idea was suggested by Soviet aircraftdesigner Vladimir Vakhmistrov Fighters,carried by a TB-3 heavy bomber plane, wereto detach from the bomber and protect itfrom enemy fighters as well as attackground troops and antiaircraft artillery

This idea was appreciated greatly by theRed Army's top ranking commandersMikhail Tukhachevsky the People'sCommissar of Defense, wrote to the AirForce Commander in Chief, Yakov Alksnis"It is a great invention It is necessary tomake design predictions regarding the mis-sion of the TB-1 and TB-3 at a 497-746 mile(800-1,200 km) range in order to estimatethe total system effectiveness The inventormust be awarded a bonus "

Flight tests began on December 31931 Some well-known Soviet test-pilots,including Valery Chkalov, took part in thetest program Two I-4 fighters were installedon each TB-1 wing, in a form of piggybackload, with Valery Chkalov and A Anisimovat the controls After the carrier aircraftclimbed to the release altitude, one fightersucceeded in detaching However, a sec-ond fighter was damaged because ofslipshod interaction between the bomberand fighter crews Nevertheless, the fighterwas eventually released This experimentwas considered successful

I-4 FIGHTER PROTOTYPE ARMED WITHRECOILLESSGUNS

In December 1 9 3 1 , one I-4 productionfighter was equipped with two 76 mm recoil-less guns designed by Leonid KurchevskyThey were mounted in the wings at a dis-tance of 39 inches (1 m) from the bracingstrut mounting points During the tests, onegun exploded However, experimentslasted until the I-4 was phased out of service

The l-4bis was equipped with wing leading edge slats that could be activated from the cockpit The slatsimproved the! 4 slow speed landing and takeoff characteristics

Thel 4bis was powered by the Russian-built M-22 radial engine Complicated cowling design wasbased on NACA studies indicating reduced drag at high speed

The V Vakhmistrov aircraft unit was one of the select few in the Russian air force to be given speciallymodified l-4s optimized to be earned and launched from the wmgofa TB 1 twin eng/nebomber

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Two l-4s could be carried by a TB-1 Transporting the fighters increased their range, but decreased the range of the transport Regardless, it was determinedthe presence of the fighters created legitimate protection for the otherwise virtually defenseless bomber

about it According to a government letterdated May 1928, and signed by DeputyCommander in Chief of the Red Army AirForce, Yakov Alksnis, 75 l-4s of this configu-ration were to have been procured

I-4 FIGHTER WITH FLOATUNDERCARRIAGE

Floats, specially designed by AGOSTsAGI for the I-4, were built in 1931 Theywere installed on the aircraft on August 10However, tests were not completedbecause it was decided that there was nodemand for a fighter with a float undercar-riage

I-4 FIGHTER VERSION ARMED WITHROCKETS

In the summer of 1932 for the first timein the Soviet Union, 82 mm RS-82 rocketswere tested using the I-4 fighter as aweapons platform The Peoples' Commissarof Defense Mikhai Tukhachevsky, observedtest firing The results were considered posi-tive Later, the RS-82 rockets entered theRed Army inventory and were widely usedby Soviet fighters during World War II

I-4 FIGHTER WITH ROCKETBOOSTERS

In 1935 there was a need for short-termspeed increases, or boosting, in air combatWork on rocket booster installation was initi-ated with the I-4 fighter The type andmethod of tests were chosen An I-4 aircraft

During winter operations it was possible to equip the TB-1 -transported l-4s with ski-type landing gearfor operation from snow and ice Noteworthy are the stub wings of the TB-1 -dedicated l-4s

with the Red Army Air Force

I-4 FIGHTER POWERED BY THE BMW-VIENGINE

Reflecting an urgent demand by theRed Army Air Force for fighter planes and a

shortage of the M-22 air-cooled engines aproposal was made to build some I-4 fight-ers powered by German water-cooledBMW-VI engines rated at 600 hp (447 kW)This aircraft version was developed butthere is no information currently available

Once positioned on the wing of the TB 1 the I 4s were rigidly supported by a lightweight mounting assembly Release of the aircraft in flight was accom-plished manually by the pilots Clean separations proved relatively routine and there were few accidents or incidents

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was equipped with boosters designed byRNII (Rocket Scientific Research Institute)It was proposed to underslmg two boosterseach with three solid fuel rockets mountedinside The next year these plans wereinterrupted and, consequently, were neveraccomplished

I-4 DESCRIPTIONThe I-4 represented a class of single-

seat all-metal, braced biplanes with smallcantilever lower wings known as sesqui-planes

Fuselage: The conventional fuselagehad a triangular cross section The power-plant was mounted in the nose The opencockpit was in the middle of the fuselage justbehind the wing

Wing: The wings had an 18% thicknessto chord ratio at the point where the bracingstruts were installed and a 12% ratio at theroots and tips The upper three-spar winghad 10 ribs in each outer-wing panel Outer-wing sections of the upper wing were joinedat the aircraft centerlme The upper wingwas mounted via a narrow pylon and two V-shaped bracing struts extending from thelower wing Additionally, the upper wingwas attached to the fuselage via stream-lined flying wires The lower wing could notbe detached and was structurally integratedwith the fuselage

Empennage: The conventional empen-nage consisted of a vertical fin equippedwith the rudder and a horizontal tailequipped with the elevator The empen-nage was covered with corrugated skins

Landing gear: The landing gear con-sisted of two streamlined, wire-braced maingear struts and a tail skid Mam gear strutshad simple rubber shock absorption andwheels of 29 53 x 1 97 in (750 x 50 mm)size Several production fighters wereequipped with ski undercarriages fromDmitry Gngorovich I-2 fighters

Powerplant: The ANT-5 prototype waspowered by the Jupiter IV engine rated at420 hp (313 kW) The second prototype andthe first production aircraft were equippedwith the Jupiter-VI engine uprated to 480 hp(358 kW) The same engines poweredseries production aircraft As the Jupiter-IVentered license series production in the

A wooden ramp assembly was utilized to roll the I-4 onto the wing oftheTB 1 during the matingprocess Note dolly for elevating I 4 tai/wheeloutofmud

The I-4/TB-1 mating process was accomplished using manual labor only Nomechanical systems were employed

A mm iu ^ ten men was required to push the I-4 up the ramp and onto thewmgoftheTB-1

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PowerplantHorsepower (kW)Wmgspan (upper)Wingspan (lower)Length ft (m)Heightft(m)Total wing area ft2 (m2)Upper wing area ft2 (m2)Lower wing area ft2 (m2)Aileron area ft2(m2)Tailplaneareaft2(m2)Fmarea(m2)Rudder area (m2)Elevator area (m2)Max takeoff weight Ib (kg)Takeoff gross weight Ib (kg)Empty weight Ib (kg)Fuel weight Ib (kg)Oil weight Ib (kg)Wing loading Ib/ft2 (kg/m2)Power loading Ib/hp (kg/hp)Max speed mprt (km/h)@ s IMax speed mph (km/h) @ alt

Time to 1 6,400 ft (5,000 m) in mmCeiling ft (m)Range mi (km)Takeoff distance ft (m)Landing roll ft (m)Armament

ANT-5 (I-4 Prototype)Jupiter IV420(313)3 7 7 ( 1 1 486)1 8 7 (5 7)(?)(?)256 1 (23 8)213 1 ( 1 9 8 )43 (4 0)(?)(?)(?)(?)(?)(')2 960 (1 343)2030(921)(?)(?)1 1 53 (56 5)(9)153(246)1 55 @ 9 840(250 @ 3 000 m)1 1 427092(8260)n230 (70)459(140)2 x 7 62mm Vickers guns2x500rpg

I-4 (Production)M 22480 (358)3 7 4 ( 1 1 4)(')2388(728)9 1 8 ( 2 8 )256 1 (23 8)(?)(?)27 3 (2 54)31 (2 88)5 8 (0 54)1 6 4 ( 1 52 )9 0 (0 84)3 3 4 2 3 ( 1 5 1 6 5 )3 151 7(1 430)2 1466(974)697(316)86 (39)1 2 1 (592)74(337)137(220)1 4 3 ® 16400(231 @ 5 000m)1 4 323288(7 100)522 (840)2 952 (90)689(210)2x7 62mm PV-1 guns2x500rpg

ANT-5 AND I-4 SPECIFICATIONS AND PERFORMANCE

Initial flight trials of the I-4/TB-1 comb/nation took place during early December of 1931 Minimal difficulties were encountered though takeoffruns were considerably extended

During December of 1931 a single I-4 was modified and equipped with two 76mm Kurchevskymachine guns mounted one meter (39 4 ) outboard of the upper wing strut attachment points

Aski equipped! 4 in flight following launch from a TB-1 Relatively low speeds of the two aircraft contnbuted significantly to the safety of the operation

Soviet Union, designated as the M-22 andrated at 480 hp (358 kW), the aircraft wereequipped with these engines The two-bladed, 9 ft 2 in (2 8 m) diameter propellerwas of wooden construction Aircraft fuelcapacity was 1 1 6 gal (4391)

Armament: The two prototypes and thefirst production I-4 were armed with two 7 62mm ( 30 cal) English Vickers machine gunswith a total of 1,000 rounds of ammunitionThe next production aircraft were armedwith the Soviet-built 7 62 mm ( 30 cal) PV-1

machine guns

SINGLE SEAT I-8 (ANT-13) INTERCEP-TOR FIGHTER

In 1928 the Andrei Tupolev and NikolaiPolikarpov design bureaus were given arequest for a proposal for the I-5 single seatfighter The Nikolai Polikarpov bureau wasassigned the task of developing a fighterwith a wooden airframe structure whileAndrey Tupolev was responsible for design-ing a fighter with a hybrid wood and metal

structure There were many other projectsalready underway so work on this fighterwas not officially planned at AGOS TsAGIOne engineer suggested that everydesigner should work for 70 hours withoutpay on the I-5 design and building The AirForce Department readily responded andset up requirements for the new fighter inter-ceptor These requirements were officiallyapproved in January 1930 The fighterdeveloped by the Nikolai Polikarpov designgroup was given the I-5 code while theTupolev Design Bureau designated its pro-ject as the I-8 (ANT-13)

Pavel Sukhoi was given responsibilityfor the technical guidance of the design andconstruction of the interceptor fighter desig-nated Zhokey (Jockey) or Obschestvennysamolet (Public Airplane) The preliminarydesign and mockup were accomplished in ashort time According to design predictions,the aircraft would have the record speed inthe Soviet Union 193 mph (310 km/h) TheI-8 design was a single seat fighter poweredby a small water-cooled American CurtissConqueror piston engine rated at 600 hp(447 kW) (without reduction gearbox)

The I-8 was built by November of 1930On December 12, test pilot Mikhail Gromovsuccessfully flew the aircraft for the firsttime It took 10 32 mm for him to reach analtitude of 16404 ft (5,000 m) Take-offweight of the aircraft was 3,139 Ib (1,424kg)

Armament included two 7 62 mm ( 30cal) PV-1 machine-guns Stainless steelwas used in the airframe structure for thefirst time in the Soviet Union The wings hadall-metal frame covered with fabric skinsThe wing box streamline wires were madeof steel Spar caps were made of 2A stain-less steel, the ribs were made of Duraluminand the fuselage truss was welded ofchromium molybdenum tubes

Soon the aircraft was retrofitted A sta-bilizer control mechanism was installed andthe oil cooler capacity was increased Theretrofit was supposed to include the installa-tion of a supercharged, alcohol cooledengine, a change in the wing shape and itsairfoil section, installation of a propellerspinner, a closed cockpit canopy and theaddition of fairings to the landing gear InAugust 1 9 3 1 , the engine, horizontal tail andlanding gear were replaced and the flighttests continued

Only the fact that its development con-tinued through 1932 is known about the fateof this aircraft design

DIP (ANT-29) TWO SEAT CANNONFIGHTER

On July 26, 1930, the Air ForceAdministration of the Red Army reported itspreliminary requirements for a two-seatfighter armed with the 103 mm APK-8 recoil-less gun designed by Leonid Kurchevsky toTsAGI The Air Force command envisionedthe aircraft as capable of overcoming allSoviet and foreign production fighters interms of its fire power

On June 26, 1931 the basic require-ments were changed The fighter had to becapable of a maximum speed of 218 mph(350 km/h) an operating altitude of 16,404 ft(5,000 m), a service ceiling of 26,247 ft(8,000 m) and a range of 186 mi (300 km)Conceptual and preliminary design of theDIP fighter (DIP means dvukhmestny

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istrebitel pushechny - two-seat cannonarmed fighter designed at TsAGI as theANT-29) began in 1932

On December 26 the Air ForceAdministration again changed the specifica-tions for the fighter The goal for top speedwas raised to 233 mph (375 km/h) Therewas also a requirement for the installation offour 7 62 mm ( 30 cal) machine guns (two inthe nose fuselage and two in the rear fuse-lage for observer/gunner) By that time,some 1 2 percent of the airf rame already hadbeen built

Official review of the DIP design, pow-ered by two M-34 engines rated at 750 hp(559 kW), was on January 8, 1933 Thedesigners did not succeed in obtaining thedesign take-off and landing characteristicswith such a heavy fighter The deficiencywas especially drastic regarding the pre-dicted landing speed of 56 mph (90 km/h)

On April 2, TsAGI raised its objections tothe Air Force Administration and suggestedits own alternate ai rcraft specifications TheDIP aircraft had to be built by December 1 ,1933 However, frequent changes in therequirements and the resulting numerousstructural alterations reduced productionreadiness of the aircraft to 6 5% by the endof the year

Additionally, the empennage which hadalready been constructed was used for themulti seat Ml-3bis prototype fighter whichwas then being built at TsAG I

The main development work on the DIPfighter began in September 1934, andlasted until February 1935 During thedevelopment the designers had to replacethe M-34 engine with the M-100 rated at 760hp(567kW)

The test flights were conducted by test-pilot N Blagin, later to become well knownas the culprit of the crash of the largestSoviet transport plane at that time the ANT-20 Maksim Gorky Tests revealed manydeficiencies in the powerplant and in theempennage design After the introductionof a redesigned powerplant, a fin ofincreased area and empennage of a differ-ent shape on May 3, 1935, the designersagain moved the aircraft to the test airfield

Smooth skin with flush riveting and thebuilt-in 103 mm APK-8 recoilless gun maybe considered the distinguishing features ofthe aircraft design The gun barrel wentthrough the whole length of the DIP fuse-

I-8 was built ofdural and used fabric only where absolutely necessary It was comparable in manyrespects to the fighters then being produced in countries such as France and Germany

The DIP was equipped with a single 103mmAPK-8 rocket launcher twoforward firing? 62 ShKASmachine guns and a single aft-firing 7 62 ShKAS

lage Because of the tests, the designersdecided to increase the stabilizer area andreduce the area of the elevator whileenhancing the effectiveness of the rudderTo eliminate the aircraft s tendency to roll tothe right, the ailerons were equipped withtrim tabs

The radiators did not provide therequired engine cooling and leaked aftereach landing Besides the inherent defi-ciencies mentioned above, the aircraftproved to be unstable throughout the rangeof possible operational CG positions It waspointed out in the official report on the flighttests The DIP aircraft must be considered

efficient for experimental and scientific pur-poses with all shortcomings eliminated InMarch 1936 TsAGI received an order tostop work on the DIP aircraft developmentbecause of the number of design deficien-cies and the cancellation of the APK-8 gundevelopment

DIP AIRCRAFT DESCRIPTIONFuselage: The primary structure of the

all-metal fuselage consisted of 20 framesand a longitudinal framework whichincluded several longerons and stringers Asmooth skin with flush riveting covered thefuselage The APK-8 gun barrel extended

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The exhaust nozzle for theAPK-8 extended beyond the tailcone of the empennage and ran forward a/Ithe way through the fuselage

The DIP was equipped with a conventional split flap under the wing center section Each flap segmentended at the beginning of the inboard section of each aileron

Thel-14 an advanced design for its day could be equipped with ski type landing gear Thusconfig-ured however the landing gear could not be retracted

from the lower nose of the fuselage Thecockpit was equipped with a canopy madeof panels of flat glass An upper canopy sec-tion slid backwards providing good accessto the cockpit

The observer cockpit in the center fuse-lage section also had a sliding canopy Therear fuselage was integrated with a perma-nently attached vertical stabilizer Adischarge nozzle for the compensating blastfrom the recoilless cannon extended fromthe tail fairing

Wing and Empennage: The low wingfeatured a center wing section and two outerwing panels which consisted of a set of ribsand three spars which formed the wing tor-sion box Each outer wing panel wasequipped with ailerons in two sections oneach side Four-sectioned air brake panelswere installed on the wing between the fuse-lage and the ailerons The two enginenacelles were underslung at the ends ofcenter wing section

A conventionally configured empen-nage consisted of vertical and horizontal tailunits The rudder, with horn and mass bal-ance, was installed on the integral fin Anadjustable-incidence wire-braced tailplanewas attached to the fin above the fuselageElevators were equipped with trim tabs

Powerplant: The aircraft was poweredby two 760 hp M-100 engines with all-metal,ground-adjustable 3 4 m dia propellers Theengines were mounted in the front of theengine nacelle sections Radiators,equipped with controllable shutters wereinstalled below the engines

Landing gear: Mam gear struts weremounted in the engine nacelles behind theengines They were attached to the wingfront spar and retracted backwards suchthat part of each retracted wheel protrudedfrom the bottom of the nacelles Most of thewheels and the gear struts were covered bythe undercarriage doors The tail skid (with-out a tail wheel) was installed in the rearfuselage

Armament: The aircraft was armedwith a single 103 mm APK-8 gun and two7 62 mm ( 30 cal) ShKAS machine-gunsmounted in the center wing section Anobserver had a single backwards firingShKAS machine-gun for preventing enemyattacks from the rear

The I 14 like several of its predecessors was powered by a British radial engine inthiscase theMercury VS2 Ski bridles visible here are noteworthy

ANT-31 (I-14) PROTOTYPEFIGHTER

Simultaneously with the development ofrecord-setting airplanes the Pavel Sukhoiteam continued work on fighter designs In1932, the Sukhoi team received a request

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DIP SPECIFICATIONS ANDPERFORMANCEPowerplantHorsepower (kW)eaWmgspanft(m)Length ft (m)Height ft (m)Wing area ft* (m2)Wheel trackTailplane area ft2 (m2)Fin area (m2)Fuel gal (I)Max speed mph(km/h)@ s IMax speed mph(km/h) @ alt

Time to 16,400 ft(5,000m) in mmArmament

2x M 100760 (566)6 2 9 4 ( 1 9 1 9 )3 6 4 ( 1 1 1 )1 8 0 ( 5 5 )2756 4 (56 86)159(485)8 9 4 4 ( 8 3 1 )41 44 (3 85)283(1 072 1)

183(296)

2 1 9 @ 1 3 1 2 0(352 @ 4 000 m)

961 X A P K 8103mm cannon3 x ShKAS762nm machine guns

for a proposal for a single-seat gun-equipped fighter with an enhanced weaponto outperform the best foreign fighters of itstype It was designated the I-14 or ANT-31with Andrei Tupolev's initials, who providedthe general leadership of all aircraft projectsatTsAGI

In May 1932, on the basis of aerody-namic predictions and preliminary design,TsAGI reported the estimated aircraft per-formance to the Principal Aircraft IndustryAdministration The full-scale developmentof an airplane and its mockup constructionhad begun in July L Osipov was appointedas Chief Engineer of the I-14 project Theprototype building factory began productionof separate assemblies in November 1932In December, the Air Force Administrationfinally confirmed the aircraft operationalrequirements That airplane was estimatedto have a maximum speed of 233-249 mph(375-400 km/h), a landing speed of 56-65mph (90-105 km/h), a time to climb to16,404 ft (5,000 m) of 7-8 minutes, a serviceceiling of 29,528-32,808 ft (9,000-10,000m) and a range of 155 mi (250 km)

The first prototype of the I-14 fighterpowered with a Bristol Mercury VS2 enginerated at 520/580 hp (388/433 kW), had beenmanufactured by the middle of May 1933 Itflew its maiden flight on May 27 with test-pilot K Popov at the controls

Several features differentiated that air-plane from the previous fighters built in theSoviet Union The pilot's cockpit washeated and enclosed by a transparent, nonsliding canopy which had a rearward hing-ing cap through which a pilot could enterAnother feature was the APK large caliberunderwmg guns designed by LeonidKurchevsky The I-14 fighter had an air-frame of mixed structure A smooth skin,which reduced the wet surface area and,consequently, the drag, covered the fuse-lage and fin

The wing and empennage were coveredwith a corrugated skin That prototype wasthe first all metal monoplane in the USSR onwhich smooth, stiffened skin with flush rivet-ing was used That was an achievement ofthe TsAGI experimental factory The proto-type fighter was built by skilled andexperienced workers as well as by youngassemblers who had been sent to the fac-tory by Komsomol

To improve the aircraft's performance,Pavel Sukhoi used a retractable undercar-riage and wheel brakes On June 8, theprototype fighter was given to TsAGI OALIDfor testing However, on July 17 the airplanewas returned for upgrading which continueduntil September 30 The I-14 prototypefighter underwent tests but from September25 until November 14 it was again beingretrofitted

Official development flight tests of thefirst fighter were held from October 6 tillDecember 13, 1933 A 9 ft 4 in (2 85 m)diameter variable-pitch propeller wasinstalled on the airplane The I-14 hadreached a maximum sea level speed of 196mph (316 km/h) with a takeoff weight of3,208 Ib (1,455 kg) Speed at an altitude of16,404 ft (5,000 m) was 239 mph (384km/h) The service ceiling was reached in8 03 mm The airplane received a positiveevaluation and it was decided to begin thestate testing

A problem arose during aircraft develop-

Following initial trials, the I-14 undertook its official government flight tests during December of 1933The results were favorable, but interest in upgrading older aircraft proved too strong to overcome

Theski type landing gear on the I 14wasnon retractable The wells which normally accommodatedthe conventional gear assemblies were covered over with metal panels when skis were installed

The/ 14 also referred to as the ANT-31, was an all-metalaircraftandone ofthe first in Russia to beequipped with a fully enclosed cockp/t

ment with the Air Force AdministrationMilitary officials felt that the operationalrequirement could be better met by updatingexisting types of fighters Only because ofthe authority and persistence of AndreiTupolev was the Sukhoi team able to pro-

duce a new airplane On that occasionPavel Sukhoi wrote "The present configu-ration of the I-14 airplane is the first in ouraviation history because, hitherto, we hadno fighter-bombers When, in 1932, a ques-tion concerning the configuration of the

The second prototype I-14, known as the l-14bis or ANT-31, was equipped with an American-manufac-tured Wnght Cyclone radial engine

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Construction of the l-14bis was completed during February of 1934 The aircraft was similar in mostrespects to the original I-14 prototype with the exception of the engine and cockpit enclosure

The l-14bis had an open cockpit which was an item often preferred by pilots over the encloseddesigns which were beginning to come into vogue as a result of aerodynamic requirements

The l-14b/s's rudder and elevator skins were of corrugated dural The rest ofth^ an^an uu,,zed con-ventionaldura/ without corrugation

airplane arose, Andrei Tupolev was forcedto endure pressure from the Air ForceAdministration which intended to update theI-4 (ANT-5) airplane Only the authority ofAndrei Tupolev forced N 1 1 VVS to change itsopinion and now summing up, one can saythat we have produced an airplane thatmeets world standards"

I-14BIS SECOND PROTOTYPEFIGHTER

The second prototype of the ANT-31fighter, designated as l-14bis, was ready tofly in August 1933 A Wright Cyclone F-2engine, rated at 712 hp (531 kW) with anNACA type cowling, was installed on the air-craft The cockpit, of open type, differedfrom that of the first prototype and was moreconvenient for pilots N Fadeyev wasappointed as leading engineer for the I-14bis program

The construction of the second proto-type was completed on February 5, 1934

On February 13 the fighter had already beenreleased for the flight test program that wasto be carried out atOALID

The new airplane was chosen to partici-pate in the Air Force parade on May 1 , 1 9 3 4 ,with a mixed group of fighters (e g , I-15, I-14, I-16) that flew in formation over RedSquare The entire group flew over RedSquare at an altitude of 984 ft (300 m) andthen each aircraft performed a solo maxi-mum speed flight at 492 ft (150 m) altitudewith a subsequent zoom maneuver

On May 19,1934, Yakov Alksnis, the AirForce Commander-m- Chief, signed thefinal report of the state flight test program ofthe I-14bis fighter A Film was the leadingpilot, but Vladimir Kokkmaki, A Chernavskyand I Belozeorov also test-flew this aircraftThe conclusion of the official test flightreport read as follows "Due to its speedcapability at 16,404 ft (5,000 m) altitude, theI-14bis fighter was one of the best fighters ofthis type worldwide, and though it had a bit

worse speed at altitudes between 3,28I-9,893 ft (1,000-3,000 m) as well as ceilingand climb performance, its armament wasconsiderably better than that of competingdesigns"

The second prototype was wrecked inMay 1934 and had been passed on to theTsAGI experimental factory for repairs andmaintenance During 1935, the aircraft wasequipped with a new wing with leading-edgeslats and a ground-adjustable variable-pitch propeller The aircraft also received anew electric ignition system for the engineand a new armament set with the APK gunsbeing replaced by 7 62 mm ( 30 cal) ShKASmachine guns

Simultaneously, the designers had car-ried out design work and correspondingperformance predictions for a reinforcedwing with enlarged flaps All the necessarypreparations to replace the old engine with aWright Cyclone F54 and provisions for theinstallation of the new equipment had beenaccomplished It was planned that TsAGIwould mount a new 20 mm ShVAK gun tothe wing by May 20,1936

I-14 SERIES PRODUCTIONFIGHTER

The decision regarding full-scale pro-duction of the I-14 fighter already had beenmade in November 1933 It implied that pro-duction was to be done at Factory No 21 inGorky Therefore, a corresponding agree-ment between TsAGI and the above factorywas signed According to that agreement,technical drawings would have beenpassed on to the latter to start the full-scaleproduction The I-14 would have replacedthe Nikolai Polikarpov I-5 fighter An initialbatch of I-14 fighters would have consistedof 50 airplanes However, a new agreementhad been signed between TsAGI andFactory No 125 in Irkutsk on December 14After some hesitation, full-scale productionof the I-14 was ultimately transferred to theNo 125 factory

In 1936, the first series production air-craft had been delivered to the flight testdepartment and the test program was com-pleted at Nil VVS The conclusions of themilitary were as follows First, regardingflight performance and good handling quali-ties for takeoff, landing and aerobatics, thefighter was highly appreciatedNevertheless, because of dangerous spinperformance it could not be adopted for theAir Force before this considerable technicalshortcoming had been eliminated Second,it was recommended that TsAGI andFactory No 125 carry out all necessaryresearch and technical improvements toeliminate the dangerous spin behaviorAfter that they were to present the aircraft toNil VVS again for the fighter test program

In 1936, several other series productionaircraft of this type reached the status ofState Flight Test as well These fighterswere flown by test pilots Altynov and EPreman

Production aircraft were powered byWright Cyclone F-2 and F-3 engines as wellas with their Russian-built version the M-25 As a total, 55 aircraft were at theassembly shop but only 18 of them werecompleted and became serviceable withmilitary units during 1936-1937 Theassembly of the rest was not completedDue to the lack of a highly skilled work force,

26

the production I-14 fighter had poor qualityskins, joints etc

When the new I-16 fighter had been built,the I-14 lost its importance because thenewer fighter had better performanceexcept for takeoff and landing maneuver-ability Nevertheless, the I-14 fighter hadset a precedent in all-metal aircraft manu-facturing in the Soviet Union andconsiderable experience had been gainedin the utilization of smooth skins and in rivet-ing

I-14 FIGHTER DESCRIPTIONFuselage: A monocoque structure was

used forthe fuselage of the I-4 airplane Theframework was made of aluminum angles of0 02-0 03 in (0 5-0 8) mm thickness Thelongitudinal framework consisted of sparswith curved profiles and the lateral frame-work consisted of frames A center wingsection had a rigid truss joined by means ofa spar to the tail section of the fuselageEngine mounting points were riveted to theupper spar on the first frame Smooth skinwas used on the fuselage The cockpit waslocated in the central section just behind thewing trailing edge Although the prototypeairplane had a closed canopy, the secondprototype and production airplanes had anopen canopy

Wing: The cantilever wing was madewith a center wing section and two detach-able outer panels Its longitudinalframework consisted of two spars of trussedstructure with riveted tube caps All tubeswere made of chromium-molybdenumalloys with heat treatment except the last,cone shaped, which was made of an alu-minum alloy A transverse frameworkconsisted of six main and five intermediateribs Split landing flaps were placedbetween the second rib and the rib at thedetachable joint Ailerons were internallybalanced The prototype airplane had a cor-rugated skin but the second prototype andproduction airplanes had a smooth skin offlush riveted aluminum sheets of 0 02 in (0 5mm) thickness

Empennage: The prototype airplanehad a fin integral with the fuselage structureA joint was located in the upper part of thefin The second prototype and productionfighters had a framework consisting of twospars and three ribs These aircraft had asmooth-skinned fin that was attached to thefuselage at two mounting points The rud-der framework consisted of one spar ofriveted aluminum profile and three ribs cov-ered with a corrugated skin A tailplaneframework consisted of two spars that wereriveted assemblies of profiles and formedribs It had two landing wires from aboveand four flying wires from below The eleva-tor's framework consisted of one spar and aset of ribs The skin was corrugated and of0 02 in (0 5 mm) thickness None of the con-trol surfaces had balances

Undercarriage: The main gear wasretracted into the center wing section inwheel wells which were enclosed by doorsThe extension and retraction were cable-driven The mam wheels were fitted withbrakes A retractable tail skid was alsocable-driven

Powerplant: Fuel and oil tanks werelocated in the fuselage in front of the pilot'scockpit The engine was mounted in the for-ward fuselage in front of the tanks An

Nil VVS I-14 acceptance trials were held during 1936 using the first production aircraft Performancewas found to be acceptable

Production I-14s were equipped with retractable landing gear The retraction sequence differed somewhat from more conventional arrangements in that the gear retracted outward into their wells

Bench testing of the I-14 main gear retraction sequence Gear well doors were attached to the maingear struts Narrow tread of tires is noteworthy

English made Bristol Mercury VS2 enginewith a nominal power of 520 hp (388 kW)and maximum power of 580 hp (433 kW)powered the first prototype aircraft Thesecond prototype airplane was poweredwith an American Wright Cyclone F-2engine with a nominal power rating of 640hp (477 kW) and a maximum power of 712hp (531 kW) The early production aircraftwere powered with Wright Cyclone F-3engines (640/712 hp)(477/531 kW) and thelater production aircraft had the Soviet ver-sion, the M-25 rated at 700 hp (533 kW) Alltypes of engines were covered with NACA

type cowlingsWooden two-bladed propellers with

ground-adjustable pitch were used on allaircraft

Armament: Armament of the first pro-totype airplane consisted of one 7 62 mm( 30 cal) PV machine gun firing through thepropeller's disk and two 37 mm APK-37underwmg guns The second prototype wasequipped with two 37 mm APK-37 under-wmg guns Four D-1 bomb racks were alsoarranged on the airplane

The I-14 production airplanes werearmed with two ShKAS 7 62 mm ( 30 cal)

27

ANT-31, I-14 bis, AND I-14 PRODUCTION SPECIFICATIONS AND PERFORMANCE

The first ANT-25 was powered by an AM-34 liquid-cooled engine The engine differed from that usedon later configurations in that it had no reduction gearbox

The first ANT-25 was built with a wing that used external corrugations for structural stiffness Parasiticdrag proved considerably higher than originally anticipated and performance suffered accordingly

machine guns firing through the propellerdisk and two 45 mm APK-11 or 37 mm APK-37underwmgguns

RD (ANT-25) LONG RANGE RECORDAIRCRAFT

During the spring of 1931 , a restructur-ing of the entire Soviet experimental aircraftindustry and a search for an optimum orga-nizational structure of the design bureausbegan Thus an attempt was made to cen-tralize the whole design process and mergethe TsAGI with the Central Design BureauHowever, this consolidation did not takeplace In 1932, the TsAGI Aero-Hydrodynamic Department Sector AGOSwas transformed into the ExperimentalAircraft Building Sector Design Department(KOSOS) with its own TsAGI prototype fac-tory

Somewhat earlier, on December 7,1931 Klim Voroshilov suggested to theGovernment that a special aircraft with amaximum range of 8,078 miles (13 000 km)should be built The idea was approvedAndrei Tupolev started developing the pre-liminary design On April 8 1932 at theconference which authorized the RD (ANT-25) record-setting aircraft, Pavel Sukhoiwas selected to be head of the design andconstruction team Sukhoi was also theleading engineer for the project On May 4,1932, by a TsAGI order, Sukhoi was namedChief of the KOSOS team No 3 (in 1935 itbecame the Design Bureau No 3, or KB-3)that was charged with the RD developmentwork

Vladimir Petlyakov and Victor Belyaevwere made responsible for the wing struc-tural design They carried out most of thetheoretical work on the strength of anextremely high-aspect ratio wing Thedesign of the engine-propeller combinationwas led by engineers Evgeny Pogossky andK Mmkner Designers that later becamefamous also took part in the development ofparts of the aircraft

The preparation for transit flightsdemanded great efforts from the engineersboth from the maintenance and the testside This work along with the flight planswas done by engineers E Stoman and MTails Theoretical problems were solved bythe TsAGI group under the leadership of theprominent Soviet scientist professor VVetchmkin

The Central Institute of Aviation Motors(TslAM) was set up during 1930 for scien-tific research in the field of engineconstruction During 1931 , the AM-34 aircooled 750 hp (559 kW) vee engine wasconstructed by this institute under the direc-tion of engine designer Aleksandr MikulmAt that time, aircraft all over the world wereusing engines with a maximum of 500 hp(373 kW) This engine was chosen forinstallation on the RD aircraft then underdesign development

The RD was conceived and built as anall-metal single-engine low-wing mono-plane with a very high aspect ratio wingThe wing span-to-chord ratio exceeded 13Such a ratio was required to obtain maxi-mum aerodynamic efficiency or hft-to-dragratio Wing drag of aircraft then existing wasoften equal to half the drag caused by theentire aircraft It was very difficult to designa wing of such shape but the specialists ofthe TsAGI Structural Analysis Department

28

Powerplant

Horsepower (kW)Wmgspan (upper)Length ft (m)Height ft (m)Wing area ft2 (m2)Tailplane area ft2 (m2)Vertical tail area (m2)Takeoff gross weight Ib (kg)

cannon variantmachine gun variant

Empty weight Ib (kg)Fuel weight Ib (kg)Oil weight Ib (kg)Max speed mph (km/h)@ s IMax speed mph (km/h) @ alt

Time to 1 6,400 ft (5,000 m) in mm.Ceihngft(m)Takeoff distance ft (m)Landing roll ft (m)

ArmamentCannon

Machine guns

Bombs

ANT-31(I-1 4 Prototype)Bristol MercuryVS2580 (432)3 6 9 ( 1 1 25)21 19(646)11 02 (3 36)169 1 9 ( 1 5 7 2 )226(2 1 )1 7 2 2 ( 1 6)3 206 8 (1 455)

2 321 (1 053)(?)(?)1 9 6 2 ( 3 1 6 )2384® 16400(384 @ 5 000 m)80330 832 (9 400)394(120)722 (220)no brakes

2xAPK5(75mm)

PV-1(7 62mm)(?)

I-1 4 bis

Wnght Cyclone

712(530)3 6 9 ( 1 1 25)20 04 (6 1 1 )8 98 (2 74)1 8 0 8 2 ( 1 6 8 )22 6 (2 1 )1 7 2 2 ( 1 6)

3366(1 527)3 277 3 (1 487)2 303 2 (1 045)309(140)44(20)222 3 (358)231 © 1 6 4 0 0(372 @ 5 000 m)(9)28 864 (8 800)246 (75)394(120)

2XAPK-11(APK37)or2xPV 1(7 62mm)4xAO 10

I-1 4 Production

WC F-3/M-25

712/700(530/522)3 6 9 ( 1 1 25)2004(6 1 1 )1227(374)18222 (1693 )226(2 1 )1 7 2 2 ( 1 6)3 394 2 (1 540)

25765(1 169)(9)(?)232 9 (375)277 @ 1 1 1 52(449 @ 3 400)6530 898 (9 420)722/853 (220 260)(')

2XAPK-11(?)2xShKAS(7 62mm)4xAO-10

The second ANT-25 which incorporation many changes and improvements was nicknamed the Doubler and was equipped with an uprated AM-34 Thisengine also incorporated a reduction gearbox which significantly changed the aircraft s nose contours

managed to solve the problem The wingturned out to be lightweight and strong

An impressive quantity of fuel, 52% ofthe aircraft TOGW, was carried in the wingThis not only allowed space in the fuselageand made it easy to locate the crew and nec-essary cargo but it also made the structurelighter thus relieving wing loads The span-wise distribution of fuel loads placed themnear the point of maximum lift thus resultingin more efficient use of the wing structure

Investigations of high aspect ratio wingsled to a new chapter in the history of Russianand Soviet aerodynamics concerning air-craft structural vibration problems Amongthe theoretical analyses associated with thebuilding of the RD the structural vibrationstudies were especially interesting andessential

To obtain the maximum flight range itwas necessary to build an aircraft wing withan aspect ratio as high as possible No highperformance aircraft existed at that timewith such unusually narrow and long wingpanels before the RD However, concernhad been raised in technical journals overflutter problems with such high-aspect-ratiowing designs Flutter, as it was subse-quently determined, occurred if the flightspeed exceeded a certain value for the par-ticular structure involved, i e , a criticalspeed The designers of the RD naturallywere apprehensive that due to the highaspect ratio wing, the critical speed wouldbe very low

To solve this problem, a special flutterinvestigation group headed by MstislavKeldysh was formed within the TsAGIExperimental Aerodynamic Department Atthat time there was no way to predict flutterThere were two approaches that might leadto the solution of this problem One couldexamine a particular case the RD wing,experimentally and determine possiblemeasures for preventing wing flutterAnother approach would be to create a gen-eral theory of the phenomena and on thebasis of that theory, a design technique thatcould be applied to any particular caseMstislav Keldysh and his associates chosethe second approach to create a generaltheory to solve the flutter problem

The design of the aircraft was com-pleted during 1932 and the construction ofthe prototype began in June the same yearTwo prototypes were built simultaneouslyThe first one, equipped with a 750 hp (559kW) engine uprated to 874 hp (652 kW)took off for the first time one year later Thesecond prototype fitted with the M-34Rgeared engine, began its flights inSeptember of the same year

With the change to the geared AM-34 the engine cowling was improved aerodynamically Additionallythe transparencies were redesigned and the cockpit windscreen was reconfigured to reduce drag

During the flight tests, the designerswere astounded when the flight speed andrange were lower than specified The prob-lem was that the total wetted wing surfacehad been greatly increased due to the use ofa corrugated skin This resulted in a consid-erable increase in the drag and a resultingreduction in the flight speed and range Thecause was determined quickly

To solve the problem, the wing was cov-ered with linen and coated with varnishElongated fillets were added to blend thewing into the fuselage

As compared to the prototype, the sec-ond prototype had some structuraldifferences Due to the installation of thegeared engine, its cowling was altered Thecockpit view was improved by increasingthe area of glazing During flight tests, thevertical stabilizer was enlarged and variousrudders were tried

Although the aircraft was still underdevelopment, it was already considered oneof the outstanding achievements of Sovietaeronautical science and technology

Grand transit flights started on June 30,1934, after a series of training flights Thecrew included the pilots Mikhail Gromov andA Film and the navigator I Spirm The firstofficial flight of the ANT-25 aircraft (the sec-

ond prototype) set a USSR record by cover-ing a range of 2 774 miles (4,465 km) in 27hours and 21 minutes On June 24, thatsame year, the crew claimed a new USSRrecord by traversing a range of 4,076 miles(6,559 km) in 39 hours and one minute

The aircraft took-off from an airfield nearMoscow equipped with a special take-offstrip At the beginning of the runway, a spe-cially profiled concrete ground ramp wasbuilt to help takeoff From September 12until September 15 the crew accumulated75 flight hours flying the RD along the routebetween Moscow, Ryazan and Kharkovand covering a range of 12,441 km Thisconsiderably exceeded the record estab-lished by the French pilots Bosseau andRossi Pilot M Gromov was declared aHero of the Soviet Union for this achieve-ment

The same year, the famous pilot SLevanevsky, a Hero of the Soviet Union,expressed in the press the idea of a transpo-lar flight from the USSR to the USA andbegan preparation for such a flight Besidesthe flight tests engine tests were done onthe full-scale engine test stand Due to thepreparations of the RD aircraft for the flightto the USA, Pavel Sukhoi was made respon-sible for the design work by an order issued

Though of all-metal construction the wing was covered with a smooth fabric and par/nted The result-ing surface was extremely smooth and created little residual parasitic drag

29

The crew of the ANT-25 during its first trans-Arctic flight attempt was com-manded by famous Russian pilot, S. Levanevsky.

The Doubler took off on its record flight on June 20, 1936. The command pilotwas V. Chkalov.

by the People's Commissar of HeavyIndustry, SergoOrdjonikidze.

During 1935, the crew, consisting ofpilots Sigizmund Levanevsky and GeorgyBaydukov and navigator V. Levtchenko,attempted to conduct a flight from the SovietUnion to San Francisco. The aircraft hadpassed a range of 1,243 miles (2,000 km)and was over the Barents Sea when thereappeared evidence of oil leakage from theengine. The aircraft commander turned backand landed near Novgorod. Baydukov, whohad much experience with blind flights, sawthat the oil had stopped leaking and decidedthat the engine was operating properly. Hetried to persuade Levanevsky not to abort themission.

Sigizmund Levanevsky stated that it wasimpossible to fly a single-engined aircraftover the North Pole and, after that, interest insuch aircraft faded away in the Soviet Union.It was thought that it was dangerous to usesuch an aircraft for long range and compli-cated flights. A decision was made to usemulti-engined aircraft for such flights, whichwas then done, but in vain. Therefore,attempts at setting records with either type ofaircraft were ignored for several years.

The famous Soviet pilot Valery Chkalov

wrote Joseph Stalin a personal letter sayingthat such flights should be resumed. Stalinresponded by offering to approve a flight withinthe country. Thus, the Moscow-to-FranzJoseph Land-to-Petropavlovsk-Kamchatskyroute, known as the Stalin route, was born.

For this purpose, the second prototypewas modified during 1936 to receive the M-34R ducted water cooled engine. Controllableshutters were mounted ahead of the aircooler. The two-bladed wooden propellerwas replaced with a three-bladed metal onewhich had given the best results out of theseries tested. Backup controls were installedatthe navigatorstation.

The engine cowl bottom was reworked sothat it could be raised or lowered from thecockpit. The aircraft also was modified forwater landings.

According to the conclusions made byTsAGI, the modifications resulted in the follow-ing improvements of the RD performance: therange increased by 7%; the ceiling increased1 ,312 ft (400 m) with the landing gear retracted(at a weight of 19,842 Ib (9,000 kg), the aircraftcould fly at 11,483 ft (3,500 m) with a greatrate-of-climb margin); the flight speed in long-range flight improved by 8%; the efficientaltitude zone was broadened; the engine rpm

in long-range flight was lowered.Only the rate-of-climb near the ground

with the landing gear extended wasunchanged. On June 20, 1936, the heavilyloaded aircraft, after a ground run of more than4,921 ft (1.5 km), gradually lifted off and beganclimbing. The aircraft crew, led by ValeryChkalov with co-pilot Georgy Baydukov andnavigator Aleksandr Belyakov, flew toPetropavlovsk-Kamchatsky.

After the long duration flight, the pilotsdecided to continue. However, because theweather became worse, pilot V. Chkalov hadto land the aircraft on a narrow spit of sand onUdd Island. The crew was in the air 56 hoursand 20 minutes flying 5,825 miles (9,374 km).All of the flight participants were declaredHeroes of the Soviet Union fortheirflight.

This flight revealed how great a dangerthat icing of the aircraft, especially of thepropellers, might constitute. Soon, the pro-peller was fitted with the first Soviet de-icerwhich was developed by the TsAGI.Crowds gathered at the traditional airparade in 1936 and enthusiastically wel-comed the ANT-25 and its crew, ValeryChkalov, Georgy Baydukov and AleksandrBelyakov.

The heroes dropped a message bag

RD/ANT-25

30

with greetings By government decree, theANT-25 was among the Soviet exhibits pre-sented at the World Airshow in Paris inNovember 1936 There, it proved a popularattraction and was one of the highlights ofthe show

Meanwhile, the crew was getting readyfor a long endurance flight Early in themorning of June 18, 1937, a takeoff wascleared from the Schelkovo airfield nearMoscow and the aircraft headed For theNorth Pole The flight was completed at1 9 20 Moscow time on July 20 The aircraftlanded at the Baracks airfield near the townof Portland, Washington, in the UnitedStates This nonstop flight was unparalleledin aviation history as it had lasted 63 hoursand 25 minutes A distance of 3,666 miles(5,900 km) had been covered over oceansand ice Due to unfavorable weather, theflight altitude had been at or above 13,123 ft(4,000 m) Several thousand kilometershad been flown blind

The names of the heroes were in thenewspapers and magazines all over theentire world for several weeks The worldgreeted Valery Chkalov, Georgy Baydukovand Aleksandr Belyakov enthusiastically

Three weeks later, a new flight wasmade with the ANT-25 across the NorthPole to the USA The crew was headed bythe Hero of the Soviet Union MikhailGromov who established a world rangerecord with this flight Gromov landed theaircraft at a field located three kilometersfrom San Jacmto, California The aircrafthad been in the air 62 hours and 17 minutescovering a range of 7,146 miles (11,500km) This achievement was not surpasseduntil the end of 1946

The historic flights had shown to theentire world not only the courage, fortitudeand skill showed by the pilots but also thehigh status of the Soviet aircraft industry Ina technology newspaper, Pavel Sukhoigave the following data on the aircraft "TheANT-25s are built exclusively from the high-grade materials The world of aeronauticalengineering does not know of an aircraft ofsimilar kind with such a great wing spanThe wing aspect ratio of the ANT-25 isapproximately 30% more than that of air-craft of similar types which have been built,both in the West-European countries andAmerica before now"

RD (ANT-25) AIRCRAFT DESIGNThe RD was a cantilever low wing

During one record attempt, f/ieDoubler was forced to make an emergency landing on Udd Island Theaircraft was successfully recovered without serious damage to the airframe

OnJune 18 1937 f/ieDoubler departed Schelkovo airfield on a record flight to America across theNorth Pole The flight took 63 hours and25 minutes to complete

monoplane with a wing aspect ratio of 13 3and a span 2 5 times greater than the fuse-lage length

Fuselage: The fuselage consisted oftwo parts A forward section was made inte-gral with the wing center section and a tailsection was of oval cross-section mono-coque design The transverse frameworkwas composed of stamped frames Theframes and stringers were of L shape

The fuselage skin was smooth and wasmade of 0 04 in (1 0 mm) and 0 07 in (1 8mm) thick aluminum Rivet heads projectedoutside the skin Four longerons were riv-eted above the skin and ran through theentire tail part of the fuselage

The cockpit, with all necessary equip-ment was aft of the engine Navigator's andcopilot's stations were located behind thejoint between the forward and tail fuselagesections All of the cabins were lined withbroadcloth on the inside

Wing: The primary structural compo-nents of the wing of ANT-6 section were

three truss spars and stringers The wingtransverse structural members included 18ribs (per each half wing) which were made oftubes All the structural members weremade from Duralumin sections, XMA alloychromium-molybdenum tubes and refinedsteel forged pieces The first two spars wereinterconnected by the structures of six fueltanks spaced between the ribs whichformed strong torsion boxes

Wing skin, except for the torsion boxarea, was from corrugated aluminum forstiffness Emergency ditching equipmentwas located in the wing leading edges In anemergency, the aircraft not only could landon water uneventfully but also could remainafloat For this purpose, fuel from sometanks was dumped and special rubberizedfabric bags were filled with air to provideextra buoyancy

The four section mass and Flettner(servo tab assisted) balanced ailerons werehinged to the third auxiliary spar Theaileron surface was covered with linen

LtoR Doublet crew members A Belyakov, VChkalov, and G Baydukov

LtoR Doubter crew members Gromov, Yumashev, and Daml/n Gromov already was a Hero of theSoviet Union one of the highest honors afforded a Russian citizen at the time

31

Gromov s aircraft landed in an empty flat field only a few miles from downtown San Jacmto California The aircraft proved a noteworthy attraction for virtuallyeveryone within walking or driving distance of the field and hundreds visited the landing site during the several days the aircraft was statically parked

Empennage: Tail surfaces were all-metal with a corrugated skin The controlsurfaces were aerodynamically balancedand were provided with Flettnertabs Unlikethe first RD aircraft, the corrugated wing andtail unit skins of the second prototype werecovered with linen and coated with aircraftdope

Landing Gear: The main landing gearfitted with oil- pneumatic shock absorbers,was attached to the first spar Operationwas by an electric actuator which was usedfor the first time in the USSR While inflightthe wheels were semi-retracted The outerportion of each wheel was enclosed in a fair-ing to reduce drag Dual wheels were fitted

Shiny wing undersurface the result of covering the metal with cloth and then painting for smoothnessis readily apparent in this view of theDoubler following its San Jacinto California

Following its record-setting flights, the ANT-25 was returned to Russia by boat It is seen during a low-altitude flyover of the 1937 Tushino airshow

32

to each landing gear leg Mam wheel sizewas 35 4x7 87 in (900x200 mm) The wheeltrack was 23 9 ft (7 28 m) All but the bottomhalf of the tail wheel was covered by a fair-ing

Powerplant: The aircraft was initiallypowered by the AM-34 1 2 cylinder water-cooled 750 hp (559 kW) engine with acompression ratio of 6 0 During the flighttests it was replaced with an M-34 engineuprated to 847 hp (652 kW) with a compres-sion ratio of 7 0 The second prototype wasequipped with an M-34R geared engine toimprove engine efficiency by reducing thepropeller speed The M-34R had a com-pression ratio of 6 0 and its power wasinitially equal to 800 hp (597 kW) The air-craft flown by the Valery Chkalov crew wasfitted with the M-34R engine uprated to 950hp (708 kW) A modular aluminum enginestructure with a so-called "dry crankcase"dramatically decreased oil consumptionContinuous engine operation for 80 to 100hours was possible

Various metal two and three bladed pro-pellers were installed and tested on theaircraft A three bladed, ground adjustablepropeller with polished blades was used forthe flights during 1936

The fuel system consisted of the centertanks of 1 340 gal (5,072 I) capacity, inter-mediate tanks containing 878 gal (3,323 I),extreme tanks with 589 gal (2,229 kg) and aservice fuel tank with 44 gal (167 I) Totalcapacity of the fuel system was 2 851 gal(10,791 I) Fuel distribution was such thatany of the tanks could supply the engine

The main oil tank contained 265 gal(1,003 I) of oil and the service tank held 55gal (2081)

The engine was water cooled Initiallythe radiators were arranged in the wingHowever the wing-mounted radiators weresubsequently replaced with a single unitwhich was installed under the engine Thenew radiator had improved air flow that wasregulated by pilot controlled intake shuttersand an adjustable exit flap

Equipment: Besides the mam mstru-

A reduced scale mock up of the ANT-25 was built for a movie about the world record distance flightsthe aircraft had flown Except for scale it s difficult to differentiate this reproduction from the original

The ANT 25 s radio station was located just aftof the pilots seat on the port side of the aircraft

The military version of the ANT 25 which has rarely been seen was designated RD-VV or DB-1 (the designation ANT 36 also was assigned1) About twentyof these aircraft eventually were built and sparingly utilized as long range bombers by the Russian air force

ments, the equipment also included blind-flying instruments A Soviet builtgyro-magnetic compass was installed forthe first time The radio equipment incorpo-rated a transceiver with a total weight ofabout 1 1 0 Ib (50 kg), which provided thecapability of communicating at a range of3,107 to 3,728 miles (5,000 to 6,000 km)Normal and emergency power supply unitsand aerials as well as a foldable telescopicmast intended for operation in case of anemergency landing were carried In addi-tion to the running lights, the aircraft wasfurnished with equipment for igniting anddispensing underwmg flares

For the first flight the copilots positionwas equipped with an additional set of con-trols and instruments Thus, it was possibleto fly the aircraft from that position

For astro-orientation, use was made ofan octant which only slightly differed from asextant but was more convenient than thelatter The octant was fitted with a doublechronometer to show mean and siderealtime The aircraft intended for the ValeryChkalov crew had more advanced equip-ment

DB-1 (RD-VV, ANT-36) LONG RANGEBUMBthf The original record-setting ANT 25 has been preserved It is displayed--along with other memorabilia-

The world records brought fame to y -in the Valery Chkalov museum m Chka/ovsk Russia

33

Soviet aviation Notwithstanding, each newstep forward was of much greater impor-tance to military aviation than to civilaviation

It was natural that Pavel Sukhoi usedthe RD design to create a long-rangebomber Production of a small batch ofthese aircraft was started They were desig-nated the DB-1 or RD-VV

The Voronezh factory made about 20DB-1 (ANT-36) aircraft That was the firstSoviet long-range bomber

However, the concept of a long-rangebomber changed with time and the DB-1 didnot go into service Various kinds of proto-types were built based on the productionaircraft

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DB-2 (ANT-37) LONG RANGE BOMBERAfter a futile attempt to make an effec-

tive bomber from the record-setting RD(ANT-25) aircraft, the DB-2 (ANT-37) long-range bomber was developed by the Sukhoiteam using whatever parts they could usefrom the RD aircraft This airplane wasequipped with two M-85 engines rated at800 hp (597 kW) each and it had to be capa-ble of a range of 3,107 mi (5,000 km) with a2,205 Ib (1,000 kg) bomb load at the stan-dard flight weight of 20,847-25,353 Ib(9,456-11,500 kg) General leadership ofthe project was carried out by AndreiTupolev himself

Two prototypes of the aircraft werebeing built simultaneously The first onewas ready on June 16, 1935, and its flighttest program began immediately On June20, the aft part of the fuselage wasdestroyed during a flight because of produc-tion defect in the stabilizer trim jack Thoughthe test pilot K Popov and the leading engi-neer M Yegorov managed to escapesuccessfully, the third crew member, a tech-nician, died in the crash The result of thisunexpected accident was an increasedemphasis on further scientific research onflutter and buffet in order to eliminate thesephenomena

Although the second DB-2, the secondprototype, had a wing root fairing and a rein-forced fuselage, its TOGW did not changeconsiderably That aircraft was test-flown atNil VVS and demonstrated a range of 3,107mi (5,000 km) with a 2,205 Ib (1,000 kg)bomb at the average speed of 132 mph (213km/h) This performance, except for range,was not sufficient in 1936 to justify full scaledevelopment for service with the Air Force

ANT-37BIS ("RODINA") RECORDAIRCRAFT

Because of government instructions,the DB-2 was redesigned to meet therequirement of a long-range (4,350-4,971mi)(7,000-8,000 km) airplane The DB-2airframe was little changed, but more pow-erful M-86 engines, rated at 950 hp (708kW) at sea level and 800 hp (597 kW) at analtitude of 26,247 ft (8,000 m), were installedas well as three-bladed propellers Allarmament was removed, fuel tank volumewas increased and other changes weremade before the record flight This third pro-totype of the DB-2 airplane finally built inFebruary 1936, had been given its ownproper name, Rodma (Motherland) All thework was carried out by the Sukhoi teamPavel Sukhoi himself was the creator of thisaircraft The fourth prototype, the Rodinaversion with a wet wing, also was being builtIt was designed for even longer rangeflights However, the airplane was nevercompleted

The Rodina airplane design and equip-ment were more sophisticated than those ofprevious Soviet military and record aircraftThe wing and empennage were coveredwith smooth skin

Fuel tanks were placed inside the fuse-lage Spars were made of metal tubesStreamlined wires braced the stabilizer tothe fuselage and fin The landing gearretracted to the rear into the nacellesLanding gear control was electrical for thefirst time in the USSR

On September 24-25, 1938, the worlddistance record for an aircraft with an all-

Production of the DB-2 was limited to the two prototypes and single production example The type wasnever introduced into the operational Russian air force inventory

The third DB-2 (seen being preparedforflight) became f/ie Rodina (Motherland) record setting aircraftIt was also referred to as the ANT-37bis

The Rodina was the first of the record-setting long-range aircraft to have a non corrugated wing sur-face A fourth DB-2, also for distance flying was never completed

On September24, the Rodina took-offwith an all-female crew The following day, it landed, having seta world distance record for gender Time aloft was 26 hours and 29 minutes

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RD (ANT-25) RD (ANT-25 DOUBLER), DB-2 (ANT-37), AND RODINA (ANT-37 bis) SPECIFICATIONS AND PERFORMANCE

PowerplantHorsepower (kW)Wingspanft(m)Length ft (m)Wheel track ft (m)Wing area ft2 (m2)Aileron areaft2(m2)Tailplane area ft2 (m2)Fin area ft2 (m2)Takeoff gross weight Ib (kg)Empty weight Ib (kg)Fuel weight Ib (kg)Wing loading lb/ftz(kg/m2)Power loading Ib/hp (kg/hp)Max speed mph (km/h)@ s I

Ceiling ft (m)Endurance (hr)Range mi (km)Takeoff distance ft (m)Armament

RD (ANT-25)

M 34750 (559)1 1 1 5 (34)4356(1328)23 9 (7 28)949 3 (88 2)75 88 (7 05)10063(935)59 73 (5 55)17632(8000)(?)(')(')(?)121 (1 95) w/gear attached1 69 (272) w/gear retracted27 092 (8 260)484 471 (7 200)(')(na)

RD (ANT-25 DOUBLER)

M34P950 (708)1 1 1 5 (34)4543(1385)23 9 (7 28)949 3 (88 2)75 88 (7 05)10063(935)5489(5 1 )24795(11 250)9 1686(4160)17103(7760)2628(1288)2755(125 )(?)

23288(7100)808 073 (1 3 000)5 2 1 5 ( 1 590)(na)

DB-2 (ANT-37)

2xM 85800(596) ea1089(332)492(15)(')(?)(')nH24684(11 200)127832(5800)n2 2 7 ( 1 1 1 3)1 3 0 ( 5 9 )187(301)

(?)(9)3182(970)1 000 kg bombs

RODINA(ANT-37b!S)2xM 86950 (708) ea101 7(31)4 9 2 ( 1 5 )(?)9149(85)n(7)H27550(12500)1 2 904 4 (5 855)1 2 177(5525)300(147)1 4 55 (6 6)186(300)

(')4 533 (7 300)3280(1 000)(na)

An approximately two-thirds scale replica of the ANT-25 is displayed at the Russian Air Force Museum atMonino The mock-up is accurately painted incream red and black and is finely detailed Even in scaled-down form it is a huge machine

female crew was established in the ANT-37bis Rod/na by Valentina GnzodubovaPolina Osipenko and Manna Raskova Therecord breaking flight took place along the

route from Moscow to Kerby Village whichwas 3 671 mi (5,908 km) long The flighttook 26 hours and 29 minutes to completeAfter that flight the airplane was operated by

Aeroflotand later up to 1943, as a researchplatform by an aircraft factory in Moscow

Another view of the approximately two-thirds scale ANT-25 replica at Monmo Construction materials appear to be a mix of metal, fiberglass and woodBuilding in which the ANT 25 is displayed dates to The Great Patriotic War (World War Two)

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