History of Tank Development in the USSR . Pivotal 1973

Annotation

This article, based on extensive archival documentation, presents a detailed and multi-perspective analysis of a pivotal moment in Soviet tank development: the concurrent adoption of the T-64A and T-72 tanks in 1973. It critically examines the decision-making process that led to the abandonment of a unified tank model for the Soviet Army, instead establishing a decades-long course of parallel production for different main battle tanks.

The core of the study rests on primary sources: internal reports of the USSR Ministry of Defense, correspondence and memoranda from military leadership (notably Marshal I. I. Yakubovsky), official letters and technical reports from the Malyshev Plant management and Chief Designer A. A. Morozov, and field trial records. This archival foundation allows the author to reconstruct the arguments and rationales of all major stakeholders.

The article meticulously contrasts the perspectives:

·        The Ministry of Defense's position, citing extensive field trial data from 1969-1973 to highlight persistent reliability issues with the T-64A's engine (5TDF), transmission, and running gear, ultimately deeming it unsuitable for mass production outside its native plant.

·        The Malyshev Plant and Design Bureau's defense, which presents its own statistical data and lists hundreds of implemented design improvements, arguing that the T-64A had reached satisfactory reliability by 1973 and that its shortcomings were either overstated or in the process of being resolved.

·        The pivotal intervention of military leadership, encapsulated in Yakubovsky's 1973 letter listing seven "structural deficiencies" of the T-64A, which served as the formal justification for initiating parallel production of the T-72.

A significant portion of the analysis is devoted to a point-by-point technical rebuttal by A. A. Morozov of the criticisms leveled in Yakubovsky's letter, covering aspects such as operational range, ammunition handling, cross-country mobility, and engine reliability. Furthermore, the article references later declassified industry journal data (from the 1980s) to compare the long-term reliability statistics of the T-64A, T-72, and T-80, challenging the established narrative of the T-64A's inherent unreliability.

The conclusion posits that the events of 1973 were less a reflection of the T-64A's objective failure and more a result of complex industrial, regional, and administrative factors within the Soviet defense industry. The study asserts that the subsequent historical narrative often relied on a "large-scale falsification" that overlooked the T-64A's achieved technical level and the similar reliability challenges faced by its successors in their early service years.

Pivotal 1973 – Part 1
© Andrei Tarasenko

On January 22, 1973, by order of the USSR Minister of Defense № 021, the T-64A and T-64AK tanks were officially adopted into service with the Soviet Army. Prior to this, the T-64A, which had been under development from 1961 to 1968, had already been in serial production for four years according to the decree of the CPSU Central Committee and the USSR Council of Ministers dated May 20, 1968, № 360-137.

In 1972, 15 units of the 172M model with the V-46 engine underwent field trials, followed by additional testing in various climatic zones. These trials ultimately led to the adoption of the T-72 tank by the Soviet Army through the CPSU and USSR Council of Ministers decree of August 7, 1973, № 554-172, and the USSR Ministry of Defense order of December 15, 1975, № 217.

An attempt to justify the adoption of the T-72 was made in a letter from the Commander-in-Chief of the Ground Forces, Marshal of the Soviet Union I. I. Yakubovsky, dated December 17, 1973, № 202/008. The letter listed seven structural deficiencies of the T-64A and concluded that organizing production of this tank at factories other than the Malyshev Plant was impractical. This correspondence effectively ended plans for a single tank model across multiple industry plants and shaped Soviet tank development for decades.

This article presents arguments from various parties leading up to this decision, including the Ministry of Defense, the leadership of the Malyshev Plant, and the Design Bureau for Machine-Building – KB-60. For a more historically accurate evaluation, we also refer to data published over a decade later in industry journals Vestnik Bronetankovoy Tekhniki and Voprosy Oboronnoi Tekhniki regarding reliability statistics of the T-64A, T-72, and T-80 tanks.

Tank Object 434, Prototype № 9

Ministry of Defense Perspective

The main materials are drawn from the report “On the Operational Use and Testing of the T-64 and T-64A Tanks” by the representative of the Chief of Tank Troops, Comrade Cherednikov, presented to the commission of Comrade Yakubovsky. Beginning of quote:

Ministry of Defense Perspective – Detailed Data

I. Tanks produced 1967–1969

1.      From 1967–1969, 180 tanks were modernized (120 at the Malyshev Plant and 60 at BTRZ-115) at a total cost of 17.9 million rubles.

2.      During field operations of 990 T-64 tanks between 1966 and 1970, there were over 2,400 failures and malfunctions of running gear, powertrain, weapons stabilizer, and other units and systems, including 1,800 failures within the warranty period ( 3,000 km ).

·        1,384 engines of series I–IV failed, including:

o       Over 300 engine hours (EH) = 246

o       200–300 EH = 375

o       100–200 EH = 444

o       Less than 100 EH = 319

·        From 1966–1973, the plant received 1,069 claims.

·        The MOD proposed that all T-64 tanks produced before 1968 be upgraded to T-64A standards (excluding weapons) during major overhaul. There were 1,230 such tanks, requiring 130 million rubles.

·        Due to significant differences in engines of series I–IV, it was economically impractical to repair them. Therefore, all engines produced before September 1969 were decommissioned. Total: 2,100 engines, valued at 5.5 million rubles.

II. T-64A Tanks

1.      Current tanks in service had the following mileage:

·        0–1,500 km = 53%

·        0–3,000 km = 84%

2.      Results of some tests:

a) Extended field trials of 65 tanks in 1969:

·        3 tanks in BVO, PrikVO, SibVO

·        2 tanks in TurkVO

·        50 tanks in five military districts (10 tanks each)

·        10 tanks in KVO (1970)

·        None of these tanks achieved reliable operation within the warranty period.

·        Failures: 41 engines (31 within 300 EH), 11 transmissions, 1,089 running gear components, 46 malfunctions of stabilizer, autoloader, and weapons. Low hull survivability observed (cracks).

b) Trials of 6 tanks in Chuguev, Borisov, and Tedzhen, July–August 1970 (6,500–7,000 km):

·        2 engines failed before 300 EH.

·        4 engines were found unsuitable for further use upon disassembly.

·        2 transmissions and several running gear components failed (total 68 failures).

c) October 1970–January 1971 trials of 10 tanks in PrikVO (≤300 EH, 6,000 km ):

·        178 malfunctions, including:

o       Engines = 2

o       Transmissions = 2

o       Running gear units = 173

d) June–November 1971 trials of 15 tanks:

·        7 engines, 18 transmissions, 20 running gear units failed.

·        No detailed report was provided to the commission.

e) Intensive operation of 171 tanks in 1971:

·        502 failures, including:

o       Engines = 15 (58 required repair)

o       Transmissions = 15

o       Road wheels and drive sprockets = 13

o       Rollers and idlers = 20

o       Track assemblies = 15

·        Engine system failures = 166

f) 30th Tank Regiment march, Oct 1972, Cherkassy ( 1,500 km ):

·        11 tanks did not reach the assembly area (8 water ingress in engine, 3 running gear damage).

·        Total forced stops: 64 (34 stuck, 30 component failures).

·        On 94 tanks, 314 malfunctions, including:

o       Transmissions = 3

o       Tracks = 22

o       Road wheels = 1

o       Rollers/idlers = 3

o       Shock absorbers = 20

g) Trials of 7 tanks, June–August 1972 ( 11,000 km , 518 EH):

·        141 failures, 54 malfunctions, including:

o       Transmissions = 2

o       Engines = 4

o       Fuel tanks, running gear = 19

·        One engine showed cavitation damage (through-cylinder hole).

h) Operational use in 1972:

·        604 failures, including 495 within warranty, 109 after warranty.

·        Tank systems failures:

o       Engine & systems: within warranty = 45, post-warranty = 28

o       Transmission & systems: within warranty = 43, post-warranty = 9 (pure transmission failures = 26, all within warranty)

o       Running gear: within warranty = 92, post-warranty = 35

i) Warranty trials – 3 T-64A tanks:

·        Tank 1: failures due to hydraulic stabilizer hose rupture, road wheel bearing, and hydraulic shock absorber.

·        Tank 2: hydraulic shock absorber failure, premature detonation of three shells.

Overall (1969–1973):

Despite 57% of tanks not reaching 1,500 km , total failures were:

j) Engines of Series V–VII

Current engine hours distribution:

·        ≤50 EH = 694

·        ≤100 EH = 376

·        ≤200 EH = 501

·        ≤300 EH = 208

·        300 EH = 268

·        Of 1,541 engines installed, 366 failed:

o       ≤100 EH = 36.6%

o       ≤200 EH = 28.6%

o       ≤300 EH = 13.3%

·        Power increase of +50 hp had no positive effect.

·        Engines could not operate on other fuel types.

k) Modernization of tanks produced 1969–1971

·        Due to unsatisfactory operation of 1969–1971 T-64A tanks, the MOD decided to modernize 610 tanks of the combat group: replacing engines, support rollers, radiators, preheaters, and conducting other measures.

·        In 1972, 350 tanks were upgraded at a cost of 8 million rubles.

Conclusion: T-64A required a series of major modifications. Key deficiencies included:

·        Short operational range

·        Small ammunition capacity and inconvenient use, especially if autoloader fails

·        Crew operation inconvenience

·        Low engine specific power

·        Susceptibility to fire

End of MOD perspective quote.

Malyshev Plant Perspective

T-64A – Mid-1971 Production, Welded Hull Sides

According to a letter from the Malyshev Plant Director O. Soich and Acting Chief Designer N. Shomin:

The Malyshev Plant, under the direction of the USSR Ministry of Defense (MOD) and the Ministry of Defense Industry (MODI), developed the T-64A based on the T-64 to further improve combat performance. The T-64A featured:

·        More powerful armament ( 125 mm gun instead of 115 mm )

·        Improved fire control and weapons stabilizer system

The State Commission, in accordance with the directive of the General Staff of the USSR Armed Forces dated May 17, 1967, conducted trials of these tanks. Its report (Inventory № 2599, 10 July 1968) recommended the T-64A for serial production and adoption into service, confirming the following tactical and technical characteristics (TTC).

By the decree of the CPSU Central Committee and USSR Council of Ministers dated May 20, 1968, № 360-137, the T-64A was placed into serial production at the Malyshev Plant, and its TTC was officially approved.

Serial production began in January 1969. The produced tanks fully complied with the approved TTC.

During serial production, the plant carried out extensive design and technological improvements to various components and mechanisms based on results from field trials and refinement of manufacturing technology.

To verify reliability and combat performance of the T-64A, 15 tanks were tested in 1971 across the following military districts: BVO, KKVO, PrikVO, SKVO, and TurkVO. A total of 183 design and technological measures were implemented on these tanks.

The trials covered distances of 1,000–1,100 km and confirmed high tactical, firepower, and maneuvering qualities of the T-64A, as well as its increased reliability. The majority of measures were effective and recommended for implementation in serial production.

The Commission concluded: “The T-64A tanks and 5TD engines passed the trials.” However, all identified deficiencies were scheduled for correction during serial production, in coordination with the MOD and MODI.

After reviewing trial results, Minister of Defense A. A. Grechko, acknowledging their positive outcomes, requested Minister of Defense Industry S. A. Zverev to increase production of the T-64A and implement corrective measures starting January 1, 1972.

In response, the plant developed a comprehensive program and, together with Military Unit №85 MOD, compiled a “List of Measures to Eliminate Deficiencies Identified During Trials of 15 Test Tanks.” A total of 84 measures were agreed upon and implemented within the required timeframe.

Verification of Reliability Measures

To verify enhancements in component durability based on the 1971 trials and to reduce maintenance requirements, in accordance with the directive of the Commander of the Ground Forces dated June 26, 1972, seven T-64A tanks underwent testing in KKVO from July to October 1972.

·        Tests covered a total distance of 11,000 km as per program requirements.

·        All major components, except experimental engines, demonstrated compliance with expected service life.

Additionally, accelerated operation and military exercises of large numbers of tanks were conducted in units between 1970–1972:

Testing and trials of T-64A tanks with 5TDF V-series engines in various climatic conditions. Note: Minor discrepancies exist in the number of tanks reported in various slides and texts.

Summary of Reliability Enhancements

Between 1967–1975, the T-64A underwent extensive, comprehensive testing under diverse road and climate conditions across BVO, KKVO, PrikVO, ZabVO, TurkVO, LVO, and ZakVO.

·        A total of 1,246 tanks participated in factory, joint, and field exercises, accumulating over 1.6 million km and 80,000 engine hours.

·        Tests were conducted year-round.

·        The plant, in cooperation with industry institutes, MOD specialists, unit commanders, and technicians, implemented extensive design, mechanism, and equipment improvements to increase reliability and service life.

Between 1970–1973:

·        242 major structural improvements implemented

·        Approximately 1,000 technological upgrades applied

·        Improvements affected nearly all major tank systems and allowed:

o       Increased durability of running gear (road wheels, idlers, tracks, drive sprockets, support rollers, hydraulic shock absorbers)

o       Enhanced hull and turret protection (fully stamped side plates, coaxial sight tube)

o       Reliable operation of the autoloader (MZ)

o       Greatly improved reliability of powertrain and engine systems (two-stage air cleaner, improved cooling system, oil preheating, improved hose fittings, reinforced fuel tanks)

o       Increased durability of side transmissions (reinforced pump drive, dual-mass system, increased disk quantity, upgraded disk materials)

o       Effective fire suppression system, improved communications

Number of failures per tank per 1,000 km , based on test results, 1969-1972.

Results:

·        Reliability improved from the 1969–1970 trials of 50 tanks to the July–October 1972 trials of 7 resource tanks:

o       Within warranty: 9× improvement

o       Over full service life: 7× improvement

Warranty Test Results:

·        Tank №1 (Feb–Mar 1972, Unit 68054) – 14 defects identified

·        Tank №2 (June–July 1972, TurkVO) – 4 defects

·        Tank №3 (Dec 1972–Jan 1973, ZabVO) – 1 defect

·        Based on operational experience, the plant extended the warranty to 4,000 km from January 1, 1973 (previously 3,000 km ).

Combat Performance Upgrades – T-64AM

Alongside reliability improvements, work was conducted to enhance combat capabilities, resulting in the T-64AM variant.

Measures included:

·        Upgraded armament, fire control, and stabilization systems

·        Lessons learned from field trials and accelerated exercises implemented

·        Enhanced mobility, engine reliability, and armor survivability

Minister of Defense Order №021ss (Jan 22, 1973):

·        The T-64A was officially adopted into Soviet Army service four years after serial production began

·        Enhanced features approved included:

o       Anti-aircraft machine gun

o       Integrated self-entrenching dozer

o       Mine plow capability

o       Command variant T-64AK based on the line tank

Production and Implementation Challenges

·        For over four years after the CPSU and Council of Ministers decree, tanks were produced according to drawings not approved by the Interdepartmental Commission (MVK).

·        Serial production according to MVK-approved documentation was intended from July 1, 1971, under Contract T-984 for 1971 deliveries.

·        MVK review by the customer was delayed until March 1973.

·        Lack of approved measures and deadlines led to isolated technical decisions with arbitrary completion timelines.

Regarding MOD Inspection Unit №85’s comments on delayed implementation:

·        Between 1969–June 1975, over 240 major structural modifications were introduced to further improve quality and reliability

·        Several improvements remained pending due to technical complexity, delaying implementation in serial production

·        Some points (№ 2, 5, 8, 10, 11) were re-raised by MOD Unit №85, despite prior resolution in August 1972 with Tank Troops Chief A. Kh. Babadzhanian

·        Certain measures (detachable tray and cab with extended transition zones, 3EZ-11 system, removable radiator manifolds) were not yet in serial production due to MVK decision delays

·        Inspection Unit №85 repeatedly demanded duplicative checks, causing additional delays

Main technical characteristics of the T-64A and T-64AK tanks at the time of adoption into service

In the intensive and demanding work of the design bureau and the plant on refining and perfecting the tank, preparing production, and implementing thoroughly tested design measures into serial production, additional difficulties arose. These were related to the fact that for more than four years after the CPSU Central Committee and USSR Council of Ministers decree on serial production, tanks were manufactured according to design and technical documentation that had not been approved by the Interdepartmental Commission (MVK).

Production of T-64A tanks according to MVK-approved drawings and technical documentation was planned to start on July 1, 1971, under Contract T-984 for delivery of T-64A tanks in 1971. However, the MVK approval process by the customer was delayed and was only conducted in March 1973.

The absence of reviewed and approved MVK measures, as well as the lack of deadlines for their implementation across all tank components, led to the emergence of various isolated decisions with technically unjustified timelines for completing these measures.

Regarding the remarks of Inspection Unit №85 of the Ministry of Defense (MOD) on the untimely implementation of joint decisions, the plant cannot agree with the accusation of reluctance or slowness in tank refinement, because:

·        From 1969 to June 1975, more than 240 major structural modifications were implemented, aimed at further improving the tank, enhancing its quality and reliability;

·        Indeed, alongside the implementation of a large number of improvement measures during serial production, there remained a number of issues regarding further enhancement of tactical and technical characteristics and elimination of deficiencies. Due to technical difficulties, these issues have not yet been resolved, and the implementation timelines for corresponding measures in serial production were postponed.

These issues are reflected in the MVK decisions and are included in the work plan of the design bureau, the plant, and other organizations.

·        Some issues (№2, 5, 8, 10, and 11) are again being raised by MOD Inspection Unit №85, despite the fact that these issues had been resolved by a decision agreed on August 17, 1972, with the Chief of Tank Troops, Comrade A. Kh. Babadzhanian, and no remarks were received from the troops regarding them;

·        A number of measures (detachable tray and cab with expanded transition zones, 3EZ-11 system, radiators with removable manifolds, etc.) have still not been introduced into serial production solely due to MOD Inspection Unit №85 not taking independent decisions.

At the same time, while executing the agreed scope of inspections, MOD Inspection Unit №85 continues to issue new, progressively increasing requirements, ultimately demanding duplication of inspections by other organizations and leaving decision-making to the customer’s management;

·        There have been prolonged delays in coordinating design orders with MOD Inspection Unit №85 for a number of measures, e.g., the introduction of a turret with ceramic filler, 3EZ11-2 system. Due to MOD Inspection Unit №85’s refusal, the design orders were only approved at the MVK level.

Quality claims accepted by Malyshev plant. 1970-1973.

End of Malyshev Plant perspective.

Summary of Part 1

Between 1969 and 1973, the T-64A tank underwent extensive and comprehensive testing, including field operations, regimental and divisional exercises, resource trials, and serial production use. In total, 1,246 tanks were involved, accumulating over 1.6 million kilometers and 80,000 engine hours. During this period, failures occurred primarily in engines, transmissions, running gear, weapons, electrical systems, and communications equipment. Early series engines (V–VII) exhibited significant early failures, with 36.6 percent failing within the first 100 engine hours, 28.6 percent between 101 and 200 hours, and 13.3 percent between 201 and 300 hours.

The T-64A’s operational range on unpaved roads was between 280 and 350 kilometers without additional fuel drums and 400 to 440 kilometers with drums installed. Engine and running gear improvements, along with design modifications, significantly increased reliability by 1972–1973. The warranty mileage was raised from 3,000 to 4,000 kilometers , and reliability within the warranty period increased ninefold, with a sevenfold increase across the full service life compared to early 1969–1970 trials.

Through systematic efforts by the Malyshev Plant and the design bureau, measures such as additional fuel tanks, strengthened running gear, improved transmission, enhanced engine maintenance systems, fire suppression upgrades, and improved communications were implemented. These actions gradually brought the T-64A to an acceptable level of operational reliability by the time it was officially adopted into service in 1973. Nevertheless, the remaining structural and operational limitations justified the parallel development of the T-72, which complemented the T-64A and ensured further strengthening of the Soviet Army’s armored capabilities.

In summary, by 1973, the T-64A had achieved a satisfactory level of reliability through intensive testing and modernization, but its limitations prevented it from becoming the sole main battle tank, shaping the Soviet approach to parallel tank development.

Yakubovsky Letter – A Turning Point in Soviet Tank Development

Part 2

The letter dated 17 July 1973, № 202/009, from the head of the 7th Main Directorate, M. I. Maresev, addressed to A. A. Morozov and O. V. Soich, titled “On the Remarks of the Commission on the T-64A”, which presented the conclusions of the commission of the Commander-in-Chief of the Ground Forces, Marshal of the Soviet Union I. I. Yakubovsky, represents a pivotal historical moment in Soviet tank building. These events determined the future development path involving the parallel development of the T-64A, T-72, and later the addition of the T-80.

Quote:

“The work conducted by the Malyshev Plant to refine the tank during serial production and modernization did not fully eliminate the remarks identified during trials, field operations, and exercises, nor did it address the structural deficiencies of the T-64A, which include:

1.      Insufficient operational range, which does not allow daily marches of 300–350 km without refueling;

2.      Placement of the ammunition load allows only 30 rounds out of 37 to be fired in combat without stopping the tank;

3.      Difficult access for the driver to the fighting compartment;

4.      Insufficient cross-country mobility on soft terrain;

5.      Shallow ford-crossing capability;

6.      Possibility of fires in the powertrain compartment;

7.      Difficulty replacing track links and towing the tank without tracks.

Required reliability for a number of units and assemblies has not yet been achieved.

During exercises of the 23rd Tank Division, equipped with tanks produced in 1972–1973, with mileage of 900–1,200 km, failures and malfunctions occurred in the engine and its systems, powertrain, running gear, and instruments.

To date, work to increase engine power and ensure operation on various fuel types has not been completed.

Based on the above, organizing serial production of the T-64A at other plants in the industry, apart from the Malyshev Plant, is impractical.

I ask you to take measures to ensure the prompt elimination of the deficiencies of the T-64A, paying particular attention to the deficiencies listed in the commission’s conclusions of Comrade I. I. Yakubovsky.”

End of quote.

Note: The seven points above, highlighting the structural deficiencies of the T-64A and serving as justification for adopting a second type of tank with similar characteristics, deserve special attention. Regarding these points, memoranda were sent to the Ministry of Defense Industry (MODI) by Chief Designer A. A. Morozov. In addition, comparative trials were conducted that confirmed the obvious inaccuracy of Yakubovsky’s statements.

Below is the content of A. A. Morozov’s memorandum on work performed to eliminate the deficiencies of the T-64A identified by Yakubovsky’s commission. Author’s notes are in italics.

1. Insufficient operational range, not allowing daily marches of 300–350 km without refueling

·        The operational range of T-64A tanks on unpaved roads was 280–350 km without additional fuel drums and 400–440 km with additional drums. These values were taken from the 1972 test report of seven tanks.

·        172M – Operational range on medium-cross-country terrain at an average speed of 25 km/h is 340 km , and 460 km with fuel drums, with the drums integrated into the fuel system. This allows planning daily marches of 300–350 km without refueling.

·        According to trials of six tanks in 1971 for Object 219, the operational range, depending on road conditions, averaged 270 km , and with additional drums, 315 km , which does not provide a daily march of 300–350 km without refueling.

·        However, experience shows that by maintaining higher speeds, the number of stops during marches can be reduced, allowing a regiment to refuel every three hours.

·        To increase the T-64A operational range, from 1 April 1975, additional fuel tanks were installed on the right side of the hull above the tracks, increasing the carried fuel by 200 liters . The total fuel capacity became 1,960 liters , allowing continuous operation for 16–16.5 hours, which ensures a daily march.

Note: This value is 20 km lower than the maximum achieved during T-72 trials in 1972. Critics of the T-64A referred to minimal and maximal ranges depending on terrain conditions; for Object 172, maximum values are cited.

·        Based on publication data [1], claims about insufficient operational range of the T-64A, especially in comparison with the T-80, appear completely unfounded

Entry in A. A. Morozov's diary dated November 1, 1973: T-64A paved the way for all design bureaus. I officially declare that if I am not given the opportunity to work on modernization, I request to be dismissed from the position of head of the design bureau.

2. Ammunition Placement Allows Firing 30 Rounds in Combat Without Stopping the Tank

The T-64A carries a total ammunition load of 37 rounds, which are stored as follows:

·        28 rounds (76%) are located in the autoloader mechanism and can be used in combat without any limitations;

·        2 rounds (5.4%) are stored in the turret stowage and can be fired without stopping the tank, but only when the gun is placed on the hydro-stop;

·        7 rounds (18.9%) are stored in a rack within the driver’s compartment. These rounds can be transferred to the autoloader mechanism without the crew leaving the tank, but only after a brief stop of the vehicle, since the driver participates in this operation.

It is important to note conclusions based on tests of 15 Object 172M tanks in 1972. Among the identified shortcomings, it was noted that 60% of the rounds (22 rounds) were in the autoloader, which could reduce combat effectiveness. Reloading the autoloader from the non-mechanized stowage requires ceasing fire and turning the turret approximately 45° from the 30–00 firing direction during the reload. When firing manually from the non-mechanized stowage, the reload rate is 1.2–2 minutes per round, including turret rotation and temporary loss of the target.

Author’s note: It is evident that the same shortcomings were sometimes emphasized and sometimes overlooked. For example, the 1972 test report of Object 219, equipped with an autoloader similar to the T-64A, states: “With 75.6% of the tank’s ammunition in the mechanized stowage, the effectiveness of gunfire is increased, while the 9 rounds in the non-mechanized stowage can be used during firing from stops at a rate of 0.5–0.8 rounds per minute.”

As an illustration of this situation, a diary entry by A. A. Morozov made in 1973 is worth citing:

They equated a tank with a market (whatever the wife wants, they will buy). They believe everyone and everything, but not us. 

3. Difficult Access for the Driver to the Fighting Compartment

With the introduction of a 7-column autoloader instead of the 10-column design in November 1972, the probability of needing to rotate the autoloader manually was reduced by 1.4 times, which improved the conditions for the driver to access the fighting compartment.

Note: It is also worth noting that the overall layout of the fighting compartment, with an isolated fighting cabin, was designed so that all major units and assemblies were accessible from the driver’s or engine compartment, rather than from the fighting compartment itself. This design feature was already presented in the technical project of Object 432 and was acceptable to both the customer and the leading industry institute, VNII Transmash [2].

Comparative data on autoloaders of T-64A and T-72 (172M)

1 – number of automated rounds,

2 – rate of fire,

3 – rate of fire if loaded in manual mode,

4 – reliability in extreme dust conditions

5 – required operations

6 – case extraction

7 - Ensuring the mechanism works when the tank bottom is bent (mm) 

8 – possibility of use with guided missile “Kobra”

10 - labor costs for manufacturing man-hours

From the Memoirs of A. I. Mazurenko, a Developer of the T-64A

For us, the developers of the autoloader mechanism, it resulted in a new “fundamental” deficiency, called the “lack of crew passages.” At the time this new problem arose, the refinement of the autoloader based on remarks from the large series of field trials was practically complete. As the person responsible for this mechanism, I was firmly convinced that no one could devise anything better within the layout constraints of our tank.

When the first information appeared about the new autoloader of the Nizhny Tagil Uralvagonzavod, I did not take it seriously, because its shortcomings, compared to our mechanism, were obvious. First of all, by placing the mechanized ammunition rack under the floor of the crew compartment, they lost six rounds, reducing the automated ammunition load by 23%, which from a military perspective should have been completely unacceptable. The new loading scheme became a two-stroke process (first the projectile was loaded, then the charge in a second movement), which undoubtedly reduced the rate of fire and eliminated the possibility of manual backup. The spent tray could not be placed in the tray by design, so it was ejected outside through a special hatch at the rear of the turret, naturally compromising the sealing of the fighting compartment and preventing firing in radiologically contaminated areas, which also should have been unacceptable for the military.

However, it turned out that despite this “bundle” of deficiencies, the Tagil tank had a clear “advantage” compared to the T-64A – the ability for crew members to move between the fighting compartment and the driver’s compartment in emergency situations. The military, forgetting about the deficiencies, latched onto this contrived “advantage” with a death grip. We had to urgently save our tank and find a design solution for the “passage.” Of course, we found a solution, slightly complicating the tray design and making it detachable, so that the vertical part of the tray could be removed if necessary to clear the crew’s evacuation path.

4. Insufficient Cross-Country Mobility of the T-64A on Soft Ground

The cross-country mobility of tanks on soft terrain is determined by the average specific ground pressure of the tracks. The specific ground pressure of the T-64A is 0.83 kg/cm², which is comparable to the specific ground pressure of well-known domestic and foreign medium tanks.

Specific ground pressure on soil:

·        Object 172M – 0.83 kg/cm²

·        T-34 – 0.83 kg/cm²

·        T-54 – 0.90 kg/cm²

·        Leopard – 0.84–0.87 kg/cm²

·        Chieftain – 0.84–0.97 kg/cm²

·        M-60 – 0.77 kg/cm²

The claim of reduced cross-country mobility of the T-64A on soft ground was not supported by any comparative trials with other medium tanks (T-62, 172M, etc.). Such comparative tests were conducted by VNIITM in April–May 1974.

The test results of the T-64A, T-72, Object 219, and T-62 tanks completely refuted this claim. According to the trials, the T-64A demonstrated the best mobility in swamps with depths of 85–120 cm and 120–150 cm, compared to the T-62, T-72, and Object 219.

During repeated crossings of a swamp 85–120 cm deep, the T-64A did not become stuck. Object 219 experienced one immobilization, the T-72 had two, and the T-62 had five. During a single crossing of a swamp 120–150 cm deep, the T-64A did not become stuck, while the T-62, T-72, and Object 219 did.

Note:

A major strength of the T-64A running gear and its modifications is excellent cross-country mobility. The shape of the track shoe’s contact surface and the holes in it not only reduce weight (decreasing idle rolling losses), improve track self-cleaning, but also enhance traction: internal forces between soil particles beneath and above the track are effectively utilized. This provides an additional 15–25% of tractive effort, while the remaining 50–65% is realized through the track’s soil-engaging cleats (spurs).

The T-64A maintains mobility on swampy terrain, and its running gear shows high tolerance to clogging, beyond which mobility is lost.

Its tracks ensure adequate self-cleaning from soil [3] and reduce the rolling resistance of the road wheels along the track path.

Design studies to improve T-64A cross-country mobility showed that further improvement could only be achieved by significantly reducing the tank’s specific ground pressure, which is impossible without a major redesign of the running gear (widening or lengthening the tracks) and, consequently, a substantial reconfiguration of the entire tank. It is worth noting that the customer required the T-64 designers to achieve a ground pressure of 0.50 kg/cm², and such work was implemented using removable track wideners [4].

5. Shallow Ford-Crossing Capability

Starting April 1, 1975, the T-64A was equipped with permanently installed valves, a quick-install exhaust pipe, a cover closing the air intake to the AK-150 compressor controlled by the driver, and peripheral louvers above the air cleaner also controlled by the driver. These modifications increased the maximum ford-crossing depth from 1.0 m to 1.8 m .

 6. Risk of Fires in the Engine-Transmission Compartment

Three cases of fire in the engine-transmission compartment (ETC) occurred during exercises in 1973 (Ovruch) and were linked to violations of operational rules (fueling into the ETC instead of the tank through the water ejection hole from the rear pump, a barrel of another tank penetrating a drum, fuel entering the ETC during drum refueling). None of these incidents were publicized. The probability of fuel entering the ETC from the ejector box during drum penetration was reduced with the introduction of valves in the ejector box as part of the “Ford” system (from September 1974).

Fire safety in the ETC was ensured from January 1972 through measures to improve the reliability of connections in the fuel, exhaust, and oil systems:

·        Improved sealing of hydraulic system hoses for the transmission with high-temperature sleeves.

·        Additional fastening of the oil supply line to the injector distributor.

·        More flexible compensators at the junctions of the curved pipe with the engine collector and turbine inlet.

·        Improved attachment of insulation for the curved pipe and engine exhaust collector.

·        Design and technological improvements for high-pressure pipes and the fuel supply line from the filter to the pumps.

·        Protective covering of basalt fiber for the exhaust duct.

7. Difficulty of Replacing Tracks and Towing the Tank Without Tracks

Replacing tracks in soft terrain (deep mud, swamp, sandy soil), as well as towing the tank without tracks in these conditions, is labor-intensive for all tracked vehicles, and the T-64A is no exception. Installing tracks on soft ground, according to VNIITM trials in April–May 1974 on T-64A, T-72, and Object 219, was similar for all tanks. The towing effort for the T-64A without tracks is higher than for other tanks.

The narrower road wheels of the T-64A, compared to the wider rubberized wheels of other medium tanks, somewhat complicates towing operations; however, the feasibility of these operations has been repeatedly confirmed both in unit service and by special tests conducted by enterprise p/o A-3530.

Equalizing the dimensions of the T-64A road wheels to reduce ground pressure to the level of tanks with wider, rubberized wheels is not feasible, as it would increase wheel weight and overall tank weight by approximately two tons, as shown by experience with the 172M and Object 219.

Note: Many years later, in 1990, during work on completely different vehicles, tests were conducted to check the possibility of evacuating Objects 434 and 478B (running gear similar to Object 219) without tracks and installing tracks on low-load-bearing soils. Findings from the report:

Evacuation of a vehicle stuck in loose sand without tracks using another identical vehicle was impossible due to the latter’s slippage. Under these conditions, evacuating Object 434 required 20–23 tons of force, Object 478B – 15.5–17.5 tons.

Installing tracks on loose sand for Objects 434 and 478B using Object 454 with a winch was possible. For Object 478B, approximately 24% less effort was required to lay the track. The preparation and installation time for each vehicle in these conditions was about 1.5 hours.

Without towing vehicles, track installation after removal on loose sand is done by undercutting all road wheels and dragging the track under them.

Another issue was deformation of the autoloader conveyor during collisions. In T-64A units, there were cases where the M3 conveyor, loaded with rounds, deformed during emergency collisions of tanks at speeds of 30 km/h , causing malfunctions in the autoloader mechanism.

To prevent M3 conveyor deformation even during tank collisions, from October 1972, a conveyor with strength characteristics 25–70% higher (depending on the section) than the previous version was introduced into serial production. In 1973, additional measures were developed for serial production, increasing the stiffness and strength of loaded conveyor elements by more than 2 times.

The 5TDF Engine and Its Reliability: A Lost Opportunity

Part 3

The Part 3 and Part 4 of this work provides a detailed historical and technical analysis of the development, testing, and operational reliability of Soviet tank engines from the late 1960s through the 1980s, with a focus on the 5TD series (5TD, 5TD-3, 5TDF) installed in the T-64A, and comparisons with the V-46-6 engine used in the T-72. It traces the initial testing, production, and military trials of engines from 1969–1973, showing systematic improvements in durability, performance, and fuel efficiency. Early engines underwent guaranteed and field tests, with progressive increases in service life from 300 hours to 700 hours, and the introduction of multi-fuel variants. Problems such as starter-generator failures, piston group wear, turbocharger issues, and fuel system defects were identified and effectively mitigated through over 850 engineering improvements, extensive testing, and adoption of robust design solutions.

The article documents the development of higher-powered engines, including the 6TD and 6TDF (1000–1250 hp), and their integration into upgraded T-64A and T-80 prototypes, resulting in improved tank mobility, acceleration, range, and fuel efficiency. Comparative analyses of guaranteed and field reliability data show that 5TDF engines outperformed V-46-6 engines in the late 1970s, disproving widespread claims of T-64A unreliability. The study highlights how administrative delays, conflicting requirements, and competition between design bureaus and factories affected development timelines, while proper engineering interventions steadily enhanced engine reliability. Finally, it emphasizes that the T-64A’s powertrain, properly developed, was at least equal to, and in some aspects superior to, later Soviet tanks such as the T-72 and T-80, contrary to popular narratives in both technical and popular literature.

On the Refinement of the 5TDF Engine

The 5TDF engine, which was developed and introduced into serial production, initially demonstrated insufficient stability and reliability during the early period of service, giving rise to justified complaints from field units toward the manufacturing plant.

During 1968–1969, the plant developed and implemented a series of design and manufacturing improvements, which significantly increased engine reliability and service life. From this point onward, production of the Series V engines began.

Accelerated trials of 50 tanks conducted in 1970 demonstrated that the average service life of Series V engines reached 300 operating hours.

To verify the effectiveness of the new design measures introduced based on the results of the 50-tank trials, interagency trials of 15 tanks were conducted between June and October 1971 in various regions of the country.

During these trials, the engines accumulated 470–500 operating hours. In view of the positive results, the commission’s conclusion stated:

“The tank and the engine have successfully passed the trials; however, the deficiencies identified during testing must be eliminated during serial production within timeframes agreed upon between the plant and the customer.”

The regional engineer, N. A. Nadomnikov, signed the report without reservations.

Results of field tests of 5TDF showing improvements of reliability form 1969 t o1973.

Operational Summary on 5TDF Engines of All Series as of 1 May 1973

The verified design improvements to the engine, tested on 15 reference tanks and approved by a joint decision dated 11 December 1971, were implemented in serial production within the agreed timeframes. This enabled the plant to produce engines with a warranty life of 300 operating hours and a service life of 500 operating hours when installed in a tank.

The effectiveness of the implemented measures is confirmed by the results of field operation and warranty bench tests of the engines. The reports cited below indicate that the percentage of claims against the plant from field units decreased sharply. Whereas in 1969–1970 this figure amounted to 6.0% of the number of engines in service, in the first half of 1973 it was only 0.4%.

The increase of service life of 5TDF, 1969-1973.

Graph 1 – Average service life of 5TDF, Graph 2 – factory warranty.

In 1972, all ten engines completed the full warranty service life of 300 hours, and four of them operated for a double warranty period of 600 hours. Based on the results of the 1972 warranty bench tests and the results of field operation, the manufacturer increased the warranty period of the engine to 400 hours starting in January 1973.

In 1973, warranty bench tests were conducted on two engines, which completed the extended warranty period of 400 hours with a power loss of 2.2–2.6%, compared to the allowable power loss of 5%.

To confirm the extended warranty period under operational conditions, ten tanks are being tested in the Lugin area. The accumulated engine operating time is 200 hours. The tests are ongoing, and there are practically no remarks regarding the engine.

During the period 1968–1973, a number of military exercises involving large numbers of tanks were conducted in field units, including marches of up to 1,500 km . The results of these marches are presented below.

During these exercises, the 5th-series engines demonstrated sufficient reliability and ensured the accomplishment of the tasks assigned by the command.

An analysis of the exercise results shows that for engines manufactured up to 1969 (prior to the 5th series) there were 0.13 failures per engine per 1,000 km of mileage, whereas for engines of the 1972–1973 production years the number of failures decreased by more than three times and amounted to 0.037 failures.

The increase of 5TDF reliability (1968-1972).

In March 1973, the interdepartmental commission (MVK) approved the design and technical documentation for the engine for series production with the designation “B,” which indicates production stability and the possibility of transferring the design and technological documentation for engine manufacture to other plants. The deadlines for implementing the measures approved by the MVK are being strictly observed by the plant.

At present, the plant continues work aimed at further increasing the engine’s reliability and service life to 700 hours. Three engines have completed 700 hours on the test stand, two engines are undergoing trials installed in a vehicle, and additional measures to ensure a 700-hour service life are being implemented.

Work on the 5TD-3 engine with a rated power of 750 hp has essentially been completed. Design and testing work is under way on a 900 hp engine: two 900 hp engines have accumulated 450–600 hours on the test stand. One engine is being tested in a tank and has already accumulated 170 operating hours. Multifuel versions of the 5TDF and 5TD-3 engines have been developed. Beginning in July, production of the 5TDF engine in a multifuel version will commence (diesel fuel, gasoline, kerosene, and their mixtures).

It should be noted that during work under contractual topics and in the execution of joint decisions, schedule slippages did occur. Some of these delays were mainly due to the need to resolve technical difficulties encountered.

A significant portion of the schedule delays is explained by the fact that deadlines were set by the customer without regard to the feasibility of resolving certain technical issues within those time frames. In a number of cases, the impracticality of the deadlines was obvious, yet they were accepted by the plant out of necessity in order to avoid production stoppages; an example is the design bureau work on increasing engine service life to 500 hours.

It must also be noted that the customer itself did not always demonstrate sufficient discipline or interest with respect to meeting deadlines.

During the period 1969–1972, the design bureau and the plant implemented more than 850 design measures into production aimed at increasing engine reliability and service life, as well as improving manufacturability, and these measures naturally produced positive results.

Work of the design bureau on eliminating engine shortcomings.

Report on the work carried out by the plant to refine the 5TDF engine, uprate it to 750 hp (5TD-3), and develop a multifuel version. Submitted on 22 June 1973 to Plant Director O. V. Soich by Chief Designer of the KhKBD L. L. Golints.

Excerpt:

In the course of engine refinement, joint decisions provided for the elimination of a number of engine shortcomings. The status of work on the main shortcomings is outlined below.

1.      Failure of the SG-102 starter-generator drive.
Failures of the SG-10 are of a sporadic nature and amount (relative to the number of engines in service) to: 1970 – 0.16%, 1971 – 0.050%, 1972 – 0.095%, 1973 – 0.08%. The cause of SG-10 drive failures is violation of operating instructions, as confirmed by failures of the ratchet clutches recorded by a commission during joint tests under close observation. This has also been confirmed by specially conducted studies.

The design bureau has developed and tested four drive design variants. Tests showed that these variants are more reliable than the production version and could reduce the number of failures by half, but they would not provide a sufficient margin of reliability for all cases of instruction violations in the troops. At the same time, implementation of these variants would require major production reconfiguration. Therefore, the design bureau and the plant are currently conducting extensive work to develop a more reliable variant in order to resolve the issue within the timeframe established by the MVK—the fourth quarter of 1973.

2.      Ensuring reliable operation of the piston group.
In 1972, all 10 engines completed the specified warranty period. Reliable operation of the piston group is also confirmed by operating experience. The plant has no claims regarding the piston group for engines produced in 1972–1973.

Reliable operation of the piston group is specifically noted in the test report for 15 control tanks. Paragraph 5 of the conclusions states: “The piston group operated normally during the tests. Oil consumption became stable.”

Ignoring these facts, and at the insistence of customer representatives, the MVK did not approve the piston group for a service life of 40 stages, citing the fact that during warranty bench tests in 1972, ring failures occurred on the first two engines (at 310 and 340 hours), and did not take into account that, as a result of measures adopted in serial production, the operability of the piston group was confirmed by subsequent warranty tests totaling 600 hours.

As evidence of unreliable piston group operation, customer representatives Ladonnikov and Sarychev cited engines Nos. 7168, 7040, and 7026, although:

– Engine M02-7168 operated for 520 hours on the test stand during warranty tests (120 hours beyond warranty);
– Engine P04-7040 experienced piston group failure while operating in an overturned tanker;
– Engine M04-7026 was not inspected (metal filings were found at the MCF when the tank was returned to Plant No. 115).

The inconsistency of these examples indicates a superficial approach by military acceptance management to the analysis and evaluation of engine performance.

3.      Reliability of the supercharger and its drive.
Analysis showed that the supercharger design reliably обеспечивает a service life of 700 hours in operation.

– On engines produced in 1972–1973 under troop operating conditions, there were three cases of supercharger impeller failure. A warranty claim was filed for only one engine—P08ET7199 (53 operating hours). The cause is under investigation.
– On engine P09ET7320, impeller failure occurred after 2 hours of operation. The cause was the ingress of a foreign washer into the supercharger (act signed by Sarychev, Military Acceptance 4766).
– On engine P01ET7063, impeller failure occurred after 233 hours of operation. No warranty claim was filed because, when replacing the idler assembly, unit personnel did not install the linkage blocking sensor that protects the impeller from overspeed.

4.      Increasing reliability of the water pump.
A new-design water pump (combined with the gearbox) has been installed on the engine since February 1972. There were no warranty claims in 1972 or the first half of 1973.

Measures for further increasing water pump reliability have been developed, tested, and will be implemented in serial production within the MVK-established timeframe—the third quarter of 1973.

5.      Increasing reliability of sealing of injector bodies and starting valves.
During 1972 and the first half of 1973, no warranty claims were received.

To further improve sealing reliability, in accordance with an MVK decision, radial sealing with rings made of IRP-1287 rubber will be introduced from 1 July 1973.

6.      Increasing reliability of sealing between the fuel pump housing and the block.
Throughout engine operation, there have been no warranty claims. On some engines during accelerated tests at high operating hours, slight sweating at the joint was observed. The customer representative’s claim that this defect occurs during all types of tests is subjective and unfounded.

To further improve sealing reliability with increased service life, a new IRP-1287 rubber seal will be introduced from 1 July in accordance with the MVK decision.

7.      Ensuring stability of engine parameters.
As a result of a комплекс of work carried out in 1969–1971, power losses during warranty-period engine tests were significantly reduced. During warranty tests in 1972, only two engines exhibited power losses exceeding permissible limits (above 4%).

In 1973, the MVK established allowable power losses of 5% during bench tests due to the increase of the warranty service life to 400 hours.

Ensuring reliable operation of the ADU-2S control unit.
Since January 1972, the ADU-2S has been installed at the rear of the vehicle. Since that time, warranty claims have ceased.

To further improve ADU-2S performance, a new separator design will be introduced from July 1973 by MVK decision.

Ensuring reliability of sealing between exhaust manifolds and inlets.
There have been no warranty claims related to this sealing assembly during operation. According to the instructions, leakage at the joint is eliminated by tightening.

To further improve sealing reliability, a new design of gas-sealing ring will be introduced into serial production from 1 July 1973 in accordance with the MVK decision.

10.  Increasing reliability of fuel filters.
Since 1 January 1972, a paper fuel filter has been introduced into serial production. No warranty claims have been received during the period under review.

To further improve fuel filtration and increase the reliability and service life of the fuel system, a cardboard filter element has been developed and has passed bench and field tests. The new cardboard filter has been approved by MVK decision and will be introduced into serial production from October 1973.

11.  Regarding seizure of fuel pump plunger pairs.
Seizure of fuel pumps occurred on engines Nos. P08-7151 and P05-7182 at operating times of 240–296 hours respectively. The nature of the defect was circumferential seizure of the plunger against the sleeve. The seizure is evidently related to the presence of water in the fuel.

During exercises, there were six cases of plunger pair seizure. There are grounds to assume that the seizures were associated with the use of low-quality fuel, since on two vehicles the filters were found to be clogged with dirt and fibers.

Work to ensure multifuel capability of the production engine

In accordance with VPK Decision No. 195 of 6 September 1967, the plant was required to carry out work to provide multifuel capability for the 5TDF engines and T-64 tanks, with completion scheduled for the fourth quarter of 1968. Execution of the main work was delayed until June 1970 due to failure to meet the deadlines for construction of multifuel test stands for testing the 5TDF engines, caused by the absence of the necessary funding for capital construction. By VPK Decision No. 30 of 4 February 1970, the completion deadline was postponed to the second quarter of 1971.

Over eleven months, from August 1970 to May 1971, a multifuel modification of the 5TDF engine was developed that surpassed all existing domestic counterparts in its performance characteristics. The engines successfully passed interdepartmental bench tests.

At the same time, factory trials of a multifuel T-64A tank equipped with a multifuel engine were conducted for a total of 300 hours without any remarks. Interdepartmental engine tests were delayed by two months because, at the insistence of the deputy commander of military unit 52682, tests were conducted on two identical engines (despite the availability of only one test stand) instead of one engine as stipulated by the contract. In addition, the final decision on whether to continue work on multifuel capability was made by the deputy commander of military unit 52682 with a delay of four months. Two T-64A tanks in the multifuel configuration were sent to military unit 68054 in March 1972.

Field 300-hour trials of two T-64A tanks were conducted by the general customer over a period of ten months (March–December 1972). The trials revealed a number of defects caused by operation of the tanks in high-altitude conditions (approximately 150 hours). Despite the positive results of the field trials, the conclusion of military unit 68054 and the decision of the deputy commander of military unit 52682 No. 562/3/09905 of 22 December 1972 declared the introduction of multifuel capability into series production to be inexpedient.

By VPK Decision No. 32-67 of 9 January 1973 and the decision of a meeting at the Ministry of Defense Industry on 24 April 1973, it was planned to:

– begin series production of T-64A tanks from 1 July 1973 with measures ensuring multifuel capability and elimination of defects associated with high-altitude operation;

– conduct repeat field trials of two T-64A tanks under the July program, after which a decision would be made on operating T-64A tanks produced from 1 July 1973 as multifuel vehicles.

Increasing the power of the 5TDF to 750 hp (engine 5TD-3)

During the development of the 5TD-3 engine, a number of difficulties arose related to finding ways to boost the engine and achieve parameters surpassing all known engines both domestically and abroad, as well as to solving fundamental problems involved in creating an even more powerful engine for prospective tanks of the 1975–1980 period.

Resolving these issues, as well as addressing the problems of increasing the service life and reliability of the base engine, led to certain delays in schedules.

However, the main issue lies in the fact that the customer is unwilling to acknowledge the results already achieved and the significant future potential for further increasing the service life of the production engine, improving its technical characteristics, and substantially increasing its power to 750–900 hp and beyond.

The technical design of the 5TD-3 engine was submitted to the customer on 29 November 1967. Despite the customer’s obligation to review the project and issue a conclusion within 30 days of receipt (in accordance with Clause 15a of the contract), the project remained under review for six months, which accordingly delayed completion of the first stage by half a year.

Similar delays occurred in the formalization of acceptance certificates for the second stage (five months), the third stage (one month), and the fourth stage (three to five months).

By letter No. 0392 of 27 June 1969, Comrade Ladonnikov suspended work on the project due to the absence at the plant of SG-15 starter-generators (although they were not manufactured by industry), the absence of agreed values for intake and exhaust resistance in the tank (even though tank trials were not предусмотрены under the fourth stage), and other reasons.

Permission to resume work was received from the Ministry of Defense only on 11 August 1969. By letter No. K/867605 of 6 March 1970, Comrade Ryabov suspended work on the fourth stage of the contract, citing the need to concentrate main efforts on refining the production engine.

Authorization to resume work on the fourth stage was granted only on 4 August 1970. In total, during execution of the first four stages from August 1967 to November 1970 (40 calendar months), the work was delayed by the customer for 22 months on various completely unjustified grounds.

The 5TD-3 engines tested upon completion of the fourth stage—Nos. 902E4172, 911E5606, and 911E5604—operated for 300, 380, and 500 hours respectively (with a specified service life of 300 hours).

Thus, by the first half of 1970, the engine service life and technical specifications specified in the project card had effectively been achieved. Despite the successful completion of the 4th stage with extensive 500-hour tests, the customer continued to delay the assembly and testing of engines during the 5th stage for various reasons. For example, engine No. L07V5077, which ran 470 hours on the test bench, and engines Nos. L10E6098 and NS7ET1104, which operated in the tank for 310 and 325 hours respectively with almost no issues, along with other engines, were not accepted by the customer for unjustified reasons. In total, during the 5th stage, 20 engines were manufactured instead of the 8 planned in the contract.

According to the joint decision of the USSR Ministry of Defense and the Ministry of Tank Industry No. 7/31690 dated 20 June 1972, interdepartmental bench tests of the engine were to be conducted in the 3rd quarter of 1972 for a service life of 300 hours (this work was not originally envisaged in the contract or subsequent decisions).

The interdepartmental tests began in September 1972 using three types of fuel: diesel, jet fuel, and gasoline. During testing on gasoline, the plant encountered certain difficulties. After 250 hours of operation (due to increased hourly fuel consumption on gasoline), the engine was returned to the plant for continuation of testing and determination of the cause of the increased fuel consumption. Overall, the engine ran 600 hours without any significant defects that would limit its further operation (including approximately 300 hours on gasoline).

Upon disassembly, it was found that the main reason for the increased hourly fuel consumption was coking of the fuel injector nozzles, caused by the absence of a fuel-bleed drill hole in the fuel pump of the second cylinder (a manufacturing defect).

Considering that in 1972–1973 long-term bench tests were carried out on six 5TD-3 engines, each running 600–1000 hours, and inspections after testing revealed no defects limiting the 700-hour service life, the plant agreed to increase the interdepartmental test duration to 400 hours instead of the 300 hours stipulated in the contract and was ready for interdepartmental testing. A corresponding telegram was sent to the commander of military unit 52682-K, Comrade Dikiy, on 25 May 1973.

Several reasons for the delays in work should be emphasized:

·        According to the contract, the plant needed to conduct factory tests of one engine in a tank; the plant conducted tests in two tanks over the specified service life with practically no issues, but the tests were not acknowledged by the customer.

·        The contract required the plant to conduct bench tests of one engine; the customer demanded tests of three engines, and the plant conducted them.

·        Interdepartmental tests were not envisaged in the contract; the customer demanded interdepartmental testing, and the plant agreed to carry it out.

Increasing the service life of the 5TD engine to 500 hours

In August 1964, Malyshev Plant prepared contract No. H2-295 with military unit 52682 to increase the 5TD engine service life to 500 hours. Due to significant disagreements between the plant and the customer regarding funding and the scope of work stages, the contract was only signed in December 1964 (Protocol K/1050630 of 23 December 1964, military unit 52682). Thus, conducting work to double the engine’s service life in the context of establishing serial production and an extensive design program gave the design bureau an unrealistically short period of one year. Such tight deadlines did not allow for sufficiently thorough research and design development, which ultimately resulted in engines being equipped with measures that were not fully verified for increased service life.

This situation was acknowledged by the customer, who adjusted plans and work schedules accordingly. In a letter from military unit 52682, No. K/867605 dated 6 January 1970, Comrade Ryabov noted: “Assessing the current situation, we consider that simultaneous work by the plant on refining the 5TD engine and fulfilling three contract tasks prevents it from focusing its main efforts on further development and ensuring reliable operation of the base engine.”

In letter 1 D/871872 of 4 November 1970, Comrade Dikiy stated that “it is advisable to conduct work to increase the guaranteed service life beyond 500 hours in the normal course during serial production.”

Accordingly, military unit 52682, considering the agreement of the Malyshev Plant, deemed it possible to close contract No. H2-295 for increasing the 5TD engine service life to 500 hours.

Significant increases in engine service life and reliability began in 1970 when serial production of the practically new 5th-series 5TD engine was mastered. Documentation for this engine was not signed by the customer and was only endorsed by the chief designer. However, it was the substantial groundwork laid in the 5th-series engine, along with the absence of restrictive contract constraints and micromanagement by the customer, that allowed the reliability and service life of the engine to increase sharply starting in 1970.

End of a qoute.

6TD Engine

Part 4

Object 476, 1976 version.

6TD engine technical proposal, 1960 and 1970 variants.

In parallel with the refinement of the 5TDF engine, the Central Design Bureau of Malyshev Plant continued the development of the 6TD engine with a power output of 1,000 hp. Since 1974, the plant has produced and tested 88 engines. Their total operating time on test benches reached 11,000 hours, including seven engines that ran 600–800 hours without disassembly.

The 6TD engine successfully passed factory bench tests and was brought to a stage ready for interdepartmental testing.

As a result of field trials of three upgraded T-64A tanks equipped with 6TD engines, covering approximately 30,000 km , the following improvements were observed:

·        Average tank speeds increased by 12–24%, depending on terrain.

·        Average fuel consumption increased by 11.5%.

·        Operational range increased by 7–16% (with some increase in fuel tank capacity).

·        Acceleration time to 40–55 km/h was reduced by more than half.

These tanks were equipped with an automatic selection system for the MTU’s economic operating mode, which reduced fuel consumption by 9–24% and oil consumption by approximately 30%.

One upgraded T-64A tank with a 6TD engine was handed over to NII-38 for range testing.

In parallel with the 1,000 hp 6TD engine, the Central Design Bureau developed the technical project and built the first experimental 6TDF engines, boosted to 1,200–1,250 hp. This engine differs mainly in the design of the supercharger impeller and the introduction of jet oil cooling for the pistons. Previously planned intermediate air cooling after the supercharger was not required.

Parametric bench tests of the manufactured prototypes have been conducted, and one of these engines is undergoing field parametric testing in a T-64A tank (Object 476) at the plant.

Tank “Object 476” is an evolutionary development of the T-64A. Major improvements focused on the powertrain compartment, where the 1,000 hp 6TD engine with an improved automatic loader was installed. A key innovation was a new turret design with enhanced armor protection and half the area of weak spots compared to the T-64A. The filler consisted of box-type plates filled with polyurethane. The filler dimensions were 260 mm , with the turret’s front wall 100 mm and rear 190 mm . With an overall thickness of 550 mm (at ±35°), protection against shaped-charge warheads was equivalent to 520 mm of medium-hard armor. Protection against 125 mm APFSDS rounds was ensured at close range.

Subsequently, developments from the Object 476 “Kedr” turret were used as the basis for Object 478 tanks. Further evolution of the same design, but with a new filler package, was applied to serial T-80U and T-80UD tanks.

Test results show that installing this engine in a tank allows an increase in average speed of 11% compared to the 1,000 hp engine. At the same time, fuel consumption increases by 14.6%, and operational range decreases by 13%. Acceleration time to 50 km/h is reduced by 17%.

One upgraded T-80 tank with a 1,200 hp 6TDF engine was handed over to NII-38 of the USSR Ministry of Defense for comparative range testing against a serial T-64A and a T-64A equipped with a 1,000 hp 6TD engine.

Warranty Testing of 5TDF and V-46-6 Engines

Studying materials on improving the reliability of the 5TDF engine without comparison to engines installed in other vehicles can give a misleading impression of its low reliability. For a more complete assessment, data on the reliability of the 5TDF and V-46-6 engines during warranty and military testing are provided from source [5]. Data from 1979 show that four years after the T-72 entered service and six years after the T-64A, engines in these tanks still experienced reliability issues. Notably, the failure rate parameter of the V-46-6 was higher than that of the 5TDF.

5TDF

During 1979, two first-category 5TDF engines were supplied for warranty bench tests. Both engines operated for 800 hours under test conditions. The engine manufactured in the first quarter of 1979 completed all 800 hours without any issues. On the engine from the third quarter, surge phenomena appeared from the 65th hour and persisted until the end of testing. The surge was caused by coking in the air-gas tract, which in turn was due to reduced detergent and anti-carbonization properties of the batch of oil used for testing.

Thus, the warranty bench tests confirmed the operational reliability of the 5TDF engines over the warranty period.

V-46-6

Warranty testing of a first-quarter 1979 V-46-6 engine was stopped at 370/315 hours due to piston ring failure and piston bridge breakage. Two control engines for the first quarter—one standard and one with barrel-shaped oval pistons—successfully completed warranty testing, with the barrel-shaped piston engine running 1,050 hours.

Testing of the second-quarter warranty engine (with barrel-shaped oval pistons) was stopped after 484 hours due to scuffing of the second piston, ring breakage, aluminum burn on the cone and first bridge. After replacing the first and second piston sets, testing continued to the warranty completion of 540/502 hours. Inspection revealed scuffing on the piston rings and wear of the piston grooves up to 0.45 mm .

Testing of three engines in the third quarter was not accepted by the customer representative. The third-quarter warranty engine stopped at 354 hours, while control engines—one with standard pistons—stopped at 296 hours, and one with barrel-shaped pistons—at 462 hours. All three engines experienced ring breakage, piston bridge failure, and increased groove wear.

At the customer’s request, another V-46-6 engine was bench-tested for 50 hours to assess piston group quality after short-term use. Inspection revealed increased groove wear and other piston and ring defects. Specialists concluded that the main causes were low-quality piston ring manufacturing (scuffing, scratches, chrome chipping) and uneven (spotty) anodizing of the grooves.

The fourth-quarter 1979 engine completed 500 hours of warranty testing and was accepted by the customer representative. However, post-test disassembly revealed broken piston rings on the 2nd and 4th pistons of the left block and groove wear under the broken rings.

Thus, the warranty tests indicate serious defects in the V-46-6 piston group, requiring urgent corrective measures.

Military Control Testing of Vehicles with 5TDF and V-46-6 Engines

Testing of vehicles with V-46-6 engines was conducted alongside vehicles with 5TDF engines. At the end of testing, the average operating time of engines in the “Sosna” area was 254.3 hours, and in the “Kedr” area—252.7 hours. During testing, there were ten V-46-6 engine failures of a design-manufacturing nature, including three resource-related failures.

All three resource failures (two in “Sosna” and one in “Kedr”) were related to piston group failures (V06-4766 at 23 hours, V05-3898 at 235.3 hours, V05-4165 at 252 hours). This confirms the need for urgent implementation of corrective measures for piston group defects.

Other issues observed during testing:

·        Four cases of coolant leakage from the cylinder head due to deformation of the rubber sealing ring for coolant bypass from the cylinder jacket to the head:

o       “Sosna”: V05-3787 at 45 and 89 hours, V05-3983 at 94 hours

o       “Kedr”: V05-3882 at 53 hours

·        Two engine failures due to poor assembly at the V-2302 plant:

o       Coolant leakage due to loosened nut securing the pipe connecting upper and lower crankcases (V06-4593 at 221 hours, “Sosna”)

o       Fuel leakage through a crack in the pipe from the fine fuel filter to the high-pressure pump (V05-4124 at 170 hours, “Kedr”)

·        Fuel entering the oil due to leakage at the injector nut of cylinder 2 left and injector 6 right (V06-4593 at 267 hours, “Sosna”).

At the end of testing, total operating time of V-46-6 engines was 2,543.1 hours in “Sosna” and 2,526.7 hours in “Kedr.”

The failure rate parameter for V-46-6 engines based on KVI-79 over 300 hours of operation was: