How the USSR compared the reliability of domestic and American armored vehicles

It is no secret that during the Cold War, Soviet tank builders actively monitored their overseas colleagues in terms of the products they produced: they studied the technological advances of the potential enemy’s equipment, all sorts of technical innovations, layout solutions and characteristics of combat vehicles – the enemy, as they say, must be known by sight.
A separate line in the list of interests of domestic engineers was the failure-free operation or, in fact, the reliability of US armored vehicles as one of the main indicators of the technological level of their tank industry. Therefore, special attention was paid to this aspect. And, it must be said, there were reports, texts with a detailed analysis tanks and other machines throughout history, Soviet researchers have written quite a few, but one of them is still quite interesting due to its, let's say, freshness (it was published in 1989): in it, the advanced T-80s are compared with the Abrams, the T-72 with the M60A3, and the BMP-1 and BMP-2 with the M113.
Today, this material, of course, does not represent any practical significance, but historical and from a technological point of view - very good indeed, so we are publishing it.
Comparative assessment of the reliability of domestic and American armored vehicles
The reliability of serial armored vehicles of the USSR and the USA (BMP-2, T-80, M-113, M-1) is analyzed based on data from periodicals and controlled operation of these vehicles.
Operational characteristics, in particular reliability indicators, along with firepower, protection and mobility characteristics are components of a complex indicator of the technical level of armored vehicle models and are used when comparing domestic and foreign tanks, infantry fighting vehicles and armored personnel carriers. Comparability of the reliability of domestic and foreign armored vehicles is ensured by the same approach to determining the reliability indicators and to the operating and testing conditions in which the initial data were obtained. It is also necessary to take into account the process of fine-tuning, during which their reliability changes.
The reliability of domestic serial tanks and infantry fighting vehicles is assessed based on the results of military tests, periodic warranty tests and controlled military operation. In the USA, the reliability of serial armored vehicles is determined based on the data of periodic tests at proving grounds, large-scale exercises and controlled operation.
There is much in common in the methodological approach to assessing the reliability of machines. In our country, the failure rate parameter serves as the reliability criterion, while in the USA the inverse value ω is used — the mean time between failures T. Comparison of ω and T is not difficult. A distinctive feature of the American methodology is the use of two types of the T indicator: the so-called failure-free operation of systems Tc and functional failure-free operation Tf. The Tc indicator coincides with the practice accepted in our country, when all system defects are classified by their impact on the performance of the machine's combat missions, regardless of whether the system is working at the time the defect is detected or not.
As for Tf, this indicator has undergone some changes. Initially, each defect was given "weight" or "significance" based on its impact on the effectiveness of combat missions. This approach was observed during the acceptance tests of M-1 tanks in 1979-1980. Currently, functional reliability is associated with failures that lead to a complete loss of any of the main properties of a tank - firepower, mobility or protection. In domestic practice, this is a previously used method of assessing reliability based on complete failures.
According to American data, functional reliability is 1,8–2,5 times higher than the corresponding estimates of system reliability (Figure). This allows for the transition from one type of assessment to another and comparison with the reliability indicators of domestic equipment.

A method for assessing the significance of failures in terms of the efficiency of a typical combat mission — 300 km of daily march and combat — has been developed for domestic armored vehicles. This approach, close to the American system of assessing functional reliability, has not yet found recognition by the Ministry of Defense, although its application in solving a number of practical problems, such as optimizing the improvement of tactical and technical characteristics, reliability, and cost, may be useful.
Let us consider the operating and testing conditions of American and domestic armored vehicles. In the United States, serial tanks undergo periodic testing at the Aberdeen Proving Ground (Maryland). The proving grounds reproduce a variety of traffic routes and artificial structures that ensure maximum loads on various components of the armored vehicles: a "Belgian" road, a wavy route, a canal with abrasive wet soil, etc. These routes are usually small (0,5-1,5 km long), their maintenance requires significant costs, and therefore they are used to a small extent for periodic running tests of serial vehicles.
Such tests are mainly carried out on routes of moderately and heavily rugged terrain, including marshy areas. Most of these routes are improved dirt roads with gravel and crushed stone surfaces and broken tank routes. The main soil is loam, black soil. There is also a mountain route with a hard surface (length 64 km, altitude above sea level within 360...780 m). In terms of impact on the chassis, these routes are close to the conditions of military tests in Ukraine and the Far East, where the soil does not have abrasive properties. The conditions of high loess dustiness of the air and high mountains, as we have in Central Asia, are not reproduced on the territory of the Aberdeen Proving Ground.
Domestic serial armored vehicles undergo periodic warranty tests at factory testing grounds and military tests, which are usually conducted in one of the regions with extreme external conditions: in the European part of the USSR (heavy roads, abrasive soil); in Central Asia (heat, high loess dust in the air, mountain roads); in the Far East and Transbaikalia (low temperatures, frozen soil).
Thus, military tests, according to the results of which the reliability of domestic vehicles is assessed, are more complicated than tests of serial equipment in the USA, and periodic tests at factory testing grounds are easier both in terms of the impact on the power plant and the chassis.
Controlled exploitation of American VGM is organized in the USA (Forts Hood and Irwin) and in Germany (Bramberg, Schweinfurt). The exploitation conditions in the area of Fort Irwin (California) are typical of desert terrain (sandy soil, thin soil layer, hot dry climate) and are identical to the conditions of the Karakum Desert. Fort Hood (Texas) belongs to the soil and climate zone of American prairies. The soil is loess loam, sand, red soil, relatively uniform soil moisture is observed throughout the year. Their analogue is the southern steppes of the European part of the USSR. In Germany, the exploitation conditions are different. The terrain is hilly, the soil is loess-like clay, the soils are podzolic-brown, the area has coniferous and broad-leaved forests, soil moisture is 550-600 mm per year. The foothills of the Carpathians can serve as an analogue of this territory.
In the USA, the most unfavorable factors are high temperatures and loess dust in the air, which worsen the operation of the gas turbine unit of the M-1 tank; in Germany, there are high loads on the chassis and power plant of the VGM. The conditions of controlled operation of domestic vehicles are close to the conditions in Germany. At the same time, T-80 tanks are not tested in conditions of high loess dust in the air during controlled operation, as are tanks with gas turbines in the USA.
Let us consider the results of periodic verification tests of the M-113 BTR, which has been in serial production for almost 30 years (since 1960). Two indicators were used: Tf for functional failure-free operation and S — the average run between defects that required repair work. Both indicators differ from the indicator accepted in domestic practice and require interpretation. For an approximate determination of the failure-free operation of the M-113 BTR, we will use the ratio between the "functional" and "systemic" failure-free operation and the ratio between the number of countable failures and the total number of defects according to the experience of our VGM. This will allow us to obtain two approximations to the desired indicator ω. Based on the ratio (see figure) Tf/Ts ≈ 2,5, we will calculate the values of ω' (Table 1).

The second approximation of the indicator is obtained from the data of military tests of the BMP-2 in 1982-1983, when the ratio between the total number of failures and malfunctions and the number of countable failures was 1,1-1,4 times. Taking into account the careful registration of defects in the USA and the increase in reliability during the development, for the calculation of ω'' we adopt a uniform change in Tf/Ts from 2 (for vehicles manufactured in 1963-1970) to 3 (for vehicles manufactured in 1978-1979).
For comparison, the main data on the reliability of the chassis of the domestic BMP-2 are provided (Table 2).

Based on the results of controlled operation of 160 M-113 armored personnel carriers, of which 1970 new vehicles were manufactured after 350, two indirect indicators are known: the ratio between failures and malfunctions of various systems and an estimate of the average mileage between failures S=XNUMX km. The number of failures in individual parts of the vehicle is, %:
Engine - 4,6
Engine systems - 17,5
Transmission - 8,5
Chassis - 17,6
Electrical equipment and communications - 23,2
Armament - 1,2
Other systems - 28.
Using this data, one can roughly estimate the reliability of the M-113 and its systems (Table 3).

The overall failure-free rating of the M-113 is determined at ω≈1,2 1/thousand km, the composition of failures (approximately equal number of failures of the power plant, chassis and electrical equipment) indicates the design has been processed. It should be noted that the controlled operation of armored personnel carriers in the United States was carried out in easier conditions than domestic BMP-2, most of which are operated in abrasive soils and broken tank routes of the Carpathian region.
Overall, the reliability of the American armored personnel carrier is approximately equal to the BMP-2.
The failure-free performance of the systems of the M-60A3 tanks, which were no longer in production and were used in the same areas as the M-113, shows that their failure-free performance is significantly worse than that of modern domestic T-72A tanks (Table 4).
More complete information is available on the failures of the new American M-1 tanks, especially during the testing of prototypes of these tanks in 1979. The first prototypes showed a large number of track drops and related destruction of the road wheel tires. Failures of the hydromechanical transmission and gas turbine engine were observed, especially in conditions of high air dustiness.
As the design of the M-1 tank was refined, its reliability and durability reached the level of the original requirements, with the exception of the track resource (Table 5).

According to the data of the controlled operation of the installation batch of serial M-1, in 1980-1982 in Europe and the USA there were cases of replacement of AST-1500 gas turbine engines (or their individual elements), transmissions, stabilizer elements and sights. In the studies of 1983-1984 in the list of 40 most frequently replaced assembly units there is no mention of either the engine, transmission or sights.
According to American experts, the improvement of starting systems, the introduction of periodic monitoring of the engine oil composition and the implementation of restoration repairs due to the block design have resulted in a 5-fold increase in the service life of the AGT-1500 gas turbine engine, and it has now reached 17 km.
The engine's service life was also increased by the refinement of the technology for fastening plastic cyclones in the air cleaner housing, eliminating the damage to seals, as well as the air cleaner design, aimed at increasing the frequency of its maintenance. Obviously, the refinement of the air cleaner design can explain the large number of their replacements in military operation. Note that the high degree of purification of air entering the gas turbine engine in dusty air conditions (USA, Texas) does not lead to the formation of dust deposits in the turbine part of the engine and surge phenomena.
The above-mentioned data on the average service life of the AGT-1500 engine and its possible estimate based on the average operating speed of the M-1 tank (v = 4,7 km/h), equal to 3 h, are of an advertising nature. It was obtained for vehicles manufactured in recent years, which have short service runs, when service failures are practically non-existent. More convincing are the data indicating that with a total service life of AGT-500 of 1500 h, about 800 engines have worked for over 000 h, i.e. their total service life was 20% of the total, and one engine reached 1 h. A similar indicator for the T-000 tank's gas turbine engine is currently 2,5%. The estimate of its average service life, according to operating data, is close to 1 hours. Thus, the service life of the AGT-400 exceeds the service life of the domestic gas turbine engine and is at the level of 80–0,6 hours.
The most common failures in the controlled operation of the M-1 tank are failures of the rubber track shoes and frequent replacement of the tracks (Table 6). They account for approximately half of all operating costs for the tank. At the same time, the operating conditions of the M-1 tank cannot be considered severe, with the exception of Germany, where increased wear of the brackets and drive wheels should be observed. At present, the USA has developed modernized versions of tracks with removable rubber shoes. It is expected that as a result of competitive developments, the track resource will be increased to 8000 km.

The first M-1 tank models were prone to repeated track drops and damage to the road wheel tires. The introduction of a limiting ring on the drive wheels and a mechanical connection between the front road wheel balancer and the guide wheel reduced the likelihood of track drops. The service life of road wheels is currently determined by mechanical loads and external operating conditions. The specific number of road wheel replacements (with low service life of M-1 tanks) is approximately the same as our T-80 tanks, whose 90% service life under operating conditions is 2500 km, and the average is 7500 km.
The large number of battery replacements during operation of M-1 tanks is presumably due to the practice adopted for American military vehicles of replacing them annually.
Output. A comparison of the reliability of armored vehicles of the USA and the USSR, based on the results of periodic tests and controlled military operation, using the principle of comparability, shows that the reliability of the M-113 armored personnel carrier and the domestic BMP-2 is approximately at the same level. In terms of reliability, the American M-60AZ tank is inferior to the domestic T-72. The reliability of the T-80 tank is generally approximately the same as the American M-1, with some superiority of the latter in terms of the service life of the gas turbine engine and worse service life of the chassis.
Source:
"Comparative assessment of the reliability of domestic and American armored vehicles." A.V. Erokhin, V.A. Lichkovakh, B.G. Polyakov, et al.
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