Component failure rates for T-72 and T-80 AFVs

Component failure in Soviet armoured fighting vehicles (AFVs) and infantry fighting vehicles (IFVs) is a common occurrence. The failure rate of components depends on factors such as quality, durability, service longevity, and serviceability. This variable can also be affected by poor repairability potential and a lack of automated diagnostic systems to monitor vehicle status.

The failure rate of components is determined by the number of failures that occur within a specified operating range. For Soviet vehicles, this operating range is measured in thousands of kilometres. Therefore, the failure rate can be expressed as the number of operational failures per 1000 kilometres [<i> Failure rate] = Operating Failure/1000km).  

Another important aspect is commonly occurring failure (COF). COF refers to parts within a module or an entire module that are prone to common failures. These failures require significant attention and resources for maintenance and repair.

The following set of data represents vehicles from the 1980s and 1990s; it does not include modernized AFVs like T-80BVM, T-90, T-72B3, T-90M and other modernizations. 
The generalized vehicles that fall under the category of analyzed vehicles are T-72A/B and T-80B/BV/U respectively. 

   Generalized failure rate among components between T-72 and T-80 tanks

Functional component group	T-72		T-80
	Amount of COF	Percentage out of total COF	Amount of COF	Percentage out of total COF
Engine	76	0,067	185	0,124
Transmission	69	0,060	149	0,100
Engine support systems	83	0,077	55	0,037
Running gear	375	0,328	448	0,301
Weapons	61	0,053	128	0,086
Stabilizer	47	0,041	82	0,055
Autoloader (AZ or MZ)	72	0,063	139	0,093
Optics	74	0,065	107	0,072
General electrical equipment	22	0,019	149	0,100
Life support systems	15	0,013	32	0,022
Special equipment	-	-	14	0,009

According to the chart, the running gear module has a high failure rate, including rubberized roadwheels, support rollers, and track links. Engines and transmissions also have elevated failure rates, such as hermetic leaks, fuel line corrosion, fuel injector blocks, and cylinder gasket failures. The electrical systems, stabilizers, and optics primarily face issues like corrosion, seal failure, solenoid failure, among others.

Lastly, another important metric for COF is baseline guaranteed failure. This metric is developed by specialized institutions that test vehicles in a controlled environment using qualified personnel. These tests are conducted with facilitated servicing and repair, and appropriate use of oil, fuel, and coolant. Baseline guarantees are generated under near-perfect conditions, which lowers the COF significantly. During trials, various components may be overstressed or under-stressed, creating outliers. Additionally, a critical factor is how and when vehicles are operated in different climates and terrain conditions.

Baseline guarantee failures compared to service usage failures among various T-80 modifications between 1980-1992.

Functional component group	Amount of COF		Failure rate per/1000km
	Baseline guarantee failure	Service usage failure	Baseline guarantee failure	Service usage failure
Engine	6	156	0,035	0,254
Transmission	2	66	0,012	0,107
Engine support systems	5	159	0,029	0,259
Running gear	42	419	0,244	0,682
Weapons	0	154	0,000	0,251
Autoloader (MZ)	1	125	0,006	0,204
Optics	4	234	0,023	0,382
General electrical equipment	13	247	0,076	0,402
Life support systems	1	40	0,006	0,065
Special equipment	0	14	0,000	0,023
General failure among tanks	74	1614	0,431	2,629

In summary, the data sets reveal two key points:

·       Factory-provided baseline guarantee failure rates are much lower than actual service usage rates for vehicles in uncontrolled environments.

·       The complexity of the T-80 significantly impacts failure rates, especially in engine transmission and running gear, possibly due to poor maintenance or unqualified personnel.

References: 

• Защита оборудования и экипажа военных гусеничных машин от механоакустических и климатических воздействий: Монография. — СПб. : Издательство «Лань», 2016