Aileron, read GOST, not the form ;-).
Although the last time I looked at the forms (a long time ago), there were “resources” and “service life”.
The bourgeoisie uses the vague term "Life".
I already posted one of my old “essays” on this topic. If people don’t judge, I can reproduce it for thought (but it’s a little long ;-)):

1. GENERAL PRINCIPLES OF ORGANIZING WORK TO ENSURE THE DURABILITY OF AIRCRAFT EQUIPMENT ABROAD

The requirements of paragraphs of aviation regulations FAR 25.571 and JAR 25.571 do not regulate the establishment of assigned resources (service life), but require calculation-analytical and experimental substantiation of lists of airframe units and components operated according to the resource (safe life) or in accordance with the concept of “damage resistance” or “damage tolerance”, i.e. TES methods.
These basic provisions of FAR 25 are:
" 25.571(a). General. The assessment must demonstrate that catastrophic failure due to fatigue, corrosion, or accidental damage will be prevented throughout the operational life of the airplane....";
" 25.571(b). ... The assessment of the extent of the effect of damage on the residual strength of a structure at any time during the service life must take into account the initial possibility of its detection and subsequent growth under repeated loading. ...";
" 25.571 (c). Evaluation of fatigue strength (safe service life). ... This structure must be capable of withstanding repeated loading ... during its service life without detectable cracks, which must be shown by analysis confirmed test results...."
It is interesting to note that even in ETC terminology abroad, the term “assigned resource” is practically not used; either simply “life” is used as a term that combines the concepts of resource and service life and is used in context (as, for example, in quotes from the FAR given above - operational life). It should be noted that the analogues of the Russian terms “assigned resource (service life)” are the English terms “ultimate life” or “declared life (maximum permitted life)”, which are absent in the text of the FAR.
The term “time between overhaul (TBO)” is not defined as an assigned time between repairs, but denotes the frequency of scheduled inspection and restoration work (CRM) performed on the product after its dismantling from the aircraft (operating time between regular scheduled CWR).
Thus, the development of aircraft and CI is carried out based on the maximum economically justified service life of the aircraft (CI), and their durability is characterized and assessed using a set of reliability indicators that do not include indicators traditional for domestic practice, such as assigned resources and service life.
A gradual extension of aircraft resources is also not practiced. Aircraft abroad are delivered to customers with the lists of units and equipment operated in terms of service life and technical condition established during certification and reflected in the aircraft maintenance program, as well as with warranty obligations established in the contract, including the service life limit (see Section 3 ).
All possible clarifications of the conditions for ensuring the durability of the aircraft are implemented in the form of changes to the maintenance and repair program, in particular in the form of the release of a program for additional control of the airframe structure (Supplemental Structural Inspection Program - SSIP). Such clarifications and additional conditions are typical, as a rule, for aging products and are in no way related to limiting or extending the resources (service life) of the aircraft as a whole, which is provided for by the fundamental regulatory documents (FAR, etc.).
For CI, the situation abroad is closer to domestic practice, however, the frequency of CVR is limited at the initial stage of operation only for particularly complex products (for example, aircraft engines) and not by all companies. Most companies supply CIs to the aircraft manufacturer or operator without limiting resources and service life in the sense accepted in domestic practice, but with a certain system of guarantees. Naturally, all products undergo certification of the “before installation on an aircraft” type, that is, they meet the requirements of FAR (JAR) and technical specifications (Technical Standard Order - TSO standards).
In practice, this means that after the end of all warranties, the operator can use the CI without restrictions (except for those in the type certificate), but he himself bears all the costs associated with damage and failure of the CI.
The practical interpretation of these requirements in terms of durability can be illustrated by the example of two medium-range aircraft BAe.146 and RJ (Canadair Regional Jet) based on materials.
1. During the development stages, the following requirements were imposed on the BAe.146 aircraft (with a typical flight duration of 45 minutes):
service life "before cracks appear" (crack free life - CFL) - 40,000 flights;
period of normal operation (with minimal control and restoration of the structure - normal operation with minor repair) - 55,000 flights;
service life before the start of design inspection (threshold inspection life - TIL) - 16,000 flights (plus two more forms of inspection and restoration work with a frequency of 2 years);
the period of normal operation with an economically justified volume of control and restoration work (economic repair life - ERL or economic design goal - EDG) is 80,000 flights.
At the same time, the volume of the “fatigue” testing program for the structure was 140,000 flight cycles.
It is also interesting to note that, in accordance with the practice of the British CAA, a requirement was put forward for the BAe.146 aircraft, at the time of receipt of the airworthiness certificate, to confirm with test results the possibility of safe operation for 2 years at 4000 flights per year and a safety factor of 5; this requirement is consistent with domestic practice establishing the initial assigned life, however, it regulates the scope of “fatigue” tests, and not the permitted duration of operation of the aircraft fleet.
2. The following basic requirements were imposed on the RJ aircraft, already in operation at present, in terms of its durability:
CFL - 30,000 flight hours (45,000 flights); TIL - 15,000 flight hours (subsequent checks are combined with Form C and are carried out every 3,000 hours);
ERL (EDG) - 60,000 hours (80,000 flights) or 20 years.
Thus, we can summarize that in accordance with the requirements of airlines and government regulations (FAR, JAR), aircraft and spacecraft can and should be operated according to their condition, and their durability is ensured by methods that differ from the domestic practice of establishing and gradually extending assigned resources and service life. An important component of these methods is the use of an extensive guarantee system of the AT supplier.

2. WARRANTY OBLIGATIONS OF SUPPLIERS AND MAINTAINING THE DURABILITY OF AIRCRAFT EQUIPMENT DURING ITS OPERATION

The formation of these guarantees and maintenance of operation are carried out abroad in accordance with ATA recommendations set out in ATA specifications (in particular, ATA Spec. 200, 300 and 400 for the supply of CIs and other logistics issues) and the ATA manual for AT suppliers.
This manual recommends that suppliers (in the interests of successful cooperation with leading airlines and aircraft MRO centers) maintain the following types of guarantees for the supplied aircraft:
 standard warranty,
 guarantee of maximum service life,
 guarantee of CI reliability level,
 guarantee of regular flights,
 guarantee of the volume of maintenance and repair,
 guarantee of costs for materials and spare parts,
 post-repair guarantees.
The standard warranty corresponds to the warranty obligations accepted in domestic practice.
The guarantee of maximum service life and level of reliability are precisely those guarantees that provide the required level of durability and reliability of the supplied AT. Below they will be discussed in more detail.
Guarantees of regularity of flights and maintenance costs are not widespread and are not directly related to durability and are therefore not discussed in detail.
The guarantee of post-repair reliability consists of the obligation to extend the initial warranty after repair of the CI, i.e. accounting for its expiration, starting from the moment the CI is restored after a break at the time of its failure.
In relation to all types of guarantees, there are a number of general conditions for the supply of aircraft related to the organization of maintaining the durability of the aircraft and spacecraft in operation, in particular, it is expected that suppliers of the airframe and engines of the aircraft will:
 receive certificates from CI sub-suppliers and enter into agreements with them to maintain guarantees, and will also support the obligations of CI suppliers in the event of their failure to fulfill warranty work on CIs installed on an aircraft or engine;
 provide the operator with general guidance on the entire system of guarantees for aircraft and spacecraft, the procedure for their implementation and control;
 allow the operator to independently eliminate failures and damage at the expense of suppliers during the warranty period, if it has a state-certified (certified) material and technical base for this, and the technology and equipment meet the requirements of the supplier of the CI or the aircraft as a whole;
 share with the operator the costs of eliminating breakdowns and damage to the vehicle caused by foreign objects, if the design is created taking into account resistance to such damage;
 carry out warranty repairs of the CI within a timeframe that is shorter than the scheduled maintenance and repair forms for a given CI;
 allow operators to transfer rights to guarantees to a third party in case of lease, sale and transfer of aircraft;
 reimburse costs for warranty repairs performed by the operator (labor costs, including overhead, at rates agreed upon for the current period and costs for materials and spare parts at current prices).
The standard warranty meets all of the above conditions and also contains a number of additional conditions.
1. Products must not have any failures or damage and meet the requirements of the delivery conditions (technical specifications) within the period of time agreed upon by the parties.
2. Guaranteed elimination is subject to CI failures, and sometimes (under the supply contract) and secondary damage caused by them.
3. Mandatory modifications (airworthiness directives) must be carried out at the expense of the aircraft supplier and with the participation, if necessary, of its specialists.
4. The warranty period must begin from the start of use of the CI (AC) and can cover the entire period of its operation, however, this period cannot be less than the frequency of the first type of scheduled maintenance planned according to the scheme.
5. If a structural defect is identified and eliminated during the warranty repair of the CI, all CIs of the fleet must be replaced with modified ones.
6. In the event of a failure of a CI operated for its service life during the warranty period, it must be replaced with a new one if the failed CI has exhausted at least 50% of its service life, otherwise the failed CI is subject to restoration (repair).
Typical terms of a standard warranty range from 6 months to 5 years of operation, depending on the type and cause of failure. Airbus Industrie contracts are characterized by a standard warranty ranging from 6 months to 4.5 years. At the same time, it should be noted that the opinion expressed in the report (apparently the general opinion of all operators) is that the standard warranty period should be at least 5 years. Such obligations are assumed, in particular, by Dassault (for example, for the Falcon 900B aircraft).
The ultimate service life guarantee is intended to ensure a level of durability of the main power elements of the airframe and aircraft engines that satisfies the operator. It is established in units of operating time and/or calendar period as agreed by the parties. Usually for large aircraft its value is higher and can reach 60,000 flight cycles and 20 years of operation. For light aircraft it is significantly less; for example, for the Falcon 900B aircraft, the maximum airframe service life guarantee is 10 years or 10,000 flight hours.
The meaning of this guarantee is that, within its framework, all costs associated with airframe (engine) failures during the period after the end of the standard warranty are reimbursed jointly by the supplier and the operator on a pro-rata basis (apparently, in proportion to the completion of the warranty period).
The reliability level guarantee is another guarantee associated with maintaining the longevity of the CI. It consists in the supplier’s obligations to ensure on its own a quick replacement of failed CIs if:
 these CIs are operated according to their resource;
 they are equipped with a guaranteed value of time between failures (MTBF) or time between unscheduled removal from board (MTBUR) and this value is not confirmed during the warranty period.
The size of the warranty period is usually set at least 5 years and it is extended beyond that, if necessary, until the value of the guaranteed level of reliability is confirmed over an interval of 18 consecutive months. The methodology for calculating this level is usually included in the guarantee agreement for the contract for the supply of aircraft (CI).
Thus, maintaining the level of aircraft durability in operation is carried out abroad by implementing a system of guarantees, in particular regarding the level of reliability of the aircraft and the maximum service life of the airframe and aircraft engines.
Abroad, just as in domestic practice, there is a system for performing additional inspections and modifications to the aircraft design, however, this is typical for aging aircraft (at the end of the service life guarantee period or beyond) and is aimed not at “life extension”, but at preserving already declared level of durability, or increasing the technical and economic efficiency of operation. In some cases, Supplemental (Structural) Inspection Programs (SSIP) are quite extensive work packages, but within the service life guarantee, their implementation is jointly financed by the supplier and the aircraft operator. If the need for modifications is identified due to an insufficient level of design failure safety identified in operation, i.e. implementation of airworthiness directives, all costs are borne by the aircraft (engine) supplier.
In some cases, the implementation of special inspection programs (such as SSIP) and modifications at the supplier's base provides an increase in the service life guarantee. For example, for aircraft manufactured by Sabreliner Corporation, it is possible to increase the service life guarantee from 10,000 to 15,000 flight hours (after performing a special form of Excalibur Inspection in the corporation's MRO center), or even up to 30,000 flight hours when performing a more labor-intensive form of control and modification of the airframe design .
In conclusion, we can summarize that, in contrast to domestic practice abroad, maintaining the durability of aircraft in operation is carried out not on the basis of a phased extension of service life, but through the implementation of a broad system of guarantees and step-by-step (with a “big step” of 5...15 thousand hours of operating time) ) clarifying the conditions (in terms of CWR volumes) for working out the calculated or guaranteed EDG values. At the same time, as the resource is used up, there is always a flexible regulation of the costs of the operator and the supplier for these works, carried out on a mutually acceptable contractual basis and in accordance with current advisory documents, for example, ATA.

LIST OF SOURCES USED

1. Falcon 20 Retrofit. Bendix/King, Allied Signal Inc., 1990.
2. Requirements for Future Advanced Short/Medium Range Aircraft, AEA, 1983.
3. ATA World Airlines and Suppliers Guide, ATA, January 1994.
4. Program Plan - National Aging Aircraft Research Program, FAA/DOT USA, 1989.
5. World Airlines Technical Operations Glossary (WATOG), 10th Edition, ATA, IATA, ICCAIA, 1983.
6. Whittington H. RJ Rolls Out. - Commuter World, June-July, 1991.
7. Grigg R.E. Development of Maintenance Program Through Flight Test Phase. Proceedings of Aircraft Engineering Conference AIRMECH"81, February 10-12, Zurich, 1981.
8. Meline J. What the Operator Wants. Right there.
9. Olcott J.M. Dassault Falcon 900B.- Business and Commercial Aviation, October, 1991.
10. Sabreliner Maintenance and Repair, Sabreliner Corp., 1991.
11. Edwards T.M., Wilson R.G. Maintenance Program Analysis for Aircraft Structures of the 80"s: MSG-3.- SAE Technical Paper Series, 1980, N 801214.
12. Maintenance Review Board Report. MDD DC-10-10 Maintenance Program, FAA/DOT USA, 1971.
13. Supplement to MDD DC-10-10 MRB Report (Applicable to MDD DC-10-30, -30F, -40), FAA/DOT USA, 1973.
14. Bradbury S.J. MSG-3 as Viewed by the Manufacturer (Was It Effective?). - SAE Technical Paper Series, 1984, N 841482.

Aircraft classification(VS). Civil aviation airplanes and helicopters are assigned a class depending on their weight (Table 1.1).

Table 1.1

Airplanes are also classified depending on their flight range in kilometers:

Trunk long-distance………………………………more than 6000

Trunk average……………………………2500 – 6000

Trunk short-range……………………………..1000 – 2500

Airplane of local airlines (LOL)…………up to 1000

Aviation resources . During operation, wear of moving elements and aging of materials occurs, and accumulation of fatigue phenomena in AT products occurs. The consequence of this is an increase in the failure rate of products. Therefore, resources and service life are established for AT products.

Warranty resource (warranty operating time) Tg – operating time of a product (in hours, cycles or other units of measurement), within which the manufacturer guarantees normal operation and provides (free) restoration of failed products, subject to compliance with the rules of operation, storage, and transportation.

Warranty period (warranty period) – a calendar period during which the manufacturer guarantees normal operation and provides (free) restoration of failed products, subject to compliance with the rules of operation, storage, and transportation.

Warranty resources and service life are established for each AT product. The manufacturer's warranty ends after the end of at least one of these periods. So, for example, let the unit have a warranty life (operating time) of 1000 hours and a warranty service life of 3 years. If the unit has worked for 1000 hours in 1.5 years or in 3 years it has worked for 500 hours, then in both cases the warranty for the unit is terminated.

Currently, the warranty service life of AT products is usually set within 3 - 5 years.

Assigned (or shared) technical resource (Tnazn) – the total operating time of the product, upon reaching which operation must be stopped, regardless of the condition of the product.

Total service life – the total calendar duration of operation of the product to the limit state at which its repair is technically impossible or economically impractical.

Overhaul life (Tmr) – operating time of a product between two successive planned overhauls. For a new product, the service life until the first major overhaul is established.

Service life between overhauls – calendar duration of product operation between two successive planned overhauls.

Within the assigned resource (total service life), there may be several TBO resources.

The warranty life and service life are established by a special agreement between the Department of Aviation Industry and the Department of Civil Aviation for each specific aircraft and type of aircraft. This resource has both legal and financial significance. During the warranty period, the manufacturer is obliged to restore the failed product free of charge.

Between-repair and assigned resources and service life are established jointly by the above-mentioned Departments based on test results and operating experience of similar products.

During operation it is carried out mandatory accounting AT resource consumption. This expense includes:

For airplanes - flight hours and number of landings;

For helicopters - flight hours and 1/5 of the time their main rotors and transmissions operate on the ground;

For aircraft engines - flight time and 1/5 of the time they operate on the ground.

Some products of on-board systems have special counters (hours) for their operating time. For devices, units, units that do not have special records of their operating time, it is assumed that their operating time is equal to the aircraft flight time.

Only serviceable aircraft that meet the technical specifications (TS) and have been checked and trained in accordance with the Manual on the technical operation and repair of aircraft are allowed to fly.

Considering the special place of the concepts “resource (service life)” in ensuring and maintaining the airworthiness of an aircraft, in addition to their standardized definitions, the following explanations are necessary.

For aircraft civil aviation equipment, in order to ensure safety, reliability and operational efficiency, the following can be specified:

■ resource (service life) before write-off (technical);

■ assigned resource (service life);

■ warranty life (service life);

■ overhaul (until the 1st repair) resource (service life),

The specified types of resources for various products can be determined and (or) installed in a complex, separately, or not installed at all during operation due to technical condition.

The service life before decommissioning is set for the aircraft as a whole and the main components based on the requirements of efficiency, subject to ensuring operational safety. The resource can be used up in stages before being written off.

During the gradual development of the resource before write-off, the following can be installed:

■ initial assigned resource;

■ assigned resource.

The procedure for ensuring and working out the service life before decommissioning is determined jointly by the developer and the customer (operator), reflected in the technical specifications (TS) for the aircraft and components and established by the aircraft supply contract.

The warranty life of the product determines the period of validity of the manufacturer’s (work performer’s) warranty and must ensure that the quality of the supplied products (work performed) meets the requirements established in the supply contract (work performance) or operational documentation. Within the warranty period, as a rule, product failures must be eliminated without additional payment by the operator or low-quality products must be replaced (work must be repeated) subject to the operator’s (customer’s) compliance with the operating, storage, transportation and installation conditions of the product, determined by the technical specifications on the aircraft and the control equipment (agreement on performance of work).

Warranty resources (service periods) established by manufacturers of aircraft and CTs, as a rule, cover a given operating period (calendar period) from the start of operation of the aircraft as a whole and CTs.

The shelf life of the product from the moment of manufacture to the start of operation may be included in the warranty service life, which must be reflected in the operational documentation for the product and the technical specifications for the aircraft.

The warranty resources established by the performer of restoration work for the aircraft and main products cover a given period of operation of the aircraft as a whole and (or) components after completion of these works.

The service life of a product is determined by the conditions for ensuring the reliability and economical operation of a fleet of products of this type and sets a limitation on the use of these products, regardless of their actual technical condition.

The first repair is carried out when the product's service life from the beginning of operation is equal to the service life before the first repair; then the time between repairs can be established until the service life is exhausted before write-off.

Between-repair (up to the 1st repair) resources can be set for the aircraft as a whole and individual products. The amount of time between overhauls is determined by the developers of aircraft and products based on the conditions for ensuring the service life before decommissioning of the aircraft or product, or is established by the operator and the performer of work (repairs), based on the technical condition of the products, technologies and organization of work, subject to ensuring the safety, economy and efficiency of operation of this type of product and (or) the aircraft as a whole.

The general principles of forming a system of aviation equipment resources are understood as follows.

The service life before decommissioning is a technical and economic characteristic of the perfection of an aircraft product and represents the expected limit of cost-effective use of the product for its intended purpose in real operating conditions, which is technically included in the design during design and can be achieved and even exceeded during operation after a set of work to ensure safety and reliability of operation, confirmation of compliance with established requirements and determination of conditions for ensuring compliance with these requirements. Therefore, the resource before write-off is specified, and the conditions for its confirmation (or non-confirmation) are regulated by the economic and technical relationships of the developer, manufacturer and operator, established on the basis of contractual relations in accordance with current laws and regulations.

Providing and confirming part of the specified resource before decommissioning is realized, if necessary, by establishing the assigned (initial assigned) resource for aviation equipment products, which is carried out after completing a set of resource works that justify the safe and reliable operation of the products within the established limits of operating time (service life) with the determination of all necessary , from the standpoint of safety and reliability, conditions and restrictions on the processes of flight and technical operation. In practice, it can be confirmed both the possibility of operating a product beyond the initially specified resource before write-off, and the impossibility of achieving it.

The list of conditions and restrictions that ensure the possibility of operating a product within the designated resource, as a rule, includes control and restoration work (CWR) to monitor the technical condition, repair or replace elements (parts, assemblies, blocks) of the product, which must be performed on various stages of working out the assigned resource. Based on the common technological or organizational conditions for performing these works, these works are grouped into complexes performed at specified intervals of operating the aircraft as a whole, often using special equipment, equipment, documentation and specialists. At the same time, it may be organizationally and economically feasible to carry out CWR at specialized enterprises that carry them out efficiently, with the provision of additional services (such as restoration of appearance, compliance with technical parameters, etc.) not directly related to the safety of aircraft operation as a whole. In this case, the frequency of CWR can be established both for the time between overhauls for the aircraft as a whole, and for its individual products, which establishes the organizational design of the conditions for performing CWR complexes at a specialized enterprise or in the operator’s department. Thus, the overhaul life establishes not technical, but organizational forms of fulfilling the conditions for working out the resource before write-off (assigned resource), associated with restoring the technical condition of an aircraft product, and is not mandatory for its purpose.

The service life before decommissioning (assigned) may also not be established for the aircraft as a whole, but is determined by the economic feasibility of restoring the airworthiness of the aircraft and the conditions for its maintenance at the considered interval (stage) of aircraft operation.

The conditions for ensuring the airworthiness of the aircraft are established by the manufacturer, developer and implemented by the operator, who determines for himself the economic feasibility of carrying out work to ensure the airworthiness of the aircraft while working out the assigned resource in order to continue further operation of the aircraft. If it is not economically feasible to carry out work to maintain the airworthiness of the aircraft (large amount of modifications, etc.), the operator may stop further operation of the aircraft, although the technical qualities of the aircraft may ensure its further operation at the level of established requirements, but with high costs of funds, labor or time.

The terms, definitions and explanations set out above form the basis of the Russian civil aviation aircraft maintenance and repair systems.

In reliability theory, the following temporary concepts of reliability are used, which in turn are its indicators.

Running time– duration or volume of system operation.

Run-to-failure– operating time of the system from the start of operation until the first failure occurs.

Time between failures– operating time of the system from the end of restoration of its operational state after a failure until the next failure occurs.

Recovery time– duration of restoration of the system’s operational state.

Resource– the total operating time of the system from the start of its operation or its resumption after repair until the transition to the limit state.

Life time– calendar duration of operation from the start of operation of the system or its resumption after repair until the transition to the limit state.

Shelf life– calendar duration of storage and (or) transportation of an object, during which the values ​​of parameters characterizing the ability of the object to perform specified functions are maintained within specified limits.

After the expiration of the shelf life, the object must meet the requirements of reliability, durability and maintainability established by the regulatory and technical documentation for the object

Residual resource– the total operating time of the system from the moment of monitoring its technical condition until the transition to the limit state.

Similarly, the concepts of residual time to failure, residual service life and residual shelf life are introduced.

Assigned resource– the total operating time, upon reaching which the operation of the system must be stopped, regardless of its technical condition.

Assigned service life– calendar duration of operation, upon reaching which the operation of the facility must be terminated, regardless of its technical condition.

Upon expiration of the assigned resource (service life, storage period), the object must be removed from service and a decision must be made as provided for in the relevant regulatory and technical documentation - sending it for repair, decommissioning, destruction, checking and establishing a new assigned period, etc.

The listed concepts refer to a specific individual object. There is an important difference between the quantities defined by these concepts and most quantities characterizing the mechanical, physical and other properties of an individual object. For example, geometric dimensions, mass, temperature, speed, etc. can be measured directly (in principle, at any time during the existence of an object). The operating time of an individual object until the first failure, its operating time between failures, service life, etc. can only be determined after failure has occurred or a limit state has been reached. Until these events occur, we can only talk about predicting these values ​​with greater or lesser certainty.

The situation is complicated due to the fact that operating time, service life, service life and shelf life depend on a large number of factors, some of which cannot be controlled, and the rest are specified with varying degrees of uncertainty.

The purpose of establishing the assigned service life and assigned resource is to ensure the forced advance termination of the use of the object for its intended purpose, based on safety requirements or technical and economic considerations. For objects subject to long-term storage, a designated storage period can be established, after which further storage is unacceptable, for example, due to safety requirements.

When the volume of the assigned resource (designated service life, designated storage period) is reached, and depending on the purpose of the object, operating features, technical condition and other factors, the object can be written off, sent for medium or major repairs, transferred for use other than its intended purpose, or re-mothballed ( during storage) or a decision may be made to continue operation.

Question 9. Indicators used to assess the reliability of products.

Probability of failure-free operation - the probability that, within a given operating time, an object failure does not occur.

The function P(t) is a continuous function of time with the following obvious properties:

Thus, the probability of failure-free operation during finite time intervals can have values ​​of 0

The statistical probability of failure-free operation is characterized by the ratio of the number of properly functioning products to the total number of products under supervision.

where is the number of products working properly at time t;

Number of products under surveillance.

Probability of failure - the probability that an object will fail at least once during a given operating time, being operational at the initial moment.

Statistical assessment of the probability of failure is the ratio of the number of objects that failed at time t to the number of objects that were operational at the initial point in time.

where is the number of products that failed at time t.

The probability of failure-free operation and the probability of failure in the interval from 0 to t are related by the dependence Q (t) = 1 - P (t).

Failure Rate - the conditional probability density of the occurrence of a failure of a non-repairable object, determined for the moment under consideration, provided that the failure did not occur before this moment:

Failure rate is the ratio of the number of failed objects per unit of time to the average number of objects that worked properly during the period of time under consideration (provided that failed products are not restored or replaced with serviceable ones).

where is the number of products that failed during a period of time.

The failure rate allows us to clearly establish the characteristic periods of operation of objects:

1. Run-in period - characterized by a relatively high failure rate. During this period, sudden failures predominantly occur due to defects caused by design errors or violations of manufacturing technology.

2. Normal operating time of machines - characterized by an approximately constant failure rate and is the main and longest failure during the operation of machines. Sudden machine failures during this period occur rarely and are caused mainly by hidden manufacturing defects and premature wear of individual parts.

3. Third period characterized by a significant increase in failure rate. The main reason is wear of parts and connections.

Mean time to failure – the ratio of the amount of time before failure of objects to the number of observed objects, if they all failed during the tests. Used for non-repairable products.

Mean time between failures – the ratio of the total operating time of restored objects to the total number of failures of these objects.

Question 10. Indicators used to assess the durability of products.

Technical resource - this is the operating time of an object from the start of operation or its resumption after a certain type of repair until the transition to the limit state. Operating time can be measured in units of time, length, area, volume, mass and other units.

The mathematical expectation of a resource is called average resource .

Distinguish average life before the first major overhaul, average life between overhauls, average life before write-off, assigned life.

Gamma percentage resource - operating time during which the object will not reach the limit state with a given probability , expressed as a percentage. This indicator is used to select the warranty period for products and determine the need for spare parts.

Life time - calendar duration from the start of operation of the facility or its resumption after a certain type of repair until the transition to the limit state.

The mathematical expectation of the service life is called the average service life. There are service lifes up to first overhaul, service life between overhauls, service life before decommissioning, average service life, gamma percentage service life and assigned average service life.

Gamma percentage life - this is the calendar duration from the start of operation of the object, during which it will not reach the limit state with a given probability , expressed as a percentage.

Assigned service life - this is the calendar duration of operation of the object, upon reaching which the intended use must be discontinued.

One should also distinguish warranty period - a period of calendar time during which the manufacturer undertakes to correct free of charge all defects revealed during the operation of the product, provided that the consumer complies with the operating rules. Warranty period is calculated from the moment of purchase or receipt of products by the consumer. It is not an indicator of the reliability of products and cannot serve as a basis for standardizing and regulating reliability, but only establishes the relationship between the consumer and the manufacturer.

Question 11. Indicators used to assess maintainability andpreservationproducts.

Indicators maintainability

Probability of restoration to working condition - the probability that the time to restore the operational state of the object will not exceed the specified one. This indicator is calculated using the formula

Average time to restore operational status - mathematical expectation of the time to restore a working state.

d*(t) - number of failures

Storability indicators

Gamma percentage shelf life - shelf life achieved by an object with a given probability y, expressed as a percentage.

Average shelf life - mathematical expectation of shelf life.

Question 12. Comprehensive indicators of product reliability.

Availability factor – the probability that the object will be in working condition at any point in time, except for planned periods during which the object is not intended to be used for its intended purpose.

The availability factor characterizes the generalized properties of the equipment being serviced. For example, a product with a high failure rate but a fast recovery time may have a higher availability rate than a product with a low failure rate and a long mean time to repair.

Technical utilization rate – the ratio of the mathematical expectation of time intervals for an object to be in working condition for a certain period of operation to the sum of the mathematical expectations of time intervals for an object to be in working condition, downtime due to maintenance, and repairs for the same period of operation.

The coefficient takes into account the time spent on planned and unscheduled repairs and characterizes the proportion of time the object is in working condition relative to the considered duration of operation.

Operational readiness ratio – the probability that the object will be in working condition at any point in time, except for planned periods during which the object is not intended to be used for its intended purpose, and, starting from this moment, will operate without failure for a given time interval. Characterizes the reliability of objects, the need for use of which arises at an arbitrary point in time, after which trouble-free operation is required.

Planned Application Factor - this is the proportion of the operating period during which the object should not undergo scheduled maintenance and repair, i.e. this is the ratio of the difference between the specified duration of operation and the mathematical expectation of the total duration of scheduled maintenance and repairs for the same period of operation to the value of this period;

Efficiency retention rate - the ratio of the value of the efficiency indicator for a certain duration of operation to the nominal value of this indicator, calculated under the condition that failures of the object do not occur during the same period of operation. The efficiency retention coefficient characterizes the degree of influence of failures of object elements on the efficiency of its intended use.