Development and calculation of the strength of the motor mounting units

Contents

Introduction

This course project is a peculiar result of the study of the discipline "Design and strength of aircraft." It reflects all the knowledge that we received by taking a course of lectures.

The main goal of the course project: the systematization of theoretical and practical knowledge in this discipline in the process of independent work. The course project is an important stage in the training of future aviation specialists, as it contains the necessary information that can be used to ensure the reliability and uninterrupted operation of aircraft systems and assemblies, and as a result, safer and regular flights.

It is also important to call it the fact that in this course project we apply the knowledge gained in other disciplines, such as "Machine Parts," "Flight Dynamics," "Materials Science," "Metrology, Standardization and Certification," "Material Resistance," "Engineering Graphics." This allows us to practice and apply the knowledge gained from these disciplines to a specific aircraft.

Ⅰ. requirements of airworthiness standards for node connections

1.1 Power plant

The power plant of the aircraft includes each component that is required to create thrust, either controls the main propulsion systems, or ensures the safety of the main propulsion systems during the periods between normal inspections or repairs.

For each power plant:

The installation shall satisfy:

engine installation documentation instructions provided for in paragraph 33.5 of Part 33 of the Aviation Regulations; The applicable provisions of this Section E. The plant components shall be designed, arranged and installed in such a way as to ensure their continued safe operation between normal inspections or repairs. The plant shall be available for required inspections and maintenance. The main components of the unit must have metallization that electrically connects them to other parts of the aircraft. For each power plant and auxiliary power plant, it must be proved that no single failure or probable combination of failures will threaten the safe operation of the aircraft, while the consequences of failures of structural elements may not be considered

1.2 Reversing Systems

For turbojet thrust reversal systems:

Each system designed for use only on the ground must be designed so that at any reversal of thrust in flight, the engine would not develop thrust greater than in flight idle mode. Additionally (by analysis or testing or both), it should be shown that each operable reverser (reverser) can be returned to the forward thrust position and the aircraft is able to continue safe flight and land at any possible position of the reverser. Each system intended for operation in flight must be designed so that during normal operation of the system or due to its any failure (or reasonably probable combination of failures) under all expected operating conditions of the aircraft, including during operation on ground, dangerous conditions do not occur. The consequences of failures of structural elements do not need to be considered in case of practical improbability of these failures. Each system shall have means which, in the event of malfunctions in it, would prevent the engine from developing a thrust greater than in idle mode, except where any higher forward thrust is permitted, if it is shown that permissible track control of one aerodynamic means is maintained under the most critical reversal conditions expected in service.

1.3 Engine Performance

Engine performance shall be examined in flight to determine that during its normal operation and operation in special situations within the limits of aircraft and engine operational limitations there are no dangerous adverse events in the engine (such as flow failure, surge and combustion failure, detonation, unacceptable parameter values).

The air intake device of the gas turbine propulsion system shall not, during normal operation, cause dangerous engine vibrations or dangerous vibration loads in its parts due to distortion of air flow.

1.4 Negative overload

No dangerous disturbance in the operation of the main engine, the auxiliary engine approved for use in flight or any component or system associated with these engines shall occur during the flight of an aircraft with negative overloads within the flight mode area prescribed in paragraph 25.333. This should be shown for the longest expected overload duration.

1.5 Torque of engine and auxiliary power plant (APU)

The engine frame of each engine, APU and their supporting structure shall be designed for the following actions:

maximum engine and APU torque corresponding to take-off power and propeller speed acting simultaneously with 75% of maximum operating load in item 1 of paragraph 25.333 maximum engine torque corresponding to maximum continuous power and propeller speed acting simultaneously with maximum operating load in item 1 of paragraph 25.333 and for turboprop engines (in addition to the conditions of paragraphs (a) and this paragraph), the maximum engine torque corresponding to the take-off power and speed of the propeller multiplied by a factor taking into account the failure of the propeller control system, including the rapid propeller fluxing acting simultaneously with the overload of 1.0 in horizontal flight. If you do not have an accurate calculation method, use a factor of 1.6. For turbine engines and APU, the sub-engine frames and the structures supporting them shall be designed to withstand:

Maximum engine torque load considered operational, caused by a sudden engine or APU shutdown due to a fault that may result in a temporary loss of power or thrust, and which may cause the engine or APU to stop as a result of vibration with maximum engine or APU acceleration.

The maximum load from the engine torque, considered as "design, caused by engine or APU shutdown due to structural failure, including the destruction of the fan blade and loading conditions, are also accepted for the wing and fuselage structure on which the power plant is located. When determining the design loads acting on the wing and fuselage under these loading conditions, a safety factor of 1.25 is taken.

1.6 Lateral load on engine installation

Installation of each engine and supporting structure shall be designed for operational G-load acting in lateral direction and equal at least to operational G-load during sliding flight, but not less than 1.33. Lateral load may be considered independent of other flight conditions. When the engine is located on the wing, take the side load at the direction of its action from the aircraft axis not less than

I, = "J g Od/9,81,

where Od - engine weight;

x - maximum values of roll angular velocity obtained in accordance with the conditions specified in 25.349;

d is the distance in plan from the center of gravity of the engine to the longitudinal axis of the aircraft .

Consideration should also be given to the combined effect of the above lateral load and engine weight load.

1.7 Asymmetric loads in case of engine failure

The aircraft shall be designed for asymmetric loads arising in case of critical engine failure. If it is not shown that a simultaneous or consecutive stop of all engines on one side of the plane of symmetry of the aircraft is unlikely, then such a failure should also be considered. The calculation conditions in this case shall be agreed with the Competent Authority.

Aircraft shall be designed for the following conditions (for turboprop aircraft combined with single system failure

limitations of the propeller - fluxing resistance) taking into account the likely corrective actions of the pilot on the flight controls:

In the speed range from VMC to VD, loads caused by engine failure due to fuel failure should be considered as operational. In the speed range Vms to Vc, the loads caused by disconnection of the engine compressor from the turbine or loss of turbine blades should be considered as operational loads, but the safety factor specified in 25.303 can be reduced to 1.25. The decrease in thrust and increase in resistance over time as a result of the above cases of engine failure should be confirmed by tests or other data applicable to the engine-propeller combination in question.

The nature of the change in time and the value of the likely corrective action of the pilot should be determined in reserve, taking into account the characteristics of the considered engine-propeller-aircraft combination.

It can be considered that the corrective action of the pilot is applied at the moment of reaching the maximum sliding angle, but not earlier than 2 s after the engine failure.

1.8 Safety factor

With the exception of specially specified cases, the safety factor is taken to be 1.5. It multiplies the specified operating loads, which are considered as external loads on the design. If loading conditions are determined through design loads, then do not multiply by safety factor, except in specially specified cases

1.9 Safety factors for butt assemblies (fittings)

For all butt assemblies (parts used to connect one subassembly to another), the following conditions shall be met:

For all butt assemblies (fittings) whose strength is not proven

by operational and design load tests, at which actual stresses are reproduced in the butt assembly and the surrounding structure, the safety factor shall be at least 1.15:

- to all parts of butt assembly;

- to parts of attachment and to places of connection of parts of the unit.

It is possible not to use the safety factor for the butt joint for joints made according to the approved procedure and based on these comprehensive tests (for example, solid joints of metal sheathing, welded joints and joints of wooden parts in a lock), or for the support surface for which a larger special coefficient is used.

For all butt assemblies that are integral with a part, fitting, or butt assembly), a part of the entire assembly is considered to be a part of the assembly to where its section becomes typical for a given subassembly. Safety factors of butt joints given in 25.785 (f) (3) shall be applied for all seats, sleepers and straps.

1.11 Fire protection of controls, engine attachment units and other structures providing flight

Vital controls, engine attachment units and other flight support structures located in installed fire hazard areas or adjacent areas that may be exposed to fire in a fire hazard area shall be made of fire impermeable material or protected to withstand fire.

IV. Comparative evaluation of designed AC with prototype

Comparative evaluation of aircraft taken as prototype Il76 MD with designed aircraft BI-6 is performed.

Designed aircraft BI - 6 designed for transportation of equipment and cargo for various purposes. The aircraft is designed to carry cargo with a maximum weight of 28-60 tons. The crew of the aircraft consists of 6 crew members.

Characteristics of Il76 aircraft correspond to the requirements of airworthiness standards. The same airworthiness standards were applicable to the designed BI-6 aircraft.

Maximum take-off weight of BI6 aircraft is 190,000 kg. The maximum take-off weight of the aircraft taken as the prototype Il76 corresponds to 190,000 kg. It follows from this that the weight characteristics of the Il76 aircraft do not differ from the designed BI-2 aircraft.

After alignment calculation it is possible to conclude that aircraft alignment

Silt-76 according to calculations of HTsS=33.34 of % is in allowable limits of 20% (limit-lobby) and 40% (limit-back) centering. Centering with the maximum take-off weight the equal 190000 Il76 aircraft is % HTsS=31.6. The flow rate in the alignments shows small differences in the materials and layout used.

Comparing flight characteristics it is possible to conclude that aircraft cruise speed BI - 6, V = 80 km/h is less than aircraft cruise speed Il76 V = 750 km/h

G-load on Il76 aircraft is the same as on

design aircraft BI - 6 - 2.6 units.

The selected aerodynamic diagram and airframe layout have the following advantages:

- high position of the wing significantly increases the degree of transverse and longitudinal stability of the aircraft, reduces the value of additional resistance associated with wing and fuselage interference.

- the location of the center plan in the upper part of the fuselage does not occupy its useful volume.

- high position of engines under the wing significantly reduces the probability of damage of compressor blades by foreign particles lifted from the runway during take-off and landing of the aircraft .

- low location of the fuselage above the ground provides fast and convenient performance of work on loading and unloading of goods and equipment.

Conclusion

During this course project, using the theoretical knowledge that was obtained during the study of a number of disciplines, such as "Design and Strength of Aircraft," "Design and Strength of Aircraft Engines," "Materials Science," "Flight Dynamics" and many others, the design and calculation of engine attachment units was developed. This course project consists of four sections.

The first section describes the requirements of aviation rules that must be observed when designing an aircraft. This section provides general requirements for aircraft airworthiness standards.

The second section of this course project describes brief information about the Il76 MD aircraft, which is selected as a prototype. This section covers brief information about the prototype design, a brief description of the main elements of the aircraft, its purpose and use. Flight engineering, mass, geometric data of the aircraft necessary for calculations and drawings are given, as well as alignment of the aircraft used for placement of equipment, cargo, crew is given. This section of the course design also describes the structural and power diagram of the aircraft. This section describes the aerodynamic layout of the fuselage, wing, landing gear nacelles, engine nacelles and aircraft fins. The forms and profiles that have these parts, their purpose, layout on the aircraft are described. The same section contains a power layout .

The force diagrams of the airframe parts and their composition and location are described here. The final part provides calculation of aircraft alignment, which is necessary for correct placement of all equipment, cargo, crew on board the aircraft. As a result of calculations, it was determined that at maximum take-off weight, the alignment of the aircraft is within the permissible range of alignment of the prototype.

In the third section, the design and calculation of engine attachment units was developed. This section describes the design of the engine attachment units as well as the power scheme. Strength calculation was carried out, the material from which the engine attachment units are made was also given, and strength calculation was carried out. The calculated engine attachment units comply with the condition of crushing strength and tensile strength, therefore, this design will withstand the calculated load.

The fourth section provides a comparative assessment of the aircraft designed. As a result of the work done on this course project, a cargo aircraft was developed, which is structurally similar to the Il76 prototype.

Graphic material is attached to this course project, which contains a drawing of the general view of the aircraft and a drawing of design developments made in A1 format.