The fuselage of the helicopter
The fuselage of the helicopter - the airframe. The fuselage of the helicopter is designed to accommodate the crew, equipment and payload. The fuselage can be placed fuel, chassis, engines.
During the development of the volume and weight are determined by the layout configuration of the fuselage of the helicopter and its geometrical parameters, location, size and nature of the loads which have to be perceived strength members. Selecting KCC fuselage is the initial stage of construction. It worked out such a power scheme that best serves to your requirements.
Basic requirements for the CMP of the fuselage:
structural reliability during operation of the helicopter;
to ensure a predetermined level of comfort in the cockpit and the passengers;
high operating efficiency;
Security for the crew and passengers of volume within the fuselage and the possibility of evacuation in an emergency landing of the helicopter.
Performance requirements, scheme and purpose of the helicopter also significantly influence the choice of KSS fuselage. These requirements are as follows:
- - Maximum use of the internal volume of the fuselage;
- - Software required for the helicopter crew review;
- - Ensuring access for inspection and maintenance of all units located in the fuselage;
- - Convenient placement of equipment and supplies;
- - Ease of loading, unloading, load securing in the cockpit;
- - Ease of maintenance;
- - Sound insulation, ventilation and heating facilities for passengers and crew;
- - Possibility of replacing the cabin windows under operating conditions;
- - The possibility of conversion of passenger cabins by changing the layout of the premises, such as chairs and steps to set them.
The fuselage of the helicopter H-21-metal
For emergency evacuation of the helicopter passengers and crew in a helicopter provided emergency exits. Doors for passengers and crew, as well as maintenance hatches included
in the number of emergency exits, if their size and location to meet the relevant requirements. Emergency exits are located in the cockpit, one on each side of the fuselage, or instead provides for a sunroof and one emergency exit on either side of him. Their size and location should provide a rapid evacuation of the helicopter crew. These outputs can not provide, if the helicopter crew can use the emergency exits for passengers located near the cockpit. Emergency exits for passengers must be rectangular with corners radiused no more 0,1 m.
The size of emergency exits for the crew must be at least:
- 480 510 x mm - for on-board outputs;
- 500 510 x mm - for top hatch of a rectangular shape or diameter G40 mm - for round hatch.
Each main and emergency exits must meet the following requirements:
- Having movable or removable door hatch, which provides free access of passengers and crew;
- Easily opened from both inside and outside with a maximum of two pens;
- Have a means for locking the outside and inside, as well as a safety device, which excludes the opening of the door or hatch in flight as a result of random acts. Locking devices make self-locking, no loose handles and keys. The helicopter outside the designated places for cutting out skin in the case of jamming doors and hatches during the emergency landing of the helicopter.
The volume required to accommodate passengers' cargo transported, are critical in the design of the passenger and the cargo compartment of the fuselage.
Appearance fuselage and CBS depends on the destination of the helicopter and its circuit:
- Amphibious helicopter should have a special shape of the lower part of the fuselage that meets the requirements of hydrodynamics (the minimum load on the helicopter landing on the water, the minimum needs 11V traction at take-off, the lack of education in the Splash Zone review pilot and air intake engines, compliance and sustainability buoyancy);
- The fuselage of the helicopter, the crane is a power beam, which is attached to the cabin crew and the cargo transported on external sling or in containers connected with butt nodes lower central part of the fuselage;
- In the most common single-rotor helicopter scheme should have the power to mount cantilever beam PB.
Choice of rational KCC fuselage made primarily on the basis of the weight of statistics, parametric dependencies and summarizes the main circuit prior structures.
As a result of decisions taken form the proposals on the basis of which there is a final selection of the KCC fuselage. In most cases, based on the requirements and the operating conditions are already known in advance what type of design apply in either case, so the problem can be reduced to finding the best option within the specified construction type.
The framework structures are used already tested by long practice KSS - a type design of reinforced shells (beam design), trusses, and combinations thereof.
The most common beam design of the fuselage. The main reason for the development of fuselages beam - the desire to create a sound designer and a rigid structure, in which the material is optimally distributed over the perimeter of a given section, is used efficiently at different loads. The beam structure as much as possible use of the internal volume of the fuselage, provided all the requirements of technology and aerodynamics. Cutouts in the skin require local effort, which increases the weight of the fuselage.
Beam fuselages are divided into two types - spar and packaged.
Scheme fuselage significantly modified in the presence of the recesses in the structure, particularly their considerable length. As we approach the cross sections to the end of the notch stresses in the skin and stringers are significantly reduced, more complex transmission torque and creates additional stress and longitudinal set. To preserve the strength of the panel stringers along the border cutout intensified, becoming a member. Plating and stringers fully incorporated into the work of a section extending from the ends of the cut-out at a distance equal to about the width of the cut. KCC fuselage in such a case it is advisable to take a spar.
The spar structures bending moment is perceived predominantly longitudinal members - spars and cladding perceives local load, shear force and torque.
The monobloc paneling together with the elements of the framework also takes a normal effort of bending moments.
The combination of these power schemes are part of a fuselage stringer stressed skin, which is performed in a thin-walled shell, reinforced by stringers and frames. KCC is a kind of one-piece.
The monocoque of a homogeneous material. It provides for the presence of only two elements - plating and frames. All the forces and moments perceives paneling. This scheme is most commonly used for the tail beam of small diameter - D <400 mm (lining, bent on a small radius of the cylinder, has a high compressive resistance).
The monocoque layered. The use of sandwich panels is, thin bearing layers improves both local and overall rigidity of the fuselage with a regular (without cuts) area. Constructive execution trehsloyiyh (sloychatyh) panels is very flexible, and depends on the materials of the outer and inner layer, type of aggregate, the connection method skins with a filler, etc.
The surface of the fuselage, used to move the technical staff at the respective ground handling units are made of panels sloychatoy design (high rigidity) with a thick outer layer of bearing friction coating. These panels are to be included, and a power circuit fuselage.
The load on the soft fuel tanks it is advisable to take the panels sloychatoy design. These panels, having high rigidity pas bending simultaneously acts as a container tank, and then did not want to create an additional bearing surface rests on the stringer set lower fuselage.
The helicopter airframe CM successfully implemented and operated for several generations of helicopters.
Modern glass-competitive with conventional aluminum alloys in terms of specific strength, but significantly, at least in 30% inferior to them in specific stiffness. This circumstance was a brake on the expansion of the volume of the PA application of fiberglass and structural elements.
Organoplastic - lighter than fiberglass materials with specific stiffness are not inferior to aluminum alloys, and in specific strength in 3-4 times their superior. The widespread development of organic plastics allowed to deliver fundamentally new task - to go from the creation of the individual parts of the CM for the metal structures to the creation of the design of the Cabinet, to their extended use, and in some cases - to create a design with a predominant use of KM.
KM used as the skins in the sandwich panels of feathers, wings, fuselage, and the frame member.
Application organita instead of fiberglass to reduce weight of the glider. In heavily loaded organoplastics units can be used most effectively in combination with other longer rigid materials, for example, • CFRP.
Structurally-technological scheme of the fuselage of the helicopter pilot Boeing-360, all security elements are made of panels sloychatoy design using composite materials.
The use of thin skins, well supported with honeycomb core (having a low density), makes sloychatye design reserve weight reduction of the fuselage. High specific strength and resistance to vibration and acoustic loads determine the growth of the application of such structures as load-bearing elements of the fuselage.
Potential advantages of sandwich structures can be implemented only if the production is organized on a high technical level. Questions of design, technology and strength of these structures are so closely interrelated that the designer can not pay more attention to technological issues.
Long-term strength of glued joints and sealing the cell aggregates (from moisture) - the main thing that should be provided constructive and technological development.
For technological tasks include:
- - The choice of the brand of glue, which provides the necessary strength with an acceptable weight increase;
- - The ability to control technological regimes at all stages of manufacturing units;
- - Providing a predetermined degree of coincidence circuits mating parts (mainly sotobloka and frame);
- - The use of reliable methods for monitoring the strength of bonding with the measurement;
- - Selection of an additional sealing;
- - The introduction of cells without punching.
Truss fuselage. The fuselage truss power circuit elements are spars (chord), racks and bracing in the vertical and horizontal planes. Boarding perceives external aerodynamic loads and transmits them to the farm. The farm takes all kinds of loads: bending and torsional moments and shear forces. Due to the fact that the lining is not included in the power circuit of the fuselage cutouts in it it does not require significant gains. Have truss rods complicates the use of the internal volume of the fuselage, accommodation units and equipment, their installation dismantling.
Eliminating resonant oscillations numerous rods - a difficult task. Truss structure hinders the aerodynamic requirements for the form and the rigidity of the fuselage skin. In this structure, it is difficult to apply the advanced technology nodes welding with a complex configuration of the weld. Heat large farm after welding is connected with certain problems. These truss main shortcomings are the cause of their limitations.
KCC cabin floor is determined by the appointment of a helicopter. The transport helicopter for transportation of wheeled transport cargo floor is necessary to reinforce the longitudinal beams arranged in such a way that the wheel loads data directly perceived power elements. For fixing wheeled transport nodes installed in the floor for fastening bracing wires at the intersection of the longitudinal (stringer) and transverse (the frame) frame members. For loading and unloading of containers used monorails mounted on the ceiling of the cabin. The load on the ropes attached to the trolley, fortified by monorail, and moves it to a predetermined place in the cockpit. Monorails appropriate to include in the power circuit of the fuselage. The cargo cabin also installed mooring units with the required interval for the corresponding loads.
For easy loading and unloading of bulky cargo must mechanize the loading bridge (ramp) so that he could stop and lock in any position, as well as to allow the transport of cargo on the open rear ramp.
Load-bearing elements of the fuselage are mainly made of aluminum alloy. In places exposed to heat, is used titanium and stainless steel. Fairings powerplant and tail transmission (located on top of the tail boom) efficiently perform fiberglass reinforced reinforced ribs.
In the formation of CIL frame unit should consider the following main points:
- The distance between the transverse force elements and placing them on the machine is determined by the place the application of concentrated forces, the normal to the axis of the machine;
- All force applied to the frame member, to be transmitted and distributed on the casing, through which they are usually balanced by other forces;
- Concentrated forces should be seen carcass elements directed parallel to the force - through the stringers and longerons, and the forces acting across the data units - frames or ribs, respectively;
- Focusing forces directed at an angle to the axis of the unit, to be transmitted on the casing through the longitudinal and transverse force elements. The force vector has to pass through the point of intersection of the axes of the rigidity of these elements;
- Cut-outs in the frame unit must have at its periphery in the form of expansion joints reinforced zones of longitudinal and transverse elements.
Availability cuts the power of the fuselage structure, abrupt transitions from one configuration to another and the application area of large concentrated forces (ie. And. "Irregular zone") have a significant impact on the distribution and nature of the power flow stress, which is similar to the field of fluid velocity in the local resistance.
Stress concentration in the elements of the fuselage structure, the amplitude and frequency of the alternating voltage are decisive parameters for solving a very important problem of creating vysokoresursnyh fuselage.
Solve the problems associated with the design of the fuselage, in the following ways:
- Develop KSS based analysis of the nature and place of the application of external forces, and operational requirements, determining all kinds of cuts (their size, location on the fuselage);
- Apply a thin (without torque) trim, which can lose stability during short high loads without permanent deformation;
- On the basis of sufficient experience in production and operation are widely put into practice design elements frame assemblies made of KM.
The final formation of CIL minimum mass of the fuselage with a given resource is carried pa based on experimental results of full-scale framework for settlement cases of the loading force elements with full imitation attached to the fuselage of forces and moments.
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