11/15/2019 AIRFRAME AND SYSTEMS EASA Part FCL Sub - 021 PJV - 2019 2 021 AIRFRAME AND SYSTEMS 021 01 Systems Design, Loads, Stresses, maintenance 021 02 Airframe 021 03 Hydraulics 021 04 Landing Gear, wheels, tyres, brakes 021 05 Flight Controls 021 06 Pneumatics – Pressurization and air conditioning systems 021 07 Anti-icing and de icing systems 021 08 Fuel systems 021 09 Electronics 021 10 Piston Engines 021 11 Turbine Engines 021 12 Protection and detection systems 021 13 Oxygen Systems 021 AIRFRAME AND SYSTEMS 1 11/15/2019 021 AIRFRAME AND SYSTEMS 021 01 Systems Design, Loads, Stresses and maintenance 021 01 01 Systems design 021 01 02 Loads and Stress 021 01 03 Fatigue 021 01 04 Corrosion 021 01 05 Maintenance 021 02 Airframe 021 02 01 Construction and attachment methods 021 02 02 Materials 021 02 03 Aeroplane: wings, tail surfaces and control surfaces 021 02 04 Fuselage, landing gear, doors, floor, windscreen and Windows 021 02 05 Helicopter: flight controls structural aspects 021 02 06 Structural limitations 021 AIRFRAME AND SYSTEMS 3 4 WING The wing is responsible to generate a force that counterbalance the weight. It is called lift The function of the wing defines the wing shape and drives the structural project 021 AIRFRAME AND SYSTEMS 2 11/15/2019 WING SHAPE The lift generated by the wing is defined by wing aerodynamic properties However, there are secondary function such as installation of components and system, structural limitations and operational issues that can lead to small changes The following caricaturists will be present: ▪ Wing geometry ▪ Influence of wing parameters in the performance 021 AIRFRAME AND SYSTEMS 5 WING GEOMETRY The wing geometry can be defined by: ▪ Plant ▪ Cross section (profile) – airfoil ▪ Twist ▪ Dihedral 021 AIRFRAME AND SYSTEMS 6 3 11/15/2019 WING GEOMETRY PLANT 021 AIRFRAME AND SYSTEMS 7 WING GEOMETRY PLANT Supermarine Spitfire Pilatus PC-6 Turbo Porter Falcon 50 021 AIRFRAME AND SYSTEMS F-16 Fighting Falcon 8 4 11/15/2019 WING GEOMETRY CROSS SECTION (PROFILE) - AIRFOIL 021 AIRFRAME AND SYSTEMS 9 WING GEOMETRY TWIST 021 AIRFRAME AND SYSTEMS 10 5 11/15/2019 WING GEOMETRY DIHEDRAL Epsilon TB-30 021 AIRFRAME AND SYSTEMS 11 WING INFLUENCE OF GEOMETRY PARAMETERS Wing tip vortex To better understand the influence of the wing geometry in the aerodynamic behave of a wing it is necessary analyze the influence of the a phenomenon that appears in the wing tip known as – wing tip vortex 021 AIRFRAME AND SYSTEMS 12 6 11/15/2019 WING INFLUENCE OF GEOMETRY PARAMETERS Wing tip vortex 021 AIRFRAME AND SYSTEMS 13 WING INFLUENCE OF GEOMETRY PARAMETERS Wing tip vortex The wing vortex induced a descent velocity field across the wing – that originate a resistant component know as induced drag. Induced angle of attack Downward direction 021 AIRFRAME AND SYSTEMS 14 7 11/15/2019 WING INFLUENCE OF GEOMETRY PARAMETERS To chose the shape of the wing several factor needs to be considered specially: Aerodynamic – the objective is maximize the efficiency (reduce the induced drag) Stability and maneuverability 021 AIRFRAME AND SYSTEMS 15 WING INFLUENCE OF GEOMETRY PARAMETERS Plant The plant shape has a direct influence in the generation of the wing marginal vortex across the wingspan. So the plant is responsible to the: Induced drag Stall characteristics of the wing The elliptic shape is the one that has lower induced drag and is more efficient. 021 AIRFRAME AND SYSTEMS 16 8 11/15/2019 WING INFLUENCE OF GEOMETRY PARAMETERS Plant One problem of the elliptic shape is that all the wing stall at the Same time. So it is possible to change the wing shape to change the away that the stall is felt across the wing: 021 AIRFRAME AND SYSTEMS 17 WING INFLUENCE OF GEOMETRY PARAMETERS Sweep The principal reasons for a positive sweep angle are: Reduce the compressible effect at higher Mach numbers Increase stability longitudinal, directional and rolling 021 AIRFRAME AND SYSTEMS 18 9 11/15/2019 WING INFLUENCE OF GEOMETRY PARAMETERS Non planar wings The introduction of dihedral in a wing and winglet allows reduce the effect of the marginal vortex and at the same time use them in a favorable away. So, non planar wings can have higher efficient than the elliptic wing Contributes positively for the roll stability 021 AIRFRAME AND SYSTEMS 19 WING INFLUENCE OF GEOMETRY PARAMETERS Non planar wings Dihedral Reduces the induced drag in the wing tip but the principal reason to used it is because increases the rolling stability 021 AIRFRAME AND SYSTEMS 20 10 11/15/2019 WING INFLUENCE OF GEOMETRY PARAMETERS Non planar wings Winglets This structure installed in the wing tip can be useful to improve the aircraft performance Increases the effective aspect ration by saving the lateral space (without increasing wing span) 021 AIRFRAME AND SYSTEMS 21 WING INFLUENCE OF GEOMETRY PARAMETERS Non planar wings Winglets In some cases can provide a small contribution to the aircraft thrust. Disadvantages: - Creates drag if not operated in optimal conditions - Increase weight - Increases loads on the wing, so is necessary introduce structural reinforcement 021 AIRFRAME AND SYSTEMS 22 11 11/15/2019 WING POSITION IN THE FUSELAGE The wing can be connected to the fuselage in 2 different away: ▪ Braced Monoplane 021 AIRFRAME AND SYSTEMS ▪ Cantilever 23 WING POSITION IN THE FUSELAGE Braced Monoplane The wing is fixed with the external reinforcement bars : Solution used in small and light airplanes Provides stiffness to the wing, without major weight penalties High drag What type of loads are in the brace? 021 AIRFRAME AND SYSTEMS 24 12 11/15/2019 WING POSITION IN THE FUSELAGE Cantilever No external supports the wing is fixed in the fuselage: Requires a stiffer wing structure heavier Lower drag Better for high performance aircrafts 021 AIRFRAME AND SYSTEMS 25 WING POSITION IN THE FUSELAGE A wing can be installed in 3 different positions: Low wing High wing Med wing 021 AIRFRAME AND SYSTEMS 26 13 11/15/2019 WING POSITION IN THE FUSELAGE Low wing Higher CG position Instability in rolling Smaller landing gear harms If engine installed on the wing (small propeller diameter) 021 AIRFRAME AND SYSTEMS 27 WING POSITION IN THE FUSELAGE High wing Downward good visibility Easier loading and unloading Rolling stability wing can be built as one single member 021 AIRFRAME AND SYSTEMS 28 14 11/15/2019 WING POSITION IN THE FUSELAGE Med wing Lower interference drag Wing spar attached to the center of the fuselage 021 AIRFRAME AND SYSTEMS 29 WING LOADS The wing, as the fuselage has higher loads. The origin of the wing loading is the following: Aerodynamics Loads Inertia, distributed and concentrated loads The most important loadings that are used to define the wing structure are the aerodynamic loads 021 AIRFRAME AND SYSTEMS 30 15 11/15/2019 WING LOADS Example of loads on a wing Symmetric flight 021 AIRFRAME AND SYSTEMS 31 WING LOADS Example of loads on a wing Symmetric flight 021 AIRFRAME AND SYSTEMS 32 16 11/15/2019 WING LOADS Example of loads on a wing Symmetric flight 021 AIRFRAME AND SYSTEMS 33 WING LOADS Example of loads on a wing Loads on the ground 021 AIRFRAME AND SYSTEMS 34 17 11/15/2019 WING LOADS Structural Requirements Aerodynamic loads are distributed along 2 different directions: Along the wingspan Along the chord Shear and bending Torsion and shear Beam along wingspan Torsion box It is still necessary to shape the wing! 021 AIRFRAME AND SYSTEMS 35 WING LOADS Maximum Zero Fuel Weight (MZFW) This concept arises from the distribution of lift along the wing, which causes it to flex upwards. MZFW is the maximum allowable weight of the airplane with residual (unused) fuel in the tank Higher weight The fuel distributed on the wings helps relieve this bending moment Higher wing lift Higher bending loads 021 AIRFRAME AND SYSTEMS 36 18 11/15/2019 WING LOADS 021 AIRFRAME AND SYSTEMS 37 WING LOADS Typical wing structure The basic component of a typical wing are the following: Skin Spars Ribs Stringers/Stiffners 021 AIRFRAME AND SYSTEMS 38 19 11/15/2019 WING STRUCTURE Basic wing structure Spars Resists to bending and shear loads The cap resists to the bending loads and the web resist to shear loads 021 AIRFRAME AND SYSTEMS 39 WING STRUCTURE Typical wing structure Spars Small planes only have one spar Medium planes have 2 spars Larger planes have 3 or more spars 021 AIRFRAME AND SYSTEMS 40 20 11/15/2019 WING STRUCTURE Typical wing structure Spars Wing with 3 spars: The front spar resists to the bending backward The main spar is the principal structural element of a conventional wing The rear spar supports the control surfaces and the loads transferred to the wing 021 AIRFRAME AND SYSTEMS 41 WING STRUCTURE Typical wing structure Skin Impermeable surface that supports the pressure loads Supports bending and shear Stringers provides stability and ribs defines the shape of the wing 021 AIRFRAME AND SYSTEMS 42 21 11/15/2019 WING STRUCTURE Typical wing structure Ribs Responsible for the shape of the wing – and for the aerodynamics properties Transmits the loads along the chord in to the main spar Supports the skin and stringers 021 AIRFRAME AND SYSTEMS 43 WING STRUCTURE Typical wing structure Stringers Reinforces the wing skin along the span wise Stabilized by the ribs The stringers are connected to the skin by rivets or adhesive 021 AIRFRAME AND SYSTEMS 44 22 11/15/2019 WING STRUCTURE Typical wing structure Torsion Box It is not a structural element in itself, it results from the arrangement of the ribs, spars and shell which form boxes along the wing. The torsion box is essential to give torsional stiffness to the wing, prevent it from twisting, increase or decrease the angle of attack. 021 AIRFRAME AND SYSTEMS 45 WING STRUCTURE Example 021 AIRFRAME AND SYSTEMS 46 23 11/15/2019 WING EQUIPMENT The wing is used as support for different components, of which the following stand out: Landing gear Engines Control surfaces Fuel tank They produce concentrated loads on the wing and openings in the skin and internal structure, which require additional structural reinforcements. 021 AIRFRAME AND SYSTEMS 47 WING EQUIPMENT Despite the need for structural reinforcements, the support of equipment on the wing structure can be beneficial – it helps alleviate the bending efforts resulting from the lift distribution. Wing fuel is the ultimate fuel! 021 AIRFRAME AND SYSTEMS 48 24 11/15/2019 WING AERO ELASTIC EFFECTS When the aerodynamic loads are so high, capable of deforming the structure? If the deformations are such that the angle of attack is affected, the results can be catastrophic! Aero elastic Phenomena Divergence Command Reversal Flutter 021 AIRFRAME AND SYSTEMS 49 WING AERO ELASTIC EFFECTS DIVERGENCE Divergence occurs when, by the action of an aerodynamic force, the wing twists leading to a variation of angle of attack that promotes the increase of aerodynamic force. The increased force will make the wing twist even further, magnifying the effect until a structural failure occurs. It happens above a certain speed. 021 AIRFRAME AND SYSTEMS 50 25 11/15/2019 WING AERO ELASTIC EFFECTS COMMAND REVERSAL The force created by the deflection of a control may be such that the deformation of the fixed surface to which it is attached leads to an effect contrary to that which is intended to be produced. The most common example is the aileron reversal. It happens above a certain speed. 021 AIRFRAME AND SYSTEMS 51 WING AERO ELASTIC EFFECTS FLUTTER Unlike the previous two cases, this is a dynamic effect, involving oscillations. These oscillations result from the coupling between the twist and the flexion of the wing - one movement excites the other. Above a certain speed, the oscillations are no longer damped and can lead to structural failure. 021 AIRFRAME AND SYSTEMS 52 26 11/15/2019 WING AERO ELASTIC EFFECTS FLUTTER 021 AIRFRAME AND SYSTEMS 53 WING AERO ELASTIC EFFECTS FLUTTER It is possible to relegate this phenomenon to higher speeds: Increasing wing torsional stiffness The equipment supported by the wing must be installed in front of the bending axis The center of gravity of the fuel within the wing must be in front of the bending axis 021 AIRFRAME AND SYSTEMS 54 27 11/15/2019 021 AIRFRAME AND SYSTEMS 021 01 Systems Design, Loads, Stresses and maintenance 021 01 01 Systems design 021 01 02 Loads and Stress 021 01 03 Fatigue 021 01 04 Corrosion 021 01 05 Maintenance 021 02 Airframe 021 02 01 Construction and attachment methods 021 02 02 Materials 021 02 03 Aeroplane: wings, tail surfaces and control surfaces 021 02 04 Fuselage, landing gear, doors, floor, windscreen and Windows 021 02 05 Helicopter: flight controls structural aspects 021 02 06 Structural limitations 021 AIRFRAME AND SYSTEMS 55 Thank you. 28
