Which of these statements about structural design principles are correct or incorrect I In structural design fail safe implies parallel structural parts II In structural design safe life implies the ? Registration > lift > off
I correct ii incorrect.
in a 'fail safe' construction components were designed in a way that loads are shared among adjacent components
if one component fails adjacent components take up load a limited period of time enough to allow detection at next periodic inspection
the philosophy of 'fail safe' to anticipate a possible failure with a minimum of harm
in a 'safe life' construction components are given a time period and/or number of cycles (x landings x engine starts) must be removed from service when appropriate criteria are met
the 'safe life' design technique employed in critical systems which are either very difficult to repair or may cause severe damage to life property
statement ii incorrect because you can not guarantee that a part will definitely not (will never ) fail within its calculated number of cycles or its period.
On modern transport aircraft cockpit windows are protected against icing by ?
On modern transport aircraft cockpit windows are protected against icing I correct ii incorrect.
on boeing 777 example windshield consists of three plies of glass with exterior surface anti icing exterior interior surface anti fogging protection the plies are comprised of chemically tempered glass separated interlayers of polyvinyl butyral urethane the glass interlayer materials are bonded together in an autoclave under specific time temperature pressure conditions
the window designed to withstand fail safe pressure loads with a single glass ply failed normal pressure loads with multiple glass plies failed the windshield heat system normally powered whenever aircraft electrical system powered
the anti ice anti fog elements are connected to separate power sensor terminal blocks located on upper lower edges of windshield.
In flight a cantilever wing of an aeroplane containing fuel is subjected to vertical loads that produce a bending moment which is ?
In flight a cantilever wing of an aeroplane containing fuel subjected to vertical loads that produce a bending moment which Highest at wing root. A good example a cantilever wing airplane the cessna 177
on ground in flight highest bending moment at wing root since there no external supports as a cessna 172 example
. The purpose of static wick dischargers to Dissipate static charge of aircraft in flight thus avoiding radio interference as a result of static electricity. The goal to maintain electrical airframe potential at around 10000 volts via static dischargers (by providing a path the electrons)
example of static dischargers on a wing
without static dischargers electrical airframe potential would rise up to a value 10 times higher would disturb and/or damage onboard equipment. Electrical bonding of an aircraft used to 1 protect aircraft against lightning effects 2 reset electrostatic potential of aircraft to a value approximating 0 volt3 reduce radio interference on radio communication systems4 set aircraft to a single potentialthe combination regrouping all correct statements Dissipate static charge of aircraft in flight thus avoiding radio interference as a result of static electricity. Good electrical bonding will reduce damage to airframe structure in event of a lightning strike
bonding the electrical interconnection of metallic aircraft parts (normally at earth potential) the safe distribution of electrical charges currents
bonding provides a means of protection against charges as a result of build up of precipitation static electrostatic induction as a result of lightning strikes so that safety of aircraft or its occupants not endangered
bonding reduces possibility of electric shock from electrical supply system reduces interference with functioning of essential services (e g radio communications navigational aids) provides a low resistance electrical return path electric current in earth return systems. One indication of inadequate bonding of aircraft components may be Static noises can be heard on radio. Bonding the electrical interconnection of metallic aircraft parts (normally at earth potential) the safe distribution of electrical charges currents
bonding provides a means of protection against charges as a result of build up of precipitation static electrostatic induction as a result of lightning strikes so that safety of aircraft or its occupants not endangered
bonding reduces possibility of electric shock from electrical supply system reduces interference with functioning of essential services (e g radio communications navigational aids) provides a low resistance electrical return path electric current in earth return systems. The reason the fact that an aeroplane designed long distances cannot simply be used short haul flights at higher frequencies that The lifetime of fatigue sensitive parts has been based on a determined load spectrum. Take example pressurization depressurizations cycles
the more cycles you do (short flights) more fatigue structure gets if you use an airbus a340 short hauls as aircraft has not been designed that it more susceptible to 'low cycle fatigue damage compared to an airbus a320
note once at cruise level fatigue remains same it not time related it cycle related
all nippon airways japan airlines are best known users the special boeing 747 400d (domestic) a high density seating model developed short haul domestic japanese flights the aircraft capable of seating a maximum of 568 passengers in a 2 class configuration or 660 passengers in a single class configuration the 400d lacks wing tip extensions winglets included on other variants allowing increased number of takeoffs landings lowering wing stresses the benefits of winglets would be minimal on short routes
the 747 400d also unusual in having more windows on both sides of upper deck than basic 400 series this allows additional seating all way down upper deck where a galley situated on most international models. 8 Engine compartment decking and firewalls are manufactured from Stainless steel or titanium sheet. Take example pressurization depressurizations cycles
the more cycles you do (short flights) more fatigue structure gets if you use an airbus a340 short hauls as aircraft has not been designed that it more susceptible to 'low cycle fatigue damage compared to an airbus a320
note once at cruise level fatigue remains same it not time related it cycle related
all nippon airways japan airlines are best known users the special boeing 747 400d (domestic) a high density seating model developed short haul domestic japanese flights the aircraft capable of seating a maximum of 568 passengers in a 2 class configuration or 660 passengers in a single class configuration the 400d lacks wing tip extensions winglets included on other variants allowing increased number of takeoffs landings lowering wing stresses the benefits of winglets would be minimal on short routes
the 747 400d also unusual in having more windows on both sides of upper deck than basic 400 series this allows additional seating all way down upper deck where a galley situated on most international models. 9 The inner surface of a heated windscreen of Stainless steel or titanium sheet. It not case all aircraft but most of time inner surface of a heated windscreen of soft polycarbonate or an equivalent product it allows high resistance very expandable seal regarding temperature change constraints. 10 The purpose of stringers used in fuselage construction to Assist skin withstand longitudinal compressive loads. It not case all aircraft but most of time inner surface of a heated windscreen of soft polycarbonate or an equivalent product it allows high resistance very expandable seal regarding temperature change constraints. 11 Significant torsion effects in a wing during flight can be caused Assist skin withstand longitudinal compressive loads. It not case all aircraft but most of time inner surface of a heated windscreen of soft polycarbonate or an equivalent product it allows high resistance very expandable seal regarding temperature change constraints. 12 The two deformation modes that cause wing flutter are Assist skin withstand longitudinal compressive loads. Flutter a divergent oscillatory motion of a control surface caused the interaction of aerodynamic forces inertia forces the stiffness of structure (it a combination of bending torsion of structure)
aero elastic coupling affects flutter characteristics
the risk of flutter increases as ias increases
if flutter occurs ias should be reduced
resistance to flutter increases with increasing wing stiffness. 13 One design method to avoid control surface flutter Ensuring correct mass distribution within control surface. Flutter a divergent oscillatory motion of a control surface caused the interaction of aerodynamic forces inertia forces the stiffness of structure (it a combination of bending torsion of structure)
aero elastic coupling affects flutter characteristics
the risk of flutter increases as ias increases
if flutter occurs ias should be reduced
resistance to flutter increases with increasing wing stiffness. 14 A composite structural component consists of Ensuring correct mass distribution within control surface. Flutter a divergent oscillatory motion of a control surface caused the interaction of aerodynamic forces inertia forces the stiffness of structure (it a combination of bending torsion of structure)
aero elastic coupling affects flutter characteristics
the risk of flutter increases as ias increases
if flutter occurs ias should be reduced
resistance to flutter increases with increasing wing stiffness. 15 The fuselage structure of a pressurised transport aeroplane an example of a Semi monocoque structure. An egg a good example of a monocoque structure monocoque means 'single shel
semi monocoque a compromise which uses longerons (stringers) to take some of strain sandwich structure a part of 'shel of an airframe
semi monocoque fuselage the standard construction in nowadays this has solved problem with thick of sheet of lining of monocoque structure this fuselage uses a thinner sheet the use of structural members between the members have function of step up union shape fuselage
semi monocoque structure on a modern pressurised transport aeroplane. 16 When a wing bends downwards aileron flutter might occur if aileron deflects Upwards because location of aileron centre of gravity lies behind hinge line. Flutter a dangerous phenomenon encountered in flexible structures subjected to aerodynamic forces as airspeed increases there may be a point at which structural damping insufficient to damp out motions which are increasing due to aerodynamic energy being added to airfoil this vibration can cause structural failure therefore considering flutter characteristics an essential part of designing an aircraft
if cg aft of torsional axis inertia causes cg of aileron to lag behind any movement of axis caused changes in lift this lag can cause still further changes in incidence hence lift making matter worse
by having cg on or forward of hinge (the torsion axis) now uses property of inertia to counter effect. 17 A structure in which skin takes all of load A monocoque structure. The monocoque design uses stressed skin to support almost all imposed loads this structure can be very strong but cannot tolerate dents or deformation of surface this characteristic easily demonstrated a thin aluminum beverage can you can exert considerable force to ends of can without causing any damage
however if side of can dented only slightly can will collapse easily the true monocoque construction mainly consists of skin formers bulkheads the formers bulkheads provide shape the fuselage
since no bracing members are present skin must be strong enough to keep fuselage rigid thus a significant problem involved in monocoque construction maintaining enough strength while keeping weight within allowable limits
due to limitations of monocoque design a semi monocoque structure used on many of today's aircraft. 18 A cantilever wing A wing attached to fuselage at wing root only. A good example a cantilever wing airplane the cessna 177
. 19 A non cantilever wing A wing supported braces or a strut connected to fuselage. A good example a cantilever wing airplane the cessna 177
. 20 A sandwich structural part Consists of two thin sheets separated a light core material. A good example a cantilever wing airplane the cessna 177
. Exclusive rights: Content under private and protected license, reproduction prohibited and prosecuted.
