Which of these statements about structural design principles are correct or incorrect 1 In structural design FAIL SAFE implies the structure will ?
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Which of these statements about structural design principles are correct or incorrect 1 The damage tolerance principle takes cracking of the structure into account 2 The safe life principle is ?
Which of these statements about structural design principles are correct or incorrect 1 The DAMAGE TOLERANCE principle assumes cracks in the structure will never occur 2 The SAFE LIFE principle is ?
Which of these statements about structural design principles are correct or incorrect 1 in structural design fail safe implies structure will never fail 2 a safe life structure based on a declared time period or number of cycles I incorrect, ii correct, i incorrect, ii incorrect, i correct, ii incorrect, i correct, ii correct. 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 i incorrect because you can not guarantee that a part will definitely not (will never ) fail. 
According jar/cs 25 worst effect of a minor failure on occupants of an aeroplane excluding flight crew could be Physical discomfort, inconvenience, serious or fatal injury to a small number of passengers or cabin crew, physical distress, possibly including injuries. certification specifications large aeroplanes cs 25 (book 2 acceptable means of compliance). click here (see table on last page) PDF 021_CS25_Amendment_6 
According jar/cs 25 worst effect of a major failure on occupants of an aeroplane excluding flight crew could be Physical distress, possibly including injuries, inconvenience, serious or fatal injury to a small number of passengers or cabin crew, physical discomfort. certification specifications large aeroplanes cs 25 (book 2 acceptable means of compliance). click here (see table on last page) PDF 021_CS25_Amendment_6 
According jar/cs 25 worst effect of a catastrophic failure on aeroplane could be Hull loss, large reduction in functional capabilities or safety margins, significant reduction in functional capabilities or safety margins, slight reduction in functional capabilities or safety margins. certification specifications large aeroplanes cs 25 (book 2 acceptable means of compliance). click here (see table on last page) PDF 021_CS25_Amendment_6 Question Airframe 17 Answer 8
According jar/cs 25 allowable quantitative average failure probability per flight hour a hazardous failure should be on order of ^ means to power of Between ^7 ^9. (extremely remote), less than ^9. (extremely improbable), between ^5 ^7. (remote), between ^3 ^5. (probable) certification specifications large aeroplanes cs 25 (book 2 acceptable means of compliance). click here (see table on last page) PDF 021_CS25_Amendment_6 Question Airframe 17 Answer 9
According jar/cs 25 worst effect of a minor failure on flight crew could be A slight increase in workload, no effect on flight crew, physical distress or excessive workload, impairs ability to perform tasks, physical discomfort or a significant increase in workload. certification specifications large aeroplanes cs 25 (book 2 acceptable means of compliance). click here (see table on last page) PDF 021_CS25_Amendment_6 Question Airframe 17 Answer 10
According jar/cs 25 worst effect of a major failure on flight crew could be Physical discomfort or a significant increase in workload, no effect on flight crew, physical distress or excessive workload, impairs ability to perform tasks, a slight increase in workload. certification specifications large aeroplanes cs 25 (book 2 acceptable means of compliance). click here (see table on last page) PDF 021_CS25_Amendment_6 Question Airframe 17 Answer 11
According jar/cs 25 worst effect of a minor failure on aeroplane could be Slight reduction in functional capabilities or safety margins, no effect on operational capabilities or safety, large reduction in functional capabilities or safety margins, significant reduction in functional capabilities or safety margins. certification specifications large aeroplanes cs 25 (book 2 acceptable means of compliance). click here (see table on last page) PDF 021_CS25_Amendment_6 Question Airframe 17 Answer 12
According jar/cs 25 worst effect of a catastrophic failure on flight crew could be Fatalities or incapacitation, physical distress or excessive workload, impairs ability to perform tasks, physical discomfort or a significant increase in workload, a slight increase in workload. certification specifications large aeroplanes cs 25 (book 2 acceptable means of compliance). click here (see table on last page) PDF 021_CS25_Amendment_6 Question Airframe 17 Answer 13
The principle of damage tolerance in structural design of an aircraft based on Capability to withstand a certain amount of weakening of structure without catastrophic failure, replacement of parts after a given number of cycles or hours of use, fact that there no need to inspect structure, monitoring of critical parameters the replacement of parts if a limit value exceeded. Damage tolerant components will not have a specified life. continued operation based on frequent inspections takes cracking of structure into account. Question Airframe 17 Answer 14
The principle of 'on condition maintenance' based on Monitoring of critical parameters the replacement of parts if a limit value exceeded, replacement of parts after a given number of cycles or hours of use, redundancy of structure or equipment, capability to withstand a certain amount of weakening of structure without catastrophic failure. On condition maintenance a preventative process in which an item monitored either continuously or at specified periods. the item's performance compared to an appropriate standard in order to determine if it can continue in service. Question Airframe 17 Answer 15
The principle of 'fail safe' design of an aircraft based on Redundancy of structure or equipment, replacement of parts after a given number of cycles or hours of use, capability to withstand a certain amount of weakening of structure without catastrophic failure, monitoring of critical parameters the replacement of parts if a limit value exceeded. 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. Question Airframe 17 Answer 16
According jar/cs 25 worst effect of a catastrophic failure on occupants of an aeroplane excluding flight crew could be Multiple fatalities, serious or fatal injury to a small number of passengers or cabin crew, physical distress, possibly including injuries, physical discomfort. certification specifications large aeroplanes cs 25 (book 2 acceptable means of compliance). click here (see table on last page) PDF 021_CS25_Amendment_6 Question Airframe 17 Answer 17
A safe life aircraft structural component May be used during a declared number of cycles or flight hours, should have enough strength during whole lifetime of an aircraft, so strong that it never will fail during a declared time period, has parallel load paths. 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. Question Airframe 17 Answer 18
Whilst stationary on ground in a hangar most important loads on a cantilever wing are Tension in upper surface, compression in lower surface, tension in both upper the lower surfaces, compression in upper surface, tension in lower surface, compression in both upper the lower surfaces. Howarthson stationary on ground, wings are drooping under gravity, stretching top skin compressing bottom skin. in flight lift pulling wings up, stretching bottom compressing top. Question Airframe 17 Answer 19
In straight and level flight most important loads on a cantilever wing are Compression in upper surface, tension in lower surface, tension in upper surface, compression in lower surface, compression in both upper the lower surfaces, tension in both upper the lower surfaces. The most important loads on a cantilever wing (in flight) are compression in upper surface, tension in lower surface. on ground, it's opposite. Question Airframe 17 Answer 20
Define term 'fatigue' If a material continually loaded unloaded it will eventually break even though load remains same, a one off loading that breaks material, a loading on material but it returns fully to its former state when load removed, material suffers progressively more permanent damage each time that it loaded unloaded. The life of an airframe limited fatigue, caused the load cycles imposed during takeoff, landing pressurisation. this life has been calculated over years using different design philosophies, these being 'safe life', 'fail safe' 'damage tolerant'. Question Airframe 17 Answer 21
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 structure will never fail during a declared time period or number of cycles I correct, ii incorrect, i incorrect, ii incorrect, i correct, ii correct, i incorrect, ii correct. 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. Question Airframe 17 Answer 22
At point 1 load moment 2760 Tension, shear, compression, torsion. Question Airframe 17 Answer 23
On modern transport aircraft cockpit windows are protected against icing Electric heating, anti icing fluid, vinyl coating, rain repellent system. 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. Question Airframe 17 Answer 24
In flight a cantilever wing of an aeroplane containing fuel subjected to vertical loads that produce a bending moment which Highest at wing root, equal to zero fuel weight multiplied the span, equal to half weight of aircraft multiplied the semi span, lowest 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 Question Airframe 17 Answer 25
The purpose of static wick dischargers to Dissipate static charge of aircraft in flight thus avoiding radio interference as a result of static electricity, dissipate static charge from aircraft skin after landing, provide a path to ground static charges when refuelling, be able to fly higher because of less electrical friction. 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. Question Airframe 17 Answer 26
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 , 3 4,, 2 3, 3 4, 2 4 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. Question Airframe 17 Answer 27
One indication of inadequate bonding of aircraft components may be Static noises can be heard on radio, there interference on vor receiver, a circuit breaker pops out, there heavy corrosion on fuselage skin mountings. 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. Question Airframe 17 Answer 28
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, procedures checklists this kind of aeroplanes will take too much time, these aeroplanes often consume too much fuel on short haul flights, in that case some fuel tanks remain empty during whole flight, which stresses aeroplane's structure in an unacceptable way. 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. Question Airframe 17 Answer 29
Engine compartment decking and firewalls are manufactured from Stainless steel or titanium sheet, composite materials such as carbon, kevlar fibre glass, aluminium alloy sheet, asbestos blankets. Question Airframe 17 Answer 30
The inner surface of a heated windscreen of Soft polycarbonate, triplex, glass, hard perspex. 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. Question Airframe 17 Answer 31
The purpose of stringers used in fuselage construction to Assist skin withstand longitudinal compressive loads, withstand shear stresses, provide sound thermal isolation, carry loads due to pressurisation convert them into tensile stress. Question Airframe 17 Answer 32
Significant torsion effects in a wing during flight can be caused Aileron deflection, wing tip vortices, propwash, wing dihedral. Question Airframe 17 Answer 33
The two deformation modes that cause wing flutter are Torsion bending, torsion shearing, bending elongation, shearing elongation. 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. Question Airframe 17 Answer 34
One design method to avoid control surface flutter Ensuring correct mass distribution within control surface, through correct use of balance tabs, through correct use of trim tabs, providing wing structure with sufficient flexibility. Question Airframe 17 Answer 35
A composite structural component consists of A matrix fibres, two thin metal sheets a light core material, aluminium alloy with a covering layer of pure aluminium, two metal sheets bonded together. Question Airframe 17 Answer 36
The fuselage structure of a pressurised transport aeroplane an example of a Semi monocoque structure, truss type structure, pure monocoque structure, sandwich 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. Question Airframe 17 Answer 37
When a wing bends downwards aileron flutter might occur if aileron deflects Upwards, because location of aileron centre of gravity lies behind hinge line, upwards, because location of aileron centre of gravity lies in front of hinge line, downwards, because location of aileron centre of gravity lies behind hinge line, downwards, because location of aileron centre of gravity lies in front of 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. Question Airframe 17 Answer 38
A structure in which skin takes all of load A monocoque structure, a semi monocoque structure, a semi braced structure, a box 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. Question Airframe 17 Answer 39
A cantilever wing A wing attached to fuselage at wing root only, a wing planform other than rectangular, a high wing configuration, a low wing configuration. A good example a cantilever wing airplane the cessna 177 Question Airframe 17 Answer 40
A non cantilever wing A wing supported braces or a strut connected to fuselage, a wing planform other than rectangular, a high wing configuration, a low wing configuration.
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