Last Updated on 4 years by teboo
021 02 01 00 Attachment methods
021 02 01 01 Attachment methods and detecting the development of faulty attachments
(01) Describe the following attachment methods used for aircraft parts and components:
— riveting; Rivets are strong in shear, the holes can be stress points. Condition of the paint is a good indicator of fretting. Mushroom rivets are aerodynamically quiet.
— welding; Bad joints can encourage fatigue. Fusion welding and gas welding.
— bolting; Disassembly possible and secured with lock wire.
— pinning; Straight or tapered fastening to attach/locate.
— adhesives (bonding); Pressure and heat supplied to ensure a good and stable bond. Stronger and lighter than rivets. Has been used to attached strengthening stingers and doublers to structures.
— screwing. Is screwing
(02) Explain how the development of a faulty attachment between aircraft parts or components can be detected by a pilot during the pre-flight inspection. Faulty attachments can be pickled up on a thorough pre-flight. Bits can be visually tested or wiggled by hand.
021 02 02 00 Materials
021 02 02 01 Composite and other materials
(01) X Explain the principle of a composite material, and give examples of typical non-metallic materials used on aircraft:Composites are based on two or more materials, one is the matrix and the other is the fibre. The fibre provides the strength and the matrix fills in and hold everything together. Examples are
carbon;
— glass;
— Kevlar aramid;
— resin or filler.
(02) X State the advantages and disadvantages of composite materials compared with metal alloys by considering the following:
— strength-to-weight ratio; Is excellent compare to metals, carbon or graphite typically is 20x stronger than metal
— capability to tailor the strength to the direction of the load; Parts can be made specifically to take the load in the direction it is needed.
— stiffness;
— electrical conductivity (lightning); Carbon has excellent electrical conductivity which is good for mild lightening, other composites have no conductivity and need lightening conductors built in.
— resistance to fatigue and corrosion; Composites are good at resisting, however. hail and sand can erode it.
— resistance to cost; Can be expensive due to the custom nature of the parts an involve expensive fabrication plants.
— discovering damage during a pre-flight inspection. Often difficult to detect. Moisture can get into gaps, expand on freezing at cause delimitation.
(03) State that several types of materials are used on aircraft and that they are chosen based on type of structure or component and the required/desired material properties. Ok then.
021 02 03 00 Aeroplane: wings, tail surfaces and control surfaces
021 02 03 01 Design
(01) Describe the following types of design and explain their advantages and disadvantages:
— high-mounted wing; More aerodynamically stable, better downward vision, gravity fed fuel. But, reduced ground effect makes landing slightly more challenging, higher wings may need bracing meaning more drag. Reduced visibility when banking
— low-mounted wing; Better at landing, retractable gear easier and lighter. Good visibility in turns, but probably need a fuel pumping system .
— low- or mid-set tailplane; For aerodynamic reasons most jet transport planes is the default position
— T-tail. Common for regional high wing aircraft as it is kept out of the turbulent airflow of the wing giving more predictable handling characteristics. The disadvantage is it may loose all effectiveness at high angle of attack due to turbulent air.
021 02 03 02 Structural components
(01) Describe the function of the following structural components:
— spar and its components (web and girder or cap); Span-wise structural member to withstand bending loads and support the wing on the ground.
— rib; Provide aerodynamic shape normal to the spars, support a stressed skin.
— stringer; Along with the spars, they share loads. Can be bonded to the skin to help withstand buckling.
— skin; Skin provides a smooth aerodynamic cover and can also take loads.
— torsion box. Joins two or more spars together forming a rectangular box type structure, very resistant to twisting.
021 02 03 03 Loads, stresses and aeroelastic vibrations (flutter)
(01) Describe the vertical and horizontal loads on the ground and during normal flight.
On the ground upwards static force through the landing gear creates a downwards bending moment on the wing, in flight it is an upwards being force, or lift. Fuel can go some way to reduce the bending moment.
Swept back wings are subject to higher torsional loads as a lot of the lift is generated aft of the attachment.
Unsure of horizontal loads.
(02) Describe the vertical and horizontal loads during asymmetric flight following an engine failure for a multi-engine aeroplane, and how a pilot may potentially over stress the structure during the failure scenario. Asymmetric flight causes yaw which is dealt with but rudder and could cause large forces on the fin with potential damage.
(03) Explain the principle of flutter and resonance for the wing and control surfaces.
Undamped oscillation due to aerodynamic imbalance. When the frequencies match, flutter can result and can be quickly catastrophic.
(04) Explain the following countermeasures used to achieve stress relief and reduce resonance:
— chord-wise and span-wise position of masses (e.g. engines, fuel, balance masses for wing and control balance masses);
Forward mounting of engines on the wing.
Forward CG bias to wing fuel tanks.
— torsional stiffness; Tough enough to resist flutter but retaining enough flexibility to absorb energy and not fail.
— bending flexibility; Same as above.
— fuel-balancing procedures during flight (automatic or applied by the pilot).
Fuel can be moved around to adjust balance.
021 02 04 00 Fuselage, landing gear, doors, floor, windscreen and windows
021 02 04 01 Construction, functions, loads
(01) X Describe the following types of fuselage construction:
— monocoque, Shell, no internal structure. Load bearing skin
— semi-monocoque. As above but with light internal framework to ad strength.
(01) Describe the construction and the function of the following structural components of a fuselage:
- frames;
Or formers. Vertical structures, take major loads and define shape.
- bulkhead;
Like frames but solid, may have a door in.
- pressure bulkhead;
Same as above but act as a cap to help with pressurisation.
- stiffeners, stringers, longerons;
Provide the base for the skin. Stiffeners, similar to stringers. Stringers, span wise members that help prevent buckling. Longerons are beans in the fuselage, nose to tail and take the main bending loads. Like I beams.
- skin, doublers;
Skins, well, the skin. Can take loads as in stressed skin. Doublers are reinforcements around holes in the skin.
- floor suspension (crossbeams);
Provides a deck and also adds structural integrity.
- floor panels
Fixed to the cross beams…
- firewall.
A bulkhead to stop fire !
(03) Describe the loads on the fuselage due to pressurisation. Hoop stress, when pressurised the difference in air pressure acts equally to expand the fuselage, axial stress acts on the pressure bulkheads and try to elongate the fuselage.
(04) Describe the following loads on a main landing gear:
— touch-down loads (vertical and horizontal); • Compressive (static and on touchdown).
• Rearward bending.
• Side (during crosswind landings, take-offs, and taxiing).
— taxi loads on bogie gear (turns).
• Torsional (ground manoeuvring).
• Forwards (during push back).
(05) Describe the structural danger of a nose-wheel landing with respect to:
— fuselage loads; A nose wheel landing could bend a long fuselage.
— nose-wheel strut loads. Not built to take landing loads.
(06) Describe the structural danger of a tail strike with respect to:
— fuselage and aft bulkhead damage (pressurisation). If damaged could cause a catastrophic failure or explosive decompression.
(07) Describe the door and hatch construction for pressurised and unpressurised aeroplanes including:
— door and frame (plug type); A plug door is like a plug in a sink, pressure keeps it closed.
— hinge location; Forward fo light aircraft so aerodynamics prevent door fully opening.
— locking mechanism. Multiple bolts secure around the door.
(08) X Explain the advantages and disadvantages of the following fuselage cross sections:
— circular; This is an ideal shape for pressurized aircraft as the hoop stresses are spread evenly throughout the structure. It requires cheaper tooling and is a relatively easy build. Sometimes considerable amounts of space are wasted when certain passenger / cargo configurations have to be accommodated.
— double bubble; These are similar to a figure eight. They provide effective use of space for both passengers and cargo whilst not having the increased drag of a large circular fuselage, and they are cost effective.
Recent designs favour a side-by-side bubble. These allow for larger number of passengers for a given structural weight and are said to be very efficient due to reduced drag. Engines would be rear mounted
— oval; An oval is less efficient than a circular shape but is frequently used to complete pressure hull construction behind the rear bulkhead.
— rectangular. Non-pressurised a/c. Easy to construct but a high weight to strength ratio.
(09) Explain why flight-deck windows are constructed with different layers. For strength.
(10) Explain the function of window heating for structural purposes. To. make them more flexible so they can absorb more impact stress, like bird strikes etc. Heating failure may limit a/c speed.
(11) Explain the implication of a direct-vision window (see CS 25.773(b)(3)). Openable in flight (unpressurised obviously, for escape purposes and alternative forward vision for landing if delisting fails for example.
(12) Explain the need for an eye-reference position. A CS-25 requirement. It is so the pilots can align their eyes for the perfect position for landing.
(13) Explain the function of floor venting (blow-out panels). To ensure cabin and cargo compartments are at the same pressure, the floor would buckle if a door fails.
(14) Describe the construction and fitting of sliding doors. I can’t find anything about sliding doors.
021 02 06 00 Structural limitations
021 02 06 01 Maximum structural masses
(01) Define and explain the following maximum structural masses:
— maximum ramp mass; Maximum when it begins taxi, stress on oleos and shock absorbers etc.
— maximum take-off mass; Maximum mass on commencing of take off roll.
— maximum zero fuel mass; Doesn’t take a genius to work this one out.
— maximum landing mass. Less than MTOM due to higher forces on landing.
Remark: These limitations may also be found in the relevant part of Subjects 031 ‘Mass and balance’, 032 ‘Performance (aeroplane)’ and 034 ‘Performance (helicopter)’.
(02) Explain that airframe life is limited by fatigue, created by alternating stress and the number of load cycles. Mis-treatment and number of cycles dictates the life of the airframe as fatigue is cumulative.
