THE
PILOT
Aircraft
general
knowledge
ATPL
STUDENT
pilot
resume
all info you need to pass atpl exams
, AGK
System design, load, stress & maintenance
• Damage/fault tolerant design:
- Capability to withstand a certain amount of weakening of a structure without catastrophic failure
- Takes cracking of the structure into account
• Fail safe design:
- More than one load carrying component, parallel structural parts, load sharing
- Based on redundancy of components
- Does not imply that the system will never fail despite having backups
• Safe life design:
- Replacement of part after a given number of cycles/flight hours in use
- One load carrying component is sufficient provided it is strong enough
- Does not imply that the system will never fail in the safe life period
There is no most favourable design method, as each component varies
• Maintenance:
1. Hard time: Component overhauled/removed after a set number of hours/cycles regardless of condition
2. On condition: Monitoring of critical parameters & replacement of parts if a limit value is exceeded
• Stress: Force/area
1. Tension: Force resisting from being pulled apart
2. Torsion: Caused by twisting
3. Compression: Push force
4. Torque: Axial rotation force
5. Shear: Force parallel to cross section
6. Buckling: Effect of more than one force
• Strain:
- Deformation due to stress, expressed as a % change of dimension of original dimension
• Elastic deformation
- Tendency of material to return to its original state
- Temporary & reverses when load is removed
• Corrosion: Incorrect metallic bonding
1. Stress: Continuous tensile load + corrosion
2. Intergranular: Grain boundaries inside metal
• Fatigue: Material is continually loaded & unloaded & will eventually break even though load is the same
• Aircraft flies beyond certified load factor: Subject to permanent deformation
No effect Minor Major Hazardous Catastrophic
Qualitive None Probable Remote Extremely remote Extremely improbable
Quantative None 10-3 10-5 10-7 10-9
Flight crew None Slight workload Physical discomfort Physical distress Fatality/Incapacitation
Airplane margins None Slight reduction Significant reduction Large reduction Hull loss
Passengers Inconvenience Physical discomfort Physical distress Serious/fatal injury Multiple fatalities
Airframe
• Engine compartment decking & firewall: Stainless steel/titanium sheet
• Sandwich structure:
- Consists of two thin sheets separated with light core material
- Low mass high stiffness
- Stabilizes covering sheets
- Unsuitable for absorbing concentrated loads
- Does not use resin
• Composite structure:
- Consists of matrix & fibres
- Component strengths can be tailored to the direction of load, not the same in all directions
- Higher strength to weight ratio compared to other metal
• Truss type: Small light aircraft/training planes
• Monocoque:
- Takes all the load on a stressed skin
- Normally uses aluminium/magnesium alloy
• Semi-monocoque:
- Fuselage of transport airplanes
, - Consists of skin, frames & stringers
- Normally uses aluminium/magnesium alloy
• Cantilever:
- Attached to the aircraft at the wing root only (No struts/braces/wires)
- Vertical loads/bending moments highest at wing root
• Wings:
- Torsion box: Consists of spars, ribs, wing skin reinforced by stringers
- Ribs:
• Maintains aerodynamic shape
- Stringers:
• Assists skin to absorb longitudinal compressive loads
- Wing skin:
• When unable to bear load, it transfers them to the spar via ribs & stringers
• Bears cylindrical load during pressurization (TENSION)
- Spar:
• Bears most of the load
• Consists of web & girders (I-beam)
- In the air:
• Lift loads carried by upper/lower skin surfaces & spars
• Tension on lower surface & compression on upper surface
- On the ground:
• Tension in upper surface & compression on lower surface
- Wing bending moments:
• Reduced by installing “upfloat” ailerons, using fuselage fuel first while maintaining fuel in wings as long as
possible
• Torsion: Effect of aileron deflection or positive sweep (As the surfaces hit the air at non uniform levels a
twisting motion is induced)
• From wing root to the tip: First compression then tension
• Aerodynamic flutter:
- Caused by torsion & bending, COP ahead of COG
- Avoided by increasing torsional stiffness & adding balancing mass in front of control surface hinge
- Avoided by ensuring correct mass distribution within the control surface during design
- Wing bends downwards: Flutter may occur if the aileron deflects upwards as aileron COG is behind hinge line
- Wing bends upwards: Flutter may occur if the aileron deflects downwards as aileron COG is behind hinge line
• T – Tail aircraft:
- Vertical stabiliser Is not affected by influence of wing turbulence
• Fuselage:
- Consists of: skin, frames & stringers (No spars/girders)
- Pressurization load = Tension
- Shell structures transmit: Normal bending, tangent bending, tension & torsional stresses (NO SHEAR)
- Torque links: Most stress when making tight turns during taxiing, turning at a small radius
- Floor proximity emergency escape lights: Gives additional guidance during evacuation in reduced visibility
• Cockpit window:
- De-icing provided by electrical heating
- Some aircraft have speed restrictions related to bird impact when window heating inoperative
- Window heating improves strength of cockpit windows
- Cockpit side windows not provided with de-icing, only defoggers
- Made of: Glass & Inner surface made of soft polycarbonate laminate
- Green system “On” information light and an amber failure warning light
• Airplanes designed for long haul cannot be used for short haul flights as lifetime of fatigue sensitive parts have been
determined on a load spectrum
• MZFM: Maximum zero fuel mass – Total maximum permissible mass of the aircraft without usable fuel
Hydraulics
• Pascal’s law: Pressure exerted on hydraulic fluid within an enclosed system the pressure will increase equally throughout
the fluid, and act at right angles to the container walls. Force/area\
• Area(A) x distance(A) = Area(B) x distance(B)
• Most common:
- Phosphate ether based fluids (Skydrol) is purple
- Synthetic oil (Maybe mineral). Synthetic = Highest resistance against cavitation
PILOT
Aircraft
general
knowledge
ATPL
STUDENT
pilot
resume
all info you need to pass atpl exams
, AGK
System design, load, stress & maintenance
• Damage/fault tolerant design:
- Capability to withstand a certain amount of weakening of a structure without catastrophic failure
- Takes cracking of the structure into account
• Fail safe design:
- More than one load carrying component, parallel structural parts, load sharing
- Based on redundancy of components
- Does not imply that the system will never fail despite having backups
• Safe life design:
- Replacement of part after a given number of cycles/flight hours in use
- One load carrying component is sufficient provided it is strong enough
- Does not imply that the system will never fail in the safe life period
There is no most favourable design method, as each component varies
• Maintenance:
1. Hard time: Component overhauled/removed after a set number of hours/cycles regardless of condition
2. On condition: Monitoring of critical parameters & replacement of parts if a limit value is exceeded
• Stress: Force/area
1. Tension: Force resisting from being pulled apart
2. Torsion: Caused by twisting
3. Compression: Push force
4. Torque: Axial rotation force
5. Shear: Force parallel to cross section
6. Buckling: Effect of more than one force
• Strain:
- Deformation due to stress, expressed as a % change of dimension of original dimension
• Elastic deformation
- Tendency of material to return to its original state
- Temporary & reverses when load is removed
• Corrosion: Incorrect metallic bonding
1. Stress: Continuous tensile load + corrosion
2. Intergranular: Grain boundaries inside metal
• Fatigue: Material is continually loaded & unloaded & will eventually break even though load is the same
• Aircraft flies beyond certified load factor: Subject to permanent deformation
No effect Minor Major Hazardous Catastrophic
Qualitive None Probable Remote Extremely remote Extremely improbable
Quantative None 10-3 10-5 10-7 10-9
Flight crew None Slight workload Physical discomfort Physical distress Fatality/Incapacitation
Airplane margins None Slight reduction Significant reduction Large reduction Hull loss
Passengers Inconvenience Physical discomfort Physical distress Serious/fatal injury Multiple fatalities
Airframe
• Engine compartment decking & firewall: Stainless steel/titanium sheet
• Sandwich structure:
- Consists of two thin sheets separated with light core material
- Low mass high stiffness
- Stabilizes covering sheets
- Unsuitable for absorbing concentrated loads
- Does not use resin
• Composite structure:
- Consists of matrix & fibres
- Component strengths can be tailored to the direction of load, not the same in all directions
- Higher strength to weight ratio compared to other metal
• Truss type: Small light aircraft/training planes
• Monocoque:
- Takes all the load on a stressed skin
- Normally uses aluminium/magnesium alloy
• Semi-monocoque:
- Fuselage of transport airplanes
, - Consists of skin, frames & stringers
- Normally uses aluminium/magnesium alloy
• Cantilever:
- Attached to the aircraft at the wing root only (No struts/braces/wires)
- Vertical loads/bending moments highest at wing root
• Wings:
- Torsion box: Consists of spars, ribs, wing skin reinforced by stringers
- Ribs:
• Maintains aerodynamic shape
- Stringers:
• Assists skin to absorb longitudinal compressive loads
- Wing skin:
• When unable to bear load, it transfers them to the spar via ribs & stringers
• Bears cylindrical load during pressurization (TENSION)
- Spar:
• Bears most of the load
• Consists of web & girders (I-beam)
- In the air:
• Lift loads carried by upper/lower skin surfaces & spars
• Tension on lower surface & compression on upper surface
- On the ground:
• Tension in upper surface & compression on lower surface
- Wing bending moments:
• Reduced by installing “upfloat” ailerons, using fuselage fuel first while maintaining fuel in wings as long as
possible
• Torsion: Effect of aileron deflection or positive sweep (As the surfaces hit the air at non uniform levels a
twisting motion is induced)
• From wing root to the tip: First compression then tension
• Aerodynamic flutter:
- Caused by torsion & bending, COP ahead of COG
- Avoided by increasing torsional stiffness & adding balancing mass in front of control surface hinge
- Avoided by ensuring correct mass distribution within the control surface during design
- Wing bends downwards: Flutter may occur if the aileron deflects upwards as aileron COG is behind hinge line
- Wing bends upwards: Flutter may occur if the aileron deflects downwards as aileron COG is behind hinge line
• T – Tail aircraft:
- Vertical stabiliser Is not affected by influence of wing turbulence
• Fuselage:
- Consists of: skin, frames & stringers (No spars/girders)
- Pressurization load = Tension
- Shell structures transmit: Normal bending, tangent bending, tension & torsional stresses (NO SHEAR)
- Torque links: Most stress when making tight turns during taxiing, turning at a small radius
- Floor proximity emergency escape lights: Gives additional guidance during evacuation in reduced visibility
• Cockpit window:
- De-icing provided by electrical heating
- Some aircraft have speed restrictions related to bird impact when window heating inoperative
- Window heating improves strength of cockpit windows
- Cockpit side windows not provided with de-icing, only defoggers
- Made of: Glass & Inner surface made of soft polycarbonate laminate
- Green system “On” information light and an amber failure warning light
• Airplanes designed for long haul cannot be used for short haul flights as lifetime of fatigue sensitive parts have been
determined on a load spectrum
• MZFM: Maximum zero fuel mass – Total maximum permissible mass of the aircraft without usable fuel
Hydraulics
• Pascal’s law: Pressure exerted on hydraulic fluid within an enclosed system the pressure will increase equally throughout
the fluid, and act at right angles to the container walls. Force/area\
• Area(A) x distance(A) = Area(B) x distance(B)
• Most common:
- Phosphate ether based fluids (Skydrol) is purple
- Synthetic oil (Maybe mineral). Synthetic = Highest resistance against cavitation
