Structures and Design Part 1 1Aero Flashcards
1
Q
is the intellectual engineering process of creating on paper (or on a computer screen)
A
Airplane Design
2
Q
These are:
* Payload and type
* Range and/or loiter requirements
* Cruise speed and altitude
* Field length for take-off and landing
* Fuel reserves
* Climb requirements
* Maneuvering requirements
* Certification base (experimental, FAR 23, FAR 25, military)
A
Design Profile
3
Q
How many design requirements are there?
A
12
4
Q
These are what?
1. Range.
2. Take-off distance.
3. Stalling velocity.
4. Endurance [usually important for reconnaissance airplanes; an overall dominating factor for the new group of very high-altitude uninhabited air vehicles (UAVs) that are of great interest at present].
5. Maximum velocity.
6. Rate of climb.
7. For dogfighting combat aircraft, maximum tum rate and sometimes minimum tum radius.
8. Maximum load factor.
9. Service ceiling.
10. Cost.
11. Reliability and maintainability.
12. Maximum size (so that the airplane will fit inside standard hangars and/or be able to fit in a standard gate at airline terminals).
A
Design Requirements
5
Q
What is the starting point in aircraft design?
A
Design Concept
6
Q
- dynamic and fluid multidisciplinary design process
- low level of detail
A
Conceptual Design
7
Q
- Large number design alternatives
- guide and evaluate design requirements of the overall aircraft contributors
A
Conceptual Design
8
Q
- study of “global” or significant interactions
- small, self- considerations group of contributors
A
Conceptual Design
9
Q
- major configurations fixed
- occasional reshapes of the overall design
A
Preliminary Design
10
Q
- increasing level of detail and of understanding of the design
- commencement of sub-system analysis and design by specialists
A
Preliminary Design
11
Q
- validation of the aircraft concept (predictions of the conceptual design phase)
A
Preliminary Design
12
Q
*full-scale development by large number of monodisciplinary designers and analysts
*ramified organisational structure
A
Detail Design
13
Q
*High level of detail (analysis and design)
*High level of confidence required regular
A
Detail Design
14
Q
*Regular checks of design goals
*field test result (esp. of components) become available
A
Detail Design
15
Q
What is the seven intellectual pivot points for conceptual design?
A
- Requirements
- Weight of the airplane - first estimate
- Critical performance parameters
-CL max
-L/D
-Wing Loading
-Thrust to weight ratio T/W - Configuration Layout - shape and size of the airplane on a drawing ( or computer screen)
- Better weight estimate
- Performace analysis
- Optimization - is it the best design?
16
Q
These are what?
-CL max Maximum coefficient of lift
-L/D Lift to drag ratio
-Wing Loading W/S
-Thrust to weight ratio T/W
A
Critical Performace Parameters
17
Q
shape and size of the airplane on a drawing ( or computer screen)
A
Configuration Layout
18
Q
Any deformable solid body which is capable of carrying loads and transmitting these loads to other parts of the body
A
Structural System
19
Q
Are one-dimensional structural members which are capable of carrying and transmitting bending, shearing, torsional, and axial loads or a combination of all four.
A
Bar elements
20
Q
Bars which are capable of carrying only axial loads are referred to as axial rods or two-force members.
A
Bar elements
21
Q
Structural systems constructed entirely out of axial rods are called
A
Trusses
22
Q
frequently are used in many atmospheric, sea, and land based structures, since simple tension or compression members are usually the lightest for transmitting forces.
A
Trusses
23
Q
Are two dimensional extensions of bar elements.
A
Plate elements
24
Q
Plates made to carry only in-plane axial loads are called
A
membranes.
25
Those which are capable of carrying only in-plane shearing loads are referred to as
shear panels
26
frequently these are found in missile fins, aircraft wing, and tail surfaces.
shear panels
27
are curved plate elements which occupy a space. Fuselages, building domes, pressure vessels, etc., are typical examples of shells.
Shell elements
28
Fuselages, building domes, pressure vessels, etc., are typical examples of
shells
29
those loads which are produced by surface contact. Examples are dynamic and/ or static pressures.
Surface load
30
If the area of contact is very small, then the load is said to be concentrated; otherwise, it is called a
distributed load.
31
Loads which depend on body volume are called. Examples are inertial, magnetic, and gravitational forces.
Body loads
32
Generally, these loads are assumed to be distributed over the entire volume of the body
Body loads
33
are time dependent, whereas static loads are independent.
Dynamic loads
34
are created on a restrained structure by a uniform and/or nonuniform temperature change
Thermal loads
35
may be defined as a force whose vector representation lies in and parallel to the plane of the cut.
Bending moment
36
is a force whose vector representation is normal to that cut.
Torque
37
is a force which lies in and is parallel to the plane of the cut.
Shear load
38
is a force which acts normal to the plane of the cut
Axial loads
39
A structure is said to be (blank) if all its external reactions and the internal loads on its members can be obtained by utilizing only the static equations of equilibrium.
Determinate
40
A structure is said to be determinate if all its external reactions and the internal loads on its members can be obtained by utilizing only the static equations of equilibrium. Otherwise the structure is said to be
statically indeterminate (redundant structure)
41
lift, drag, and pitching-moment force distributions for the complete aircraft with the horizontal tail removed, through the range of angles of attack from the negative stalling angles to the positive stalling angle. Are the?
The first aerodynamic data required for the structural system analysis
42
loads used by civil agencies or loads used by military agencies are the maximum anticipated loads in the entire service life-span of the vehicle.
Limit loads/ Applied loads
43
commonly referred to as design loads, are the limit loads multiplied by a factor of safety (FS):
The ultimate loads
44
Factor Safety is equal to
ultimate load / limit load
45
is a factor by which basic loads on a vehicle are multiplied to obtain the limit loads
Limit load factor
46
is a factor by which basic vehicle loads are multiplied to obtain the ultimate loads; in other words, it is the product of the limit load factor and the factor of safety.
Ultimate load factor
47
is obtained in a pullout at the highest possible angle of attack on the wing.
Positive High Angle of Attack (PHAA) condition
48
The lift and drag forces are perpendicular and parallel respectively, to the relative wind, which is shown as horizontal.
Positive High Angle of Attack (PHAA) condition
49
the wing has the smallest possible angle of attack at which the lift corresponding to the limit-load factor may be developed.
Positive Low Angle of Attack (PLAA) condition
50
For a given lift on the wing, the angle of attack decreases as the indicated airspeed increases,
Positive Low Angle of Attack (PLAA) condition
51
condition corresponds to the maximum indicated airspeed at which the airplane will dive.
Positive Low Angle of Attack (PLAA) condition
52
This condition represents an upward acceleration at its design gliding speed Vg
Positive Low Angle of Attack (PLAA) condition
53
design gliding speed
Vg
54
occurs in intentional flight maneuvers in which the air loads on the wing are down or when the airplane strikes sudden downdrafts while in level flight
Negative High Angle of Attack (NHAA) condition
55
In this condition usually the wing is assumed to be at the negative stalling angle of attack for steady flow conditions.
Negative High Angle of Attack (NHAA) condition
56
occurs at the diving-speed limit of the airplane.
Negative Low Angle of Attack (NLAA) condition
57
This condition may occur in an intentional maneuver producing a negative load factor or in a negative gust condition.
Negative Low Angle of Attack (NLAA) condition
58
This condition allows for the effect of a sudden decrease in angle of attack while flying at the speed of Vg
Negative Low Angle of Attack (NLAA) condition
59
The (blank) load factors on an aircraft are greater when it is flying at the minimum flying weight than they are at the gross-weight condition.
gust load factors
60
A critical load-bearing structure on an aircraft
Primary Structure
61
If this structure is severely damaged, the aircraft cannot fly
Primary Structure
62
Structural elements mainly provide enhanced aerodynamics
Secondary Structure
63
a rigid framework made up of members such as beams, struts, and bars to resist deformation by applied loads.
Truss Type
64
Aircraft Structures where The skin carries all the load
Monocoque
65
Aircraft Structures where Unstiffened Shell. Must be relatively thick to resist bending, compressive, and torsional loads
Monocoque
66
Aircraft Structures where Consist of skin and frames/formers/ bulkhead
Monocoque
67
Construction with stiffening members that may also be required to diffuse concentrated loads into the cover
Semi-Monocoque
68
More efficient type of construction that permits much thinner covering shell
Semi-Monocoque
69
Reacts the applied torsion and shear forces transmits aerodynamic forces to the longitudinal and transverse supporting members
Skin
70
Acts with longitudinal members in resisting the applied bending and axial loads
Skin
71
Acts with the transverse members in reacting the hoop, or circumferential, load when the structure is pressurized
Skin
72
* Resist bending and axial loads
* Form the wing box for stable torsion resistance
Spar
73
Resist bending and axial loads along with the skin
Stiffener and Stringers
74
Divide the skin into small panels and thereby increase its buckling and failing stresses
Stiffener and Stringers
75
Act with the skin in resisting axial loads caused by pressurization
Stiffener and Stringers
76
Main longitudinal member of a fuselage or nacelle.
Longeron
77
Member taking a tensile load.
Tie Rod (Tension Rod)
78
Member taking a compression load.
Strut
79
Structure where loads are shared between skin and framework.
Stressed skin
80
A partition within the structure. Usually lateral but can be longitudinal.
Bulkhead
81
If it forms the boundary of pressurized structure it is called
pressure bulkhead
82
A reinforcing member normally placed at right angles to the path of an anticipated crack which will reduce the rate of further propagation.
Crack stopper
83
A flat sheet triangular in shape used to reinforce the corners of structure.
Gussets
84
structural element frequently used to carry the fuselage bending loads through the portion of the lower fuselage which is cut up by the wheel wells.
Keelson/Keel beam
85
Profile Drag + Induced Drag is equal to
Total Drag
86
What formula is this 𝑪𝑫=𝑪𝑫𝒐+𝑪𝑫𝒊
Total Drag
87
Drag induced while producing lift
This type of drag decreases as speed increases
Induced Drag
88
Drag produced by shape and form of the aircraft
Profile / Form Drag
89
This type of drag increases as speed increases
Part of this drag is interference drag and exceedance drag
Profile / Form Drag
90
Drag is generated by the mixing of airflow streams between airframe components, such as the wing and the fuselage, or the landing gear strut and the fuselage.
Interference Drag
91
Drag produced due to surface roughness. Could be reduce by installing flush fasteners or using flush repair or application of filleting sealants
Exceedance Drag
92
Fuselage Shape Where:
- Efficient Structural Design
- Offers theoretically greater strength for shell structure
- Inefficient in availability of useful shape
Circular Cross Section
93
Fuselage Shape Where:
- Permits the most economical use of the space
- Not Suitable for shell structures
Rectangular Cross Section
94
Fuselage Shape Where:
- Best Compromise between circular and rectangular cross section
Oval/Elliptical Cross Section
95
the primary function of the (blank) are:
1. Maintain the shape of the fuselage
2. To sustain concentrated loads imposed
3. Serve as attachments for equipment, flooring, and the like
4. Transmit the loads to adjacent structural members
transverse fuselage frames
96
1. Serve mainly to maintain the shape of the fuselage
2. These are not subjected to stress unless distortion of the entire adjacent structure has taken place
Simple Frames
97
1. Serve to act as anchorage for medium weight equipment, control system and the like.
2. Similar simple frames but must be reinforced locally to carry the load and reduce deflection to a minimum
Intermediate Frames
98
1. Additional brackets may have to be introduced and tied in with the longitudinal stingers as well as the frames
2. These are not subjected to stress unless distortion of the entire adjacent structure has taken place
Intermediate Frames
99
1. To which large external loads are supplied through the landing gear, powerplant, or wing structure.
Main Frames
100
1. These are usually two in number, spaced a small distance apart and designed so as to take fittings to serve as carry through members
2. Act as the main transverse load carrying member
Main Frames
101
Since the fuselage is essentially a beam, the longitudinal stringers serve an important function in that they, along with the effective width of sheet covering, are the main bending elements of the structure.
Stringers
102
are the main bending elements, they should be continuous and therefore pass through the transverse frame
stringers
103
Since the openings have to be reinforced along the edges, it is desirable to have the top and bottom of all frames for such opening rest on
longitudinal stringers
104
spacing is determined by the number required for the loads imposed.
Longitudinal members are spaced from 6 to 12 inches apart around the largest cross section.
stringer
105
Since the cross section gradually decreases in size, the spacing is closer towards the tail post so that alternated members may be stopped at a forward frame.
It is desirable not to end all the longitudinal members at the same frame.
stringer
106
is essentially a beam that is subjected to shear, bending, and torsion imposed upon it by aerodynamics and inertia loads.
Wings
107
The center of gravity of the complete airplane is placed, usually at the maximum forward position of the center of pressure on the (blank) in order to get the desired stability
Mean Aerodynamic Chord
108
is difficult to determine unless the pressure distribution is know. Moreover, the pressure distribution varies with angle of attack. It is customary therefore to use the mean geometric chord of the wing instead.
mean aerodynamic chord
109
is determined for only 1/2 of the wing, either to the side of the fuselage, or up to the plane of symmetry for a parasol wing
The mean aerodynamic chord, or mean geometric chord
110
A wing with taper is a trade-off between elliptical (least induced drag, difficult to manufacture) and a rectangular wing (more induced drag, easy to manufacture).
Taper Ratio
111
More taper (smaller taper ratio) means weight is
less
112
More taper (small tip chord) is more conducive to
tip stall
113
Less taper means more fuel
volume
114
Tapered wings cost more than
untapered wings
115
For Aircraft operating at high subsonic speeds, the use of the sweepback in the planform of the wing is favored in order to increase the critical Mach number of the wing
Sweepback
116
Advantages:
▪ Delays drag divergence effects
▪ Used for balance
▪ Used for stability (dihedral effect)
▪ Better ride through turbulence characteristics
Sweepback
117
Disadvantages
Contributes to pitch up characteristics
▪ Performs less during take-off and landing
▪ Reduces subsonic lift
▪ Significant weight penalty
▪ Liable to tip stall
Sweepback
118
Increase lateral stability. Angle varies around 3 to 8 degrees
Dihedral
119
Decrease lateral stability/ Angle varies around 3 to 6 degrees
Also known as negative dihedral or drooped wing
Anhedral
120
is weight of aircraft over wing area (W/S)
Wing loading
121
Affects [a] take-off and landing field length, [b] cruise performance (L/D), [c] ride through turbulence, and [d] weight
Wing Loading
122
High W/S mean Stall Speed is
High
123
▪ For cruise at (L/D)max, a high wing loading is required
▪ For flight at high altitudes and at low speeds, a large wing is required.
▪ Of course a large wing means more weight
Wing Loading
124
Low W/S means Stall Speed is
Low
125
If Fieldlength ( Landing and Take-off) is Long, Wing Loading is
High
126
If Fieldlength ( Landing and Take-off) is Short, Wing Loading is
Low
127
L/D max is high when Wing Loading is
High
128
L/D max is low when Wing Loading is
Low
129
Good Ride qualities in turbulence when Wing loading is
High
130
If weight is low then Wing loading is
High
131
If weight is high then Wing loading is
low
132
The higher the AR, the higher the span,
the heavier
133
Also means high lift curve slope; good approach
attitude; bad ride through turbulence
High Aspect Ratio
134
means reduced induced drag;
increased (L/D)max
Aspect Ratio
135
If induced drag is low the AR is
High
136
If induced drag is High the AR is
Low
137
If lift-curve slope is high the AR is
High
138
If pitch attitude is (approach) is low then AR is
High
139
If pitch attitude is (approach) is high then AR is
Low
140
Good Ride qualities in turbulence when Aspect Ratio is
Low
141
Poor Ride qualities in turbulence when Aspect Ratio is
High
142
If Wing weight is High then the Aspect ratio is
High
143
If Wing weight is low then the Aspect ratio is
Low
144
if Wing Span is large the Aspect Ratio is
High
145
if Wing Span is small the Aspect Ratio is
Low
146
Wingtip has less area, there is less vortex induced downwash,
which means a lot less
induced drag.
147
Most important geometric consideration when selecting and airfoil
Thickness Ratio
148
Higher thickness ratio, higher
profile drag / wave drag
149
If Higher thickness ratio weight is
Low
150
Higher thickness ratio (up to 12-14%), means C/L max is
Higher
151
Higher thickness ratio, greater
fuel volume
152
tip airfoil has negative incidence relative to root airfoil.
Wash-out
153
opposite of wash-out
Wash-in
154
- delays tip stall
▪ May increase induced drag
▪ Less-loaded tip; less strength requirements; less
weight
Wash-out
155
will only be optimal relative to lift distribution for one value of coefficient of lift
Wing twist
156
Negative Twist
Wash out
157
Positive Twist
Wash in
158
one type of airfoil used, incidence is
changing relative to root chord.
Geometric Twist
159
Incidence is proportional to distance from root airfoil.
Linear Twist
160
difference in the zero-lift angles of the
root and tip airfoil. Same as geometric twist if one type of airfoil
is used
Aerodynamic Twist
161
It is possible for a wing without geometric twist to have an (blank) This can happen, for example, when the
root and the tip are using different airfoil.
Aerodynamic Twist
