Wing Design Flashcards
(26 cards)
Give 5 advantages of using high wing
- Loading/unloading
- water landing
- more lift
- good engine location
- avoid high temperature gases (take-off / landing)
Give 4 disadvantages of using high wing
- More frontal area then mid-wing
- lower ground effect
- pilot reduced vision
- more drag
Give 5 advantages of using low wing
- Better ground effect
- lighter
- lower drag
- shorter landing gear
- higher lateral control
Give 2 disadvantages of using low wing
- less lift
2. needs more landing run
Give 2 advantages of using mid-wing
- features stand between high and low wing
2. cut wing for fuselage
Give 2 disadvantages of using mid-wing
- more expensive
2. more drag than low wing
Define aerodynamic centre
The point where moment is independent of angle of attack
Define centre of pressure
point where resultant pressure forces act on the body
How inaccurate can initial iteration be for calculating maximum takeoff weight
20%
Give equation for Wto
Wto = (Wc + Wp) / ( 1 - Wf/Wt - We/Wt)
Give equation for fuel fraction ratio
Wf/Wt = 1.05(1 - sum(Wi+1 / Wi))
1.05 : 5% extra fuel
Give equation for pitching moment
Cm = M/q(c^2)
c^2 = S probably
Give thickness ranges for various flight dynamics
15-18%:
low speed, high lift cargo
9-12%;
high speed, low lift high subsonic passenger aircraft
3-9%:
supersonic aircraft
Explain 6-series NACA aerofoil
example: 65(1) - 212
6: 6 series
5: minimum pressure at 50%c
(1) : low drag for a Cl range +/- 0.1
2: Cl desirable is 0.2
12: thickness
Explain 5-series NACA aerofoil
example: 23012
2: Control camber (L=2, Cl = L x 3/20)
3: position of max camber divided by 20
0: 0-normal camber line, 1-reflex camber line
12: thickness
Give advantages and disadvantages of a tapered wing
Ad:
- elliptical lift distribution
- reduces wing weight
- improves lateral control
Dis:
- increases production cost
What are raked wingtips
tip of the wing has a higher degree of sweep than the rest of the wing
- improves fuel efficiency, climb performance and shorten takeoff
- this is because it reduces induced drag
What does Dihedral wings achieve
- better lateral stability
- this is due to a greater lift force being produced on one wing when aircraft slips during manoeuvre
- increases drag however as lift is not perfectly normal to fuselage
Give thrust equation
T = m(dot)(Ve - Vi) + (Pe - Pi)Ae
m(dot) = mass flow rate = ρVA
Give propeller diameter equation
Dp = Kn x SQRT( 2 x np x P x AR / ρ x Vav^2 x Vc x Clp)
What is the use of frames and stringers in fuselage structure
Frames:
resist hoop stress
Stringers:
resist bending stress
Give equation for wing box
Wing box volume = Tr x Cr x intersection length
Cr = 3/2 x C x ( 1 + λ)/(1 + λ x λ^2)
C = mean chord length λ = taper ratio
Tr = (t/c),max x C
How to calculate gear box ratio
GR = np / ns
np = propeller rotational speed ns = engine shaft rotational speed
Define divergence
when deformation-dependent aerodynamic forces exceed the elastic restoring capability of the structure
