Configuration Options: Connecting Concepts Why Airplanes

33 Pages·2003·6.47 MB·English

Configuration Options: Connecting Concepts
Why Airplanes Look Like They Do
To Requirements
W. H. Mason
Aerospace and
Ocean Engineerin g collage from John McMasters
slide 1
2/19/03
A new capability
Technology
someone might
advances?
pay to have?
Designer
How to exploit
technology for
capability?
Configuration
Concept
Airplane Shapes Change to
Exploit Advances in Technology
Aerospace and
Ocean Engineerin g
slide 2
2/19/03
To Start: Define a Mission
What is the airplane supposed to do?
• How far does it go? How fast?
• What and how much does it carry?
• What are the landing and takeoff requirements?
• Are there any maneuver/accel requirements?
(these are known as point performance req’ts)
• What MIL or FAR req’ts must be satisfied?
Taken together, the answers to these questions are
known as the Mission Statement, and also imply that
you think of concepts to do the job
Aerospace and
Ocean Engineerin g
slide 3
2/19/03
We Define Mission Segments
Each Segment Can Influence the Concept
BCA: best cruise altitude
BCA,
BCM: best cruise Mach
specified M
6+
7
5+
Altitude
combat
5
6
4
3 BCA,BCM
8 R R
7 subsonic supersonic
2
1
Radius
Aerospace and
Ocean Engineerin g
slide 4
2/19/03
Configuration Concept:
• Lifting surface arrangement
• Control surface(s) location
• Propulsion system selection
• Payload
• Landing Gear
Wright Brothers:
• Light weight propulsion
• Innovative control concept
(more important than stability)
• Continual design evolution/refinement
Aerospace and
Ocean Engineerin g
slide 5
2/19/03
Good Aircraft
• Aerodynamically efficient, including propulsion integration (streamlining!)
• Must balance near stability level for minimum drag
• Landing gear must be located relative to cg to allow rotation at TO
• Adequate control authority must be available throughout flight envelope
• Design to build easily (cheaply) and have low maintenance costs
• in 1990s: quiet, nonpolluting
Aerospace and
Ocean Engineerin g
slide 6
2/19/03
Conventional Subsonic - A Baseline
• Payload distributed around cg
• Longitudinal control power from tail (with moment arm)
• Vertical Tail for directional stability, rudder for control
• Wing/Fuselage/Landing Gear setup works
• Minimum trimmed drag at
near neutral stability
Aerospace and
Boeing 747-400, source: www.boeing.com
Ocean Engineerin g
slide 7
2/19/03
Configuration Options
• Where do you put
– the wings?
– the engines (in fact, what kind?)
• Where do you put the control surfaces?
– what options are available?
• Do you have room for the landing gear?
• Possible innovative designs?
Aerospace and
Ocean Engineerin g
slide 8
2/19/03
Why Sweep the Wing?
Subsonic (usually small)
• Adjust wing aero center relative to cg
• On flying wing, get moment arm length for control
Transonic (significant, 30°-35°)
• Delay drag rise Mach (compressibility effect)
- definition of the drag divergence Mach no.?
Supersonic (large, 45°-70°)
• Wing concept changes,
- must distribute load longitudinally as well as laterally
• reduce cross-sectional area and area variation
Wing sweep increases wing weight for fixed span
Aerospace and
Ocean Engineerin g
slide 9
2/19/03
The classic large airplane: The Boeing 747
source: www.boeing.com
Aerospace and
Ocean Engineerin g
slide 10
2/19/03