Post on 06-May-2018
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
What is the optimum taper ratio?
λ ≈ ???
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
For ease of manufacture
λ ≈ 1.0?
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
For minimum wing weight
λ ≈ 0.2?
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
For benign stall characteristics
ηsep≈(1-λ)
ηsep ≈ 0.4
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
For benign stall characteristics
λ ≈ 0.6?
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
For minimum vortex drag
λ ≈ 0.4?
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Other factors?
•twist
•t/c
•sweep
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
So what is the optimum taper ratio?
λ ≈ ??
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
To deal with such issues we need:
• Judgement and intuition.
• Conceptual design tools.
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Commercial conceptual design
tools
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Homebrew spreadsheet models?
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Homebrew spreadsheet models?
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Why build your own?
• You have absolute control.
• You choose the methods.
• You can calibrate it to the problem.
• You learn about the design.
• They can be very accurate.
• They can be very powerful.
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Building your own models
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Input data
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Fuselage geometry
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Fuselage geometry – X section
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Fuselage geometry – X sections
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Fuselage Geometry
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Fuselage geometry -apertures
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Mission data
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Range-payload data
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Range-payload data
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Design variables
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Typical high-level design variables
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Sources of information
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Model components
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
• Weights & c.g.
• Propulsion.
• Lift.
• Drag.
• Take-off performance.
• Cruise performance.
Performance model components
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Performance model components
• Landing performance.
• Static stability & control.
• Dynamic stability.
• Production cost.
• Direct operating cost.
• Etc. etc.
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
• Weights and c.g.
• Propulsion.
• Lift.
• Drag.
• Take-off performance
• Cruise performance.
Performance model components
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Weight models
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
To be useful the methods used in the model should be:
• Appropriate.
• Design sensitive.
• Consistent.
• Calibrated.
• Verified.
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Weight models -Appropriate?
Ww = 219 kg
Ww = 928 kg
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Weight models - Appropriate?
Ww = 219 kg
Ww = 928 kg
Factor of 4!!!
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Weight models - Appropriate?
Ww = 219 kg
Ww = 928 kg
Factor of 4!!!
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Weight models - Design sensitive?
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Weight models – Consistent?
Should the autopilot servos have been included here?
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Weight models – Consistent?
... or here?
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Weight models – Calibrated?
Composite “fudge factors”
Wing structure 0.88
Empennage structure 0.86
Fuselage structure 0.92
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Weight models – Verified?
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
• Good geometric and performance data for DHC-6 available from AIAA case study.
• Complete weight breakdown by systems.
Weight models – Verified?
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Weight methods
• Public domain weight estimates.Wing - Denis Howe’s synthesis method.
Fuselage – Torenbeek, Appendix D
Rest - mostly from Torenbeek.
• No fiddle factors!
Weight models – Verified?
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Weight models – Verified?
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
An example
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Spreadsheet model of GROB Spn
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
• New generation turbofan.
• Composite.
• Reasonably good data available from brochures and RAeS presentation.
Spreadsheet model of GROB Spn
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Input data
• Fuselage sections.
• Wing planform.
• Max payload.
• Full fuel range, speed, altitude and payload.
Spreadsheet model of GROB Spn
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Grob Spn fuselage
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Grob Spn range-payload
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Range-payload data
Max payload = 2490 lbs
Max fuel payload = 1400 lbsMax fuel mission = 1700 nmFlown at 41kft and Mach 0.7
Single 200lb pilot. Reserves for 100 nm diversion
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Analysis methods
• All methods public domain.
• Weights methods same as Twin Otter, but adjusted by composite factors.
• Williams FJ44-3AP engine deck.
Spreadsheet model of GROB Spn
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Spreadsheet model of GROB Spn
Brochure Spreadsheet
MTOW 13,889 13,635
Flapped stall speed 75 KEAS 76 KEAS
AEO rate of climb @MTOW 4,360 fpm 4,406 fpm
OEI rate of climb @MTOW 1,360 fpm 1,504 fpm
Balanced field length 3,000 ft 2,954 ft
Landing distance 2,670 ft 2,509 ft
Fuel burn (max fuel mission + reserves) 685 US Gal. 681 US Gal.
Static margin ? 6%
Production cost $? m $5.5 m
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Model refinements
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
• Graphing.
• Macros & Visual Basic routines.
• Dynamic link libraries.
Model refinements
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Graphing
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Graphing examples
US Airfield access with engine option: A
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Graphing examples
US Airfield access with engine option: B
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Graphing examples
Scanned plot applied
as background image
Spin recovery analysis
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Graphing examples
Scanned plot applied
as background image
Spin recovery analysis
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Visual Basic routines
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Visual Basic routines
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Dynamic link libraries.
• Allow direct calls to external software.(e.g. Engine decks)
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Optimisation
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
• Optimisation using Excel’s intrinsic tools:
Goalseek
Solver
• 3rd party optimisation add-ins(genetic algorithms, simulated annealing, CONMIN etc.)
• True multi-disciplinary optimisation!
Optimisation
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft
Some demonstrations .....
A spreadsheet approach to aircraft design
Design Methods and Tools for Light Aircraft