Simplified Aircraft Design Spreadsheet for HomebuildersVersion 1.0 Copyright C 2003 by Daniel P. Raymer. All Rights Reserved. See legal notice for further restrictions.
LEGAL NOTICE ! Better to save this spreadsheet as a renamed copy before changing it for your airplane, in case it gets messed up!
Inputs Calculated ValuesStall speed (kts) 60 Stall speed (ft/sec) 101.3Takeoff air density (slugs/ft^3) 0.00238 Dynamic pressure (psf) 12.2Wing CLmax 1.6 Wing loading (W/S) (psf) 19.55
power loading (lb/hp) 8.3333
Engine Power (hp -each) 120 Wo (lb) 2000.0Number of Engines 2 Wing Area (sq ft) 102.3
Swet/Sref 4.2Cfe 0.0053 Cdo 0.0223Aspect ratio (A) 10 K (=1/piAe) 0.0424Cruise air density (slugs/ft^3) 0.00176 W/S cruise 19.2Cruise velocity (kts) 180 Cruise velocity (ft/sec) 304.0
Dynamic pressure (psf) 81.3L/D cruise 9.57
Engine SFC 0.45 Engine SFC 0.000125Prop Efficiency (cruise) 0.75Range (nmi) 800 Range (ft) 4860800
Breguet Exponent 0.1539Wf/Wo 0.1641
Fuel allowance (%) 6 Wf/Wo with allow. 0.1739Empty Weight constant "a" 1.2438Weight - crew (lbs) 180Weight - Passengers (lbs) 180Weight - payload (lbs) 20 See Sizing Graph sheet for Wo Results
Wing taper ratio 0.5 Wing Span (ft) 31.98Root Chord (ft) 4.26Tip Chord (ft) 2.13Mean Chord (ft) 3.32
Horizontal tail arm (ft) 10 Tail areas:Cht (volume coeff) 0.6 Sht (horizontal) (sq ft) 20.35Vertical tail arm (ft) 10Cvt (volume coeff) 0.04 Svt (vertical) (sq ft) 13.08
Shar
e -
war
e !
Win
g Lo
adin
gW
o -k
now
n en
gine
If sizing to a range requirement, ignore this input for now but enter it later when Wo is calculated and engine is selected
You cannot enter Wo! Engine power and power loading are multiplied to calculate Wo. If sizing to a range requirement, do calculation below, read Wo from graph, and select an engine that gives the desired Wo=P*P/W
Wo
Sizi
ng to
a ra
nge
requ
irem
ent (
engi
ne is
no
t yet
sel
ecte
d)
(lb/hour /bhp)
(lb/sec /bhp)
Win
g G
eom
etry
Tail
Sizi
ng
Simplified Aircraft Design Spreadsheet for HomebuildersVersion 1.0 Copyright C 2003 by Daniel P. Raymer. All Rights Reserved. See legal notice for further restrictions.
Better to save this spreadsheet as a renamed copy before changing it for your airplane, in case it gets messed up! Send problems & questions to [email protected]
Other Factors Used Equations (from book) Misc Useful Calcs
e (Oswald) 0.75Wcruise/Wo 0.98
CL-cruise 0.2356
Non-cruise weight allowance 0.975
Empty Weight exponent -0.09 Fuel Weight 347.8 (lbs)Fuel Vol 58.0 (gal)
Enter items in blue and purple. Come back and re-enter purple items after the drawing is analyzed.
(OK to change these if you know what you are doing)
Preliminary tail sizing using these methods does not guarantee that the aircraft will be stable, controllable, or safe. You must perform stability calculations after doing your design layout!
LD
=1
qCD 0
W /S+(W /S ) K
q
q= 12ρV
Stall2
WS
=qC L
CD0=C feSwet
Sref
K=1
0 .75 π A=0 .424A
W f /W 0=1−0 .975 e
−R c bhp500 ηp L /D
W 0=W people+W payload
1−W E /W 0−W F /W 0
W E /W 0=aW0−0 .09
Send problems & questions to [email protected]
Sizing Calculations
Wo guess We/Wo We Wo calculated1000 0.6680 668.0 2403.21500 0.6440 966.0 2087.32000 0.6276 1255.1 1914.22500 0.6151 1537.7 1801.0
Enter Wo from graph (lbs) 2000Pick engine with horsepower of at least: 120
Power of Selected Engine: 120Calculated Power Loading: 8.33
Pick Wo from graph, where the two lines cross. Enter this value below to find the minimum horsepower engine for your power loading.
If sizing graph lines do not cross, change Wo-guess values above.
Now find a suitable engine of at least this horsepower and enter its power below:
Now go to sheet 1 and enter the power of your selected engine and the power loading calculated above in the
boxes this color. 800 1000 1200 1400 1600 1800 2000 2200 2400 26000
500
1000
1500
2000
2500
3000Sizing Graph
Wo Guess
Wo
Cal
cula
ted
800 1000 1200 1400 1600 1800 2000 2200 2400 26000
500
1000
1500
2000
2500
3000Sizing Graph
Wo Guess
Wo
Cal
cula
ted
As-Drawn Performance Calculations for Simplified Aircraft Design for HomebuildersUse this sheet for performance calculations after you have drawn your design and measured its geometry.
Calculated ValuesWo (lb) 2000 wing loading (W/S) (psf) 19.55Engine Power (hp) 120 stall speed (ft/sec) 101.34Number of Engines 2 stall speed (kts) 60.00Engine SFC (lb/hour /bhp) 0.45 power loading (lb/hp) 8.33Wing Area (sq ft) 102.3 Takeoff Parameter 123.2Cdo 0.0223 Takeoff Groundroll (ft) 874.2K (=1/piAe) 0.0424 Takeoff to 50 ft (ft) 1159.1Wing CLmax 1.6Takeoff air density (slugs/ft^3) 0.00238e (Oswald) 0.75Wcruise/Wo 0.98 Cruise Weight (lb) 1959.9922Non-cruise weight allowance 0.975Fuel allowance (%) 6Weight - crew (lbs) 180Weight - passengers (lbs) 180Weight - payload (lbs) 20Empty Weight (lbs) 1255.1
Other InputsPropeller Diameter (ft) 5Engine RPM (rev/min) 2700Cooling Power Loss (%) 6Cruise Power Setting (% of SL hp) 62Cruise air density (slug/ft^3) 0.00176 Power Coefficient Cp 0.1317
Go to next sheet for climb, cruise, and maximum speed calculations then return here
Cruise speed (kts) 180 Cruise speed (ft/sec) 304.02Cruise Advance Ratio J 1.3512
Cruise Prop efficiency 0.85 Cruise q (psf) 81.3Cruise W/S (psf) 19.2Cruise L/D 9.6Wfuel (total) (lbs) 365Wfuel (usable) (lbs) 344Wfuel (cruise) (lbs) 294log term 1.1776909Range (ft) 5854552Range (nmi) 964
Values from Sheet 1 - OK to change these here, but then link from Sheet 1 is lost
As-Drawn Performance Calculations for Simplified Aircraft Design for HomebuildersUse this sheet for performance calculations after you have drawn your design and measured its geometry.
Equations (from book)
T .O .P .=1.21
WS
Whp
C Lmax
LD
=1
qCD 0
W /S+(W /S ) K
q
R=550 ηp
Cbhp
LDln [ 0 .975W 0
W 0−W f (usable ) ]
Climb, Cruise, & Max Speed Calculations for Simplified Aircraft Design for HomebuildersUse this sheet for performance calculations after you have drawn your design and measured its geometry.
V kts V ft/sec CL CD Drag lbs50 84.45 0.375333 0.59 866.8703 537.4596 6.2759862 3.115636 0.434233 278.7433
100 168.9 0.750667 0.8 587.7087 364.3794 25.1039448 0.778909 0.048008 123.2702150 253.35 1.126 0.85 416.2937 258.1021 56.4838758 0.346182 0.027346 157.9862200 337.8 1.501333 0.82 301.2007 186.7444 100.415779 0.194727 0.023869 245.1549220 371.58 1.651467 0.8 267.1403 165.627 121.503093 0.160932 0.023359 290.2979
Input adjusted values
Advance Ratio J
Propeller Efficiency
Total Thrust lbs
Cruise Thrust lbs
Dynamic pressure q
Read Cruise speed where cruise thrust line crosses drag line and enter in cruise speed box (this color) on previous sheet
40 60 80 100 120 140 160 180 200 220 2400
200
400
600
800
1000Maximum & Cruise Speed
Total ThrustCruise ThrustDrag
Velocity - kts
Thru
st o
r Dra
g -lb
s
40 60 80 100 120 140 160 180 200 220 2400
500
1000
1500
2000
2500
3000Rate of Climb - Sea Level
Velocity - kts
Clim
b - f
pm
Climb, Cruise, & Max Speed Calculations for Simplified Aircraft Design for HomebuildersUse this sheet for performance calculations after you have drawn your design and measured its geometry.
Equations (from book)
Climb (fps)1520.43452401.34642003.3404579.56153-263.4165
Read Cruise speed where cruise thrust line crosses drag line and enter in cruise speed box (this color) on previous
D=qS(CD 0+KC L2)
CL−cruise=
WS
qq=12ρV 2
Vv=V [ TW −1
L/D ]
40 60 80 100 120 140 160 180 200 220 2400
500
1000
1500
2000
2500
3000Rate of Climb - Sea Level
Velocity - kts
Clim
b - f
pm
Weight Reporting Format for Simplified Aircraft Design for HomebuildersUse this sheet for reporting weights calculations & estimating center of gravity. Input only items in blue
Weight Loc Moment Weight Loc Momentlbs ft ft-lbs lbs ft ft-lbs
STRUCTURES 661.0 5600 EQUIPMENT 69.0 429 Wing 276 6.5 1794 Flight Controls 10 5.5 55 Horizontal Tail 24 21.0 504 Instruments 10 5.5 55 Vertical Tail 18 19.0 342 Hydraulics 2 6.0 12 Ventral Tail 8 17.0 136 Electrical 12 6.0 72 Fuselage 155 9.0 1395 Avionics 15 5.0 75 Canopy 15 8.0 120 Air Conditioning 0 Nacelle on wing 50 9.0 450 Anti-Icing 0 Nacelle/cowling 30 7.5 225 Furnishings & Equipment 20 8.0 160 Motor Mount 10 7.5 75 Main Landing Gear 56 9.0 504 (% We Allowance) 10 enter % Nose Landing Gear 19 2.9 55 Empty Weight Allowance 114.1 7.8 891 don’t enter these
PROPULSION 411.0 2877 TOTAL WEIGHT EMPTY 1255.1 7.8 9797 Engine 340 7.0 2380 Air Induction 3 7.0 21 USEFUL LOAD 744.9 Cooling 3 7.0 21 Crew 180.0 8.0 1440 Exhaust 8 7.0 56 Fuel 358.9 7.5 2692 Don't enter this! It is calculated from Wo, We, and other Useful Load Group items Engine Controls 2 7.0 14 Oil 6 5.0 30 Misc. Engine Inst 5 7.0 35 Passengers 180 8.0 1440 Propeller 30 7.0 210 Payload 20 10.0 200 Starter 10 7.0 70 Fuel System 10 7.0 70 TAKEOFF GROSS WEIGHT 2000.0 7.8 15598
Crew+Pass+Pld, No Fuel 1641.1 7.9 12907Crew+Pass,No Pld,No Fuel 1621.1 7.8 12707Crew only, No Fuel 1441.1 7.8 11267Crew only, Full Fuel 1800.0 7.8 13958
(Sorry, no weights estimation methods here, just the form to enter your estimates. Moments & cg are calculated)
Calculated Empty Weight constant "a". Go to Initial Sizing Inputs sheet and revise value in purple box:
Pos
sibl
e Lo
adin
g C
ondi
tions
Input only items in blue
1.2438
Don't enter this! It is calculated from Wo, We, and other Useful Load Group items
Calculated Empty Weight constant "a". Go to Initial Sizing Inputs sheet and revise value in purple box:
ASPECT RATIO OPTIMIZATION: DR-4
A-baseline 10Wo 2000.0Wwing-base 276We-base 1255.1 Read performance results and enter here
A A/Abase Delta We We-new Range ROC6 0.60 0.74 -73 1182 1165 212 175 2200
10 1.00 1.00 0 1255 964 220 180 240014 1.40 1.22 62 1317 760 221 181 2500
Wwing/ Ww-base
Max Speed
Cruise Speed
Enter delta on Weight sheet (I stuck it in the unused Anti-Ice entry), and change aspect ratio and empty weight "a" factor on Initial Sizing Sheet
6 8 10 12 140
500
1000
1500
2000
2500Aspect Ratio Trade Study
RangeMax Speed *10Cruise Speed *10Rate of Climb
Aspect Ratio
nmi,
kts,
or f
pm
max*10 cruise*102120 17502200 18002210 1810
6 8 10 12 140
500
1000
1500
2000
2500Aspect Ratio Trade Study
RangeMax Speed *10Cruise Speed *10Rate of Climb
Aspect Ratio
nmi,
kts,
or f
pm