"Perry J. Mick" wrote:
Interesting. I rotate at about the first taxiway exit (rwy 22 at MMV) at 80
knots (not 65 mph) which appears to be about a third of the length of the
runway including the extension on the 04 end, or about 2000 feet.
But I watch Cessna's takeoff, and they aren't rotating that much before the
spot that I rotate at. 1500 feet, like you say.
--
Perry Mick
Duckt N7XR
http://www.ductedfan.com
I found a minor bug that overestimated the reduction in thrust.
Results were a little pessimistic. Here is the corrected source code.
I figure with only 100 pounds of static thrust a RV will still get off
in about 1500 feet. I probably could change the program so the thrust built
up to 65 MPH and degraded there after.
Paul Lamar
The AirCraft Rotary Engine NewsLetter. Powered by Linux.
http://home.earthlink.net/~rotaryeng/ http://www.linux.org
AIRCRAFT SIMULATION V71
Copyright June 1997 Paul Lamar
paul-lamar-la@worldnet.att.net
Gross weight 1500
Equivalent square feet with gear down. 4
Equivalent flat plate in square feet with gear up. 3
Initial static thrust in pounds. 200
Pounds per mph that thrust is reduced. 1.00
Wing span 25
Wing Area 100
Time Net Accel Velocity Distance Cl HP Out Excess Climb
Sec Thrust FPS^2 MPH Feet Req. Total HP Avail. Pot. FPM
1.56 200 4.26 5 5 286.69 2 2 0
3.28 199 4.24 10 23 64.25 5 5 0
5.02 198 4.22 15 54 27.45 8 8 0
6.76 196 4.18 20 97 15.20 10 10 0
8.53 194 4.13 25 154 9.62 13 13 0
10.32 191 4.07 30 225 6.63 16 15 0
12.13 187 4.00 35 310 4.85 18 17 0
13.99 183 3.91 40 411 3.70 21 19 0
15.88 179 3.82 45 528 2.92 24 21 0
17.83 174 3.71 50 662 2.36 26 23 0
19.84 169 3.60 55 816 1.94 29 25 0
21.91 163 3.47 60 989 1.63 32 26 0
24.07 156 3.33 65 1185 1.39 34 27 0
AIRCRAFT SIMULATION V71
Copyright June 1997 Paul Lamar
paul-lamar-la@worldnet.att.net
Gross weight 1500
Equivalent square feet with gear down. 4
Equivalent flat plate in square feet with gear up. 3
Initial static thrust in pounds. 500
Pounds per mph that thrust is reduced. 1.00
Wing span 25
Wing Area 100
Time Net Accel Velocity Distance Cl HP Out Excess Climb
Sec Thrust FPS^2 MPH Feet Req. Total HP Avail. Pot. FPM
0.63 500 10.66 5 2 292.18 6 6 0
1.32 499 10.64 10 9 64.50 13 13 0
2.01 498 10.62 15 21 27.59 19 19 0
2.70 496 10.58 20 39 15.25 26 26 0
3.40 494 10.53 25 61 9.62 33 32 0
4.10 491 10.47 30 89 6.63 39 39 0
4.80 487 10.40 35 122 4.85 46 45 0
5.51 483 10.31 40 161 3.70 53 51 0
6.22 479 10.22 45 205 2.92 59 57 0
6.94 474 10.11 50 254 2.36 66 63 0
7.67 469 10.00 55 310 1.94 73 68 0
8.41 463 9.87 60 372 1.63 79 73 0
9.16 456 9.73 65 440 1.39 86 78 0
'
' 6/29/97 Version 71
'
'Requires QuickBasic and DOS "MORE".
'Generates ACCEL.DAT ascii file on hard disk in the directory from which
'this program is run.
'All sea level so far.
'
'In general ducted fans are twenty percent less efficient than propellors.
'The same program will work for propellors.
'
DEFDBL A-Z
OPEN "ACCEL51.DAT" FOR OUTPUT AS #1
CLS
FOR x = 1 TO 5: PRINT : NEXT
PRINT #1,
PRINT " AIRCRAFT SIMULATION V71"
PRINT #1, " AIRCRAFT SIMULATION V71"
PRINT " Copyright June 1997 Paul Lamar"
PRINT #1, " Copyright June 1997 Paul Lamar"
PRINT " paul-lamar-la@worldnet.att.net"
PRINT #1, " paul-lamar-la@worldnet.att.net"
PRINT ""
PRINT #1, ""
'
PRINT " Generates a file called ACCEL.DAT on this sub-directory."
FOR x = 1 TO 5: PRINT : NEXT
INPUT "Press Enter to continue"; z$
CLS
FOR x = 1 TO 5: PRINT : NEXT
INPUT " Gross Weight "; Wt
INPUT " Flate plate area with gear down "; FlatPlate
INPUT " Flate plate area with gear up "; GearUpFP
INPUT " Static Thrust "; StaticThrust
INPUT " Lapse Rate for thrust "; LapseRate
INPUT " Wing span "; Span
INPUT " Wing area "; WingArea
PRINT
'PRINT #1,
PRINT
'PRINT #1,
'Edit these numbers for your aircraft and propulsion system.
IF Wt = 0 THEN Wt = 1500
'Gross weight.
PRINT " Gross weight "; Wt
PRINT #1, " Gross weight "; Wt
IF FlatePlate = 0 THEN FlatPlate = 4
'Equivalent square feet with gear down.
PRINT " Equivalent square feet with gear down. "; FlatPlate
PRINT #1, " Equivalent square feet with gear down. "; FlatPlate
IF GearUpFP = 0 THEN GearUpFP = 2
'Equivalent flat plate in square feet with gear up.
PRINT " Equivalent flat plate in square feet with gear up. "; GearUpFP
PRINT #1, " Equivalent flat plate in square feet with gear up. "; GearUpFP
IF StaticThrust = 0 THEN StaticThrust = 500
'Initial static thrust in pounds.
PRINT " Initial static thrust in pounds. "; StaticThrust
PRINT #1, " Initial static thrust in pounds. "; StaticThrust
IF LapseRate = 0 THEN LapseRate = 1
'Pounds per mph that thrust is reduced.
PRINT " Pounds per mph that thrust is reduced. "; USING "#.##"; LapseRate
PRINT #1, " Pounds per mph that thrust is reduced. "; USING "#.##"; LapseRate
IF Span = 0 THEN Span = 24
PRINT " Wing span "; Span
PRINT #1, " Wing span "; Span
IF WingArea = 0 THEN WingArea = 150
PRINT " Wing Area "; WingArea
PRINT #1, " Wing Area "; WingArea
FOR x = 1 TO 5: PRINT : NEXT
PRINT #1,
PRINT #1,
INPUT "Press Enter to continue"; z$
'Don't change any of this.
pi = 3.1416
DeltaTime = .01 'Time increment in seconds. Smaller is better.
Velocity = .01 'Initial velocity in FPS. Do not change.
LiftOffCoef = 1.2 'Cl at which rotation is initiated
ClimbCoef = 1.19 'Cl at which climb can be initiated.
Flag = 1 'Used by program. Do not change
Thrust = StaticThrust 'Initialise thrust to static thrust.
AverageCord = WingArea / Span
Aspect = Span / AverageCord 'Aspect ratio
CLS
PRINT #1, "Time Net Accel Velocity Distance Cl HP Out Excess Climb "
PRINT #1, "Sec Thrust FPS^2 MPH Feet Req. Total HP Avail. Pot. FPM"
'Cl Req. is the lift coefficient required to = the weight of the aircraft.
'HP Out Total is the actual HP out of the tail pipe in terms of Lb Ft/Sec.
'HP Ex. Avail. is the excess HP available for climbing.
'Climb Pot. FPM is the rate of climb available at that speed and time.
FOR Time1 = DeltaTime TO 2000 STEP DeltaTime 'seconds
MPH = Velocity * .682
IF MPH > 75 THEN FlatPlate = GearUpFP 'Gear up point.
IF MPH \ 5 = Flag THEN GOSUB TimetoPrint 'Print the output
DynPress = (MPH ^ 2 * .0026) 'Standard day.
Cl = Wt / (DynPress * WingArea) 'Cl required to = weight.
IF Cl > 999 THEN Cl = 999 ELSE Cl = Cl 'Cosmetic fix only.
IF Cl < LiftOffCoef THEN GOSUB CalcDrag 'After rotate calc induced drag.
IF Cl < ClimbCoef THEN GOSUB CalcClimb 'Calc climb potential.
Thrust = StaticThrust - (MPH * LapseRate * DeltaTime)
NetThrust = Thrust - (DynPress * FlatPlate) - InducedDrag
Accel = (NetThrust / Wt) * 32 'In FPS^2
IF Accel < .005 THEN GOTO EndIt 'Top speed so exit the loop.
Velocity = Velocity + Accel * DeltaTime
Distance = Distance + (Velocity * DeltaTime)
HP = (Velocity * NetThrust) / 550 'Net HP after drag avail for climb.
THP = Thrust * Velocity / 550 'Thrust HP out the tail pipe.
NEXT Time1
EndIt:
PRINT #1,
CLOSE
CLS
SHELL "MORE < ACCEL51.DAT" 'Look at the data file on the disk.
FOR x = 1 TO 10: PRINT : NEXT
PRINT " Have a nice day!"
PRINT
PRINT " paul-lamar-la@worldnet.att.net"
SYSTEM
CalcDrag: 'Calculate the induced drag component.
InducedDrag = (((Cl ^ 2 / (pi * Aspect)) * WingArea) * DynPress)
RETURN
CalcClimb: 'Calculate the climb potential.
FootLbMin = HP * 33000
Climb = FootLbMin / Wt
RETURN
TimetoPrint:
PRINT Flag;
'READ Thrust 'Not used unless empirical data is avail.
Flag = Flag + 1
PRINT #1, USING "###.##"; Time1;
PRINT #1, USING " ###"; NetThrust;
PRINT #1, USING " ##.##"; Accel;
PRINT #1, USING " ###"; MPH;
PRINT #1, USING " ######"; Distance;
PRINT #1, USING " #####.##"; Cl;
PRINT #1, USING " #####"; THP;
PRINT #1, USING " #####"; HP;
PRINT #1, USING " ####"; Climb
RETURN
'Not used when lapse rate is available.
' Edit this for characteristics of the propulsion system.
' Fixed pitch, variable pitch, twist, ducted fan, etc..
' Thrust data in pounds at 5 MPH increments.
'MPH 5 10 15 20 25 30 35 40 45 50
DATA 100, 101, 102, 103, 104, 105, 106, 107, 108, 109
'MPH 55 60 65 70 75 80 85 90 95 100
DATA 110, 115, 120, 125, 130, 135, 140, 145, 150, 155
'MPH 105 110 115 120 125 130 135 140 145 150
DATA 160, 165, 170, 175, 180, 190, 195, 200, 205, 210
'MPH 155 160 165 170 175 180 185 190 195 200
DATA 215, 220, 220, 220, 220, 220, 220, 220, 220, 220
'MPH 205 210 215 220 225 230 235 240 245 250
DATA 220, 220, 220, 220, 220, 220, 220, 220, 220, 220
'MPH 255 260 265 270 275 280 285 290 295 300
DATA 220, 220, 220, 220, 220, 200, 100, 50, 25, 0