1 /***************************************************************************
5 ----------------------------------------------------------------------------
7 FUNCTION: aerodynamics model based on constant stability derivatives
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11 MODULE STATUS: developmental
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15 GENEALOGY: Based on data from:
16 Part 1 of Roskam's S&C text
17 The FAA type certificate data sheet for the 172
18 Various sources on the net
19 John D. Anderson's Intro to Flight text (NACA 2412 data)
20 UIUC's airfoil data web site
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24 DESIGNED BY: Tony Peden
28 MAINTAINED BY: Tony Peden
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35 6/10/99 Initial test release
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48 Croll,Cl rolling moment (yeah, I know. Shoot me.)
51 o constant i.e. not a function of alpha or beta
60 de elevator deflection
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71 ----------------------------------------------------------------------------
75 ----------------------------------------------------------------------------
79 ----------------------------------------------------------------------------
83 --------------------------------------------------------------------------*/
87 #include "ls_generic.h"
88 #include "ls_cockpit.h"
89 #include "ls_constants.h"
91 #include "c172_aero.h"
99 #define DYN_ON_SPEED 33 /*20 knots*/
103 #define NZ generic_.n_cg_body_v[2]
109 extern COCKPIT cockpit_;
112 SCALAR interp(SCALAR *y_table, SCALAR *x_table, int Ntable, SCALAR x)
119 /* if x is outside the table, return value at x[0] or x[Ntable-1]*/
123 /* printf("x smaller than x_table[0]: %g %g\n",x,x_table[0]); */
125 else if(x >= x_table[Ntable-1])
127 slope=(y_table[Ntable-1]-y_table[Ntable-2])/(x_table[Ntable-1]-x_table[Ntable-2]);
128 y=slope*(x-x_table[Ntable-1]) +y_table[Ntable-1];
130 /* printf("x larger than x_table[N]: %g %g %d\n",x,x_table[NCL-1],Ntable-1);
132 else /*x is within the table, interpolate linearly to find y value*/
135 while(x_table[i] <= x) {i++;}
136 slope=(y_table[i]-y_table[i-1])/(x_table[i]-x_table[i-1]);
137 /* printf("x: %g, i: %d, cl[i]: %g, cl[i-1]: %g, slope: %g\n",x,i,y_table[i],y_table[i-1],slope); */
138 y=slope*(x-x_table[i-1]) +y_table[i-1];
144 void aero( SCALAR dt, int Initialize ) {
148 static int flap_dir=0;
149 static SCALAR lastFlapHandle=0;
152 static SCALAR trim_inc = 0.0002;
154 static SCALAR alpha_ind[NCL]={-0.087,0,0.14,0.21,0.24,0.26,0.28,0.31,0.35};
155 static SCALAR CLtable[NCL]={-0.22,0.25,1.02,1.252,1.354,1.44,1.466,1.298,0.97};
157 static SCALAR flap_ind[Ndf]={0,10,20,30};
158 static SCALAR dCLf[Ndf]={0,0.20,0.30,0.35};
159 static SCALAR dCdf[Ndf]={0,0.0021,0.0085,0.0191};
160 static SCALAR dCmf[Ndf]={0,-0.0654,-0.0981,-0.114};
162 static SCALAR flap_transit_rate=2.5;
168 /* printf("Initialize= %d\n",Initialize); */
169 /* printf("Initializing aero model...Initialize= %d\n", Initialize);
171 /*nondimensionalization quantities*/
172 /*units here are ft and lbs */
173 cbar=4.9; /*mean aero chord ft*/
174 b=35.8; /*wing span ft */
175 Sw=174; /*wing planform surface area ft^2*/
176 rPiARe=0.054; /*reciprocal of Pi*AR*e*/
177 lbare=3.682; /*elevator moment arm / MAC*/
186 Cda=0.13; /*Not used*/
195 CLde=-Cmde / lbare; /* kinda backwards, huh? */
217 MaxTakeoffWeight=2550;
225 Cl > 0 => Right wing down
228 elevator > 0 => AND -- aircraft nose down
229 aileron > 0 => right wing up
233 /*do weight & balance here since there is no better place*/
238 else if(Weight < 1500)
244 else if(Dx_cg < -0.4655)
252 if(Flap_handle < flap_ind[0])
254 Flap_handle=flap_ind[0];
255 Flap_Position=flap_ind[0];
257 else if(Flap_handle > flap_ind[3])
259 Flap_handle=flap_ind[3];
260 Flap_Position=flap_ind[3];
266 if((Flap_handle != lastFlapHandle) && (dt > 0))
272 Flap_Position=Flap_handle;
274 lastFlapHandle=Flap_handle;
275 if((Flaps_In_Transit) && (dt > 0))
277 if(Flap_Position < 10)
278 flap_transit_rate = 2.5;
284 if(Flap_Position < Flap_handle)
289 if(fabs(Flap_Position - Flap_handle) > dt*flap_transit_rate)
290 Flap_Position+=flap_dir*flap_transit_rate*dt;
292 if(fabs(Flap_Position - Flap_handle) < dt*flap_transit_rate)
295 Flap_Position=Flap_handle;
301 if(Aft_trim) long_trim = long_trim - trim_inc;
302 if(Fwd_trim) long_trim = long_trim + trim_inc;
304 /* printf("Long_control: %7.4f, long_trim: %7.4f,DEG_TO_RAD: %7.4f, RAD_TO_DEG: %7.4f\n",Long_control,long_trim,DEG_TO_RAD,RAD_TO_DEG);
305 */ /*scale pct control to degrees deflection*/
306 if ((Long_control+Long_trim) <= 0)
307 elevator=(Long_control+Long_trim)*28*DEG_TO_RAD;
309 elevator=(Long_control+Long_trim)*23*DEG_TO_RAD;
311 aileron = -1*Lat_control*17.5*DEG_TO_RAD;
312 rudder = -1*Rudder_pedal*16*DEG_TO_RAD;
314 The aileron travel limits are 20 deg. TEU and 15 deg TED
315 but since we don't distinguish between left and right we'll
316 use the average here (17.5 deg)
320 /*calculate rate derivative nondimensionalization (is that a word?) factors */
321 /*hack to avoid divide by zero*/
322 /*the dynamic terms are negligible at low ground speeds anyway*/
324 /* printf("Vinf: %g, Span: %g\n",V_rel_wind,b);
326 if(V_rel_wind > DYN_ON_SPEED)
328 cbar_2V=cbar/(2*V_rel_wind);
329 b_2V=b/(2*V_rel_wind);
338 /*calcuate the qS nondimensionalization factors*/
340 qS=Dynamic_pressure*Sw;
345 /* printf("aero: Wb: %7.4f, Ub: %7.4f, Alpha: %7.4f, elev: %7.4f, ail: %7.4f, rud: %7.4f, long_trim: %7.4f\n",W_body,U_body,Alpha*RAD_TO_DEG,elevator*RAD_TO_DEG,aileron*RAD_TO_DEG,rudder*RAD_TO_DEG,long_trim*RAD_TO_DEG);
346 printf("aero: Theta: %7.4f, Gamma: %7.4f, Beta: %7.4f, Phi: %7.4f, Psi: %7.4f\n",Theta*RAD_TO_DEG,Gamma_vert_rad*RAD_TO_DEG,Beta*RAD_TO_DEG,Phi*RAD_TO_DEG,Psi*RAD_TO_DEG);
351 /* sum coefficients */
352 CLwbh = interp(CLtable,alpha_ind,NCL,Alpha);
353 /* printf("CLwbh: %g\n",CLwbh);
355 CLo = CLob + interp(dCLf,flap_ind,Ndf,Flap_Position);
356 Cdo = Cdob + interp(dCdf,flap_ind,Ndf,Flap_Position);
357 Cmo = Cmob + interp(dCmf,flap_ind,Ndf,Flap_Position);
359 /* printf("FP: %g\n",Flap_Position);
360 printf("CLo: %g\n",CLo);
361 printf("Cdo: %g\n",Cdo);
362 printf("Cmo: %g\n",Cmo); */
368 CL = CLo + CLwbh + (CLadot*Alpha_dot + CLq*Theta_dot)*cbar_2V + CLde*elevator;
369 cd = Cdo + rPiARe*Ai*Ai*CL*CL + Cdde*elevator;
370 cy = Cybeta*Beta + (Cyp*P_body + Cyr*R_body)*b_2V + Cyda*aileron + Cydr*rudder;
372 cm = Cmo + Cma*Alpha + (Cmq*Q_body + Cmadot*Alpha_dot)*cbar_2V + Cmde*(elevator);
373 cn = Cnbeta*Beta + (Cnp*P_body + Cnr*R_body)*b_2V + Cnda*aileron + Cndr*rudder;
374 croll=Clbeta*Beta + (Clp*P_body + Clr*R_body)*b_2V + Clda*aileron + Cldr*rudder;
376 /* printf("aero: CL: %7.4f, Cd: %7.4f, Cm: %7.4f, Cy: %7.4f, Cn: %7.4f, Cl: %7.4f\n",CL,cd,cm,cy,cn,croll);
379 /*calculate wind axes forces*/
384 /* printf("V_rel_wind: %7.4f, Fxwind: %7.4f Fywind: %7.4f Fzwind: %7.4f\n",V_rel_wind,F_X_wind,F_Y_wind,F_Z_wind);
387 /*calculate moments and body axis forces */
391 /* requires ugly wind-axes to body-axes transform */
392 F_X_aero = F_X_wind*Cos_alpha*Cos_beta - F_Y_wind*Cos_alpha*Sin_beta - F_Z_wind*Sin_alpha;
393 F_Y_aero = F_X_wind*Sin_beta + F_Y_wind*Cos_beta;
394 F_Z_aero = F_X_wind*Sin_alpha*Cos_beta - F_Y_wind*Sin_alpha*Sin_beta + F_Z_wind*Cos_alpha;
396 /*no axes transform here */
397 M_l_aero = croll*qSb;
398 M_m_aero = cm*qScbar;
401 /* printf("I_yy: %7.4f, qScbar: %7.4f, qbar: %7.4f, Sw: %7.4f, cbar: %7.4f, 0.5*rho*V^2: %7.4f\n",I_yy,qScbar,Dynamic_pressure,Sw,cbar,0.5*0.0023081*V_rel_wind*V_rel_wind);
403 printf("Fxaero: %7.4f Fyaero: %7.4f Fzaero: %7.4f Weight: %7.4f\n",F_X_aero,F_Y_aero,F_Z_aero,Weight);
405 printf("Maero: %7.4f Naero: %7.4f Raero: %7.4f\n",M_m_aero,M_n_aero,M_l_aero);