1 // flight.hxx -- define shared flight model parameters
3 // Written by Curtis Olson, started May 1997.
5 // Copyright (C) 1997 Curtis L. Olson - http://www.flightgear.org/~curt
7 // This program is free software; you can redistribute it and/or
8 // modify it under the terms of the GNU General Public License as
9 // published by the Free Software Foundation; either version 2 of the
10 // License, or (at your option) any later version.
12 // This program is distributed in the hope that it will be useful, but
13 // WITHOUT ANY WARRANTY; without even the implied warranty of
14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 // General Public License for more details.
17 // You should have received a copy of the GNU General Public License
18 // along with this program; if not, write to the Free Software
19 // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
29 # error This library requires C++
35 `FGInterface::get_Longitude ()'
36 `FGInterface::get_Latitude ()'
37 `FGInterface::get_Altitude ()'
38 `FGInterface::get_Phi ()'
39 `FGInterface::get_Theta ()'
40 `FGInterface::get_Psi ()'
41 `FGInterface::get_V_equiv_kts ()'
43 `FGInterface::get_V_north ()'
44 `FGInterface::get_V_east ()'
45 `FGInterface::get_V_down ()'
47 `FGInterface::get_P_Body ()'
48 `FGInterface::get_Q_Body ()'
49 `FGInterface::get_R_Body ()'
51 `FGInterface::get_Gamma_vert_rad ()'
52 `FGInterface::get_Climb_Rate ()'
53 `FGInterface::get_Alpha ()'
54 `FGInterface::get_Beta ()'
56 `FGInterface::get_Runway_altitude ()'
58 `FGInterface::get_Lon_geocentric ()'
59 `FGInterface::get_Lat_geocentric ()'
60 `FGInterface::get_Sea_level_radius ()'
61 `FGInterface::get_Earth_position_angle ()'
63 `FGInterface::get_Latitude_dot()'
64 `FGInterface::get_Longitude_dot()'
65 `FGInterface::get_Radius_dot()'
67 `FGInterface::get_Dx_cg ()'
68 `FGInterface::get_Dy_cg ()'
69 `FGInterface::get_Dz_cg ()'
71 `FGInterface::get_Radius_to_vehicle ()'
82 #include <simgear/compiler.h>
83 #include <simgear/constants.h>
84 #include <simgear/structure/subsystem_mgr.hxx>
85 #include <FDM/groundcache.hxx>
91 // This is based heavily on LaRCsim/ls_generic.h
92 class FGInterface : public SGSubsystem {
96 // Has the init() method been called. This is used to delay
97 // initialization until scenery can be loaded and we know the true
101 // Have we bound to the property system
104 // periodic update management variable. This is a scheme to run
105 // the fdm with a fixed delta-t. We control how many iteration of
106 // the fdm to run with the fixed dt based on the elapsed time from
107 // the last update. This allows us to maintain sync with the real
108 // time clock, even though each frame could take a random amount
109 // of time. Since "dt" is unlikely to divide evenly into the
110 // elapse time, we keep track of the remainder and add it into the
111 // next elapsed time. This yields a small amount of temporal
112 // jitter ( < dt ) but in practice seems to work well.
114 // CG position w.r.t. ref. point
115 SGVec3d d_cg_rp_body_v;
118 SGVec3d v_dot_local_v;
119 SGVec3d v_dot_body_v;
121 SGVec3d a_pilot_body_v;
123 SGVec3d omega_dot_body_v;
127 SGVec3d v_local_rel_ground_v; // V rel w.r.t. earth surface
128 SGVec3d v_local_airmass_v; // velocity of airmass (steady winds)
129 SGVec3d v_wind_body_v; // Wind-relative velocities in body axis
131 SGVec3d omega_body_v; // Angular B rates
132 SGVec3d euler_rates_v;
133 SGVec3d geocentric_rates_v; // Geocentric linear velocities
136 SGGeod geodetic_position_v;
137 SGVec3d cartesian_position_v;
138 SGGeoc geocentric_position_v;
139 SGVec3d euler_angles_v;
141 // Normal Load Factor
145 double v_rel_wind, v_true_kts;
146 double v_ground_speed, v_equiv_kts;
147 double v_calibrated_kts;
149 // Miscellaneious Quantities
150 double alpha, beta; // in radians
151 double gamma_vert_rad; // Flight path angles
152 double density, mach_number;
153 double static_pressure, total_pressure;
154 double dynamic_pressure;
155 double static_temperature, total_temperature;
156 double sea_level_radius, earth_position_angle;
157 double runway_altitude;
158 double climb_rate; // in feet per second
161 double daux[16]; // auxilliary doubles
162 float faux[16]; // auxilliary floats
163 int iaux[16]; // auxilliary ints
165 // the ground cache object itself.
166 FGGroundCache ground_cache;
170 int _calc_multiloop (double dt);
174 // deliberately not virtual so that
175 // FGInterface constructor will call
180 void _updatePositionM(const SGVec3d& cartPos);
181 void _updatePositionFt(const SGVec3d& cartPos) {
182 _updatePositionM(SG_FEET_TO_METER*cartPos);
184 void _updatePosition(const SGGeod& geod);
185 void _updatePosition(const SGGeoc& geoc);
187 void _updateGeodeticPosition( double lat, double lon, double alt );
188 void _updateGeocentricPosition( double lat_geoc, double lon, double alt );
189 void _update_ground_elev_at_pos( void );
191 inline void _set_CG_Position( double dx, double dy, double dz ) {
192 d_cg_rp_body_v[0] = dx;
193 d_cg_rp_body_v[1] = dy;
194 d_cg_rp_body_v[2] = dz;
196 inline void _set_Accels_Local( double north, double east, double down ) {
197 v_dot_local_v[0] = north;
198 v_dot_local_v[1] = east;
199 v_dot_local_v[2] = down;
201 inline void _set_Accels_Body( double u, double v, double w ) {
206 inline void _set_Accels_CG_Body( double x, double y, double z ) {
211 inline void _set_Accels_Pilot_Body( double x, double y, double z ) {
212 a_pilot_body_v[0] = x;
213 a_pilot_body_v[1] = y;
214 a_pilot_body_v[2] = z;
216 inline void _set_Accels_CG_Body_N( double x, double y, double z ) {
221 void _set_Nlf(double n) { nlf=n; }
222 inline void _set_Velocities_Local( double north, double east, double down ){
223 v_local_v[0] = north;
227 inline void _set_Velocities_Ground(double north, double east, double down) {
228 v_local_rel_ground_v[0] = north;
229 v_local_rel_ground_v[1] = east;
230 v_local_rel_ground_v[2] = down;
232 inline void _set_Velocities_Local_Airmass( double north, double east,
235 v_local_airmass_v[0] = north;
236 v_local_airmass_v[1] = east;
237 v_local_airmass_v[2] = down;
239 inline void _set_Velocities_Wind_Body( double u, double v, double w) {
240 v_wind_body_v[0] = u;
241 v_wind_body_v[1] = v;
242 v_wind_body_v[2] = w;
244 inline void _set_V_rel_wind(double vt) { v_rel_wind = vt; }
245 inline void _set_V_ground_speed( double v) { v_ground_speed = v; }
246 inline void _set_V_equiv_kts( double kts ) { v_equiv_kts = kts; }
247 inline void _set_V_calibrated_kts( double kts ) { v_calibrated_kts = kts; }
248 inline void _set_Omega_Body( double p, double q, double r ) {
253 inline void _set_Euler_Rates( double phi, double theta, double psi ) {
254 euler_rates_v[0] = phi;
255 euler_rates_v[1] = theta;
256 euler_rates_v[2] = psi;
258 inline void _set_Geocentric_Rates( double lat, double lon, double rad ) {
259 geocentric_rates_v[0] = lat;
260 geocentric_rates_v[1] = lon;
261 geocentric_rates_v[2] = rad;
263 inline void _set_Geocentric_Position( double lat, double lon, double rad ) {
264 geocentric_position_v.setLatitudeRad(lat);
265 geocentric_position_v.setLongitudeRad(lon);
266 geocentric_position_v.setRadiusFt(rad);
268 inline void _set_Latitude(double lat) {
269 geodetic_position_v.setLatitudeRad(lat);
271 inline void _set_Longitude(double lon) {
272 geodetic_position_v.setLongitudeRad(lon);
274 inline void _set_Altitude(double altitude) {
275 geodetic_position_v.setElevationFt(altitude);
277 inline void _set_Altitude_AGL(double agl) {
280 inline void _set_Geodetic_Position( double lat, double lon, double alt ) {
281 geodetic_position_v.setLatitudeRad(lat);
282 geodetic_position_v.setLongitudeRad(lon);
283 geodetic_position_v.setElevationFt(alt);
285 inline void _set_Euler_Angles( double phi, double theta, double psi ) {
286 euler_angles_v[0] = phi;
287 euler_angles_v[1] = theta;
288 euler_angles_v[2] = psi;
290 // FIXME, for compatibility with JSBSim
291 inline void _set_T_Local_to_Body( int i, int j, double value) { }
292 inline void _set_Alpha( double a ) { alpha = a; }
293 inline void _set_Beta( double b ) { beta = b; }
294 inline void _set_Gamma_vert_rad( double gv ) { gamma_vert_rad = gv; }
295 inline void _set_Density( double d ) { density = d; }
296 inline void _set_Mach_number( double m ) { mach_number = m; }
297 inline void _set_Static_pressure( double sp ) { static_pressure = sp; }
298 inline void _set_Static_temperature( double t ) { static_temperature = t; }
299 inline void _set_Total_temperature( double tat ) { total_temperature = tat; } //JW
300 inline void _set_Sea_level_radius( double r ) { sea_level_radius = r; }
301 inline void _set_Earth_position_angle(double a) { earth_position_angle = a; }
302 inline void _set_Runway_altitude( double alt ) { runway_altitude = alt; }
303 inline void _set_Climb_Rate(double rate) { climb_rate = rate; }
305 inline void _set_daux( int n, double value ) { daux[n] = value; }
306 inline void _set_faux( int n, float value ) { faux[n] = value; }
307 inline void _set_iaux( int n, int value ) { iaux[n] = value; }
312 FGInterface( double dt );
313 virtual ~FGInterface();
315 virtual void init ();
316 virtual void bind ();
317 virtual void unbind ();
318 virtual void update(double dt);
319 virtual bool ToggleDataLogging(bool state) { return false; }
320 virtual bool ToggleDataLogging(void) { return false; }
322 // Define the various supported flight models (many not yet implemented)
327 // The NASA LaRCsim (Navion) flight model
330 // Jon S. Berndt's new FDM written from the ground up in C++
333 // Christian's hot air balloon simulation
336 // Aeronautical DEvelopment AGEncy, Bangalore India
339 // The following aren't implemented but are here to spark
340 // thoughts and discussions, and maybe even action.
347 // Driven externally via a serial port, net, file, etc.
352 inline bool get_inited() const { return inited; }
353 inline void set_inited( bool value ) { inited = value; }
355 inline bool get_bound() const { return bound; }
357 //perform initializion that is common to all FDM's
361 virtual void set_Latitude(double lat); // geocentric
362 virtual void set_Longitude(double lon);
363 virtual void set_Altitude(double alt); // triggers re-calc of AGL altitude
364 virtual void set_AltitudeAGL(double altagl); // and vice-versa
365 virtual void set_Latitude_deg (double lat) {
366 set_Latitude(lat * SGD_DEGREES_TO_RADIANS);
368 virtual void set_Longitude_deg (double lon) {
369 set_Longitude(lon * SGD_DEGREES_TO_RADIANS);
372 // Speeds -- setting any of these will trigger a re-calc of the rest
373 virtual void set_V_calibrated_kts(double vc);
374 virtual void set_Mach_number(double mach);
375 virtual void set_Velocities_Local( double north, double east, double down );
376 inline void set_V_north (double north) {
377 set_Velocities_Local(north, v_local_v[1], v_local_v[2]);
379 inline void set_V_east (double east) {
380 set_Velocities_Local(v_local_v[0], east, v_local_v[2]);
382 inline void set_V_down (double down) {
383 set_Velocities_Local(v_local_v[0], v_local_v[1], down);
385 virtual void set_Velocities_Wind_Body( double u, double v, double w);
386 virtual void set_uBody (double uBody) {
387 set_Velocities_Wind_Body(uBody, v_wind_body_v[1], v_wind_body_v[2]);
389 virtual void set_vBody (double vBody) {
390 set_Velocities_Wind_Body(v_wind_body_v[0], vBody, v_wind_body_v[2]);
392 virtual void set_wBody (double wBody) {
393 set_Velocities_Wind_Body(v_wind_body_v[0], v_wind_body_v[1], wBody);
397 virtual void set_Euler_Angles( double phi, double theta, double psi );
398 virtual void set_Phi (double phi) {
399 set_Euler_Angles(phi, get_Theta(), get_Psi());
401 virtual void set_Theta (double theta) {
402 set_Euler_Angles(get_Phi(), theta, get_Psi());
404 virtual void set_Psi (double psi) {
405 set_Euler_Angles(get_Phi(), get_Theta(), psi);
407 virtual void set_Phi_deg (double phi) {
408 set_Phi(phi * SGD_DEGREES_TO_RADIANS);
410 virtual void set_Theta_deg (double theta) {
411 set_Theta(theta * SGD_DEGREES_TO_RADIANS);
413 virtual void set_Psi_deg (double psi) {
414 set_Psi(psi * SGD_DEGREES_TO_RADIANS);
418 virtual void set_Climb_Rate( double roc);
419 virtual void set_Gamma_vert_rad( double gamma);
423 virtual void set_Static_pressure(double p);
424 virtual void set_Static_temperature(double T);
425 virtual void set_Density(double rho);
427 virtual void set_Velocities_Local_Airmass (double wnorth,
431 // ========== Mass properties and geometry values ==========
433 // CG position w.r.t. ref. point
434 inline double get_Dx_cg() const { return d_cg_rp_body_v[0]; }
435 inline double get_Dy_cg() const { return d_cg_rp_body_v[1]; }
436 inline double get_Dz_cg() const { return d_cg_rp_body_v[2]; }
438 // ========== Accelerations ==========
440 inline double get_V_dot_north() const { return v_dot_local_v[0]; }
441 inline double get_V_dot_east() const { return v_dot_local_v[1]; }
442 inline double get_V_dot_down() const { return v_dot_local_v[2]; }
444 inline double get_U_dot_body() const { return v_dot_body_v[0]; }
445 inline double get_V_dot_body() const { return v_dot_body_v[1]; }
446 inline double get_W_dot_body() const { return v_dot_body_v[2]; }
448 inline double get_A_X_cg() const { return a_cg_body_v[0]; }
449 inline double get_A_Y_cg() const { return a_cg_body_v[1]; }
450 inline double get_A_Z_cg() const { return a_cg_body_v[2]; }
452 inline double get_A_X_pilot() const { return a_pilot_body_v[0]; }
453 inline double get_A_Y_pilot() const { return a_pilot_body_v[1]; }
454 inline double get_A_Z_pilot() const { return a_pilot_body_v[2]; }
456 inline double get_N_X_cg() const { return n_cg_body_v[0]; }
457 inline double get_N_Y_cg() const { return n_cg_body_v[1]; }
458 inline double get_N_Z_cg() const { return n_cg_body_v[2]; }
460 inline double get_Nlf(void) const { return nlf; }
462 // ========== Velocities ==========
464 inline double get_V_north() const { return v_local_v[0]; }
465 inline double get_V_east() const { return v_local_v[1]; }
466 inline double get_V_down() const { return v_local_v[2]; }
467 inline double get_uBody () const { return v_wind_body_v[0]; }
468 inline double get_vBody () const { return v_wind_body_v[1]; }
469 inline double get_wBody () const { return v_wind_body_v[2]; }
471 // Please dont comment these out. fdm=ada uses these (see
473 inline double get_V_north_rel_ground() const {
474 return v_local_rel_ground_v[0];
476 inline double get_V_east_rel_ground() const {
477 return v_local_rel_ground_v[1];
479 inline double get_V_down_rel_ground() const {
480 return v_local_rel_ground_v[2];
482 // <--- fdm=ada uses these (see cockpit.cxx)
484 inline double get_V_north_airmass() const { return v_local_airmass_v[0]; }
485 inline double get_V_east_airmass() const { return v_local_airmass_v[1]; }
486 inline double get_V_down_airmass() const { return v_local_airmass_v[2]; }
488 inline double get_U_body() const { return v_wind_body_v[0]; }
489 inline double get_V_body() const { return v_wind_body_v[1]; }
490 inline double get_W_body() const { return v_wind_body_v[2]; }
492 inline double get_V_rel_wind() const { return v_rel_wind; }
494 inline double get_V_true_kts() const { return v_true_kts; }
496 inline double get_V_ground_speed() const { return v_ground_speed; }
497 inline double get_V_ground_speed_kt() const { return v_ground_speed * SG_FEET_TO_METER * 3600 * SG_METER_TO_NM; }
499 inline double get_V_equiv_kts() const { return v_equiv_kts; }
501 inline double get_V_calibrated_kts() const { return v_calibrated_kts; }
503 inline double get_P_body() const { return omega_body_v[0]; }
504 inline double get_Q_body() const { return omega_body_v[1]; }
505 inline double get_R_body() const { return omega_body_v[2]; }
507 inline double get_Phi_dot() const { return euler_rates_v[0]; }
508 inline double get_Theta_dot() const { return euler_rates_v[1]; }
509 inline double get_Psi_dot() const { return euler_rates_v[2]; }
510 inline double get_Phi_dot_degps() const { return euler_rates_v[0] * SGD_RADIANS_TO_DEGREES; }
511 inline double get_Theta_dot_degps() const { return euler_rates_v[1] * SGD_RADIANS_TO_DEGREES; }
512 inline double get_Psi_dot_degps() const { return euler_rates_v[2] * SGD_RADIANS_TO_DEGREES; }
514 inline double get_Latitude_dot() const { return geocentric_rates_v[0]; }
515 inline double get_Longitude_dot() const { return geocentric_rates_v[1]; }
516 inline double get_Radius_dot() const { return geocentric_rates_v[2]; }
518 // ========== Positions ==========
520 inline double get_Lat_geocentric() const {
521 return geocentric_position_v.getLatitudeRad();
523 inline double get_Lon_geocentric() const {
524 return geocentric_position_v.getLongitudeRad();
526 inline double get_Radius_to_vehicle() const {
527 return geocentric_position_v.getRadiusFt();
530 const SGGeod& getPosition() const { return geodetic_position_v; }
531 const SGGeoc& getGeocPosition() const { return geocentric_position_v; }
532 const SGVec3d& getCartPosition() const { return cartesian_position_v; }
534 inline double get_Latitude() const {
535 return geodetic_position_v.getLatitudeRad();
537 inline double get_Longitude() const {
538 return geodetic_position_v.getLongitudeRad();
540 inline double get_Altitude() const {
541 return geodetic_position_v.getElevationFt();
543 inline double get_Altitude_AGL(void) const { return altitude_agl; }
545 inline double get_Latitude_deg () const {
546 return geodetic_position_v.getLatitudeDeg();
548 inline double get_Longitude_deg () const {
549 return geodetic_position_v.getLongitudeDeg();
552 inline double get_Phi() const { return euler_angles_v[0]; }
553 inline double get_Theta() const { return euler_angles_v[1]; }
554 inline double get_Psi() const { return euler_angles_v[2]; }
555 inline double get_Phi_deg () const { return get_Phi() * SGD_RADIANS_TO_DEGREES; }
556 inline double get_Theta_deg () const { return get_Theta() * SGD_RADIANS_TO_DEGREES; }
557 inline double get_Psi_deg () const { return get_Psi() * SGD_RADIANS_TO_DEGREES; }
560 // ========== Miscellaneous quantities ==========
562 inline double get_Alpha() const { return alpha; }
563 inline double get_Alpha_deg() const { return alpha * SGD_RADIANS_TO_DEGREES; }
564 inline double get_Beta() const { return beta; }
565 inline double get_Beta_deg() const { return beta * SGD_RADIANS_TO_DEGREES; }
566 inline double get_Gamma_vert_rad() const { return gamma_vert_rad; }
568 inline double get_Density() const { return density; }
569 inline double get_Mach_number() const { return mach_number; }
571 inline double get_Static_pressure() const { return static_pressure; }
572 inline double get_Total_pressure() const { return total_pressure; }
573 inline double get_Dynamic_pressure() const { return dynamic_pressure; }
575 inline double get_Static_temperature() const { return static_temperature; }
576 inline double get_Total_temperature() const { return total_temperature; }
578 inline double get_Sea_level_radius() const { return sea_level_radius; }
579 inline double get_Earth_position_angle() const {
580 return earth_position_angle;
583 inline double get_Runway_altitude() const { return runway_altitude; }
584 inline double get_Runway_altitude_m() const { return SG_FEET_TO_METER * runway_altitude; }
586 inline double get_Climb_Rate() const { return climb_rate; }
588 // Auxilliary variables
589 inline double get_daux( int n ) const { return daux[n]; }
590 inline float get_faux( int n ) const { return faux[n]; }
591 inline int get_iaux( int n ) const { return iaux[n]; }
593 // Note that currently this is the "same" value runway altitude...
594 inline double get_ground_elev_ft() const { return runway_altitude; }
597 //////////////////////////////////////////////////////////////////////////
598 // Ground handling routines
599 //////////////////////////////////////////////////////////////////////////
601 // Prepare the ground cache for the wgs84 position pt_*.
602 // That is take all vertices in the ball with radius rad around the
603 // position given by the pt_* and store them in a local scene graph.
604 bool prepare_ground_cache_m(double startSimTime, double endSimTime,
605 const double pt[3], double rad);
606 bool prepare_ground_cache_ft(double startSimTime, double endSimTime,
607 const double pt[3], double rad);
610 // Returns true if the cache is valid.
611 // Also the reference time, point and radius values where the cache
612 // is valid for are returned.
613 bool is_valid_m(double *ref_time, double pt[3], double *rad);
614 bool is_valid_ft(double *ref_time, double pt[3], double *rad);
616 // Return the nearest catapult to the given point
617 // pt in wgs84 coordinates.
618 double get_cat_m(double t, const double pt[3],
619 double end[2][3], double vel[2][3]);
620 double get_cat_ft(double t, const double pt[3],
621 double end[2][3], double vel[2][3]);
624 // Return the orientation and position matrix and the linear and angular
625 // velocity of that local coordinate systems origin for a given time and
626 // body id. The velocities are in the wgs84 frame at the bodys origin.
627 bool get_body_m(double t, simgear::BVHNode::Id id, double bodyToWorld[16],
628 double linearVel[3], double angularVel[3]);
631 // Return the altitude above ground below the wgs84 point pt
632 // Search for the nearest triangle to pt in downward direction.
633 // Return ground properties. The velocities are in the wgs84 frame at the
635 bool get_agl_m(double t, const double pt[3], double max_altoff,
636 double contact[3], double normal[3], double linearVel[3],
637 double angularVel[3], SGMaterial const*& material,
638 simgear::BVHNode::Id& id);
639 bool get_agl_ft(double t, const double pt[3], double max_altoff,
640 double contact[3], double normal[3], double linearVel[3],
641 double angularVel[3], SGMaterial const*& material,
642 simgear::BVHNode::Id& id);
643 double get_groundlevel_m(double lat, double lon, double alt);
644 double get_groundlevel_m(const SGGeod& geod);
647 // Return the nearest point in any direction to the point pt with a maximum
648 // distance maxDist. The velocities are in the wgs84 frame at the query
650 bool get_nearest_m(double t, const double pt[3], double maxDist,
651 double contact[3], double normal[3], double linearVel[3],
652 double angularVel[3], SGMaterial const*& material,
653 simgear::BVHNode::Id& id);
654 bool get_nearest_ft(double t, const double pt[3], double maxDist,
655 double contact[3], double normal[3],double linearVel[3],
656 double angularVel[3], SGMaterial const*& material,
657 simgear::BVHNode::Id& id);
660 // Return 1 if the hook intersects with a wire.
661 // That test is done by checking if the quad spanned by the points pt*
662 // intersects with the line representing the wire.
663 // If the wire is caught, the cache will trace this wires endpoints until
664 // the FDM calls release_wire().
665 bool caught_wire_m(double t, const double pt[4][3]);
666 bool caught_wire_ft(double t, const double pt[4][3]);
668 // Return the location and speed of the wire endpoints.
669 bool get_wire_ends_m(double t, double end[2][3], double vel[2][3]);
670 bool get_wire_ends_ft(double t, double end[2][3], double vel[2][3]);
672 // Tell the cache code that it does no longer need to care for
673 // the wire end position.
674 void release_wire(void);
677 extern FGInterface * cur_fdm_state;
679 // Toggle data logging on/off
680 void fgToggleFDMdataLogging(void);
683 #endif // _FLIGHT_HXX