diff --git a/sw/simulator/scilab/q6d/q6d_fdm.sci b/sw/simulator/scilab/q6d/q6d_fdm.sci
index 1478f571b1..be5812e158 100644
--- a/sw/simulator/scilab/q6d/q6d_fdm.sci
+++ b/sw/simulator/scilab/q6d/q6d_fdm.sci
@@ -138,7 +138,7 @@ function [F_ltp] = fdm_get_forces_ltp(X, U)
   quat = X(FDM_SQI:FDM_SQZ);
   airspeed_body = quat_vect_mult(quat, airspeed_ltp);
 
-  lift_body = [0; 0; -sum(U) * fdm_Ct0 * ( 1 + 1/fdm_V0 * airspeed_body(AXIS_Z))];
+  lift_body = [0; 0; -sum(U) * fdm_Ct0 * ( 1 - 1/fdm_V0 * airspeed_body(AXIS_Z))];
   lift_ltp = quat_vect_inv_mult(quat, lift_body);
   
   weight_ltp = [0; 0; fdm_g * fdm_mass];
diff --git a/sw/simulator/scilab/q6d/test_stop_stop.sce b/sw/simulator/scilab/q6d/test_stop_stop.sce
index f730b86425..e2666ba58a 100644
--- a/sw/simulator/scilab/q6d/test_stop_stop.sce
+++ b/sw/simulator/scilab/q6d/test_stop_stop.sce
@@ -17,8 +17,8 @@ max_accel = [ 9.81*tan(rad_of_deg(30)) 0.5*9.81];
 
 //b0 = [ 0    0   0];
 //b1 = [-10   1  -2];
-b0 = [ 0   0   0];
-b1 = [ 1   0   5];
+b0 = [ 0   0   0 ];
+b1 = [ 1   0   -5];
 [fo_traj] = sbb_gen_traj(time, dyn, max_speed, max_accel, b0, b1);