Hello i want to solve the differential equation but i have these problem i don't understand why !?

restart;

with(LinearAlgebra):

with(student):

P:=180000:

Vt:=P/m;

m:=1.4787880*10^5-t*606.06:

g:=9.81:

T:=176:

pi:=evalf(Pi):

Euler_x := -(diff(lambda3(t), t)) = 0;

Euler_y := -(diff(lambda4(t), t)) = 0;

Euler_Vx := -lambda3(t)-(diff(lambda1(t), t)) = 0;

Euler_Vy := -lambda4(t)-(diff(lambda2(t), t)) = 0;

Euler_theta := lambda1(t)*sin(theta)-lambda2(t)*cos(theta) = 0;

transversalnost:=y(t)-lambda1(t)*Vt*cos(theta)-lambda2(t)*Vt*sin(theta)+lambda2(t)*g-lambda3(t)*Vx(t)-lambda4(t)*Vy(t)=0;

transversalnost:=eval(transversalnost,t=176);

sys:={Euler_x, Euler_Vx, Euler_y, Euler_Vy, theta=arctan(lambda2(t)/lambda1(t)), diff(Vx(t),t)=Vt*cos(theta), diff(Vy(t),t)=Vt*sin(theta)-g, diff(y(t),t)=Vy(t), diff(x(t),t)=Vx(t),x(0)=0, y(0)=0.302, lambda1(0)=0, lambda2(0)=0, lambda3(0)=0, lambda4(0)=0,transversalnost, x(176)=120};

ans:=dsolve(sys, numeric, output=listprocedure):

Error, (in dsolve/numeric/bvp/convertsys) unable to convert to an explicit first-order system

thanks for your help