tmp190

06-08-2010, 11:12 AM

From a website I got this calculation procedure. What do you think ?

advance ratio (J), power coefficient (C_P):

J = 88.0 * v / (N * D),

where v is aircraft speed in mph, N is prop rotation in RPM, and D is prop diameter in feet

C_P = 52.5 * gamma* BHP / [(N / 1000)^3 * D^5 * rho / rho_0],

where gamma is fraction of full power being applied, BHP is engine brake horsepower, N is prop RPM, D is prop diameter in ft, rho is the air density, and rho_0 is the air density at standard sea level.

eta_i / (1 - eta_i)^(1/3) = (pi / 2)^(1/3) * J / C_P^(1/3),

eta is approx 0.85 to 0.87 eta_i.

advance ratio (J), power coefficient (C_P):

J = 88.0 * v / (N * D),

where v is aircraft speed in mph, N is prop rotation in RPM, and D is prop diameter in feet

C_P = 52.5 * gamma* BHP / [(N / 1000)^3 * D^5 * rho / rho_0],

where gamma is fraction of full power being applied, BHP is engine brake horsepower, N is prop RPM, D is prop diameter in ft, rho is the air density, and rho_0 is the air density at standard sea level.

eta_i / (1 - eta_i)^(1/3) = (pi / 2)^(1/3) * J / C_P^(1/3),

eta is approx 0.85 to 0.87 eta_i.