Velocity at 2R below rotor disk is 2 times that at rotor disk.

R of single disk is 104".

R squared is 10816 sq-in.

1/2R squared is 5408 sq-in.

Square root of 5408 is 73.5391".

Therefore the radius of the downwash 2R below the disk is 73.5391".

The radius of the downwash disk at the same elevation as that of the center of the stabilizer is approximately 86".

The rotor disk area is pi * R * R which is (22/7)*104*104 = 33,993 sq-in.

The disk area at the stabilizer elevation is pi * r * r which is (22/7)*86*86 = 23,244 sq-in.

The average loading at the rotor disk is 1.6251 lbs per sq-ft.

Therefore the average loading at the elevation of the stabilizer is 1.6251 * (33,993 / 23,244) = 2.376 lbs per sq-ft.

If the stabilizer X-axis coordinate is 75% of R then it is located at 78/86.4 = 90% of downwash disk radius at the elevation of the stabilizer.

The following coefficients are from the blade element program for hover.

Therefore the loading from the downwash on the stabilizers in hover should be 2.376 * (48 / 37) = 3 lbs per sq-ft.

As the forward speed increases the downwash from the disk onto the stabilizer should progressively decrease until the forward speed reaches about 25 knots. At this speed the downwash should be coming from the center of the rotor disks and therefore be quite small. Above 25 knots the downwash should start increasing again. It should also be noted that any longitudinal pitch in the body of the helicopter would also cause a pitch in the stabilizers and as the forward speed increases this pitch will contribute (or deduct) more and more to the downloading on the stabilizers.