Item 1083

OTHER: Helicopter - Rotor Disk & HP Specifications - Database Calculations

Notes:

The calculations are done with FORMS: Helicopter, Momentum Method, Flight Hovering, Test Conditions, Atmosphere

The Total Disk Area [AT] is used in the momentum method.

The Effective Disk Area [A] is used in the blade element method.

FORM: Momentum Method:

I have increased Prouty's algorithm for [Change in Blade Pitch] (Δθ) by a multiplier of 10 to make the value look correct.

The Induced power in Forward flight will be incorrect since the Oswald efficiency factor is currently a constant and it must be a variable from Figure 3.7 on page 128 of RWP1.

Vertical and Forward computations and their results are independent of each other.

There are now problems with the calculations; May 16, 2002

    1. It appears that the Momentum Method is only compatible with the Blade Element; for 1 rotor w/ 2 blades and 0012 airfoil.
    2. The VR-7 (8-H-12) blade gives too much lift in comparison with the 0012.
    3. The Momentum and the Blade element methods are comparable for 1 rotor w/ 2 blades and 0012 airfoil, but that's where it ends, Side by side is OK in Momentum but it is way out in blade element

Considerations re a Method of Calculating Intermeshing, Interleaving & Side-by-Side, Hover HP, using the UniCopter as an example

    1. Calculate the overlapped area of the 2 disks.~ 181 ft2
    2. Calculate the non-overlapped area of the 2 disks. ~ 74 ft2
    3. Sum 1. and 2. to obtain total disk area. ~ 255 ft2
    4. Calculate the HP required for 1 rotor disk (w/ 4 or 6 blades) at the full GW, using the Blade Element Method. ~ 58 HP
    5. Calculate the HP required for 1 rotor disk (w/ 2 or 3 blades) at half the GW, using the Blade Element Method. ~ 25 HP
    6. Obtain the HP for overlapped area. Items (1 / 3) * 4 ~ (181 / 255) * 58 Hp = 41.17HP
    7. Obtain the HP for overlapped area. Items (2 / 3) * 5 ~ (74 / 255) * 25 HP = 7.25HP
    8. Sum the two HPs. Items 6 + 8 ~ 41.17HP + 7.25HP = 48.42 HP

Note re 8. If the masts are concentric then the HP is that of a 4-blade rotor and it does not take into account any of the co-axial gap advantage.

Note that the current Momentum calculation gives 45.15 HP and the current Blade Element gives 83.11 HP.

Back to top | SynchroLite Home Page | UniCopter Home Page

Last Revised: May 17, 2002