Едно полезен калкулатор с обяснения и формули!
A i r c r a f t S u p e r C a l c u l a t o r 7.5.1
© 2005 - 2018 Dean A. Scott, all rights reserved.
MAC And Neutral Point
use the same units of measure for all entries!
Wing Sweep, C =
(S * ((2 * B) + A)) / (3 * (A + B))
MAC (length) =
A - (2 * (A - B) * (0.5 * A + B) / (3 * (A + B)))
MAC location, d =
Y * ((A - MAC) / (A - B))
wing area, WA =
2 * Y * ((A + B) / 2)
tail area, TA =
2 * YY * ((AA + BB) / 2)
wing aspect ratio, ARw =
(2 * Y) / ((A + B) / 2)
tail aspect ratio, ARt =
(2 * YY) / ((AA + BB) / 2)
Tail Arm =
(D - wing AC) + tail AC
tail volume, Vbar =
(TA / WA ) * (Tarm / MAC)
NP (%MAC) =
0.25 + (.7 * Vbar * (As / Aw) * ( 1 - de / da));
ideal CG (%MAC) =
NP - Desired Static Margin
actual CG (%MAC) =
((Total Moment / Total Wt) - (Datum to LE + C)) / MAC
actual static margin % =
(NP - actual CG) / MAC * 100
Center of Gravity (CG)
is the point where the weight of the aircraft is balanced.
Neutral Point (NP)
is the point where the aerodynamic forces of the wing and tail are balanced.
25% - 35% MAC is the typical range for the CG of a conventional aircraft .
Placing CG 5% to 15% of MAC in front of NP creates a longitudinal (pitch) stability called Static Margin. A lower margin (tail heavy) produces less stability and greater elevator authority, while a higher margin (nose heavy) creates more stability and less elevator authority. A static margin that's too high may result in elevator stall at take off and landing.
is a unitless volume coefficient, based on the ratio of the wing surface area to the horizontal tail group (stabilizer and elevator) surface area and the distance between the wing's AC and the tail's AC. It quantifies the tail's aerodynamic effectiveness and is used to calculate NP. Typical values range from 0.35 (smaller or closer to the wing, thus less effective) to 0.6 (larger or farther from the wing, thus more effective).