Dual rotor, rotary wing aircraft
A main rotor blade assembly for a rotary wing aircraft is provided including a main rotor blade root region, a main rotor blade inboard region arranged outboard of said main rotor blade root region, a main rotor blade main region arranged outboard of said main rotor blade inboard region, and a main rotor blade tip region arranged outboard of said main rotor blade main region. At least one of chord, twist, sweep, airfoil shape, and thickness/chord of the main rotor blade assembly has been optimized to achieve balanced high speed forward flight and hover relative to both efficiency and high thrust capability.
1. A coaxial counter-rotating main rotor blade assembly for a rotary wing aircraft having an upper rotor assembly and a lower rotor assembly rotatable about a common rotor axis, each of the upper rotor assembly and the lower rotor assembly including a plurality of rotor blades, each of the plurality of rotor blades, comprising:
a main rotor blade root region;
a main rotor blade inboard region arranged outboard of said main rotor blade root region;
a main rotor blade main region arranged outboard of said main rotor blade inboard region; and
a main rotor blade tip region arranged outboard of said main rotor blade main region, wherein a blade chord to blade radius ratio within the root region increases adjacent the inboard region from about 0.04 to about 0.08, a blade chord to blade radius ratio of the inboard region includes a substantially constant blade chord to blade radius ratio of about 0.08, a blade chord to blade radius ratio of the main region decreases from about 0.08 to about 0.05, and a blade chord to blade radius ratio in the tip region decreases from about 0.05 to about 0.03 in order to achieve balanced high speed forward flight and hover relative to both efficiency and high thrust capability and such optimization is for use both in the upper rotor assembly and in the lower rotor assembly.
2. The coaxial counter-rotating main rotor blade assembly according to claim 1 , wherein the main rotor blade root region extends from about 0% R to 20% R, the main rotor blade inboard region extends from about 20% R to 40% R, the main rotor blade main region extends from about 40% R to 90% R, and the main rotor blade tip region extends from about 90% R to 100% R.
3. The coaxial counter-rotating main rotor blade assembly according to claim 2 , wherein the main rotor blade tip region has a large negative twist angle extending between about −1° and −8°.
4. The coaxial counter-rotating main rotor blade assembly according to claim 2 , wherein the main rotor blade main region has a twist angle extending between about 3° and about −1°.
5. The coaxial counter-rotating main rotor blade assembly according to claim 2 , wherein the twist angle of a portion of the main rotor blade main region varies at a constant rate.
6. The coaxial counter-rotating main rotor blade assembly according to claim 2 , wherein the main rotor blade inboard region has a twist angle extending between about −6° and about 3°.
7. The coaxial counter-rotating main rotor blade assembly according to claim 2 , wherein the twist angle of the main rotor blade inboard region varies at a constant rate.
8. The coaxial counter-rotating main rotor blade assembly according to claim 2 , wherein the main rotor blade root region has a constant twist angle.
9. The coaxial counter-rotating main rotor blade assembly according to claim 2 , wherein the main rotor blade root region has a twist angle of about −6°.
10. The coaxial counter-rotating main rotor blade assembly according to claim 2 , wherein the main rotor blade tip region has an aft tip sweep of about 25°.
11. The coaxial counter-rotating main rotor blade assembly according to claim 2 , wherein a thickness to chord ratio of the rotor blade gradually decreases between the inboard region and the tip region from about .035 to about .01.
12. The coaxial counter-rotating main rotor blade assembly according to claim 1 , wherein at least one of sweep, chord, twist, and thickness to chord ratio of the rotor blade is defined in any of the following tables:
TABLE 1
Program
S-97
Configuration No./Designation
Raider ™
Date
Jan. 15, 2013
Hover Vtip (ft/s)
675
Lateral Lift Offset Limit
−0.28
Advancing Tip Mach Number Limit
0.90
Root cutout (r/R)
0.126
Pre-cone: Upper Rotor (+up)
3
Pre-cone: Lower Rotor (+up)
2
Total Rotor separation distance (d)
0.1347
Number of blades per rotor
4
Radius (ft)
17
Thrust-weighted solidity (per rotor)
0.07072
Thrust-weighted solidity (total)
0.14143
Thickness
r/R
AF
t/c (%)
0
CYL
1
0.1262
CYL
1
0.2
SCE433
0.33
0.32
SCE426
0.26
0.446
SC325222
0.22
0.57
SC36212
0.12
0.7
SC36210
0.1
0.8
SC36210
0.1
0.85
SC36210
0.1
0.9
SC36210
0.1
0.95
SC36210
0.1
1
SC36210
0.1
Chord
r/R
chord (m)
chord (in)
0
0.2286
9.00
0.126
0.2286
9.00
0.15
0.26406
10.40
0.19
0.37196
14.64
0.2
0.37854
14.90
0.21
0.37854
14.90
0.25
0.37854
14.90
0.3
0.37854
14.90
0.32
0.37854
14.90
0.35
0.37854
14.90
0.39
0.37854
14.90
0.4
0.37854
14.90
0.41
0.37854
14.90
0.446
0.37854
14.90
0.45
0.3785
14.90
0.46
0.3776
14.87
0.47
0.3761
14.81
0.5
0.3690
14.53
0.55
0.3548
13.97
0.57
0.3496
13.76
0.6
0.3426
13.49
0.65
0.3309
13.03
0.7
0.3192
12.57
0.75
0.3075
12.11
0.8
0.2958
11.64
0.85
0.2841
11.18
0.89
0.2747
10.81
0.9
0.2693
10.60
0.91
0.2580
10.16
0.95
0.2009
7.91
0.995
0.1366
5.38
1
0.12941
5.09
Sweep
r/R
deg
0
0
0.5
0
0.9
0
0.9
−25
1
−25
Twist
r/R
theta
0
−6
0.126
−6
0.15
−6
0.19
−6
0.2
−5.89
0.21
−5.57
0.25
−3.85
0.3
−1.69
0.32
−0.83
0.35
0.46
0.39
2.18
0.4
2.5
0.41
2.61
0.446
2.61
0.45
2.61
0.46
2.59
0.47
2.52
0.5
2.25
0.55
1.8
0.57
1.62
0.6
1.35
0.65
0.9
0.7
0.45
0.75
0
0.8
−0.45
0.85
−0.9
0.89
−1.26
0.9
−1.49
0.91
−2.02
0.95
−4.67
0.995
−7.67
1
−8.